Multiplex PCR assay to identify methicillin-resistant Staphylococcus haemolyticus

Staphylococcus haemolyticus: An updated review on nosocomial infections, antimicrobial resistance, virulence, genetic traits, and strategies for combating this emerging opportunistic pathogen

Staphylococcus haemolyticus, a key species of the Staphylococcus genus, holds significant importance in healthcare-associated infections, due to its notable resistance to antimicrobials, like methicillin, and proficient biofilms-forming capabilities. This coagulase-negative bacterium poses a substantial challenge in the battle against nosocomial infections. Recent research has shed light on Staph. haemolyticus genomic plasticity, unveiling genetic elements responsible for antibiotic resistance and their widespread dissemination within the genus. This review presents an updated and comprehensive overview of the clinical significance and prevalence of Staph. haemolyticus, underscores its zoonotic potential and relevance in the one health framework, explores crucial virulence factors, and examines genetics features contributing to its success in causing emergent and challenging infections. Additionally, we scrutinize ongoing studies aimed at controlling spread and alternative approaches for combating it.

Current types of staphylococcal cassette chromosome mec (SCCmec) in clinically relevant coagulase-negative staphylococcal (CoNS) species

Coagulase-negative staphylococci (CoNS) colonize human skin and mucosal membranes, which is why they are considered harmless commensal bacteria. Two species, Staphylococcus epidermidis and Staphylococcus haemolyticus belong to the group of CoNS species and are most frequently isolated from nosocomial infections, including device-associated healthcare-associated infections (DA-HAIs) and local or systemic body-related infections (FBRIs). Methicillin resistance, initially described in Staphylococcus aureus, has also been reported in CoNS species. It is mediated by the mecA gene within the staphylococcal cassette chromosome (SCCmec). SCCmec typing, primarily using PCR-based methods, has been employed as a molecular epidemiological tool. However, the introduction of whole genome sequencing (WGS) and next-generation sequencing (NGS) has enabled the identification and verification of new SCCmec types. This review describes the current distribution of SCCmec types, subtypes, and variants among CoNS species, including S. epidermidis, S. haemolyticus, and S. capitis. The literature review focuses on recent research articles from the past decade that discuss new combinations of SCCmec in coagulase-negative Staphylococcus. The high genetic diversity and gaps in CoNS SCCmec annotation rules underscore the need for an efficient typing system. Typing SCCmec cassettes in CoNS strains is crucial to continuously updating databases and developing a unified classification system.

A rapid and visual detection of Staphylococcus haemolyticus in clinical specimens with RPA-LFS

Staphylococcus haemolyticus (S. haemolyticus), which is highly prevent in the hospital environment, is an etiological factor for nosocomial infections. Point-of-care rapid testing (POCT) of S. haemolyticus is not possible with the currently used detection methods. Recombinase polymerase amplification (RPA) is a novel isothermal amplification technology with high sensitivity and specificity. The combination of RPA and lateral flow strips (LFS) can achieve rapid pathogen detection, enabling POCT. This study developed an RPA-LFS methodology using a specific probe/primer pair to identify S. haemolyticus. A basic RPA reaction was performed to screen the specific primer from 6 primer pairs targeting mvaA gene. The optimal primer pair was selected based on agarose gel electrophoresis, and the probe was designed. To eliminate false-positive results caused by the byproducts, base mismatches were introduced in the primer/probe pair. The improved primer/probe pair could specifically identify the target sequence. To explore the optimal reaction conditions, the effects of reaction temperature and duration of the RPA-LFS method were systematically investigated. The improved system enabled optimal amplification at 37 °C for 8 min, and the results were visualized within 1 min. The S. haemolyticus detection sensitivity of the RPA-LFS method, whose performance was unaffected by contamination with other genomes, was 0.147 CFU/reaction. Furthermore, we analyzed 95 random clinical samples with RPA-LFS, quantitative polymerase chain reaction (qPCR), and traditional bacterial-culture assays and found that the RPA-LFS had 100% and 98.73% compliance rates with the qPCR and traditional culture method, respectively, which confirms its clinical applicability. In this study, we designed an improved RPA-LFS assay based on the specific probe/primer pair for the detection of S. haemolyticus via rapid POCT, free from the limitations of the precision instruments, helping to make diagnoses and treatment decisions as soon as possible.

