Detection of methicillin-resistant Staphylococcus aureus (MRSA) using polymerase chain reaction amplification

Polymerase chain reaction (PCR) was applied for the detection of methicillin-resistant Staphylococcus aureus (MRSA). This procedure amplified a segment of MRSA-PBP (penicillin-binding protein) gene of DNA extract from the clinical isolates of S. aureus. A 1339-base-pair fragment of MRSA-PBP gene in DNA from S. aureus (MIC of methicillin, greater than or equal to 16 micrograms/ml) was amplified and detected by a specific oligonucleotide probe. Moreover, a 4.3 kb HindIII fragment containing MRSA-PBP gene was detected by using the same oligonucleotide probe. On the other hand, no PCR-amplified product was detected in DNA from methicillin-sensitive S. aureus (MIC of methicillin, less than 16 micrograms/ml).     

Staphylococcus aureus (methicillin-resistant S. aureus: MRSA)

Before antibiotic development, Staphylococcus aureus was a cause of serious invasive infections such as sepsis and meningitis and claimed many lives. However, even after antibiotic development, S. aureus posed a new threat as a major nosocomial pathogen, changing it to methicillin-resistant S. aureus (MRSA) since 1961. This year marks the 50th anniversary of the first report on MRSA. Today, there are two classes of MRSA spreading in hospitals and the community. The United States experienced invasive MRSA epidemics in 2005, and the latter MRSA (named CA-MRSA), especially USA300, affected the entire United States. As a countermeasure, guidelines for the management of MRSA infections were prepared in 2011. In Japan, there are people who are suffering from "hidden" epidemics in the community, falling behind in fighting CA-MRSA. We summarized current epidemic MRSA and infections.     

Update on methicillin-resistant Staphylococcus aureus (MRSA)

MRSA was once acquired almost exclusively in hospitals and long-term care facilities, but it is now spreading in the community. Controlling the spread of MRSA requires appropriate selection and administration of antibiotics, and strict asepsis and infection control efforts. Remember that the most important means of preventing the spread of MRSA is meticulous hand washing and the use of alcohol-based hand rubs.     

An attempt to control nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection]

A strain of Methicillin-Resistant Staphylococcus aureus (MRSA) was first isolated in our hospital in March 1986. Since then, MRSA has become a difficult pathogen and a cause of sepsis, bacterial endocarditis, and pneumonia in 1988. Rigorous hospital-wide control measures have been planned. The major control measures, based on the various investigations reported, consist of the following three points; improvement of environmental control, reinforcement of handwashing practices during care and control usage of antibiotics. The frequency of isolation of MRSA among the S. aureus isolates was 43.3% in 1988 and this was further reduced to 31.7% in 1990. The total number of MRSA isolates from decubitus, bile, and blood samples have also declined. This decline resulted in a reduction of cases of severe MRSA infection. As yet, MRSA strain are still isolated on incubation. There may be a limit to complete control by measures in a single hospital. It is desired that regional measures and national consensus on nosocomial infection be established.     

Spontaneous methicillin-resistant Staphylococcus aureus (MRSA) meningitis

Spontaneous methicillin-resistant Staphylococcus aureus (MRSA) meningitis is extremely rare and has a high mortality rate. We report a case of MRSA meningitis in an otherwise healthy young adult female with no recent trauma or neurosurgical interventions. Despite antibiotics she suffered a vasculitis-induced cerebral vascular ischemic event.     

Risk factors associated with nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection including previous use of antimicrobials

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen worldwide. To investigate an association between antimicrobial use and MRSA, a case control study of 121 patients infected with MRSA compared with 123 patients infected with methicillin-susceptible S. aureus (MSSA) was carried out. Antimicrobial use was analysed by three different logistic regression models: all beta-lactam antibiotics, beta-lactam antibiotics grouped in classes and antimicrobial use in grammes. Patients infected with MRSA tended to have more co-morbidities, longer lengths of stay (LOS) and greater exposure to antibiotics than MSSA-infected patients. Multivariate analysis identified levofloxacin [odds ratio (OR) 8.01], macrolides (OR 4.06), previous hospitalization (OR 1.95), enteral feedings (OR 2.55), surgery (OR 2.24) and LOS before culture (OR 1.03) as independently associated with MRSA infection. All models were concordant with the exception of macrolides, which were not significant based on the number of grammes administered. There were no significant differences in the types of infection or the attributed mortality in either group. MRSA-infected patients had a significantly longer LOS before infection [18.8 +/- 18.2 compared with 8.4 +/- 6.9 (P < 0.001)] and a significantly longer post-diagnosis LOS [27.8 +/- 32.9 compared with 18.6 +/- 21 (P = 0.01)] than MSSA-infected patients.     

