Community-acquired Methicillin-resistant Staphylococcus Aureus Strains Research Articles

Staphylococcal scalded skin syndrome in neonate: Another face of CA-MRSA.

Staphylococcal scalded skin syndrome (SSSS), also known as Ritter's disease, in its severe form occurs predominantly in infants and children. It is caused by infection with group II (often phage group 71) Staphylococcus aureus. The foci of infection include nasopharynx, less commonly umbilicus, urinary tract, superficial abrasion, conjunctivae, and blood. Staphylococci are non-motile, non-spore-forming, catalase-positive, gram-positive cocci that appear predominantly as grape-like clusters. Although this organism is frequently a part of normal human microbial flora, it can cause significant opportunistic infections under certain conditions such as when extremes of age groups are involved, the presence of indwelling medical devices, and intravenous (iv) drug abuse. Staphylococcus aureus may cause a variety of infectious manifestations ranging from relatively benign skin infections to life-threatening systemic illnesses. SSSS caused by S. aureus strains produces exfoliative toxins which result in the development of blisters, erythema, and desquamation. Here, we present a case of an 11-day-old neonate who was diagnosed with SSSS. The causative agent responsible for this syndrome was identified as methicillin-resistant Staphylococcus aureus (MRSA). The molecular characterization of the gene Panton-Valentine leukocidin (PVL) was done by polymerase chain reaction (PCR) and was detected positive for PVL which is a distinctive virulence factor seen almost in all of the community-acquired MRSA strains. The patient was discharged after parenteral clindamycin therapy with almost complete resolution of symptoms.

2177. Characterization of community-acquired methicillin-resistant Staphylococcus aureus isolated from patients with skin and soft tissue infections in selected health facilities, in Kenya

Abstract Background Colonization of the skin, mucus membrane, and nose of humans by Staphylococcus aureus (S. aureus) is more common than infection. The lack of proper microbiological surveillance systems in Africa may underestimate the burden of Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), while little is known about its incidence. In Kenya, there is a paucity of data on prevalence and circulating CA-MRSA strains. Methods Cross-sectional study design was employed with a sample size of 228 wound swabs from community-acquired skin and soft tissue infections, collected from 5 AMR surveillance sites in Kenya. S. aureus isolation, identification, and antimicrobial susceptibility tests were carried out according to standard bacteriology methods. Molecular characterization for MRSA isolates was performed by whole genome sequencing. Results Descriptive and inferential statistics were computed using the R program. Total S. aureus isolated was 29.38 % while MRSA isolation varied within study sites, with a CA-MRSA prevalence of 1.8 %. Phenotypic resistance observed did not match genotypic resistance for some isolates. Resistance mostly reported in nosocomial infections and resistance to reserved antibiotics was observed, which raises concern. Mutations within resistance genes, Inducible-Macrolide-Lincosamide-Streptogramin b resistance (MLSBi), 23S ribosome resistance and also erythromycin resistance by efflux pump was observed. Staphylococcal chromosomal cassette mec (SCCmec) type IV was the most prevalent while the sequence types (STs) obtained were ST 30, 8 and the novel STs 7460 and 7635. Only one isolate had intact mecA and its regulatory genes, but still conferred methicillin resistance. IS 1272 was detected in mecA regulatory genes. Conclusion The resistance patterns observed in this study further highlight the burden of antimicrobial resistance in community isolates of S. aureus. There is need for more research on CA-MRSA within Antimicrobial resistance (AMR) surveillance in Kenya in order to better understand the molecular epidemiology as well as the drivers of resistance Disclosures All Authors: No reported disclosures

