Faculty of Basic Medical Sciences

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    Open Access
    Studies on the Effect of Traditional Culinary Methods on the Digestibility of Local Cowpea (Vigna unguiculata) Protein.
    (University of Lagos, 1980-09) Oyefeso, Jacob. Adetola.
    A comprehensive review of the origin of cowpea, (Vigna unguiculata) its place in the diet of the people of West Africa and in particular Nigeria, its nutritive value and the inherent anti-nutritional factors, together with the biological mechanisms affecting protein digestion is given.
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    Open Access
    Studies on Local Strains of Campylobacter Jejuni in Lagos, Nigeria.
    (University of Lagos, 1985) Coker, Akitoye . Olusegun.
    One thousand two hundred stool specimens were collected from patients who presented with diarrhoea at Gbaja Health Centre, Surulere, children emergency department and clinical laboratory of the Department of Microbiology and Parasitology of the Lagos University Teaching Hospital, between 1980 and 1983. Faecal specimens were plated on a Butzler’s type medium which consists of Brucella agar base (Oxide CM 169) with 10% sheep blood and bacitracin 25iu/ ml, novobiocin 5pg/ml, cycloheximide 50pg/ml, colistin 10 units/ml and cefazolin 15pg/ml. The first batch of 436 stool specimens were cultured for comparison on both skirrow’s medium and Butzler’s type medium. Plates were incubated at 420C in various systems: candle jar, gas generating kits, with and without active catalyst with a view to arriving at a most suitable procedure for the isolation of Campylobacter jejuni in our environment. The candle jar method which is easy, cheap and simple was found most suitable and then used throughout the project. Sixty-two (5.2%) specimens out of 1,200 were positive for Camylobacter jejuni. In positive specimens, characteristic effuse colonies of the organism were formed. These colonies were gram stained and showed small spiral Gram-negative rods. All the 62 strains were oxidase and catalase positive. Nitrate was not reduced to Nirate and failed to oxidize ferment glucose. On the basis of temperature requirements, all strains grew at 370C and 430C but not at 250C. All strains tested reduced selenite by the production of bright-orange coloured selenium. Strains grew well on nalidixic agar (Oxide) containing 40pg/m1. All the strains showed a wide range of tolerance to 2, 3, 5 – triphenyltetrazolium chloride. (TTC). All strains grew on the 1.5% sodium chloride (Nacl) agar but failed to grow on the 3.5% Nacl agar. All strains gave positive results with 1% glycine. Growth occurred mostly near the surface of the liquid medium to give a cloudy appearance. Strains produced slight growth on the cysteine medium (oxide) and hydrogen sulphide in lead acetate paper. There was no growth on 8% glucose, 1:100,000 and 1:33.000 brilliant green agar. All the strains (60) were sensitive to gentamicin and streptomycin. Both antibiotics inhibited all the strains at 4pg/ml. Chloramphenicol inhibited 54 (90%) of the strains at a concentration of 0.25pg/ml. Tetracycline inhibited all the strains at 2pg/ml with the exception of 3 (5%) strains at 64pg/ml. While erythromycin inhibited all the strains at 4pg/ml with the exception of six (10%). Three of the resistant strains had MIC 16PG/ML while the other three had >128pg/ml.
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    Open Access
    Biological and Serological Studies on Toxoplasma Gondii in Lagos, Nigeria.
    (University of Lagos, 1987-03) Mensah, E.B
    Sera from 775 persons in 10 age-groups, living in Lagos metropolis, were titrated for Toxoplasma antibodies, using the haemagglutination test. The overall percentage positive was 63.2%. The highest (78.4%) was found amongst the age group ranging from 36-40 years, whilst the lowest (48.2%) was recorded in the age group 11-15 years. The risk of nonimmune persons acquiring infection was calculated in the different age group using Van Der Veen's equation. Venous blood samples, cord blood, as well as placental tissue were also collected from a total of 452 pregnant women who attended some antenatal clinics in Lagos. Of the 452 samples studied 60.18% were positive for Toxoplasma antibodies. 70.7% the cord blood specimen collected were also positive. Transmission pattern of toxoplasmosis employing cats was studied, as faecal samples of cats collected randomly from different areas of Lagos were analysed, using the Formol-Ether Concentration technique after Ritchie (1948) to detect the presence of oocysts. The cats were also bled for serological tests. Those found to be negative were fed acutely-ill mouse, and the course of development of the parasite was observed.The effect of Toxoplasma infection on pregnancy was observed using mice models, and it was found that when pregnant mice were experimentally infected, intraperitoneally within the different thirds of their gestation period, death occurred, beginning from the 11th to the 29th day, and not earlier. Toxoplasma gondii trophozoites were maintained in vitro in different fluid media, with pH values ranging from 6.3 to 7.3. The length in days before the death of the infected mice was recorded and it was related to the viability and number of surviving organisms in the suspension. A graph in survival time against preservation time (both in days) was then drawn. The maximum length of survival at 40C was in whole human blood, as well as in foetal Bovine Serum, for up to 56 days. The molecular weight of the proteins present in the RH strain of Toxoplasma gondii laboratory prepared antigen (after Voller et at., 1976) was determined by gel filtration onSephadex G200 chromatography column. The absorbance of the 3 fractions derived were read at 280 nanometers, and the molecular weights were determined by extrapolation from a standard curve of ve/vo against the molecular weights of 4 standard proteins. The molecular weights ranged from 12,445 to 186,209 daltons.
