South Asian Journal of Research in Microbiology

Antimicrobial Susceptibility and Biofilm-Forming Ability of Airborne Bacteria Isolated from Selected Livestock Farms and Abattoirs in Port Harcourt, Nigeria

2026-10-01T12:17:04+00:00

Background: Airborne microbial contamination in livestock farms and abattoirs poses significant public health, animal welfare, and food safety risks because of high animal density, inadequate ventilation, and processing activities that generate bioaerosols.

Materials and Methods: This study assessed the distribution, diversity, antibiotic susceptibility, and biofilm-forming potential of airborne microorganisms in six livestock-related environments in Port Harcourt, Nigeria: Piggery Farm, Goat Farm, Cattle Farm, Rumuokoro Abattoir, Eagle Island Abattoir, and Tech Farm Abattoir. Air samples were collected by passive sedimentation using exposed Nutrient Agar, MacConkey Agar, and Sabouraud Dextrose Agar plates placed in areas of high animal activity, waste disposal, and slaughter-processing operations for 10 minutes. The plates were incubated at 37°C for 24–72 hours. Bacterial isolates were identified using colonial morphology, Gram staining, and standard biochemical tests, while fungal isolates were identified based on their macroscopic and microscopic characteristics. Antibiotic susceptibility was determined using the Kirby–Bauer disc diffusion method, and microbial load was expressed as colony-forming units per minute per square metre (CFU/min·m²).

Results: Rumuokoro Abattoir recorded the highest microbial load, with total heterotrophic bacterial count, total coliform count, and total fungal count of 36.38 ± 15.91, 38.60 ± 18.24, and 5.10 ± 0.28 CFU/min·m², respectively. A total of 24 bacterial isolates belonging to nine genera were identified, comprising Staphylococcus spp., Bacillus spp., Lederbergia sp., Micrococcus sp., Serratia spp., Arsenophonus sp., Cronobacter sp., Klebsiella spp., and Citrobacter spp. Staphylococcus spp. showed the highest occurrence (29.2%), followed by Bacillus spp. (20.8%). Five fungal taxa were recovered: Penicillium sp., Mucor sp., Aspergillus niger, Trichophyton sp., and Fusarium sp. Antibiotic susceptibility testing showed that most Bacillus spp. and Staphylococcus spp. were resistant to rifampicin, ceftazidime, azithromycin, and cefuroxime, with only limited susceptibility to gentamicin and levofloxacin. Among the Gram-negative isolates, Serratia spp. and Citrobacter spp. were resistant to all antibiotics tested, whereas Klebsiella spp. and Cronobacter spp. exhibited susceptibility to selected antibiotics with some intermediate responses. Biofilm production was detected in Klebsiella spp., Citrobacter spp., and Bacillus spp.

Conclusion: The livestock farms and abattoirs in the study areas harbours diverse airborne microorganisms, including antibiotic-resistant and biofilm-forming bacterial species, with abattoirs exhibiting the highest microbial contamination.

Influence of Chemical Preservatives on Quality Attributes of Kunu-zaki-a Nigerian Traditional Fermented Cereal Beverage

2026-10-15T11:35:21+00:00

Kunu-zaki is a traditional fermented cereal beverage valued for its accessibility but susceptible to microbial spoilage during storage. This study examined the effects of sodium benzoate (E211), potassium sorbate (E202) and their combination on the physicochemical, microbiological and sensory characteristics of kunu-zaki. Laboratory-prepared beverage samples were allocated to four treatments: sodium benzoate at 0.1% (A), potassium sorbate at 0.1% (B), a combination of both preservatives at 0.05% each (C) and an untreated control (D). Samples were assessed on days 0, 2 and 4 for pH, proximate composition and microbial counts; sensory characteristics were evaluated by 20 panellists using a five-point hedonic scale. The control pH declined from 5.8 to 3.3 during storage, whereas the corresponding day-4 pH values for treatments A, B and C were 5.2, 5.0 and 5.3, respectively. The day-4 total viable counts were 1.0 × 10⁶, 1.0 × 10⁶, 5.0 × 10⁵ and 8.0 × 10⁶ CFU/mL for A, B, C and D, respectively. No yeast/mould count was recorded for treatment C on day 4, whereas the control had a count of 5.0 × 10⁷ CFU/mL. Overall sensory acceptability scores were 3.4, 4.0, 3.8 and 1.6 for samples A–D, respectively. These findings suggest that the preservatives influenced selected quality indicators during four days of storage, although remaining microbial counts preclude conclusions about product safety.

