What is community-associated methicillin-resistant Staphylococcus aureus?

BACKGROUND: A community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has been defined as an MRSA infection in a patient who lacks specific risk factors for healthcare exposure. We sought to determine whether the absence or presence of these risk factors still predicts the phenotypic or genotypic characteristics of MRSA strains. METHODS: All clinical MRSA isolates were prospectively collected at the University of Chicago Hospitals from July 2004 through June 2005. Patients were interviewed and/or their medical records were reviewed. Isolates underwent genotyping and susceptibility testing. Data on patients and isolates were stratified in accordance with 8 frequently cited criteria for the identification of CA-MRSA and compared for concordance. RESULTS: Among 616 unique patients from whom MRSA isolates were recovered, 404 (65.6%) had risk factors for healthcare exposure. Of the 404 isolates recovered from these patients, 166 (41.1%) were clindamycin susceptible, 190 (47.0%) carried staphylococcal cassette chromosome mec (SCCmec) type IV, 145 (35.9%) carried the Panton-Valentine leukocidin genes (PVL+), and 162 (40.1%) were identified as sequence type (ST) 8 by multilocus sequence typing (MLST), all of which are characteristics commonly attributed to CA-MRSA strains. CONCLUSIONS: Association with the healthcare environment now has little predictive value for distinguishing patients with infection due to multidrug resistant MRSA isolates from those infected by CA-MRSA isolates, that is, isolates that are clindamycin-susceptible, PVL+, ST8, and/or contain SCCmec type IV. Defining CA-MRSA by the absence of risk factors for healthcare exposure greatly underestimates the burden of epidemic CA-MRSA disease.     

Community‐acquired,methicillin‐resistant Staphylococcus aureus isolated from children with community‐onset pneumonia in China

Community‐acquired, methicillin‐resistant Staphylococcus aureus (CA‐MRSA) has been associated with morbidity and mortality in various countries. In this study, we characterized the molecular and clinical features of pediatric CA‐MRSA pneumonia in China. Between June 2006 and February 2008, 55 previously healthy children confined in eight hospitals countrywide were found to be afflicted with CA‐MRSA pneumonia. A total of 55 strains collected from these children were analyzed by multilocus sequence typing (MLST), Staphylococcus cassette chromosome mec (SCCmec) typing, and spa typing. The Panton–Valentine leukocidin (PVL) gene was also detected. Overall, nine STs were obtained, with ST59 (40.4%) established to be the most prevalent type. We first registered the new ST1409 from a child with necrotizing pneumonia. SCCmecIVa was the most predominant type, followed by SCCmec type V. Twelve spa types were identified, of which one new spa type, t5348, was first detected and registered. One typical livestock‐associated spa type, t034, was found in a 4‐month‐old girl living in the countryside. We also found that 40% of those isolates were PVL‐positive. In addition, the median age of the children in this study was 10 months. A total of 69% (38/55) of the children with community‐acquired pneumonia (CAP) had preceding influenza or influenza‐like illness, and three ST910‐MRSA‐IV strains (PVL gene‐positive) were associated with severe necrosis. The results indicated that the recent CA‐MRSA found in Chinese children with CAP was largely associated with the spread of the ST59‐MRSA‐IV clone, and most of the PVL‐positive strains in this study did not cause necrotic cases. Pediatr Pulmonol. 2010; 45:387–394. © 2010 Wiley‐Liss, Inc.     

产杀白细胞素金黄色葡萄球菌感染的研究现状

国外多数回顾性研究发现产杀白细胞素(PVL)金黄色葡萄球菌感染有着特有的临床表现,特别是产PVL金黄色葡萄球菌相关性坏死性肺炎可能为一新现的临床疾病,由此PVL在金黄色葡萄球菌感染中的致病研究日益受到重视.本文就目前对产PVL金黄色葡萄球菌感染的致病机制、流行病学、检测和防治等问题研究作一综述.     

Community-associated methicillin-resistant Staphylococcus aureus necrotizing pneumonia without evidence of antecedent viral upper respiratory infection

BACKGROUND:

USA300 community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains causing necrotizing pneumonia have been reported in association with antecedent viral upper respiratory tract infections (URI).