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    Open Access
    Studies on the in Vitro Cultivation of Trypanosomos and Effects of Some Drugs Showing Trypanocidal Activities.
    (University of Lagos, 1987-11) Otigbuo, N.I
    A modified medium for the in vitro cultivations of trypanosomes has been developed. The medium ME-99 comprised of Eagle Minimum Essential Medium (MEM) base and various components of medium 199, not found in MEM. The growth, survival and infectivity of T. b. brucei, T. b. gambiense and T. vivax were compared in the modified medium (ME-99), RPMI 1640, MEM, BCM and 199. The effects of the various sera and the Nu-serum on the culture system Baby Hamster kidney cells (BHK) in MEM, on the growth of T. b. brucei were compared. Parasites grew up to 2 x 1010 in medium utilizing Nu-serum, they were infective to mammalian hosts and they could be subcultured. Nu-serum was found to be suitable replacement for the traditional animal sera used in culture. After the exposure of a monomorphic slender T. b. brucei to the Nu-serum culture, they were observed to have reverted to pleiomorphic forms. It was observed that Nu-serum was responsible for this phenomenon. An attempt at culturing trypanosomes axenically was made. This new system grew the parasites but not as well as the cell systems. Blood stream forms of T. b. brucei were grown over BHK cells in MEM with various concentrations of antiprotozol drugs, (metronidazole, chloroquine and mefloquine) to study the effects of the drugs on the parasites. Drugs inhibited the multiplication of the parasites in vitro. The least effective in vitro concentration for methronidazole and chloroquine were 0.003 mg/ml and 0.0024 mg/ml respectively and for mefloquine 0.002 mg/ml. Groups of female mice were treated once to four times daily with metronidazole and chloroquine individually 24, 48 and 72 hours after T. b. brucei infection. The drugs (chloroquine 0.08mg/kgb w, metronidazole 0.1mg/kgw, 0.03mg/kgbw reduced the number of parasites in the mice but did not effect a cure; they prolonged the survival period of the animals. When mefloquine was administered daily at 0.03 mg/kg body weight for 4 consecutive days, a permanent cure was recorded. The combination of metronidazole (0.1 mg/kgbw) and chloroquine (0.08 mg/kgbw) given daily for four consecutive days, also cleared the parasites from the blood stream.Mice inoculated with culture medium containing a combination of both chloroquine and metronidazole at 0.0024 mg/ml and 0.003 mg/ml respectively confer protection against infection by trypanosomes for 14 days. Mefloquine alone at 0.002 mg/ml conferred protection against subsequent infection for more than 4 months. Mice inoculated with washed trypanosomes from cultures containing a combination of metronidazole and chloroquine, were protected against infection for 3 weeks. Mice initially inoculated with pre-treated and washed trypanosomes from drug combined culture medium, and later given a combination of both drugs intraperitoneally, were protected against infection for a period of 5 weeks.Mice injected with 0.03 mg/g mefloquine for 3 days consecutively were protected against T. b. brucei infection for 90 days and over.
