Frequent carriage of Panton-Valentine leucocidin genes by Staphylococcus aureus isolates from surgically drained abscesses

Microbiology of Facial Skin Infections-Strains, Susceptibility, and Therapeutic Consequences

BACKGROUND

Skin and soft tissue infections (SSTIs) are common conditions with severe and potentially life-threatening outcomes. However, the use of antibiotics to treat these infections is controversial.

PURPOSE

This study was to identify the microorganisms responsible for facial SSTIs, their antibiotic sensitivities, and the therapeutic outcomes of treatment.

STUDY DESIGN, SETTING, AND SAMPLE

This was a retrospective, observational cohort study conducted at a single oral and maxillofacial plastic surgery department. The study sample included 103 patients with facial SSTIs (61 men, 42 women) with a mean age of 41.8 years (standard deviation ± 20.4).

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLES

The predictor variables included patient characteristics, antibiotic use before the clinic visit, and the infection's site and origin.

MAIN OUTCOME VARIABLE(S)

The primary outcome variable was the presence of antibiotic resistance in the bacterial strains isolated from the infections.

METHODS

The data were collected by reviewing the results of microbiological swabs and patient records obtained from patients with facial SSTIs. Categorical variables were described using absolute and relative frequencies, and continuous variables were described using mean and standard deviation. The association between antibiotic resistance and the predictor variables was analyzed using Pearson's χ² test and student's t test.

RESULTS

The most common cause of SSTI was an infected epidermal cyst (60.1%). Of all the microorganisms identified, 80.6% were Gram-positive, and 55.8% showed antibiotic resistance against one or more of the evaluated antibiotics, including several backup antibiotics. There were no identified risk factors that significantly influenced the probability of resistance, and there were no adverse events observed.

CONCLUSION

The results of this study suggest that surgery should be the primary approach for treating SSTIs, as antibiotic administration may not be effective due to the unknown susceptibility of the causative strains. Antibiotics should be reserved for severe cases and high-risk patients, and if deemed necessary for SSTI management, a broad-spectrum antibiotic should be administered to cover resistant organisms.

In Vivo Pathogenicity of Methicillin-Susceptible Staphylococcus aureus Strains Carrying Panton-Valentine Leukocidin Gene

Toxin-producing Staphylococcus aureus strains posing a potential risk for public health have long been a topic of scientific research. Effects of Panton-Valentine leukocidin (PVL) on tissue destruction mechanisms and activities of inflammatory cells were presented in animal models of pneumonia and skin infections induced by PVL-producing S. aureus strains. This study aimed to demonstrate the in vivo pathogenicity of PVL-producing S. aureus strains isolated from some foodstuffs, which can be a potential risk to public health. PVL-positive methicillin-susceptible S. aureus (MSSA) strains M1 and YF1B-b isolated from different foodstuffs and a PVL-positive MSSA strain HT480 (positive control) were administered to New Zealand rabbits. Blood samples were harvested three and six hours after the intratracheal inoculation. Lung tissue samples were collected for gross and microscopic exams and immunohistochemical (IHC) demonstration of IL-6, IL8, IL-10, and TNF-α expressions. Serum cytokine levels were also measured by ELISA. The strains isolated from lung tissue samples were confirmed by pulsed-field gel electrophoresis. The development of acute necrotising pneumonia and a significant elevation in IL-6, IL-8, IL-10, and TNF-α expressions demonstrated the significance of foodborne PVL-positive MSSA strains in public health for the first time.

Paediatric and adult patients from New Caledonia Island admitted to the ICU for community-acquired Panton-Valentine leucocidin-producing Staphylococcus aureus infections

Severe infections involving Panton-Valentine leukocidin-producing Staphylococcus aureus (PVL + Sa) are increasing. This monocentre, retrospective descriptive cohort assessed clinical characteristics and outcome of paediatric and adult patients admitted for community-acquired PVL + Sa infections to the unique intensive care unit (ICU) on New Caledonia Island. Overall, 72 patients (including 23 children) admitted for acute respiratory failure (42%), sepsis/septic shock (21%), and/or postoperative care (32%) were analysed. Most patients had pulmonary (64%), skin/soft tissue (SSTI) (54%) and/or osteoarticular (38%) infections. Multifocal infections (≥ 2 sites) and bacteraemia were reported in 65% and 76% of the patients, respectively. Methicillin-resistant S. aureus isolates were reported in 61% of adult cases versus 30% in children (p < 0.05). Mechanical ventilation, vasoactive support and source control were administered in 53%, 43% and 58% of the patients, respectively. All paediatric patients received adequate empirical antibiotic therapy versus 30/49 adults (p < 0.001). Adequate documented therapy was obtained ≤ 72 h in 70/72 (97%) patients. Death was only reported in adults (n = 10 (14%)), mainly during pulmonary infection (22%), SSTIs (21%) and bacteraemia (24%)). In summary, in ICU patients from New Caledonia Island the clinical presentation of severe community-acquired PVL + Sa infections seems different from Western European observations with high rates of multifocal infections and methicillin-resistant strains.