Unusual carriage of virulence genes sasX/sesI/shsA by nosocomial Staphylococcus haemolyticus from Brazil

Background: Staphylococcus haemolyticus is an emerging threat in the nosocomial environment but only some virulence factors are known. Materials & methods: The frequency of the sasX gene (or orthologues sesI/shsA), encoding an invasiveness-related surface-associated protein, in S. haemolyticus was detected in different hospitals in Rio de Janeiro. Results: 9.4% of strains were sasX/sesI/shsA-positive, some were in the context of the ΦSPβ-like prophage and devoid of CRISPR systems, indicating potential transferability of their virulence genes. Gene sequencing evidenced that Brazilian S. haemolyticus harbored sesI, instead of the usual sasX, while S. epidermidis had sasX instead of sesI, suggesting horizontal acquisition. Conclusion: The contexts of Brazilian sasX/sesI/shsA favor transfer, which is alarming given the difficulty in treating infections caused by S. haemolyticus.

Methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolates from skin and nares of Brazilian children with atopic dermatitis demonstrate high level of clonal diversity

BACKGROUND

Atopic dermatitis (AD) primarily affects the pediatric population, which is highly colonized by S. aureus. However, little is known about the genetic features of this microorganism and other staphylococcal species that colonize AD patients.

OBJECTIVE

This study aimed to characterize Staphylococcus spp. isolated from the nares and skin (with and without lesion) of 30 AD and 12 non-AD Brazilian children.

METHODS

Skin and nasal swabs were cultured onto mannitol salt agar, and bacterial colonies were counted and identified by matrix assisted laser desorption ionization time of flight mass spectrometry and polymerase chain reaction (PCR). Antimicrobial susceptibility was evaluated by phenotypic and genotypic tests. In S. aureus isolates, Panton-Valentine leukocidin genes were detected by PCR, and their clonality was assessed by pulsed-field gel electrophoresis and multilocus sequence typing.

RESULTS

S. aureus was more prevalent in the nares (P = 0.005) and lesional skin (P = 0.0002) of children with AD, while S. hominis was more frequent in the skin of non-AD children (P < 0.0001). All children in the study, except one from each group, were colonized by methicillin-resistant coagulase-negative Staphylococcus and 24% by methicillin-resistant S. aureus. Despite the great clonal diversity of S. aureus (18 sequence types identified), most AD children (74.1%) were colonized by the same genotype in both niches.

CONCLUSION

High colonization by polyclonal S. aureus isolates was found among children with AD, while S. hominis was more frequent among non-AD children. The high prevalence of methicillin-resistant staphylococcal isolates highlights the importance of continued surveillance, especially when considering empiric antibiotic therapy for the treatment of skin infections in these patients.

Clinical Infections, Antibiotic Resistance, and Pathogenesis of Staphylococcus haemolyticus

Staphylococcus haemolyticus (S. haemolyticus) constitutes the main part of the human skin microbiota. It is widespread in hospitals and among medical staff, resulting in being an emerging microbe causing nosocomial infections. S. haemolyticus, especially strains that cause nosocomial infections, are more resistant to antibiotics than other coagulase-negative Staphylococci. There is clear evidence that the resistance genes can be acquired by other Staphylococcus species through S. haemolyticus. Severe infections are recorded with S. haemolyticus such as meningitis, endocarditis, prosthetic joint infections, bacteremia, septicemia, peritonitis, and otitis, especially in immunocompromised patients. In addition, S. haemolyticus species were detected in dogs, breed kennels, and food animals. The main feature of pathogenic S. haemolyticus isolates is the formation of a biofilm which is involved in catheter-associated infections and other nosocomial infections. Besides the biofilm formation, S. haemolyticus secretes other factors for bacterial adherence and invasion such as enterotoxins, hemolysins, and fibronectin-binding proteins. In this review, we give updates on the clinical infections associated with S. haemolyticus, highlighting the antibiotic resistance patterns of these isolates, and the virulence factors associated with the disease development.

