Evidence of nosocomial Stenotrophomonas maltophilia cross-infection in a neonatology unit analyzed by three molecular typing methods

Characterisation of trehalose-6-phosphate phosphatases from bacterial pathogens

The trehalose biosynthesis pathway has recently received attention for therapeutic intervention combating infectious diseases caused by bacteria, helminths or fungi. Trehalose-6-phosphate phosphatase (TPP) is a key enzyme of the most common trehalose biosynthesis pathway and a particularly attractive target owing to the toxicity of accumulated trehalose-6-phosphate in pathogens. Here, we characterised TPP-like proteins from bacterial pathogens implicated in nosocomial infections in terms of their steady-state kinetics as well as pH- and metal-dependency of their enzymatic activity. Analysis of the steady-state kinetics of recombinantly expressed enzymes from Acinetobacter baumannii, Corynebacterium diphtheriae and Pseudomonas stutzeri yielded similar kinetic parameters as those of other reported bacterial TPPs. In contrast to nematode TPPs, the divalent metal ion appears to be bound only weakly in the active site of bacterial TPPs, allowing the exchange of the resident magnesium ion with other metal ions. Enzymatic activity comparable to the wild-type enzyme was observed for the TPP from P. stutzeri with manganese, cobalt and nickel. Analysis of the enzymatic activity of S. maltophilia TPP active site mutants provides evidence for the involvement of four canonical aspartate residues as well as a strictly conserved histidine residue of TPP-like proteins from bacteria in the enzyme mechanism. That histidine residue is a member of an interconnected network of five conserved residues in the active site of bacterial TPPs which likely constitute one or more functional units, directly or indirectly cooperating to enhance different aspects of the catalytic activity.

The association between the microbes in the tracheobronchial aspirate fluid and bronchopulmonary dysplasia in preterm infants

OBJECTIVE

The study aimed to evaluate the association between microbes in the lower respiratory tract (LRT) and the srisk for severe bronchopulmonary dysplasia (sBPD) in premature infants.

METHODS

We conducted a retrospective, single-center study of preterm infants who were admitted to the neonatal intensive care unit (NICU) of Southern Medical University Affiliated Maternal & Child Health Hospital of Foshan, China, between January 2015 and December 2017. The microbes in the LRT were screened by using tracheobronchial aspirate fluid (TAF) culture.

RESULTS

One hundred and fifty-five infants were included in the analysis. Among 155 infants, 41 were diagnosed with sBPD, and 114 were diagnosed without sBPD. There were significant differences between infants with and without sBPD in regard to birth weight (BW), gestational age (GA), the duration of endotracheal ventilation and supplemental oxygen. The incidence of retinopathy (ROP) and sepsis was higher in the sBPD infants than in the infants without sBPD. There was a difference in the detection rate of Gram-negative bacteria (GNB) between the two groups. Stenotrophomonas maltophilia and Klebsiella pneumoniae were mainly detected in TAF.

CONCLUSIONS

The LRT microbes were different between infants with and without sBPD, and GNB is more frequently detected in sBPD infants.

Stenotrophomonas maltophilia isolated from patients exposed to invasive devices in a university hospital in Argentina: molecular typing, susceptibility and detection of potential virulence factors

Purpose. The aim of this work was to investigate the presence of selected potential virulence factors, susceptibility and clonal relatedness among 63 Stenotrophomonas maltophilia isolates recovered from patients exposed to invasive devices in a university hospital in Argentina between January 2004 and August 2012.Methodology. Genetic relatedness was assessed by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and pulsed-field gel electrophoresis (PFGE). Isolates were characterized by antimicrobial resistance, the presence and/or expression of potential virulence determinants, and virulence in the Galleria mellonella model.Results/Key findings. ERIC-PCR generated 52 fingerprints, and PFGE added another pattern. Resistance to trimethoprim-sulfamethoxazole (6.35 %), levofloxacin (9.52 %) and ciprofloxacin (23.80 %) was detected. All isolates were susceptible to minocycline. All isolates were lipase, protease and siderophore producers, while all but Sm61 formed biofilms. However, 11/63 isolates did not amplify the major extracellular protease-coding gene (stmPr1). Sm61 is an stmPr1-negative isolate, and showed (as did Sm13 and the reference strain K279a) strong proteolysis and siderophore production, and high resistance to hydrogen peroxide. The three isolates were virulent in the G. mellonella model, while Sm10, a low-resistance hydrogen peroxide stmPr1-negative isolate, and weak proteolysis and siderophore producer, was not virulent.Conclusion. This is the first epidemiological study of the clonal relatedness of S. maltophilia clinical isolates in Argentina. Great genomic diversity was observed, and only two small clusters of related S. maltophilia types were found. Minocycline and trimethoprim-sulfamethoxazole were the most active agents. S. maltophilia virulence in the G. mellonella model is multifactorial, and further studies are needed to elucidate the role of each potential virulence factor.

