Post-influenza pneumonia caused by the USA300 community-associated methicillin-resistant Staphylococcus aureus in Korea

Panton-Valentine leukocidin (PVL)-positive USA300 clone has been the most successful community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clone spreading in North America. In contrast, PVL-negative ST72-CA-MRSA has been predominant in Korea, and there has been no report of infections by the USA300 strain except only one case report of perianal infection. Here, we describe the first case of pneumonia caused by the USA300 strain following pandemic influenza A (H1N1) in Korea. A 50-year-old man was admitted with fever and cough and chest radiograph showed pneumonic consolidation at the right lower lung zone. He received a ventilator support because of respiratory failure. PCR for pandemic influenza A (H1N1) in nasopharyngeal swab was positive, and culture of sputum and endotracheal aspirate grew MRSA. Typing of the isolate revealed that it was PVL-positive, ST 8-MRSA-SCCmec type IV. The analysis of the PFGE patterns showed that this isolate was the same pulsotype as the USA300 strain.     

Rapid multiplex PCR assay for identification of USA300 community-associated methicillin-resistant Staphylococcus aureus isolates

Recent reports have noted a discernible increase in the number of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in patients without traditional risk factors. In the United States, the most prominent CA-MRSA strain encodes Panton-Valentine leukocidin (PVL) cytotoxin genes, belongs to pulsed field gel electrophoresis type USA300 and multilocus sequence type 8, and carries staphylococcal cassette chromosome mec (SCCmec) type IV. At present, molecular characterization of MRSA strains, such as USA300, can be time-consuming and is often beyond the technical capability of many clinical laboratories, making routine identification difficult. We analyzed the chromosomal regions flanking the SCCmec element in 44 USA300 MRSA isolates and identified a signature "AT repeat" sequence within the conserved hypothetical gene SACOL0058 located 1.4 kb downstream of the 3' end of the J1-SCCmec chromosomal junction. Only USA300 isolates tested contained a sequence of > or =6 AT repeats in combination with PVL (e.g., related USA500 or Iberian strains had > or =6 AT repeats but were PVL negative). Using a locked nucleic acid primer specific for > or =6 AT repeats in combination with primers to detect PVL, we developed a multiplex PCR assay specific for the identification of USA300 strains. Multiplex results were 100% concordant with DNA sequencing, suggesting that the method has promise as a means of rapidly identifying USA300 isolates.     

USA300 genotype community-associated methicillin-resistant Staphylococcus aureus as a cause of surgical site infections

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains are increasingly recovered from nosocomial settings. We conducted a retrospective study of surgical site infections (SSI) during 2004 and 2005 to determine the prevalence of CA-MRSA; 57% of MRSA strains tested belonged to the USA300 genotype. CA-MRSA has become a prominent cause of SSI at our institution.     

USA300 abroad: global spread of a virulent strain of community-associated methicillin-resistant Staphylococcus aureus

The epidemic of USA300-0114 methicillin-resistant Staphylococcus aureus (MRSA) in the USA has been remarkable for its virulence and for its ability to cause infections in both the community and healthcare settings. Although it has mainly been associated with skin and soft tissue infections, particularly furunculosis, it has also caused severe life-threatening conditions such as necrotizing pneumonia, osteomyelitis, and septic arthritis. This strain or a closely related Latin American variant has now spread to multiple countries on five continents, where associated clinical and epidemiological features have been in keeping with those seen in the USA. Furthermore, it has become the dominant community-associated MRSA strain in five countries. It is now a major international epidemic strain, but whether it will supplant established community-associated strains in other countries remains to be seen.     

Community-associated methicillin-resistant Staphylococcus aureus epidemic clone USA300 in isolates from Florida and Washington

We examined 299 methicillin-resistant, community-associated Staphylococcus aureus isolates from Florida and Washington State for the presence of the USA300 epidemic clone. Pulsed-field gel electrophoresis demonstrated the epidemic clone in 43% of our S. aureus strains and in isolates from both states. The majority of the USA300 isolates (88%) were from wound infections.     

Phenotypic prediction rule for community-associated methicillin-resistant Staphylococcus aureus

Recent studies have suggested that community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are encroaching upon nosocomial settings. We assessed the performance characteristics of a rule using the antimicrobial phenotype to predict genotype. This rule could be applied for epidemiologic purposes to describe the trend in CA-MRSA infections over time.     

Long-term follow-up of methicillin-resistant Staphylococcus aureus molecular epidemiology after emergence of clone USA300 in San Francisco jail populations

We performed a longitudinal analysis of 502 unique methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates originating from San Francisco jail inmates between 2000 and 2007. Strain USA300, first encountered in 2001, accounted for 82.1% (412/502) of MRSA infections. Non-USA300 MRSA strains were rarely found after 2005 (one isolate in 2006, three in 2007).     

