Changes in pneumococcal serotypes and antibiotypes carried by vaccinated and unvaccinated day-care centre attendees in Portugal, a country with widespread use of the seven-valent pneumococcal conjugate vaccine.

The seven-valent pneumococcal conjugate vaccine (PCV7) has been available in Portugal since June 2001, but is not included in the National Vaccination Plan. Its impact on colonization is unknown. A point-prevalence study to evaluate PCV7 usage was carried out in 2006 among day-care centre attendees from the Lisbon area. Pneumococcal carriage rates, serotypes, and antibiotypes were determined and compared with results from a similar study conducted in 2001 before vaccine approval. In 2001 and 2006, 717 and 571 children, respectively, were enrolled. In 2006, 45.9% of the participants were appropriately vaccinated and 11.5% were incompletely vaccinated. Carriage of pneumococci remained stable (64.9% in 2001; 68.7% in 2006). Vaccine types (VT) decreased from 53.1% of all pneumococci to 11.2% (p <0.001). Serotype replacement was observed among vaccinated and unvaccinated children. Non-vaccine types (NVT) 1, 6C, 7F, 15A, 16F, 21, 23A, 29, and non-typeable (NT) strains increased significantly; serotype 19A increased, but not significantly. Rates of resistance to penicillin, erythromycin, clindamycin and tetracycline remained stable (p >0.05) due to significant increases in intermediate resistance to penicillin (from 5.5% to 17.8%), erythromycin (from 9.2% to 21.8%), clindamycin (from 6.4% to 19.3%) and tetracycline (from 8.3% to 15.8%) among NVT. Whereas in 2001 resistance among NVT was mostly associated with serotype 19A and NT strains, in 2006 resistance was also found among serotypes 6C, 15A, 24F and 33F. In conclusion, dramatic shifts in serotypes of colonizing pneumococci were observed among vaccinated and unvaccinated children. Rates of antibiotic resistance remained unchanged due to a balance between reduction in VT and an increase in antimicrobial-resistant NVT.

Clonal types and multidrug resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) recovered in Italy during the 1990s.

A large number (272) of methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from Italian hospitals during the early and late 1990s were characterized for multidrug resistance pattern and clonal type using a combination of genotyping methods, including pulsed-field gel electrophoresis (PFGE), spaA typing, multilocus sequence typing (MLST), determination of SCC mec type, and hybridization pattern with Tn 554. The majority of MRSA belonged to four genetic lineages: the pandemic Iberian and Brazilian clones, and two unique clonal types-the "Italian" and "Rome" clones of MRSA. The Italian clone carried the SCC mec type I in the genetic background of ST228, which is a double-locus variant of the sequence type of the multidrug-resistant New York/Japanese clone (ST5). The properties of the Rome clone showed several striking similarities to those of the Archaic clone of MRSA that was dominant among MRSA isolates in the mid-1960s to 1970s, but has not been detected since then in recent global surveillance studies.

Two international methicillin-resistant Staphylococcus aureus clones endemic in a university hospital in Patras, Greece.

Pulsed-field gel electrophoresis (PFGE) of SmaI macrofragments and hybridization of ClaI digests with the mecA- and Tn554-specific DNA probes were used to define the endemic clones of methicillin-resistant Staphylococcus aureus (MRSA) among strains collected in 1993 and 1998 to 2000 at the University Hospital of Patras, Patras, Greece. Representatives of each clonal type were analyzed by spaA typing, multilocus sequence typing (MLST), and staphylococcal chromosomal cassette mec (SCCmec) typing. The results indicated the existence of two successive international MRSA clones: (i) a clonal type with PFGE type A, sequence type (ST) 30 (ST30), and SCCmec type IV, which was very similar to a clone widely spread in the United Kingdom, Mexico, and Finland, and (ii) a clonal type with PFGE type B, ST239, and SCCmec III, which was related to the Brazilian clone. Both clones seem to be widespread in Greece as well. A novel MRSA clone is also described and is characterized by a new MLST type (ST80) associated with SCCmec type IV and with the presence of Panton-Valentine leukocidin genes.

Frequent recovery of a single clonal type of multidrug-resistant Staphylococcus aureus from patients in two hospitals in Taiwan and China.

One hundred thirty-two methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from patients with S. aureus infections between January 1998 and February 1999 in two hospitals, one located in Taipei, Taiwan, and another in Nanjing, People's Republic of China, were examined for antibiotic susceptibility and for clonal type by a combination of three methods: hybridization of ClaI restriction digests with mecA- and Tn554-specific DNA probes and pulsed-field gel electrophoresis of chromosomal SmaI digests. Selected isolates representing each clonal type were also analyzed by spaA typing, multilocus sequence typing, and a multiplex PCR method capable of identifying the structural type of the staphylococcal cassette chromosome mec (SCCmec) carried by the bacteria. The overwhelming majority of isolates (126 of 132 or 95%) belonged to minor variants of a single clonal type resembling the Brazilian and Hungarian epidemic MRSA clones, which showed a common spaA type and which were either sequence type 239 (ST239) or ST241 (a single-locus variant of ST239) in association with SCCmec type III or IIIA.

The evolution of methicillin resistance in Staphylococcus aureus: similarity of genetic backgrounds in historically early methicillin-susceptible and -resistant isolates and contemporary epidemic clones.

The key genetic component of methicillin resistance, the mecA determinant, is not native to Staphylococcus aureus. Thus, the evolution of methicillin-resistant S. aureus (MRSA) must have begun with the acquisition of the mecA determinant from an unknown heterologous source some time before the first reported appearance of MRSA isolates in clinical specimens in the U.K. and Denmark (in the early 1960s). We compared the genetic backgrounds and phenotypes of a group of methicillin-susceptible S. aureus (MSSA) isolates to the properties of MRSA strains isolated in Denmark and the U.K. during the same time period, and also to the genetic profiles of contemporary epidemic clones of MRSA. All early MRSA isolates resembled a large group of the early MSSA blood isolates in phenotypic and genetic properties, including phage group, antibiotype (resistance to penicillin, streptomycin, and tetracycline), pulsed-field gel electrophoresis pattern, and spaA type and multilocus sequence type, strongly suggesting that the early MSSA examined here represented the progeny of a strain that served as one of the first S. aureus recipients of the methicillin-resistance determinant in Europe. The genetic background of this group of early MSSA isolates was also very similar to that of the widely disseminated contemporary "Iberian clone" of MRSA, suggesting that genetic determinants present in early MSSA and essential for some aspects of the epidemicity and/or virulence of these strains may have been retained by this highly successful contemporary MRSA lineage.