Intraabdominal abscess caused by Stenotrophomonas maltophilia: A case report

INTRODUCTION

Stenotrophomonas maltophilia usually causes nosocomial infections, but intraabdominal abscesses or organ/space surgical site infection (SSI) secondary to this organism has been rarely reported. Here, we reported a rare case of SSI that presented as intraabdominal abscess caused by S. maltophilia.

PRESENTATION OF CASE

A 68-year-old woman presented to our hospital with transverse colon cancer. Further work up with abdominal computed tomography (CT) revealed left renal cell carcinoma. Transverse colon resection and left kidney partial resection were performed. On post-operative day 10, she started to have fever at 38°C and repeat abdominal CT showed intraabdominal abscess. Empiric treatment with piperacillin/tazobactam (TAZ/PIPC) was initiated. However, fever persisted and the abscess size did not change despite 10 days of antibiotic. On post-operative day 20, drainage of intraabdominal abscess was performed. TAZ/PIPC was then shifted to meropenem (MEPM). After two days, S. maltophilia was identified in the culture of the abscess, and MEPM was shifted to minocycline (MINO). Fever disappeared after 7days of treatment and abdominal CT after 14 days showed almost complete resolution of the abscess.

DISCUSSION

S. maltophilia is a multi-drug resistant, aerobic, non-glucose fermenting, non-sporulating, Gram-negative bacillus. S. maltophilia may cause a variety of infections, but intraabdominal abscesses as a manifestation of SSI due to this organism is relative rare.

CONCLUSION

Although usually a non-pathogenic organism or colonizer, S. maltophilia can cause organ/space SSI in an immunocompromised host. Therefore, clinicians should be aware of the possibility that S. maltophilia may cause organ/space SSI.

Genotypic and Phenotypic Characterization of Stenotrophomonas maltophilia Strains from a Pediatric Tertiary Care Hospital in Serbia

Background

Stenotrophomonas maltophilia is an environmental bacterium and an opportunistic pathogen usually associated with healthcare-associated infections, which has recently been recognized as a globally multi-drug resistant organism. The aim of this study was genotyping and physiological characterization of Stenotrophomonas maltophilia isolated in a large, tertiary care pediatric hospital in Belgrade, Serbia, hosting the national reference cystic fibrosis (CF) center for pediatric and adult patients.

Methods

We characterized 42 strains of cystic fibrosis (CF) and 46 strains of non-cystic fibrosis (non-CF) origin isolated from 2013 to 2015 in order to investigate their genetic relatedness and phenotypic traits. Genotyping was performed using sequencing of 16S rRNA gene, Pulse Field Gel Electrophoresis (PFGE) and Multi locus sequencing typing (MLST) analysis. Sensitivity to five relevant antimicrobial agents was determined, namely trimethoprim/sulfamethoxazole (TMP/SMX), chloramphenicol, ciprofloxacin, levofloxacin and tetracycline. Surface characteristics, motility, biofilm formation and adhesion to mucin were tested in all strains. Statistical approach was used to determine correlations between obtained results.

Results

Most of the isolates were not genetically related. Six new sequence types were determined. Strains were uniformly sensitive to all tested antimicrobial agents. The majority of isolates (89.8%) were able to form biofilm with almost equal representation in both CF and non-CF strains. Swimming motility was observed in all strains, while none of them exhibited swarming motility. Among strains able to adhere to mucin, no differences between CF and non-CF isolates were observed.

