Meticillin-resistant Staphylococcus Aureus Strains Research Articles

Impact of control measures including decolonization and hand hygiene for orthopaedic surgical site infection caused by MRSA at a Japanese tertiary-care hospital

Meticillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen in orthopaedic surgical site infections (SSIs). However, few studies have investigated the transmission process of orthopaedic MRSA SSI. To investigate the transmission process of orthopaedic MRSA SSI using epidemiological and molecular analyses and to determine a method to prevent MRSA SSI innosocomial orthopaedic surgery. Active MRSA surveillance, preoperative decolonization and contact precautions for MRSA-positive cases was performed at our institution. Changes in epidemic strains were evaluated and the possibility of transmission from patients in an orthopaedic ward of a Japanese tertiary-care hospital was assessed by genotyping stored MRSA strains. In addition, data on the prevalence of MRSA SSI, MRSA colonization, and use of an alcohol antiseptic agent (mL/patient-days) during 2005-2022 were retrospectively assessed. SCCmec type II strain in the SSI group decreased over time, associated with fewer outbreaks. Even during a period of high infection rates, no cases of transmission-induced SSI from nasal MRSA carriers were identified. The infection rate correlated negatively with the use of an alcohol antiseptic agent (r = -0.82; P < 0.0001). Two cases among five nasal carriers developed MRSA SSI caused by strains different from those related to nasal colonization. The infection control measures for transmission from the hospital reservoirs including strict adherence to hand hygiene and decolonization of carriers is likely to be important for the prevention of orthopaedic MRSA SSI. However, the need for contact precautions for decolonized nasal carriers might be low.

Whole-genome sequencing analysis of molecular epidemiology and silent transmissions causing meticillin-resistant Staphylococcus aureus bloodstream infections in a university hospital

The emergence of novel genomic-type clones, such as community-associated meticillin-resistant Staphylococcus aureus (MRSA) and livestock-associated MRSA, and their invasion into hospitals have become major concerns worldwide; however, little information is available regarding the prevalence of MRSA in Japan. Whole-genome sequencing (WGS) has been conducted to analyse various pathogens worldwide. Therefore, it is important to establish a genome database of clinical MRSA isolates available in Japan. A molecular epidemiological analysis of MRSA strains isolated from bloodstream-infected patients in a Japanese university hospital was conducted using WGS and single-nucleotide polymorphism (SNP) analysis. Additionally, through a review of patients' clinical characteristics, the effectiveness of SNP analysis as a tool for detecting silent nosocomial transmission that may be missed by other methods was evaluated in diverse settings and various time points of detection. Polymerase-chain-reaction-based staphylococcal cassette chromosome mec (SCCmec) typing was performed using 135 isolates obtained between 2014 and 2018, and WGS was performed using 88 isolates obtained between 2015 and 2017. SCCmec type II strains, prevalent in 2014, became rare in 2018, whereas the prevalence of SCCmec type IV strains increased from 18.75% to 83.87% of the population, and became the dominant clones. Clonal complex (CC) 5 CC8 and CC1 were detected between 2015 and 2017, with CC1 being dominant. In 88 cases, SNP analyses revealed nosocomial transmissions among 20 patients which involved highly homologous strains. Routine monitoring of MRSA by whole-genome analysis is effective not only for gaining knowledge regarding molecular epidemiology, but also for detecting silent nosocomial transmission.

