Survey of methicillin-resistant coagulase-negative staphylococci in the hospitals of central Greece

Characterization of a Lytic Bacteriophage vB_SurP-PSU3 Infecting Staphylococcus ureilyticus and Its Efficacy Against Biofilm

In response to the increasing nosocomial infections caused by antimicrobial-resistant coagulase-negative staphylococci (CoNS), bacteriophages (phages) have emerged as an alternative to antibiotics. Staphylococcus ureilyticus, one of the representative species of the CoNS, is now considered a notable pathogen that causes nosocomial bloodstream infections, and its biofilm-forming ability increases pathogenicity and resistance to antimicrobial agents. In this study, a lytic phage infecting S. ureilyticus was newly isolated from wastewater collected from a sewage treatment plant and its biological and antimicrobial characteristics are described. The isolated phage, named vB_SurP-PSU3, was morphologically similar to Podoviridae and could simultaneously lyse some S. warneri strains used in this study. The sequenced genome of the phage consisted of linear dsDNA with 18,146 bp and genome-based phylogeny revealed that vB_SurP-PSU3 belonged to the genus Andhravirus. Although its overall genomic arrangement and contents were similar to those of other members of the Andhravirus, the predicted endolysin of vB_SurP-PSU3 distinctly differed from the other members of the genus. The bacteriolytic activity of vB_SurP-PSU3 was evaluated using S. ureilyticus ATCC 49330, and the phage could efficiently inhibit the planktonic growth of the bacteria. Moreover, the anti-biofilm analysis showed that vB_SurP-PSU3 could prevent the formation of bacterial biofilm and degrade the mature biofilm in vitro. In an additional cytotoxicity assay of vB_SurP-PSU3, no significant adverse effects were observed on the tested cell. Based on these findings, the newly isolated phage vB_SurP-PSU3 could be classified as a new member of Andhravirus and could be considered an alternative potential biocontrol agent against S. ureilyticus infections and its biofilm.

Genomic investigation of clinically significant coagulase-negative staphylococci

Introduction. Coagulase-negative staphylococci have been recognized both as emerging pathogens and contaminants of clinical samples. High-resolution genomic investigation may provide insights into their clinical significance.Aims. To review the literature regarding coagulase-negative staphylococcal infection and the utility of genomic methods to aid diagnosis and management, and to identify promising areas for future research.Methodology. We searched Google Scholar with the terms (Staphylococcus) AND (sequencing OR (infection)). We prioritized papers that addressed coagulase-negative staphylococci, genomic analysis, or infection.Results. A number of studies have investigated specimen-related, phenotypic and genetic factors associated with colonization, infection and virulence, but diagnosis remains problematic.Conclusion. Genomic investigation provides insights into the genetic diversity and natural history of colonization and infection. Such information allows the development of new methodologies to identify and compare relatedness and predict antimicrobial resistance. Future clinical studies that employ suitable sampling frames coupled with the application of high-resolution whole-genome sequencing may aid the development of more discriminatory diagnostic approaches to coagulase-staphylococcal infection.

Soaking of autografts with vancomycin is highly effective on preventing postoperative septic arthritis in patients undergoing ACL reconstruction with hamstrings autografts

PURPOSE

To evaluate the impact of local soaking of the autografts with vancomycin during anterior cruciate ligament (ACL) reconstruction on postoperative infection rates.

METHODS

Between 2003 and 2014 (first study period), 1,242 patients underwent ACL reconstruction using autografts, without soaking them in vancomycin solution, while between 2014 and 2019 (second study period) all ACL autografts in 593 patients were soaked in a 5-mg/ml vancomycin solution, in a territory University Hospital. The same standard treatment of perioperative IV antibiotics was applied in both groups.

RESULTS

Postoperative septic arthritis occurred in seven out of 1,242 patients (0.56%) during the first study period. Bone patellar tendon bone autograft was used in 311 (25%) patients, and hamstring tendon autograft was used in the rest 931 (75%) of the study population during this period. All infected cases were male and had a hamstrings graft implanted. There were no postoperative infections (0%) in 593 ACL reconstructions during the second study period. Bone patellar tendon bone autograft was used in 178 (30%) patients while hamstring tendon autograft was used in the rest 415 (70%) of the study population, during this period. Statistical analysis revealed a significantly reduced postoperative infection rate (p = 0.018) between the two reported periods, with the main impact referring to the use of hamstrings autograft (p = 0.031) for the first study period.

