Antimicrobial resistance in nosocomial isolates of Staphylococcus haemolyticus

Abstract

Staphylococcus haemolyticus is frequently cultured from hospitalized patients and is characterized by resistance to multiple antimicrobial agents. We found that S. haemolyticus represented 70 of 524 (13%) coagulase-negative staphylococcal isolates identified by the clinical microbiology laboratories of two hospitals over 2 months. S. haemolyticus isolates were recovered from wounds (44%), urine (26%), blood (10%), and other sources (20%). All S. haemolyticus isolates were tested for susceptibility to six antimicrobial agents; 77% were resistant to three or more agents, and 41% were resistant to five or six agents. In addition, among 47 multiply resistant isolates, high MICs (.6.25 ,ug/ml) of vancomycin (62% of isolates) and teicoplanin (91% of isolates) were found. DNA probes which were derived from S. epidermidis or S. aureus and which contained sequences associated with resistance to antimicrobial agents were used to detect specific genes in the total cellular and plasmid DNAs of 10 resistant S. haemolyticus isolates. Resistance gene probes and the numbers of resistant isolates hybridizing were as follows: methicillin, 10 of 10; gentamicin, 9 of 10; erythromycin, 7 of 10; and trimethoprim, 0 of 10. Genes for resistance to methicillin were found only in chromosomal locations, genes for resistance to gentamicin were found in both chromosomal and plasmid locations, and genes for resistance to erythromycin were found in plasmid locations only. With the exception of trimethoprim resistance determinants, similar genes were found among concurrently isolated multiply resistant S. epidermidis isolates from our hospitals. S. haemolyticus is a potentially important nosocomial species which readily acquires antimicrobial resistance genes and which shares, to some extent, in a common gene pool with S. epidermidis.Staphylococcus haemolyticus has been reported to represent an average of 10% of clinical coagulase-negative staphylococcal isolates (5,7,9,12,15,22,24,25,27,28). Many of these isolates have been found to be resistant to multiple antimicrobial agents. The importance of these organisms as human pathogens relative to that of other coagulase-negative staphylococci is uncertain, in part because species determinations of coagulase-negative staphylococci are not routinely done in most clinical microbiology laboratories. The mechanisms of antimicrobial resistance in S. haemolyticus and the extent to which it shares resistance genes with other staphylococci are also unknown. In a recent study of trimethoprim resistance among coagulase-negative staphylococci (6), we found that a specific trimethoprim resistance gene probe from a conjugative S. aureus plasmid hybridized with all trimethoprim-resistant S. epidermidis isolates but not with four S. haemolyticus isolates tested. The possibility of unique mechanisms of resistance in this poorly understood species led us to further investigate its characteristics.In the present study, we determined the proportion of S. haemolyticus isolates among clinical isolates of coagulasenega...

Core genome conservation of Staphylococcus haemolyticus limits sequence based population structure analysis

“…patients with haematological disease and immature infants (Nouri et al, 2008). The ability to produce biofilm and the notoriously multi-resistance to antimicrobial agents, including glycopeptides, favours S. haemolyticus as an emerging cause of nosocomial infections (de Allori et al, 2006;Falcone et al, 2006;Fredheim et al, 2009;Froggatt et al, 1989;Hiramatsu, 1998;Hope et al, 2008;Koksal et al, 2009;Schwalbe et al, 1987).…”

“…the staphylococcal cassette chromosome -SCC) but also regions unique to each species. Sequence similarity between resistance genes suggests that resistance determinants are readily transferred between these staphylococcal species (Froggatt et al, 1989). When comparing different S. haemolyticus isolates, large scale chromosomal inversions in the oriC environ were reported (Watanabe et al, 2007).…”

Species distribution and antimicrobial resistance pattern of Coagulase-negative Staphylococci at a tertiary care centre

“…Similarly, Sheikh et al 5 also isolated 90.9% of S. saprophyticus from urine samples of female patients and Froggatt et al 6 isolated S. hemolyticus mainly from wound and pus samples. Coagulase-negative Staphylococci, especially S. epidermidis, are the most prominent cause of intravascular catheter related infections and hospital acquired bloodstream infections.…”

Biofilm Formation by Staphylococcus haemolyticus

“…S. haemolyticus plays an important role in hospital-acquired opportunistic infections related to implanted medical devices (29,31,34). Furthermore, S. haemolyticus has the highest level of antimicrobial resistance among all CoNS species, and heteroresistance to glycopeptides is common (8,19). This limits the therapeutic options available and makes an S. haemolyticus infection a serious threat.…”