Sensitivity of Strains of Meticillin Resistant Staphylococcus aureus (MRSA), Isolated from Bacterial Infections in the District of Abidjan

Staphylococcus aureus is one of the most prevalent human pathogens causing a wide range of bacterial infections. Since the introduction of methicillin as a treatment option, the emergence and subsequent spread of methicillin-resistant Staphylococcus aureus (MRSA) strains has become a global concern. The objective of this study is to determine the prevalence of MRSA isolated from bacterial infections in Abidjan as well as their resistance profile to certain antibiotics. One hundred and twenty-four (124) strains of Staphylococcus aureus from the University Hospital of Cocody and various clinics isolated from various biological products were included in our study. The antibiogram on Mueller-Hinton agar was repeated by testing cefoxitin for the revelation of MRSA. Several other families of antibiotics have also been tested with the aim of observing resistance associated with MRSA. Among the one hundred and twenty-four strains of Staphylococcus aureus analyzed, 75 present, after phenotypic interpretation, a profile of resistance to methicillin (MRSA strains), i.e. 60.48%. These MRSA were isolated from blood culture (26.67%), purulent secretions (44%), urine (14.67%), sperm culture (1.33%), wound (4%), pleural fluid (4%), stool (1.33%) and tip of urinary catheter (4%); and came from neonatology, surgery, pneumology, pediatrics, outpatient, medicine, emergency, rheumatology, ENT, neurology, traumatology and gastroenterology departments. A variable proportion of MRSA strains express resistance to other families of antibiotics including aminoglycosides (23.32%), fluoroquinolones (85.33%), erythromycin (27.64%), clindamycin (24.19%) and tetracycline (20.73%). The increasing prevalence of multidrug-resistant Staphylococcus aureus, limiting the therapeutic options available against this pathogen, has become an issue of concern worldwide. Thus, the establishment of a relevant resistance monitoring policy to better control the circulation of multi-resistant strains is necessary.

Risk factors for meticillin-resistant Staphylococcus aureus (MRSA) carriage in MRSA-exposed household pets.

Household pets can carry meticillin-resistant Staphylococcus aureus (MRSA) introduced to the home by their human companions. Specific factors promoting pet carriage of this pathogen have not been fully elucidated. This study evaluated MRSA cultured from pets and the home environment in households where a human infected with MRSA had been identified, and aimed to determine potential risk factors for pet MRSA carriage. Humans diagnosed with community-associated MRSA (CA-MRSA) skin or soft-tissue infection (SSTI) in the mid-Atlantic United States were identified. One hundred forty-two dogs and cats from 57 affected households were identified of which 134 (94.4%) pets and the household environment were sampled for bacterial culture, PCR confirmation and spa-typing for MRSA strain determination. Samples were obtained 3 months later from 86 pets. At baseline, 12 (9.0%) pets carried MRSA. Potential risk factors associated with carriage included pet bed (environmental) MRSA contamination, flea infestation and prior antimicrobial use in the pet. Pets tended to carry human-adapted MRSA strains and spa-types of MRSA isolates cultured from pets were concordant with strains cultured from the home environment in seven of eight homes (87.5%) at baseline. Results may inform risk-based veterinary clinical recommendations and provide evidence for selective pet testing as a possible alternative to early removal of pets from the homes of humans infected with MRSA. MRSA contamination of the home environment is likely an important risk factor for pet MRSA carriage, and household interventions should be considered to reduce risk of MRSA carriage in exposed pets.

Misidentification of meticillin-resistant Staphylococcus aureus by the Cepheid Xpert MRSA NxG assay, the Netherlands, February to March 2021.

We describe two false-negative results in the detection of meticillin-resistant Staphylococcus aureus (MRSA) of sequence type 398 and spa type t011 using the Cepheid Xpert MRSA NxG assay. The isolates were recovered in late February and early March 2021 from two patients in different hospitals in the northern Netherlands. Variations between the two isolate genomes indicate that this MRSA strain might have been spreading for some time and could have disseminated to other regions of the Netherlands and other European countries.

