Status of Antimicrobial Resistance in Bacteria Isolated From Kenyan Chickens

Abstract

The term antimicrobial resistance refers to the ability of microorganisms to grow in the presence of an antimicrobial (drug) at a concentration that would normally kill them or inhibit their growth. Antimicrobial resistance has become a big threat to global health; having risen to dangerously high levels in all parts of the World, making it difficult to treat infectious diseases. This is forcing patients to incur extra expenses as they have to buy more expensive second-generation or third-generation medicines. Also, as a result of medicines not being effective, patients are forced to stay longer in hospitals; this translates to higher hospital bills. In an effort to establish the antimicrobial resistance status of bacteria isolated from chickens, a cross-sectional study was conducted to demonstrate the antimicrobial resistance profiles of bacteria isolated from three groups of chickens [sick (clinical), farm and slaughter]. The three chicken groups were studied so as to determine whether there are any differences, with respect to antimicrobial resistance, between them. Intestinal swabs were taken from the first 50 chickens brought to the clinic (for post mortem examination) during the study period, while, for farm and market (slaughterhouse) categories, cloacal swabs were randomly taken from a total of 122 birds. Bacteriological isolation and characterization was then carried out, using the conventional methods, and six genera were identified; the most prevalent being organisms of the genus Streptococcus (40.7%), followed by E. coli (31.4%), then Staphylococcus (26.2%), Bacillus (9.3), Proteus (2.9%). The least isolated were in the genus Corynebacterium (2.3%). Due to financial constraints, while all the E. coli isolates were tested for antibiotic susceptibility/resistance, only a few of the other bacterial isolates were tested, using the 8 antibiotics supplied by HiMedia (HiMedia Laboratories-INDIA). Overall, the study demonstrated existence of antimicrobial resistance, both single and multiple (some up to 7 xvi antimicrobials), in the tested bacteria. The antimicrobial resistance was mostly towards the commonly-used antibiotics, namely: ampicillin (76.0%), tetracycline (71.1%), sulphamethoxazole (69.5%) and co-trimoxazole (65.5%). They were least resistant to Gentamycin (8.3%). The study also showed that, overall, a higher percentage of Escherichia coli isolates demonstrated multi-drug resistance compared to the other isolates. When comparing the three study groups, the general picture indicated higher multidrug resistance prevalence in bacteria isolated from clinical cases, followed by market birds (Table 3.3). It was, however, encouraging that there were some bacterial strains that were still susceptible to the commonly-used antimicrobials The resistant E. coli isolates were further tested for carriage of antimicrobial resistant genes; three Extended-spectrum β-lactamase (ESBL) - coding genes: blaTEM, dfrA1 and blaCTX-M, using multiplex Polymerase Chain Reaction. Only 3 (10.7%) of the 28 isolates tested had the dfrA1gene; none carried the blaCTX-M and blaTEM. This showed that 25 (89.3%) of the tested resistant E. coli isolates utilised other means to express their antimicrobial resistance. Results from the two studies will thus contribute towards data on current antimicrobial resistance status in bacteria harboured by chickens in Kenya, which will help in informing the policy makers as they embark in their fight towards reduction of antimicrobial resistance.