Characterization and Antimicrobial Resistance of Escherichia coli and Its Serotypes Isolated from Poultry Feed in Relation to Seasons in Karachi, Pakistan

 The increasing prevalence of Escherichia coli as a foodborne pathogen in poultry poses a high risk to food safety. The resistant strains of E. coli may contribute resistant genes to human endogenous flora, causing fatal diseases. Moreover, these pathogens are serious threats to poultry farming.

 The current study aimed to investigate the effects of seasonal variations on the bacterial load of E. coli and to evaluate its antibiogram profile.

 All feed samples were evaluated for the identification of E. coli and its serotypes, using conventional culture methods and biochemical characterization. Positive samples were confirmed by polymerase chain reaction (PCR) assay. The bacterial load of E. coli was estimated by measuring the total viable count, and the antibiogram data were calculated using two methods, that is, disc diffusion method and minimum inhibitory concentration (MIC) measurement.

 Of 204 feed samples investigated, 38 isolates were positive for E. coli. All positive samples were also confirmed via universal and species-specific PCR assays, and 8/38 were documented as E. coli 0157:H7 strains. The bacterial load of E. coli was also determined by measuring the total viable count, and the results revealed the highest ratio (6.44×108 CFU/g) from June to August and the lowest ratio (2.06×108 CFU/g) from December to February. The multidrug resistance of E. coli O157:H7 was validated by antimicrobial susceptibility tests since all isolates showed high resistance to chloramphenicol, penicillin derivatives, fluoroquinolones, and oxytetracycline, respectively, and were only susceptible to aminoglycosides.

 Considering the high bacterial load of E. coli from June to August, the poultry industry needs to establish appropriate and effective hygienic and storage policies, especially during these alarming months. Moreover, surfacing and propagation of resistant strains of these pathogens may obscure future assessments for treatment purposes.