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    Open Access
    Studies on the Effects of Ultraviolet Radiation on Schistosoma Mansoni
    (University of Lagos, 1988) Ariyo, A.A
    The effect of ultraviolet radiation on the pre-adult stages of Schistosoma mansoni under various conditions was studied. No morphological changes occurred in irradiated eggs. However, the hatchability of the eggs decreased proportionately with the radiation dose. The mean rates of motility of miracidia hatched from irradiated eggs and that of irradiated miracidia were found to be radiation dose dependent and also decreased as the miracidia and miraciadia hatched from irradiated eggs were shortened, only 19% and 5% of those exposed to ultraviolet for 30 minutes survived for 3 hours as compared with 80% survival rate in control experiments. When miracidia were directly exposed to radiation, ineffectivity rate decesed with rising radiation dose while no significant difference was observed in ineffectivity of miracidia from irradiated eggs. The batches of S. mansoni cercariae exposed to various radiation dose and the control batch remained actively motile 30 minutes post-irradiation. Thereafter cercarial activity decreased with increasing radiation dose and cercarial age. There was no significant difference between the attachment rate of the batches of cercariae. The recovery rates (0.00-49.00%) of worms were significantly different from he rate of attachment of cercariae to the mice (93.50 - 100.00%). Maturation and penetration rates were dependent on radiation dose. Eggs deposited in the liver of mice and hatchability rate of the eggs varied significantly with the radiation dose. When radiation of cercariae at different levels in water and the reproductive potentials of the adult worms were studied, at a depth of 10.0cm the number of worms recovered was 25, while at 72.5cm the corresponding number of worms recovered increased to 52. Similarly, the pairing of worms, egg-load per gram of liver and hatchability of eggs increased as compared with control. When mice were infected with mixed radiated, and non-irradiated cercariae, the rate of intestinal adult worm recovery decreased form 52 to 0 as the proportion of irradiated cercariae increased. No effect on pairing was evident even when all cercateriae were radiated. Irridiation of cercariae did not influence the haemoglobin and packed cell volume of the host and their offsprings. There was an increase in the weight of infected mice which was more significant the more intense the radiation. Reproduction in female mice with irradiated cercarial infection were negligibly affected by the presence of irradiated schistosomes and could be ignored.
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    Open Access
    Plasmodium Yoelii Nigeriensis Infection and Immune Response in Mice and Rats
    (University of Lagos, 1988) Fagbenro-Beyioku, F.A
    The Biology of Plasmodium yoelli nigeriensis in rodents and the reaction of rats and mice to the infection were studied. In investigations into the course of infection of Plasmodium yoelli nigeriensis in rats and mice, it was found that adult mice and baby rats were susceptible to the infection, while adult rats were totally resistant. The infection was rapidly fatal in both adult and baby mice while in baby rats; it was tolerated until the animals were 7 weeks old, after which they are able to eradicate the infection. Investigations conducted into the possible causes of this non-susceptibility of adult rats revealed that both the serum and thoracic duct cells of these animals conveyed some immunity. The serum conveyed noticeable immunity to rodents of another species, i.e mice, while the thoracic duct cells conveyed total immunity to baby rats. Some mice which exhibited a phenomenon termed "spontaneous recovery" or "self cure", that is natural recovery without the use of any drugs, exhibited an immunity which lasted for the duration of the life time of the animals. This immunity was found to be non-transferrable to the offspring as babies born to such parents exhibited the normal course of infection as other baby mice. In investigations correlating the quantity of food to the course of infection of Plasmodium yoelli nigeriensis in adult mice, it was found that animals which had adequate food were in better condition to withstand infections with Plasmodium yoelli nigeriensis. The less food the animal had, the longer the pre-patent period of the parasite, but the earlier animal host died of its effects. The effect of a chronic disease e.g. Schistosomiasis, on the course of infection of Plasmodium yoelli nigeriensis was also investigated. Interestingly enough, mild infections with Schistosoma mansoni (100 cercariae per animal) was found to be beneficial to the rodent host in attenuating infections with Plasmodium yoelli nigeriensis within the early days of the Schistosoma infection. More animals infected at this time recovered from the malaria infections. Even heavier infections at this time exhibited a beneficial effect in that the animals died much later than control animals which had no Schistosoma. In challenges made to animals which had worms that would have reached sexual maturity, the course of Plasmodium yoelli nigeriensis was comparable to that of normal mice.