Conclusions

High genetic diversity among isolates implies the absence of clonal spread within the hospital. Positive correlation between motility, biofilm formation and adhesion to mucin was demonstrated. Biofilm formation and motility were more pronounced among non-CF than CF isolates.

Evaluation of Three Molecular Typing Techniques for Nonfermentative Gram-Negative Bacilli

Objective:

To evaluate three different DNA techniques for typing nonfermentative gram-negative bacilli isolated from Latin American hospitals.

Design:

One hundred twenty-six nonfermentative gram-negative bacilli were typed.

Participants:

Pseudomonas aeruginosa(n = 64) andAcinetobacter baumannii(n = 42) samples were obtained from blood cultures of patients admitted to 10 medical centers in Latin America during 1998 andStenotrophomonas maltophilia(n = 20) samples were obtained from patients admitted to the Hospital São Paulo between 1999 and 2001.

Methods:

All samples were typed using automated ribotyping, PFGE, and ERIC-PCR. The discriminatory power for each technique was calculated using Hunter's generalized formula.

Results:

All strains could be typed by automated ribotyping and ERIC-PCR, but two strains (1.6%) were not typeable by PFGE. All three techniques showed 100% reproducibility. The time to obtain the results was shorter for automated ribotyping and ERIC-PCR compared with PFGE. Likewise, the costs for ERIC-PCR and PFGE were lower than those for automated ribotyping. The interpretation of results was more complicated and more difficult with ERIC-PCR than with both PFGE and automated ribotyping. All techniques presented excellent discriminatory power forP. aeruginosa(0.98). PFGE presented the highest discriminatory power (0.94) forA. baumannii,and both PFGE and ERIC-PCR showed higher discriminatory power (0.90 for both) than automated ribotyping (0.82) for S.maltophilia.

Conclusions:

PFGE showed the highest discriminatory power for typing these nonfermentative gram-negative bacilli. However, automated ribotyping and ERIC-PCR can provide results in a shorter time period with similar discriminatory power.

An overview of various typing methods for clinical epidemiology of the emerging pathogen Stenotrophomonas maltophilia

Typing of bacterial isolates has been used for decades to study local outbreaks as well as in national and international surveillances for monitoring newly emerging resistant clones. Despite being recognized as a nosocomial pathogen, the precise modes of transmission of Stenotrophomonas maltophilia in health care settings are unknown. Due to the high genetic diversity observed among S. maltophilia clinical isolates, the typing results might be better interpreted if also environmental strains were included. This could help to identify preventative measures to be designed and implemented for decreasing the possibility of outbreaks and nosocomial infections. In this review, we attempt to provide an overview on the most common typing methods used for clinical epidemiology of S. maltophilia strains, such as PCR-based fingerprinting analyses, pulsed-field gel electrophoresis, multilocus variable number tandem repeat analysis, and multilocus sequence type. Application of the proteomic-based mass spectrometry by matrix-assisted laser desorption ionization-time of flight is also described. Improvements of typing methods already in use have to be achieved to facilitate S. maltophilia infection control at any level. In the near future, when novel Web-based platforms for rapid data processing and analysis will be available, whole genome sequencing technologies will likely become a highly powerful tool for outbreak investigations and surveillance studies in routine clinical practices.

Recurrent Stenotrophomonas maltophilia bacteremia after iliac crest bone graft harvest

We describe a rare case of recurrent Stenotrophomonas maltophilia bacteremia in a previously healthy 45-year-old man. The infection was caused by osteomyelitis at the site of an iliac crest bone graft harvest. A genetic analysis using enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) revealed that the blood isolates and pathogens obtained from the surgical wound were identical. Initial treatment with levofloxacin and cefozopran was ineffective, but the patient's infection was successfully treated by long-term administration of latamoxef and trimethoprim-sulfamethoxazole. The present case suggests that attention should be given to the possibility of S. maltophilia infection in any situations.