Mandatory surveillance of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in England: the first 10 years

Since 2001 it has been mandatory for acute hospital Trusts (groups of hospitals under the same management) in England to report all cases of bacteraemia due to Staphylococcus aureus together with information on their susceptibility or resistance to methicillin. This allowed the incidence of methicillin-resistant S. aureus (MRSA) bacteraemia (expressed as the number of cases per 1000 occupied bed days) to be determined for each Trust. In late 2005, the scheme was enhanced to collect demographic, clinical and epidemiological information on each case using a web-based data collection system. Analysis of this mandatory dataset has provided important information on the trends in MRSA bacteraemia in England and has documented a year-on-year decrease in incidence since 2006, following a government initiative in which Trusts were tasked with halving their MRSA bacteraemia rates over a 3 year period. In addition, the enhanced mandatory surveillance scheme has captured a wealth of data that have helped to further define the epidemiology of MRSA bacteraemia. It is to be hoped that based on the English experience of mandatory surveillance, other countries will consider the implementation of similar schemes, not only for MRSA but for other pathogens of public health importance.     

Predictive Value of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Swab PCR Assay for MRSA Pneumonia

Pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with poor outcomes and frequently merits empirical antibiotic consideration despite its relatively low incidence. Nasal colonization with MRSA is associated with clinical MRSA infection and can be reliably detected using the nasal swab PCR assay. In this study, we evaluated the performance of the nasal swab MRSA PCR in predicting MRSA pneumonia. A retrospective cohort study was performed in a tertiary care center from January 2009 to July 2011. All patients with confirmed pneumonia who had both a nasal swab MRSA PCR test and a bacterial culture within predefined time intervals were included in the study. These data were used to calculate sensitivity, specificity, positive predictive value, and negative predictive value for clinically confirmed MRSA pneumonia. Four hundred thirty-five patients met inclusion criteria. The majority of cases were classified as either health care-associated (HCAP) (54.7%) or community-acquired (CAP) (34%) pneumonia. MRSA nasal PCR was positive in 62 (14.3%) cases. MRSA pneumonia was confirmed by culture in 25 (5.7%) cases. The MRSA PCR assay demonstrated 88.0% sensitivity and 90.1% specificity, with a positive predictive value of 35.4% and a negative predictive value of 99.2%. In patients with pneumonia, the MRSA PCR nasal swab has a poor positive predictive value but an excellent negative predictive value for MRSA pneumonia in populations with low MRSA pneumonia incidence. In cases of culture-negative pneumonia where initial empirical antibiotics include an MRSA-active agent, a negative MRSA PCR swab can be reasonably used to guide antibiotic de-escalation.     

Change in genotype of methicillin-resistant Staphylococcus aureus (MRSA) affects the antibiogram of hospital-acquired MRSA

Recently, the dissemination of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) into hospitals has frequently been reported worldwide. Hospital-acquired MRSA (HA-MRSA) strains exhibit high-level resistance to multiple antimicrobial agents, whereas CA-MRSA strains are usually susceptible to non-β-lactams. Thus, it is predicted that the antibiogram of the HA-MRSA population would change along with the change in genotype of MRSA. Here, we investigated the changes in the MRSA population along with the MRSA antibiogram in a hospital between 2010 and 2016. Staphylococcal cassette chromosome (SCC) mec typing showed that the predominant HA-MRSA strains in the hospital dramatically changed from SCCmec type II, which is the major type of HA-MRSA, to SCCmec type IV, which is the major type of CA-MRSA. Multilocus sequence typing revealed that the predominant SCCmec type IV strain was a clonal complex (CC) 8 clone, which is mainly found among CA-MRSA. Furthermore, the CC1-SCCmec type IV (CC1-IV) clone significantly increased. Both the CC8-IV and CC1-IV clones exhibited high antimicrobial susceptibility. The antibiogram change of the HA-MRSA population was consistent with the antimicrobial susceptibilities and increased prevalence of the CC8-IV and CC1-IV clones. Our data reveal that the change in the genotypes of MRSA strains could impact the antibiogram of HA-MRSA population.     