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    Open Access
    Prevalence and Gingivalis Pathogenicity of Bacteroides Gingivalts Isolated from Nigerians
    (University of Lagos, 1988-08-27) Eke, I.P
    Plaque samples obtained from 62% and 20% of 50 Nigerians with clinically 'normal' oral cavities were colonized by Bacteroides melaninogenicus and B. intermedius respectively. B. gingivalis was not isolated from these subjects. Pathologic materials obtained from infected sites in 45.6%, 53.3% and 34.9% of 103 patients presenting with a variety of prodental diseases were colonized by B. melanino-genicus, B. intermedius and B. gingivalis respectively. The apparently higher prevalence of B. gingivalis was isolated more frequently with increasing age of patient and most frequently from periodontitis (37.1%). Acute necrotizing ulcerative gingivitis - ANUG (70%), and dento-alveolar abscesses (32%). Clinical isolates of B. gingivalis from Nigerians exhibited several phenotypic similarities with isolates from Americans. Clinically important differences existed however in sensitivity to ampicillin, tetracycline and the production of Beta-lactamase. A reliable simple and rapid scheme for the identification of human black pigmented Bacteroides was developed and evaluated. This scheme utilized microtitration techniques and the hydrolysis of specific chromogenic enzyme substrate for presumptive identification within 4hs. Co-aggregation studies undertaken showed that B. gingivalis exhibited specific affinity to bind in-vitro with members of the Veilonella spp, Capnocytophaga spp and Actinomyces naeslundii but not with any of the oral streptococci. Co-aggregation exhibited by B. gingivalis was lactose reversible. Also, B. gingivalis demonstrated a strong hemagglutinating activity which was enhanced by saliva but weakened when cells are/primed with ethylenediamenetetra acetic acid (EDTA). Salivary enzymes did not interfere with aggregation of human black pigmented Bacteroides species. Cultural filtrates and crude cell extracts of B. gingivalis were cytotoxic to Vero cells and Wi 38 cells in vitro and this activity was related partly to butyrate and propionate metabolic end products. Also a previously unreported heat labile cytotoxin in young cultures of B. gingivalis was reported and related to the activity of a trypsin-like protease by B. gingivalis. An experimental animal model was developed for demonstrating the pathogenicity of mono model B. gingivalis. By utilizing this model B. gingivalis was demonstrated to induced a loculated subcutaneous abscess in hamsters and a spreading subcutaneous infection in mice. Its pathogenicity was not enhanced by reducing agents but was greatly enhanced by haemin. B. gingivalis also produced pneumonitis and lung abscesses in hamsters infected transtracheally, and abscesses in experimentally infected liver, testes and muscles. These studies suggest that B. gingivalis may be involved directly in the pathogenesis of soft tissue abscesses of the oral cavity and respiratory tract.
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    Open Access
    Experimental Infections of Biomphalaria Glabrata, B. Pfeifferi and B. Sudanica with Schistosoma Mansoni
    (University of Lagos, 1989) Wey, I.O
    A laboratory study was carried out to determine quantitatively the degree of compatibility between biomohalaria glabrata, B. pfeifferi and B. sudanica and Schistosoma mansoni. The effect of host diet and mode of exposure to miracidia, continuous darkness, origin of host species and parasite strains, miracidial dosage level, age and intensity of primary infection in dual infections were examined by measuring snail survival, growth, fecundity, prepatent period, infection rate and cercarial production. The results of experiments on host diet and exposure technique showed that individual exposure of B. glabrata snails to mircidia resulted in injection rates varying from 31% - 85% compared with a range of 6% - 22% obtained in mass exposed snails. Lettuce plus Tetramin and lettuce plus rabbit pellets were found to be superior diets to lettuce alone. Light-deprivation did not significantly reduce the survivorship, growth, fecundity and cercarial production of B. glabrata. The compatibility of large (1479.1mh), medium (493.5mg) and small 101.5mg) B. glabrata with S. mansoni was tested. Medium-sized snails were found to produce the highest average cercarial yield of 628 cercariae per snail per day compared to 377 cercariae produced by small and large snails respectively. This trend was confirmed in a subsequent modified replicate. An investigation of the compatibility between Sudanese B. pfeifferi, Ethiopian B. sudanica and Brazilain B. glabrata to Kenya and Brazilian strains of S. mansoni strain from Kenya. The highest infection rate (60%) and the highest cercarial yield (2792 cercariae per snail) were produced by this host-parasite combination. Exposure of B. glabrata to varying doses of miracidia ranging from 1 to 50 resulted in decreased cercarial production at miracidial densities above fifteen. Four different types of shell deformations were observed in addition to polyembryony and the production of eggmasses which were completely devoid of eggs and embryos.Superimposition of homologous miracidia on pre-existing S. mansoni infections was easily achieved in B. glabrata. However, the effect of superinfection on snail survival, growth, fecundity and cercarial production depended on the sequence of infection and the interval between infections. A challenge infection of five miracidia within an interval of one week, was found to enhance cercarial production and inhibit ovipository activity to a high degree (P < 0.001). On the contrary, snails which received a challenge infection of fifteen miracidia three weeks after a primary dose of five miracidia showed less evidence of ovipository inhibition and had a significantly reduced mean cercarial production (P < 0.05). The significance of the age of the primary infection is discussed.