Stenotrophomonas maltophilia strains isolated from a university hospital in Japan: genomic variability and antibiotic resistance

The diversity within the genetic and antibiotic resistance profiles and the production of virulence-associated enzymic activities of 66 Stenotrophomonas maltophilia strains collected from a university hospital in Japan in 2005 were studied. PFGE analysis of the collection indicated that a variety of profiles were present. MLST analysis of nine selected strains showed that four of the six sequence types identified were novel. These results indicated that there was a high degree of genetic diversity between the strains and that S. maltophilia strains isolated in Japan might be genetically divergent from those in Europe. The majority of strains were resistant to piperacillin (93.9 %), ceftazidime (84.8 %), imipenem (100 %), aztreonam (98.5 %), gentamicin (81.8 %), amikacin (87.9 %), ciprofloxacin (84.8 %), tetracycline (97.0 %) and chloramphenicol (78.8 %), although levofloxacin was effective against 77.3 % of the strains. Most of the strains showed multidrug resistance and carried the class 1 integron, but no strain showed transmission of antibiotic resistance by conjugation. Although haemolytic activity was not detected in any of the strains, protease and lipase activities were detected in 86.4 % and 31.8 % of the strains, respectively.

Comparison of pulsed-field gel electrophoresis and three rep-PCR methods for evaluating the genetic relatedness of Stenotrophomonas maltophilia isolates

AIMS

In this study, three facile repetitive-sequence PCR (rep-PCR) techniques have been compared with the pulsed-field gel electrophoresis (PFGE) method for differentiating the genetic relatedness of clinical Stenotrophomonas maltophilia isolates.

METHODS AND RESULTS

The dendrograms of 20 S. maltophilia isolates were constructed based on the data obtained from PFGE and three PCR-based methods, i.e. enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR), BOX-PCR and repetitive extragenic palindromic-PCR (REP-PCR). When compared with PFGE, ERIC-PCR displayed a much lower discriminatory power, whereas BOX-PCR and REP-PCR had a comparable discriminatory power for close genetic-related isolates.

CONCLUSION

BOX-PCR and REP-PCR can be convenient and effective methods for evaluating the close genetic relatedness of clinical S. maltophilia isolates.

SIGNIFICANCE AND IMPACT OF THE STUDY

A rapid method for determining S. maltophilia's close genetic relatedness provides a convenient tool for understanding the epidemiology of S. maltophilia.

Pseudooutbreak of Stenotrophomonas maltophilia bacteremia in a general ward

BACKGROUND

Stenotrophomonas maltophilia is a significant nosocomial pathogen and is commonly isolated in the hospital environment. We investigated the risk factors for a bloodstream pseudooutbreak of S maltophilia in a general ward.

METHODS

On November 24 and 25, 2005, 7 patients without evidence of sepsis were reported as positive for blood culture with S maltophilia from blood samples collected on November 21 and 22, 2005. We conducted an epidemiologic investigation and a case-control study of this pseudooutbreak.

RESULTS

All 7 S maltophilia showed the same antibiogram and an indistinguishable pattern on pulsed-field gel electrophoresis. The observational study revealed multiple lapses in infection control, including multiple use of a single bottle of saline for dilution of antibiotics. A case-control study showed that one health care worker, who collected blood samples from 6 of 7 patients, was a significant risk factor for the pseudooutbreak of S maltophilia (P < .05).

CONCLUSION

We suggest that the combination of multiple lapses in infection control and the blood-collecting behavior of a health care worker might be the cause of the pseudooutbreak of S maltophilia.

Stenotrophomonas maltophilia: the significance and role as a nosocomial pathogen

Stenotrophomonas maltophilia is a significant pathogen that primarily affects patients with co-morbid illnesses, usually malignancies, who have been hospitalized for prolonged periods and received broad-spectrum antibiotic therapy. The organism has been associated with an expanding spectrum of clinical manifestations associated with high case to fatality ratios. Therapy of these infections presents a significant challenge both for the clinician and the microbiologists because of its high-level antibiotic resistance to most of the currently used agents and methodological difficulties in susceptibility testing with this organism.

