Genetic diversity of pvl-positive community-onset methicillin-resistant Staphylococcus aureus isolated at a university hospital in Japan

The First Report of a Methicillin-Resistant Staphylococcus aureus Isolate Harboring Type IV SCCmec in Thailand

Methicillin-resistant Staphylococcus aureus (MRSA) is mostly found in Thailand in the hospital as a nosocomial pathogen. This study aimed to report the genetic characterization of a clinical community-acquired MRSA (CA-MRSA) isolate collected from hospitalized patients in Thailand. Among 26 MRSA isolates, S. aureus no. S17 preliminarily displayed the presence of a staphylococcal cassette chromosome mec (SCCmec) type IV pattern. The bacterial genomic DNA was subjected to whole-genome sequencing. Panton-Valentine leukocidin (PVL) production, virulence toxins, and antibiotic resistance genes were identified, and multi-locus sequence typing (MLST) and spa typing were performed. The strain was matched by sequence to MLST type 2885 and spa type t13880. This strain carried type IV SCCmec with no PVL production. Five acquired antimicrobial resistance genes, namely blaZ, mecA, Inu(A), tet(K), and dfrG conferring resistance to β-lactams, lincosamides, tetracycline, and trimethoprim, were identified. The detected toxins were exfoliative toxin A, gamma-hemolysin, leukocidin D, and leukocidin E. Moreover, there were differences in seven regions in CR-MRSA no. S17 compared to CA-MRSA type 300. In summary, we have reported the ST2885-SCCmec IV CA-MRSA clinical strain in Thailand for the first time, highlighting the problem of methicillin resistance in community settings and the consideration in choosing appropriate antibiotic therapy.

Development of a vaccine against Staphylococcus aureus invasive infections: Evidence based on human immunity, genetics and bacterial evasion mechanisms

Invasive Staphylococcus aureus infections are a leading cause of morbidity and mortality in both hospital and community settings, especially with the widespread emergence of virulent and multi-drug resistant methicillin-resistant S. aureus strains. There is an urgent and unmet clinical need for non-antibiotic immune-based approaches to treat these infections as the increasing antibiotic resistance is creating a serious threat to public health. However, all vaccination attempts aimed at preventing S. aureus invasive infections have failed in human trials, especially all vaccines aimed at generating high titers of opsonic antibodies against S. aureus surface antigens to facilitate antibody-mediated bacterial clearance. In this review, we summarize the data from humans regarding the immune responses that protect against invasive S. aureus infections as well as host genetic factors and bacterial evasion mechanisms, which are important to consider for the future development of effective and successful vaccines and immunotherapies against invasive S. aureus infections in humans. The evidence presented form the basis for a hypothesis that staphylococcal toxins (including superantigens and pore-forming toxins) are important virulence factors, and targeting the neutralization of these toxins are more likely to provide a therapeutic benefit in contrast to prior vaccine attempts to generate antibodies to facilitate opsonophagocytosis.

Observational study of skin and soft-tissue Staphylococcus aureus infection in patients infected with HIV-1 and epidemics of Panton-Valentine leucocidin-positive community-acquired MRSA infection in Osaka, Japan

BACKGROUND

In patients infected with human immunodeficiency virus (HIV)-1 at our hospital, we observed increases in skin and soft-tissue infections (SSTIs) by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Therefore, we analyzed factors related to CA-MRSA infection and performed a molecular epidemiological investigation.

METHODS

HIV-1-infected patients were diagnosed with SSTIs related to S. aureus between 2007 and 2017, and MRSA was classified into community and hospital-acquired types according to published criteria. Information was collected retrospectively from clinical records, and multivariate analysis by logistic regression was performed concerning factors related to CA-MRSA infection. We evaluated the staphylococcal cassette chromosome mec (SCCmec) type, multilocus sequence type, and the presence of genes encoding Panton-Valentine leucocidin (PVL) in 27 MRSA samples isolated during and after 2015.

RESULTS

We found 218 episodes of SSTIs in 169 patients, and among initial episodes of SSTIs, the MRSA ratio was higher from 2015 to 2017 relative to that from 2007 to 2014 (88% vs. 44%; p < 0.0001). Multivariate analysis showed that in men having sex with men [MSM; odds ratio (OR): 13] and exhibiting onset during and after 2015 (OR: 5.4), CD4⁺ cell count ≥200 cells/μL (OR: 5.6) and the presence of lesions in the lower abdomen or buttocks (OR: 9.5) were independent factors related to CA-MRSA infection. Additionally, PVL+/ST8/SCCmec type IV MRSA was the predominant pathogen (22 cases; 81%).

