Staphylococcus haemolyticus as an Important Hospital Pathogen and Carrier of Methicillin Resistance Genes

Abstract

Phenotypic and molecular methods were used to characterize the antibiotic resistance of 64 clinical isolates of Staphylococcus haemolyticus. By PCR of the mecA gene, 87% were found to be methicillin resistant. Approximately 55% harbored staphylococcal cassette chromosome mec element (SCCmec) type V, and only one SCCmec type IV. Many isolates (75%) displayed multiresistance, and pulsotype analysis showed a high diversity.A mong coagulase-negative staphylococci (CoNS), Staphylococcus haemolyticus is the second most frequently isolated from human blood cultures (18) and has the highest level of antimicrobial resistance (3,8). Methicillin resistance is conferred by the mecA gene, carried on the staphylococcal cassette chromosome mec element (SCCmec) (12). Eight types (I to VIII) of SCCmec have been assigned for Staphylococcus aureus (11), and SCCmec type V has already been found in CoNS, particularly in S. haemolyticus (13). The increase in the frequency of methicillinresistant S. haemolyticus as the causal agent of hospital infections and the possibility of emergence of resistance to other antibiotics demand trustworthy characterization of the isolates and an investigation of clonal spreading within hospitals.In the studies reported here, 64 clinical strains were isolated from patients at Hospital Naval Marcílio Dias, Rio de Janeiro, Brazil, between 2006 and 2008. The strains were isolated from the following clinical infections or sources in 31 males and 33 females: bacteremia (n ϭ 45), skin (n ϭ 2), urine (n ϭ 13), and unknown source (n ϭ 4). The isolates were identified at the hospital laboratory as S. haemolyticus by using the MicroScan WalkAway PC21 panel, and their identification was confirmed by specific PCR (17).The resistance profiles of the strains for the main antibiotics used in Brazil were determined by disc diffusion tests according to CLSI guidelines (5). However, the mupirocin susceptibility testing was not preconized by CLSI, so the results for this antibiotic were interpreted as previously described (7, 9). The methicillin resistance was also evaluated by other phenotypic methods, such as the MIC for oxacillin (5), the MicroScan, and PCR of the mecA gene (6). The SCCmec type was determined in a multiplex PCR as previously described (14), except that the pair of primers mecI P2 and mecI P3 used as the internal control were replaced by MRS1 and MRS2 (6), which amplify a 154-bp fragment of the mecA gene.Analysis of genetic relatedness and characterization of isolates using pulsed-field gel electrophoresis (PFGE) of genomic DNA digested with SmaI were carried out as previously described (20). Banding patterns were determined by visual inspection and by using Bionumerics software, version 6.0 (Applied Maths) using the Dice index and the unweighted-pair group method with arithmetic average. Similar PFGE genotypes were defined using a coefficient of similarity of up to 80%, and the subtypes were those with less than five-band variants, as recommended by van Belkun et al. (19).As shown in Table 1, there wa...

Staphylococcal cassette chromosome mec typing and mecA sequencing in methicillin-resistant staphylococci from Algeria: a highly diversified element with new mutations in mecA

“…MRS isolates proved to be generally susceptible to antibiotics other than b-lactams. They exhibited significant resistance only toward tetracycline, erythromycin and tobramycin, according to reports from elsewhere (De Mattos et al, 2003;Barros et al, 2011;Al-Bakri et al, 2013).…”

“…Indeed, according to De Mattos et al (2003) and Barbier et al (2010), 23 % and 12 % of isolates belonged to this species, respectively. Barros et al (2011) have considered S. haemolyticus as an important hospital pathogen, as well as a carrier of methicillin resistance genes. Our results significantly differ to the findings by Al-Bakri et al (2013), with 80 % isolates of MR S. epidermidis and only 2 % of MR S. haemolyticus.…”

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

“…The most important factor might be the facility to acquire multiresistance against available antimicrobial agents. In a recent study, Barros et al (2012) noted that 75% of analysed S. haemolyticus isolates displayed multiresistance. This species also plays an important role in the dissemination of resistance genes, contributing to the emergence of epidemic clones of a more virulent nosocomial pathogen, S. aureus (Cavanagh et al, 2014;Fluit et al, 2013).…”

Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci

“…haemolyticus is frequently isolated from blood cultures and has a tendency to develop resistance to multiple antimicrobial drugs 8 , similar to S. warneri, which is another CoNS that can cause catheter-related bacteremia and native and prosthetic valve endocarditis 9 . Two isolates of this bacterial species were misclassifi ed as S. warneri by the Vitek 2 system.…”