METHODS:

A case series of necrotizing pneumonia presenting as a primary or coprimary infection, secondary to CA-MRSA without evidence of antecedent viral URI, is presented. Cases were identified through the infectious diseases consultation service records. Clinical and radiographic data were collected by chart review and electronic records. MRSA strains were isolated from sputum, bronchoalveolar lavage, pleural fluid or blood cultures and confirmed using standard laboratory procedures. MRSA strains were characterized by susceptibility testing, pulsed-field gel electrophoresis, spa typing, agr typing and multilocus sequence typing. Testing for respiratory viruses was performed by appropriate serological testing of banked sera, or nucleic acid testing of nasopharyngeal or bronchoalveloar lavage specimens.

RESULTS:

Ten patients who presented or copresented with CA necrotizing pneumonia secondary to CA-MRSA from April 2004 to October 2011 were identified. The median length of stay was 22.5 days. Mortality was 20.0%. Classical risk factors for CA-MRSA were identified in seven of 10 (70.0%) cases. Chest tube placement occurred in seven of 10 patients with empyema. None of the patients had historical evidence of antecedent URI. In eight of 10 patients, serological or nucleic acid testing testing revealed no evidence of acute viral coinfection. Eight strains were CMRSA-10 (USA300). The remaining two strains were a USA300 genetically related strain and a USA1100 strain.

CONCLUSION:

Pneumonia secondary to CA-MRSA can occur in the absence of an antecedent URI. Infections due to CA-MRSA are associated with significant morbidity and mortality. Clinicians need to have an awareness of this clinical entity, particularly in patients who are in risk groups that predispose to exposure to this bacterium.     

耐甲氧西林金黄色葡萄球菌杀白细胞素基因检测

目的 调查临床分离的耐甲氧西林金黄色葡萄球菌(MRSA)杀白细胞毒素基因携带率。方法 收集非重复MRSA菌株83株,按照美国疾病预防控制中心的CA-MRSA 定义分为HA-MRSA和CA-MRSA两组。采用多重PCR法进行SCCmec分型,普通PCR+测序法进行spa分型,普通PCR检测杀白细胞素(PVL)基因。结果 83株MRSA中HA-MRSA、CA-MRSA分别占47.0%、53.0%,SCCmec分型中SCCmecⅠ、Ⅱ、Ⅲ、Ⅳa型和未分型各占1.2%、3.6%、65.1%、28.9%、1.2%,spa分型中83株MRSA共检出15个型,主要分型为t437,t062,t015分别占39.8%, 21.7%,10.8%;PVL阳性的MRSA中HA-MRSA和CA-MRSA分别10.3%、36.4%,两者差异有显著性(P=0.006);33株spa t437中有18株携带PVL基因,阳性率54.5%,50株其他spa分型中仅2株携带PVL基因,阳性率4.0%,两者差异有显著性(P=0.000)。PVL基因阳性的MRSA特征CA-MRSA-Ⅳa-t437 9株,HA-MRSA-Ⅲ-t437 4株,HA-MRSA-Ⅳa-t437 3株;20株PVL基因阳性的MRSA中10株分离自皮肤软组织感染病例,6株分离于耳鼻喉科感染病例,3株分离于呼吸道感染病例,1株分离于败血症病例。结论 CA-MRSA菌株较HA-MRSA菌株的 PVL基因阳性率更高,同时也发现携带有更高毒力的CA-MRSA的克隆已经播散到医院的环境中,引起医院获得性相关感染。     

Coexistence of Panton-Valentine leukocidin-positive and -negative community-associated methicillin-resistant Staphylococcus aureus USA400 sibling strains in a large Canadian health-care region

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains often carry the Panton-Valentine leukocidin (PVL) genes. However, the specific role that PVL plays in the epidemiological features and pathogenesis of CA-MRSA infections has remained undefined and controversial. Conducting a retrospective study on a natural population of MRSA clinical isolates recovered from community and hospital patients in a large Canadian health-care region during a 6-year period, we identified the coexistence of 2 USA400 (a major clonal group of CA-MRSA) sibling strains with and without PVL genes. Polymerase chain reaction and sequence analysis indicated that the PVL-carrying prophage phiSa2mw was present in PVL(+) but absent in PVL(-) USA400 isolates. These strains shared identical genotypic and phenotypic properties and similar clinical characteristics. This study provides direct evidence that PVL genes are not necessarily the key determinants associated with the increasing dissemination of CA-MRSA strains, suggesting that the genomic milieu may play a greater role in this regard.     

