Christel Driessen

The population structure of Staphylococcus aureus among general practice patients from The Netherlands

To investigate the prevalence, the antibiotic resistance pattern and the population structure of Staphylococcus aureus, S. aureus isolates from the anterior nostrils of patients of general practitioners (GPs) were analysed. Insight into the S. aureus population structure is essential, as nasal carriers of S. aureus are at increased risk of developing an S. aureus infection. S. aureus was isolated from nasal swabs from 2691 patients with no sign of an infection collected in 29 GP practices in The Netherlands. The susceptibility pattern for several classes of antibiotics was determined, as well as the S. aureus genetic background, using spa typing. S. aureus was isolated from 617 of the 2691 (23%) nasal swabs. The prevalences of resistance to ciprofloxacin, co-trimoxazole, fusidic acid, macrolides and mupirocin were 0.2%, 0%, 6%, 5% and 1%, respectively. Half of the isolates were associated with a genetic background common to the major methicillin-resistant S. aureus (MRSA) clones, e.g. clonal complex (CC)1, CC5, CC8, CC22, CC30 and CC45, and the remainder were mainly associated with CC7, CC12, CC15, CC26, CC51 and CC101. The low prevalences of resistance suggest that, in the Dutch situation, S. aureus isolates from patients visiting their GP because of complaints not related to infection do not represent a large reservoir of antibiotic resistance genes. Although no MRSA isolates were found, the genetic background of some of the S. aureus isolates is commonly observed among community-associated (CA)-MRSA clones (CC1, CC8 and CC30), and this might suggest that these isolates have the potential to become CA-MRSA.

Different Clonal Complexes of Methicillin-Resistant Staphylococcus aureus Are Disseminated in the Euregio Meuse-Rhine Region

ABSTRACT The Euregio Meuse-Rhine (EMR) is formed by the border regions of Belgium, Germany, and The Netherlands. Cross-border health care requires infection control measures, in particular since the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) differs among the three countries. To investigate the dissemination of MRSA in the EMR, 152 MRSA isolates were characterized by pulsed-field gel electrophoresis (PFGE), SCCmec typing, and multilocus sequence typing. PFGE revealed major clonal groups A, G, L, and Q, suggesting dissemination of MRSA in the EMR. Group A harbored mainly SCCmec type III and sequence types (STs) 239 and 241. The majority of the strains from group G harbored SCCmec type I and ST8 and ST247, whereas most strains from group L carried either SCCmec type IV or type I. Within group L, ST8 and ST228 were found, belonging to clonal complexes 8 and 5, respectively. Most strains from group Q included SCCmec type II and were sequence typed as ST225. Both ST225-MRSA-II and ST241-MRSA-III were novel findings in Germany. In addition, the SCCmec type of two isolates has not been described previously. One strain was classified as SCCmec type III but harbored the pls gene and the dcs region. Another strain was characterized as SCCmec type IV but lacked the dcs region. In addition, one isolate harbored both SCCmec type V and Panton-Valentine leukocidin. Finally, the SCCmec type of the strains was found to be correlated with the antibiotic susceptibility pattern.

Cross-border dissemination of methicillin-resistant Staphylococcus aureus, Euregio Meuse-Rhin region

MRSA clones were associated with hospital-associated clonal complexes and with Panton-Valentine leukocidin–positive community-associated MRSA.

Different Levels of Genetic Homogeneity in Vancomycin-Resistant and -Susceptible Enterococcus faecium Isolates from Different Human and Animal Sources Analyzed by Amplified-Fragment Length Polymorphism

ABSTRACT The genetic relationship among fecal vancomycin-resistant Enterococcus faecium (VREF) and vancomycin-susceptible E. faecium (VSEF) isolates (n = 178) from the same populations of pigs, human healthy volunteers, and hospitalized patients (from The Netherlands) and chickens (from The Netherlands and Greece) was studied by amplified-fragment length polymorphism (AFLP). The majority of VREF isolates from pigs, healthy volunteers, and hospitalized patients grouped together (genetic similarity, ≥65%). In a previous AFLP study by our group the VREF isolates from hospitalized patients grouped separately, most likely because these were clinical and not fecal isolates as in the present study. Furthermore, VSEF isolates from humans and pigs were found much more genetically diverse than VREF isolates, whereas VREF and VSEF isolates from chickens clustered together in a separate genogroup (genetic similarity, ≥65%), a pattern clearly distinct from the patterns for human and pig isolates. The present study suggests that pigs are a more important source of VREF for humans than chickens and that human- and pig-derived VSEF isolates seem much more heterogeneous than VREF isolates.

