The second nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan

The present study compared trends in antimicrobial resistance patterns in pathogens isolated from skin and soft-tissue infections (SSTIs) in Japan with those of a nationwide survey conducted in 2013. Three organisms that caused most of the SSTIs were collected from 12 dermatology departments in medical centers and 12 dermatology clinics across Japan between April 2019 and August 2020. A total of 390 strains, including 267 Staphylococcus aureus, 109 coagulase-negative staphylococci (CNS), and 14 Streptococcus pyogenes strains were submitted to a central laboratory for antimicrobial susceptibility testing. Patient demographic and clinical information was collated. Methicillin-resistant S. aureus (MRSA) was detected in 25.8% (69/267) of the S. aureus strains. The prevalence of MRSA between the present study and the 2013 survey did not differ significantly. Furthermore, there were no significant differences in MIC values and susceptibility patterns of the MRSA strains to other agents, regardless of a history of hospitalization within 1 year or invasive medical procedures. Methicillin-resistant CNS (MRCNS) was detected in 48.6% (53/109) of CNS isolates, higher than the 35.4% prevalence in the 2013 survey. This difference could be attributed to the heterogeneity in the members of the MRCNS, which comprises multiple staphylococci species, between the 2013 and 2019 surveys. However, it was noted that the susceptibility profiles of the MRCNS to each antibiotic were not significantly different from those identified in the 2013 survey. Most strains of S. pyogenes were susceptible to each antibiotic, similar to the 2013 survey. Continuous monitoring of trends in pathogen and susceptibility profiles is important to advise local public health efforts regarding the appropriate treatment of SSTIs.

Distribution of Leukocidins, Exfoliative Toxins, and Selected Resistance Genes Among Methicillin-resistant and Methicillin-sensitive Staphylococcus aureus Clinical Strains in Egypt

Background:

Infection with Staphylococcus aureus (S.aureus) is an increasing health problem worldwide. This pathogen has multiple virulence factors that contribute to its pathogenesis in a wide range of diseases. The present study aimed to investigate the prevalence of leukocidins, exfoliative toxins, and common antimicrobial resistance genes among Methicillin-Resistant Staphylococcus aureus (MRSA) and Methicillin-Sensitive Staphylococcus aureus (MSSA) strains collected from various clinical sources in Egypt.

Methods:

Isolates were identified as S.aureus by the standard microbiological methods. Methicillin resistance was detected phenotypically by cefoxitin disc diffusion method and genotypically by PCR for detection of mecA gene. PCR was also used to detect the presence of leukocidin genes (LukD, LukE, LukF-PV, and LukS-PV), exfoliative toxin genes (eta and etb), and antibiotic resistance genes (tetK, tetM, ermA, ermC, msrA, and aacA-aphD).

Results:

About 50.5% of tested isolates were methicillin resistant by cefoxitin disc assay, while mecA gene was amplified in 64.6% of isolates. The highest prevalent toxin gene was lukE (93%) and the least prevalent one was eta (1%). The resistance genes tetK and tetM were detected in nearly 50% of the tested strains but lower prevalence rates were recorded for aacA-aphD, msrA, ermA, and ermC genes.

Conclusion:

Methicillin resistance was highly prevalent among tested S.aureus strains. Regarding the studied virulence and resistance genes, no significant difference was detected between MRSA and MSSA strains, except for ermA gene p<0.05 which was highly prevalent in MRSA strains. So, the variation between MRSA and MSSA strains in the response to treatment may be attributed to the resistance of MRSA strains to all β-lactams in addition to other possible acquired resistance mechanisms. Accordingly, fewer options of antimicrobial medications are available to treat MRSA infections.

Prevalence of antimicrobial-resistant staphylococci in nares and affected sites of pet dogs with superficial pyoderma

Currently, antimicrobial-resistant staphylococci, particularly methicillin-resistant Staphylococcus pseudintermedius (MRSP), are frequently isolated from canine superficial pyoderma in Japan. However, little is known regarding the nasal prevalence of MRSP in pet dogs. Here, we determined the prevalence of antimicrobial-resistant staphylococci in nares and affected sites of pet dogs with superficial pyoderma. Of the 125 nares and 108 affected sites of pet dogs with superficial pyoderma, 107 (13 species) and 110 (eight species) staphylococci strains, respectively, were isolated. The isolation rate of S. pseudintermedius from pyoderma sites (82/110 strains, 74.5%) was significantly higher than that from nares (57/107 strains, 53.3%) (P<0.01). Notably, the prevalence of MRSP (18/57 strains, 31.6%) in nares was equivalent to that in pyoderma sites (28/82 strains, 34.1%). Furthermore, the phenotypes and genotypes of antimicrobial resistance in MRSP strains from nares were similar to those from pyoderma sites. Our findings revealed that the prevalence of antimicrobial-resistant staphylococci in the nares of pet dogs with superficial pyoderma is the same level as that in affected sites. Therefore, considerable attention should be paid to the antimicrobial resistance of commensal staphylococci in companion animals.

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.

