Abstract
Foodborne pathogens are leading cause of illness and death globally in humans, animals and
birds. The present study was aimed to investigate the prevalence of bacterial foodborne
pathogens in chicken meat, milk, beef and egg, their antibacterial resistance (ABR) and genomic
diversity of resistant genes in those pathogens. The study was conducted in Mymensingh and
Gazipur districts of Bangladesh during the period from July 2015 to June 2018. A total of 302
milk (n=110), chicken meat (n=62), egg (n=80) and beef (n=50) samples were collected from
Bangladesh Agricultural University (BAU) dairy farm, surrounding small- and large-scale dairy
farms and retail market of municipal area. Foodborne pathogens were identified and
characterized by conventional and molecular techniques. Based on sequence data, the genomic
diversity of ABR genes was evaluated with CLC genomic work bench 8.0 using NCBI data. The
overall prevalence of E. coli, Salmonella spp. and Staphylococcus aureus were 49%, 26% and 45%
in all specimens, respectively. The prevalence of E. coli was significantly (p< 0.05) higher in beef
(74%) than that of egg (53%) and milk (30%) samples. Similarly, the prevalence of Salmonella
spp. was significantly (p< 0.05) higher in chicken meat (66%) than that of egg (10%) and milk
(3%) samples. In addition, the prevalence of S. aureus was significantly (p< 0.05) higher in
chicken meat (63%) than that of beef (40%) and milk (32%) samples. An overall 64% (207/326)
of the isolates were multi-drug resistant (MDR). E. coli isolates were highly resistant to
erythromycin (80%-91%) followed by oxytetracycline (65%-91%) but highly sensitive to
amikacin (93%-100%) and ciprofloxacin (74%-93%) originating from almost all food samples.
Salmonella spp. isolates were highly resistant to erythromycin (92%-100%) followed by
oxytetracycline (61%-100%) and azithromycin; and sensitive to amikacin (95%-100%) in almost
all the cases. S. aureus isolates originated from chicken and egg specimen were highly resistant
(64%-81%) to oxytetracycline and highly sensitive to amikacin (100%) followed by gentamicin
(70%-95%), ciprofloxacin (73%-95%) and sulpha-trimethoprim (69%-90%) in almost all
specimens. The MDR E. coli were most common in milk and chicken meat (89%-91%); MDR
Salmonella were prevalent in milk, egg and chicken meat (89%-100%). However, MDR S. aureus
isolates were found only in chicken meat (69%). The tetA and strA genes were detected mostly
from E. coli in egg (48%) and chicken meat (42%), respectively. The tetA, tetB, sull, sul2 and
ant(3")-la ABR genes as single and double were most commonly detected from Salmonella spp.
of egg origin but 3 to 4 genes together from that of chicken meat origin. The mecA gene was
detected from 45% S. aureus isolates of beef. In this study, two tetA genes were identified in E.
coli originated from beef samples but they did not express phenotypic resistant. Again tetB and
ant(3")-la genes were detected in Salmonella spp. originated from beef sample but they were
susceptible to oxytetracycline and gentamicin, respectively. The gene sul-2 was also found in six
Salmonella spp. isolates originated from chicken meat (04), milk (01) and egg (01) samples but
they were susceptible to sulpha-trimethoprim. No tetA gene in E. coli was identified in 8 beef, 20
chicken, 10 egg and 09 milk specimens but they were resistant to oxytetracycline. Phylogenetic
analysis revealed 99%-100% similarity of the tetA and strA gene sequences in E. coli; tetA,
ant(3")-la, sul-1 and sul2 gene sequences in Salmonella spp. to each other and to that of other
isolates containing same gene reported from other countries. However, homology analysis
revealed considerable nucleotide heterogeneity in mecA gene sequences in Staphylococcus aureus
which rendered them into two clusters, although most of these sequences showed 96%-100%
homologous with each other. A little heterogeneity was also observed in ant(3)-la and sull gene
sequences in Salmonella spp.. In conclusion, it can be suggested that physicians and veterinary
doctors should select amikacin, ciprofloxacin, gentamicin and sulpha-trimethoprim for the
treatment of salmonellosis, colibacillosis and stahylococcosis. Hygiene and proper sanitation
should be maintained from the farm to fork. Government and livestock sector are suggested to
ensure the sales of antibiotics through prescription by the registered veterinarian to prevent
their misuse.