An Alternative Approach to Extraction of Enzymes from Saccharomyces cerevisiae Using Snail Slime and Hydraulic Pressure

2026-10-17T11:18:50+00:00

The need for environmentally sustainable enzyme extraction methods has increased due to the growing demand for industrial bioprocesses. In this study, slime from Achatina achatina combined with syringe-needle hydraulic pressure was used to lyse Saccharomyces cerevisiae cells and recover a crude intracellular enzyme extract. Cells from a stock of a highly ethanol-tolerant strain of Saccharomyces cerevisiae isolated from palm wine were cultured on modified Potato Dextrose Agar (PDA) supplemented with 0.5% potassium phosphate (K₂HPO₄) and incubated in a candle jar for 3 days. A standardised yeast suspension was prepared from the resulting colonies. Equal volumes of Saccharomyces cerevisiae suspension and snail slime (1:1 ratio) were mixed and left to stand for 1 hour. The mixture was repeatedly homogenized by hydraulic pressure through repeated syringe-needle (340 µm) passage for three rounds. The lysed cell suspension was filtered through a 0.45 µm membrane filter to obtain a crude enzyme extract. The extract was evaluated for its ethanol production potential using glucose solutions at different concentrations (1%, 2.5%, 5%, 7.5%, and 10% v/v). The results showed that no ethanol was detected at 1% glucose, while ethanol yield increased progressively with increasing glucose concentration, from 0.27% v/v at 2.5% glucose concentration to 0.37% v/v at 10% glucose concentration. The absence of ethanol at 1% glucose likely reflected insufficient carbon substrate, whereas higher glucose levels supported measurable enzymatic activity. These findings indicated that snail slime-assisted lysis combined with hydraulic pressure effectively disrupted yeast cells and yielded active enzyme extracts capable of ethanol production. This approach offers a simple, eco-friendly, and low-cost alternative to conventional crude enzyme extraction techniques and may have potential applications in industrial biotechnology and cell-free ethanol production systems.

Phenotypic Drug Susceptibility Patterns of Mycobacterium tuberculosis Isolates to First-Line Anti-Tuberculosis Drugs in South-Western Nigeria

2026-10-23T09:32:27+00:00

Drug-resistant tuberculosis (TB) undermines global TB control efforts, yet comprehensive phenotypic drug susceptibility data from South-Western Nigeria remain limited. Understanding local resistance patterns is essential for optimising treatment regimens and informing programmatic responses. This study aimed to determine the phenotypic susceptibility patterns of culture-confirmed Mycobacterium tuberculosis isolates to first-line anti-tuberculosis drugs among patients in South-Western Nigeria. Seventy-four GeneXpert MTB/RIF-positive sputum specimens from patients attending health facilities in Osun, Oyo, and Lagos States underwent mycobacterial culture on Löwenstein-Jensen medium. Culture-confirmed M. tuberculosis isolates were subjected to phenotypic drug susceptibility testing against rifampicin, isoniazid, and ethambutol using the proportion method. Of 74 GeneXpert-positive specimens cultured, 51 (68.9%) yielded M. tuberculosis. Among these 51 isolates, 36 (70.6%) demonstrated resistance to at least one first-line drug. Rifampicin resistance was detected in 27 isolates (52.9%), isoniazid resistance in 18 (35.3%), and ethambutol resistance in 13 (25.5%). Fifteen isolates (29.4%) met criteria for multidrug-resistant TB (MDR-TB), defined as combined rifampicin and isoniazid resistance. Analysis of the geographical distribution revealed that 74.1% of rifampicin-resistant, 77.8% of isoniazid-resistant, and 84.6% of ethambutol-resistant isolates originated from Osun State. Substantial resistance to first-line anti-tuberculosis drugs, particularly rifampicin, was detected among culture-confirmed M. tuberculosis isolates in South-Western Nigeria. The high prevalence of drug resistance and MDR-TB highlights the need for routine culture and drug susceptibility testing to guide individualized treatment and prevent treatment failure.