RESUMO
BACKGROUND: Despite 10 years of clinical use, linezolid resistance in Staphylococcus aureus and coagulase-negative staphylococci (CoNS) is still a rare phenomenon. This study reports the mechanisms of resistance and strain types seen in clusters of linezolid-resistant CoNS from two different hospitals in Italy during the period 2008-09. METHODS: Genes associated with linezolid resistance were subjected to molecular analysis and isolates were characterized by PFGE macrorestriction analysis using SmaI. RESULTS: Thirty-three linezolid-resistant isolates of methicillin-resistant CoNS comprising Staphylococcus epidermidis (24), Staphylococcus hominis (5) and Staphylococcus simulans (4) were studied. The isolates showed varying levels of linezolid resistance. Almost all isolates for which linezolid MICs were 64 mg/L possessed point mutations in domain V of 23S rRNA, while isolates for which the MICs were 256 mg/L expressed methylase activity at position A2503 mediated by the cfr gene. Overall, the isolates showed reduced susceptibility to vancomycin (MICs 1-2 mg/L) and 11 of the 33 isolates showed no susceptibility to teicoplanin. These strains were also resistant to chloramphenicol (28 of 33), lincomycin (24 of 33), erythromycin (17 of 33) and quinupristin/dalfopristin (13 of 33). S. epidermidis isolates, showing mutations or methylase modifications, belonged to different PFGE profiles and to two different sequence types (ST2 and ST23), in which the cfr gene was carried on a plasmid of â¼50 kb. CONCLUSIONS: Clinical CoNS strains with resistance to linezolid and other second-line antibiotics, as well as reduced susceptibility to glycopeptides, have emerged in Italy.
Assuntos
Acetamidas/farmacologia , Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla , Oxazolidinonas/farmacologia , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacos , Staphylococcus hominis/efeitos dos fármacos , Técnicas de Tipagem Bacteriana , Impressões Digitais de DNA , Metilação de DNA , Metilases de Modificação do DNA/metabolismo , DNA Bacteriano/genética , DNA Bacteriano/metabolismo , Desoxirribonucleases de Sítio Específico do Tipo II/metabolismo , Eletroforese em Gel de Campo Pulsado , Hospitais , Humanos , Itália , Linezolida , Testes de Sensibilidade Microbiana , Mutação Puntual , RNA Ribossômico 23S/genética , Staphylococcus aureus/classificação , Staphylococcus aureus/enzimologia , Staphylococcus aureus/genética , Staphylococcus epidermidis/classificação , Staphylococcus epidermidis/enzimologia , Staphylococcus epidermidis/genética , Staphylococcus hominis/classificação , Staphylococcus hominis/enzimologia , Staphylococcus hominis/genéticaRESUMO
In the last decade the detection of the resistance of bacteria to antibiotics treatment, developed by different kind of bacteria, is becoming a huge problem. We hereby present a different approach to the current problem of detection of bacteria resistance to antibiotics. Our aims were to use the atomic force microscopy (AFM) to investigate bacteria morphological changes in response to antibiotics treatment and explore the possibility of reducing the time required to obtain information on their resistance. In particular, we studied Klebsiella pneumoniae bacteria provided by the Lavagna Hospital ASL4 Liguria (Italy), where there are cases linked with antibiotics resistance of the Klebsiella pneumoniae. By comparing AFM images of bacteria strains treated with different antibiotics is possible to identify unambiguously the Klebsiella pneumoniae strains resistant to antibiotics. In fact, the analysis of the AFM images of the antibiotic-sensitive bacteria shows clearly the presence of morphological alterations in the cell wall. While in the case of the antibiotic-resistant bacteria morphological alterations are not present. This approach is based on an easy and potentially rapid AFM analysis.