Investigation of Staphylococcus strains with heterogeneous resistance to glycopeptides in a Turkish university hospital

Staphylococcus haemolyticus – an emerging threat in the twilight of the antibiotics age

“…They also emerged after long-term treatment with teicoplanin in infections caused by S. epidermidis strains (Aubert et al, 1990;Blans & Troelstra, 2001). The wide use of glycopeptides in the hospital environment led to the selection of strains with reduced susceptibility to these antibiotics, with MIC values *4-8 mg l 21 for vancomycin and/or 8-16 mg l 21 for teicoplanin (Nakipoglu et al, 2005;Natoli et al, 2009;Tabe et al, 2001). The first cases like these were reported in 1979 and 1983, when CNS were regarded as bacteria with a low pathogenic potential (Siebert et al, 1979;Tuazon & Miller, 1983).…”

Antimicrobial Heteroresistance: an Emerging Field in Need of Clarity

“…For example, heteroresistance was defined by growth of A. baumannii colonies on plates containing 8 g/ml of colistin, with confirmation of a MIC of 8 g/ml by a subsequent broth microdilution method (11). Similarly, heterogeneously resistant staphylococci were defined as any culture containing subpopulations at a frequency of 1 in 10 6 CFU/ml or higher, with a MIC of Ͼ4 g/ml for vancomycin or Ն16 g/ml for teicoplanin (12), or simply with a MIC above those specified in the CLSI guidelines for breakpoints of vancomycin or teicoplanin (13). A similar definition was adopted by setting a cutoff diameter of 10 mm in disc diffusion assays, below which the strain was considered heteroresistant rather than merely resistant (14).…”

“…For example, several studies investigated the response to glycopeptide antibiotics by using PAP assays with narrow increments in antibiotic concentrations, such as 1-g/ml steps (9,13,, and even as low as 0.1-g/ml steps (66). In these cases, a homogeneous strain could inaccurately be considered heteroresistant, and sometimes the same strain appeared to be homogeneous by one curve and heterogeneous by another (12).…”

Investigation of Vancomycin Resistance in Staphylococcus aureus Strains Detected by Microdilution and Agar Screening Method

“…Nakipoğlu ve ark. (14) yaptıkları çalışmada agar tarama ve populasyon analiz metodunu uygulamışlardır. Her iki çalışmada hVISA veya VISA suşlarına rastlanmamıştır.…”