Detection of TEM-, SHV- and CTX-M-type β-lactamase production among clinical isolates of Salmonella species

Abstract

Enteric fever is a major public health problem in developing countries. Due to the problem of resistance to first-line drugs and fluoroquinolone, cephalosporins are currently used for treatment of enteric fever. Cephalosporin resistance in Salmonella spp. is mainly due to production of extended-spectrum b-lactamases (ESBLs). The majority of ESBLs in Salmonella are derivatives of the TEM and SHV b-lactamase families. The objectives of this study were to detect antibiotic susceptibility patterns, ESBL production and TEM-, SHV-and CTX-M-encoding genes (bla TEM , bla SHV and bla CTX-M ) among clinical isolates of Salmonella spp. A total of 134 Salmonella isolates [Salmonella Typhi (n5101), Salmonella Paratyphi A (n531), Salmonella Paratyphi B (n51) and Salmonella Typhimurium (n51)] were included in this study. Multidrug resistance was seen in 5/ 134 (3.73 %) isolates, all of which belonged to serotype S. Typhi. A better susceptibility profile was observed for first-line drugs (ampicillin, chloramphenicol, co-trimoxazole and tetracycline) and cephalosporins (cefotaxime, ceftazidime, ceftriaxone, cefixime and cefepime). However, 131 (97.76 %) of the 134 isolates were resistant to nalidixic acid and one (0.75 %) was resistant to ciprofloxacin. TEM-1-type b-lactamase (bla TEM-1 ) was detected in six (4.47 %) of the 134 isolates, which belonged to the serotype S. Typhi. All six TEM-positive isolates were negative for the bla SHV gene and none of the isolates was positive for the bla CTX-M gene. The presence of the bla TEM gene encoding TEM-1 b-lactamase is believed to confer resistance only to penicillins and early cephalosporins; however, the resistance spectrum of TEM-1 descendants may extend to second-, third-and fourth-generation cephalosporins. The ESBLs derived from TEM-1 differ from their progenitors by as few as 1 aa, and have the ability to hydrolyse third-generation cephalosporins. Therefore, appropriate selection and rotation of antibiotics as well as continuous monitoring of antibiotic susceptibility profiles could help to control the emergence and spread of resistant strains.

Patterns in antimicrobial susceptibility of Salmonellae isolated at a tertiary care hospital in northern India

“…Further, high resistance to ampicillin was also seen which was in contrast to studies from different parts of India, which showed high rates of sensitivity to the drug among S. Typhi and S. Paratyphi A isolates1012. All our isolates were sensitive to ceftriaxone and cefotaxime contrary to studies which reported resistance to ceftriaxone1015.…”

Aeromonas hydrophilafrom marketed mullet (Mugil cephalus) in Egypt: PCR characterization ofβ-lactam resistance and virulence genes

“…Primarily bla TEM is associated with penicillins and early cephalosporins resistance (Elumalai et al . ). However, the genetic mutation of bla TEM could result in the emergence of bacteria that resist broad spectrum cephalosporins (Weldhagen et al .…”

“…Our findings also identified bla CTX-M , which is responsible for the hydrolysis of CTX, only in 24% of the isolated A. hydrophila. Primarily bla TEM is associated with penicillins and early cephalosporins resistance (Elumalai et al 2014).…”

Enteric fever in India: current scenario and future directions

“…A number of molecular studies have failed to identify extended‐spectrum beta lactamases such as CTX‐M in S . typhi in India , although there are case reports of these in S . paratyphi A .…”

“…Over the last decade, there have been sporadic reports of typhoid resistant to third-generation cephalosporins [68], but these isolates are uncommon. A number of molecular studies have failed to identify extended-spectrum beta lactamases such as CTX-M in S. typhi in India [66,69,70], although there are case reports of these in S. paratyphi A [71]. Further case reports have identified plasmid-mediated ampC production [72,73] and, in one case, proved that the plasmid was transferrable to E. coli by transconjugation experiments [73].…”