Incidence and molecular characterization of extended-spectrum beta-lactamase (ESBL)-producing Salmonella enterica and Escherichia coli of avifauna origin in Pakistan

Members of Enterobacteriaceae are known to produce extended-spectrum beta-lactamases (ESBL) which hydrolyze the beta-lactam group of antibiotics. The existence of ESBL-producing Salmonella enterica (S. enterica) and Escherichia coli (E. coli) harbored by urban avifauna was investigated in this study. Dropping samples (n= 180) were collected from six different bird species in the district Jhang, Punjab province, Pakistan. Isolation and identification of ESBL isolates were made by using cefotaxime- (4 mg/L) supplemented MacConkey agar and double disc synergy test (DDST). Polymerase chain reaction (PCR) was performed for the detection of four different ESBL genes including bla CTX-M, bla TEM, bla SHV and bla OXA. A total of 42.69% isolates were confirmed as ESBL via DDST including 30.64% S. enterica and 49.54% E. coli. The incidence of ESBL S. enterica and ESBL E. coli was found highest in egret (Ardea alba) and pigeon (Columba livia) as 64.28% and 78.95%, respectively. The bla CTX-M gene was detected in 57.89% and 64.81% of isolates of S. enterica and E. coli, respectively. Among other genes in S. enterica and E. coli, bla TEM (21.05%, 20.4%); bla SHV (15.78%, 9.26%), and bla OXA (5.26%, 5.56%) were detected, respectively. All of the tested isolates were found resistant to at least one of the thirteen antimicrobial agents except meropenem. To the best of our knowledge, this is the first study reporting the incidence and genetic diversity of ESBL bacteria associated with urban avifauna in Pakistan. The urban avifauna can serve as a potential subject of bio-surveillance to monitor the emergence of antimicrobial-resistant bacteria.