Genotypic and phenotypic relationships between clinical and environmental isolates of Stenotrophomonas maltophilia. (1/220)

While the gram-negative bacterium Stenotrophomonas maltophilia is used in biotechnology (e.g., for biological control of plant pathogens and for bioremediation), the number of S. maltophilia diseases in humans has dramatically increased in recent years. A total of 40 S. maltophilia isolates from clinical and environmental sources (plant associated and water) was investigated to determine the intraspecies diversity of the group and to determine whether or not the strains could be grouped based on the source of isolation. The isolates were investigated by phenotypic profiling (enzymatic and metabolic activity and antibiotic resistance patterns) and by molecular methods such as temperature-gradient gel electrophoresis of the 16S rRNA gene fragment, PCR fingerprinting with BOX primers, and pulsed-field gel electrophoresis (PFGE) after digestion with DraI. Results of the various methods revealed high intraspecies diversity. PFGE was the most discriminatory method for typing S. maltophilia when compared to the other molecular methods. The environmental strains of S. maltophilia were highly resistant to antibiotics, and the resistance profile pattern of the strains was not dependent on their source of isolation. Computer-assisted cluster analysis of the phenotypic and genotypic features did not reveal any clustering patterns for either clinical or environmental isolates.  (+info)

Genomic diversity of the genus Stenotrophomonas. (2/220)

The clinical and environmental importance of Stenotrophomonas bacteria requires thorough, molecular studies on their epidemiology and taxonomy. In order to obtain a complete genomic profile of this genus, over 100 Stenotrophomonas maltophilia strains from various origins were investigated by AFLP fingerprinting. A subset of these strains was analysed by DNA hybridization and 16S rDNA sequencing. In contrast to their high phenotypic homogeneity, the strains were found to be very heterogeneous genotypically by AFLP fingerprinting. Nevertheless, ten cores of highly similar strains representing ten genomic groups were observed. The same groups could be retrieved by DNA hybridizations and also, partly, by 16S rDNA sequence analysis. The intergroup DNA similarities were too high to create confident species delineations, neither could the genomic groups be characterized by phenotypic features.  (+info)

Nosocomial pneumonia likely caused by Stenotrophomonas maltophilia in two patients with polymyositis. (3/220)

We report two cases of polymyositis (PM) complicated with nosocomial pneumonia probably caused by Stenotrophomonas maltophilia, which was resistant to multiple antimicrobials. In the first case, the chest CT findings and high serum endotoxin level as well as sputum culture results were helpful for the proper diagnosis and the therapy was successful. However the second patient died of a lung abscess in spite of the intensive antibiotic therapy. When PM patients develop pneumonia unresponsive to various antibiotics, a multi-drug-resistant bacteria such as Stenotrophomonas maltophilia should be considered as the pathogen.  (+info)

Levofloxacin in vitro activity and time-kill evaluation of Stenotrophomonas maltophilia clinical isolates. (4/220)

The in vitro activity of levofloxacin and eight other antimicrobial agents against 60 clinical isolates of Stenotrophomonas maltophilia was determined by an agar dilution method using 10(4) and 10(6) cfu/spot inocula. At the lower inoculum, 85.0% of the isolates were susceptible to levofloxacin but only 58.3% were susceptible to ofloxacin; at the higher inoculum, 78.3% were susceptible to levofloxacin and 36.7% to ofloxacin. In time-kill studies, levofloxacin exerted bactericidal activity within 4 h. With ofloxacin and ciprofloxacin bacterial regrowth was observed after 8 h. Levofloxacin may represent an alternative drug in the treatment of infections caused by S. maltophilia.  (+info)

Multiple antibiotic resistance in Stenotrophomonas maltophilia: involvement of a multidrug efflux system. (5/220)

Clinical strains of Stenotrophomonas maltophilia are often highly resistant to multiple antibiotics, although the mechanisms of resistance are generally poorly understood. Multidrug resistant (MDR) strains were readily selected by plating a sensitive reference strain of the organism individually onto a variety of antibiotics, including tetracycline, chloramphenicol, ciprofloxacin, and norfloxacin. Tetracycline-selected MDR strains typically showed cross-resistance to erythromycin and fluoroquinolones and, in some instances, aminoglycosides. MDR mutants selected with the other agents generally displayed resistance to chloramphenicol and fluoroquinolones only, although two MDR strains (e.g., K1385) were also resistant to erythromycin and hypersusceptible to aminoglycosides. Many of the MDR strains expressed either moderate or high levels of a novel outer membrane protein (OMP) of ca. 50 kDa molecular mass, a phenotype typical of MDR strains of Pseudomonas aeruginosa hyperexpressing drug efflux systems. Indeed, the 50-kDa OMP of these S. maltophilia MDR strains reacted with antibody to OprM, the outer membrane component of the MexAB-OprM MDR efflux system of P. aeruginosa. Similarly, a ca. 110-kDa cytoplasmic membrane protein of these MDR strains also reacted with antibody to the MexB component of the P. aeruginosa pump. The outer and cytoplasmic membranes of several clinical S. maltophilia strains also reacted with the anti-OprM and anti-MexB antibodies. N-terminal amino acid sequencing of a cyanogen bromide-generated peptide of the 50-kDa OMP of MDR strain K1385, dubbed SmeM (Stenotrophomonas multidrug efflux), revealed it to be very similar to a number of outer membrane multidrug efflux components of P. aeruginosa and Pseudomonas putida. Deletion of the L1 and L2 beta-lactamase genes confirmed that these enzymes were responsible for the bulk of the beta-lactam resistance of K1385 and its parent. Still, overexpression of the MDR efflux mechanism in an L1- and L2-deficient derivative of K1385 did yield a modest increase in resistance to a few beta-lactams. These data are consistent with the MDR efflux mechanism(s) playing a role in the multidrug resistance of S. maltophilia.  (+info)