Exfoliative toxin E, a new Staphylococcus aureus virulence factor with host-specific activity

Exfoliative toxins (ETs) are secreted virulence factors produced by staphylococci. These serine proteases specifically cleave desmoglein 1 (Dsg1) in mammals and are key elements in staphylococcal skin infections. We recently identified a new et gene in S. aureus O46, a strain isolated from ovine mastitis. In the present study, we characterized the new et gene at a genetic level and the enzymatic activity of the deduced protein. The S. aureus O46 genome was re-assembled, annotated and compared with other publicly available S. aureus genomes. The deduced amino acid sequence of the new et gene shared 40%, 53% and 59% sequence identity to those of ETA, ETB and ETD, respectively. The new et gene shared the same genetic vicinity and was similar in other S. aureus strains bearing this gene. The recombinant enzyme of the new et gene caused skin exfoliation in vivo in neonatal mice. The new et-gene was thus named ete, encoding a new type (type E) of exfoliative toxin. We showed that ETE degraded the extracellular segments of Dsg1 in murine, ovine and caprine epidermis, as well as in ovine teat canal epithelia, but not that in bovine epidermis. We further showed that it directly hydrolyzed human and swine Dsg1 as well as murine Dsg1α and Dsg1β, but not canine Dsg1 or murine Dsg1γ. Molecular modeling revealed a correlation between the preferred orientation of ETE docking on its Dsg1 cleavage site and species-specific cleavage activity, suggesting that the docking step preceding cleavage accounts for the ETE species-specificity. This new virulence factor may contribute to the bacterial colonization on the stratified epithelia in certain ruminants with mastitis.

An outbreak of severe infectious diseases caused by methicillin-resistant Staphylococcus aureus USA300 clone among hospitalized patients and nursing staff in a tertiary care university hospital

The USA300 clone, which produces Panton-Valentine leukocidin (PVL), is a major highly pathogenic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone that is spreading throughout the world. Although the prevalence of the USA300 clone in Japan was very limited a decade ago, its incidence has been increasing in both community and hospital settings in recent years. There is great concern that the USA300 clone will cause more complicated diseases and become a serious threat to immunocompromised patients in hospital settings. Here, we report an outbreak of severe infectious diseases in a tertiary care university hospital involving the incidence of deep infections, including bacteremia, and continuous and frequent isolation of MRSA strains for five months from six patients and a healthy nursing staff member in the same ward. The genotype of all MRSA isolates was identical to that of the USA300 clone. Furthermore, pulsed-field gel electrophoresis analysis indicated that all MRSA had the same patterns. These data demonstrate that a USA300 clone outbreak had occurred in the hospital. Fortunately, this outbreak was terminated subsequent to the interventions of the infection control team and all patients recovered following the appropriate therapies. Our report demonstrates that patients carrying highly pathogenic CA-MRSA have the potential to become a source of nosocomial outbreaks that can spread to healthy healthcare workers. Therefore, stricter standard precautions should be applied for all patients at the time of admission to prevent such nosocomial outbreaks.

Decreased Prevalence of qacA-Positive Methicillin-Resistant Staphylococcus aureus in Hospitalized Patients in Tokyo, Japan

Presence of methicillin-resistant Staphylococcus aureus (MRSA) strains carrying plasmid-borne multidrug efflux pump-encoding gene, qacA/B, is a serious issue for infection control in hospitals, because they can survive hand hygiene. The qacA/B genes are divided into five subtypes: qacA, qacBI, qacBII, qacBIII, and qacBIV. The aim of this study was to investigate the prevalence and risk factors of hospitalized patients infected by respective qacA/B-positive MRSA strains between 2010 and 2016 in Tokyo, Japan. Of the 600 total MRSA strains observed, the qacA/B-positive strains constituted 19.8% (199 isolates), of which 56.8% (113 isolates), 28.6% (57 isolates), and 14.6% (29 isolates) were classified as qacA, qacBIII, and qacBII-positive strains, respectively. The prevalence of qacA-positive MRSA strains significantly decreased from July 2010 to June 2011 (34.0%) to July 2015 to May 2016 (5.3%) (p < 0.05). When staphylococcal cassette chromosome (SCC)mec types of the respective qacA/B-positive strains were determined, 81.4% of the qacA-positive strains were classified into SCCmec type II, which has recently been decreasing in hospital-acquired MRSA in Japan. Risk factor analysis showed that there were no specific clinical departments associated with the presence of qacA-positive strains. Our findings suggest that change in the MRSA clonal lineages impact to decrease the prevalence of qacA-positive strains in Japanese hospitals.

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.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

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.

Characterization of SCCmec type IV methicillin-resistant Staphylococcus aureus clones increased in Japanese hospitals

Recently, the prevalence of staphylococcal cassette chromosome mec (SCCmec) type IV isolates, which are the major community-acquired methicillin-resistant Staphylococcus aureus (MRSA), have increased in Japanese hospitals. The aim of this study was to elucidate the detailed molecular epidemiological features of the SCCmec type IV clones in Japanese hospitals. When 2589 MRSA isolated from four hospitals in Tokyo, Japan between 2010 and 2014 were analysed, the proportion of SCCmec type IV overtook that of type II, which was the major type of hospital-acquired MRSA in 2014. Multilocus sequence typing showed that CC1 was the most predominant clone in the SCCmec type IV isolates. The clinical departments that the patients belonged to, pulsed-field gel electrophoresis analysis and antimicrobial susceptibility profiles suggested that the origin of the CC1-SCCmec type IV (CC1-IV) clone was a community setting. Our data show that the CC1-IV clone is becoming a predominant MRSA clone in Japanese hospitals.

Dissemination of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus USA300 clone in multiple hospitals in Tokyo, Japan

OBJECTIVES

Panton-Valentine leukocidin (PVL) gene (lukS/F-PV)-positive community-acquired methicillin-resistant Staphylococcus aureus (MRSA), particularly the USA300 clone, is a health concern worldwide. Recently, community-acquired MRSA clones have been found to spread and persist in hospital settings. We aimed to investigate the prevalence and molecular epidemiologic features of lukS/F-PV-positive MRSA in Japanese hospitals.

METHODS

A total of 3433 MRSA isolated from nine hospitals in 2011-2015 were assessed. Molecular epidemiologic analysis performed by staphylococcal cassette chromosome mec typing, PVL typing, arginine catabolic mobile element typing, detection of virulence determinants, multilocus sequence typing, pulsed-field gel electrophoresis and antimicrobial susceptibility testing.