Five cases of bacterial endocarditis after furunculosis and the ongoing saga of community-acquired methicillin-resistant Staphylococcus aureus infections

Bacterial endocarditis secondary to Panton-Valentine leukocidin producing community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections is rare. We report 5 previously healthy patients who presented with endocarditis after developing furunculosis due to CA-MRSA. A retrospective chart review of all patients with MRSA positive blood cultures was conducted over a 12-month period. Patients with multiple positive blood cultures within 72 h of admission and who had no risk factors for MRSA acquisition were included. Modified Duke's criteria were used to define bacterial endocarditis. PCR detection of Panton-Valentine leukocidin (PVL) genes as well as SCCmec typing was performed. In addition, strain typing of MRSA isolates was performed utilizing pulsed-field gel electrophoresis. Five out of a total of 193 patients had features consistent with CA-MRSA infections and met modified Duke's criteria for bacterial endocarditis. Blood culture isolates were found to be PVL gene positive and carried the type IV SCCmec element. PFGE confirmed that skin isolate was identical to the isolate cultured from his blood. Bacterial endocarditis in patients with CA-MRSA furunculosis is an emerging entity. In areas where CA-MRSA skin infections are prevalent, inappropriate initial antibiotics remain a major problem and may result in significant morbidity.     

Is Panton-Valentine leukocidin the major virulence determinant in community-associated methicillin-resistant Staphylococcus aureus disease?

Methicillin-resistant Staphylococcus aureus (MRSA) remains a major problem in hospitals, and it is now spreading in the community. A single toxin, Panton-Valentine leukocidin (PVL), has been linked by epidemiological studies to community-associated MRSA (CA-MRSA) disease. However, the role that PVL plays in the pathogenesis of CA-MRSA has not been tested directly. To that end, we used mouse infection models to compare the virulence of PVL-positive with that of PVL-negative CA-MRSA representing the leading disease-causing strains. Unexpectedly, strains lacking PVL were as virulent in mouse sepsis and abscess models as those containing the leukotoxin. Isogenic PVL-negative (lukS/F-PV knockout) strains of USA300 and USA400 were as lethal as wild-type strains in a sepsis model, and they caused comparable skin disease. Moreover, lysis of human neutrophils and pathogen survival after phagocytosis were similar between wild-type and mutant strains. Although the toxin may be a highly linked epidemiological marker for CA-MRSA strains, we conclude that PVL is not the major virulence determinant of CA-MRSA.     

The emergence of infections with community-associated methicillin resistant Staphylococcus aureus

Recently there have been reports indicating an increased incidence of MRSA infections, afflicting individuals with no apparent risk factors for hospital acquisition. Patients with community-associated (CA) MRSA are significantly younger and had different distributions of clinical infections compared with HA-MRSA patients. CA-MRSA infections have mostly been associated with staphylococcal strains bearing the SCCmec type IV element and PVL genes. These strains are more frequently susceptible to a variety of non-beta-lactam antibiotics. Clinicians must be aware of the wide and, in some cases, unique spectrum of disease caused by CA-MRSA. Continued emergence of MRSA in the community is a public-health problem that warrants increased vigilance in the diagnosis and management of suspected and confirmed staphylococcal infections.     

Methicillin-resistant Staphylococcus aureus as a cause of invasive infections in Central Africa: a case report and review of the literature

Introduction

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) colonization and infection are increasingly being reported worldwide and are associated with severe illness. The vast majority of MRSA infections are skin and soft tissue infections, while invasive disease remains rare. In Western countries, the epidemiology of MRSA is well documented, but from Central Africa, reports on MRSA are very limited.