Pathogenesis of Staphylococcus haemolyticus on primary human skin fibroblast cells

STAPHYLOCOCCUS HAEMOLYTICUS

(S. haemolyticus) is one of the Coagulase-negative staphylococci (CoNS) that inhabits the skin as a commensal. It is increasingly implicated in opportunistic infections, including diabetic foot ulcer (DFU) infections. In contrast to the abundance of information available for S. aureus and S. epidermidis, little is known about the pathogenicity of S. haemolyticus, despite the increased prevalence of this pathogen in hospitalized patients. We described, for the first time, the pathogenesis of different clinical isolates of S. haemolyticus isolated from DFU on primary human skin fibroblast (PHSF) cells. Virulence-related genes were investigated, adhesion and invasion assays were carried out using Giemsa stain, transmission electron microscopy (TEM), MTT and flowcytometry assays. Our results showed that most S. haemolyticus carried different sets of virulence-related genes. S. haemolyticus adhered to the PHSF cells to variable degrees. TEM showed that the bacteria were engulfed in a zipper-like mechanism into a vacuole inside the cell. Bacterial internalization was confirmed using flowcytometry and achieved high intracellular levels. PHSF cells infected with S.haemolyticus suffered from amarked decrease in viability and increased apoptosis when treated with whole bacterial suspensions or cell-free supernatants but not with heat-treated cells. After co-culture with PBMCs, S. haemolyticus induced high levels of pro-inflammatory cytokines. This study highlights the significant development of S. haemolyticus, which was previously considered a contaminant when detected in cultures of clinical samples. Their high ability to adhere, invade and kill the PHSF cells illustrate the severe damage associated with DFU infections.

ABBREVIATIONS

CoNS, coagulase-negative staphylococci; DFU, diabetic foot ulcer; DM, diabetes mellitus; DMEM, Dulbecco's Modified Eagle Medium; MTT, 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide; PBMCs,peripheral blood mononuclear cells; PHSF, primary human skin fibroblast; CFU, colony-forming unit.

High rate of detection of OXA-23-producing Acinetobacter from two general hospitals in Brazil

INTRODUCTION

In recent decades, the prevalence of carbapenem-resistant Acinetobacter isolates has increased, and the production of oxacillinase (OXA)-type carbapenemases is the main mechanism underlying resistance. We evaluated OXA production from 114 Acinetobacter isolates collected between March and December 2013 from different clinical specimens of patients in two hospitals (Hospital 1 [n = 61] and Hospital 2 [n = 53]) located in Niterói, Rio de Janeiro, Brazil. We also evaluated the genetic diversity of OXA-producing isolates.

METHODS

All the isolates were identified through the automated system Vitek II and matrix-assisted laser desorption ionization-time of flight mass spectrometry MALDI-TOF MS as belonging to the A. baumannii-A. calcoaceticuscomplex. Antimicrobial susceptibility profiles were verified through agar diffusion tests. The presence of OXA-encoding genes was confirmed by PCR. The genetic diversity of isolates positive for carbapenemase production was analyzed through pulsed-field gel electrophoresis.

RESULTS

There was a high rate of resistance to carbapenems in the isolates (imipenem: 96%; meropenem: 92%) from both hospitals. Moreover, a high percentage (95.6%) of OXA-23-positive isolates was observed for both hospitals, indicating that this was the main mechanism of carbapenem-resistance among the studied population. In addition, most isolates (96.5%) were positive for bla OXA-51. A high genetic diversity and a few major genotypes were found among the OXA-23-positive isolates analyzed. Only intra-hospital dissemination was observed.

CONCLUSIONS

The elevated dissemination of bla OXA-23-like observed among Acinetobacter isolates from both the studied hospitals highlights the need for continuous epidemiological surveillance in these institutions.

Influence of antibiotics on biofilm formation by different clones of nosocomial Staphylococcus haemolyticus

Staphylococcus haemolyticus is the most common organism among clinical isolatesof methicillin-resistant staphylococci. Aim: This study evaluated the ability to produce biofilm with the presence of the antibiotics (1/4 minimum inhibitory concentrations) of S. haemolyticus strains isolated from blood culture. Methods: Clonal distribution was assessed in pulsed-field gel electrophoresis. PCR assays were performed to detect mecA, icaA, aap, atlE, atl, fbp genes. S. haemolyticus strains grown in the presence of the antibiotics were investigated for biofilm formation on glass, polystyrene and catheter surfaces. Results: Biofilm formation was independent of the presence of the icaA and mecA genes, pulsed-field gel electrophoresis type. Vancomycin, oxacillin, moxifloxacin, rifampicin, teicoplanin, tigecycline and linezolid did not inhibit biofilm formation on abiotic surfaces. Conclusion: This study demonstrated that the biofilm formation process is complex and may not be related to ica gene carriage. Furthermore, in this study the biofilm formation was increased in the presence of antimicrobial agents.

