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Expert Review of Molecular Diagnostics 05/2010; 10(4):375-80. · 4.86 Impact Factor
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ABSTRACT: This article reviews the microbiological diagnostic tests that are currently available for the detection of M pneumoniae, C pneumoniae, and Legionella spp; their clinical performance; and their future in the clinical microbiology laboratory. When implementing a strategy, a balance between performance criteria (sensitivity, specificity) and convenience criteria (clinical utility, turnaround time, and costs) will have to be defined. In the end, this should result in the optimization of clinical patient management.
Infectious disease clinics of North America 03/2010; 24(1):229-248. · 2.29 Impact Factor
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ABSTRACT: Catheter-related bloodstream infection (CRBSI) results in significant attributable morbidity and mortality. In this randomized, double-blind, placebo-controlled trial, we studied the efficacy and safety of a daily ethanol lock for the prevention of CRBSI in patients with a tunnelled central venous catheter (CVC).
From 2005 through 2008, each lumen of the CVC of adult hematology patients was locked for 15 minutes per day with either 70%-ethanol or placebo, where after the lock solution was flushed through. As a primary endpoint, the incidence rates of endoluminal CRBSI were compared.
The intent-to-treat analysis was based on 376 patients, accounting for 448 CVCs and 27,745 catheter days. For ethanol locks, the incidence of endoluminal CRBSI per 1000 CVC-days was 0.70 (95%-CI, 0.4-1.3), compared to 1.19 (95% confidence interval, 0.7-1.9) for placebo (incidence rate-ratio, 0.59; 95% confidence interval, 0.27-1.30; P = .19). For endoluminal CRBSI according to the strictest definition (positive hub culture and identical bacterial strain in blood), a 3.6-fold, non-significant, reduction was observed for patients receiving ethanol (2 of 226 versus 7 of 222; P = .103). No life-threatening adverse events were observed. More patients receiving ethanol discontinued lock-therapy (11 of 226 versus 1 of 222; P = .006) or continued with decreased lock-frequency (10 of 226 versus 0 of 222; P = .002), due to non-severe adverse events.
In this study, the reduction in the incidence of endoluminal CRBSI using preventive ethanol locks was non-significant, although the low incidence of endoluminal CRBSI precludes definite conclusions. Therefore, the lack of statistical significance may partially reflect a lack of power. Significantly more patients treated with ethanol locks discontinued their prophylactic treatment due to adverse effects, which were non-severe but reasonably ethanol related. Additional studies should be performed in populations with higher incidence of (endoluminal) CRBSI. Alternative sources of bacteremia, like exoluminal CRBSI or microbial translocation during chemotherapy-induced mucositis may have been more important in our patients.
ClinicalTrials.gov NCT00122642.
PLoS ONE 01/2010; 5(5):e10840. · 4.09 Impact Factor
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ABSTRACT: We have analyzed a representative selection of the HARMONY meticillin-resistant Staphylococcus aureus strain collection originating from 11 European countries (Cookson, B.D. et al., 2007, J. Clin. Microbiol. 45: 1830–1837) with the DiversiLab™ System, Pulsed-Field Gel Electrophoresis (PFGE) and Multi-Locus Sequence Typing (MLST). Simpson's diversity indices were 0.905, 0.877 and 0.860 for PFGE, MLST and DiversiLab™, respectively. All methods displayed concordant classification of the MRSA strains, although with divergent resolution and reproducibility.