Mersacidin eradicates methicillin-resistant Staphylococcus aureus (MRSA) in a mouse rhinitis model

OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) often colonize the anterior nares, and nasal carriage remains the main source of bacterial dissemination. The aim of this study was to assess the in vivo activity of the lantibiotic mersacidin against MRSA colonizing nasal epithelia. METHODS: The efficiency of mersacidin in the eradication of MRSA was tested employing mice pre-treated with hydrocortisone and inoculated intranasally either three or six times with a bacterial suspension. RESULTS: In mersacidin-treated animals, pre-colonized with MRSA, bacteria could not be detected in blood, lungs, liver, kidney, spleen or nasal scrapings and there were no lesions manifested after intraperitoneal drug application. Blood samples from infected mice obtained 2 h after mersacidin therapy revealed anti-MRSA activity in a serum bactericidal test. Moreover, elevated interleukin-1beta and tumour necrosis factor-alpha titres were noticed in the pre-infected but not in cured animals. In contrast, mersacidin did not induce differences in the cytokine profiles of treated uninfected control mice. CONCLUSIONS: In the mouse rhinitis model, mersacidin was able to eradicate MRSA colonization. The site of action (epithelium versus blood) of mersacidin needs to be further explored.     

Guidelines for the laboratory diagnosis and susceptibility testing of methicillin-resistant Staphylococcus aureus (MRSA)

These evidence-based guidelines have been produced after a literature review of the laboratory diagnosis and susceptibility testing of methicillin-resistant Staphylococcus aureus (MRSA). We have considered the detection of MRSA in screening samples and the detection of reduced susceptibility to glycopeptides in S. aureus. Recommendations are given for the identification of S. aureus and for suitable methods of susceptibility testing and screening for MRSA and for S. aureus with reduced susceptibility to glycopeptides. These guidelines indicate what tests should be used but not when the tests are applicable, as aspects of this are dealt with in guidelines on control of MRSA. There are currently several developments in screening media and molecular methods. It is likely that some of our recommendations will require modification as the new methods become available.     

Lemierre's syndrome: methicillin-resistant Staphylococcus aureus (MRSA) finds a new home

Lemierre's syndrome is septic thrombophlebitis of the internal jugular vein, arising as a complication of an oropharyngeal infection. This thrombophlebitis frequently results in septic emboli to organs such as the lungs. The causative agent in most previously described cases is Fusobacterium necrophorum, an anaerobic Gram-negative organism. We present the case of an 8-year-old previously healthy girl who came to the Emergency Department with a 5-day history of left-sided neck pain and was subsequently diagnosed with methicillin-resistant Staphylococcus aureus (MRSA) Lemierre's syndrome. MRSA has not previously been described in Lemierre's syndrome in the Emergency Medicine literature. The clinical presentation, findings, and management of the syndrome are discussed. Regardless of etiology, once the diagnosis of Lemierre's syndrome is made, long-term broad-spectrum intravenous therapy will be necessary.     

耐甲氧西林金黄色葡萄球菌耐药基因及其相关因素分析

目的了解耐甲氧西林金黄色葡萄球菌（MRSA）耐药现状,加强临床MRSA的监控。方法回顾性分析临床46株MRSA耐药性,并用PCR法对MRSA进行β-内酰胺类耐药相关基因mecA、氨基糖甙类耐药相关基因aac（6′）／aph（2″）、红霉素类耐药基因emr和耐消毒剂基因qac（A／B）检测。结果46株MRSA表现多重耐药和高度耐药性,并检测出相关的耐药基因。结论在临床工作中加强MRSA的监测、合理使用抗生素、严格消毒隔离制度是控制MRSA医院感染的关键。     

耐甲氧西林金黄色葡萄球菌产色培养基临床应用评估

目的通过头孢西丁纸片法、耐甲氧西林金黄色葡萄球菌(MRSA)产色筛选平板法和聚合酶链反应(PCR)检测MRSA,评估MRSA产色筛选平板的敏感性和特异性。方法收集仁济医院2008年8月至9月临床分离的金黄色葡萄球菌68株,分别采用头孢西丁纸片法、MRSA产色筛选平板法和PCR检测MRSA,以PCR检测femA基因和mecA基因结果为金标准,比较MRSA产色筛选平板的敏感性和特异性。结果甲氧西林敏感金黄色葡萄球菌(MSSA)除万古霉素、替考拉宁和利奈唑胺外,对其他11种抗菌药物的敏感率明显高于MRSA。68株金黄色葡萄球菌中,头孢西丁纸片法筛选出50株MRSA,产色平板法筛选出51株MRSA,PCR检测到51株mecA基因阳性,MRSA产色筛选平板结果和mecA基因检测结果符合率为100%。结论MRSA产色筛选平板可用于临床快速检测MRSA。