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    Open Access
    Immunological Studies on Strains of Campylobacter Jejuni Isolated in Lagos, Nigeria.
    (University of Lagos, 1989-06-12) Obi, L.C
    Microbiology is a dynamic discipline, the taxonomy of some species is rapidly changing. Organisms which were not known to previously cause infection of some opportunistic pathogens are now incriminated in disease causation. Until recently, the unequivocal bacterial agents of diarrhoea in our environment and even world wide were Salmonella spp., Shigella spp. and Vibrio cholera. However more recent bacterial agents of diarrhoea or gastroenteritis include Yersinia enterocolitica, Clostridium difficle, Liseria monocytogenes and Campylobacter jejuni. In Nigeria, cases of diarrhoea due to Campylobacter jejuni may exceed the frequency of salmonelle and Shigella combined (Coker and Dosunmu-Ogunbi, 1983). In Nigeria, studies on Campylobacter are still at its infacy. Until date, reports on Campylobacter jejuni have been on pathogenicity assessment, biotype and serogroups distribution, plasmid profiles, Campylobacter as agent of gestroenterities and anti-microbial agents. Presently, detailed immunological studies or reports on Campylobacter jejuni are lacking in Nigeria. For example, production of antisera against the organism has not been attempted. Experimental studies involving diagnostic or protective effects of anti-Campylobacter antibody in line with recent developments in Imunology are not available. The levels of antibodies among patients with diarrhoes due to Campylobacter jejuni and asymptomatic individuals including the bactericidal power of normal human serum against the organism have also not been determined. A simple presumptive test for the organism in our environment is still non-existent. In light of all these, should we remain complacent and continue to depend on reports from developed countries? As microbiologists are we not aware that strains of particular organism vary from country to country? Is it then very appropriate to continue to import antisera for the diagnosis of our local strains of Campylobacter jejuni? As indigenous scientists, do we have any justification in believing that for example, immunological studies on a particular organism carried out abroad must bear relevance to our local organism? This thesis is an attempt to document immunological studies on our local strains of Campylobacter jejuni.
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    Open Access
    Factors Associated with Pathogenicity and Antibiotic Resistance of Local Strains of Lancefield Groups A, C and G Streptococci
    (University of Lagos, 1989-11-07) Lawal, F.S
    Four thousand, three hundred and ninety five throat, 4,395 nasal and 58 skin lesion swabspecimens were examined bacteriologically out of which 401 (9.12%) were positive for betahaemolytic streptococci (BHS) and 11 (0.25%) for non-haemolytic streptococci (NHS). On the basis of Lancefield group polysaccharide antigens, the isolates were classified into groups A, C, D, G and non-groupable BHS strains. On the basis of bacitracin sensitivity and biochemical analysis, these groups and ungroupable HBS strains were classified into Strept pyogenes Strept. equisimilis, Strept. canis and Strept. milleri. Six members of group A, 68 of group C and 117 of group G BHS isolates were O (SLO), deoxyribonuclease B (DNase B), hyaluronidase, M-associated protein (MAP), serum opacity factor (SOF), proteinase, M,T and R protein antigens. These antigenic components were observed in varying percentages of the isolates: all (100.0%) the six members of group A were positive for SLO and MAP, five (83.3%) for DNase B and hyaluronidase, three (50.0%) for SOF and four (66.6%) for proteinase activity; 41 (60.29%) of group C for SLO and MAP, 52 (76.47%) for DNase B, 56 (82.35%) for hyaluronidase, and nil (0.0%) for both SOF and proteinase while 68 (58.11%) of group G produced SLO, 94 (80.34%) DNase B 56 (47.86%) hyaluronidase, 104 (88.88%) MAP and nil (0.0%) for SOF and proteinase. The ultimately established group C serotype CI and group G serotypes GI - VIII examined for both indigenous and group A - cross - reacting T4 or T25 - antigen showed evidence of these antigens as follows: both serotypes CI and GI showed their indigenous T-antigen and group A cross-reacting T25 and T4 respectively, while serotypes GII - VIII showed indigenous Tantigens only. Varying proportions of those BHS strains (8: 68 for group C and 68: 117 for group G) that produced high ( > 1:80) titres of MAP were studied further. Six members of group C and 19 of group G were ultimately selected as vaccine strains for antisera production in rabbit. Five of the six members of group C and 17 out of 19 of group