Detection and Phylogenetic Analysis of Extended-Spectrum β-Lactamase (ESBL)-Genetic Determinants in Gram-Negative Fecal-Microbiota of Wild Birds and Chicken Originated at Trimmu Barrage.

Extended-spectrum β-lactamases (ESBL) give rise to resistance against penicillin and cephalosporin antibiotics in multiple bacterial species. The present study was conducted to map genetic determinants and related attributes of ESBL-producing bacteria in three wild aquatic bird species and chickens at the "Trimmu Barrage" in district Jhang, Punjab province, Pakistan. To study the prevalence of ESBL-producing bacteria, a total of 280 representative samples were collected from wild bird species; cattle egrets ( Bubulcus ibis ), little egrets ( Egretta garzetta ) and common teals ( Anas crecca ) as well as from indigenous chickens ( Gallus gallus domesticus ) originating from a local wet market. The isolates were confirmed as ESBL producers using a double disc synergy test (DDST) and bacterial species were identified using API-20E and 20NE strips. A polymerase chain reaction (PCR) was used to detect ESBL genetic determinants and for genus identification via 16S rRNA gene amplification. A phenotypic antimicrobial susceptibility test was performed for ESBL-producing isolates against 12 clinically relevant antibiotics using the Kirby-Bauer disk diffusion susceptibility test. A phylogenetic tree was constructed for the sequence data obtained in this study and comparative sequence data obtained from GenBank. The overall prevalence of ESBL-producing bacteria was 34.64% (97/280). The highest percentage (44.28%; 31/70) of ESBL-producing bacteria was recovered from chickens ( Gallus gallus domesticus ), followed by little egrets ( Egretta garzetta ) (41.43%; 29/70), common teal ( Anas crecca ) (28.57%; 20/70) and cattle egrets ( Bubulcus ibis ) (24.28%; 17/70). Five different ESBL-producing bacteria were identified biochemically and confirmed via 16S rRNA gene sequencing, which included Escherichia coli (72; 74.23%), Enterobacter cloacae (11; 11.34%), Klebsiella pneumoniae (8; 8.25%), Salmonella enterica (4; 4.12%) and Pseudomonas aeruginosa (2; 2.06%). Based on PCR, the frequency of obtained ESBL genes in 97 isolates was bla CTX-M (51.55%), bla TEM (20.62%), bla OXA (6.18%) and bla SHV (2.06%). In addition, gene combinations bla CTX-M + bla TEM , bla TEM + bla OXA and bla CTX-M + bla SHV were also detected in 16.49%, 2.06% and 1.03% of isolates, respectively. The ESBL gene variation was significant ( p = 0.02) in different bacterial species while non-significant in relation to different bird species ( p = 0.85). Phylogenetic analysis of amino acid sequence data confirmed the existence of CTX-M-15 and TEM betalactamases. The average susceptibility of the antibiotics panel used was lowest for both Klebsiella pneumoniae (62.5% ± 24.42) and Salmonella enterica (62.5% ± 31.08) as compared to Enterobacter cloacae (65.90% ± 21.62), Pseudomonas aeruginosa (70.83% ± 33.42) and Escherichia coli (73.83% ± 26.19). This study provides insight into the role of aquatic wild birds as reservoirs of ESBL-producing bacteria at Trimmu Barrage, Punjab, Pakistan. Hence, active bio-surveillance and environment preservation actions are necessitated to curb antimicrobial resistance.