CONCLUSIONS

These data describe an increased prevalence of SSTIs due to PVL-positive ST8-MRSA-IV, not previously considered epidemic in Japan, in MSM infected with HIV-1 in Osaka, Japan.

Current status of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus isolated from patients with skin and soft tissue infections in Japan

The USA300 clone, which produces Panton-Valentine leukocidin (PVL), is a major pathogenic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone that causes intractable skin infections. Recently, PVL-positive CA-MRSA, including USA300 clones, have emerged in both communities and hospitals in Japan. To prevent an outbreak of PVL-positive MRSA, infected patients should be treated with effective antimicrobial agents at community clinics. Herein, we investigate molecular epidemiological characteristics of PVL-positive MRSA isolated from outpatients with skin and soft tissue infections (SSTI), which are common community-onset infectious diseases. The detection rate of MRSA was 24.9% (362 strains) out of 1455 S. aureus strains isolated between 2013 and 2017. Among the MRSA strains, 15.5% (56 strains) were PVL-positive strains and associated with deep-seated skin infections. Molecular epidemiological analyses of PVL-positive MRSA showed that USA300 was the predominant clone (53.6%, 30 strains) and was identified in Kanto (18 strains), Kagawa (nine strains), Tohoku (two strains) and Hokkaido (one strain). Notably, minocycline and fusidic acid were effective against all PVL-positive MRSA strains. Hence, our data reveals the current status of PVL-positive MRSA isolated from patients with SSTI in Japan. Continuous surveillance of CA-MRSA is necessary to monitor latest prevalence rates and identify effective antimicrobial agents for PVL-positive MRSA strains.

Skin and Soft Tissue Infections Caused by Different Genotypes of PVL-Positive Community-Acquired Methicillin-Resistant Staphylococcus aureus Strains

Panton-Valentine leukocidin (PVL) is a causative agent of lethal necrotizing pneumonia and is associated with epidemic strains of community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA). PVL-producing strains have rarely been isolated in Japan. However, PVL-positive CA-MRSA has been isolated much more frequently in recent years. To investigate the relevance of pvl genes (lukS/F-PV) and clinical traits in epidemic S. aureus strains, we genotyped four PVL-positive CA-MRSA strains isolated from patients with skin and soft tissue infections and measured their susceptibility to antibiotics. Three of the isolates matched the genotype of the USA300 clone, which has predominantly been isolated in the USA. The remaining strain matched the ST217 genotype, and its spa type was identical to that of PVL-positive strains previously reported in India and China. Abscess drainage was necessary in all cases, and deep cutaneous ulcers were formed in three out of four cases regardless of the genotype. The ST217 genotype strain was resistant to clindamycin, in addition to quinolones, macrolides, and aminoglycosides. Thus, diagnostic determination of lukS/F-PV should be used as a guide for selecting the treatment regimen.

Clonal change of methicillin-resistant Staphylococcus aureus isolated from patients with impetigo in Kagawa, Japan

Recently, the USA300 clone, which is a Panton-Valentine leukocidin (PVL)-positive clonal complex 8-staphylococcal cassette chromosome mec type IV (CC8-IV) community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain, emerged in community and hospital settings in Japan. Hence, clonal types of CA-MRSA strains are predicted to be changing. Nonetheless, long-term surveillance of CA-MRSA has not been conducted in Japan. Here, we investigated the transition and current status of CA-MRSA strains isolated from outpatients with impetigo; the samples were collected between 2007 and 2016 in Kagawa, Japan. The detection rate (22.8%, 488/2139 strains) of MRSA slightly decreased in these 10 years. Molecular epidemiological analyses showed that the prevalence of the CC89-II clone, which is a typical CA-MRSA genotype of causative agents of impetigo, significantly decreased from 48.0% (48/100 strains) in 2007-2009 to 21.9% (16/73 strains) in 2013-2016. By contrast, a non-USA300 CC8-IV clone, which is a highly pathogenic CA-MRSA/J clone, significantly increased in prevalence from 9.0% (9/100 strains) to 32.9% (24/73 strains). The prevalence of PVL-positive CA-MRSA strains increased annually from 2012 (0%) to 2015 (6.7%), whereas only one of these strains turned out to be the USA300 clone. Antibiotic susceptibility data revealed that the rates of resistance to gentamicin and clindamycin among CA-MRSA strains decreased along with the decreased prevalence of the CC89-II clone and increased prevalence of the CA-MRSA/J clone. Our data strongly suggest that the clonal types and antibiotic susceptibility of CA-MRSA isolated from patients with impetigo dramatically changed during the last 10 years in Japan.