G successfully produced corresponding type antibodies. Distinct type antisera, one for group C and eight for group Gcorresponding respectively to group C (serotype CI) and group G (serotypes GI - VIII) eventually emerged after absorption with appropriate group C or group G heterologous strains. Other type antisera and their corresponding typeable vaccine strains turned out to be homologous to other group C or group G types. These group C and group G antisera were initially used in parallel with group A type 12 (G 12) and group G strain 51/755 antisera (controls) to screen Lancefield's extracts of 86 group C isolates and 152 group G isolates respectively for evidence of M or R like type antigen. Twelve (13.65%) of the 86 group C and 75 (50.33) of 149 group G isolates could be M-serotyped while none (0.0) showed evidence of R-like antigen/antibody activity. The remaining 76 (86.36%) group C and 74 (49.66%) group G isolates could not be serotyped with the available antisera. Twenty (Co5T'S'). The three patterns occurred in varying percentages of 63.48 (353/556), 33.27 (185/556) and 3.25 (18/556) respectively. Representative strains of the three antibiotic susceptibility patterns, Co5 S' T', Co5 S' T5, and Co' S' T' were observed further to show varying (80 - 0.62 ug/ml) rages of minimum inhibitory concentrations (MIC) of chloramphenicol co-trimoxazole, erythromycin, penicillin G, streptomycin and tetracycline for the three antibiotic - susceptibility patterns, which in the case of chloraphenicol, co-trimoxazole, erythromycin and penicillin G correlated with in vitro susceptibility and in the case of streptomycin and tetracycline correlated with in vitro resistance of the BHS isolates tested against the six antibiotics. The three representative patterns were further screened for evidence of antibiotic - resistance factors, plasmid deoxyribonucleic acid and beta-lactamase for which none of the isolates was positive.
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    Open Access
    Prevalence and Characteristic of Aeromonas Species and Plesiomonas Shigelloides in Lagos.
    (University of Lagos, 1989-12) Alabi, S.A
    This study was carried out in two phases. The first phase involved the determination of the prevalence of Aeromonas species. and Plesiomonas Shigelloides in patients, with and without diarrhoea, reporting at the enteric laboratory of the Department of Medical Microbiology and Parasitology, Lagos University Teaching Hospital (LUTH), Idi-Arba, Lagos: over a 12-month period of October 1986 through September 1987. In the second phase the characteristics of isolates thus obtained were examined. During the first phase of the study, a total of 2,350 faecal specimens from patients with diarrhoea were screened for the presence of Aeromonas sp. or P. Shigelloides. Of this number, 53 (2.26%) yielded P. Shigelloides sp. On the other hand, of a total of 500 faecal specimens from patients without diarrhoea (controls) collected over the same period of time, only 2 (0.4%) were positive for Aeromonas sp. while none of the specimens yield P. shigelloides. In which case, both organisms were more frequently isolated from diarrhoea than that from control specimens. As a matter of fact, the difference in the isolation rates of Aeromonas sp. from patients with diarrhoea and controls was statistically significant (p<0.01). It is equally noteworthy that isolation rates of 2.26% Aeromonas sp. and 0.68% P. shigelloides compared favourably with those obtained for other established enteric pathogens in this study, such as the entero-pathogenic Escherichia coli (EPEC, 2.85%), shigella sp. (0.17%), Salmonella sp. (0.13%) and Y. enterocolitica (0.09%). Also, none of these enteropathogens were recovered in faecal specimens positive for Aeromonas sp. or P. shigelloides. Further biochemical characterisation of the Aeromonas and Plesiomonas isolates revealed that of the 55 Aeromonas sp. 20 (36.4%) were A. Hydrophila, 28 (50.9%) were A. caviae and 7 (12.7%) were A. Sobria. It was also observed that of the numerous tests used in the characterisation, eleven simple ones, viz: the production of oxidase, catalase, hydrogen sulphide (H2S) from Kligler's iron agar (KTA), pigmentation on nutrient agar, acid from glucose, xylose, dulcitol, adonitol, mannitol, inositol, and inability to grow in 6.5% NaC1; were highly reproducible. Based on these findings, a simple scheme was designed for the isolation and preliminary identification of Aeromonas sp. and P. shigelloides from faecal specimens. Similarly, survival of Aeromonas sp. and P. shigelloides was measured in commonly used transport media such as Cary-Blair, Stuart, Amies, phosphate bufferred saline, and alkaline peptone water (APW). Results obtained indicate that these organisms would