Çeşitli Klinik Örneklerden Izole Edilen Staphylococcus aureus Suşlarında Metisilin Direncinin Araştırılmasında Konvansiyonel PCR Yöntemi ile Sefoksitin Disk Difüzyon, Otomatize Sistem ve Chromogenic MRSA Agar Yöntemlerinin Karşılaştırılması

Meticillin-resistant Staphylococcus aureus (MRSA) is one of the most important infectious agents. Therefore, fast and accurate diagnosis of MRSA is utmost important. Although mecA gene detection by PCR is reference method, conventional methods are preferred in routine practices due to simplicity. As conventional methods last 48-96 hours, several chromogenic media have been developed. Our objective was to compare the methods used for meticillin resistance detection with PCR. Forty-eight S. aureus strains isolated from various clinical specimens were included. Of the 48 S. aureus strains, 19 were mecA gene-positive and 29 were negative. mecA gene-positive 19 strains were also meticillin-resistant by automated system and disk diffusion. On chromogenic agar, 15 of 19 MRSA strains were meticillin-resistant and 4 were meticillin-sensitive. Twentynine mecA gene-negative strains were susceptible to meticillin by automatized system and disk diffusion. Among 29 mecA gene-negative MSSA strains inoculated on chromogenic agar, 17 were methicillin-resistant. According to our study, chromogenic media would be ineffective to detected to meticillin-resistance because of low sensitivity and specificity in routine.

Methicillin-Resistant Staphylococcus Strains Isolated from Adult Intensive Care Units with E-test MIC Values of Different Antibiotic Research

Objective: Nasocomial infections are major health problems due to their high morbidity and mortality, prolonged hospital duration and higher treatment costs. Methicillin-resistant staphylococcus species became one of the leading bacteria causing nasocomial infections especially in intensive care units, recently. The minimum inhibitory concentration value of an antibiotic gives the concentration of antibiotic needed to inhibit the bacteria in the infection area. Careful monitoring of minimal inhibitory concentration (MIC) values is necessary especially during long-term treatments of meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-resistant coagulase-negative staphylococci (MRCoNS) infections 1,2 . Increasing antibiotic resistance in methicillin-resistant staphylococci, has led to the need for different antibiotics. Methods: A total of 60 meticillin-resistant staphylococci strains isolated in Microbiology Laboratory of Dicle University Hospital, from clinical specimens of patients in adult Intensive Care Units (ICUs) between April 2013 and March 2014 were included in this study. After identification with conventional and automated system, the antibiotic susceptibility rates of vancomycin, teicoplanin, daptomycin, linezolid, quinupristin/dalfopristin, tigecycline, ceftaroline were determined by E-test method. Results: The majority of the samples (26.7%) were sent from Pulmonary Diseases and Tuberculosis intensive care unit and the blood samples were the most common materials (80%) . All staphylococcal strains in our study were determined as susceptible to vancomycin, daptomycin, linezolid, teicoplanin and tigecycline. One (1.6%) MRCoNS isolate was resistant to quinupristin/dalfopristin while 11 (36.6%) of the MRSA isolates were resistant to ceftaroline. In comparison with the MIC values of MRSA and MRCoNS, only tigecycline was significantly different. Thirty MRSA strains were evaluated in terms of vancomycin-intermediate Staphylococcus aureus /heteroresistant vancomycin-intermediate Staphylococcus aureus (VISA/hVISA) with macro E-test method; any VISA/hVISA isolate was not detected. Antibiotic concentrations below the MIC level, not only leads to treatment failure but also causes mutant bacteria to appear. In order to control the resistance to antibiotics in the treatment of infections due to MRSA and MRCoNS agents, the clinician should be notified of the MIC values of the drugs and the treatment should be planned accordingly. VISA/hVISA isolates should be considered in treatment failures of infections due to MRSA which are in vitro susceptible to vancomycin. Further testing is needed to detect these isolates. Despite the fact that ceftaroline is not a drug used in our country, the high resistance rate in our study is remarkable. This situation may be due to the intensive use of other beta-lactam antibiotics. Therefore, antibiotic susceptibility results should be taken into consideration during planning the treatment of infections. The high average MIC values of tigecycline in MRCoNS infections should also be monitored carefully

Biofilm formation and antibiotic resistance in meticillin-resistant and meticillin-sensitive Staphylococcus aureus isolated from burns.