Discovery of the novel auxiliary factor for β-lactam resistance BlrA in community-acquired methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important human pathogens that cause a variety of infections in community and hospital settings. This organism displays high levels of resistance to β-lactam antibiotics and this principally occurs due to the production of β-lactamase and the penicillin binding protein PBP2a encoded by mecA gene. Furthermore, additional mechanisms, such as auxiliary factors, significantly contribute to β-lactam resistance. However, the function of most of these factors is still unknown.
 Recently, in our laboratory, the novel auxiliary factor gene blrA was initially identified by transposon mutagenesis in the community-acquired MRSA strain JE2. Next, the transposon mutation was transduced to the community-acquired MRSA strain MW2, resulting in the formation of a transposon mutant for blrA (blrA::ermB), denoted as MW2A. Initially, our results suggested that MW2A is more susceptible to oxacillin than the MW2 wild-type. Then, we performed the Minimum Inhibitory Concentration (MIC) method for the β-lactam antibiotics: oxacillin, cefoxitin, cephradine, ceftazidime, cefaclor and imipenem. MW2A exhibited a two-fold reduction for all tested β-lactam antibiotics compared to the MRSA wild-type strain MW2. Additionally, no phenotypical changes were observed after performing PBP2a latex agglutination test and phage spot assay. Finally, using DeepTMHMM we show that BlrA is likely to act intracellularly, which is typical of auxiliary factors.
 In this study, we show that BlrA is clearly involved in β-lactam resistance, but does not affect the expression of the gene mecA or the structure of the wall teichoic acids. Furthermore, we propose that that BlrA acts as an auxiliary factor and is activated in response to antimicrobial stress.

Molecular Epidemiology of Community-Acquired Methicillin-Resistant Staphylococcus aureus and Clinical Characteristics of Different Sites of Infection.

Since community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized, the molecular epidemiology of CA-MRSA in China has been diverse. It is unclear whether different sites of CA-MRSA infection differ in antimicrobial resistance and clinical characteristics. The purpose of this study was to identify the molecular types, virulence factors and antimicrobial resistance of CA-MRSA strains and to analyze the clinical characteristics of different sites of CA-MRSA infection. 26 CA-MRSA strains were screened from Beijing Chao-Yang Hospital from 2014 to 2022. SCCmec type, MLST type, spa type, Panton-Valentine leukocidin (PVL), hemolysin α (Hla), phenolic soluble regulatory protein α (PSMα), toxic shock syndrome toxin-1 (TSST-1), and enterotoxin (SE) A to E were detected by PCR and gene sequencing. Antimicrobial susceptibility tests and the clinical features of CA-MRSA infection cases were collected for statistical analysis. The predominant type of CA-MRSA was ST59-t437-IV. New non-epidemic types, SCCmec VII, were also found. PVL was seen in 65.4% of CA-MRSA strains and TSST-1 was only be detected in 3.8% of CA-MRSA strain which caused poor prognosis. There were three types of infections: pneumonia (61.5%), infective endocarditis (7.7%), and skin and soft tissue infections (SSTIs) (30.8%). CA-MRSA pneumonia cases were secondary to influenza infection (37.5%). Patients with CA-MRSA-associated infective endocarditis were more likely to have underlying cardiac diseases. Patients with CA-MRSA-associated SSTIs were more likely to have a history of diabetes mellitus, and strains in this group were more susceptible to erythromycin and clindamycin. ST59-t437-IV was the primary CA-MRSA type in our research and in China. We proposed that TSST-1 might be one of the indicators to predict the severity and prognosis of CA-MRSA infection. Different sites of CA-MRSA infection had difference in antibiotics susceptibility testing and underlying diseases of patients. It could provide a new perspective on treating different types of CA-MRSA infection.

Characterization of PVL-Positive MRSA Isolates in Northern Bavaria, Germany over an Eight-Year Period.