Molecular Characterization and Pathogenicity of Staphylococcus aureus Isolated from Benin-City, Nigeria

While numerous studies examine the epidemiology and molecular characterization of Staphylococcus aureus in most developed countries, the detailed molecular characterization and molecular epidemiology of S. aureus strains and clones in Africa is lacking. We determined the molecular epidemiology and virulence of 81 non-duplicate isolates of S. aureus from Benin-City, Nigeria, collected during January–July 2016, and compared with global strains. Forty-seven isolates (58.0%) were found to be methicillin-sensitive Staphylococcus aureus (MSSA), while 34 (42.0%) were methicillin-resistant Staphylococcus aureus (MRSA). ST152-MSSA (24.7%) and ST7-MRSA-V (19.8%) were the dominant groups identified, which were not genetically related to global predominant strains, but rather exhibited regional dominance. An interesting finding of the study was the presence of highly related strains in the region, which differed primarily in their methicillin resistance gene carriage, staphylococcal cassette chromosome mec (SCCmec), with 99.4–99.7% relatedness between the genomes of the strains within the MRSA–MSSA pairs. This suggests that the strains within a pair are experiencing gain or loss of SCCmec within local conditions, with evolution continuing to diversify the strains to a small degree. This study represents the most comprehensive genetic and virulence study of S. aureus in Nigeria.

Skin Infections Caused by Staphylococcus aureus

Staphylococcus aureus is the most common pathogen involved in skin infections worldwide, regardless of the patient's age, the climate or geographical area. The main skin clinical manifestations can be linked to a few toxins produced by the bacteria, which give rise to a rich and varied clinical spectrum. Panton Valentine leucocidin, exfoliatins, enterotoxins and toxin shock syndrome toxin 1 are the main toxins involved in most dermatological manifestations associated with S. aureus. Other less frequent cutaneous manifestations can occur in endocarditis, bacteraemia. Currently, the most important event is worldwide emergence of community-acquired S. aureus resistant to methicillin (CA-MRSA), mainly causing skin infections.

Molecular epidemiology of Staphylococcus aureus from Lambaréné, Gabon

While there is an abundance of data on the epidemiology and molecular typing of Staphylococcus aureus, especially those carrying Panton-Valentine leucocidin (PVL) genes or mecA from Western Europe, Northern America and Australia, comparably few studies target African strains. In this study, we characterised genes associated with virulence and resistance, as well the phylogenetic background of S. aureus from healthy carriers and outpatients in Gabon. In total, 103 isolates from 96 study participants were characterised. Seventy-nine isolates originated from throat swabs and 24 isolates from skin lesions. Three isolates carried mecA, although only one, belonging to CC8-MRSA-IV [PVL+] 'USA300', was found to be phenotypically oxacillin-resistant; two CC88-MRSA-IV isolates appeared to be oxacillin-susceptible. PVL genes were common, with a total of 44 isolates (43 %) found to be PVL-positive. CC15-MSSA [PVL+] (n = 29) and CC152-MSSA [PVL+] (n = 9) were the predominant clones among the PVL-positive isolates. Among PVL-negative isolates, CC5-MSSA (n = 12), CC101-MSSA (n = 10) and CC15 (n = 9) were the most frequent. A hitherto undescribed multilocus sequence type of S. schweitzeri was detected twice in unrelated patients. The data emphasise a need for further studies on the role of PVL in African populations and the clinical significance of S. schweitzeri.

Staphylococcus aureus Toxins and Diabetic Foot Ulcers: Role in Pathogenesis and Interest in Diagnosis

Infection of foot ulcers is a common, often severe and costly complication in diabetes. Diabetic foot infections (DFI) are mainly polymicrobial, and Staphylococcus aureus is the most frequent pathogen isolated. The numerous virulence factors and toxins produced by S. aureus during an infection are well characterized. However, some particular features could be observed in DFI. The aim of this review is to describe the role of S. aureus in DFI and the implication of its toxins in the establishment of the infection. Studies on this issue have helped to distinguish two S. aureus populations in DFI: toxinogenic S. aureus strains (harboring exfoliatin-, EDIN-, PVL- or TSST-encoding genes) and non-toxinogenic strains. Toxinogenic strains are often present in infections with a more severe grade and systemic impact, whereas non-toxinogenic strains seem to remain localized in deep structures and bone involving diabetic foot osteomyelitis. Testing the virulence profile of bacteria seems to be a promising way to predict the behavior of S. aureus in the chronic wounds.

Community-associated methicillin-resistant Staphylococcus aureus in non-outbreak skin infections

The aim of this study was to determine the prevalence of Staphylococcus aureus and risk factors for the acquisition of MRSA (Methicillin Resistant Staphylococcus aureus) as the main cause of skin and soft tissue infections. S. aureus were characterized for the presence of PVL, TSST-1 and mecA genes. SCCmec typing was carried out in mecA positive strains and PFGE was performed only in these strains. During the study period, 127 outpatients attending a dermatology clinical the Botucatu Medical School, a regional tertiary hospital in Botucatu, Sao Paulo, Brazil, were diagnosed with active skin infections. A total 66 (56.9%) S. aureus strains were isolated. The methicillin resistance gene mecA was detected in seven (10.6%) S. aureus strains. The SCCmec types detected in the seven mecA-positive S. aureus strains were type Ia in one, type II in three, and type IV in three. The PVL gene was detected in 10 (15.1%) in sensitive strains. Pulsed field gel electrophoresis revealed non-clonal diversity among the isolates. The risk factors associated with MRSA acquisition in this study were previous ciprofloxacin use and working in a healthcare environment. The risk factors indicate plausible routes of CA-MRSA transmission among the subjects studied.