Genetic lineages of community-associated methicillin-resistant Staphylococcus aureus in Kuwait hospitals

Twenty-six community-associated methicillin-resistant Staphylococcus aureus (CAMSRA) isolates were characterized by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) and screened for accessory gene regulator (agr), capsular polysaccharide (cap), and Panton-Valentine leucocidin (PVL) genes. They exhibited five PFGE patterns (types A to E). The majority were PFGE type A (12 isolates) or type B (8 isolates). MLST showed that PFGE type A isolates belonged to sequence type 80 (ST80), while the PFGE type B isolates were ST30. The ST80 and ST30 clones contained agr allotype 3, cap type 8, and PVL. The results showed that two internationally recognized CAMRSA clones are dominant in Kuwait hospitals.     

Epidemiology and outcomes of community-associated methicillin-resistant Staphylococcus aureus infection

Over a 2-year period (2003 to 2005) patients with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and community-acquired methicillin-susceptible Staphylococcus aureus (CA-MSSA) infections were prospectively identified. Patients infected with CA-MRSA (n = 102 patients) and CA-MSSA (n = 102 patients) had median ages of 46 and 53 years, respectively; the most common sites of infection in the two groups were skin/soft tissue (80 and 93%, respectively), respiratory tract (13 and 6%, respectively), and blood (4 and 1%, respectively). Fourteen percent of patients with CA-MRSA infections and 3% of patients with CA-MSSA infections had household contacts with similar infections (P < 0.01). Among the CA-MRSA isolates, the pulsed-field gel electrophoresis (PFGE) groups detected were USA300 (49%) and USA100 (13%), with 27 PFGE groups overall; 71% of the isolates were staphylococcal chromosome cassette mec (SCCmec) type IV, 29% were SCCmec type II, and 54% had the Panton-Valentine leucocidin (PVL) gene. Among the CA-MSSA isolates there were 33 PFGE groups, with isolates of the USA200 group comprising 11%, isolates of the USA600 group comprising 11%, isolates of the USA100 group comprising 10%, and isolates of the PVL type comprising 10%. Forty-six and 18% of the patients infected with CA-MRSA and CA-MSSA, respectively, were hospitalized (P < 0.001). Fifty percent of the patients received antibiotic therapy alone, 5% received surgery alone, 30% received antibiotics and surgery, 3% received other therapy, and 12% received no treatment. The median durations of antibiotic therapy were 12 and 10 days in the CA-MRSA- and CA-MSSA-infected patients, respectively; 48 and 56% of the patients in the two groups received adequate antimicrobial therapy, respectively (P < 0.001). The clinical success rates of the initial therapy in the two groups were 61 and 84%, respectively (P < 0.001); recurrences were more common in the CA-MRSA group (recurrences were detected in 18 and 6% of the patients in the two groups, respectively [P < 0.001]). CA-MRSA was an independent predictor of clinical failure in multivariate analysis (odds ratio, 3.4; 95% confidence interval, 1.7 to 6.9). In the community setting, the molecular characteristics of the S. aureus strains were heterogeneous. CA-MRSA infections were associated with a more adverse impact on outcome than CA-MSSA infections.     

Methicillin-resistant Staphylococcus aureus USA300 clone as a cause of Lemierre's syndrome

We describe a case of a young woman who had methicillin-resistant Staphylococcus aureus USA300 clone (MRSA-USA300)-associated Lemierre's syndrome and secondary necrotizing pneumonia and cerebral infarcts. We also review 11 cases of S. aureus-associated Lemierre's syndrome reported in the literature from 1965 to 2010. Recognition of S. aureus as an emergent cause of Lemierre's syndrome informs the initial empirical antibiotic choice for this life-threatening condition and may positively impact patient outcomes.     

社区相关性耐甲氧西林金黄色葡萄球菌致病性研究进展

社区相关性耐甲氧西林金黄色葡萄球菌(CA-MRSA)自从上世纪八十年代出现以来,得到了全世界的普遍关注。CA-MRSA较强地适应外界环境的能力和定植能力对于其致病性起到了十分重要的作用,近期在CA-MRSA-USA300型菌株的基因组中发现的可移动精氨酸代谢元件(ACME),以及该段DNA编码的精氨酸脱亚胺酶(arginine deiminase)对MRSA在人体中的定植起到了重要作用。     

USA300 methicillin-resistant Staphylococcus aureus in Zurich,Switzerland between 2001 and 2013

USA300 methicillin-resistant Staphylococcus aureus (MRSA) is the most prevalent MRSA in the United States of America (USA) and a global epidemic threat. We investigated the prevalence of USA300 at a tertiary care hospital in Zurich, Switzerland, where all MRSA strains have been collected and PFGE typed since 1992. These strains were retrospectively compared to the PFGE pattern of USA300 strain JE2. Isolates with a respective PFGE pattern were spa-typed and tested for the presence of the arginine catabolic mobile element (ACME) arc gene cluster and Panton-Valentine Leucocidin (PVL) genes. The first MRSA strain with a USA300 PFGE pattern was isolated in 2001 from a patient visiting from the USA. USA300 strains represented between 0% (in 2002) and 9.2% (in 2012) of all MRSA isolates in our hospital. We identified various USA300 subtypes based on either the PFGE pattern, the spa-type or absence of either the PVL genes or ACME arc gene cluster. All the USA300 strains including the variants (n = 47) accounted for 5.6% of all MRSA isolates typed between 2001 and 2013 and reached a maximum of 14.5% in 2009. They predominantly caused skin and soft tissue infections (74.4%). In conclusion, even though USA300 has been present in our hospital for over twelve years it has not become the predominant MRSA clone like in the USA. However, in light of the global burden of USA300, care must be taken to further contain the spread of this lineage and of MRSA in general in our hospital.     

