Panton-Valentine Leucocidin-related disease in England and Wales

Prevalence of Panton-Valentine leukocidin in methicillin-resistant Staphylococcus aureus clinical isolates at a university hospital in Northern Cyprus: a pilot study

Objective

Panton-Valentine leukocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (MRSA) is a healthcare problem worldwide. There are no reports on the virulence characteristics of MRSA in Northern Cyprus (NC). This study aimed to determine the presence of pvl among MRSA isolates from patients admitted to a university hospital in NC using molecular methods. Fifty S. aureus strains were included in this study. BD Phoenix automated identification system was used for bacterial identification and antibiotic susceptibility testing. Methicillin resistance was confirmed by disc diffusion assay. Presence of nuc and mecA genes was tested by multiplex PCR. Detection of pvl gene was performed by single-target PCR.

Results

Out of 50 S. aureus isolates identified as MRSA by BD Phoenix system, 3 were susceptible to cefoxitin with disc diffusion assay and were confirmed as methicillin-sensitive S. aureus (MSSA). All isolates (n = 50, 100%) tested positive for the presence nuc gene and 68% (n = 34/50) were mecA positive. pvl was detected in 27.7% (n = 13/47) of the MRSA isolates. Among PVL-positive MRSA isolates, 69.2% (9/13) were inpatients. PVL-MRSA was more common in isolates from deep tracheal aspirate (30.8%, 4/13) and abscess/wound (23.1%, 3/13). This represents the first study of PVL presence among MRSA in hospital setting in NC.

Staphylococcus aureus colonization and acquisition of skin and soft tissue infection among Royal Marines recruits: a prospective cohort study

OBJECTIVES

Skin and soft tissue infections (SSTIs) are a serious health issue for military personnel. Of particular importance are those caused by methicillin-resistant Staphylococcus aureus and Panton-Valentine leucocidin (PVL)-positive S. aureus (PVL-SA), as they have been associated with outbreaks of SSTIs. A prospective observational study was conducted in Royal Marine (RM) recruits to investigate the prevalence of PVL-SA carriage and any association with SSTIs.

METHODS

A total of 1012 RM recruits were followed through a 32-week training programme, with nose and throat swabs obtained at weeks 1, 6, 15 and 32. S. aureus isolates were characterized by antibiotic susceptibility testing, spa typing, presence of mecA/C and PVL genes. Retrospective review of the clinical notes for SSTI acquisition was conducted.

RESULTS

S. aureus colonization decreased from Week 1 to Week 32 (41% to 26%, p < 0.0001). Of 1168 S. aureus isolates, three out of 1168 (0.3%) were MRSA and ten out of 1168 (0.9%) PVL-positive (all MSSA) and 169 out of 1168 (14.5%) were resistant to clindamycin. Isolates showed genetic diversity with 238 different spa types associated with 25 multi-locus sequence type (MLST) clonal complexes. SSTIs were seen in 35% (351/989) of recruits with 3 training days lost per recruit. SSTI acquisition rate was reduced amongst persistent carriers (p < 0.0283).

CONCLUSIONS

Nose and throat carriage of MRSA and PVL-SA was low among recruits, despite a high incidence of SSTIs being reported, particularly cellulitis. Carriage strains were predominantly MSSA with a marked diversity of genotypes. Persistent nose and/or throat carriage was not associated with SSTI acquisition. Putative person-to-person transmission within troops was identified based on spa typing requiring further research to confirm and explore potential transmission routes.

Subscapular Abscess Caused by Panton-Valentine Leukocidin-Positive Staphylococcus aureus: An Atypical Presentation

Subscapular abscess is an uncommon condition which requires early recognition followed by prompt surgical intervention. We present a case of spontaneous subscapular abscess following blunt trauma to the shoulder in a patient with a history of recurrent superficial soft tissue infections, in which Panton-Valentine leukocidin-producing S. aureus was identified as the infectious agent. This strain due to its virulence can lead to fatal infections in otherwise healthy individuals; therefore, a high index of suspicion is needed to investigate with an MRI to rule out abscess formation in a patient with acute shoulder girdle pain and negative joint aspirate. Urgent surgical intervention and targeted antimicrobial therapy against PVL-positive S. aureus in accordance with microbiologist yield good outcomes.

