Microbiology -Scholarly Publications

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    Open Access
    Heavy metals assessment of ecosystem polluted with wastewaters and taxonomic profiling of multi‑resistant bacteria with potential for petroleum hydrocarbon catabolism in nitrogen‑limiting medium
    (Springer, 2023-01-11) Oyetibo, G.O.; Adebusoye, S.A.; Ilori, M.O.; Amund, O.O.
    The coexistence of heavy metals (HMs) and petroleum hydrocarbons (PHs) exacerbates ecotoxicity and impair the drivers of eco-functionalities that stimulate essential nutrients for the productivity of the impacted environment. Profiling the bacteria that stem the ecological impact via HMs sequestration and PHs catabolism with nitrogen fixation is imperative to bioremediation of the polluted sites. The sediment of site that was consistently contaminated with industrial wastewaters was analysed for ecological toxicants and the bacterial strains that combined HMs resistance with PHs catabolism in a nitrogen-limiting system were isolated from the sediment and characterized. The geochemistry of the samples revealed the co-occurrence of the above-benchmark concentrations of HMs with the derivatives of hydrocarbons. Notwithstanding, nickel and mercury (with 5% each of the total metal concentrations in the polluted site) exhibited probable effect concentrations on the biota and thus hazardous to the ecosystem. Approx. 31% of the bacterial community, comprising unclassified Planococcaceae, unclassified Bradyrhizobiaceae, Rhodococcus, and Bacillus species, resisted 160 µmol Hg2+ in the nitrogen-limiting system within 24 h post-inoculation. The bacterial strains adopt volatilization, and sometimes in combination with adsorption/bioaccumulation strategies to sequester Hg2+ toxicity while utilizing PHs as sources of carbon and energy. Efficient metabolism of petroleum biomarkers (> 87%) and Hg2+ sequestration (≥ 75% of 40 µmol Hg2+) displayed by the selected bacterial strains portend the potential applicability of the bacilli for biotechnological restoration of the polluted site.
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    Open Access
    Growth Limiting pH, Water Activity, and Temperature for Neurotoxigenic Strains of Clostridium butyricum
    (Hindawi Publishing Corporation, 2013-08-25) Ghoddusi, H. B.; Sherburn, R. E.; Aboaba, O. O.
    Some rare strains of Clostridium butyricum carry the gene encoding the botulinal type E neurotoxin and must be considered as possible hazards in certain types of food. The limiting growth conditions for C. butyricum were determined in peptone yeast glucose starch (PYGS) broth incubated anaerobically at 30∘C for up to 42 days. The minimum pH values permitting growth depended on the acidulant and strain. Organic acids were more effective at inhibiting growth than HCl as expected. The lowest pH values at which growth of toxigenic and nontoxigenic strains of C. butyricum was observed in broth acidified with HCl were 4.1 and 4.2, respectively. In organic acids, however, the minimum pH varied between 4.4 and 5.1 depending on acid type and concentration. The minimum water activity for growth of toxigenic strains of C. butyricum was 0.96. The minimum growth temperatures of the toxigenic strains of C. butyricum (ca 10-11∘C) were somewhat higher than for non-toxigenic ones (8∘C). It was concluded that control of toxigenic C. butyricum in the food industry needs to allow for the greater pH tolerance of this species compared with proteolytic C. botulinum.
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    Open Access
    Antibiotic resistant profiles of food (fresh raw milk) and environmental (abattoir effluents) isolates of Listeria monocytogenes from the six zones of Nigeria
    (African Journal of Microbiology Research, 2013-08-06) Enurah, L. U.; Aboaba, O. O.; Nwachukwu, S.C.U.; Nwosuh, C. I.
    The prevalence of Listeria monocytogenes in fresh raw milk and abattoir effluents in the six zones of Nigeria was determined. Antibiotic resistant profile of the isolates was examined using the Bauer- Kirby disc diffusion assay. A total of 626 food and environmental samples were cultured on selective media out of which 54 (8.6%) were positive for L. monocytogenes. Chloramphenicol was the most effective antibiotic against the isolates with the least resistance (3.70%) while nalidixic acid proved to be least effective with resistance of 90.74%. The multiple-antibiotic resistant pattern of the isolates showed nalidixic acid/cloxacillin (35.2%), nalidixic acid/colistin (31.5%) and cloxacillin/colistin/nalidixic acid (29.6%) to be most prominent. The least value was observed in chloramphenicol/nitrofurantin/cotrimoxazole with 5.6%. The modal values of the minimum inhibitory concentrations (MICs) of the antibiotics to the isolates range between 4.0 and >16.0 μg/ml. Chloramphenicol, nitrofurantin and gentamycin recorded the highest MIC compared with other antibiotics. This study has demonstrated that a wide and rapidly expanding range of undesirable and, in some cases, multi-resistant determinants is currently present in L. monocytogenes
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    Open Access
    Prevalence and Antibiotics Susceptibility Profile of Listeria monocytogenes Isolated from Processed and Unprocessed Meat Products in Lagos, Nigeria
    (Science and Technology, 2015-01-01) Ohue, L. A.; Enurah, L. U.; Aboaba, O. O.
    Antibiotics susceptibly pattern of Listeria monocytogenes isolated from processed and an unprocessed meat was investigated. A total of fifty (50) retail meat samples consisting of 20 raw meat, 15 fresh processed meat samples and 15 processed ready- to-eat samples were cultured on Listeria Selective Agar (Oxoid) and Listeria Chromogenic Differential Agar (Oxoid) after pre-enrichment in Buffered Listeria Enrichment Broth. Listeria spp. were isolated from 29 (58%) of the samples, out of which 14 (28%) were Listeria monocytogenes. Listeria monocytogenes was significantly higher in unprocessed meat 9 (45%) than in processed ready-to-eat meat products which were 5 (33%). No isolate was found in fresh processed meat products comprising of smoked bacon, sausages, beef mortadella, minced meat and beef salami. The antibiotic susceptibility of the fourteen Listeria monocytogenes strains was determined by disc diffusion method. High susceptibility was found in Ciprofloxacin (100%), Pefloxacin (100%), Gentamycin (100%), Streptomycin (92.9%), Erythromycin (92.9%), Sulphamethoxazole (71.4%) and Amoxicillin (64.9%). Resistance to Ampiclox was the most common and was encountered in 13 (93%) of the strains. The study shows that Listeria monocytogenes from meat samples is susceptible to the antibiotics commonly used in veterinary and human listeriosis treatment.
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    Open Access
    Isolation and PCR Detection of Cronobacter sakazakii from Powdered Infant Formulae retailed in Nigeria
    (American Journal of Food and Nutrition, 2013-01-01) Ezeh, R. A.; Aboaba, O. O.; Smith, S. I.; Fesobi, W. A.; Omonigbehin, E. A.; Bamidele, M.
    The presence of Cronobacter sakazakii in 154 samples of powdered infant formulae (PIF) retailed in Nigeria was analyzed using real time polymerase chain reaction (PCR) and a chromogenic medium, Druggan-Forsythe-Iversen (DFI) agar. Two pairs of species specific primers (SG-F/SG-R and SI-F/SI-R) targeting the sequences between 16S rDNA and 23S rDNA (internal transcribed spacer, ITS) were used for the amplification. Out of the 154 samples analyzed, C. sakazakii was detected in 3 (1.95%). A particular isolate detected by SI primer was not detected by SG primer. This study shows that Cronobacter sakazakii can be detected using both the chromogenic DFI agar (cultural method) and molecular method. This report is the first for the isolation and molecular detection of Cronobacter sakazakii from powdered infant formulae retailed in Nigeria.