Clonal Structure of the Methicillin-ResistantStaphylococcus aureus(MRSA) Population in Poland: Revision and Update

Emergence and spread of worldwide Staphylococcus aureus clones among cystic fibrosis patients

Background

The aim of this study was to assess the relatedness of molecular types of Staphylococcus aureus isolates colonizing cystic fibrosis (CF) patients with their antimicrobial resistance and prevalence of toxin genes.

Methods

A total of 215 isolates from the airways of 107 patients with CF were tested for spa and SCCmec type, antimicrobial resistance and carriage of toxin genes.

Results

t015, t084, t091, t700 and t002 were the largest group (approximately 25%) among all 69 identified spa types. Five new spa types, t14286, t14287, t14288, t14289 and t14290, were identified and registered. Isolates from CF patients were clustered into 11 multi-locus sequence typing clonal complexes, with CC30, CC22, CC97, CC45, CC15 and CC5 being the most frequent ones. Twelve (5.6%) methicillin-resistant S. aureus (MRSA) isolates and 102 (47.7%) multidrug-resistant isolates were identified, along with three SCCmec types (I, III and V). All isolates (both MRSA and methicillin-sensitive S. aureus) were Panton–Valentine leucocidin-negative, and 56.7% harbored egc genes. This was the first study documenting the presence of ST398-V-t571 livestock-associated MRSA in a European patient with CF.

Conclusion

These findings imply that individuals with CF can also be colonized with animal-related ST398 MRSA, and justify constant monitoring of staphylococcal colonization and identification of epidemic S. aureus clones in this group.

Staphylococcal chromosomal cassettes mec (SCCmec): A mobile genetic element in methicillin-resistant Staphylococcus aureus

Considered to be a potential "superbug", methicillin-resistant Staphylococcus aureus (MRSA) has been one of the major recent infectious pathogens and thus poses a challenge to hospital infection control. The mobile genetic element staphylococcal chromosomal cassette mec (SCCmec) carries both the mecA or mecC gene, encoding for a novel specific penicillin-binding protein (PBP2a), and site-specific recombinase genes ccrAB or/and ccrC. In MRSA, the acquisition of SCCmec leads to the resistance to the β-lactam antibiotics. As SCCmec plays a core role in the antimicrobial resistance characteristics, molecular epidemiology and evolution of MRSA, a thorough summary and comprehensive understanding of the prevalence and structural characteristics of SCCmec may aid in global surveillance, implementation and investigation on MRSA isolates, as well as further development of preventive and therapeutic approaches. Consequently, this review is aimed at describing the history, prevalence, types and subtypes, and current typing methods of SCCmec, with the focus on the typical structures of the SCCmec cassette.

Clinical isolates of Staphylococcus aureus from the Arkhangelsk region, Russia: antimicrobial susceptibility, molecular epidemiology, and distribution of Panton-Valentine leukocidin genes

A total of 91 consecutive clinical isolates of Staphylococcus aureus were collected at the Regional Hospital of Arkhangelsk, Russia, from May to December 2004, and examined for antimicrobial susceptibility, methicillin resistance and presence of Panton-Valentine leucocidin (PVL) genes. Epidemiological typing was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Methicillin-resistant S. aureus (MRSA) isolates were examined by staphylococcal cassette chromosome mec (SCCmec) typing. High-to-moderate rates of resistance to penicillin (beta-lactamase production; 93%), tetracycline (40%), erythromycin and clindamycin (32%) were observed. Forty out of ninety-one (44%) isolates were positive for PVL genes. Thirty-six (40%) PVL-positive methicillin-susceptible S. aureus (MSSA) strains were shown by PFGE and MLST typing (ST121, ST681, ST837) to be part of a nosocomial outbreak caused by clonal complex (CC) 121. PFGE, MLST and SCCmec typing revealed three MRSA clones. Sequence type (ST) 239-III (n=11), ST1097-III (n=1) and ST8-IV (n=3) belong to CC8 of epidemic multiresistant MRSA, whereas ST426-MRSA-IV/CC395 (n=1) has not been reported previously. All MRSA strains were PVL negative. The overall results underline the necessity of microbiological sampling, antimicrobial susceptibility testing, and epidemiological typing as a rational basis for antimicrobial treatment of S. aureus infections, and infection control measures to limit the spread of multiresistant MRSA and epidemic MSSA clones.