To investigate the relationship between biofilm formation and antibiotic resistance patterns in meticillin-resistant and meticillin-sensitive Staphylococcus aureus, isolated from burns. In a cross-sectional study, pus/wound swab samples were obtained from burns. Presence of Staphylococcus aureus was confirmed, and biofilm formation-related icaABCDR and eta, etb genes were detected by polymerase chain reaction. Biofilm formation assay was assessed using the microtiter plate method. Antibiotic resistance was performed using the disk diffusion method and minimum inhibitory concentration. A total of 95 patients with burns were recruited. Of the 95 wounds swabbed, Staphylococcus aureus was identified in 50 (62.5%), and 47 (94%) isolates capable of producing biofilm. Biofilm production levels were classed as 'strong' (n=29; 58%), 'moderate' (n=11; 22%), 'weak' (n=7; 14%) and 'non-biofilm forming' (n=3; 6%). There was an almost even split between isolates identified as meticillin-resistant Staphylococcus aureus (MRSA), n=24 (48%), and meticillin-sensitive Staphylococcus aureus (MSSA) n=26 (52%). The prevalence of the icaA, icaB, icaC, icaD and icaR genes among the studied isolates were 96%, 80%, 80%, 96% and 84%, respectively. The prevalence of eta and etb genes in isolates were 84% and 92%, respectively. Biofilm producing isolates of Staphylococcus aureus showed greater multidrug resistance than non-biofilm producers. In our study, a high rate of biofilm formation and antimicrobial drug resistance was seen. Our results highlight the alarming levels of antimicrobial resistance among MRSA strains and important data about the prevalence of eta and etb genes in Staphylococcus aureus strains isolated from burn patients in this study.

Successful termination of sustained transmission of resident MRSA following extensive NICU refurbishment: an intervention study

Neonatal sepsis is a leading cause of morbidity and mortality in neonatal units worldwide. Meticillin-resistant Staphylococcus aureus (MRSA) has become a leading causative pathogen. Many neonatal units experience endemic colonization and infection of their infants, which is often very challenging to successfully eradicate. To assess the impact of neonatal unit refurbishment and redesign on endemic MRSA colonization and infection. A retrospective review was carried out over an eight-year period in a 14-cot, level 2-3 neonatal unit in University Hospital Galway, a large university teaching hospital in the West of Ireland. Surveillance, colonization, and infection data for a four-year period pre and four-year period post neonatal unit refurbishment are described. Clinical and microbiological data were collected on all MRSA-colonized and -infected infants between 2008 and 2015. Molecular typing data are available for MRSA isolates. An interrupted time-series design was used, with unit refurbishment as the intervention. Our neonatal unit had a pattern of sustained transmission of endemic resident MRSA strains which we could not eradicate despite repeated standard infection control interventions. Complete unit refurbishment led to successful termination of sustained transmission of these strains. Colonization decreased and no infants were actively infected post refurbishment of the unit. We report successful termination of sustained transmission of endemic strains of MRSA from our neonatal unit following complete unit redesign and refurbishment.

Control of healthcare- and community-associated MRSA: recent progress and persisting challenges.

Healthcare adapted meticillin-resistant Staphylococcus aureus (MRSA) has spread to hospitals around the world over 50 years. More recently, other strains of MRSA have emerged with the ability to spread in the community and infect otherwise healthy individuals. Morbidity and mortality associated with MRSA remains high and its control in both the healthcare and community setting has proven challenging. Pubmed (Medline). The use of targeted screening and decolonization, hand hygiene and antimicrobial stewardship is supported by the most robust studies, though many studies have implemented bundles for effective healthcare-associated (HA)-MRSA control. Universal screening, universal decolonization and contact precautions for HA-MRSA control are supported by less evidence. Some interventions may not be cost-effective. Contact precautions may be associated with potential for patient harm. Evidence for effective control community acquired (CA)-MRSA is largely lacking. Programmes that focus on implementing bundles of interventions aimed at targeting HA-MRSA are more likely to be effective, with an emphasis on hand hygiene as a key component. Control of CA-MRSA is likely to be more difficult to achieve and relies on prevalence, risk factors and community healthcare interactions on a broader scale. Further research in the area of CA-MRSA in particular is required. Antimicrobial stewardship for both CA and HA-MRSA is promising, as is the role of whole genome sequencing in characterizing transmission. However, further work is required to assess their long-term roles in controlling MRSA. With many institutions applying widespread use of chlorhexidine washes, monitoring for chlorhexidine resistance is paramount to sustaining efforts at controlling MRSA.