Methods

Case presentation and review of the literature. The clinical features, epidemiology, and characteristics of MRSA in Central Africa, as well as the treatment options, are discussed. We present a case of severe invasive CA-MRSA infection with pneumonia, pericarditis, and bacteremia in a previously healthy young woman in Gabon. Several virulence factors, like Panton–Valentine leukocidin and type I arginine catabolic mobile element, may play a role in the ability of CA-MRSA to cause severe invasive infections. Based on studies from Gabon and Cameroon (no reports were available from other countries), we find that the prevalence of MRSA is relatively low in this region. Treatment depends primarily on local prevalence and resistance profile of MRSA combined with clinical characteristics.

Conclusion

Severe invasive infection with CA-MRSA is a rare disease presentation in Central Africa, where this pathogen is still relatively uncommon. However, cases of MRSA may be complicated by the human immunodeficiency virus (HIV) and tuberculosis epidemics, and also the limited availability of effective antibiotics.     

Panton-Valentine Leukocidin-positive methicillin-resistant Staphylococcus aureus lung infection in patients with cystic fibrosis

BACKGROUND: Panton-Valentine Leukocidin-expressing (PVL+) methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen worldwide causing fatal necrotizing pneumonias in otherwise healthy individuals but has not been described in patients with cystic fibrosis (CF). Following two cases of patients with CF admitted with lung abscesses in association with PVL+ MRSA, we examined the incidence and the clinical characteristics of MRSA acquisition in our CF patient population. METHODS: Newly acquired MRSA isolates from patients with CF followed up at St. Louis Children's Hospital were analyzed for the presence of Panton-Valentine leukocidin coding region, clindamycin susceptibility, staphylococcal cassette chromosome (SCC) mec type, and multilocus sequence type. Medical records and pulmonary function studies at the time of MRSA isolation were reviewed. RESULTS: MRSA isolates from 40 CF patients were available for analysis. Six children (15%) had PVL+ MRSA infection. All PVL+ organisms were clindamycin susceptible. Patients who acquired a PVL+ organism were more likely to have a focal pulmonary infiltrate on chest radiograph, including cavitary lung lesions in two patients (p = 0.04), a markedly greater decline in FEV1 at the time of MRSA detection (p = 0.01), and a significantly higher WBC count (p = 0.04) and absolute neutrophil count (p = 0.04). These patients were more likely to be admitted for IV antibiotic therapy for respiratory illnesses (p < 0.01). CONCLUSIONS: We describe the emergence of PVL+ MRSA in our CF population in association with development of invasive lung infections including lung abscesses. Early identification and treatment of CF patients with newly acquired PVL+ MRSA may be crucial.     

Complex molecular epidemiology of methicillin-resistant staphylococcus aureus isolates from children with cystic fibrosis in the era of epidemic community-associated methicillin-resistant S aureus

BACKGROUND: Limited data exist about the molecular types of methicillin-resistant Staphylococcus aureus (MRSA) strains found in children with cystic fibrosis (CF). We sought to characterize MRSA strains from these patients and compare them with MRSA strains from non-CF pediatric patients. METHODS: All MRSA isolates were collected prospectively at Children's Medical Center in Dallas, TX, and the University of Chicago Comer Children's Hospital in 2004 to 2005. All CF MRSA isolates underwent susceptibility testing, multilocus sequence typing, Panton-Valentine leukocidin gene detection (pvl+), and staphylococcal chromosome cassette mec (SCCmec) typing. RESULTS: A total of 22 of 34 MRSA isolates (64.7%) from patients with CF belonged to clonal complex (CC) 5 and contained SCCmec II, so-called health-care associated MRSA (HA-MRSA) strains. Nine of 34 MRSA strains (26.5%) were CC 8, and contained SCCmec IV, so-called community-associated MRSA (CA-MRSA) strains. The CA-MRSA strains tended to be isolated from newly colonized CF patients. In contrast, CC8 isolates predominated among the non-CF patients (294 of 331 patients; 88.8%). MRSA isolates from children with CF were more likely to be resistant to clindamycin (65% vs 19%, respectively) and ciprofloxacin (62% vs 17%, respectively) compared with strains from non-CF patients (p < 0.001). There was no difference in the rate of pvl+ isolate recovery from children with CF undergoing a surveillance culture (7 of 23 children) compared with those with pulmonary exacerbation (3 of 11 children; p = 1.0). CONCLUSIONS: Both CA-MRSA (CC8) isolates and HA-MRSA (CC5) isolates populate the respiratory tracts of children with CF. HA-MRSA isolates predominated, but CA-MRSA strains predominated among CF patients with newly acquired MRSA strains and among the non-CF patients. The presence of CA-MRSA strains in children with CF was not associated with exacerbation or necrotizing pneumonia.     

