Emergence of methicillin-resistant coagulase-negative staphylococci resistant to linezolid with rRNA gene C2190T and G2603T mutations.

The aim of this article were to determinate the mechanism of linezolid resistance in coagulase-negative methicillin-resistant staphylococci from hospitals in the northeast of Brazil. We identified the isolates using VITEK(®) 2 and MALDI-TOF. Susceptibility to antibiotics was measured by the disk-diffusion method and by Etest(®) . Extraction of the whole genome DNA was performed, followed by screening of all the strains for the presence of mecA and cfr genes. The domain V region of 23S rRNA gene was sequenced and then aligned with a linezolid-susceptible reference strain. Pulsed-field gel electrophoresis (PFGE) macro-restriction analysis was performed. Three linezolid-resistant Staphylococcus hominis and two linezolid-resistant Staphylococcus epidermidis strains were analyzed. The isolates showed two point mutations in the V region of the 23S rRNA gene (C2190T and G2603T). We did not detect the cfr gene in any isolate by PCR. The S. hominis showed the same pulsotype, while the S. epidermidis did not present any genetic relation to each other. In conclusion, this study revealed three S. hominis and two S. epidermidis strains with resistance to linezolid due to a double mutation (C2190T and G2603T) in the domain V of the 23S rRNA gene. For the first time, the mutation of C2190T in S. epidermidis is described. This study also revealed the clonal spread of a S. hominis pulsotype between three public hospitals in the city of Natal, Brazil. These findings highlight the importance of continued vigilance of linezolid resistance in staphylococci.

Cidral TA ，Carvalho MC ，Figueiredo AM ，de Melo MC ... -  《-》

Linezolid-resistant Staphylococcus haemolyticus and Staphylococcus hominis: single and double mutations at the domain V of 23S rRNA among isolates from a Rio de Janeiro hospital.

In this work, the molecular and phenotypic antimicrobial resistance and clonal diversity of 10 linezolid-resistant Staphylococcus spp. isolates were investigated. The 7 Staphylococcus haemolyticus isolates presented Staphylococcal cassete chromosome mec (SCCmec) V and belonged to the same pulsed-field gel electrophoresis pulsotype. Their MICs for oxacillin, vancomycin, and linezolid were ≥ 256 μg/mL, 1-4 μg/mL, and 8-16 μg/mL, respectively. The 3 S. hominis presented MIC values 32 to >256 μg/mL, 2-4 μg/mL, and 12-24 μg/mL, and all carried the nontypeable SCCmec (ccr1 + mecA class) and belonged to 2 different genotypes. The cfr gene was not found, but the mutation G2603T was detected in S. haemolyticus and C2190T and G2603T in Staphylococcus hominis in 23S rRNA. This study demonstrates the spread of a linezolid-resistant S. haemolyticus genotype and, for the first time, describes the mutation C2190T among S. hominis isolates with a double mutation in Brazil.

Chamon RC ，Iorio NL ，Cavalcante FS ，Teodoro CR ，de Oliveira AP ，Maia F ，dos Santos KR ... -  《-》

Mechanisms of Linezolid Resistance Among Clinical Staphylococcus spp. in Spain: Spread of Methicillin- and Linezolid-Resistant S. epidermidis ST2.

Ruiz-Ripa L ，Feßler AT ，Hanke D ，Eichhorn I ，Azcona-Gutiérrez JM ，Alonso CA ，Pérez-Moreno MO ，Aspiroz C ，Bellés A ，Schwarz S ，Torres C ... -  《-》

Nosocomial outbreak of methicillin- and linezolid-resistant Staphylococcus epidermidis associated with catheter-related infections in intensive care unit patients.

A total of 128 isolates associated with catheter-related infections was recovered from 101 intensive care unit patients in a Spanish hospital during March 2008 to August 2009, and 27 of these isolates (from 21 patients) were typed as methicillin- and linezolid-resistant Staphylococcus epidermidis. Thirteen of these 21 patients (62%) had received linezolid during the 3 months preceding S. epidermidis recovery. Two closely related pulsotypes (P1a and P1b) were identified among the 27 studied isolates that belonged to the sequence type ST2 and harboured the mecA gene and the SCCmecIII type. The strains recovered from patients 1-4 (pulsotype P1a) showed the nucleotide mutation G2474T inside the amplified fragment of the 23S rRNA region and carried the aac(6')-Ie-aph(2″)-Ia, ant(4'), and catA genes, whereas the strains from patients 5-21 (pulsotype P1b) showed the mutation G2603T and carried the aac(6')-Ie-aph(2″)-Ia gene. None of the strains amplified the cfr gene. The ica gene and the IS256 element were detected in all strains. The emergence of 2 closely related methicillin- and linezolid-resistant S. epidermidis strains with 2 different mutations in the 23S rRNA region (G2474T and G2603T) is reported in this study as a cause of a nosocomial outbreak. The presence of G2474T or G2603T point mutations suggests that there are multiple potential sites within domain V of the 23S rRNA region at which mutations could confer resistance to linezolid in the clinical isolates. To our knowledge, this is the first report in which the G2474T mutation has been detected in domain V of the 23S rRNA gene of clinical S. epidermidis.

Seral C ，Sáenz Y ，Algarate S ，Duran E ，Luque P ，Torres C ，Castillo FJ ... -  《-》

Detection of new mutations conferring resistance to linezolid in glycopeptide-intermediate susceptibility Staphylococcus hominis subspecies hominis circulating in an intensive care unit.

Sorlozano A ，Gutierrez J ，Martinez T ，Yuste ME ，Perez-Lopez JA ，Vindel A ，Guillen J ，Boquete T ... -  《-》