Enterobacterial repetitive intergenic consensus PCR is a useful tool for typing Mycobacterium chelonae and Mycobacterium abscessus isolates

Outbreaks of rapidly growing mycobacterium (RGM) infections are increasingly being reported worldwide. Information about genetic relatedness of isolates obtained during outbreaks can provide opportunities for prompt intervention. Pulsed-field gel electrophoresis (PFGE) is expensive, time consuming, and labor intensive. Other than that, Mycobacterium abscessus isolates can suffer DNA degradation during electrophoresis. Polymerase chain reaction (PCR)-based methods are cheaper, faster, and easier to perform, but discriminatory power varies depending on the primer used. In this study, we tested the competence of enterobacterial repetitive intergenic consensus (ERIC) PCR in comparison with PFGE to distinguish unrelated isolates (24 Mycobacterium chelonae and 24 M. abscessus) obtained from human and/or environmental samples and to group 56 isolates from 6 outbreaks confirmed epidemiologically, caused by M. chelonae and M. abscessus after ophthalmologic refractive surgery and mesotherapy. Enterobacterial repetitive intergenic consensus PCR presented discriminatory power, calculated using Simpson's index of diversity, of 0.989 for M. abscessus and 0.975 for M. chelonae and grouped outbreak isolates in distinct groups showing epidemiologic concordance. Pulsed-field gel electrophoresis also grouped outbreak isolates and presented discriminatory power of 0.972 and 0.993 for M. abscessus and M. chelonae, respectively. DNA from 8 (22%) of 36 M. abscessus isolates analyzed showed degradation during electrophoresis. Compared with PFGE and epidemiologic information as the gold standard, ERIC PCR is a simple, high throughput, affordable, reproducible, and discriminatory molecular typing method for inference of genetic relatedness of RGMs of the M. chelonae-abscessus group.

Stenotrophomonas maltophilia: antimicrobial resistance and molecular typing of an emerging pathogen in a Turkish university hospital

Despite its limited pathogenicity, Stenotrophomonas maltophilia is an emerging nosocomial pathogen. This study investigated the isolation frequency, antimicrobial resistance and genotypic relationships of 205 S. maltophilia isolates from 188 patients in a university hospital between 1998 and 2003. Susceptibility profiles for 11 antimicrobial agents were determined by the NCCLS agar dilution method for non-fermentative bacteria, while enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR and pulsed-field gel electrophoresis (PFGE) were used for genotyping of the isolates. Of the 205 isolates, 56.1% were isolated in the last 2 years of the study. The risk of S. maltophilia isolation was higher in intensive care units, S. maltophilia was isolated mostly (86.8%) after hospitalisation for >or= 48 h, and 90.4% of the patients had underlying diseases. Resistance levels were>60% for all antimicrobial agents tested except co-trimoxazole. High genetic diversity was found among the S. maltophilia isolates, and cross-infection with S. maltophilia was not common. Although ERIC-PCR revealed fewer genotypes than PFGE, it proved to be a rapid and easy method for S. maltophilia genotyping, and was more economical than PFGE.

Nosocomial Stenotrophomonas maltophilia cross-infection: three cases in newborns

BACKGROUND

Increased nosocomial Stenotrophomonas maltophilia infection rates in newborns, especially in recent years, are a significant cause for concern. These cases are the second case group in the literature to have been identified as nosocomial cross-infection with S. maltophilia in neonates.

OBJECTIVE

To investigate the clinical, microbiological, and epidemiologic features of the outbreak caused by S. maltophilia in the neonatal intensive care unit within a period of 7 days.

METHODS

Three cases with nosocomial S. maltophilia infection considered to be the result of cross-transmission were prospectively analyzed. Arbitrarily primed polymerase chain reaction (AP-PCR) performed with M13 primer and pulsed-field gel electrophoresis (PFGE) of genomic DNA after digestion with XbaI were used to determine clonal relationship among the isolates. Results S. maltophilia was isolated from the blood cultures of all 3 patients. Molecular typing confirmed that the 3 cases were epidemiologically linked.

CONCLUSIONS

Opportunistic pathogens such as S. maltophilia can lead to major problems in neonates. Molecular typing is helpful to improve effective control programs for preventing the spread of the infection.