Journal of microbiological methods 02/2009; · 2.43 Impact Factor
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Diana F M Willemse-Erix,
Maarten J Scholtes-Timmerman,
Jan-Willem Jachtenberg, Willem B van Leeuwen,
Deborah Horst-Kreft,
Tom C Bakker Schut,
Ruud H Deurenberg,
Gerwin J Puppels,
Alex van Belkum,
Margreet C Vos,
Kees Maquelin
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ABSTRACT: Hospital-acquired infections (HAI) increase morbidity and mortality and constitute a high financial burden on health care systems. An effective weapon against HAI is early detection of potential outbreaks and sources of contamination. Such monitoring requires microbial typing with sufficient reproducibility and discriminatory power. Here, a microbial-typing method is presented, based on Raman spectroscopy. This technique provides strain-specific optical fingerprints in a few minutes instead of several hours to days, as is the case with genotyping methods. Although the method is generally applicable, we used 118 Staphylococcus aureus isolates to illustrate that the discriminatory power matches that of established genotyping techniques (numerical index of diversity [D]=0.989) and that concordance with the gold standard (pulsed-field gel electrophoresis) is high (95%). The Raman clustering of isolates was reproducible to the strain level for five independent cultures, despite the various culture times from 18 h to 24 h. Furthermore, this technique was able to classify stored (-80 degrees C) and recent isolates of a methicillin-resistant Staphylococcus aureus-colonized individual during surveillance studies and did so days earlier than established genotyping techniques did. Its high throughput and ease of use make it suitable for use in routine diagnostic laboratory settings. This will set the stage for continuous, automated, real-time epidemiological monitoring of bacterial infections in a hospital, which can then be followed by timely corrective action by infection prevention teams.
Journal of clinical microbiology 01/2009; 47(3):652-9. · 4.16 Impact Factor
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ABSTRACT: Although Staphylococcus aureus is a bacterial species of medical significance, only approximately 30% of all humans carry staphylococcal cells persistently but asymptomatically in their nasopharynx and/or other body sites. This goes largely unnoticed by the host, which shows that in the natural situation the human ecosystem is hospitable or at least receptive to the bacteria and that by a process of co-evolution this has lead to a state of mutual acceptance or tolerance. However, upon disturbance of this balanced, neutral state, localized or disseminated invasive infection can occur. Unfortunately, the events leading to infection are still largely unknown and especially the causal events leading to the transition from colonization to infection are ill-defined in vivo. Whether certain genotypes of S. aureus are more prone to colonise and/or infect humans is still quite heavily debated. The genetic population structure of S. aureus has been largely solved by using a number of different DNA polymorphism-interrogating laboratory methods. However, even this major effort has not (yet) revealed major clues with respect to colonisation and infection potency of the clonal lineages that were thus identified, except for the fact that certain lineages are highly epidemic. The overall picture is that in principle all S. aureus strains can become invasive given the proper circumstances. What these, primarily host-defined circumstances are is still enigmatic. However, a large variety of staphylococcal virulence and colonization factors have been identified as well as a number of host' colonisation and infection susceptibility traits. How these are specifically involved in colonisation and infection has been experimentally substantiated in only a limited number of cases. The present review paper will explore the relevance of these and other, for instance environmental factors that define the colonisation or infection state in humans. When the nature of these states would be known in more detail, this knowledge could be used to design novel and empirical, knowledge-driven means of preventing colonisation from proceeding into S. aureus infection.
Infection Genetics and Evolution 11/2008; 9(1):32-47. · 3.13 Impact Factor
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ABSTRACT: The objective of this study was to evaluate the test characteristics of a modified BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) assay on individual and pooled samples in a setting of low MRSA prevalence. The results of the polymerase chain reaction (PCR) assay were compared with culture results from a selective phenol red mannitol broth subcultured after 48 h. Sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) were calculated. For individual testing, 581 samples from 201 persons were collected; 18 (3.2%) were MRSA culture positive. Five hundred ten broths from 174 persons were combined in 106 pools after overnight incubation; 8 pools (7.5%) contained 1 or more MRSA culture-positive specimens. There were no inhibited PCR tests. The combined sensitivity of individual and pooled specimens was 92% (95% confidence interval [CI], 73-99%), the specificity was 98% (95% CI, 96-99%), and the PPV and NPV were 63% and 99.7%, respectively. Our modified procedure gives satisfactory results, and the pooling of broths may reduce costs.