Sphygmomanometers and thermometers as potential fomites of Staphylococcus haemolyticus: biofilm formation in the presence of antibiotics

BACKGROUND

The association between Staphylococcus haemolyticus and severe nosocomial infections is increasing. However, the extent to which fomites contribute to the dissemination of this pathogen through patients and hospital wards remains unknown.

OBJECTIVES

In the present study, sphygmomanometers and thermometers were evaluated as potential fomites of oxacillin-resistant S. haemolyticus (ORSH). The influence of oxacillin and vancomycin on biofilm formation by ORSH strains isolated from fomites was also investigated.

METHODS

The presence of ORSH on swabs taken from fomite surfaces in a Brazilian hospital was assessed using standard microbiological procedures. Antibiotic susceptibility profiles were determined by the disk diffusion method, and clonal distribution was assessed in pulsed-field gel electrophoresis (PFGE) assays. Minimum inhibitory concentrations (MICs) of oxacillin and vancomycin were evaluated via the broth microdilution method. Polymerase chain reaction (PCR) assays were performed to detect the mecA and icaAD genes. ORSH strains grown in media containing 1/4 MIC of vancomycin or oxacillin were investigated for slime production and biofilm formation on glass, polystyrene and polyurethane catheter surfaces.

FINDINGS

ORSH strains comprising five distinct PFGE types were isolated from sphygmomanometers (n = 5) and a thermometer (n = 1) used in intensive care units and surgical wards. ORSH strains isolated from fomites showed susceptibility to only linezolid and vancomycin and were characterised as multi-drug resistant (MDR). Slime production, biofilm formation and the survival of sessile bacteria differed and were independent of the presence of the icaAD and mecA genes, PFGE type and subtype. Vancomycin and oxacillin did not inhibit biofilm formation by vancomycin-susceptible ORSH strains on abiotic surfaces, including on the catheter surface. Enhanced biofilm formation was observed in some situations. Moreover, a sub-lethal dose of vancomycin induced biofilm formation by an ORSH strain on polystyrene.

MAIN CONCLUSIONS

Sphygmomanometers and thermometers are fomites for the transmission of ORSH. A sub-lethal dose of vancomycin may favor biofilm formation by ORSH on fomites and catheter surfaces.

Transfer of mupirocin resistance from Staphylococcus haemolyticus clinical strains to Staphylococcus aureus through conjugative and mobilizable plasmids

Coagulase-negative staphylococci are thought to act as reservoirs of antibiotic resistance genes that can be transferred to Staphylococcus aureus, thus hindering the combat of this bacterium. In this work, we analyzed the presence of plasmids conferring resistance to the antibiotic mupirocin-widely used to treat and prevent S. aureus infections in hospital environments-in nosocomial S. haemolyticus strains. About 12% of the 75 strains tested were resistant to mupirocin, and this phenotype was correlated with the presence of plasmids. These plasmids were shown to be diverse, being either conjugative or mobilizable, and capable of transferring mupirocin resistance to S. aureus Our findings reinforce that S. haemolyticus, historically and mistakenly considered as a less important pathogen, is a reservoir of resistance genes which can be transferred to other bacteria, such as S. aureus, emphasizing the necessity of more effective strategies to detect and combat this emergent opportunistic pathogen.