RESULTS

The detection rate of lukS/F-PV was increased annually from 0.6% (5/817) in 2011 to 3.1% (17/544) in 2015. Molecular epidemiologic analysis for 64 lukS/F-PV-positive MRSA isolates revealed that 42 isolates (65.6%) were the USA300 clone. Resistance rates of levofloxacin and gentamicin among lukS/F-PV-positive isolates increased annually as a result of increased prevalence of the multidrug-resistant USA300 clone.

CONCLUSIONS

This is the first report on dissemination of the USA300 clone and PVL-positive MRSA in multiple Japanese hospitals. Our data strongly suggest that the USA300 clone may become epidemic in Japanese hospitals.

The first nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan

To investigate the trends of antimicrobial resistance in pathogens isolated from skin and soft-tissue infections (SSTI) at dermatology departments in Japan, a Japanese surveillance committee conducted the first nationwide survey in 2013. Three main organisms were collected from SSTI at 30 dermatology departments in medical centers and 10 dermatology clinics. A total of 860 strains - 579 of Staphylococcus aureus, 240 of coagulase-negative Staphylococci, and 41 of Streptococcus pyogenes - were collected and shipped to a central laboratory for antimicrobial susceptibility testing. The patient profiles were also studied. Among all 579 strains of S. aureus, 141 (24.4%) were methicillin-resistant (MRSA). Among 97 Staphylococcus epidermidis strains, 54 (55.7%) were methicillin-resistant (MRSE). MRSA and MRSE were more frequently isolated from inpatients than from outpatients. Furthermore, these methicillin-resistant strains were also isolated more frequently from patients with histories of taking antibiotics within 4 weeks and hospitalization within 1 year compared to those without. However, there were no significant differences in MIC values and susceptibility patterns of the MRSA strains between patients with a history of hospitalization within 1 year and those without. Therefore, most of the isolated MRSA cases at dermatology departments are not healthcare-acquired, but community-acquired MRSA. S. pyogenes strains were susceptible to most antibiotics except macrolides. The information in this study is not only important in terms of local public health but will also contribute to an understanding of epidemic clones of pathogens from SSTI.

Determination of the Mutant Prevention Concentration and the Mutant Selection Window of Topical Antimicrobial Agents against Propionibacterium acnes

Determination of the mutant prevention concentration (MPC) and the mutant selection window (MSW) of antimicrobial agents used to treat pathogenic bacteria is important in order to apply effective antimicrobial therapies. Here, we determined the MPCs of the major topical antimicrobial agents against Propionibacterium acnes and Staphylococcus aureus which cause skin infections and compared their MSWs. Among the MPCs of nadifloxacin and clindamycin, the clindamycin MPC was determined to be the lowest against P. acnes. In contrast, the nadifloxacin MPC was the lowest against S. aureus. Calculations based on the minimum inhibitory concentrations and MPCs showed that clindamycin has the lowest MSW against both P. acnes and S. aureus. Nadifloxacin MSWs were 4-fold higher against P. acnes than against S. aureus. It is more likely for P. acnes to acquire resistance to fluoroquinolones than S. aureus. Therefore, topical application of clindamycin contributes very little to the emergence of resistant P. acnes and S. aureus strains.

Determining the prevalence of SCCmec polymorphism, virulence and antibiotic resistance genes among methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from selected hospitals in west of Iran

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important pathogens worldwide and compared to other staphylococcal species that are associated with higher mortality rate. A total of 500 Staphylococcus spp. was collected from selected hospitals in Ilam, Kermanshah, Khorram Abad and Hamadan cities and, via phenotypic and genotypic methods, was assessed to find MRSA. The presence or absence of prevalent antibiotic resistance genes and virulence genes was evaluated among MRSA isolates, using polymerase chain reaction (PCR) method, and then the SCCmec typing of these isolates was assayed by multiplex PCR. A total of 372 (74.4%) Stapylococcus spp. isolates were identified as S. aureus, among which 200 (53.8%) possessed the mecA gene and were distinguished as MRSA. All of MRSA isolates contained blaZ gene. The frequency of ermA and ermC genes among erythromycin-resistant MRSA isolates was 21.6% and 66.7%, respectively. The frequency of the virulence genes eta, hla and sea among MRSA isolates was 10%, 80.5% and 100%, respectively. SCCmec type IV accounted for 30.6% of the MRSA isolates and SCCmec type III, SCCmec type II and SCCmec type I accounted for 30%, 22% and 17.5% of the isolates, respectively. The antibiotic resistance genes and the virulence genes of blaZ, hla, sea, eta and ermC had high frequencies among the MRSA isolates. This study showed that the antibiotic resistance genes had higher frequencies among SCCmec types I and IV, which confirms the previous reports in this field.

Anti-bacterial and anti-inflammatory effects of ethanol extract from Houttuynia cordata poultice

Houttuynia cordata (HC) has been commonly used as many traditional remedies in local areas of Japan. Although many pharmacological activities of HC have been reported, the mechanism underlying the effect of HC remains unknown. We conducted the interview survey in Japan to verify how HC was actually used. The interview survey revealed that HC poultice (HCP) prepared from smothering fresh leaves of HC was most frequently used for the treatment of purulent skin diseases including furuncle and carbuncle with high effectiveness. Ethanol extract of HCP (eHCP) showed anti-bacterial effects against methicillin-resistant Staphylococcus aureus (MRSA), and showed an anti-biofilm activity against MRSA. eHCP showed dose-dependent inhibition of S. aureus lipoteichoic acid (LTA)-induced interleukin-8 and CCL20 production in human keratinocyte without any cytotoxicity. These results suggest that HCP is effective for skin abscess and its underlying mechanism might be the complicated multiple activities for both bacteria and host cells.

