Mechanisms of antibiotic resistance in Gram-negative bacteria from coastal area of the Kaštela Bay

Abstract

U cilju razumijevanja uloge onečišćenog mora u širenju humanih potencijalnih patogena rezistentnih na antibiotike, istražena je učestalost i mehanizmi rezistencije u bakterijskim zajednicama priobalnog područja Kaštelanskog zaljeva. U razdoblju 2008.-2010. godine ukupno 2,569 bakterijskih izolata iz morske vode i faune je identificirano, te je utvrđena njihova fenotipska osjetljivost na antibiotike. Karakterizacija gena rezistencije, s posebnim naglaskom na β-laktamaze proširenog spektra, je provedena primjenom metoda PCR, sekvenciranja DNK, konjugacije i Southern blot ibridizacije. Genetička srodnost izolata iz mora i kliničkih izolata je ispitana RAPD i PFGE metodama genotipizacije. Značajna učestalost TEM, SHV i CTX-M β-laktamaza (4.7%) je utvrđena u vrstama iz porodice Enterobacteriaceae, te rodova Aeromonas, Pseudomonas, Burkholderia, Stenotrophomonas i Vibrio. Molekularne analize ukazuju da Enterobacteriaceae kao komenzali probavnog sustava imaju značajnu ulogu u prijenosu gena, osobito CTX-M β-laktamaza na humane patogene, što je od velikog značaja za razumijevanje epidemiologije gena rezistencije a time i mogućih posljedica onečišćenja na zdravlje ljudi.To understand the role of polluted marine environment in dissemination of human pathogenic bacteria resistant to antibiotics, we explored the incidence and mechanisms of resistance in bacterial communities from coastal area of the Kaštela Bay. From 2008 to 2010 2,569 isolates were isolated from seawater and fauna, identified and determined their phenotypic susceptibility to antibiotics. Characterization of resistance genes, with focus on extended spectrum-β-lactamases, were performed by PCR, sequencing, conjugation and Southern blot hybridization, while genetic relationship of marine isolates and isolates from Split University Hospital were examined using RAPD and PFGE genotyping. TEM, SHV and CTX-M β-lactamases were identified in a significant percent (4.7%) of Enterobacteriaceae, Aeromonas, Pseudomonas, Burkholderia, Stenotrophomonas and Vibrio isolates. Molecular analyses indicated that enterobacteriaceae as human commensals play a significant role in the transmission of genes, specifically CTX-M β-lactamases, from marine isolates to human pathogens, which is of great importance in understanding the epidemiology of resistance genes and, thus, the potential consequences of faecal pollution on human health