Methicillin-Resistant Staphylococcus aureus Ocular Infection in Taiwan: Clinical Features,Genotying, and Antibiotic Susceptibility

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an important public health issue. This observational study aimed to characterize clinical features, antibiotic susceptibility, and genotypes of ocular infections caused by MRSA based on the clinical and molecular definitions of community-associated (CA) and healthcare-associated (HA) strains.Fifty-nine patients with culture-proven S aureus ocular infection were enrolled from January 1, 2010 to December 31, 2011 at Chang Gung Memorial Hospital, Taiwan. Antibiotic susceptibility was verified using disk diffusion/E test. For characterization, staphylococcal cassette chromosome mec (SCCmec), pulsed-field gel electrophoresis (PFGE), multilocus sequence type (MLST), and Panton–Valentine leukocidin (PVL) gene, were performed. MRSA isolates from the patients with HA factors were classified as clinically defined HA-MRSA, and those carrying SCCmec type I to III as molecularly defined HA-MRSA.Thirty-four patients with MRSA ocular infection were identified. The most common clone of CA-MRSA and HA-MRSA isolates was ST59/PFGE type D/SCCmec IV,V_T/PVL (+) (n = 12) and CC 239/PFGE type A/SCCmec III, III_A/PVL(−) (n = 10), respectively. All the 11 patients with molecularly defined HA-MRSA infections and 50% of the 22 patients with molecularly defined CA-MRSA infections were found to have HA factors (P = .005). CA-MRSA tended to cause lid infections, whereas HA-MRSA tended to cause corneal infections. Contrary to HA-MRSA isolates, nearly all the CA-MRSA isolates were susceptible to trimethoprim/sulfamethoxazole and fluoroquinolones under either clinical or molecular classifications.In Taiwan, CA-MRSA isolates exhibited considerably higher susceptibility to fluoroquinolones when compared with HA-MRSA isolates. A strong correlation was observed between the HA factors and molecularly defined HA-MRSA isolates.     

Is Methicillin-Resistant Staphylococcus aureus Pneumonia Epidemiology and Sensitivity Changing?

IntroductionMethicillin-resistant Staphylococcus aureus (MRSA) pneumonia poses a deadly threat due to the pathogen’s remarkable resistance and virulence factors. Evidence suggests that the epidemiology and sensitivity to antibiotics for MRSA pneumonia is changing extremely fast, creating the potential for it to become a “super bug.”ObjectiveTo assess the incidence of community-acquired and hospital-acquired MRSA pneumonia in the community hospital at Christus Spohn during a period of 3 years and its reactivity to antibiotic therapy.MethodsThe retrospective study was performed using data collected from Christus Spohn Memorial Hospital Corpus Christi inpatient charts between 2006 and 2008. Patients were identified and selected based on positive sputum cultures for MRSA and using Center of Disease Control, American Thoracic Society and Infectious Diseases Society of America guidelines. Patients were then categorized into 2 groups: community-acquired MRSA (CA-MRSA) pneumonia and hospital acquired MRSA (HA-MRSA) pneumonia.ResultsOur results indicated increase resistance to clindamycin among both CA-MRSA and HA-MRSA, whereas the sensitivity to trimethoprim/sulfamethoxazole (TMP/SMX) is preserved for both CA-MRSA and HA-MRSA.ConclusionsResistance to clindamycin has increased over time, but TMP/SMX has preserved its sensitivity against MRSA. TMP/SMX should be revisited as a viable antibiotic option against CA-MRSA and HA-MRSA, specifically against CA-MRSA.     