Searching Biomarkers in the Sequenced Genomes of Staphylococcus for their Rapid Identification

Bacterial identification using rrs (16S rRNA) gene is widely reported. Bacteria possessing multiple copies of rrs lead to overestimation of its diversity. Staphylococcus genomes carries 5-6 copies of rrs showing high similarity in their nucleotide sequences, which lead to ambiguous results. The genomes of 31 strains of Staphylococcus representing 7 species were searched for the presence of common genes. In silico digestion of 34 common genes using 10 restriction endonucleases (REs) lead to select gene-RE combinations, which could be used as biomarkers. RE digestion of recA allowed unambiguous identification of 13 genomes representing all the 7 species. In addition, a few more genes (argH, argR, cysS, gyrB, purH, and pyrE) and RE combinations permitted further identification of 12 strains. By employing additional RE and genes unique to a particular strain, it was possible to identify the rest 6 Staphylococcus aureus strains. This approach has the potential to be utilized for rapid detection of Staphylococcus strains.

Antibiotic surgical prophylaxis increases nasal carriage of antibiotic-resistant staphylococci

Staphylococci are a significant cause of hospital-acquired infection. Nasal carriage of Staphylococcus aureus is an important risk factor for infection in surgical patients and coagulase-negative staphylococci (CNS) are a major cause of prosthetic joint infections. The impact that antibiotic surgical prophylaxis has on the nasal carriage of staphylococci has not been studied. Daily nasal swabs were taken from 63 patients who received antibiotic surgical prophylaxis and 16 patients who received no antibiotics. Total aerobic bacterial count, S. aureus and CNS were enumerated by culture from nasal swabs. Representative isolates were typed by staphylococcal interspersed repeat units (SIRU) typing and PFGE, and MICs to nine antibiotics were determined. After antibiotic administration, there was a reduction in S. aureus counts (median - 2.3 log(10)c.f.u. ml(- 1)) in 64.0 % of S. aureus carriers, compared with only a 0.89 log(10)c.f.u. ml(- 1) reduction in 75.0 % of S. aureus carriers who did not receive antibiotics. A greater increase in the nasal carriage rate of meticillin-resistant CNS was observed after antibiotic surgical prophylaxis compared with hospitalization alone, with increases of 16.4 and 4.6 %, respectively. Antibiotic-resistant S. epidermidis carriage rate increased by 16.6 % after antibiotic administration compared with 7.5 % with hospitalization alone. Antibiotic surgical prophylaxis impacts the nasal carriage of both S. aureus and CNS.

Staphylococcal cassette chromosome mec elements in methicillin-resistant coagulase-negative staphylococci from a Brazilian neonatal care unit

To characterize 46 methicillin-resistant coagulase-negative staphylococci from Brazilian neonates, we investigated their SCCmec type, susceptibility and clonality. Staphylococcus epidermidis and Staphylococcus haemolyticus were the prevalent species. SCCmec types III or IV were detected in 53.3% S. epidermidis, whereas 63.6% S. haemolyticus were nontypeable. Despite the diversity, specific clones carried specific SCCmec elements, highlighting that effective typing can help in epidemiological analysis.

Multiplex PCR assay for identification of six different Staphylococcus spp. and simultaneous detection of methicillin and mupirocin resistance

We describe a new, efficient, sensitive, and fast single-tube multiple-PCR protocol for the identification of the most clinically significant Staphylococcus spp. and the simultaneous detection of the methicillin and mupirocin resistance loci. The protocol identifies at the species level isolates belonging to S. aureus, S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, and S. saprophyticus.

A diversity profile from the staphylococcal community on atopic dermatitis skin: a molecular approach

AIMS

The aim of this study was to determine the biodiversity of the skin staphylococcal community from patients with atopic dermatitis (AD) and superantigen (SAg) detection from Staphylococcus aureus isolates.

METHODS AND RESULTS

In this study, we developed a novel multiplex PCR that allows the identification and discrimination of bacteria belonging to the Staphylococcus genus both Staph. aureus and coagulase-negative Staphylococcus - Staph. capitis, Staph. epidermidis, Staph. haemolyticus and Staph. hominis isolated from the skin of patients with AD. In addition, a multiplex PCR assay that allows the rapid screening of the 19 genes that encode staphylococcal enterotoxins (SEs), SE-like toxins and toxic shock syndrome toxin-1 was also performed and applied in Staph. aureus isolates. The microflora of the skin of patients with AD was dominated by Staph. aureus (69 isolates, 35·6%) followed by Staph. epidermidis (59 isolates, 30·4%) species. The SElM and SElN genes were the most frequently detected in our study (15 isolates, 71·4%), followed by SEG and SElO (14 isolates, 66·7%).