CONCLUSIONS

Septic arthritis following ACL reconstruction can be significantly reduced (or even eliminated) by soaking ACL autografts in a 5 mg/ml vancomycin solution. Of note, this strategy seems to be more effective in the setting of hamstring tendon autograft use, since the risk of postoperative knee infection is significantly higher when this type of graft is used.

MLST-Based Analysis and Antimicrobial Resistance of Staphylococcus epidermidis from Cases of Sheep Mastitis in Greece

Staphylococcus epidermidis is an important causal agent of ovine mastitis. A literature search indicated a lack of systematic studies of causal agents of the infection by using multi-locus sequence typing (MLST). The objectives were to analyse MLST-based data and evaluate the antimicrobial resistance of S. epidermidis isolates from ovine mastitis in Greece. The database included 1593 isolates from 46 countries: 1215 of human, 195 of environmental and 134 of animal origin, distributed into 949 sequence types (STs) and cumulatively with 450 alleles therein. Among mastitis isolates, bovine isolates were distributed into 36 different STs and ovine ones into 15 STs. The 33 isolates from ovine mastitis in Greece were in 15 different STs, 6 of these (ST677, ST678, ST700, ST 709, ST710, ST711) assigned for the first time; in addition, 5 alleles (65 for arcC, 59 for aroE, 56 and 57 for gtr and 48 for tpiA) were identified for the first time. The spanning tree of these isolates included 15 nodes and 14 edges (i.e., branches). Among these isolates, 19 showed resistance to antimicrobial agents (tetracycline, penicillin, fucidic adic, erythromycin, clindamycin, cefoxitin). Resistance-related genes (tetK, tetT, msrA, tetM, tetS, ermC, mecA) were detected. There was no association between STs and resistance to antimicrobial agents. Isolates with antimicrobial resistance were recovered more often from flocks where hand-milking was practised.

Antimicrobial Agent Susceptibility and Typing of Staphylococcal Isolates from Subclinical Mastitis in Ewes

Objective was to study susceptibility to antimicrobial agents of 142 staphylococcal isolates from subclinical mastitis in ewes. In total, 41.5% of these were resistant and 5.6% multidrug resistant. More coagulase-negative staphylococci (47.0%) were resistant than Staphylococcus aureus (18.5%) isolates. Resistance was greater to penicillin (22.5%), tetracycline, or ampicillin (18.3%). More biofilm-forming (20.6%) isolates were resistant to tetracycline than nonbiofilm-forming (0.0%) ones. Presence of tetK was associated with presence of icaA in the same strains. Further, 76.6% of resistant isolates versus 57.7% of susceptible ones were recovered immediately postpartum and 23.4% of resistant isolates versus 9.9% of susceptible ones were recovered in farms that practiced routine administration of antimicrobial agents at the end of a lactation period. Most S. aureus (59.3%) were classified in ST133 and most Staphylococcus epidermidis were classified in ST100, ST142, or ST152 (19.0% each). There was no association of sequence types with resistance. Whole genome sequencing showed that, in a Staphylococcus lentus strain, the ermB gene was part of transposon Tn917 integrated into the chromosome; also, a small plasmid was observed in an ermC-carrying Staphylococcus hominis strain and, finally, in an S. aureus and an S. epidermidis strains, small tetK-carrying plasmids (pSau-2716Lar, pSau-3893Lar) of 4.439 kb were found.

Alteration of the cutaneous microbiome in psoriasis and potential role in Th17 polarization

BACKGROUND

Psoriasis impacts 1-3% of the world's population and is characterized by hyper-proliferation of keratinocytes and increased inflammation. At the molecular level, psoriasis is commonly driven by a Th17 response, which serves as a major therapeutic target. Microbiome perturbations have been associated with several immune-mediated diseases such as atopic dermatitis, asthma, and multiple sclerosis. Although a few studies have investigated the association between the skin microbiome and psoriasis, conflicting results have been reported plausibly due to the lack of standardized sampling and profiling protocols, or to inherent microbial variability across human subjects and underpowered studies. To better understand the link between the cutaneous microbiota and psoriasis, we conducted an analysis of skin bacterial communities of 28 psoriasis patients and 26 healthy subjects, sampled at six body sites using a standardized protocol and higher sequencing depth compared to previous studies. Mouse studies were employed to examine dermal microbial-immune interactions of bacterial species identified from our study.