Evidence for increasing severity of community-onset boils and abscesses in UK General Practice

In England, hospital admissions for severe staphylococcal boils and abscesses trebled between 1989 and 2004. We investigated this trend using routine data from primary and secondary care. We used The Health Improvement Network (THIN), a large primary-care database and national data on hospital admissions from Hospital Episode Statistics (HES). Time trends in the incidence of primary-care consultations for boils and abscesses were estimated for 1995-2010. HES data were used to calculate age-standardized hospital admission rates for boils, abscesses and cellulitis. The incidence of boil or abscess was 450 [95% confidence interval (CI) 447-452] per 100 000 person-years and increased slightly over the study period (incidence rate ratio 1·005, 95% CI 1·004-1·007). The rate of repeat consultation for a boil or abscess increased from 66 (95% CI 59-73) per 100 000 person-years in 1995 to peak at 97 (95% CI 94-101) per 100 000 person-years in 2006, remaining stable thereafter. Hospital admissions for abscesses, carbuncles, furuncles and cellulitis almost doubled, from 123 admissions per 100 000 in 1998/1999 to 236 admissions per 100 000 in 2010/2011. Rising hospitalization and recurrence rates set against a background of stable community incidence suggests increased disease severity. Patients may be experiencing more severe and recurrent staphylococcal skin disease with limited treatment options.

Molecular Characterization of Invasive Staphylococcus aureus Infection in Central New York Children: Importance of Two Clonal Groups and Inconsistent Presence of Selected Virulence Determinants

BACKGROUND

The genetic makeup of circulating Staphylococcus aureus (SA) populations varies by region. The extent to which SA virulence determinants contribute to the severity of pediatric infections is poorly understood. The study objective was to describe the genetic population of invasive SA (ISA) isolates from children in the Central New York (CNY) area and the prevalence of selected virulence genes.

METHODS

Clinical and demographic information for hospitalized children <19 years of age with community-onset or community-associated ISA infections, determined from clinical microbiology records, was extracted from medical records from Upstate Golisano Children's Hospital in CNY. Antibiotic susceptibility was assessed, and available isolates were genotyped and tested for the presence of selected virulence determinants. Associations between clinical and laboratory findings were evaluated using standard statistical techniques.

RESULTS

Ninety patients with ISA disease diagnosed between 2007 and 2010 were included in the study; 74% were due to methicillin-susceptible SA (MSSA). The most common clinical diagnosis was bacteremia. Fifty-seven of 90 isolates were available for further testing. The SA pulsed-field gel electrophoresis type, agr type, and clonal complexes most commonly isolated were USA300 (n = 25, 44%), agr1 (n = 30, 52%), and CC8 (n = 25, 44%), respectively. USA300 strains were more likely to be associated with deep abscesses (P = .007), whereas non-USA300 strains were associated with medical device infections (P = .018). Isolates from patients with deep abscesses and pneumonia were more likely to carry luk-PV genes (P = .023 and P = .051, respectively).

CONCLUSIONS

MSSA remains an important problem of pediatric ISA infection in our region and results from genetically diverse SA populations.

Skin and soft tissue infections due to Panton-Valentine leukocidin producing Staphylococcus aureus

OBJECTIVE

The authors had for aim to describe the epidemiological and clinical characteristics, and the treatment of patients presenting with skin and soft tissue infections due to Panton-Valentine leukocidin (PVL) producing Staphylococcus aureus in the Nord-Pas-de-Calais (NPDC) region, North of France.

METHODS

We included patients presenting with PVL producing S. aureus infection from seven hospitals in the NPDC region, between February 2004 and April 2008. We retrospectively collected patient data using a standardized questionnaire. The features of patients presenting with skin and soft tissue were then analyzed.

RESULTS

PVL producing S. aureus was isolated from 64 patients. Fifty-four patients presented with skin and soft tissue infections. The mean age of patients was 23.8 years (63% male patients). The mean number of persons living with the infected patient was 4.5 (vs. 2.5 in NPDC). The lesions were abscesses with inflammatory signs in 64.8% of the cases (20% were necrotic). Among the patients, 70.3% carried a methicillin resistant strain. Antibiotics per os were used for 83.3% of patients; the first-line antibiotics were considered inadequate in 53.3% of the cases. Among the patients, 83.3% underwent surgery. Fourteen out of 38 patients with available data had been exposed to antibiotic therapy during the three months before hospital management.

CONCLUSION

Recent exposure to antibiotics and living with a high number of persons are reasons to suspect a PVL producing S. aureus infection in patients with skin abscess.

High genetic diversity among community-associated Staphylococcus aureus in Europe: results from a multicenter study

Background

Several studies have addressed the epidemiology of community-associated Staphylococcus aureus (CA-SA) in Europe; nonetheless, a comprehensive perspective remains unclear. In this study, we aimed to describe the population structure of CA-SA and to shed light on the origin of methicillin-resistant S. aureus (MRSA) in this continent.

Methods and Findings

A total of 568 colonization and infection isolates, comprising both MRSA and methicillin-susceptible S. aureus (MSSA), were recovered in 16 European countries, from community and community-onset infections. The genetic background of isolates was characterized by molecular typing techniques (spa typing, pulsed-field gel electrophoresis and multilocus sequence typing) and the presence of PVL and ACME was tested by PCR. MRSA were further characterized by SCCmec typing. We found that 59% of all isolates were associated with community-associated clones. Most MRSA were related with USA300 (ST8-IVa and variants) (40%), followed by the European clone (ST80-IVc and derivatives) (28%) and the Taiwan clone (ST59-IVa and related clonal types) (15%). A total of 83% of MRSA carried Panton-Valentine leukocidin (PVL) and 14% carried the arginine catabolic mobile element (ACME). Surprisingly, we found a high genetic diversity among MRSA clonal types (ST-SCCmec), Simpson’s index of diversity = 0.852 (0.788–0.916). Specifically, about half of the isolates carried novel associations between genetic background and SCCmec. Analysis by BURP showed that some CA-MSSA and CA-MRSA isolates were highly related, suggesting a probable local acquisition/loss of SCCmec.