Virulence Factors and Antibiotic Susceptibility of Staphylococcus aureus Isolates in Ready-to-Eat Foods: Detection of S. aureus Contamination and a High Prevalence of Virulence Genes

Staphylococcus aureus is one of the leading causes of food poisoning. Its pathogenicity results from the possession of virulence genes that produce different toxins which result in self-limiting to severe illness often requiring hospitalization. In this study of 200 sushi and sashimi samples, S. aureus contamination was confirmed in 26% of the food samples. The S. aureus isolates were further characterized for virulence genes and antibiotic susceptibility. A high incidence of virulence genes was identified in 96.2% of the isolates and 20 different virulence gene profiles were confirmed. DNA amplification showed that 30.8% (16/52) of the S. aureus carried at least one SE gene which causes staphylococcal food poisoning. The most common enterotoxin gene was seg (11.5%) and the egc cluster was detected in 5.8% of the isolates. A combination of hla and hld was the most prevalent coexistence virulence genes and accounted for 59.6% of all isolates. Antibiotic resistance studies showed tetracycline resistance to be the most common at 28.8% while multi-drug resistance was found to be low at 3.8%. In conclusion, the high rate of S. aureus in the sampled sushi and sashimi indicates the need for food safety guidelines.

Quaternary Ammonium Compounds: An Antimicrobial Mainstay and Platform for Innovation to Address Bacterial Resistance

Quaternary ammonium compounds (QACs) have represented one of the most visible and effective classes of disinfectants for nearly a century. With simple preparation, wide structural variety, and versatile incorporation into consumer products, there have been manifold developments and applications of these structures. Generally operating via disruption of one of the most fundamental structures in bacteria-the cell membrane-leading to cell lysis and bacterial death, the QACs were once thought to be impervious to resistance. Developments over the past decades, however, have shown this to be far from the truth. It is now known that a large family of bacterial genes (generally termed qac genes) encode efflux pumps capable of expelling many QAC structures from bacterial cells, leading to a decrease in susceptibility to QACs; methods of regulation of qac transcription are also understood. Importantly, qac genes can be horizontally transferred via plasmids to other bacteria and are often transmitted alongside other antibiotic-resistant genes; this dual threat represents a significant danger to human health. In this review, both QAC development and QAC resistance are documented, and possible strategies for addressing and overcoming QAC-resistant bacteria are discussed.

Increase in SCCmec type IV strains affects trends in antibiograms of meticillin-resistant Staphylococcus aureus at a tertiary-care hospital

The prevalence of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) strains has become a serious problem worldwide. The aim of this study was to investigate the annual transitions of MRSA strains with the CA-MRSA feature, which were identified as SCCmec type IV or V, in a hospital setting in Japan. Between 2005 and 2012, MRSA strains were collected from a tertiary-care hospital in Tokyo, Japan, and SCCmec typing, detection of the virulence factors and antimicrobial susceptibility testing were conducted. The rate of detection of type II SCCmec, which is found mainly in healthcare-associated MRSA, significantly decreased from 90.0 (2005-2006) to 74.3 % (2011-2012) (P < 0.01). In contrast, the rate of detection of type IV SCCmec, which is mainly found in CA-MRSA, significantly increased from 5.8 (2005-2006) to 16.3 % (2011-2012) (P < 0.01). The rate of detection of the toxic shock syndrome toxin-1 gene significantly decreased from 66.7 (2005-2006) to 51.6 % (2011-2012) (P < 0.01), whilst that of the Panton-Valentine leukocidin gene significantly increased from 0.1 (2005-2006) to 2.1 % (2011-2012) (P < 0.01). The resistance rates of cefotaxime, levofloxacin, clarithromycin and minocycline decreased every year. The resistance rates of these antimicrobial agents for the SCCmec type IV or V strains were significantly lower than those for the SCCmec type I or II strains (P < 0.01, respectively). Therefore, these results suggest that the annual transitions of the virulence factors and antibiograms in MRSA are closely related to the increase of SCCmec type IV/V strains.

Prevalence and molecular analysis of macrolide-resistant Moraxella catarrhalis clinical isolates in Japan, following emergence of the highly macrolide-resistant strain NSH1 in 2011

Although Moraxella catarrhalis is known to be susceptible to macrolides, highly macrolide-resistant M. catarrhalis isolates have recently been reported in Japan and China. In this study, we investigated the prevalence of macrolide-resistant M. catarrhalis isolates in Tokyo and Chiba, Japan, and studied the mechanisms underlying their resistance. Specifically, we determined the susceptibility of 593 clinical isolates (collected between December 2011 and May 2014) to erythromycin, using the disk diffusion method. For isolates with erythromycin resistance, we identified the MICs of seven antimicrobial agents, including macrolides, and used PFGE to analyse the clonal spread. We also performed sequencing analysis to investigate macrolide-resistance targets. Thirteen isolates (2.2 %) were found to be resistant to erythromycin, showing a high MIC90 to erythromycin, clarithromycin, clindamycin and azithromycin. However, those isolates, in addition to 156 randomly selected erythromycin-susceptible strains, were susceptible to amoxicillin-clavulanate, cefixime and levofloxacin. The 13 highly macrolide-resistant isolates were classified into 10 clades and harboured three or four A2058T-mutated 23S rRNA alleles. Three highly macrolide-resistant isolates also exhibited mutations in ribosomal proteins L4 (V27A and R161C) and L22 (K68T). To the best of our knowledge, we have demonstrated for the first time that, whilst the prevalence of macrolide-resistant M. catarrhalis isolates is low in clinical settings in Japan, genetically diverse isolates with high-level macrolide resistance due to the acquisition of an A2058T mutation in the 23S rRNA have already spread. Our study therefore lays the basis for epidemiological studies of macrolide-resistant M. catarrhalis clinical isolates.

