Detection of the genes encoding beta-lactamases in environmental enterobacteriaceae isolates

The family Enterobacteriaceae which can live in natural aquatic environments are precarious microorganisms that can lead to various infectious diseases in humans. In Enterobacteriaceae; primary resistance mechanism depending upon intense and unconscious consumption of beta-lactam antibiotics is beta-lactamase production. Enterobacteriaceae strains which synthesize one or more beta-lactamases are common causitives of the infections that result in therapeutic failure. Antimicrobial residues transferred to natural aquatic environments through food chain, agricultural irrigation activities, sewage disposal etc. cause serious community-acquired infections by unbalancing the microbial flora for the good of mutant bacteria that acquire resistance. Therefore, studies aiming at identifying the resistance to beta-lactam antibiotics especially among the environmental isolates of Enterobacteriaceae are required. The purpose of this study is to determine the beta-lactam antibiotic resistance profiles with phenotypic tests and the genes encoding resistance to beta-lactams through performing molecular methods in environmental Enterobacteriaceae isolates. Within this scope, three different antimicrobial susceptibility tests (disc diffusion test, combined disc test for extended-spectrum beta-lactamase confirmation and combined disc test for class C beta-lactamase confirmation) were performed in total 27 Enterobacteriaceae strains (20 Escherichia coli, 3 Klebsiella oxytoca, 3 Enterobacter cloacae, 1 Klebsiella pneumoniae subsp. pneumoniae) isolated from Western Black Sea coast and sea water, Lake Manyas and Lake Iznik. After the detection of resistance to beta-lactams by performing phenotypic methods, presence of the genes (blaTEM, blaSHV, blaCTX-M, blaIMP) and gene groups (CIT, MOX, FOX) encoding plasmid-mediated beta-lactamases and chromosomally-mediated AmpC beta-lactamase gene(blaAmpC) of Enterobacter cloacae were investigated with polimerase chain reaction (PCR) method. According to the results of disc diffusion method, among 15 different beta-lactam antibiotics, high level resistance to ampicillin (92.6%), carbenicillin (74.1%) and cephalothin (63%) was detected. 24 of the strains (88.9%) were determined to be resistant to more than one of the beta-lactam antibiotics. In extended-spectrum beta-lactamase (ESBL) and class C beta-lactamase (AmpC) confirmation tests, ESBL production in 3 E. coli; AmpC production in 2 E .coli and 3 E. cloacae strains were confirmed. Both enzymes were detected in one of these strains. In the study, presence of blaTEM in 3 E. coli strains; blaSHV in 6 E. coli, 2 K. pneumoniae and 1 K. oxytoca strains; blaCTX-M type ESBL encoding gene in 3 E.coli strains were determined. CIT gene group was determined only in 2 E. coli isolates and E. cloacae strains with no plasmid- mediated AmpC encoding genes were defined to express the chromosomal blaAmpC gene. Among 3 different E. coli isolates from Western Black Sea; one blaTEM+blaSHV, one blaSHV+CIT and one blaCTX-M+CIT gene profile was experienced. In our study, antimicrobial susceptibility test results and beta-lactamase encoding gene profiles identified with PCR in environmental Enterobacteriaceae isolates, were generally compatible. This study revealed the beta-lactam antibiotic resistance phenotype reflected by genetic factors which can be transferred between the bacteria growing in aquatic environments. In this context; our study which we associate the processes between the beta-lactamase production and the genetic determinants encoding these enzymes in the bacteria of Enterobacteriaceae family isolated from the aquatic environments will enlighten the similar prospective investigations.