Conclusions

Our results imply that CA-MRSA origin, epidemiology and population structure in Europe is very dissimilar from that of USA.

Antibacterial resistance, genes encoding toxins and genetic background among Staphylococcus aureus isolated from community-acquired skin and soft tissue infections in France: a national prospective survey

The epidemiology of staphylococcal community-acquired skin and soft tissues infections (CA-SSTIs) has changed dramatically. We described prospectively the characteristics of the Staphylococcus aureus isolated from 71 non-teaching French hospitals and implicated in CA-SSTIs: antimicrobial susceptibility (mecA polymerase chain reaction [PCR], disk diffusion method), virulence factor gene (sea, tst, pvl) prevalence and genetic background (agr allele). During November 2006, 235 strains were collected (wound infection: 51%, abscess: 21%, whitlow: 8%, diabetic foot: 7%, furunculosis: 3%). sea, tst and pvl were identified in 22.1, 13.2 and 8.9% strains, respectively. agr allele 1 was the most frequently encountered genetic background, whatever the methicillin susceptibility. Among the 34 methicillin-resistant S. aureus (MRSA, 14.5% of all S. aureus), only one strain (2.9%) harboured pvl (belonging to the European ST80 clone), four (11.8%) tst (belonging to two endemic French clones) and 18 (52.9%) sea gene (mainly the Lyon clone). According to their in vitro activity, pristinamycin or trimethoprim/sulfamethoxazole could be considered as first-choice antibiotics. To date, the international pvl-positive MRSA clones have not spread in France. MRSA strains isolated from putative CA-SSTIs exhibited a genetic and phenotypic background of hospital-acquired (HA) clones. National survey should be continued, in order to monitor the emergence of virulent clones.

Community-Associated Methicillin-Resistant Staphylococcus Aureus Skin and Soft Tissue Infections

The prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing globally and in Singapore. Skin and soft tissue infections (SSTIs) are the most common manifestations, ranging from common furuncles to the rare but life-threatening necrotizing fasciitis. Surgical drainage and debridement where feasible are the mainstay of therapy, whereas MRSA-active antibiotics are essential when surgery is not possible or as adjunctive therapy for severe and/or complicated SSTIs. In itself, the continued inexorable rise in CA-MRSA rates poses difficult challenges for primary healthcare and hospital infection control. Innovative approaches are required to mitigate its impact in both the community and hospital settings.

Clinical manifestations and outcome of skin infections caused by the community-acquired methicillin-resistant Staphylococcus aureus clone ST80-IV

BACKGROUND

Several Panton-Valentin leukocidin-positive clones of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) are spreading worldwide. The European clone ST80-IV is the main CA-MRSA clone in Europe. There is no reported study of the specific clinical manifestations and outcome of skin infections caused by the clone ST80-IV, using strict definitions of skin diseases.

METHODS

Single-centre observational prospective cohort of S. aureus skin infections caused by the clone ST80-IV.

RESULTS

From November 1999 to October 2009, we diagnosed skin infections due to the clone ST80-IV in 20 patients (median age 28 years, median 27; range 1-66). All the isolates had all the following characteristics: lukPV, etd and edin gene-positive, agr 3 allele, spa-type t044 and ST80. All the isolates were resistant to beta-lactam agents, kanamycin, tetracycline and fusidic acid. During the study period, the 20 patients had the following manifestations: 19 primary abscesses (18 single abscess and one patient with two), eight furuncles, four folliculitis, one case of cellulitis, one wound infection and one felon. Surgical treatment and drainage was required for all the primary abscesses. The infections occurred mainly in the perineal area (50%). No secondary infections occurred in family members. Despite strict hygiene measures, systemic antibiotics and nasal mupirocine, four patients (20%) had recurrent skin infections over a period of a few months to 6 years.

CONCLUSIONS

The CA-MRSA clone ST80-IV is responsible for suppurative skin infections such as furuncles and abscesses, which can recur over a period of several years.

Risk factors for community-associated Staphylococcus aureus infections: results from parallel studies including methicillin-resistant and methicillin-sensitive S. aureus compared to uninfected controls

Despite the increasing burden of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, the risk factors are not well understood. We conducted a hypothesis-generating study using three parallel case-control studies to identify risk factors for CA-MRSA and community-associated methicillin-susceptible S. aureus (CA-MSSA) infections. In the multivariate model, antimicrobial use in the 1-6 months prior to culture was associated with CA-MRSA infection compared to CA-MSSA [adjusted odds ratio (aOR) 1·7, P=0·07] cases. Antimicrobial use 1-6 months prior to culture (aOR 1·8, P=0·04), history of boils (aOR 1·6, P=0·03), and having a household member who was a smoker (aOR 1·3, P=0·05) were associated with CA-MRSA compared to uninfected community controls. The finding of an increased risk of CA-MRSA infection associated with prior antimicrobial use highlights the importance of careful antimicrobial stewardship.

Acute osteomyelitis in children: the pathogenesis revisited?

PURPOSE OF THE STUDY

The present study reviews our experience of acute hematogenous osteomyelitis in 450 children over a period of 20 years from 1985 to 2004 at the Nouméa Territorial Hospital in New Caledonia. The objective was to formulate a new theory of the pathogenesis of this affection and to report our research on the disparity in the pathology between temperate countries and our own tropical Pacific area.