Characterization of methicillin-resistant Staphylococcus aureus isolated from tertiary care hospitals in Tokyo, Japan

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) remains problematic in both hospital and community settings. Investigations of MRSA existing in the local area are necessary to understand the detailed epidemiology of healthcare-associated MRSA (HA-MRSA). In the present study, molecular epidemiological analysis was performed on 584 MRSA isolated from four hospitals in Tokyo, Japan. In the pulsed-field gel electrophoresis (PFGE) analysis, four epidemic pulsotypes (I to IV) were found. The isolates of the epidemic pulsotype I mainly consisted of the SCCmec type II, toxic shock syndrome toxin 1 gene (tst)-negative, spa type t002, and ST764 clones. The ST764 clone, which is a novel hybrid variant of the ST5 HA-MRSA lineage with the arginine catabolic mobile element (ACME), was first found in Niigata, Japan. However, no ACME genes were detected in the isolates of the epidemic pulsotype I. In contrast, the other isolates of the epidemic pulsotypes mainly consisted of the SCCmec type II, tst-positive, spa type t002, and ST5 clones, which are the most predominant clones of HA-MRSA in Japan. Resistance rates of non-β-lactams for the isolates of the epidemic pulsotype I were higher than those of the other epidemic pulsotypes. Our data showed that the novel ACME-negative ST764 clones are being distributed throughout multiple hospitals in Tokyo. The ST764 clones in Tokyo have the potential to acquire ACME in the future, because the ACME-positive ST764 clones have already been found in both hospital and community settings in other areas of Japan.

Staphylococcus aureus nasal carriage in Ukraine: antibacterial resistance and virulence factor encoding genes

Background

The number of studies regarding the incidence of multidrug resistant strains and distribution of genes encoding virulence factors, which have colonized the post-Soviet states, is considerably limited. The aim of the study was (1) to assess the Staphylococcus (S.) aureus nasal carriage rate, including Methicillin Resistant S. aureus (MRSA) strains in adult Ukrainian population, (2) to determine antibiotic resistant pattern and (3) the occurrence of Panton Valentine Leukocidine (PVL)-, Fibronectin-Binding Protein A (FnBPA)- and Exfoliative Toxin (ET)-encoding genes.

Methods

Nasal samples for S. aureus culture were obtained from 245 adults. The susceptibility pattern for several classes of antibiotics was determined by disk diffusion method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. The virulence factor encoding genes, mecA, lukS-lukF, eta, etb, etd, fnbA, were detected by Polymerase Chain Reaction (PCR).

Results

The S. aureus nasal carriage rate was 40%. The prevalence of nasal MRSA carriage in adults was 3.7%. LukS-lukF genes were detected in over 58% of the strains. ET-encoding genes were detected in over 39% of the strains and the most prevalent was etd. The fnbA gene was detected in over 59% of the strains. All MRSA isolates tested were positive for the mecA gene. LukS-lukF genes and the etd gene were commonly co-present in MRSA, while lukS-lukF genes and the fnbA gene were commonly co-present in Methicillin Sensitive S. aureus (MSSA) isolates. No significant difference was detected between the occurrence of lukS-lukF genes (P > 0.05) and the etd gene (P > 0.05) when comparing MRSA and MSSA. The occurrence of the fnbA gene was significantly more frequent in MSSA strains (P < 0.05).

Conclusions

In Ukraine, S. aureus is a common cause of infection. The prevalence of S. aureus nasal carriage in our cohort of patients from Ukraine was 40.4%. We found that 9.1% of the strains were classified as MRSA and all MRSA isolates tested positive for the mecA gene. We also observed a high prevalence of PVL- and ET- encoding genes among S. aureus nasal carriage strains. A systematic surveillance system can help prevent transmission and spread of drug resistant toxin producing S. aureus strains.

Relationship between the severity of acne vulgaris and antimicrobial resistance of bacteria isolated from acne lesions in a hospital in Japan

Propionibacterium acnes and Staphylococcus epidermidis are normal skin inhabitants that are frequently isolated from lesions caused by acne, and these micro-organisms are considered to contribute to the inflammation of acne. In the present study, we examined the antimicrobial susceptibilities and resistance mechanisms of P. acnes and S. epidermidis isolated from patients with acne vulgaris in a university hospital in Japan from 2009 to 2010. Additionally, we analysed the relationship between the antimicrobial resistance of P. acnes and the severity of acne vulgaris. Some P. acnes strains (18.8 %; 13/69) were resistant to clindamycin. All strains had a mutation in the 23S rRNA gene, except for one strain that expressed erm(X) encoding a 23S rRNA methylase. Tetracycline-resistant P. acnes strains were found to represent 4.3 % (3/69) of the strains, and this resistance was caused by a mutation in the 16S rRNA gene. Furthermore, three strains with reduced susceptibility to nadifloxacin (MIC = 16 µg ml(-1)) were detected. When analysing the correlation between the antimicrobial resistance of P. acnes and S. epidermidis, more than 80 % of the patients who carried clindamycin-resistant P. acnes also carried clindamycin-resistant S. epidermidis. However, no epidemic strain that exhibited antimicrobial resistance was detected in the P. acnes strains when analysed by PFGE. Therefore, our results suggest that the antimicrobial resistance of P. acnes is closely related to antimicrobial therapy. Additionally, those P. acnes strains tended to be frequently found in severe acne patients rather than in mild acne patients. Consequently, the data support a relationship between using antimicrobial agents and the emergence of antimicrobial resistance.