Diagnostic Microbiology and Infectious Disease 09/2008; 61(4):396-401. · 2.53 Impact Factor
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ABSTRACT: Methicillin-resistant Staphylococcus aureus sequence type 398 (ST398 MRSA) was identified in Dutch pigs and pig farmers. ST398 methicillin-susceptible S. aureus circulates among humans at low frequency (0.2%) but was isolated in 3 human cases of bacteremia (2.1%; p = 0.026). Although its natural host is probably porcine, ST398 MRSA likely causes infections in humans.
Emerging Infectious Diseases 04/2008; 14(3):479-83. · 6.79 Impact Factor
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Damian C Melles,
Erna Pauw,
Linda van den Boogaard,
Hélène A M Boelens,
Jenny Peters,
Justine K Peeters,
Hanneke Witsenboer, Willem B van Leeuwen,
Henri A Verbrugh,
Alex van Belkum,
Jan L Nouwen
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ABSTRACT: It has been shown that persistent Staphylococcus aureus nasal carriage results in increased bacterial dispersal and a higher risk of infection compared to non-or-intermittent S. aureus carriage. Although many studies investigated S. aureus nasal carriage in HIV patients, none compared persistent carriage to non-persistent carriage nor were studies performed in the HAART era. We investigated the host-microbe interplay of persistent S. aureus nasal carriage in HIV-infected patients by studying host determinants of persistent carriage as well as the genetic structure of S. aureus strains isolated. We compared this genetic structure with the previously determined population structure of S. aureus isolates obtained from healthy individuals. Between February 2004 and June 2005 all HIV patients visiting the outpatient department of Erasmus MC (Rotterdam, The Netherlands) were asked to participate in this study. Participants were interviewed and screened for persistent S. aureus carriage using two semi-quantitative nasal swab cultures. For 443 patients two cultures were available, 131 (29.6%) were persistent carriers, which is significantly higher as compared to healthy individuals from the same geographic region (17.6%; P<0.0001). Male sex (odds ratio [OR], 2.22; 95% confidence interval [CI], 1.32-3.73), current smoking (OR, 0.58; 95% CI, 0.38-0.90), Pneumocystis jiroveci pneumonia (PCP) prophylaxis (OR, 0.39; 95% CI, 0.16-0.97) and antiretroviral therapy (OR, 0.61; 95% CI, 0.38-0.98) were independent determinants of persistent carriage. Only two strains were mecA positive (1.2%) and no PVL positive strains were detected. The population structure of S. aureus strains isolated from HIV patients appeared to be strongly overlapping with that of S. aureus isolates from healthy individuals.
Microbes and Infection 02/2008; 10(2):151-8. · 3.10 Impact Factor
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ABSTRACT: Staphylococcus aureus produces compounds that interfere with complement deposition. We hypothesized that humans have developed countermeasures to staphylococcal complement evasion and we screened for single nucleotide polymorphisms in the serine protease C1 inhibitor (C1INH) gene at amino acid position 480 (valine vs. methionine) and nasal carriage of S. aureus. In our study cohort, 38 individuals were persistently colonized by S. aureus, whereas 50 were invariably culture-negative. A trend was observed towards an increased prevalence of the Val/Val genotype in noncarriers compared to persistent carriers (OR 0.50, P=0.07). The Val/Val genotype was significantly overrepresented in noncarriers compared to 463 Caucasian blood donors (OR 0.52, P=0.02). These findings suggest that susceptibility to S. aureus nasal carriage is associated with the C1INH V480M polymorphism.
FEMS Immunology & Medical Microbiology 09/2007; 50(3):330-2. · 2.44 Impact Factor
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ABSTRACT: Ten samples containing various amounts of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus, methicillin-resistant Staphylococcus epidermidis (MRSE), and combinations thereof were distributed to 51 laboratories for molecular diagnostics testing. Samples containing 10(2) to 10(3) MRSA cells were frequently reported to be negative. MRSE samples were scored as negative by all commercial tests but by only two out of three in-house tests.
Journal of Clinical Microbiology 09/2007; 45(8):2698-700. · 4.15 Impact Factor
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ABSTRACT: We compared multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and amplified fragment length polymorphism (AFLP) for typing of Staphylococcus aureus and show that the methods yield similar results, although with differences in resolving power and reproducibility. Epidemiological conditions should determine which is the optimal typing method to be used.