Countrywide molecular survey of methicillin-resistant Staphylococcus aureus strains in Poland

The present investigation was undertaken to assess the proportion of methicillin-resistant Staphylococcus aureus (MRSA) strains among hospital-acquired isolates and to determine the clones of MRSA currently circulating in Poland by using a number of molecular techniques. Between January and May 2005, methicillin resistance was investigated among a total of 915 S. aureus isolates collected from 39 hospitals. A total of 208 (22.7%) isolates were positive for the mecA gene by PCR. The molecular characterization of MRSA isolates was carried out by the multiple-locus variable-number tandem repeat fingerprinting, pulsed-field gel electrophoresis, multilocus sequence typing, and staphylococcal chromosomal cassette mec (SCCmec) typing methods. The Hungarian (PFGE B; ST239, SCCmec type III [ST239-III]), Iberian (ST247-I), and Berlin (ST45-IV) clones were predominant, representing approximately 52.9, 11.5, and 10.0% of the MRSA isolates, respectively. A decline in the proportion of earlier MRSA clones, such as ST5-IV (a Pediatric clone), ST80-IV) (a Mediterranean clone), ST239-III (a Polish and Brazilian clone), and ST30-IV (a southwest Pacific clone) was observed. Additionally, the emergence of an MRSA clone with SCCmec type V, possibly representing a community-acquired strain, was observed in two hospitals during this study.

Usefulness of multiple-locus VNTR fingerprinting in detection of clonality of community- and hospital-acquired Staphylococcus aureus isolates

Staphylococcus aureus has become a major source of hospital infections and the risk of colonisation and infection by community-acquired methicillin-resistant S. aureus (CA-MRSA) is increasingly higher. Because of the importance of S. aureus to public health, many molecular typing methods have been developed to determine its transmission routes and source of infection during epidemiological investigations. In this study we evaluated the usefulness of multiplex PCR based Multi-Locus VNTR Fingerprinting (MLVF) as the first step method for rapid differentiation of Croatian and Polish S. aureus isolates in hospital and community settings. This is a first report of the usefulness of MLVF in typing of hospital-acquired methicillin-sensitive S. aureus (HA-MSSA) and four CA-MRSA isolates. A total of 47 isolates of S. aureus recovered in Croatia in 2004 and in Poland in 2006 and 2007 were tested. The MLVF results were compared to those produced by other typing methods, such as Pulsed-Field Gel Electrophoresis (PFGE), Multi-Locus Sequence Typing (MLST) and spa typing. The MLVF analysis showed almost the same clonality results as the remaining typing methods although some differences were found. Epidemiological data about the relation among S. aureus isolates and the results produced by typing methods applied in the present study indicate that because of the advantages in ease and speed of Variable Number of Tandem Repeats (VNTR) procedure over PFGE, spa typing and MLST, MLVF can be used as a first screening method followed by additional typing.

Emergence in Brazil of methicillin-resistant Staphylococcus aureus isolates carrying SCCmecIV that are related genetically to the USA800 clone

An increasing incidence of nosocomial infections caused by non-multiresistant methicillin-resistant Staphylococcus aureus (nMMRSA) has been reported worldwide. The present study genotyped nMMRSA isolates obtained from hospitals in two cities in Brazil. The hospital isolates displayed pulsed-field gel electrophoresis (PFGE) patterns that were similar to those of the USA100 (ST5-SCCmecII) and USA 800 (ST5-SCCmecIV) strains, which are related to the New York/Japan and paediatric clones, respectively. Carriage of SCCmecIV and the classification by multilocus sequence typing (MLST) of a representative of this PFGE pattern in clonal complex 5 (CC5) confirmed the genetic relationship of the Brazilian isolates with USA800. The USA800-related Brazilian isolates were responsible for severe nosocomial infections in compromised adults and elderly patients in Brazil. A higher growth rate, an ability to form biofilm on inert polystyrene surfaces and the presence of the egc locus may have contributed, at least in part, to the fitness of these organisms as global nosocomial pathogens.

Replacement of methicillin-resistant Staphylococcus aureus clones in Hungary over time: a 10-year surveillance study

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Hungary has been increasing and is now close to 20% among invasive isolates of S. aureus. In order to understand the evolution of MRSA in Hungary, two collections of isolates were studied: 22 representatives of a collection of 238 MRSA isolates recovered between 1994 and 1998, and a collection of 299 MRSA isolates recovered between 2001 and 2004. The isolates were first characterised by pulsed-field gel electrophoresis (PFGE) and were distributed into 19 different PFGE patterns. Representatives of each pattern were further characterised by spa typing, multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) typing. The Hungarian clone that was predominant in 1994-1998 (PFGE E, ST239-III) had almost disappeared in 2003-2004, being replaced by the Southern German clone (PFGE B, ST228-I) and the New York/Japan epidemic clone (PFGE A, ST5-II), which represented c. 85% of the 2001-2004 isolates. Thus, this study describes, for the first time, the co-dominance and extensive spread of the New York/Japan clone in a European country.

