Heterogeneous resistance to vancomycin in Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus warneri clinical strains: characterisation of glycopeptide susceptibility profiles and cell wall thickening

• Published in: International journal of antimicrobial agents 2006-04, Vol.27 (4), p.307-315
• Main Authors: Nunes, Ana Paula Ferreira, Teixeira, Lúcia Martins, Iorio, Natália Lopes Pontes, Bastos, Carla Callegário Reis, Fonseca, Leila de Sousa, Souto-Padrón, Thaís, dos Santos, Kátia Regina Netto
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antibiotics. Antiinfectious agents. Antiparasitic agents; Bacteriolysis; Biological and medical sciences; Brazil; Cell Wall - ultrastructure; Colony Count, Microbial; Heteroresistance; Humans; Medical sciences; Microbial Sensitivity Tests; Microscopy, Electron, Transmission; Pharmacology. Drug treatments; Population analysis profile; Staphylococcal Infections - microbiology; Staphylococci; Staphylococcus - drug effects; Staphylococcus - isolation & purification; Staphylococcus - ultrastructure; Staphylococcus epidermidis; Staphylococcus epidermidis - drug effects; Staphylococcus epidermidis - isolation & purification; Staphylococcus epidermidis - ultrastructure; Staphylococcus haemolyticus; Staphylococcus haemolyticus - drug effects; Staphylococcus haemolyticus - isolation & purification; Staphylococcus warneri; Teicoplanin; Teicoplanin - pharmacology; Transmission electron microscopy; Vancomycin; Vancomycin Resistance
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2005.11.013

The population analysis profile (PAP) method as well as analysis of autolytic activity and cellular ultrastructure by transmission electron microscopy (TEM) were used to characterise Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus warneri clinical strains with reduced susceptibility to glycopeptides. All strains showed heterogeneous profiles to vancomycin and teicoplanin by the PAP method. Subpopulations that grew in the presence of high concentrations of each drug were selected from the PAP as derivative strains. Their glycopeptide minimal inhibitory concentrations (MICs) were determined and subsequently all parental and derivative strains were grown in one-half of the MIC of vancomycin or teicoplanin. An increase in cell wall thickness of all derivative strains was seen by TEM, with statistically significant values ( P < 0.01) compared with their respective parental strains. In general, variable rates of autolysis among the strains were observed. Cell wall thickness is an important factor involved in glycopeptide resistance and, in association with PAP results, confirmed the Brazilian coagulase-negative staphylococci clinical isolates as being heteroresistant to glycopeptides. Detection of these heteroresistant organisms is important in order to achieve more judicious use of vancomycin and teicoplanin in hospitals.