PATIENT AND METHODS

Only children with an initially normal X-ray and showing symptoms for less than one week were included in the study. Subacute osteomyelitis, infant osteoarthritis and spinal and sacroiliac joint infections were all excluded. All children were treated according to a preestablished protocol including: clinical examination; blood tests; ultrasound, to determine the presence and size of the periosteal elevation and to exclude soft tissue abscess and frequent pyomyositis. Ultrasound was used in the decision to treat with antibiotics alone or with surgery. Computed Tomography was used for deep structures assessment and medical therapy guidance Surgery was limited to open drainage of the subperiosteal abscess only. Regular follow-up of outpatients was continued until normal blood test and X-ray results were achieved.

RESULTS AND DISCUSSION

Four hundred and fifty children with a diagnosis of acute hematogenous osteomyelitis were identified, giving an average incidence of 22 new cases per year (range, 12-35). This incidence was two to five times as high as found in Europe. Fifty-three percent of our cases required surgical drainage (vs. 20 % in Europe). Ethnically, 60 % of the children were Melanesian and 20 % Polynesian (both represented less than 50 % of the local population). A similar incidence, about four times as high as in the population of European descent, was reported in Polynesians by our neighbors in New Zealand. The limbs were affected in 90 % of cases, and specifically lower limbs in 70 %. Multiple osseous lesions and systemic infection were recorded in 43 children (9.5 %). Blood cultures and surgical samples were positive in 80 % of cases, and otherwise negative. All the children were successfully treated, without chronic evolution or sequelae needing secondary surgery. The predominant microorganisms isolated were Staphylococcus aureus, in 81 % of cases, none of which were methicillin-resistant, and group A Streptococcus in 7.5 % of cases. A previous study of soft-tissue S. aureus infection showed the presence of Panton-Valentine Leukocidin (PVL) genes in 89 % of cases. These very infrequent genes are responsible for leukotoxic apoptosis, producing leukocidin, causing local acute aggressiveness. A parallel study, in progress for more than a year, is focusing on detecting PVL genes in S. aureus isolated from acute osteomyelitis: in the first nine children analyzed, PVL genes were likewise detected in 89 % of the S. aureus isolated, with no methicillin resistance. Ultrasonography allowed positive diagnosis in 64 % of cases on the day of admission and 84 % by the second day. Because of this very early presence of subperiosteal abscess at the beginning of the disease, and several other issues raised in the present study, we believe that Trueta's theory of acute osteomyelitis pathogenesis does not provide any logical explanation for our anatomoclinical observations. We believe that the primary focus of infection is in the osteoperiosteal area rather than under the growth plate in the metaphyseal bone. The term of Acute Osteo-Periostitis would therefore be much more suitable. A history of blunt trauma was found in 63 % of cases in the present series, and often reported in the literature. We speculate that two forms of infection fixation may develop: a local form, where bacteria carried by the blood stream reach a subperiosteal edema or hematoma secondary to blunt trauma, which is in our opinion the most frequent cause; and a general form, where fixation occurs as single or multifocal osteoperiostitis, and multivisceral locations in severe forms of septicemia. The disparity in this pathology between temperate countries and our own tropical Pacific area is certainly due to PVL-positive S. aureus and ethnic factors. The high prevalence of Melanesian and Polynesian patients confirms that they are at high risk of musculoskeletal infection in New Caledonia as in other Pacific countries, and it is possible that these ethnic groups are genetically susceptible to PVL-positive strains.

LEVEL OF EVIDENCE

Level IV. Retrospective case series.

Skin and soft tissue infections caused by community-associated methicillin-resistant staphylococcus aureus among children in China

AIM

To investigate the characteristic of community-associated methicillin-resistant staphylococcus aureus (CA-MRSA) skin and soft tissue infections (SSTIs) among children in China.

METHODS

Forty-seven children with CA-MRSA SSTIs were enrolled in this study. Clinical information was collected and analysed. The strains from the children were analysed by multilocus sequence typing (MLST), staphylococcus cassette chromosome mec (SCCmec) typing and spa typing. The Panton-Valentine leukocidin (PVL) gene was also detected.

RESULTS

The majority of the 47 cases were impetigo (20; 42.6%) and abscesses (14; 29.8%). The rest was cellulites, infected wounds, omphalitis, paronychia and conjunctivitis combined folliculitis. Thirty-two of the isolates (68.1%) were PVL-positive, and the abscesses infected with PVL-positive strains usually required incision and drainage (87.5% vs. 16.7%, p = 0.026). Most of the isolates belonged to ST type 59, which accounted for 46.8%, followed by ST1 (7/47, 14.9%) and ST910 (5/47, 10.6%). The clone of ST59-MRSA-IV with t437 was the most prevalent one. The multiresistant rate of these strains was 93.6%.

CONCLUSION

The most common disease of CA-MRSA SSTIs was impetigo, and PVL-positive abscess was associated with incision and drainage. ST59-MRSA-IV with t437 was the most prevalent clone, and the multiresistant rate was high in Chinese children.

