ABSTRACT
Limited use of linezolid for treating methicillin-resistant Staphylococcus aureus (MRSA) infection was approved in Japan in 2006. We report here the status of linezolid-resistant MRSAs in Japan. Eleven linezolid-resistant clinical isolates from 11 patients at six hospitals were collected from 2006 through 2008. The minimal inhibitory concentration (MIC) of linezolid in these strains varied from 8 to 64 µg/ml. All strains had at least one G2576T mutation in the chromosomal gene(s) encoding domain V of the 23S ribosomal RNA (rRNA). Chromosomal DNA encoding five copies of the domain V region was analyzed by polymerase chain reaction (PCR). Strains with the linezolid MICs of 64, 32, 16, and 8 µg/ml had the G2576T mutation(s) in four, three (or four), two, and one copy of the 23S rRNA genes, respectively. These results suggest that the level of linezolid resistance seems to be roughly correlated with the number of mutations in the genes encoding 23S rRNA. DNA samples from all 11 strains were subjected to pulsed-field gel electrophoresis and were classified into seven independent clones having >92% identity. Among the 11 patients, five had been treated with linezolid and the remainder, in two hospitals, had no history of prior linezolid use. The results suggested possible nosocomial infections by linezolid-resistant MRSA.
Subject(s)
Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial , Linezolid/pharmacology , Staphylococcal Infections , Staphylococcus aureus/isolation & purification , DNA, Bacterial/genetics , Genome, Bacterial , Humans , Japan , RNA, Ribosomal, 23S/genetics , Staphylococcal Infections/drug therapy , Staphylococcus aureus/genetics , Time FactorsABSTRACT
We investigated the molecular characteristics of ESBL-producing Escherichia coli in Japan. A total of 101 clinical isolates of ESBL-positive E. coli collected in Japan between June 2008 and November 2009 were studied. Among the 101 strains, 97 were positive for CTX-M, while 47 and two were positive for TEM and SHV, respectively. Sequencing revealed that CTX-M-14 was most common (49/101), followed by CTX-M-27 (22/101) and CTX-M-15 (8/101). Based on MLST data, seven of eight CTX-M-15 producers belonged to ST131. This is the first report about clinical isolates of E. coli ST131 possessing CTX-M-15 in Japan.
Subject(s)
Escherichia coli/classification , Escherichia coli/enzymology , beta-Lactamases/metabolism , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Cluster Analysis , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Escherichia coli/genetics , Escherichia coli/isolation & purification , Escherichia coli Infections/epidemiology , Escherichia coli Infections/microbiology , Female , Genotype , Humans , Infant , Japan/epidemiology , Male , Middle Aged , Molecular Epidemiology , Multilocus Sequence Typing , Sequence Analysis, DNA , Young Adult , beta-Lactamases/geneticsABSTRACT
Limited use of linezolid for treating methicillin-resistant Staphylococcus aureus (MRSA) infection was approved in Japan in 2006. We report here the status of linezolid-resistant MRSAs in Japan. Eleven linezolid-resistant clinical isolates from 11 patients at six hospitals were collected from 2006 through 2008. The minimal inhibitory concentration (MIC) of linezolid in these strains varied from 8 to 64 µg/ml. All strains had at least one G2576T mutation in the chromosomal gene(s) encoding domain V of the 23S ribosomal RNA (rRNA). Chromosomal DNA encoding five copies of the domain V region was analyzed by polymerase chain reaction (PCR). Strains with the linezolid MICs of 64, 32, 16, and 8 µg/ml had the G2576T mutation(s) in four, three (or four), two, and one copy of the 23S rRNA genes, respectively. These results suggest that the level of linezolid resistance seems to be roughly correlated with the number of mutations in the genes encoding 23S rRNA. DNA samples from all 11 strains were subjected to pulsed-field gel electrophoresis and were classified into seven independent clones having >92% identity. Among the 11 patients, five had been treated with linezolid and the remainder, in two hospitals, had no history of prior linezolid use. The results suggested possible nosocomial infections by linezolid-resistant MRSA.