RESULTS

Skin microbiome profiling based on sequencing the 16S rRNA V1-V3 variable region revealed significant differences between the psoriasis-associated and healthy skin microbiota. Comparing the overall community structures, psoriasis-associated microbiota displayed higher diversity and more heterogeneity compared to healthy skin bacterial communities. Specific microbial signatures were associated with psoriatic lesional, psoriatic non-lesional, and healthy skin. Specifically, relative enrichment of Staphylococcus aureus was strongly associated with both lesional and non-lesional psoriatic skin. In contrast, Staphylococcus epidermidis and Propionibacterium acnes were underrepresented in psoriatic lesions compared to healthy skin, especially on the arm, gluteal fold, and trunk. Employing a mouse model to further study the impact of cutaneous Staphylcoccus species on the skin T cell differentiation, we found that newborn mice colonized with Staphylococcus aureus demonstrated strong Th17 polarization, whereas mice colonized with Staphylococcus epidermidis or un-colonized controls showed no such response.

CONCLUSION

Our results suggest that microbial communities on psoriatic skin is substantially different from those on healthy skin. The psoriatic skin microbiome has increased diversity and reduced stability compared to the healthy skin microbiome. The loss of community stability and decrease in immunoregulatory bacteria such as Staphylococcus epidermidis and Propionibacterium acnes may lead to higher colonization with pathogens such as Staphylococcus aureus, which could exacerbate cutaneous inflammation along the Th17 axis.

Coagulase-negative staphylococci

The definition of the heterogeneous group of coagulase-negative staphylococci (CoNS) is still based on diagnostic procedures that fulfill the clinical need to differentiate between Staphylococcus aureus and those staphylococci classified historically as being less or nonpathogenic. Due to patient- and procedure-related changes, CoNS now represent one of the major nosocomial pathogens, with S. epidermidis and S. haemolyticus being the most significant species. They account substantially for foreign body-related infections and infections in preterm newborns. While S. saprophyticus has been associated with acute urethritis, S. lugdunensis has a unique status, in some aspects resembling S. aureus in causing infectious endocarditis. In addition to CoNS found as food-associated saprophytes, many other CoNS species colonize the skin and mucous membranes of humans and animals and are less frequently involved in clinically manifested infections. This blurred gradation in terms of pathogenicity is reflected by species- and strain-specific virulence factors and the development of different host-defending strategies. Clearly, CoNS possess fewer virulence properties than S. aureus, with a respectively different disease spectrum. In this regard, host susceptibility is much more important. Therapeutically, CoNS are challenging due to the large proportion of methicillin-resistant strains and increasing numbers of isolates with less susceptibility to glycopeptides.

Whole-genome sequence of Staphylococcus hominis, an opportunistic pathogen

Staphylococcus hominis is a commensal coagulase-negative species of staphylococci. It has been considered a presumptive and opportunistic pathogen that causes nosocomial infections in humans. Here we present the draft genome sequence of S. hominis ZBW5, a multidrug-resistant strain isolated from a human skin sample, which provides opportunities to understand the mechanism and genetic basis of its pathogenesis.

Antibiotic-resistance Staphylococcus aureus isolated from cow's milk in the Hawassa area, South Ethiopia

BACKGROUND

Quarter milk samples from cows were examined to determine the prevalence of Staphylococcus aureus (SA) and different antibiotic resistant pattern were determined in a cross-sectional study design.

OBJECTIVE

The objective of this study was to isolate Staphylococcus aureus from samples of cow's milk obtained from Hawassa area and to determine their antibiotic susceptibility patterns.

METHOD

A total of 160 milk (CCP1-CCP5) samples were collected and screened for the presence of S. aureus. Gram staining, oxidase, catalase, DNase, haemolysis and coagulase tests were employed for bacterial identification.