survive in these media for at least one month. However, a modified form of APW containing 0.01% w/v FeSo4 appeared to be the most suitable for the long storage of these organisms. In the same vein, a good number of Aeromonas sp. and P. shigelloides examined in this study produced haemolysins, heat-stable (ST) enterotoxin, or invasiveness: which are recognised virulence factors in the pathophysiology of acute diarrhoea. Specifically, about 70% of the Aeromonas sp. produced & or B-haemolysin, 20% produced ST and about 11% were invasive. Similarly, 25% of P. shigelloides produced ST and invasiveness while about 13% produced & - haemolysin. It is significant to note that all the isolates that produced virulence factors were isolated from patients with diarrhoea; thus indicating that these factors may have a role to play in diarrhoea associated with these organisms. However, when strains producing virulence factors were fed orally to healthy adult mice, they failed to cause diarrhoea. It is noteworthy that these strains survived the gastric acid barrier in the stomach, and were infact reisolated from faecal specimens of the animals. The possibilities are therefore that either these virulence factors were not elaborated in vivo, or that a number of host factors made mice unsuitable for experimental infection with Aeromonas or Plesiomonas. The in vitro susceptibility pattern of Aeromonas sp. and P. shigelloides isolated in this study was determined against 15 selected antimicrobial agents. The results obtained have shown that these organisms are susceptible to most of the agents evaluated. Specifically, all the strains were susceptible to ofloxacin and at least 60 (>70%) strains were susceptible to gentamicin, carbenicillin, ceftriaxone, colistin, nalidixic acid, nitrofurantoin, chloramphenicol, tetracycline and co-trimoxazole. Also, less than 30% of the strains were susceptible to ampicillim. Finally, Aeromonas sp. and P. shigelloides isolated during the course of this work were screened for the presence of plasmids. Interestingly enough, some of the isolates harboured plasmids with molecular weights ranging between 2.4 x 106 to 16.8 x 106 daltons. Of the 55 Aeromonas sp. examined, 12 (21.8%) harboured one or more plasmids. Similarly, a strain of P. shigelloides possessed more than one plasmid. Hence, the various findings reported in this study seem to suggest that Aeromonas sp. and P. shigelloides may have a significant role to play in acute diarrhoeal diseases in the Lagos environment. However, there is need for similar studies on a national scale to increase the present level of awareness; and for a better understanding of Aeromonas and Plesiomonas associated diarrhoea in Nigeria.
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    Open Access
    An Investigation of Some Factors Influencing the Pathogenicity of Neisseria Meningitidis
    (University of Lagos, 1990) Taiwo, O.B
    The nasopharyngael carriage rate of Neisseria meningitidis among 639 school children in Ijede, Ikorodu, Lagos State was 6.2% (40/639). The proportion of male carriers 62.5% (25/40) was significantly higher than females (37.5%; 15/40 (P < 0.05). N. meaningitidis groups C and A were the most frequently isolated serogroups accounting for 40% (16/40) and 22.5% (9/40) of the isolates respectively. In-vitro assessment of the attachment of N. meaningitidis to human nasopharyngeal epithelial cells (NEC) dropped that meningococci of all serogroups attached in significantly higher numbers to NEC of infants (160/HDC) and children (164/NEC) than NEC from neonates, (115/NEC) adults (124/NEC) and elderly (109/NEC). Attachment of meningococci to NEC of males and females was not significantly different. N. meningitidis group C clinical strain attached significantly better to non-carrier NEC than to the NEC of group C meningococcal carrier. The cell free supernates of some strains of Escherichia coli, Staphylococcus aureus and vridans streptococci isolated from the upper respiratory tracts of meningococcal carriers and non-carriers were found to produce substances inhibitory to serogroups of menigococci in vitro. Purified meningococcal endotoxin, and heat-killed meningococcal inocula from both clinical and carrier isolates were lethal for 12 day old chick embryo on chorioallantotic vein and yolk sac inoculation. Experimental laboratory animals including day old chicks suckling mice and infant rats did not develop meningitis subsequent to inoculation with meningococci through various routes. The collective results of these studies suggest that N. meningitidis possesses numerous pathogenicity factors which may act in synchrony depending on various host factors to enable this organism to overcome host defence and cause life threatening infections.