Spread of a single multiresistant methicillin-resistant Staphylococcus aureus clone carrying a variant of staphylococcal cassette chromosome mec type III isolated in a university hospital

The purpose of the study was the molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolates cultured from patients treated in seven wards of a university hospital in Lublin, Poland, over a 14-month period. Eleven nosocomial MRSA isolates were analyzed. Phenotypic identification of the isolates as MRSA was confirmed by the detection of the nuc and mecA genes using a multiplex PCR assay. The MRSA isolates were further characterized by pulsed-field gel electrophoresis, 16S-23S rRNA spacer length polymorphism analysis, and the simplex and multiplex SCCmec PCR assays. The MRSA isolates were found to be multiresistant: in addition to resistance to beta-lactam agents, they demonstrated resistance to ciprofloxacin, tetracycline, erythromycin, and gentamicin. The MRSA isolates were genetically identical and shared common pulsed-field gel electrophoresis profiles and 16S-23S rRNA spacer length polymorphism profiles. The PCR-based method revealed that the profile of the Lublin clone was identical to that of the Brazilian pandemic MRSA isolates. By SCCmec typing, all MRSA isolates harbored the C variant of the SCCmec type III that differed from the typical SCCmec type III pattern by the lack of locus F (414 bp). The results of this study indicate the spread of a single, multiresistant, MRSA clone in various wards of a university hospital over a 14-month period. The SCCmec structure harbored by the Lublin clone has previously been identified among Polish MRSA isolates representing the HoMRSA-Pol1 clone. The data from this study indicate that the Lublin MRSA clone is most probably genetically related to the HoMRSA-Pol1 clone. Moreover, this latter clone belongs to ST239, the same sequence type as the Hungarian and Brazilian pandemic MRSA isolates.

Characteristics of Staphylococcus aureus strains isolated in Poland in 1996 to 2004 that were deficient in species-specific proteins

One hundred seventy Staphylococcus aureus isolates, collected in 1996 to 2004, were reidentified by phenotypic and genotypic methods. One hundred ten of these (65%) were confirmed, as previously denoted, to be clumping factor (CF)- or free coagulase-deficient S. aureus, based on their phenotype. Based on the CF or coagulase production, three groups of phenotypically deficient S. aureus isolates were distinguished. Group 1 encompassed CF-positive and coagulase-deficient isolates, group 2 consisted of CF-deficient and coagulase-positive isolates, and group 3 included isolates that were CF positive, had delayed coagulase activity, and were deficient in other species-specific features. All investigated strains harbored the clfA, clfB, coa, spa, and nuc genes, but the presence of their products was not detected by the phenotypic methods. Glycopeptide susceptibility testing showed that 26 isolates (23.6%) were hetero-glycopeptide-intermediate S. aureus(hGISA) or hetero-teicoplanin-intermediate S. aureus (hTISA), based on the population analysis profile. The relatedness of the isolates was evaluated by multiple-locus variable number of tandem repeats analysis, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing. The phenotypically deficient S. aureus isolates were classified into PFGE types B (ST239-III) and D (ST246-IA) and were related to the common clones, Hungarian and Iberian, respectively, which have been widely disseminated in Poland and globally. The simultaneous occurrence of hGISA/hTISA and the CF-deficient phenotypes was found for 62.1% of isolates belonging to group 2. The majority of these isolates were assigned to the Iberian clone (PFGE type D; ST247-IA). An association between the defect in coagulase and that in thermonuclease production was observed, which concerned 59.2% of isolates of group 1. The majority of these isolates belonged to the Hungarian clone (PFGE type B; ST239-III).

Distribution of the serine-aspartate repeat protein-encoding sdr genes among nasal-carriage and invasive Staphylococcus aureus strains

The sdr locus was found in all 497 investigated Staphylococcus aureus strains, although in 29 strains it contained only the sdrC gene (sdrD negative, sdrE negative). The sdrC-positive, sdrD-negative, sdrE-negative gene profile was exclusive to methicillin-sensitive S. aureus (MSSA) strains (Fisher's exact test; P = 0.0005) and was not found in the strains collected from bone infections (P = 0.0019). We also found a strong association between the presence of the sdrD gene and methicillin-resistant S. aureus strains (P < 0.0001). Our findings suggest that MSSA strains with the newly uncovered sdrC-positive, sdrD-negative, sdrE-negative gene profile have a substantially decreased potential to establish bone infection.