RESULTS

All the samples were contaminated with S. aureus. A total of 78 S. aureus isolates were obtained during this study. The levels of contamination with S. aureus were higher in milk obtained from CCP1, CCP2, CCP3, CCP4 and CCP5 at Hawassa area farms (18.0%, 25.6%, 27.0%, 21.8% and 7.7%) respectively. A large percentage of the S. aureus isolates (25.6% and 27.0%) were from CCP2 and CCP3. All strains were resistant to Penicillin G (PG) (10 μg), Ampicillin (AP) (10 μg), Amoxicillin-Clavulanic acid (AC) (30 μg), Ciprofloxacin (CIP) (5 μg), Erythromycin (E) (15 μg), Ceftriaxone (CRO) (30 μg), Trimethoprime-Sulfamethoxazole (TMP-SMZ) (25 μg) Oxacillin (Ox) (1 μg) and Vancomycin (V) (30 μg), 67.9%, 70.9%, 30.9%, 0%, 32.1%, 23.1%, 7.7%, 60.3% and 38.5% respectively.

CONCLUSION

The proportion of isolates resistant to CIP, TMP-SMZ, CRO, AC, E and V were low compared to AP, PG and Ox. S. aureus is normally resident in humans; therefore, the S. aureus present in the cow's milk may have resulted from transmission between the two species, emphasizing the need to improve sanitary conditions in the milking environment.

Risk of colonization or gene transfer to owners of dogs with meticillin-resistant Staphylococcus pseudintermedius

To determine the zoonotic risk from meticillin-resistant staphylococcal species or transfer of resistance genes between dogs with pyoderma and their owners, 25 dog-owner pairs were studied. Cultures were obtained from the dog's lesions and the owner's nasal cavity on the initial visit. Staphylococcus isolates were identified and antimicrobial susceptibility tests were performed by the Kirby-Bauer disk diffusion method. Presence of the mecA gene was determined by PCR. Staphylococcal Cassette Chromosome (SCCmec) typing was performed by multiplex PCR. Eighteen dogs had a meticillin-resistant staphylococcal species, with meticillin-resistant S. pseudintermedius (MRSP) isolated from 15 dogs. MRSP was isolated from two owners of dogs with MRSP skin infections. Both organisms had the same susceptibility pattern and SCCmec type. MRSP was not isolated from the owners after treating both dogs for 1 month. At least one coagulase-negative Staphylococcus spp. (CoNS) was isolated from each owner, with meticillin resistance found in 16 (64%) of the isolates. The mecA gene was identified in all but two of the meticillin-resistant Staphylococcus spp. Multiplex PCR identified SCCmec type V in all MRSP. The mecA gene-possessing CoNS isolates from owners contained either SCCmec type IVa or IVc. In conclusion, MRSP colonization of owners appeared to be uncommon and transient. Human nasal carriage of meticillin-resistant CoNS was common, but the SCCmec types were different from those in the canine MRSP isolates. Owners do not appear to be at great risk of zoonotic transfer of organisms or antimicrobial resistance genes from dogs with MRSP infections, but the findings should be confirmed with a much larger cohort.

Purulent flexor tenosynovitis: factors influencing the functional outcome

This retrospective study aimed to evaluate the factors that influence the final outcome of treatment of purulent flexor tenosynovitis, viz. delay in treatment, severity of the condition, the infecting pathogen and the method of treatment. Of 41 patients with this condition treated by drainage and irrigation through two small incisions (16) and wide incision (25), 16 were treated after a delay. Continuous postoperative irrigation was applied in 26 patients. Re-operation was necessary in 11 patients. In most cases, Staphylococcus aureus was detected. The results were excellent in 32 cases and the mean Disabilities of the Arm, Shoulder and Hand score was 8.1. Irrigation through small incisions and continuous postoperative irrigation decreased the probability of an unfavourable outcome. Delayed treatment and infections with specific pathogens led to a worse outcome. Early diagnosis of purulent flexor tenosynovitis followed by drainage through small incisions and continuous postoperative irrigation appear, from this retrospective review, to lead to the best functional outcome.

Autograft contamination during preparation for anterior cruciate ligament reconstruction

BACKGROUND

The autograft preparation process for anterior cruciate ligament reconstruction has a potential for graft contamination. The purpose of this study was to evaluate the possibility of contamination of the bone-patellar tendon-bone and hamstring tendon autograft during preparation for anterior cruciate ligament reconstruction.

METHODS

A primary isolated reconstruction of the anterior cruciate ligament with use of bone-patellar tendon-bone autograft (thirty patients) and hamstring tendon autograft (thirty patients) was performed in a prospective, consecutive series of patients. Three tissue samples were obtained for culture from each graft at different time-intervals during the graft preparation. In addition, the erythrocyte sedimentation rate and the C-reactive protein level were evaluated preoperatively and on the third, seventh, and twentieth postoperative days, and the clinical course of all patients was monitored.