Panton Valentine Leukocidin exotoxin has no effect on the outcome of cancer patients with methicillin-resistant Staphylococcus aureus (MRSA) infections

The presence of Panton-Valentine leukocidin (PVL) gene in methicillin-resistant Staphylococcus aureus (MRSA) infections has been associated with high severity and mortality rates. In this study we evaluated the effect of PVL on outcome in cancer patients with MRSA infections.We retrospectively reviewed the records of 173 cancer patients diagnosed with MRSA pneumonia (n = 47), skin and soft tissue infections (n = 77), and bacteremia (n = 49) between September 2003 and September 2007 at M. D. Anderson Cancer Center. We obtained demographic and clinical data and tested isolates for the presence of PVL. The data were compared between patients with PVL (+) and those with PVL (-) strains. Statistical methods for comparison included Cochran-Mantel-Haenszel tests, 2-way nonparametric analysis of variance, chi-square or Fisher exact tests, and Wilcoxon rank sum tests. All tests were 2-sided with a significance level of 0.05.Seventy patients with PVL (+) strains and 103 patients with PVL (-) strains were included in our study. Fewer PVL (+) patients had pneumonia than did PVL (-) patients (14% vs. 36%, p = 0.002). PVL (-) patients were more likely to have concomitant infections (35% vs. 17%, p = 0.012). The 2 groups were similar in terms of fever, sepsis, vasopressor use, mechanical ventilation, antibiotics response, infection relapse, death, and death due to MRSA. In a skin and soft tissue subset analysis, PVL (+) patients were more likely to have solid tumors (73% vs. 47%, p = 0.02) and less likely to have fever (20% vs. 44%, p = 0.02) and sepsis (12% vs. 36%, p = 0.013). There were no differences in outcome between patients with pneumonia and bacteremia; however, most patients with pneumonia were PVL (-) (79% vs. 21%). Among the 73 patients who received vancomycin and the 20 who received linezolid, there was no difference in response to treatment, regardless of PVL status or neutropenia. In conclusion, the presence of the PVL gene had no negative effect on cancer patients with health care-associated MRSA.     

Comparison of both clinical features and mortality risk associated with bacteremia due to community-acquired methicillin-resistant Staphylococcus aureus and methicillin-susceptible S. aureus.

BACKGROUND: The majority of research about community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has focused on skin and soft-tissue infections. No literature has been published on the clinical features and outcomes of adult patients with CA-MRSA bacteremia in comparison with patients with community-acquired methicillin-susceptible S. aureus (CA-MSSA) bacteremia. METHODS: From 1 January 2001 through 31 December 2006, the demographic data and outcome of 215 consecutive adult patients admitted to a tertiary care center in Taiwan with S. aureus bacteremia (age, >16 years) who fulfilled the criteria for community-acquired S. aureus bacteremia were collected for analysis. RESULTS: The mean age (+/-SD) was 56.8+/-20.5 years. There were 30 patients (14%) with CA-MRSA bacteremia and 185 (86%) patients with CA-MSSA bacteremia. Cutaneous abscess (odds ratio, 5.46; 95% confidence interval, 1.66-17.94) and necrotizing pneumonia (odds ratio, 24.81; 95% confidence interval, 2.63-234.03) were the independent predictors of CA-MRSA bacteremia; endovascular infection was the only independent predictor of CA-MSSA bacteremia. After Cox regression analysis, the independent significant risk factors for 30-day mortality included increased age, shock, and thrombocytopenia (<100,000 cells/microL). After adjustment, the day 30 mortality of patients with CA-MRSA bacteremia was not significantly higher than that of patients with CA-MSSA bacteremia (adjusted hazard ratio, 1.01; 95% confidence interval, 0.30-3.39; P = .986). Most (92%) of 25 available CA-MRSA isolates were multilocus sequence typing 59. CONCLUSIONS: The number of adult patients with CA-MRSA bacteremia increased with time, and the disease was associated with more necrotizing pneumonia and cutaneous abscess but less endovascular infection than was CA-MSSA bacteremia. Patients with CA-MRSA bacteremia did not have higher mortality than did patients with CA-MSSA, even though most of the patients with CA-MRSA bacteremia did not receive empirical glycopeptide therapy.     