Invasive infections with community-associated methicillin-resistant Staphylococcus aureus after kidney transplantation

We report two cases of invasive infections caused by Panton-Valentine leukocidin-positive, community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA) after kidney transplantation. This report emphasizes the clinical importance of considering CA-MRSA as a causative agent in the differential diagnosis of infections of the skin and soft tissues in organ transplant recipients.     

The economic burden of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA)

The economic impact of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) remains unclear. We developed an economic simulation model to quantify the costs associated with CA-MRSA infection from the societal and third-party payer perspectives. A single CA-MRSA case costs third-party payers $2277–$3200 and society $7070–$20 489, depending on patient age. In the United States (US), CA-MRSA imposes an annual burden of $478 million to 2.2 billion on third-party payers and $1.4–13.8 billion on society, depending on the CA-MRSA definitions and incidences. The US jail system and Army may be experiencing annual total costs of $7–11 million ($6–10 million direct medical costs) and $15–36 million ($14–32 million direct costs), respectively. Hospitalization rates and mortality are important cost drivers. CA-MRSA confers a substantial economic burden on third-party payers and society, with CA-MRSA-attributable productivity losses being major contributors to the total societal economic burden. Although decreasing transmission and infection incidence would decrease costs, even if transmission were to continue at present levels, early identification and appropriate treatment of CA-MRSA infections before they progress could save considerable costs.     

Community-associated methicillin-resistant Staphylococcus aureus immune evasion and virulence

Staphylococcus aureus is a significant cause of human infections globally. Methicillin-resistant S. aureus (MRSA) emerged in the early 1960s and is now endemic in most healthcare facilities. Although healthcare-associated MRSA infections remain a major problem in most industrialized countries, those caused by community-associated MRSA (CA-MRSA) are now the most abundant cause of bacterial infections in the community in some parts of the world, such as the United States. The basis for the emergence and subsequent success of CA-MRSA is incompletely defined. However, the ability of the pathogen to cause disease in otherwise healthy individuals is likely attributed, in part, to its ability to circumvent killing by the innate immune system, which includes survival after phagocytosis by neutrophils. In this review, we discuss the role of neutrophils in host defense against S. aureus and highlight progress made toward understanding mechanisms of CA-MRSA virulence and pathogenesis.     

Novel multiplex PCR assay for simultaneous identification of community-associated methicillin-resistant Staphylococcus aureus strains USA300 and USA400 and detection of mecA and Panton-Valentine leukocidin genes, with discrimination of Staphylococcus aureus from coagulase-negative staphylococci

We developed a novel multiplex PCR assay for rapid identification and discrimination of the USA300 and USA400 strains and concomitant detection of Panton-Valentine leukocidin genes, with simultaneous discrimination of methicillin-resistant Staphylococcus aureus strains from methicillin-susceptible S. aureus strains, S. aureus strains from coagulase-negative staphylococci, and staphylococci from other bacteria.     

Caenorhabditis elegans as a host model for community-associated methicillin-resistant Staphylococcus aureus

The nematode Caenorhabditis elegans has recently been developed as a host model for the study of Staphylococcus aureus virulence and pathogenesis. Here, the toxicity and virulence of representative clinical isolates of our methicillin-resistant S. aureus (MRSA) epidemic strains were studied using this model. The strains USA300 (associated with community infection outbreaks), USA400 (associated with sporadic community infections) and CMRSA2 (associated with both hospital and community infections), as well as the nematocidal reference strain NCTC8325, showed high nematocidal activity, both by killing the majority of the nematodes (> 90%) over 9 days, and by inhibiting second-generation nematode growth. By contrast, the typical hospital-associated MRSA strain CMRSA6, the colonization strain M92, and the non-pathogenic Staphylococcus epidermidis control strain ATCC12228 were non-toxic to the nematode, which behaved normally. The absence of nematocidal activity does not reflect lack of growth or reduced growth of the bacterial inoculum. The two non-nematocidal strains share similar genomic backgrounds, bacterial growth curve patterns and virulence gene profiles. However, the nematocidal strains each showed the same low maximum density growth curve patterns, but possessed distinct genetic profiles; no common virulence gene patterns or specific genes have been elucidated. Our findings demonstrate that community-associated MRSA strains are more pathogenic than hospital-associated MRSA in the C. elegans model and support the use of this model for studying the virulence of S. aureus strains.