RESULTS

The time needed for graft preparation was significantly longer for hamstring autografts (nineteen minutes) than for bone-patellar tendon-bone autografts (ten minutes) (p = 0.032). In the hamstring group, cultures of graft tissue from four patients (13%) were positive for bacteria. In the bone-patellar tendon-bone group, cultures of graft tissue from three patients (10%) were positive for bacteria; the difference between groups was not significant (p = 0.923). No patient had development of a postoperative infection. There were no differences between patients with a contaminated graft and those with an uncontaminated graft with regard to postoperative changes in the erythrocyte sedimentation rate or the C-reactive protein level at all time-intervals.

CONCLUSIONS

A high rate (12%) of autograft contamination can be expected during autograft preparation for anterior cruciate ligament reconstruction. The contamination rate is almost equal for both bone-patellar tendon-bone and hamstring tendon autografts. We could not identify an association between contaminated grafts implanted in the knee and postoperative inflammatory markers such as the erythrocyte sedimentation rate and the C-reactive protein level.

Clonal relatedness of methicillin-resistant coagulase-negative staphylococci in the haemodialysis unit of a single university centre in Greece

BACKGROUND

Coagulase-negative staphylococci (CoNS) are frequently encountered pathogens in hospital environment. Dialysis patients, often carrying central venous catheters, are prone to CoNS infections. Methicillin-resistant (MR) staphylococci in hospitals are resistant to multiple antibiotics and may cause an overall increase in the incidence of staphylococcal infections rather than simply replacing the more susceptible strains. The aim of this study was to evaluate the antimicrobial resistance and the clonal relatedness of all clinically significant CoNS isolates recovered from haemodialysis patient infections treated in a tertiary care centre, the University Hospital of Larissa, in central Greece. In addition, the CoNS isolates from carriers among health-care workers of the local haemodialysis unit were tested.

METHODS

All staphylococci recovered from chronic haemodialysis patients who developed CoNS infections according to Herwaldt criteria in the University Hospital of Larissa, from October 2002 to October 2005, were included. In addition, isolates from the palms and the nasal mucosa of the nursing and medical personnel in the haemodialysis unit were also collected. Isolates were identified and tested for antimicrobial resistance by conventional microbiological methods. The clonal relationship of both patients' and carriers' isolates was tested by pulsed-field gel electrophoresis (PFGE) analysis.

RESULTS

Forty-two CoNS isolates were recovered from clinical culture specimens of patients hospitalized for various reasons. In 37 out of 42 CoNS isolates, methicillin resistance was determined. The majority of the MR Staphylococcus epidermidis isolates from patients belonged to one main clone (27 out of 32), arbitrarily named clone z. Clone z was also found to colonize 40% of the haemodialysis unit personnel.

CONCLUSIONS

The high prevalence of clone z emphasizes the great capacity of CoNS to colonize patients with central venous catheters such as haemodialysis patients and personnel. This emphasizes the need for the establishment of control and prevention measures.

Automated systems in the identification and determination of methicillin resistance among coagulase negative staphylococci

Coagulase-negative staphylococci (CoNS) are an important cause of nosocomial bacteremia, specially in patients with indwelling devices or those submitted to invasive medical procedures. The identification of species and the accurate and rapid detection of methicillin resistance are directly dependent on the quality of the identification and susceptibility tests used, either manual or automated. The objective of this study was to evaluate the accuracy of two automated systems--MicroScan and Vitek--in the identification of CoNS species and determination of susceptibility to methicillin, considering as gold standard the biochemical tests and the characterization of the mecA gene by polymerase chain reaction, respectively. MicroScan presented better results in the identification of CoNS species (accuracy of 96.8 vs 78.8%, respectively); isolates from the following species had no precise identification: Staphylococcus haemolyticus, S. simulans, and S. capitis. Both systems were similar in the characterization of methicillin resistance. The higher discrepancies for gene mec detection were observed among species other than S. epidermidis (S. hominis, S. saprophyticus, S. sciuri, S. haemolyticus, S. warneri, S. cohnii), and those with borderline MICs.