Spread of Stenotrophomonas maltophilia colonization in a pediatric intensive care unit detected by monitoring tracheal bacterial carriage and molecular typing

In our pediatric intensive care unit in Tours (France), intubated and ventilated inpatients are systematically monitored for tracheal bacterial colonization twice a week. This led us to detect five patients colonized with Stenotrophomonas maltophilia over a 4-month period. Molecular typing of the isolates using random amplified polymorphism DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) confirmed that four of the five isolates were genetically related. The strict isolation of carriers and improvements in hygiene measures stopped the spread. This systematic strategy prevented pulmonary nosocomial infections or allowed their early detection. Moreover, it has made it possible to assess the efficiency of care practices continuously.

Risk factors for Stenotrophomonas maltophilia bacteremia in oncology patients: a case-control study

OBJECTIVE

To characterize risk factors for Stenotrophomonas maltophilia bloodstream infection in oncology patients.

DESIGN

A 3:1 case-control study.

SETTING

Stem Cell Transplant and Leukemic Center at Barnes-Jewish Hospital (St. Louis), a 1,442-bed, tertiary-care teaching hospital with a 26-bed transplantation ward.

METHOD

From, June 1999 to April 2001, 13 patients with S. maltophilia bacteremia were compared with 39 control-patients who were on the transplantation unit on the same day as the case-patients' positive blood cultures. Information collected included patient demographics, medical history, history of transplantation, transplantation type, graft versus host disease, neutropenia, antibiotic use, chemotherapy, mucositis, diarrhea, the presence of central venous catheter(s), cultures, and concomitant infections.

RESULTS

Significant risk factors for S. maltophilia bacteremia included severe mucositis (7 [53.8%] of 13 vs 8 [20.5%] of 39; P = .034), diarrhea (7 [53.8%] of 13 vs 8 [20%] of 39; P = .034), and the use of metronidazole (9 [69.2%] of 13 vs 8 [20.5%] of 39; P = .002). In addition, the number of antibiotics used (median, 9 vs 5; P < .001), duration of mucositis (median, 29 vs 15 days; P = .032), and length of hospital stay (median, 34 vs 22 days; P = .017) were significantly different between case- and control-patients. Nine S. maltophilia isolates tested by pulsed-field gel electrophoresis were found to be distinctly different.

CONCLUSION

Interventions to ameliorate the severity of mucositis, reduce antibiotic pressure, prevent diarrhea, and promote meticulous central venous catheter care may help prevent S. maltophilia bloodstream infection in oncology patients. The role of gastrointestinal tract colonization as a potential source of S. maltophilia bacteremia in oncology patients deserves further investigation.

Molecular typing strategies

Nosocomial infections among infants in neonatal intensive care units are an increasing cause of morbidity and mortality. Efforts to rapidly detect, contain and ultimately prevent cross-transmission of these pathogens require constant vigilance by members of the epidemiology team. A vital component of an epidemiological evaluation is the ability to assess the interrelatedness of clinical isolates. This review focuses on the basic principles, strengths and weaknesses of some of the most commonly used molecular-based procedures, which determine clonal identity of outbreak strains in neonatal settings. Published evidence for the cogent selection of the method best suited for studying a particular organism and technological advances that await the new science of Molecular Epidemiology are also presented. The appropriate use of molecular typing technologies should enable reliable tracking of epidemic clones and thereby enhance the effectiveness of infection control strategies.

Molecular epidemiology of Stenotrophomonas maltophilia in a university hospital

The aim of this investigation was to study the molecular epidemiology of Stenotrophomonas maltophilia in a university hospital in Italy. Sixty-one clinical isolates were collected from 43 patients during a two-year period. The majority of specimens were from the respiratory tract (41 of 43) of patients in the adult intensive care unit (ICU) (19 of 43) or cystic fibrosis (CF) patients (13 of 43). Genotypic analysis by pulsed-field gel electrophoresis (PFGE) of clinical isolates identified 31 different PFGE patterns. Although most patients were infected or colonized by different S. maltophilia clones, clones with identical genotype were isolated in patients from ICU, where two separate outbreaks were identified. Antimicrobial susceptibility identified a multi-resistant phenotype in all S. maltophilia PFGE clones. The majority of PFGE clones identified (six of seven clones from patients in the ICU) were susceptible to fluoroquinolones. Mechanical ventilation was associated with S. maltophilia acquisition in the ICU.