Genomic characterization of a paediatric MRSA outbreak by next-generation sequencing

Twelve strains of meticillin-resistant Staphylococcus aureus (MRSA) isolated during a suspected outbreak in a paediatric intensive care unit were analysed by whole-genome sequencing (WGS). To define the clonality of MRSA strains to a high discriminative power, and to evaluate the presence of genetic determinants responsible for antibiotic resistance and virulence. Ten out of 12 strains belonged to multi-locus sequence type ST2625, while the other two strains were ST8. Among the ST2625 strains, analysis based on 1126 genes showed that they were clonal, sharing more than 98.3% of allelic identities, and one strain was isolated from a healthcare worker. All ST2625 strains were characterized by the SCC-Mec cassette IVa, and resistoma analysis indicated correspondence between phenotypic and genotypic characteristics. The study of 63 genes associated with virulence was correlated with the pattern of clonality shown. This analysis confirmed the occurrence of an outbreak. As such, standard infection control measures were strictly enforced, and this led to prompt termination of the outbreak.

Spa typing and identification of pvl genes of meticillin-resistant Staphylococcus aureus isolated from a Libyan hospital in Tripoli.

The purpose of the study was to investigate the molecular characteristics of meticillin-resistant Staphylococcus aureus (MRSA) isolated from clinical sources in Tripoli, Libya. A total of 95 MRSA strains collected at the Tripoli medical Centre were investigated by spa typing and identification of the Panton-Valentine Leukocidin (pvl) genes. A total of 26 spa types were characterized and distributed among nine clonal complexes; CC5 (n=32), CC80 (n=18), CC8 (n=17) and CC22 (n=12) were the most prevalent clonal complexes. In total, 34% of the isolates were positive for PVL. This study demonstrated the presence of CA-MRSA and pvl positive strains in hospital settings and underlines the importance of using molecular typing to investigate the epidemiology of MRSA. Preventative measures and surveillance systems are needed to control and minimize the spread of MRSA in the Libyan health care system.

The ability of a colloidal silver gel wound dressing to kill bacteria in vitro and in vivo

Inhibiting bacterial biofilms is of major significance for proper wound healing. The choice of the dressing material plays a key role, as bacteria can live in dressings and keep reinfecting the wound. This study examines the effectiveness of a colloidal silver gel (Ag-gel) wound dressing in inhibiting the growth of bacteria in a mouse wound model. Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and two different meticillin-resistant Staphylococcus aureus (MRSA) strains were examined. Bacteria were measured in vitro on the dressing, and in vivo studies were carried out to analyses both the dressing and the infected tissue. Using colony-forming unit (CFU) assays, over 7 logs of inhibition (100%) were found for Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii for the Ag-gel dressing when compared with the control dressing. In vivo, complete inhibition was observered for the three most common bacteria on the Ag-gel dressing and the tissue under that dressing. These results were confirmed by an in vivo live imaging system. However, with MRSA strains, only 2-3 logs of inhibition were recorded. The Ag-gel was effective in preventing biofilm infections caused by both Gram-negative and Gram-positive bacteria.