Isolation and molecular characterization of Staphylococcus sciuri in the hospital environment

Staphylococcus sciuri is a principally animal-associated bacterial species, but its clinical relevance for humans is increasing. Our study aimed to provide the first insight into the prevalence of this bacterium in a hospital environment. A 3-month surveillance was conducted in a hospital located in Belgrade, Serbia, and 1,028 samples taken from hands of medical personnel, medical devices, and various hospital surfaces were screened for S. sciuri presence. In total, 108 isolates were obtained, which resulted in a relatively high rate of colonization (10.5%). These isolates, along with 7 S. sciuri strains previously isolated in the same hospital (n = 115), were phenotypically and genotypically characterized. Antimicrobial susceptibility testing revealed that 73% of the strains were resistant to one or more antibiotics, with 4.3% strains displaying multiresistance. Examination of 16S-23S ribosomal DNA intergenic spacer length polymorphism identified the strains at the subspecies level, and 74 (64.3%) strains of S. sciuri subsp. sciuri, 37 (32.2%) strains of S. sciuri subsp. rodentium, and 4 (3.5%) strains of S. sciuri subsp. carnaticus were established. Pulsed-field gel electrophoresis (PFGE) analysis showed 21 distinct pulsotypes, including 17 main types and 4 subtypes. One dominant cluster with 62 strains was found, while 19 (90.5%) of the PFGE types and subtypes identified had 5 or fewer strains. The predominance of small PFGE clusters suggests that the ubiquitous presence of S. sciuri in the outside environment presents the continuous source for colonization of the hospital environment. The presence of one dominant PFGE cluster of strains indicates that some S. sciuri strains may be capable for adaptation to hospital environment conditions and continuous existence in this environment.

In vitro combined bactericidal activity of cefpirome and glycopeptides against glycopeptides and oxacillin-resistant staphylococci

Infections caused by coagulase-negative staphylococci are becoming increasingly important, particularly those of nosocomial origin, as the organisms are frequently multi-resistant. New antimicrobial strategies are needed. The bactericidal activity of a combination of cefpirome with either vancomycin or teicoplanin against 12 strains of methicillin-resistant staphylococci with a decreased susceptibility to teicoplanin was determined in vitro by a time killing method. Strains Mu3 and Mu50 of Staphylococcus aureus were also studied. Cefpirome (0.125-0.5 x MIC) combined with vancomycin (0.25-1 x MIC) or teicoplanin (0.125-1 x MIC) acted synergically against 12 isolates over 18 h in most cases. A synergistic killing effect was also observed with the Mu3 and Mu50 strains of glycopeptide-intermediate S. aureus but over a longer period.

Isolation and molecular characterization of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus associated with skin and soft-tissue infections

The isolation, molecular identification and genotyping of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus from skin and soft-tissue infections are reported. Accurate and full identification of three coagulase-negative staphylococcal isolates was achieved using PCR, while the API STAPH method failed to identify an isolate of S. haemolyticus fully. The PCR assay, which detects polymorphism in the 16S-23S rRNA spacer region, is shown to be potentially useful for rapid and accurate identification of coagulase-negative staphylococci. Identical PFGE type and antibiotic-resistance profiles of two methicillin-resistant S. haemolyticus isolates in this study suggest the existence of a multiresistant community clone.

Evaluation of a multilocus sequence typing system for Staphylococcus epidermidis

Staphylococcus epidermidis is a significant cause of nosocomial disease. However, the taxonomy of this pathogen, particularly at subspecies level, is unclear. A multilocus sequence typing (MLST) scheme has therefore been investigated as a tool to elucidate taxonomic relationships within this group, based on genetic relatedness. DNA sequences for internal fragments of seven housekeeping genes were compared in 47 geographically and temporally diverse S. epidermidis isolates that were obtained from clinical infections. Twenty-three different allelic profiles were detected; 17 of these were represented by single strains and the largest profile group contained 17 isolates. Diversity of the same collection of isolates was investigated by using PFGE of SmaI-digested genomic DNA to test the discrimination and validity of the MLST approach. Isolates within the largest profile group were resolved into four distinct PFGE clusters on the basis of their SmaI digest patterns. Isolates within other profile groups that contained multiple isolates had matching PFGE SmaI patterns within each group. It appears that MLST is an effective method for grouping S. epidermidis strains at the subspecies level; however, it is not as discriminatory as it has been for other species for which MLST schemes have been established and, used alone, would not be a useful method for epidemiological studies. In addition, it was demonstrated that this method was effective for confirming the identity of S. epidermidis CoNS (coagulase-negative) isolates.