Infective Endocarditis from Furuncle with Meningitis Complication Caused by Methicillin-resistant Staphylococcus aureus

Infective endocarditis (IE) may be acquired in the community as community-acquired (CA) IE or in the healthcare setting. In Japan, cases of CA-methicillin-resistant Staphylococcus aureus (MRSA) infection as skin infection have been increasing. CA-MRSA strains, including the USA300 clone, have higher pathogenicity and are more destructive to tissue than healthcare-associated MRSA strains because of the toxins they produce, including arginine-catabolic mobile element (ACME) and Panton-Valentine leukocidin (PVL). However, only a few IE cases induced by USA300 have been reported. We herein report a 64-year-old man who developed CA-IE from a furuncle caused by USA300 MRSA producing PVL and ACME, which resulted in complications of meningitis.     

Recognition and treatment of neonatal community-associated MRSA pneumonia and bacteremia

Community-associated strains of methicillin-resistant Staphylococcus aureus (CA-MRSA) have recently emerged as a major cause of serious infections among older children and are now being seen in NICU patients. We present the case of a preterm infant with CA-MRSA necrotizing pneumonia and secondary bacteremia.     

Fatal community-associated methicillin-resistant Staphylococcus aureus pneumonia in an immunocompetent young adult

Severe pneumonia caused by community-associated methicillin-resistant Staphylococcus aureus (MRSA) was reported in children soon after this pathogen emerged in the United States in the 1990s. Genes for Panton Valentine leukocidin, which are present in the majority of community-associated MRSA, are thought to enhance the ability of S aureus to cause necrotizing pneumonia. Despite the rapid spread throughout the United States of community-associated MRSA and related skin and soft-tissue infections, reports of severe pneumonia in adults have been rare. We describe a case of a healthy young adult who initially was treated as an outpatient with levofloxacin for what appeared to be typical community-acquired pneumonia. He soon returned to the emergency department (ED) with rapidly fatal necrotizing pneumonia, associated with hemoptysis, leukopenia, and sepsis syndrome, that was caused by community-associated MRSA carrying genes for Panton Valentine leukocidin. This case highlights the typical features of this form of pneumonia and the need to consider MRSA when evaluating and treating severe pneumonia in the ED. It also raises the question of whether the incidence of this form of pneumonia might be increasing in communities with a high prevalence of community-associated MRSA and whether current pneumonia treatment guidelines should be modified.     

Epidemiological and microbiological analysis of community-associated methicillin-resistant Staphylococcus aureus strains isolated from a Japanese hospital

Reports of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have recently increased in Japan; however, these studies contain limited information on their epidemiology. We performed a single-center study in the Tokyo Medical University Hospital located in Shinjuku, a central area of Tokyo, Japan. From 2,099 MRSA isolates obtained during July 2007 to March 2009, we selected 44 MRSA isolates with a MIC of <2 μg/mL for imipenem. Among 44 isolates, 28 strains had type IV or type V SCCmec, and we classified them as CA-MRSA. We identified only 1 Panton-Valentine leukocidin (PVL)-positive MRSA strain, which belonged to SCCmec type V. The PVL-positive CA-MRSA strain was isolated from a patient with multiple subcutaneous abscesses. The patient had returned to Japan from India; thus, the strain may have been contracted from outside of Japan. Thirteen (46.4%) and 15 strains (53.6%) were isolated from outpatients and inpatients, respectively. The major sites of infection included the respiratory tract (8 strains, 28.6%), skin/soft tissue (4 strains, 14.3%), and nasal cavity (4 strains, 14.3%). It is important to note that the most common site of CA-MRSA infection in inpatients was the respiratory tract; respiratory infections with CA-MRSA frequently cause severe infectious diseases.