ABSTRACT
Stenotrophomonas maltophilia is a multidrug-resistant nosocomial pathogen that is difficult to identify unequivocally using current methods. Accordingly, because the presence of this microorganism in a patient may directly determine the antimicrobial treatment, conventional polymerase chain reaction (PCR) and real-time PCR assays targeting 23S rRNA were developed for the specific identification of S. maltophilia. The PCR protocol showed high specificity when tested against other species of Stenotrophomonas, non-fermentative Gram-negative bacilli and 100 clinical isolates of S. maltophilia previously identified using the Vitek system.
Subject(s)
Humans , Polymerase Chain Reaction/methods , /genetics , Stenotrophomonas maltophilia/isolation & purification , Bacterial Typing Techniques , Stenotrophomonas maltophilia/classification , Stenotrophomonas maltophilia/geneticsABSTRACT
BACKGROUND: Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, which causes infections that are often difficult to manage because of the inherent resistance of the pathogen to a variety of antimicrobial agents. In this study, we analyzed the expressions of smeABC and smeDEF and their correlation with antimicrobial susceptibility. We also evaluated the genetic relatedness and epidemiological links among 33 isolates of S. maltophilia. METHODS: In total, 33 S. maltophilia strains were isolated from patients in a tertiary hospital in Daejeon. Minimum inhibitory concentrations (MICs) of 11 antimicrobial agents were determined by using agar dilution method and E-test (BioMerieux, France). Real-time PCR analysis was performed to evaluate the expression of the Sme efflux systems in the S. maltophilia isolates. Additionally, an epidemiological investigation was performed using multilocus sequence typing (MLST) assays. RESULTS: The findings of susceptibility testing showed that the majority of the S. maltophilia isolates were resistant to beta-lactams and aminoglycosides. Twenty-one clinical isolates overexpressed smeABC and showed high resistance to ciprofloxacin. Moreover, a high degree of genetic diversity was observed among the S. maltophilia isolates; 3 sequence types (STs) and 23 allelic profiles were observed. CONCLUSIONS: The smeABC efflux pump was associated with multidrug resistance in clinical isolates of S. maltophilia. In particular, smeABC efflux pumps appear to perform an important role in ciprofloxacin resistance of S. maltophilia. The MLST scheme for S. maltophilia represents a discriminatory typing method with stable markers and is appropriate for studying population structures.
Subject(s)
Humans , Alleles , Anti-Infective Agents/pharmacology , Bacterial Proteins/genetics , Bacterial Typing Techniques , Ciprofloxacin/pharmacology , Drug Resistance, Multiple, Bacterial , Gene Expression Regulation, Bacterial , Gram-Negative Bacterial Infections/microbiology , Microbial Sensitivity Tests , Multilocus Sequence Typing , Stenotrophomonas maltophilia/classificationABSTRACT
Pseudomonads are commonly encountered in clinical samples. Usually ignored as contaminants, these organisms are known to cause nosocomial opportunistic infections like urinary tract infections (UTI). One hundred and two pseudomonads obtained in pure culture and significant numbers from 8400 consecutive urinary tract (UT) specimens were biochemically characterised upto species level by a battery of biochemical tests. Modified Stoke's disk diffusion method was followed for testing antibiotic susceptibility. Beta-lactamase production was checked by nitrocefin disk method. Minimum Inhibitory Concentration for some of these strains against imipenem was done by agar dilution method of NCCLS. Etiological significance of isolating these organisms from UT specimens was also assessed. P. aeruginosa was the commonest (76) followed by B. pickettii (10), P. putida (6), P.fluorescence (2), P. stutzeri (20) P. vesicularis (2), S. putrefaciens (2) and Stenotrophomonas maltophilia (2). Seventy six per cent of P. aeruginosa produced beta-lactamases as compared to 45% of other pseudomonads. The frequency of antibiotic resistance was gentamicin and ciprofloxacin (68.6%) followed by netilmicin (60.7%), ceftazidime (58.8%), amikacin (43.1%) and piperacillin (39.2%). In 42 patients (51.2%) the etiological significance of isolating a pseudomonad could be confirmed. Risk factors for development of UTI were present in 62(75%). Obstructive uropathy (20) followed by post operative period and surgery on urinary tract were the commonest risk factors involved. A high level of resistance was observed for imipenem (P. aeruginosa 43.7% and other pseudomonads 25%).