Antimicrobial susceptibility and mechanisms of high-level macrolide resistance in clinical isolates of Moraxella nonliquefaciens

We investigated antimicrobial susceptibility and the molecular mechanism involved in conferring high-level macrolide resistance in 47 clinical isolates of Moraxella nonliquefaciens from Japan. Antimicrobial susceptibility was determined using Etest and agar dilution methods. Thirty-two erythromycin-non-susceptible strains were evaluated for the possibility of clonal spreading, using PFGE. To analyse the mechanism related to macrolide resistance, mutations in the 23S rRNA gene and the ribosomal proteins, and the presence of methylase genes were investigated by PCR and sequencing. The efflux system was examined using appropriate inhibitors. Penicillin, ampicillin, amoxicillin, cefixime, levofloxacin and antimicrobials containing β-lactamase inhibitors showed strong activity against 47 M. nonliquefaciens isolates. Thirty-two (68.1 %) of the 47 isolates showed high-level MICs to macrolides (MIC ≥128 mg l(-1)) and shared the A2058T mutation in the 23S rRNA gene. The geometric mean MIC to macrolides of A2058T-mutated strains was significantly higher than that of WT strains (P<0.0001). Thirty-two isolates with high-level macrolide MICs clustered into 30 patterns on the basis of the PFGE dendrogram, indicating that the macrolide-resistant strains were not clonal. In contrast, no common mutations of the ribosomal proteins or methylase genes, or overproduction of the efflux system were observed in A2058T-mutated strains. Moreover, of the 47 M. nonliquefaciens strains, 43 (91.5 %) were bro-1 and 4 (8.5 %) were bro-2 positive. Our results suggest that most M. nonliquefaciens clinical isolates show high-level macrolide resistance conferred by the A2058T mutation in the 23S rRNA gene. This study represents the first characterization of M. nonliquefaciens.

Emergence of Staphylococcus aureus carrying multiple drug resistance genes on a plasmid encoding exfoliative toxin B

We report the complete nucleotide sequence and analysis of pETBTY825, a Staphylococcus aureus TY825 plasmid encoding exfoliative toxin B (ETB). S. aureus TY825 is a clinical isolate obtained from an impetigo patient in 2002. The size of pETBTY825, 60.6 kbp, was unexpectedly larger than that of the archetype pETBTY4 (∼30 kbp). Genomic comparison of the plasmids shows that pETBTY825 has the archetype pETBTY4 as the backbone and has a single large extra DNA region of 22.4 kbp. The extra DNA region contains genes for resistance to aminoglycoside [aac(6')/aph(2″)], macrolide (msrA), and penicillin (blaZ). A plasmid deletion experiment indicated that these three resistance elements were functionally active. We retrospectively examined the resistance profile of the clinical ETB-producing S. aureus strains isolated in 1977 to 2007 using a MIC determination with gentamicin (GM), arbekacin (ABK), and erythromycin (EM) and by PCR analyses for aac(6')/aph(2″) and msrA using purified plasmid preparations. The ETB-producing S. aureus strains began to display high resistance to GM, which was parallel with the detection of aac(6')/aph(2″) and mecA, after 1990. Conversely, there was no significant change in the ABK MIC during the testing period, although it had a tendency to slightly increase. After 2001, isolates resistant to EM significantly increased; however, msrA was hardly detected in ETB-producing S. aureus strains, and only five isolates were positive for both aac(6')/aph(2″) and msrA. In this study, we report the emergence of a fusion plasmid carrying the toxin gene etb and drug resistance genes. Prevalence of the pETBTY825 carrier may further increase the clinical threat, since ETB-producing S. aureus is closely related to more severe impetigo or staphylococcal scalded-skin syndrome (SSSS), which requires a general antimicrobial treatment.

Molecular epidemiology of community-associated meticillin-resistant Staphylococcus aureus in Asia

In Asia, most reports on the epidemiology of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) are from developed countries, with few data from resource-limited countries, not because of low actual prevalence, but probably because of scarce diagnostic facilities. The rate of MRSA in all community-associated S. aureus infections in Asian countries ranges from 2·5% to 39%. Unlike the predominance of USA300-sequence type (ST) 8 staphylococcal cassette chromosome mec (SCCmec) type IV in the USA, the molecular epidemiology of CA-MRSA in Asia is characterised by clonal heterogeneity, similar to that in Europe. The emergence of CA-MRSA is a threat in both community and hospital settings because such strains are now more prevalent than are health-care-associated MRSA (HA-MRSA) strains. Many epidemic clones are in circulation in Asia and with scarce data available, concern has arisen that CA-MRSA could have devastating results if it becomes epidemic in resource-poor regions. The epidemiology of CA-MRSA in Asia is closely linked with the health of both developing and developed countries. The present situation of CA-MRSA in Asia is important not only for local public health, but also to provide a better understanding of the successful epidemic clones of this global pathogen.

Identification of methicillin-resistant Staphylococcus aureus carrying an exfoliative toxin A gene encoding phage isolated from a hospitalized patient in Turkey

From the four known isoforms of the staphylococcal exfoliative toxins (ETs), only ETA and ETB are the major causative agents. General knowledge is that the gene for ETA is located on the chromosome, whereas that for ETB is located on a large plasmid. Yoshizawa and co-workers (2000, Microbiol. Immunol. 44(3): 189–191) isolated, for the first time, a temperate phage (φETA) that carried the structural gene for ETA from an ETA-producing strain of Staphylococcus aureus. In this study, we presented eta gene encoding temperate phages isolated from methicillin-resistant S.aureus (MRSA) isolates obtained from patients in a Turkish hospital. Molecular analysis of the phage genome revealed that the eta gene is located upstream to amidase and holin genes, the same as in the φETA genome. However, partial sequence analysis of amidase and holin genes revealed polymorphic variation. In addition to polymorphic variation, restriction fragment length polymorphism (RFLP) analysis of all of the phage genomes showed that the ETA-containing phage is different from the rest of the phage genomes. The phylogenetic dendrogram of pulsed field gel electrophoresis (PFGE) analysis showed that the ETA-carrying MRSA is quite different from the rest of the MRSA strains. This is the first report showing that a MRSA strain carries an ETA-encoding phage.