Epidemiology and microbiological characterization of clinical isolates of Staphylococcus aureus in a single healthcare region of the UK, 2015

We investigated the epidemiology and characterization of isolates of Staphylococcus aureus within the Yorkshire and Humber (YH) region in the UK. In July 2015, each laboratory within YH (n = 14) was assigned two consecutive days during which all clinical isolates of S. aureus were collected. Isolates were tested for antibiotic susceptibilities and the presence of genes encoding methicillin resistance (mecA and mecC), Panton–Valentine leukocidin (PVL) (lukS-PV), and efflux-mediated chlorhexidine resistance (qacA); isolates were also characterized by spa-types. Minimum inhibitory concentrations (MICs) to chlorhexidine were determined by the broth dilution method. Of 520 isolates collected, 6·2% were methicillin-resistant S. aureus (MRSA, all mecA-positive) and mupirocin resistance was low [0·8%, 95% confidence interval (CI) 0·3–2·0] and only found in MRSA. Carriage of the qacA gene was identified in 1·7% (95% CI 0·8–3·3) of isolates and 3·5% (95% CI 2·2–5·4) had a chlorhexidine MIC of 4 mg/l. The PVL gene was infrequent (3·7%, 95% CI 2·4–5·6). Genotyping identified 234 spa-types that mapped to 22 clonal complexes. Comparison of these current data with previous work suggest that the widespread use of staphylococcal decolonization regimens over the past decade or more has not had an adverse impact on resistance rates, PVL carriage or the prevalence of specific S. aureus lineages.

Systematic Surveillance Detects Multiple Silent Introductions and Household Transmission of Methicillin-Resistant Staphylococcus aureus USA300 in the East of England

Background. The spread of USA300 methicillin-resistant Staphylococcus aureus (MRSA) across the United States resulted in an epidemic of infections. In Europe, only sporadic cases or small clusters of USA300 infections are described, and its prevalence in England is unknown. We conducted prospective surveillance for USA300 in the east of England.

Methods. We undertook a 12-month prospective observational cohort study of all individuals with MRSA isolated from community and hospital samples submitted to a microbiology laboratory. At least 1 MRSA isolate from each individual underwent whole-genome sequencing. USA300 was identified on the basis of sequence analysis, and phylogenetic comparisons were made between these and USA300 genomes from the United States.

Results. Between April 2012 and April 2013, we sequenced 2283 MRSA isolates (detected during carriage screening and in clinical samples) from 1465 individuals. USA300 was isolated from 24 cases (1.6%). Ten cases (42%) had skin and soft tissue infection, and 2 cases had invasive disease. Phylogenetic analyses identified multiple introductions and household transmission of USA300.

Conclusions. Use of a diagnostic laboratory as a sentinel for surveillance has identified repeated introductions of USA300 in eastern England in 2012–2013, with evidence for limited transmission. Our results show how systematic surveillance could provide an early warning of strain emergence and dissemination.

High prevalence of Panton-Valentine leukocidin (PVL) genes in nosocomial-acquired Staphylococcus aureus isolated from tertiary care hospitals in Nepal

Methicillin-resistant Staphylococcus aureus (MRSA) carrying the important virulence determinant, Panton-Valentine leukocidin (PVL), is an emerging infectious pathogen associated with skin and soft tissue infections as well as life-threatening invasive diseases. In carrying out the first PVL prevalence study in Nepal, we screened 73 nosocomial isolates of S. aureus from 2 tertiary care Nepali hospitals and obtained an overall PVL-positivity rate of 35.6% among the hospital isolates: 26.1% of MRSA and 51.9% of methicillin sensitive S. aureus (MSSA) isolates were found to be positive for the PVL genes. PVL prevalence was not associated with a specific (i) infection site, (ii) age group, or (iii) hospital of origin. It was found to be positively associated with heterogeneous MRSA (73.3%) compared to homogeneous MRSA (3.2%) and MSSA (51.9%); negatively associated with multiresistant MRSA (22%) compared to nonmultiresistant MRSA (60%) and MSSA (51.9%); and positively associated with macrolide-streptogramin B resistance (93.8%) compared to macrolide-lincosamide-streptogramin B resistance (0%) and no-resistance (45.8%) types. Macrolide-streptogramin B resistance was confirmed by the presence of msr(A) gene. Restriction pattern analyses provided evidence to support the circulation of a limited number of clones of PVL-positive MRSA, arguing for the adaptability of these isolates to a hospital setting.

Skin and soft tissue infections in the military

Skin and soft tissue infections (SSTI) are common in military populations regularly living and training in close contact with each other. The majority of such infections are simple and can be easily treated with antibiotics and appropriate infection control practices. Some, however, can progress to become complex and even life threatening, such as Panton-Valentine Leukocidin (PVL)-associated staphylococcus aureus pneumonia, or Streptococcus pyogenes necrotising fasciitis, which carry a mortality rate of up to 65% and 30%, respectively. This review focuses on the most important SSTIs and those more commonly affecting military personnel with advice on how they are best managed.