CONCLUSIONS

Our molecular-based approach successfully identified the staphylococcal microflora that was relatively specific to patients with AD. Considering skin colonization and expression of virulence factors, the Staph. aureus may play a relevant role in AD pathophysiology.

SIGNIFICANCE AND IMPACT OF THE STUDY

This ability to classify disease-related microbial species provides new insights into the relevance of those microbes in human disorders.

Staphylococcus haemolyticus as an important hospital pathogen and carrier of methicillin resistance genes

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.

Evaluation of the synergistic potential of vancomycin combined with other antimicrobial agents against methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococcus spp strains

Methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative Staphylococcus spp (CNS) are the most common pathogens that cause serious long term infections in patients. Despite the existence of new antimicrobial agents, such as linezolid, vancomycin (VAN) remains the standard therapy for the treatment of infections caused by these multidrug-resistant strains. However, the use of VAN has been associated with a high frequency of therapeutic failures in some clinical scenarios, mainly with decreasing concentration of VAN. This work aims to evaluate the synergic potential of VAN plus sulfamethoxazole/trimethoprim (SXT), VAN plus rifampin (RIF) and VAN plus imipenem (IPM) in sub-minimum inhibitory concentrations against 22 clinical strains of MRSA and CNS. The checkerboard method showed synergism of VAN/RIF and VAN/SXT against two and three of the 22 strains, respectively. The combination of VAN with IPM showed synergistic effects against 21 out of 22 strains by the E-test method. Four strains were analyzed by the time-kill curve method and synergistic activity was observed with VAN/SXT, VAN/RIF and especially VAN/IPM in sub-inhibitory concentrations. It would be interesting to determine if synergy occurs in vivo. Evidence of in vivo synergy could lead to a reduction of the standard VAN dosage or treatment time.

[Evaluation of methods commonly used in laboratories to determine the susceptibility to oxacillin among Staphylococcus sp samples isolated from a hospital in Vitória, State of Espírito Santo]

INTRODUCTION

The genus Staphylococcus is of great importance because of its high prevalence in hospital infections and because it presents high rates of resistance to oxacillin and other antimicrobials. Thus, evaluation of the accuracy of the phenotypic methods that are used to determine the profile of antimicrobial resistance is essential to ensure that the most appropriate therapy is chosen.

METHODS

One hundred and fourteen strains of Staphylococcus sp (53 S. aureus and 61 CNS) were used to evaluate the accuracy of the methods of disk diffusion, agar microdilution, oxacillin screening agar and automated systems, in comparison with PCR for investigating resistance to oxacillin.

RESULTS

The mecA gene was detected in 48 strains (42.1%), and 27 strains (23.7%) showed discrepant results in at least one of the methods (74.1% of CNS, 25.9% of S. aureus). For S. aureus, with the exception of the Microscan Walkaway, all the methods showed 100% specificity and sensitivity. In relation to CNS, the automated system and cefoxitin disk had lower accuracy.

CONCLUSIONS

Use of two methods should be the best option for improved accuracy, especially when the diagnostic laboratory only uses an automated system or oxacillin disk diffusion test. Combination of these methods with others presented almost 100% sensitivity and specificity in our study.

Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus haemolyticus: methicillin-resistant isolates are detected directly in blood cultures by multiplex PCR

In this study, we standardized and evaluated a multiplex-PCR methodology using specific primers to identify Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus haemolyticus and their methicillin-resistance directly from blood cultures. Staphylococci clinical isolates (149) and control strains (16) previously identified by conventional methods were used to establish the multiplex PCR protocol. Subsequently, this methodology was evaluated using a fast and cheap DNA extraction protocol from 25 staphylococci positive blood cultures. A wash step of the pellet with 0.1% bovine serum albumin (BSA) solution was performed to reduce PCR inhibitors. Amplicons of 154bp (mecA gene), 271bp (S. haemolyticus mvaA gene) and 108 and 124bp (S. aureus and S. epidermidis species-specific fragments, respectively) were observed. Reliable results were obtained for 100% of the evaluated strains, suggesting that this new multiplex-PCR combined with an appropriate DNA-extraction method could be useful in the laboratory for fast and accurate identification of three staphylococci species and simultaneously their methicillin resistance directly in blood cultures.