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Abstract: The purpose of this study was to quantify the biofilm formations of various methicillin-resistant Staphylococcus aureus (MRSA) clones (ST1, ST5, ST72, ST89, ST239, and ST254) and to evaluate the in vitro activities of antibiotics. Of 86 MRSA isolates tested, 44 isolates (51.2 %) formed biofilms, including 8 strong biofilm producers (7 isolates of ST72 and 1 isolate of ST89). The planktonic MICs, minimal bactericidal concentrations, and minimum biofilm eradication concentrations (MBECs) of 6 antibiotics (clindamycin, gentamicin, linezolid, vancomycin, daptomycin, and tigecycline) were measured for 8 MRSA isolates. The planktonic isolates were susceptible to all agents, with daptomycin being the most effective, followed by gentamicin and vancomycin. However, clindamycin, linezolid, and tigecycline showed bacteriostatic activity against most of the isolates. The biofilms were resistant to high concentrations of most drugs. However, the MBEC values of daptomycin and tigecycline were lower overall than that of other antibiotics. Microscopy studies verified that daptomycin was the most effective drug used in adhesive biofilms, while gentamicin and tigecycline exhibited some bactericidal efficacy. Our results demonstrated that ST72 and ST89 form strong biofilms that may cause problems in hospital setting, and daptomycin, gentamicin, and tigecycline may be choice therapeutics against biofilm-mediated S. aureus infections. [Copyright &y& Elsevier]

Abstract: The aim of this study was to investigate for the first time the prevalence and types of extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpC β-lactamase (PABL) in Enterobacteriaceae in Korean long-term care facilities (LTCFs). ESBL rates were 45.3% (72/159) in Escherichia coli and 42.7% (50/117) in Klebsiella pneumoniae. In E. coli, CTX-M-28, the most prevalent ESBLs, was identified for the first time in Korea in 44 isolates. In K. pneumoniae, SHV-12 was found in 27 isolates (52.9% of ESBLs), among which 25 isolates also contained SHV-11. Twenty-seven isolates had SHV and CTX-M β-lactamase simultaneously. PABL genes were detected in 39.3% (46/117) of K. pneumoniae and 3.1% (5/159) E. coli. In E. coli, DHA-1(3), CMY-2(1), and CMY-6(1) were detected, whereas in K. pneumoniae, only DHA-1 was detected. Among the PABL-producing organisms, 80.0% (E. coli) and 52.2% (K. pneumoniae) simultaneously produced ESBLs. In conclusion, LTCF residents in Korea have a very high prevalence of E. coli and K. pneumoniae producing ESBLs, PABLs, or both, and the genotypes of ESBL and PABL were identical with those found in general hospitals. [Copyright &y& Elsevier]

Abstract: A nationwide surveillance of the antimicrobial resistance of Pseudomonas aeruginosa isolates from non-tertiary care hospitals was conducted in Korea from 2002 to 2006. Resistance to almost all antimicrobial agents decreased significantly from 2003 (P < 0.01). Resistance rates to the major antipseudomonal agents, ceftazidime, imipenem, meropenem, and aztreonam, were 18.8%, 20.5%, 18.7%, and 19.7%, respectively, in 2003. However, they had all decreased to below 10% in 2006. The proportion of multidrug-resistant isolates that were resistant to at least 3 of 5 major antipseudomonal agent decreased from 33.5% in 2003 to 23.1% in 2006 (P < 0.05). In this study, we found a decreasing trend in resistance rates and low resistance rates in P. aeruginosa from non-tertiary care hospitals compared with those from general hospitals, including tertiary care hospitals, in Korea. Our data provide valuable information for the selection of reliable empiric therapies for P. aeruginosa infections in non-tertiary care hospital patients, including outpatients. [Copyright &y& Elsevier]