Isolation of methicillin-resistant Staphylococcus aureus (MRSA) from retail meats in Hong Kong

OBJECTIVES

The presence of methicillin-resistant Staphylococcus aureus (MRSA) on meat purchased from retail outlets may allow its spread to households and represents a risk for colonization and possibly infection of consumers. Improved isolation methods have indicated that more than 10% of samples are positive. We aimed to determine rates of MRSA contamination of meat samples, including comparison of fresh and frozen samples. We characterized isolates and determined their antibiotic susceptibility.

METHODS

Samples of raw meats commonly consumed in Hong Kong were investigated for MRSA contamination using a double-enrichment isolation method. Isolates were characterized by antibiotic susceptibility testing, presence of mecA, SCCmec type, staphylococcal enterotoxins, Panton-Valentin leukocidin (PVL), and spa type. Differences in rates of MRSA contamination between meat types, rearing method, locations, sources, and fresh or frozen storage were compared.

RESULTS

MRSA was recovered from 21.9% of pork samples (78/355), 6.8% chicken (31/455), and 4.4% of beef (17/380). Isolation was considerably higher from fresh pork (47%) than frozen (0.6%), whereas contamination rates in fresh (6%) and frozen (7%) chicken were similar. All strains were multidrug resistant. All contaminated fresh pork and most frozen chicken originated from China. Most isolates belonged to CC9, being SCCmec IVb and spa type t899 or closely related spa types, but one chicken sample yielded ST398. Five strains carried spa types associated with human isolates. The egc enterotoxin group was present in the majority of isolates, but PVL in only three from chicken.

CONCLUSIONS

The predominance of t899 in isolates indicates that the primary source of contamination may be pig carcasses, previously demonstrated to frequently harbor CC9-positive MRSA in Hong Kong and China. The high rates of meat contamination suggest that improvements in food safety and personal hygiene guidelines may be advisable to reduce risk of spread of these MRSA strains in the community.

Preadmission screening of adults highlights previously unrecognized carriage of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus in London: a cause for concern?

In the first study of its kind in the United Kingdom, we describe the colonization rate of ciprofloxacin-sensitive Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus (PVL-MRSA) in adult patients who were screened systematically at the time of hospital admission. We also describe the molecular characteristics of PVL-MRSA and antibiotic resistance phenotypes. A total of 55,760 specimens were screened for MRSA between April 2008 and December 2010. MRSA was identified in 1,998 specimens, and ciprofloxacin-susceptible (CSMRSA) isolates (385/1,998, or 19.3%) were subjected to PVL testing. Of these, 70 (18.1%) were identified as PVL-CSMRSA. During the study period, the MRSA colonization rate decreased from 4.6% to 2.8%. In contrast, the colonization rate of PVL-CSMRSA increased over time, rising from 0.075% in 2008 and 0.07% in 2009 to 0.22% in 2010. The mean patient age was 52 years (range, 18 to 90 years); over two-thirds were male. Seven different lineages of PVL-CSMRSA were identified. Over the 3 years, the Southwest Pacific clone (CC30) was dominant in our population. The CC5 clone was detected once in 2008 and not at all in 2009 but accounted for a third of all PVL-CSMRSA strains in 2010. This lineage was commonly associated with clindamycin resistance and, less frequently, tetracycline resistance. We conclude that there is hitherto unrecognized low-level carriage of PVL-CSMRSA among patients being admitted to hospitals in northwest London. We observed the emergence of the CC5 clone in 2010 with associated clindamycin and tetracycline resistance.

Staphylococcus aureus isolates belonging to different multilocus sequence types present specific virulence gene profiles

To characterize 73 Staphylococcus aureus isolates from infections in an orthopedic hospital in Rio de Janeiro, we investigated the SCCmec types, the clonality by pulsed field gel electrophoresis and multilocus sequence typing, and the presence of virulence genes. Twenty-eight (38.3%) methicillin-resistant (16 SCCmec type IV and 12 type III) isolates were detected. Most (83.5%) of the isolates were included in five lineages: sequence type (ST) 239 (SCCmecIII), 1, 5, 30, and 1462 (SCCmecIV and/or methicillin-susceptible isolates). Virulence genes fnbB, bbp, and pvl were related to STs 239, 30, and 30/1462, respectively. Isolates from STs 1, 5, and 30 presented specific virulence profiles, irrespective of methicillin resistance.

Involvement of methicillin-susceptible Staphylococcus aureus related to sequence type 25 and harboring pvl genes in a case of carotid cavernous fistula after community-associated sepsis

Staphylococcus aureus encoding Panton-Valentine leukocidin (PVL) genes has become the cause of life-threatening infections. We describe a case of carotid cavernous fistula after bacteremia in a 12-year-old male, caused by a methicillin-susceptible S. aureus isolate carrying the pvl, fnbA, and ebpS genes and related to sequence type 25 (ST25). The patient's condition was complicated by pleural empyema and osteomyelitis in the right femur. The patient was discharged in good clinical condition after 160 days of hospitalization.