ABSTRACT
BACKGROUND: Acinetobacter baumannii causes difficult-to-treat nosocomial infections, which often lead to morbidity due to the development of antimicrobial drug resistance and expression of virulence genes. Data regarding the association of resistance to colistin, a last treatment option, and the virulence gene expression of A. baumannii is scarce. METHODS: We evaluated the MLVA genotype, antimicrobial resistance, and biofilm formation of 100 A. baumannii isolates from burn patients, and further compared the in vitro and in vivo expression of four virulence genes among five colistin-resistant A. baumannii (Cst-R-AB) isolates. Five Cst-R-AB isolates were tested; one from the present study, and four isolated previously. RESULTS: Our results showed that reduced expression of recA, along with increased in vivo expression of lpsB, dnaK, and blsA; are associated with colistin resistance among Cst-R-AB isolates. Differences in virulence gene expressions among Cst-R-AB isolates, may in part explain common discrepant in vitro vs. in vivo susceptibility data during treatment of infections caused by Cst-R-AB. CONCLUSIONS: Our findings highlight the intricate relationship between colistin-resistance and virulence among A. baumannii isolates, and underscore the importance of examining the interactions between virulence and antimicrobial resistance toward efforts to control the spread of multidrug-resistant A. baumannii (MDR-AB) isolates, and also to reduce disease severity in burn patients with MDR-AB infection.
Subject(s)
Acinetobacter baumannii/genetics , Acinetobacter baumannii/pathogenicity , Anti-Bacterial Agents/therapeutic use , Biofilms/growth & development , Colistin/therapeutic use , Drug Resistance, Multiple, Bacterial/genetics , Acinetobacter Infections/drug therapy , Acinetobacter Infections/microbiology , Acinetobacter baumannii/drug effects , Bacterial Outer Membrane Proteins/biosynthesis , Bacterial Outer Membrane Proteins/genetics , Bacterial Proteins/biosynthesis , Bacterial Proteins/genetics , Burns/microbiology , DNA-Binding Proteins/biosynthesis , DNA-Binding Proteins/genetics , Humans , Mannosyltransferases/biosynthesis , Mannosyltransferases/genetics , Microbial Sensitivity Tests , Rec A Recombinases/biosynthesis , Rec A Recombinases/genetics , Virulence/geneticsABSTRACT
BACKGROUND: Multidrug resistant strains of Acinetobacter baumannii (MDR-AB) have emerged as alarming nosocomial pathogens among patients with burning. OBJECTIVES: The current study aimed to determine the susceptibility of A. baumannii species, carbapenems resistance patterns, and their association with IS Aba 1 and IS Aba 4 elements upstream of the bla OXA-like genes, and the distribution of international clone (IC) of A. baumannii isolates among patients with burning in Tehran, Iran. MATERIALS AND METHODS: In the current study, 62 A. baumannii species isolates from patients with burning in Tehran, Iran, in 2012 were evaluated for the antimicrobial susceptibility, genetic relationships, ICs, carbapenemase encoding genes, and insertion elements IS Aba upstream of bla OXA-like genes. RESULTS: The highest rates of susceptibility were observed with colistin (88.7%) and tigecycline (82.2%). The extensively drug-resistance and pan drug-resistance were observed in 37.1% and 8.1% of the isolates, respectively. About 98.3% of 17 genotypes categorized into three distinct clusters. Thirty-six of the 62 isolates (58%) belonged to the IC II lineage. The most prevalent acquired OXA-type carbapenemase was bla OXA-23-like (62.9%). IS Aba 1 and IS Aba 4 were detected upstream of bla OXA-23-like genes in 45.1% and 12.9% of isolates, respectively. In 32.2% of all isolates, IS Aba 1 laid upstream of bla OXA-51-like genes. The PCR results were negative for carbapenemase genes of Ambler class A and B, except bla VIM-2 . (1.6%). CONCLUSIONS: It was the first study that attempted to detect the insertion elements IS Aba and IC lineages in MDR-AB species isolated from patients with burning in Iran.