Epidemiological data of staphylococcal scalded skin syndrome in France from 1997 to 2007 and microbiological characteristics of Staphylococcus aureus associated strains

Epidemiological data on staphylococcal scalded skin syndromes (SSSS), including bullous impetigo (BI) and generalized exfoliative syndrome (GES), are scarce. To better characterize SSSS and associated Staphylococcus aureus strains, we conducted a retrospective study of 349 cases collected in France between 1997 and 2007 by the National Reference Centre of Staphylococci. Our results showed a stationary evolution of SSSS cases, with a heterogeneous distribution of cases in France. Although notification was not exhaustive, we estimated an incidence of 0.56 cases/year/million inhabitants, in accordance with previous studies conducted in France and Europe, with a median age of 2 years old and sex ratios of 1. A seasonal effect was observed, with a higher GES/BI ratio in autumn compared with other seasons, which could be explained by the impact of viral co-infection. Genetic analysis of S. aureus strains showed that accessory gene regulator (agr) 4, exfoliative toxin A (eta) and B (etb) genes, staphylococcal and enterotoxin-like O (selo) gene and agr4 etb selo profiles were predominantly associated with GES, whereas agr2 eta and agr4 eta selo were more frequently observed with BI. Only one methicillin-resistant strain was found. Protein A (spa) typing identified two main genotypes: spa clonal complex (CC) 159/sequence-type (ST) 121 (75%) and spaCC346/ST15 (18%). spaCC159 was mainly associated with agr4 eta etb selo, agr4 eta selo and agr4 etb selo, and spaCC346 was mainly associated with agr2 eta, suggesting that French SSSS cases are caused by these two main lineages. However, in a multivariate analysis, only etb was independently associated with GES.

Characterization of enterococcus strains contained in probiotic products

Probiotics are additives containing live microbes that beneficially affect a host by improving the properties of the host intestinal microflora. Recently, advances in medical treatments have led to increased numbers of immunocompromised patients; some patients contract opportunistic infections of Enterococcus species, which are considered non-pathogenic bacteria. To evaluate the safety of probiotics containing Enterococcus strains, we isolated Enterococcus from six probiotic products and compared the pathogenic genes and antimicrobial susceptibility of the probiotic strains to those of clinical isolates. Our study showed that all Enterococcus strains contained in probiotic products were E. faecium, and no vancomycin-resistant strains were found. In addition, no pathogenic genes, such as ace, agg, gelE, cylM, cylB, cylA, cpd, cob, ccf, efaA(fs), efaA(fm), esp(fs), or esp(fm), were found in the probiotic strains. Pulsed-field gel electrophoresis (PFGE) analysis showed obvious genetic differences between the probiotic strains and the clinical isolates. The data suggested that the probiotic Enterococcus strains were not transmitted to hospitalized patients. Therefore, our results strongly suggest that probiotic products are unlikely agents for causing opportunistic infections.

Genotypes and toxin gene profiles of Staphylococcus aureus clinical isolates from China

A total of 108 S. aureus isolates from 16 major hospitals located in 14 different provinces in China were characterized for the profiles of 18 staphylococcal enterotoxin (SE) genes, 3 exfoliatin genes (eta, etb and etd), and the toxic shock syndrome toxin gene (tsst) by PCR. The genomic diversity of each isolate was also evaluated by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and accessory gene regulator (agr) typing. Of these strains, 90.7% (98/108) harbored toxin genes, in which tsst was the most prevalent toxin gene (48.1%), followed by sea (44.4%), sek (42.6%) and seq (40.7%). The see and etb genes were not found in any of the isolates tested. Because of high-frequency transfer of toxin gene-containing mobile genetic elements between S. aureus strains, a total of 47 different toxin gene combinations were detected, including a complete egc cluster in 19 isolates, co-occurrence of sea, sek and seq in 38 strains, and sec and sel together in 11 strains. Genetic typing by PFGE grouped all the strains into 25 clusters based on 80% similarity. MLST revealed 25 sequence types (ST) which were assigned into 16 clonal complexes (CCs) including 2 new singletons. Among these, 11 new and 6 known STs were first reported in the S. aureus strains from China. Overall, the genotyping results showed high genetic diversity of the strains regardless of their geographical distributions, and no strong correlation between genetic background and toxin genotypes of the strains. For genotyping S. aureus, PFGE appears to be more discriminatory than MLST. However, toxin gene typing combined with PFGE or MLST could increase the discriminatory power of genotyping S. aureus strains.

Predominant Dissemination of PVL-Negative CC89 MRSA with SCCmec Type II in Children with Impetigo in Japan

Background. The ratio of CA-MRSA in children with impetigo has been increasing in Japan. Methods. Antimicrobial susceptibilities of 136 S. aureus isolates from children with impetigo were studied. Furthermore, molecular epidemiological analysis and virulence gene analysis were performed. Results. Of the 136 S. aureus isolates, 122 (89.7%) were MSSA and 14 (10.3%) were MRSA. Of the 14 MRSA strains, 11 belonged to CC89 (ST89, ST91, and ST2117) and carried diverse types of SCCmec: type II (IIb: 3 strains; unknown subtype: 4 strains), type IVa (2 strains), and unknown type (2 strains). The remaining three strains exhibited CC8 (ST-8)-SCCmec type VIa, CC121 (ST121)-SCCmec type V, and CC5 (ST5)-nontypeable SCCmec element, respectively. None were lukS-PV-lukF-PV gene positive. Gentamicin- and clarithromycin-resistant strains were frequently found in both MRSA and MSSA. Conclusions. PVL-negative CC89-SCCmec type II strains are the most predominant strains among the CA-MRSA strains circulating in the community in Japan.