Toxin profiling of Staphylococcus aureus strains involved in varicella superinfection

The most common complications of varicella are bacterial skin and soft tissue infections, generally due to Staphylococcus aureus and group A beta-hemolytic streptococci. The aim of this study was to characterize the toxin and antibiotic resistance profiles of S. aureus isolates involved in varicella complications. Between 2002 and 2007, the French Reference Centre for Staphylococci collected 58 S. aureus isolates involved in varicella superinfection. All the isolates were characterized by screening for 12 toxin genes, agr typing, and mecA gene detection; some isolates were also studied by spa typing, multilocus sequence typing (MLST), and resistance profiling. A major toxin gene was detected in 53% (31/58) of the isolates (genes for exfoliative toxins A and B, 17.2%; Panton-Valentine leukocidin gene, 8.6%; toxic shock syndrome toxin 1 gene, 27.6%). Most clinical manifestations were directly compatible with the classical activity of these toxins. Nineteen isolates (33%) were resistant to methicillin, and 12 of these isolates belonged to an emerging agr-2, ST5 clone that harbors the toxic shock syndrome toxin 1 gene. These data should be considered in the management and treatment of patients with varicella complicated by S. aureus superinfection. Antibiotics that decrease toxin production, such as clindamycin, may provide benefit, and their efficacy against bacterial superinfections in children with varicella should be studied.

Augmented production of Panton-Valentine leukocidin toxin in methicillin-resistant and methicillin-susceptible Staphylococcus aureus is associated with worse outcome in a murine skin infection model

The role of Panton-Valentine leukocidin (PVL) in Staphylococcus aureus infections is controversial. We used a mouse model of skin infection to compare the virulence of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains with different levels of PVL production. Differences in PVL production were not associated with mutations in the genes lukS-PV and lukF-PV. However, MSSA and MRSA strains that produced high levels of PVL caused larger skin abscesses, higher bacterial burdens, and more tissue inflammation than did low-PVL-producing strains. Together, these data suggest that (1) the effect of PVL on the pathogenesis of staphylococcal infection may depend on the level of toxin produced and (2) many strains of MSSA that cause soft-tissue infections produce higher levels of PVL than do MRSA strains.

Emergence of SCCmec type IV and SCCmec type V methicillin-resistant Staphylococcus aureus containing the Panton-Valentine leukocidin genes in a large academic teaching hospital in central Switzerland: external invaders or persisting circulators?

The hospital epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has changed in the past few years due to the encroachment of community-associated MRSA (CA-MRSA) strains into health care settings. MRSA strains that were isolated during a 2-year period from patients of the Luzerner Kantonsspital were analyzed to elucidate their epidemiology. Moreover, extended surveillance of individuals who were contacts of those patients was carried out for 6 months to identify the routes of spread and to assess the quality of the infection control measures used in our setting. Patient data were collected to distinguish CA-MRSA strains from health care-associated MRSA (HA-MRSA) strains by epidemiological criteria, as defined by the Centers for Disease Control and Prevention (CDC). On the basis of the CDC definition, the majority of the strains were considered to be HA-MRSA. However, 87% of them belonged to staphylococcal cassette chromosome mec (SCCmec) types IV and V, which are traditionally associated with CA-MRSA. Surprisingly, classical nosocomial SCCmec types I and II represented a minority, whereas SCCmec type III was completely absent. By PFGE analysis, four predominant clonal lineages and 21 highly variable sporadic genotypes were detected. Twenty-eight percent of the MRSA strains studied carried the genes encoding the Panton-Valentine leukocidin (PVL), of which 21% and 83% were associated with SCCmec types IV and V, respectively. Among 289 contact individuals screened for MRSA carriage throughout the extended surveillance, a single secondary patient was discovered. The possibility of nosocomial transmission could be excluded. The high proportions of SCCmec type IV and V strains as well as PVL-positive strains suggest strong infiltration of CA-MRSA into our institution. Moreover, the low endemic prevalence of MRSA demonstrates that current infection control measures are sufficient to limit its spreading and the emergence of large epidemic outbreaks.

Aortic root abscess without involvement of the aortic valve in a child caused by Panton-Valentine leukocidin-positive staphylococci

Aortic root abscess without any involvement of the aortic valve is extremely rare. This report describes an 11-year-old girl with subperiosteal abscess due to a virulent organism called Panton-Valentine leukocidin-secreting staphylococci. Although her initial transthoracic echocardiogram did not show any cardiac abnormality, she subsequently experienced an aortic root abscess communicating with the left ventricle. The aortic valve was unaffected, and no other cardiac abnormality was detected at any stage. The girl made a complete recovery after surgical intervention for her aortic root abscess, which was increasing in size despite antibiotic therapy. Patients with such illnesses require close monitoring with repeated expert echocardiography and timely intervention.

Presence and molecular epidemiology of virulence factors in methicillin-resistant Staphylococcus aureus strains colonizing and infecting soldiers

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as an important cause of skin and soft-tissue infections (SSTI). The understanding of the molecular epidemiology and virulence of MRSA continues to expand. From January 2005 to December 2005, we screened soldiers for MRSA nasal colonization, administered a demographic questionnaire, and monitored them prospectively for SSTI. All MRSA isolates underwent molecular analysis, which included pulsed-filed gel electrophoresis (PFGE) and PCR for Panton-Valentine leukocidin (PVL), the arginine catabolic mobile element (ACME), and the staphylococcal cassette chromosome mec (SCCmec). Of the 3,447 soldiers screened, 134 (3.9%) had MRSA colonization. Of the 3,066 (89%) who completed the study, 39 developed culture-confirmed MRSA abscesses. Clone USA300 represented 53% of colonizing isolates but was responsible for 97% of the abscesses (P < 0.001). Unlike colonizing isolates, isolates positive for USA300, PVL, ACME, and type IV SCCmec were significantly associated with MRSA abscess isolates. As determined by multivariate analysis, risk factors for MRSA colonization were a history of SSTI and a history of hospitalization. Although various MRSA strains may colonize soldiers, USA300 is the most virulent when evaluated prospectively, and PVL, ACME, and type IV SCCmec are associated with these abscesses.