Journal of Microbiological Methods 06/2007; 69(2):371-5. · 2.09 Impact Factor
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Damian C Melles,
Debby Bogaert,
Raymond F J Gorkink,
Justine K Peeters,
Michael J Moorhouse,
Alewijn Ott, Willem B van Leeuwen,
Guus Simons,
Henri A Verbrugh,
Peter W M Hermans,
Alex van Belkum
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ABSTRACT: Bacterial interference between Staphylococcus aureus and Streptococcus pneumoniae in the nasopharynx has been observed during colonization, which might have important clinical implications for the widespread use of pneumococcal conjugate vaccine in young children. This study aimed to determine whether the capacity of Staph. aureus to compete with Strep. pneumoniae is dependent on bacterial genotype. Demographic and microbiological determinants of carriage of specific genotypes of Staph. aureus in children were also studied. Children (n=3198) were sampled in the nasopharynx to detect carriage of Staph. aureus, Strep. pneumoniae and Neisseria meningitidis. Staph. aureus genotypes and pneumococcal sero- and genotypes were determined. Age, gender, zip code, active smoking and co-colonization with N. meningitidis or Strep. pneumoniae, both vaccine- and non-vaccine types, were not associated with colonization by specific Staph. aureus genotypes. Based on the whole-genome typing data obtained, there was no obvious correlation between staphylococcal and pneumococcal genotypes during co-colonization. Passive smoking showed a significant association (P=0.003) with carriage of a specific Staph. aureus cluster. This study suggests that there are no major differences between Staph. aureus clones (with different disease-invoking potential) in their capacity to compete with Strep. pneumoniae subtypes. Further studies should demonstrate whether differences in bacterial interference are due to more subtle genetic changes.
Microbiology 04/2007; 153(Pt 3):686-92. · 3.06 Impact Factor
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Emerging infectious diseases 08/2006; 12(7):1174-5. · 6.17 Impact Factor
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ABSTRACT: The Lightcycler Staphylococcus kit is a diagnostic tool for direct real-time detection of Staphylococcus aureus in clinical materials. We show here that detection of S. aureus nasal carriage using this test is hampered by competition of DNA from coagulase-negative staphylococci. However the test is well suited for species identification after culture and the identification of high-load S. aureus carriers.
Journal of Microbiological Methods 06/2006; 65(2):354-6. · 2.09 Impact Factor
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ABSTRACT: The Staphylococcus aureus enterotoxin gene cluster, egc, was detected in isolates from healthy individuals and in those from patients with bacteremia. The egc genes cooccur and are slightly enriched in strains from healthy carriers (present in 63.7% of carriage-associated isolates versus 52.9% of invasive isolates; P = 0.03). Multilocus sequence typing revealed that successful staphylococcal clones usually harbor the egc locus.
Journal of Clinical Microbiology 05/2006; 44(4):1555-7. · 4.15 Impact Factor
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ABSTRACT: We screened 14,008 adult nonsurgical patients for Staphylococcus aureus nasal carriage at hospital admission and assessed them for invasive S. aureus disease and in-hospital mortality. Multilocus sequence typing was performed on endogenous invasive strains and nasal strains of matched asymptomatic carriers to investigate whether virulent clones could be identified in nasal carriers. Clonal complex (CC) 45 was significantly underrepresented (odds ratio [OR], 0.16 [95% confidence interval {CI}, 0.04-0.59]) and CC30 was overrepresented (not statistically significant) among invasive strains (OR, 1.91 [95% CI, 0.91-4.0]). The distribution of CCs of invasive S. aureus strains in noncarriers did not differ from that in carriers. Those infected with S. aureus strains belonging to a CC had higher mortality than those infected with strains not belonging to a CC (P<.05), which indicates the coevolution of S. aureus virulence and spread in humans.
