Detection of CTX-M gene in extended spectrum β-lactamases producing Enterobacteriaceae isolated from bovine milk

Abstract

Extended spectrum β-lactamases producing Enterobacteriaceae (ESBL-E) have emerged recently as the main cause that facilitates the spreading of antibiotic resistance worldwide. Due to its composition and nutritive values, raw cow milk is vulnerable to bacterial contamination from different sources, especially ESBL-E. Accordingly, present study aimed to detect the ESBL-E in the raw milk of healthy cows. 80 raw cow milk samples were collected from unorganized farms and cows belong to individual owners and investigated for the presence of ESBL-E with the main focusing on CTX-M type. The bacterial isolation was performed using selective MacConkey agar plus cefotaxime (MC+), while PCR was used to confirm the species of the isolated bacteria and presence of CTX-M gene. The results showed that 28.75%(23/80) samples were ESBL-E positive and distributed as following, 82.61%(19/23) were pure E. coli isolates, 4.35%(1/23) was pure K. pneumoniae isolate and finally, 13.04%(3/23) were mixed of both E. coli and K. pneumoniae isolates. Moreover, the total number of positive ESBL-E was 26 isolates with the majority of them were belong to E. coli and recorded 84.61%(22/26), while K. pneumoniae was recorded less 15.39%(4/26). Additionally, the CTX-M gene was successfully identified in all ESBL-E positive isolates by using PCR, including E. coli and K. pneumoniae isolates. The results of this study assert the importance of raw cow milk as a potential source of ESBL-E that might be transmitted to humans.

Keywords

• milk
• pcr
• enterobacteriaceae
• esbl-e
• ctx-m