Screening for a Potent Antibacterial Peptide to Treat Mupirocin-Resistant MRSA Skin Infections

Mupirocin is the first-line topical antibacterial drug for treating skin infections caused primarily by meticillin-resistant Staphylococcus aureus (MRSA). Its widespread use since its introduction more than 30 years ago has resulted in the global emergence of mupirocin-resistant strains of MRSA. Antimicrobial peptides (AMPs) are a promising class of antibacterial compounds that can potentially be developed to replace mupirocin due to their rapid membrane-targeting bactericidal mode of action and predicted low propensity for resistance development. Herein, we conducted and compared the antibacterial activities of 61 AMPs between 3 and 11 residues in length reported in the literature over the past decade against mupirocin-resistant MRSA. The most potent AMP, 11-residue peptide 50, was selected and tested against a panel of clinical isolates followed by a time-kill and a human dermal keratinocyte cytotoxicity assay. Lastly, peptide 50 was formulated into a topical spray which showed strong in vitro bactericidal effects against mupirocin-resistant MRSA. Our results strongly suggest that peptide 50 has the potential to be further developed into a new class of topical antibacterial agent for treating drug-resistant MRSA skin infections.

Molecular analysis of meticillin-resistant Staphylococcus aureus strains isolated from different types of infections from patients hospitalized in 12 regional, non-teaching hospitals in southern Poland

Accumulated data indicate that meticillin-resistant Staphylococcus aureus (MRSA) infections are associated with a worse prognosis than methicillin-susceptible S.aureus infections. To assess the epidemiological profile of S.aureus infections and the genetic diversity of clinical strains of MRSA in 12 hospitals in southern Poland. Samples from bloodstream infections, pneumonia, and skin and soft tissue infections from adult patients were examined. S.aureus isolates were tested for MRSA and macrolide-lincosamide-streptogramin B (MLSB) phenotypes. Staphylococcal cassette chromosome mec (SCCmec) typing and S.aureus protein A (spa) typing were performed. Analysis of the genetic similarity was performed by pulsed-field gel electrophoresis. This study included 555 patients. An MRSA phenotype was detected in 15.1% of strains. The prevalence of MRSA infection was higher in patients aged >80 years. An MLSB phenotype was detected in 18.2% of strains. Analysis of SmaI profiles did not reveal a dominant clone. Spa typing showed 25 different spa types, and spa type t003 was the most common (49% of strains). Among MRSA strains, SCCmecII (49%) and SCCmecIV (27.4%) were predominant. The characteristics of MRSA showed considerable heterogeneity. The results demonstrate the need for caution when drawing conclusions on direct epidemiological relationships between isolates based on a single typing method. As the cases of infection in this study were not associated with the hospital environment and horizontal transfer, a focus on screening at hospital admission, and appropriate infection control, may help to reduce the risk of MRSA infections.

Meticillin-resistant Staphylococcus aureus colonisation and infection in Thoroughbred racehorses and veterinarians in Japan

Meticillin-resistant Staphylococcus aureus (MRSA) infections have been confirmed in hospitalised Thoroughbred racehorses at the hospitals of two training centres in Japan since 2009. To investigate the source of infection, the...

Whole-genome sequencing as standard practice for the analysis of clonality in outbreaks of meticillin-resistant Staphylococcus aureus in a paediatric setting

Meticillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-associated infections. This study investigated the potential use of whole-genome sequencing (WGS) for surveillance purposes by re-examining MRSA strains related to past outbreaks among hospitalized paediatric patients. WGS data ameliorated the genotypic profile previously obtained with Sanger sequencing and pulsed-field gel electrophoresis typing, and discriminated between strains that were related and unrelated to the outbreaks. This allowed strain clonality to be defined with a higher level of resolution than achieved previously. This study demonstrates the potential of WGS to trace hospital outbreaks, which may lead to WGS becoming standard practice in outbreak investigations.