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    Open Access
    Studies on the Effect of Prostaglandin Inhibition by Aspirin and Indomethacin on Ovulation and Pregnancy in the Rat
    (University of Lagos, 1990-01) Olufeyisipe, A.A
    The present study was conducted with the aim of determining the effect of prostaglandin inhibition on certain aspects of the reproductive system, namely ovulation and pregnancy in young adult female Sprague Dawley rats. Prostaglandin inhibition was achieved by the administration of two widely used prostaglandin inhibitors, Aspirin and indomethacin. In order to determine the probable mechanism as well as the site of action of the prostaglandin inhibitors, the effects of human chorionic gonadotropin (HCG) and luteinizing hormone (LH) on the action of the drugs were investigated. Morphometric studies on the ovaries were also carried out. The experiments involved the testing of the effects of Aspirin and indomethacin on (i) Spontaneous ovulation (ii) Superovulation, (iii) ovulation in the presence of exogenous HCG (iv) ovulation in the presence of exogenous LH, and (v) pregnancy. The parameters measured were the preovulatory plasma LH level, the preovulatory plasma PGF level, the rate of ovulation, the pattern of follicular development in the ovary, the rate of embryo implantation, the length of gestation, and the number of offsprings delivered at the end of gestation. The result of the present study indicates that Aspirin and indomethacin when given in doses that inhibit inflammatory reactions will inhibit the process of ovulation, including follicular development and ovum maturation. In this action indomethacin was a stronger inhibitor of ovulation than aspirin. Morphometric studies reveal that while indomethacin is effective in suppressing follicular rupture, aspirin mainly retards ovum maturation. The two drugs also caused a significant reduction in plasma PGF level with indomethacin again being the more effective of the two. It therefore appears that aspirin and indomethacin may inhibit ovulation by inhibiting. Prostaglandin synthesis, implying that prostaglandins are involved in the process of ovulation. Since both aspirin and indomethacin are anti-inflammatory agents, the mechanism of prostaglandin action on ovulation may likely be an inflammatory one. It was also observed that HCG and LH did not reverse the inhibition of ovulation by aspirin and indomethacin. It is also noteworthy that the administration of aspirin indomethacin did not affect the prevalatory LH level. This indicates that aspirin and indomethacin exert their ovulation inhibitory action directly on the ovary and not on the hypothalamic axis. The results also revealed that while aspirin administration during pregnancy caused no adverse effects, indomethacin reduced the rate of implanation, prolonged the gestation period and caused the resorption of some of the fetuses. It is concluded that prostaglandins play a crucial role in the mechanisms involved in the processes of ovulation and pregnancy.
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    Genetic manipulation of Bacillus species for improved fermentation of Citrullus Vulgaris and cloning of its Amylase gene in Escherichia Coli
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1991) Adeniran, S.A
    Two strains of Bacillus Licheniformis and one each of Bacillus pumulus and Bacillus subtillis were isolated from Iru fermented African Locust Beans (Parkia biglobosa). Characteristics of these microbes show that they are resistant to at least two antibiotics each with B.subtilis being resistant to a total of eleven antibiotics.
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    Histoquantative studies on the alteration in testicular morhology induced by chronic administration of chloroquine
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1991-02) Okanlawon, A.O.
    Chloroquine has been reported to affect male reproductive capacity. As these reports have been very elusive in both qualitative and quantitative determination of reproductive toxicities, experiments were undertaken to develop a model which could be used to study these effects and efforts made to design a battery of tests for efficient evaluation of the effect of reproductive toxins on testicular morphology.
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    Studies on Bacteroides Bivius: its occurence in gynaecological infections and pathogenicity
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1992) Egwari, L.O
    A total of 335 and 307 bacterial isolates were isolated from cervical swab (CS) and high vaginal swab (HVS) specimen of 80 Nigerian women with gynecological infections respectively.
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    Studies on Bacteroides Bivius: its occurence in gynaecological infections and pathogenicity
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1992) Egwari, L.O
    A total of 335 and 307 bacterial isolates were isolated from cervical swab (CS) and high vaginal swab (HVS) specimen of 80 Nigerian women with gynecological infections respectively.
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    An enzyme linked immunosorbent assay (ELISA) for thyriglobulin antibodies
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1992) Adedara, T.A
    An enzyme-linked immunosorbent essay (ELISA) has been developed for the quantitative analysis of thyroglobulin antibodies. The method is based on the detection of antibodies using enzyme-labelled antiglobulin.
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    A study of some mechanisms of experimental salt-induced hypertension in Rats
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1992-01) Obiefuna, P.C
    A relationship between high blood pressure and dietary salt intake has been postulated for over a century. Dietary salt ingestion is now known to positively correlate with arterial blood pressure in man and experimental animals. The underlying mechanisms are however not clear. This study examined vascular smooth muscle activity in a sprague-Dawey rat model of salt-induced hypertension.
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    Effects of Diarrhoea on intestinal brush burder enzymes and protein nutritional status of the Rat
    (School of Postgraduate Studies of the University of Lagos, Akoka, 1993-02-02) Elemo, B.O