Molecular typing of methicillin-susceptible Staphylococcus aureus isolates collected in the Yogyakarta area in Indonesia, 2006

The characterization of 62 community-associated methicillin-sensitive Staphylococcus aureus (MSSA) isolates from 440 individuals in the Yogyakarta area of Indonesia in 2006 showed that: (i) almost half of the isolates were associated with methicillin-resistant S. aureus lineages [clonal complex (CC)1, CC8 and CC45] and (ii) ten Panton-Valentine leukocidin-positive isolates were associated with CC1 (n = 7), CC30 (n = 1) and CC51 (n = 2). The high Panton-Valentine leukocidin prevalence (16%) among S. aureus is of concern because these strains can cause severe infections and the introduction of staphylococcal cassette chromosome mec into virulent and epidemic MSSA could pose a serious public health threat.

Staphylococcus aureus carriage among GPs in the Netherlands

BACKGROUND The extent to which GPs serve as a reservoir for antibiotic-resistant Staphylococcus aureus is unknown and not well studied. AIM To determine the prevalence of nasal S. aureus carriage among GPs in the Netherlands, as well as the antimicrobial resistance and the genotypes of isolated S. aureus. DESIGN OF STUDY Observational, point-prevalence, and cross-sectional study. SETTING GPs attending the annual conference of the Dutch College of General Practitioners in 2006. METHOD Nasal swabs were randomly taken from 395 GPs and analysed for the presence of S. aureus. Antimicrobial susceptibility was determined by a microbroth dilution method and the genotypes by spa typing, which was associated with multilocus sequence typing. RESULTS Of the GPs, 129/395 (33%; 95% confidence interval [CI] = 28 to 37%) were carriers of S. aureus. No meticillin-resistant S. aureus (MRSA) was found. Resistance was observed to penicillin (71%; 95% CI = 63 to 79%), fusidic acid (7%; 95% CI = 3 to 13%), and clarithromycin (6%; 95% CI = 3 to 12%). In 72% of the isolates, an MRSA-related genotype of S. aureus was found. CONCLUSION The low antibiotic resistance found among S. aureus of GPs suggests that GPs are not a reservoir of antibiotic-resistant S. aureus strains. The relatively high resistance to fusidic acid, which has not previously been described in the Netherlands and is mostly because of antibiotic use, suggests that patients infect GPs and not the other way round. GPs may be at risk for nasal carriage of S. aureus with an MRSA-related genotype.

Prevalence and spread of multidrug-resistant Escherichia coli including ST131 in different patient populations in the Euroregion Meuse-Rhine.

AIM To investigate the prevalence and genetic background of Escherichia coli collected from different patient populations in the Euroregion Meuse-Rhine. MATERIALS & METHODS Susceptibility testing was performed on 1651 E. coli isolates with broth microdilution. Their genetic background was determined using pulsed-field gel electrophoresis and multilocus sequence typing. RESULTS The prevalence of resistance varied significantly between the populations. Approximately 10% of the E. coli isolates were multidrug-resistant and/or a β-lactamase producer. The most prevalent extended-spectrum β-lactamase type was CTX-M-15 and ST131 was the most prevalent multilocus sequence typing type. RESULTS from pulsed-field gel electrophoresis of the ST131 isolates indicate the spread of these isolates in the Euroregion. CONCLUSION E. coli ST131 was the most prevalent sequence type in our Euroregional study. It is essential to control the spread of these resistant strains (e.g., with infection-control policies, antibiotic stewardship programs and antibiotic resistance surveillance). In this way we could observe shifts in the prevalence of resistance of the E. coli population and act accordingly.