[Methicillin-resistant Staphylococcus aureus (MRSA). Relevance in dermatology]

Because of the increasing incidence of resistance to beta-lactam antibiotics, dermatologists will be increasingly confronted with methicillin-resistant S. aureus (MRSA) strains which display a great variability of their virulence factors. In view of the high mortality of systemic MRSA infections (estimated 700-1.500 deaths per year in Germany), dermatologists should be well aware of the various aspects of diagnosis, therapy and prevention of this problem bacteria. Adequate screening measures must be in place to identify high-risk patients and institute appropriate prophylactic measures and therapy. If only colonization is present, topical antiseptic measures are sufficient. If an infection is present, either systemic or topical therapeutic approaches may be indicated. We review the role of MRSA infection and colonization in skin diseases.

Spread of invasive Spanish Staphylococcus aureus spa-type t067 associated with a high prevalence of the aminoglycoside-modifying enzyme gene ant(4')-Ia and the efflux pump genes msrA/msrB

OBJECTIVES

We carried out a nationwide study aimed at the determination of the molecular epidemiology and antibiotic resistance mechanisms of invasive Staphylococcus aureus in 21 Spanish hospitals.

METHODS

The distributions of molecular markers, including antibiotic resistance genes, were investigated in 203 S. aureus, comprising 90 methicillin-resistant S. aureus (MRSA) and 113 methicillin-susceptible S. aureus (MSSA). Antimicrobial susceptibility was determined by standard methods. Panton-Valentine leucocidin (PVL) detection, staphylococcal cassette chromosome mec (SCCmec) types and agr types were performed/determined by PCR. All isolates were genotyped by PFGE after digestion of chromosomal DNA with SmaI. Multilocus sequence typing and spa-typing were also performed.

RESULTS

In MRSA isolates, 74.4% were agr allotype II and were positive for SCCmec IV. Sixty-nine spa-types were identified, 18 in MRSA and 57 in MSSA. Both MRSA and MSSA variants were detected in six spa-types (8.7%). The majority of S. aureus (51.2%) were grouped into four spa-types (t067, t002, t012 and t008). The spa-type t067 was detected in 18 of the 21 (85.7%) participating hospitals, including both MRSA and MSSA in six of them; in total, 25.9% of our isolates were spa-type t067 (49% in MRSA) in comparison with 0.6% in a central spa-typing database. The prevalence of the ant(4')-Ia and msrA/msrB genes was significantly higher in the MRSA spa-type t067 than in the other MRSA spa-types. Association between spa-type t067 and ST125 is described here for the first time. A high prevalence (36.4%) of PVL-positive MSSA was detected.

CONCLUSIONS

A higher than expected prevalence of spa-type t067 isolates was found among invasive MRSA in Spain. The oxacillin, tobramycin, erythromycin and ciprofloxacin resistance profile of spa-type t067 isolates was linked to the presence of ant(4')-Ia and msrA or msrB genes.

Brain abscess due to Panton-Valentine leukocidin-positive Staphylococcus aureus

Panton-Valentine leukocidin (PVL) is a cytotoxin produced by Staphylococcus aureus that exhibits highly specific lytic activity against polymorphonuclear cells, monocytes, and macrophages. A 34-year-old man admitted for right parietal brain abscess and thickened dura mater in close proximity to a lytic bone lesion is presented. The abscess culture yielded methicillin-sensitive S. aureus that produced PVL. The patient did well after surgery and antibiotic treatment. A hematogenous infection, route of bone infection with progression to dura mater and brain parenchyma was hypothesized. To our knowledge this is the first reported case of a brain abscess due to PVL-positive S. aureus.

[Multiple abscesses in immunocompetent patients caused by Panton-Valentine leukocidin positive Staphylococcus aureus]

We report cases of immunocompetent patients showing multiple abscesses by a Panton-Valentine leukocidin (PVL) positive Staphylococcus aureus. PVL is considered to be an important virulence factor. The most common manifestations by this pathogen are recurrent or multiple abscesses of the skin. Seldom necrotizing pneumonia with high mortality occurs. Even methicillin-resistant PVL positive isolates have been identified in Germany. Only appropriate infection control measures in combination with antimicrobial therapy resulted in successful eradication of this pathogen. Dermatologists should be informed about this specific type of infection and about the appropriate infection control measures.

Prevalence of genes encoding extracellular virulence factors among meticillin-resistant Staphylococcus aureus isolates from the University Hospital, Olomouc, Czech Republic

A rather fast and complicated progression of an infection caused by some strains of Staphylococcus aureus could be associated with the expression and co-action of virulence factor complexes in these strains. This study screened the antibiotic susceptibility and prevalence of virulence markers in isolates of meticillin-resistant S. aureus (MRSA) obtained from patients hospitalized at the University Hospital in Olomouc, Czech Republic. A total of 100 isolates was screened for 13 genes encoding extracellular virulence determinants (tst, pvl, eta, etb, sea, seb, sec, sed, see, seg, seh, sei and sej) and for their distribution in sample types. Eighty-nine isolates were positive for at least one of the genes. Genes for etb, pvl, see and seh were not detected in any of the MRSA isolates. No statistically significant differences in the occurrence of the determinants studied among sample types were found.