Degradation and mineralization of high-molecular-weight polycyclic aromatic hydrocarbons by defined fungal-bacterial cocultures. (6/220)

This study investigated the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) in liquid media and soil by bacteria (Stenotrophomonas maltophilia VUN 10,010 and bacterial consortium VUN 10,009) and a fungus (Penicillium janthinellum VUO 10, 201) that were isolated from separate creosote- and manufactured-gas plant-contaminated soils. The bacteria could use pyrene as their sole carbon and energy source in a basal salts medium (BSM) and mineralized significant amounts of benzo[a]pyrene cometabolically when pyrene was also present in BSM. P. janthinellum VUO 10,201 could not utilize any high-molecular-weight PAH as sole carbon and energy source but could partially degrade these if cultured in a nutrient broth. Although small amounts of chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene were degraded by axenic cultures of these isolates in BSM containing a single PAH, such conditions did not support significant microbial growth or PAH mineralization. However, significant degradation of, and microbial growth on, pyrene, chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene, each as a single PAH in BSM, occurred when P. janthinellum VUO 10,201 and either bacterial consortium VUN 10,009 or S. maltophilia VUN 10,010 were combined in the one culture, i.e., fungal-bacterial cocultures: 25% of the benzo[a]pyrene was mineralized to CO(2) by these cocultures over 49 days, accompanied by transient accumulation and disappearance of intermediates detected by high-pressure liquid chromatography. Inoculation of fungal-bacterial cocultures into PAH-contaminated soil resulted in significantly improved degradation of high-molecular-weight PAHs, benzo[a]pyrene mineralization (53% of added [(14)C]benzo[a]pyrene was recovered as (14)CO(2) in 100 days), and reduction in the mutagenicity of organic soil extracts, compared with the indigenous microbes and soil amended with only axenic inocula.  (+info)

Failure of an automated blood culture system to detect nonfermentative gram-negative bacteria. (7/220)

During a 1-year study we observed that both aerobic and anaerobic blood culture bottles from patients were negative by the BacT/Alert system during a 7-day incubation period. However, upon subcultivation of negative bottles, growth of Pseudomonas aeruginosa was detectable. In an attempt to explain this observation, aerobic BacT/Alert Fan bottles were seeded with a defined inoculum (0.5 McFarland standard; 1 ml) of Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, P. aeruginosa, Stenotrophomonas maltophilia, or Acinetobacter baumannii. Half of the inoculated bottles were loaded into the BacT/Alert system immediately, and the remainder were preincubated for 4, 8, 16, and 24 h at 36 degrees C. With preincubation all bottles seeded with the Enterobacteriaceae signaled positive during the next 1.5 h. Organisms in bottles seeded with the nonfermentative species P. aeruginosa and A. baumannii remained undetected by the BacT/Alert system for 7 days. S. maltophilia was detected if the preincubation time was equal or less than 8 h. Without preincubation all bottles seeded with the Enterobacteriaceae or nonfermentative species signaled positive. Since nonfermentative species seem to enter a state of bacteriostasis within the preincubation period, we reasoned that an unknown factor is consumed. Accordingly, a smaller inoculum should allow the detection of nonfermentative species, even after preincubation, and serial dilutions of P. aeruginosa were detected in preincubated bottles. In this case preincubated bottles signaled positive faster than bottles without preincubation. We conclude that all bottles from clinical settings should be subcultured prior to loading to avoid false negatives. An alternative may be preincubation at room temperature.  (+info)

Comparative activity of new quinolones against 326 clinical isolates of Stenotrophomonas maltophilia. (8/220)

Stenotrophomonas maltophilia is an important emerging pathogen causing a variety of infections in severely ill patients. This microorganism is inherently resistant to many antibiotics, and only a few therapeutic options are available. The principal aim of this study was to assess the in vitro activity of new quinolones against this pathogen. Three hundred and twenty-six single clinical isolates were tested in this study. The MIC(90) was 16 mg/L for ciprofloxacin, 8 mg/L for levofloxacin and gatifloxacin, 4 mg/L for trovafloxacin, moxifloxacin and sparfloxacin and 2 mg/L for clinafloxacin. At a 2 mg/L concentration, a C(max) lung:MIC ratio of >/=10 can be reached for 95%, 84.3%, 83.1% and 81.5% of isolates, respectively, for clinafloxacin, trovafloxacin, moxifloxacin and sparfloxacin (P < 0. 001 compared with levofloxacin and ciprofloxacin). In spite of the rare but serious adverse events associated with the new-generation quinolones, these agents may become very useful in the treatment of certain severe or life-threatening infectious conditions due to S. maltophilia, notably lower respiratory tract infections.  (+info)