Prevalence and Characterization of Staphylococcus aureus Isolated From Women and Children in Guangzhou, China

The prevalent Staphylococcus aureus clones and antibiotic susceptibility profiles are known to change dynamically and geographically; however, recent S. aureus strains causing infections in women and children in China have not been characterized. In this study, we analyzed the molecular epidemiology and antimicrobial resistance of S. aureus isolated from patients in four centers for women and children in Guangzhou, China. In total, 131 S. aureus isolates (100 from children and 31 from women) were analyzed by spa typing, multi-locus sequence typing, virulence gene and antimicrobial resistance profiling, staphylococcal chromosomal cassette mec typing, and mutation analyses of rpoB. A total of 58 spa types, 27 sequence types (STs), and 10 clonal complexes (CCs) were identified. While CC59 (ST59-IV, 48.8%; ST338-III, 35.7%) and CC45 (ST45-IV, 100%) were the major clones (84.4%) among MRSA isolates, CC5 (ST188, 24.3%; ST1, 21.6%) and CC398 (ST398, 70%) were the major ones (70.1%) among MSSA isolates. ST338-MRSA-III mostly found in pus but hardly in respiratory tract samples while ST45-MRSA-IV was on the opposite, even though they both found in blood and cerebrospinal fluid sample frequently. Staphylococcal enterotoxin genes seb-seq-sek were strongly associated with ST59 and ST338, while sec was associated with ST45, ST121, ST22, and ST30. All ST338, ST1232, and SCCmec III isolates carried lukF/S-PV genes. A total of 80% of ST338 isolates were resistant to erythromycin, clindamycin, and tetracycline. All ST45 isolates exhibited intermediate or complete resistance to rifampicin. In total, 481 HIS/ASN mutations in rpoB were found in rifampicin-resistant or intermediate-resistant isolates. ST338-III and ST45-IV emerged as two of three major clones in MRSA isolates from women and children in Guangzhou, China, though ST59-MRSA-IV remained the most prevalent MRSA clone. Clonal distribution of S. aureus varied, depending on the specimen source. Virulence genes and antibiograms were closely associated with the clonal lineage. These results clarified the molecular epidemiology of S. aureus from women and children in Guangzhou, China, and provide critical information for the control and treatment of S. aureus infections.

Comparative analysis of methicillin-resistant Staphylococcus aureus isolated from outpatients of dermatology unit in hospitals and clinics

Community-onset methicillin-resistant Staphylococcus aureus (CO-MRSA) is a causative agent of intractable skin infections. In general, clinical symptoms of hospital outpatients with skin infections are severer than those of clinic patients. Hence, molecular epidemiological features of the CO-MRSA strains from hospital outpatients are predicted to be different from those of clinic patients. Here, we conducted a comparative analysis for CO-MRSA isolates from outpatients with impetigo in hospitals and clinics located in the same district of Tokyo, Japan. Incidence of MRSA infection was higher in hospital outpatients (21.5%, 20/93 isolates) than in clinic patients (14.5%, 121/845 isolates). The resistance rate to clindamycin, which is a common topical antimicrobial agent in dermatology, in the isolates from hospital outpatients (60.0%) was higher than those from clinic patients (31.4%). Proportion of the staphylococcal cassette chromosome (SCC) mec type II, which is a representative type of hospital-acquired MRSA in Japan, in the isolates from hospital outpatients (65.0%) was significantly higher than those from clinic patients (30.6%) (P < 0.01). Multilocus sequence typing showed that the clonal complex 89-SCCmec type II (CC89-II) clone, which exhibits clindamycin resistance, was the most predominant (55.0%) in the isolates from hospital outpatients. On the other hand, all CC8-IV, CC121-V, and CC89-V clones accounted for 60% in clinic patients were susceptible to clindamycin. Our findings suggested that the clindamycin-resistant CC89-II CO-MRSA clone might be more related to skin infections in hospital outpatients than clinic patients.

A case of acute septic arthritis of the hip joint caused by Panton-Valentine leukocidin-positive ST772 community-acquired methicillin-resistant Staphylococcus aureus

Acute septic arthritis (ASA) caused by Staphylococcus aureus can lead to fulminant arthritis and cause permanent joint destruction. In particular, infection caused by methicillin-resistant Staphylococcus aureus (MRSA) becomes intractable and severe owing to limitation of therapeutic drugs. Here, we report the case of a young patient with ASA without any record of overseas travel, who was infected by the Panton-Valentine leukocidin-positive Bengal-Bay clone, which is a predominant community-acquired MRSA in India.