Panton-Valentine leukocidin: raising practitioner awareness

Media reports have focused recently on methicillin-resistant Staphylococcus aureus (MRSA). Panton-Valentine leukocidin is a toxin carried by MRSA. With reported increases in community-acquired MRSA, this article seeks to raise practitioner awareness of this toxin and its effects on dermal tissue. A case study and anecdotal evidence is given.

Community-Onset Methicillin-Resistant Staphylococcus aureus Skin and Soft-Tissue Infections: Impact of Antimicrobial Therapy on Outcome

BACKGROUND

Conflicting data exist on the role of antimicrobial therapy for the treatment of uncomplicated community-onset methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections (SSTIs).

METHODS

We performed a retrospective cohort study of 492 adult patients with 531 independent episodes of community-onset MRSA SSTIs, which consisted of abscesses, furuncles/carbuncles, and cellulitis, at 2 tertiary care medical centers. The purpose of the study was to determine the impact of active antimicrobial therapy (i.e., the use of an agent to which the organism is susceptible) and other potential risk factors on the outcome for patients with uncomplicated community-onset MRSA SSTIs. Treatment failure was the primary outcome of interest and was defined as worsening signs of infection associated with microbiological and/or therapeutic indicators of an unsuccessful outcome. Bivariate analyses and logistic regression analyses were preformed to determine predictors of treatment failure.

RESULTS

An incision and drainage procedure was performed for the majority of patients. Treatment failure occurred in 45 (8%) of 531 episodes of community-onset MRSA SSTI. Therapy was successful for 296 (95%) of 312 patients who received an active antibiotic, compared with 190 (87%) of 219 of those who did not (P=.001 in bivariate analysis). Use of an inactive antimicrobial agent was an independent predictor of treatment failure on logistic regression analysis (adjusted odds ratio, 2.80; 95% confidence interval, 1.26-6.22; P=.01).

CONCLUSIONS

Our findings suggest that certain patients with SSTIs that are likely caused by MRSA would benefit from treatment with an antimicrobial agent with activity against this organism.

Methicillin-resistant S. aureus infections among patients in the emergency department

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly recognized in infections among persons in the community without established risk factors for MRSA.

METHODS

We enrolled adult patients with acute, purulent skin and soft-tissue infections presenting to 11 university-affiliated emergency departments during the month of August 2004. Cultures were obtained, and clinical information was collected. Available S. aureus isolates were characterized by antimicrobial-susceptibility testing, pulsed-field gel electrophoresis, and detection of toxin genes. On MRSA isolates, we performed typing of the staphylococcal cassette chromosome mec (SCCmec), the genetic element that carries the mecA gene encoding methicillin resistance.

RESULTS

S. aureus was isolated from 320 of 422 patients with skin and soft-tissue infections (76 percent). The prevalence of MRSA was 59 percent overall and ranged from 15 to 74 percent. Pulsed-field type USA300 isolates accounted for 97 percent of MRSA isolates; 74 percent of these were a single strain (USA300-0114). SCCmec type IV and the Panton-Valentine leukocidin toxin gene were detected in 98 percent of MRSA isolates. Other toxin genes were detected rarely. Among the MRSA isolates, 95 percent were susceptible to clindamycin, 6 percent to erythromycin, 60 percent to fluoroquinolones, 100 percent to rifampin and trimethoprim-sulfamethoxazole, and 92 percent to tetracycline. Antibiotic therapy was not concordant with the results of susceptibility testing in 100 of 175 patients with MRSA infection who received antibiotics (57 percent). Among methicillin-susceptible S. aureus isolates, 31 percent were USA300 and 42 percent contained pvl genes.

CONCLUSIONS

MRSA is the most common identifiable cause of skin and soft-tissue infections among patients presenting to emergency departments in 11 U.S. cities. When antimicrobial therapy is indicated for the treatment of skin and soft-tissue infections, clinicians should consider obtaining cultures and modifying empirical therapy to provide MRSA coverage.

Characterization of a strain of community-associated methicillin-resistant Staphylococcus aureus widely disseminated in the United States

A highly stable strain of Staphylococcus aureus with a pulsed-field gel electrophoresis type of USA300 and multilocus sequence type 8 has been isolated from patients residing in diverse geographic regions of the United States. This strain, designated USA300-0114, is a major cause of skin and soft tissue infections among persons in community settings, including day care centers and correctional facilities, and among sports teams, Native Americans, men who have sex with men, and military recruits. The organism is typically resistant to penicillin, oxacillin, and erythromycin (the latter mediated by msrA) and carries SCCmec type IVa. This strain is variably resistant to tetracycline [mediated by tet(K)]; several recent isolates have decreased susceptibility to fluoroquinolones. S. aureus USA300-0114 harbors the genes encoding the Panton-Valentine leucocidin toxin. DNA sequence analysis of the direct repeat units within the mec determinant of 30 USA300-0114 isolates revealed differences in only a single isolate. Plasmid analysis identified a common 30-kb plasmid that hybridized with blaZ and msrA probes and a 3.1-kb cryptic plasmid. A 4.3-kb plasmid encoding tet(K) and a 2.6-kb plasmid encoding ermC were observed in a few isolates. DNA microarray analysis was used to determine the genetic loci for a series of virulence factors and genes associated with antimicrobial resistance. Comparative genomics between USA300-0114 and three other S. aureus lineages (USA100, USA400, and USA500) defined a set of USA300-0114-specific genes, which may facilitate the strain's pathogenesis within diverse environments.