Differing epidemiology of two major healthcare-associated meticillin-resistant Staphylococcus aureus clones

Two meticillin-resistant Staphylococcus aureus (MRSA) clones, sequence type (ST) 22 and ST239, have successfully spread globally. Across Australia, ST22 has supplanted ST239 as the main healthcare-associated MRSA. To understand the reasons underlying this shift, the epidemiology and clinical features of infections due to ST22 and ST239 MRSA isolates from a tertiary hospital in Melbourne, Australia were compared. Over six months, consecutive MRSA isolates with clinical data were collected from specimens referred to Alfred Health Pathology (AHP). Isolates were genotyped by a multi-locus-sequence-typing-based high-resolution melting method. Three hundred and twenty-eight of 1079 (30%) S.aureus isolated by AHP were MRSA. Of these, 313 were genotyped; 78 (25%) were clonal complex (CC) 22 (representing ST22) and 142 (45%) were CC239 (representing ST239). Common clinical syndromes included skin or soft tissue, respiratory tract and osteo-articular infections. On multi-variate logistic regression, compared with CC239, CC22 was associated with older patients [adjusted odds ratio (aOR) 1.04 for each year increase, 95% confidence interval (CI) 1.02-1.07)], and patients from subacute hospitals (aOR 2.7, 95% CI 1.2-5.8) or long-term care facilities (LTCFs; aOR 5.5, 95% CI 2.0-14.5). Median time from patient admission to MRSA isolation was nine days for CC239 and one day for CC22 (P<0.01). MRSA strain epidemiology varied according to hospital unit. CC22 and CC239 MRSA have differing ecological niches. CC22 is associated with elderly patients in LTCFs, and CC239 is associated with nosocomial acquisition. Infection control strategies involving LTCFs and their residents will likely be required to achieve continued MRSA control.

Evaluation of commercial chromogenic media for the detection of meticillin-resistant Staphylococcus aureus

Selective chromogenic media allowing one-step meticillin-resistant Staphylococcus aureus (MRSA) isolation and identification are widely used. However, the changing epidemiology of MRSA means that the suitability of these chromogenic media requires investigation. To evaluate the following chromogenic media - Colorex MRSA, MRSA Select II, ChromID MRSA, and MRSA Brilliance 2 - for the detection of divergent strain types. We used a diverse collection of S. aureus, including strains harbouring the mecC gene, strains expressing varying levels of meticillin resistance, and isolates recovered from patient samples. MRSA Select II, Colorex MRSA, and ChromID each grew at a density of 1.5 × 10(1)cfu/mL for each SCCmec type investigated. Brilliance 2 demonstrated growth at 1.5 × 10(1)cfu/mL for mecC MRSA but at a higher density (1.5 × 10(4)cfu/mL) for the three mecA MRSA strains. All four media demonstrated excellent sensitivity for MRSA detection (≥99%), but reduced levels of specificity (85-73%) when challenged with a range of meticillin-susceptible S. aureus (MSSA) isolates. High levels of false positives (∼50%) were also obtained with all chromogenic media when tested with mec-negative borderline oxacillin-resistant S. aureus (BORSA) isolates. Although false positives may be obtained with some strains of MSSA and BORSA, the high sensitivity of these media and their ability to recover almost all MRSA tested (including oxacillin-susceptible and mecC-positive strains) confirm the value of chromogenic agar in MRSA detection.

An FDA-Drug Library Screen for Compounds with Bioactivities against Meticillin-Resistant Staphylococcus aureus (MRSA).

The lack of new antibacterial drugs entering the market and their misuse have resulted in the emergence of drug-resistant bacteria, posing a major health crisis worldwide. In particular, meticillin-resistant Staphylococcus aureus (MRSA), a pathogen responsible for numerous human infections, has become endemic in hospitals worldwide. Drug repurposing, the finding of new therapeutic indications for approved drugs, is deemed a plausible solution to accelerate drug discovery and development in this area. Towards this end, we screened 1163 drugs approved by the Food and Drug Administration (FDA) for bioactivities against MRSA in a 10 μM single-point assay. After excluding known antibiotics and antiseptics, six compounds were identified and their MICs were determined against a panel of clinical MRSA strains. A toxicity assay using human keratinocytes was also conducted to gauge their potential for repurposing as topical agents for treating MRSA skin infections.