The Journal of Infectious Diseases 10/2005; 192(7):1196-200. · 6.41 Impact Factor
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Willem B van Leeuwen,
Damian C Melles,
Alwaleed Alaidan,
Mohammed Al-Ahdal,
Hélène A M Boelens,
Susan V Snijders,
Heiman Wertheim,
Engeline van Duijkeren,
Justine K Peeters,
Peter J van der Spek,
Roy Gorkink,
Guus Simons,
Henri A Verbrugh,
Alex van Belkum
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ABSTRACT: Comparative genomics were used to assess genetic differences between Staphylococcus aureus strains derived from infected animals versus colonized or infected humans. A total of 77 veterinary isolates were genetically characterized by high-throughput amplified fragment length polymorphism (AFLP). Bacterial genotypes were introduced in a large AFLP database containing similar information for 1,056 human S. aureus strains. All S. aureus strains isolated from animals in close contact with humans (e.g., pet animals) were predominantly classified in one of the five main clusters of the AFLP database (cluster I). In essence, mastitis-associated strains from animals were categorized separately (cluster IVa) and cosegregated with bacteremia-associated strains from humans. Distribution of only 2 out of 10 different virulence genes differed across the clusters. The gene encoding the toxic shock syndrome protein (tst) was more often encountered among veterinary strains (P < 0.0001) and even more in the mastitis-related strains (P<0.0001) compared to human isolate results. The gene encoding the collagen binding protein (cna) was rarely detected among invasive human strains. The virulence potential, as indicated by the number of virulence genes per strain, did not differ significantly between the human- and animal-related strains. Our data show that invasive infections in pets and humans are usually due to S. aureus strains with the same genetic background. Mastitis-associated S. aureus isolated in diverse farm animal species form a distinct genetic cluster, characterized by an overrepresentation of the toxic shock syndrome toxin superantigen-encoding gene.
Journal of Bacteriology 08/2005; 187(13):4584-91. · 3.83 Impact Factor
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Damian C Melles,
Raymond F J Gorkink,
Hélène A M Boelens,
Susan V Snijders,
Justine K Peeters,
Michael J Moorhouse,
Peter J van der Spek, Willem B van Leeuwen,
Guus Simons,
Henri A Verbrugh,
Alex van Belkum
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ABSTRACT: The population structure of Staphylococcus aureus carried by healthy humans was determined using a large strain collection of nonclinical origin (n = 829). High-throughput amplified fragment length polymorphism (AFLP) analysis revealed 3 major and 2 minor genetic clusters of S. aureus, which were corroborated by multilocus sequence typing. Major AFLP cluster I comprised 44.4% of the carriage isolates and showed additional heterogeneity whereas major AFLP groups II and III presented 2 homogeneous clusters, including 47.3% of all carriage isolates. Coanalysis of invasive S. aureus strains and epidemic methicillin-resistant S. aureus (MRSA) revealed that all major clusters contained invasive and multiresistant isolates. However, clusters and subclusters with overrepresentation of invasive isolates were also identified. Bacteremia in elderly adults, for instance, was caused by a IVa cluster-derived strain significantly more often than by strains from other AFLP clusters. Furthermore, expansion of multiresistant clones or clones associated with skin disease (impetigo) was detected, which suggests that epidemic potential is present in pathogenic strains of S. aureus. In addition, the virulence gene encoding Panton-Valentine leukocidin was significantly enriched in S. aureus strains causing abscesses and arthritis in comparison with the carriage group. We provide evidence that essentially any S. aureus genotype carried by humans can transform into a life-threatening human pathogen but that certain clones are more virulent than others.
Journal of Clinical Investigation 01/2005; 114(12):1732-40. · 15.39 Impact Factor
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ABSTRACT: A newly developed oligonucleotide array suited for multilocus sequence typing (MLST) of Staphylococcus aureus strains was analyzed with two strain collections in a two-center study. MLST allele identification for the first strain collection fully agreed with conventional strain typing. Analysis of strains from the second collection revealed that chip-defined MLST was concordant with conventional MLST. Array-mediated MLST data were reproducible, exchangeable, and epidemiologically concordant.
Journal of Clinical Microbiology 08/2003; 41(7):3323-6. · 4.15 Impact Factor
