Antimicrobial susceptibility and molecular typing of MRSA in cystic fibrosis.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in cystic fibrosis (CF) patients in the United States is approximately 25%. Little is known about the relative proportion of hospital- versus community-associated strains or the antimicrobial susceptibility of MRSA in different CF centers. We hypothesized that the majority of MRSA isolates obtained from children with CF are those endemic in the hospital and that those associated with community acquisition (SCCmec IV) would be more resistant than typically seen in non-CF MRSA isolates. We studied MRSA strains from seven pediatric CF centers to determine the clonal distribution based on DNA sequencing of the staphylococcal protein A gene (spa typing), the type of staphylococcal chromosomal cassette mec (SCCmec), and the proportion of strains with Panton-Valentine leukocidin (PVL). Antimicrobial susceptibility to systemic and topical antibiotics was compared between different MRSA types. We analyzed 277 MRSA isolates from unique patients (mean age 11.15 ± 4.77 years, 55% male). Seventy % of isolates were SCCmec II PVL negative and the remainder SCCmec IV. Overall 17% MRSA strains were PVL positive (all SCCmec IV). Spa typing of 118 isolates showed most of the SCCmec II strains being t002, while SCCmec IV PVL positive isolates were t008, and SCCmec IV PVL negative isolates represented a variety of spa-types. The proportions of SCCmec II strains and spa-types were similar among centers. Overall rates of resistance to trimethoprim-sulfamethoxazole (4%), tetracycline (7%), tigecycline (0.4%), linezolid (0.4%) as well as fosfomycin (0.4%), fusidic acid (3%), and mupirocin (1%) were low. No strains were resistant to vancomycin. SCCmec II strains had higher rates of resistance to ciprofloxacin and clindamycin (P < 0.001) than SCCmec IV strains. In this U.S. study, most MRSA isolates in the pediatric CF population were SCCmec II PVL negative. Rates of resistance were low, including to older and orally available antibiotics such as trimethoprim-sulfamethoxazole.

Champion EA ，Miller MB ，Popowitch EB ，Hobbs MM ，Saiman L ，Muhlebach MS ，STAR-CF Study Team ... -  《-》

Molecular characterization and antibiotic resistance of clinical isolates of methicillin-resistant Staphylococcus aureus obtained from Southeast of Iran (Kerman).

Staphylococcus aureus infections, particularly infections caused by methicillin-resistant S. aureus (MRSA) strains, are emerging as a major public health problem. The aim of this study was to determine the prevalence of MRSA, antibiotic resistance profile and staphylococcal cassette chromosome mec (SCCmec) type of MRSA isolates obtained from clinical samples. Totally, 162 S. aureus isolates were obtained from clinical samples at three university hospitals in Kerman, Iran from March 2011 to February 2012. All isolates were identified as S. aureus by phenotypic methods and confirmed by PCR amplification of the nuc gene. MRSA isolates were screened by phenotypic tests and confirmed by presence of mecA gene. The minimum inhibitory concentrations (MICs) of the MRSA isolates against antibacterial agents were determined by E-test. All isolates were analyzed by PCR for the presence of mecA and pvl genes. SCCmec typing of MRSA isolates was performed by multiplex PCR assay. Strain typing was carried out with REP-PCR. Using mecA gene PCR and phenotypic methods, 56.8% of the isolates were identified as MRSA. All MRSA isolates were susceptible to vancomycin and linezolid. The sensitivity of MRSA isolates to trimethoprim-sulfamethoxazole, clindamycin, ciprofloxacin, gentamicin, and erythromycin was 70.66, 66.53, 42.4, 38.05, and 29.35%, respectively. The most frequent SCCmec types were type III (48.31%) followed by type V (19.1%), type I (16.85%), and type IV (3.37%). The pvl gene was detected in 3.08% of isolates (two MRSA and three MSSA isolates). REP-PCR typing divided the 92 MRSA isolates into 10 distinct clusters. Our results indicate that vancomycin and linezolid are the most effective antibacterial agents against MRSA isolates and SCCmec type III is predominant in MRSA strains in this area.

Sadeghi J ，Mansouri S 《-》

Multicenter Observational Study on Factors and Outcomes Associated with Various Methicillin-Resistant Staphylococcus aureus Types in Children with Cystic Fibrosis.

Muhlebach MS ，Heltshe SL ，Popowitch EB ，Miller MB ，Thompson V ，Kloster M ，Ferkol T ，Hoover WC ，Schechter MS ，Saiman L ，STAR-CF Study Team ... -  《-》

[Epidemiological and molecular characteristics of hospital-acquired methicillin-resistant Staphylococcus aureus strains isolated in Hacettepe University Adult Hospital in 2004-2005].

Akoğlu H ，Zarakolu P ，Altun B ，Ünal S ... -  《MIKROBIYOLOJI BULTENI》

Antimicrobial susceptibility patterns and staphylococcal cassette chromosome mec types of, as well as Panton-Valentine leukocidin occurrence among, methicillin-resistant Staphylococcus aureus isolates from children and adults in middle Tennessee.

Kilic A ，Li H ，Stratton CW ，Tang YW ... -  《-》