Abstract

Background:
Although chicken meat is a major source of dietary protein globally, it is highly prone to microbial spoilage, especially under refrigeration, posing economic and public health risks. Psychrotrophic Pseudomonas spp., particularly Pseudomonas fluorescens and Pseudomonas aeruginosa, are key spoilage organisms due to their enzyme production, biofilm formation, and cold tolerance.

Aim:
This study determined the prevalence, virulence gene profiles, enzymatic activity, and antibiotic resistance profiles of P. fluorescens and P. aeruginosa isolated from raw chicken meat sold in supermarkets.

Methods:
Detection and isolation of Pseudomonas spp. in raw chicken samples were carried out using selective Pseudomonas agar. PCR assay used species-specific primers targeting adnA and toxA genes to confirm the presence of P. fluorescens and P. aeruginosa, respectively. The isolated P. fluorescens and P. aeruginosa were molecularly characterized using a polymerase chain reaction (PCR) assay for the presence of genes responsible for biofilm formation, proteolytic enzymes, and virulence. The proteolytic and lipolytic activities of the isolates at 30 °C and 4°C using skim milk agar and tributyrin agar. Antibiotic susceptibility was determined using the Kirby–Bauer disk diffusion method.

Results:
Of 180 samples, 61 (33.9%) were positive for P. fluorescens and 34 (18.9%) were contaminated with P. aeruginosa, as confirmed by PCR assay. Molecular characterization of the P. fluorescens isolates revealed that 41.0% were positive for aprX and 8.2% had fliC, whereas the P. aeruginosa isolates showed the presence of oprL (58.8%), lasB (11.4%), and exoS (20.6%). Gene distribution varied across retail outlets, possibly reflecting differences in hygiene and storage conditions. At 4 °C, most P. fluorescens isolates (82%) displayed proteolytic activity, and all isolates showed lipolytic activity. P. aeruginosa showed low proteolytic (29.4%) but high lipolytic (88.2%) activity. These findings show their ability to degrade meat even under refrigeration conditions. Antibiotic susceptibility testing revealed high resistance to penicillin G, ampicillin, and piperacillin among all isolates. P. fluorescens showed notable resistance to ceftazidime (100%) but remained largely susceptible to gentamicin (80.3%) and levofloxacin (82.0%). P. aeruginosa exhibited similar trends, with high susceptibility to gentamicin (85.3%) and levofloxacin (91.2%). Moderate susceptibility to amikacin was observed in both of the aforementioned species. All isolates had MAR index scores above 0.2, and 19 P. fluorescens and 5 P. aeruginosa isolates were identified as extensively drug-resistant (XDR), resistant to at least five antibiotic classes.

Conclusion:
These findings highlight the contamination of retail chicken meat by virulent, spoilage-causing, and antibiotic-resistant Pseudomonas spp., which requires improved control measures to minimize spoilage and safeguard public health.

Key words: Pseudomonas fluorescens; Pseudomonas aeruginosa; Antibiotic resistance; Protease; Lipase.