Use of random amplified polymorphic DNA PCR to examine epidemiology of Stenotrophomonas maltophilia and Achromobacter (Alcaligenes) xylosoxidans from patients with cystic fibrosis

Stenotrophomonas maltophilia and Achromobacter (Alcaligenes) xylosoxidans have been increasingly recognized as a cause of respiratory tract colonization in cystic fibrosis (CF). Although both organisms have been associated with progressive deterioration of pulmonary function, demonstration of causality is lacking. To examine the molecular epidemiology of S. maltophilia and A. xylosoxidans in CF, isolates from patients monitored for up to 2 years were fingerprinted using a PCR-based randomly amplified polymorphic DNA (RAPD-PCR) method. Sixty-one of 69 CF centers screened had 183 S. maltophilia culture-positive patients, and 46 centers had 92 A. xylosoxidans-positive patients. At least one isolate from each patient was genotyped, and patients with > or =10 positive cultures (12 S. maltophilia cultures, 15 A. xylosoxidans cultures) had serial isolates genotyped. In addition, centers with multiple culture-positive patients were examined for evidence of shared clones. There were no instances of shared genotypes among different CF centers. Some patients demonstrated isolates with a single genotype throughout the observation period, and others had intervening or sequential genotypes. At the six centers with multiple S. maltophilia culture-positive patients and the seven centers with multiple A. xylosoxidans-positive patients, there were three and five instances of shared genotypes, respectively. The majority of shared isolates were from pairs who were siblings or otherwise epidemiologically linked. These findings suggest RAPD-PCR typing can distinguish unique CF isolates of S. maltophilia and A. xylosoxidans, person-to-person transmission may occur, there are not a small number of clones infecting CF airways, and patients with long-term colonization may either have a persistent organism or may acquire additional organisms over time.

Antimicrobial susceptibilities of unique Stenotrophomonas maltophilia clinical strains

Susceptibility to 41 antimicrobials was studied with 99 Stenotrophomonas maltophilia strains, and different pulsed-field gel electrophoresis profiles were identified among 130 prospectively collected isolates. Moxalactam, doxycycline, minocycline, and clinafloxacin displayed the highest activity (> or = 98% susceptibility). Ticarcillin resistance (75%) was reverted by clavulanate in 25% of strains. Trimethoprim-sulfamethoxazole resistance was 26.2% (> or = 4 [trimethoprim]/76 [sulfamethoxazole] microg/ml) and dropped to 11.1% when an 8/152-microg/ml breakpoint was applied based on its bimodal MIC distribution. Resistance was lower when unique strains were considered, because clonal organisms contribute to resistance.

Heterogeneous antimicrobial resistance patterns in polyclonal populations of coagulase-negative staphylococci isolated from catheters

Most cases of nosocomial bacteremia are catheter related, and coagulase-negative staphylococci (CoNS) are the microorganisms most frequently associated with these infections. Subtle morphological differences are frequently found among CoNS colonies cultured from infected catheters. The aim of this study was to analyze the significance of the morphological heterogeneity observed in these CoNS populations. With this purpose in mind, the clonal composition of the CoNS populations obtained from a selection of nine catheters was analyzed by two different molecular techniques, arbitrarily primed-PCR and DNA macrorestriction analysis by pulsed-field gel electrophoresis. Twenty CoNS morphotypes were included for analysis, and four single colonies representative of each morphotype were selected. Morphological differences between colonies were found to correlate in all cases with differences at the molecular level. Unique fingerprints were also obtained for some isolates which were indistinguishable from other representatives of the same morphotypes. Differences in the molecular patterns among the isolates were associated in most of the cases with differences in the antimicrobial susceptibility patterns. The frequent isolation of polyclonal CoNS populations from catheters, with heterogeneous antimicrobial susceptibility patterns, has relevant epidemiologic and therapeutic implications in the context of catheter-related infections.