Epidemiology and antimicrobial resistance of pathogenic E. coli in chickens from selected poultry farms in Zambia

Escherichia coli (E. coli) bacteria areone of the most important pathogens in the poultry industry and a leading cause of cellulitis, septicemia, and airsacculitis infections. Antimicrobial resistance in pathogenic E. coli is of particular interest because it is the most common gram-negative pathogen in chickens. Cloacal, eggs, and environmental samples were randomly collected from three commercial farms in Zambia.  Specimens were cultured and phenotypically identified pathogenic E. coli using Congo red dye-binding test (CR-test). The pathogenic E. coli underwent antimicrobial susceptibility testing for six antibiotics. The study aimed to isolate and determine antimicrobial resistance patterns of pathogenic E. coli from chickens in Chisamba and Lusaka districts. A total of 417 samples were collected and processed microbiologically. E. coli was isolated from 333(79.9%; 95%CI=75.23-82.98) samples.  The highest number was isolated from cloacal swabs 313(75.1%; 95%CI=70.19-78.52%) while 18(4.3%; 95%CI=2.75-6.72%) was from litter in poultry houses, and 1(0.2%) of each from eggs and environment swabs. Of 333 isolates, 62(18.6%; 95%CI=14.90-23.28%) were pathogenic. The bacteria demonstrated 100% and 92% resistance to tetracycline and cephalexin, respectively, while 77% were susceptible to gentamicin. The results also showed that 4.8% of pathogenic isolates exhibited multidrug resistance (MDR) to all six antibiotics combined, while 17.7% were resistant to five antibiotics. The isolation of antimicrobial-resistant pathogenic E. coli suggests that the bacteria were exposed to these antibiotics before sampling. The resistant bacteria are a serious public health concern, causing ailments that are difficult to treat with antimicrobial drugs. Consequently, there is a need to intensify education campaigns on bio-security measures and good-hygienic practices.