Determination of staphylococcal exotoxins, SCCmec types, and genetic relatedness of Staphylococcus intermedius group isolates from veterinary staff, companion animals, and hospital environments in Korea

The Staphylococcus (S.) intermedius group (SIG) has been a main research subject in recent years. S. pseudintermedius causes pyoderma and otitis in companion animals as well as foodborne diseases. To prevent SIG-associated infection and disease outbreaks, identification of both staphylococcal exotoxins and staphylococcal cassette chromosome mec (SCCmec) types among SIG isolates may be helpful. In this study, it was found that a single isolate (one out of 178 SIG isolates examined) harbored the canine enterotoxin SEC gene. However, the S. intermedius exfoliative toxin gene was found in 166 SIG isolates although the S. aureus-derived exfoliative toxin genes, such as eta, etb and etd, were not detected. SCCmec typing resulted in classifying one isolate as SCCmec type IV, 41 isolates as type V (including three S. intermedius isolates), and 10 isolates as non-classifiable. Genetic relatedness of all S. pseudintermedius isolates recovered from veterinary staff, companion animals, and hospital environments was determined by pulsed-field gel electrophoresis. Strains having the same band patterns were detected in S. pseudintermedius isolates collected at 13 and 18 months, suggesting possible colonization and/or expansion of a specific S. pseudintermedius strain in a veterinary hospital.

Dissemination of multiple MRSA clones among community-associated methicillin-resistant Staphylococcus aureus infections from Japanese children with impetigo

The proportion of MRSA strains that cause skin and soft infections has recently increased. In 3 months we have characterized 17 MRSA strains isolated from children with impetigo at a Japanese hospital. Seventeen MRSA strains belonged to 7 clones defined by clonal complex (CC) in MLST genotype and type of SCCmec, which were rarely identified among healthcare-associated MRSA: CC 91-SCCmecIIb (4 strains); CC91-SCCmecIIn (2 strains); CC91-SCCmecIVa (2 strains); CC91-SCCmecV (4 strains); CC88-SCCmecIVg (3 strains); CC1-SCCmecIVc (1 strain); and CC5-SCCmecIVn (1 strain). Although one strain belonged to CC5, which has been commonly identified in healthcare-associated MRSA, it did not carry type II SCCmec, but carried type IV SCCmec. Fourteen of the 17 strains carried exfoliative toxin a or b gene, and none carried Panton-Valentine leukocidine gene. Furthermore, we determined the entire nucleotide sequences of two type V SCCmec elements carried by strains JCSC5952, a CC91 strain, and TSGH17, a Taiwanese CC59 strain. The structure of SCCmecJCSC5952 was more than 99% homologous in nucleotide identity with those of Taiwanese PVL-positive ST59 MRSA strains TSGH17 and PM1, which were designated as type V (5C2&5). Identification of multiple MRSA clones distinct from those disseminating at the hospital suggests that MRSA strains might be emerging in the community from MSSA strains by acquiring SCCmec elements on various occasions. Carriage of the similar type V(5C2&5) SCCmec element by strains of distinct genetic backgrounds, CC91 and CC59, suggested horizontal transfer of the SCCmec element.

Community-acquired methicillin-resistant Staphylococcus aureus: community transmission, pathogenesis, and drug resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is able to persist not only in hospitals (with a high level of antimicrobial agent use) but also in the community (with a low level of antimicrobial agent use). The former is called hospital-acquired MRSA (HA-MRSA) and the latter community-acquired MRSA (CA-MRSA). It is believed MRSA clones are generated from S. aureus through insertion of the staphylococcal cassette chromosome mec (SCCmec), and outbreaks occur as they spread. Several worldwide and regional clones have been identified, and their epidemiological, clinical, and genetic characteristics have been described. CA-MRSA is likely able to survive in the community because of suitable SCCmec types (type IV or V), a clone-specific colonization/infection nature, toxin profiles (including Pantone-Valentine leucocidin, PVL), and narrow drug resistance patterns. CA-MRSA infections are generally seen in healthy children or young athletes, with unexpected cases of diseases, and also in elderly inpatients, occasionally surprising clinicians used to HA-MRSA infections. CA-MRSA spreads within families and close-contact groups or even through public transport, demonstrating transmission cores. Re-infection (including multifocal infection) frequently occurs, if the cores are not sought out and properly eradicated. Recently, attention has been given to CA-MRSA (USA300), which originated in the US, and is growing as HA-MRSA and also as a worldwide clone. CA-MRSA infection in influenza season has increasingly been noted as well. MRSA is also found in farm and companion animals, and has occasionally transferred to humans. As such, the epidemiological, clinical, and genetic behavior of CA-MRSA, a growing threat, is focused on in this study.

Identification of first exfoliative toxin in Staphylococcus pseudintermedius

Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus chromogenes are known to cause skin infections in human or animals by producing exfoliative toxins (ETs). Staphylococcus pseudintermedius can also cause canine pyoderma, but no exfoliative toxins or similar toxins have been reported. PCR with degenerate primers targeted to the conserved regions in ETA, ETB, and ETD from S. aureus and SHETB from S. hyicus, and subsequent chromosome walking identified a novel gene, designated as exi (exfoliative toxin of pseudintermedius) in S. pseudintermedius. EXI had significant homologies with the exfoliative toxins (43-68% identity), particularly with ETB (67.1%), ETD (67.9%), and SHETB (65.1%). Phylogenetic analysis showed close relation between EXI and ETB with a bootstrap value of 80%. Neonatal mice injected with the crude proteins from the culture supernatant or recombinant EXI showed gross blisters and/or characteristic skin exfoliation. The prevalence of exi assessed by dot-blot hybridization was 23.3% (10/43) in S. pseudintermedius isolates from canine pyoderma. The EXI reported herein is the first exfoliative toxin identified in S. pseudintermedius.