Application of molecular typing methods to characterize nosocomial coagulase-negative staphylococci collected in a Greek hospital during a three-year period (1998-2000)

A total of 143 methicillin-resistant coagulase-negative staphylococci (MR-CNS) collected between 1998 and 2000 at the University Hospital of Patras, Greece, were characterized by antibiogram and genomic typing to define the clonal types endemic in this hospital and their evolution during the 3-year period. These isolates corresponded to 93 methicillin-resistant Staphylococcus epidermidis (MRSE) and 50 other MR-CNS, which were isolated from patients in different wards, exclusively from blood and catheter tips cultures. Pulsed-field gel electrophoresis (PFGE) of SmaI macrofragments and hybridization of ClaI digests with mecA and murE DNA probes were performed. The application of these methodologies demonstrated the existence, persistence and spread of MRSE, MR-Staphylococcus haemolyticus, and MR-Staphylococcus hominis clones in this hospital, whereas the SmaI/murE hybridization pattern was shown to be a valuable tool for the MRSE identification.

Rapid screening and identification of methicillin-resistant Staphylococcus aureus from clinical samples by selective-broth and real-time PCR assay

A screening method for methicillin-resistant Staphylococcus aureus (MRSA) by using selective broth and real-time PCR (broth-PCR) was developed and evaluated. The samples (n = 304) were cultured in the broth overnight, followed by nuc gene detection by real-time PCR. nuc-negative samples were further checked for the presence of nuc amplification inhibitors by a PCR internal inhibitor assay. nuc-positive samples and nuc-negative samples with PCR inhibitors were cultured onto plates and processed further. The diagnostic values for this MRSA screening method were 93.3% sensitivity, 89.6% specificity, 31.8% positive predictive value, and 99.6% negative predictive value. The application of the broth-PCR method will be able to report most of the negative samples (258 of 289 [89.3%]) on the next morning and can save as much as 84.9% (258 of 304) of the labor and cost spent on processing the nuc-negative specimens on plates. In the study, all the samples were processed in parallel by the broth enrichment method and the plating method for comparison. To identify MRSA, the isolated oxacillin-resistant S. aureus strains were tested by a duplex real-time PCR targeting the mecA gene and the nuc gene. A collection of MRSA, methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, and methicillin-susceptible Staphylococcus epidermidis strains and a panel of standard strains of 11 bacterial species other than S. aureus were also tested by this method, which was proved to be a valuable tool for MRSA identification in a routine microbiological laboratory.

Staphylococcal resistance revisited: community-acquired methicillin resistant Staphylococcus aureus--an emerging problem for the management of skin and soft tissue infections

PURPOSE OF REVIEW

In the community non-localized or deep staphylococcal skin and soft tissue infections are typically managed with beta-lactamase stable penicillins. The aims of this review are (1) to evaluate the evidence for the emergence of new strains of community-acquired methicillin resistant Staphylococcus aureus (MRSA), (2) to identify the reasons for their significant association with cutaneous infections, and (3) to consider how they arose and how big a threat they pose to the management of such infections outside hospitals.

RECENT FINDINGS

MRSA are emerging as significant community pathogens, especially in previously healthy children with no recognizable risk factors, and are predominantly associated with skin and soft tissue infections (especially abscesses and cellulitis). When present, risk factors are generally similar to those for infection with methicillin susceptible S. aureus. The MRSA isolates associated with such infections may not be entirely 'new', but could represent the displacement of some hospital clones (e.g. EMRSA-15 or variants thereof) to the community as well as the de-novo generation of novel MRSA clones by multiple horizontal transmissions of the mecA gene into methicillin susceptible S. aureus with different genetic backgrounds, some of which are already circulating globally. Community-acquired MRSA from diverse locations are non multiresistant and almost always contain the novel type IV SCCmec commonly found in coagulase-negative staphylococci, but also in hospital-associated gentamicin susceptible MRSA from France, the paediatric clone and in EMRSA-15.

SUMMARY

More local data on CA-MRSA infections are needed so that dermatologists and community physicians can assess the risk of such infections amongst their patients and avoid the inappropriate administration of beta-lactams. No simple change in prescribing practices will entirely alleviate selective pressure for the spread of community-acquired MRSA and not exacerbate resistance in pyogenic streptococci, commonly found together with S. aureus in skin and soft tissue infections. The importance of hygiene in preventing the spread of community-acquired MRSA in the community must be reemphasized.