Community-acquired methicillin-resistant Staphylococcus aureus strains (CA-MRSA) are spread worldwide and often cause recurring and persistent infections in humans. CA-MRSA strains frequently carry Panton-Valentine leukocidin (PVL) as a distinctive virulence factor. This study investigates the molecular epidemiology, antibiotic resistance and clinical characteristics of PVL-positive MRSA strains in Northern Bavaria, Germany, isolated over an eight-year period. Strains were identified by MALDI-TOF MS and antibiotic susceptibility was tested by automated microdilution (VITEK 2) or disk diffusion. PVL-encoding genes and mecA were detected by PCR. MRSA clonal complexes (CC) and lineages were assigned by genotyping via DNA microarray and spa-typing. In total, 131 PVL-positive MRSA were collected from five hospital sites between 2009 and 2016. Predominant lineages were CC8-MRSA-[IV+ACME], USA300 (27/131; 20.6%); CC30-MRSA-IV, Southwest Pacific Clone (26/131; 19.8%) and CC80-MRSA-IV (25/131; 19.1%). Other CCs were detected less frequently. Resistance against erythromycin and clindamycin was prevalent, whereas all strains were sensitive towards vancomycin and linezolid. In total, 100 cases (76.3%) were causally linked to an infection. The majority (102/131; 77.9%) of isolates were detected in skin swabs or swabs from surgical sites. During the sample period we found an increase in the PVL-positive MRSA lineages CC30 and CC1. Compared to less-abundant lineages CC1 or CC22, the predominant lineages CC8, CC30 and CC80 harbored a broader resistance spectrum. Furthermore, these lineages are probably associated with a travel and migration background. In the spatio-temporal setting we investigated, these were arguably drivers of diversification and change in the landscape of PVL-positive MRSA.

Identification of Staphylococcus aureus Penicillin Binding Protein 4 (PBP4) Inhibitors.

Methicillin-resistant Staphylococcus aureus (MRSA) is a global healthcare concern. Such resistance has historically been attributed to the acquisition of mecA (or mecC), which encodes an alternative penicillin binding protein, PBP2a, with low β-lactam affinity. However, recent studies have indicated that penicillin binding protein 4 (PBP4) is also a critical determinant of S. aureus methicillin resistance, particularly among community-acquired MRSA strains. Thus, PBP4 has been considered an intriguing therapeutic target as corresponding inhibitors may restore MRSA β-lactam susceptibility. In addition to its role in antibiotic resistance, PBP4 has also recently been shown to be required for S. aureus cortical bone osteocyte lacuno-canalicular network (OLCN) invasion and colonization, providing the organism with a niche for re-occurring bone infection. From these perspectives, the development of PBP4 inhibitors may have tremendous impact as agents that both reverse methicillin resistance and inhibit the organism’s ability to cause chronic osteomyelitis. Accordingly, using a whole-cell high-throughput screen of a 30,000-member small molecule chemical library and secondary assays we identified putative S. aureus PBP4 inhibitors. Quantitative reverse transcriptase mediated PCR and PBP4 binding assays revealed that hits could be further distinguished as compounds that reduce PBP4 expression versus compounds that are likely to affect the protein’s function. We also showed that 6.25 µM (2.5 µg/mL) of the lead candidate, 9314848, reverses the organism’s PBP4-dependent MRSA phenotype and inhibits its ability to traverse Microfluidic-Silicon Membrane-Canalicular Arrays (µSiM-CA) that model the OLCN orifice. Collectively, these molecules may represent promising potential as PBP4-inhibitors that can be further developed as adjuvants for the treatment of MRSA infections and/or osteomyelitis prophylactics.

Prevalence of Staphylococcus aureus and mec-A Cassette in the Throat of Non-Hospitalized Individuals Randomly Selected in Central Italy.

Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of life-threatening infections that are difficult to treat because of resistance to several antibiotics. Most documented MRSA infections are acquired nosocomially or among community with frequent contact with health facilities. However, an increasing attention to community acquired MRSA strains appears justified. A population of Central Italy was investigated for the presence of S. aureus and for the methicillin-resistance determinant mec-A gene. Exclusion was due to systemic diseases, pathologies or therapies inducing systemic immunosuppression, facial trauma or poor oral hygiene. Throat swabs obtained from 861 randomly selected participants were tested for the presence of DNA sequences of S. aureus and the mec-A gene by real-time PCR. The DNA of S. aureus was detected in 199 specimens (23.1%), while the mec-A gene was detected in 27 samples (3.1%). The prevalence of patients carrying methicillin-resistant strains was higher in younger and older strata. The prevalence of mec-A among S. aureus positive samples was 7.5%. Our data confirm that S. aureus and methicillin-resistant strains are common in the throat of the general population of Central Italy. Although the PCR methods used in this study are different from traditional culture-based approaches, the observed prevalence was consistent to those observed in Italians and other populations. Considering that carriers have a higher risk to develop post surgically life-threatening infections, it is worth evaluating a preventive approach based on rapid PCR screening of incoming patients to reduce the risk of developing health-care-associated infections.

The Correlation Between Biofilm-Forming Ability of Community-Acquired Methicillin-Resistant Staphylococcus aureus Isolated from the Respiratory Tract and Clinical Characteristics in Children.

ObjectiveThis study aimed to investigate the biofilm-forming ability, molecular typing, and antimicrobial resistance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains isolated from the respiratory tract of children and their correlation with clinical characteristics.MethodsAll CA-MRSA strains were isolated from hospitalized children, and their presentation, molecular typing, antimicrobial susceptibility, and biofilm formation were investigated. The clinical characteristics were compared between the strong and weak biofilm producer groups.ResultsFifty-three CA-MRSA strains were isolated from the respiratory samples of 53 children, with nearly half of them being young infants (0–12 months). Approximately, 88.7% (47/53) of the isolates were resistant to four or more antibiotics, mainly β-lactam antibiotics, lincosamides, and macrolides. Twelve sequence types (STs) and 20 subtypes of staphylococcal protein A (spa) typing were identified, with ST59-t437 (39.6%, 21/53) as the predominant subtype. All strains showed the ability to form biofilms. When compared to children with weak biofilm-forming CA-MRSA strains, those with strong biofilm-forming strains had higher proportions of lower respiratory tract infections (LRTI) (88.5% vs 59.3%), obvious cough symptoms (84.6% vs 51.9%), and severe chest imaging manifestations (76.9% vs 37.0%). Furthermore, a strong biofilm-forming ability significantly increased the risk of prolonged cough in children with LRTI (44.4% vs 14.3%), and a positive correlation between the duration of cough and the extent of biofilm formation was observed. Medical history investigation revealed that the strong biofilm-forming group had a much higher percentage of macrolides intake than the weak biofilm-forming group in the last month before admission (61.5% vs 14.8%).ConclusionST59-t437 was the most prevalent clone in CA-MRSA respiratory isolates among the hospitalized children. All CA-MRSA strains formed biofilms. The stronger the biofilm-forming ability, the more serious and prolonged were the respiratory symptoms.

Epidemiological and clinical features of Panton-Valentine Leukocidin positive Staphylococcus aureus bacteremia: A case-control study.

Panton-Valentine Leukocidin (PVL) toxin in Staphylococcus aureus has been associated with both severe pneumonia and skin and soft tissue infections. However, there are only limited data on how this virulence factor may influence the clinical course or complications of bacteremic S. aureus infections. Between September 2016 and March 2018, S. aureus isolates from clinical cultures from hospitals in an academic medical center underwent comprehensive genomic sequencing. Four hundred sixty-nine (29%) of 1681 S. aureus sequenced isolates were identified as containing the genes that encode for PVL. Case patients with one or more positive blood cultures for PVL were randomly matched with control patients having positive blood cultures with lukF/lukS-PV negative (PVL strains from a retrospective chart review). 51 case and 56 control patients were analyzed. Case patients were more likely to have a history of injection drug use, while controls more likely to undergo hemodialysis. Isolates from 78.4% of case patients were methicillin resistant as compared to 28.6% from control patients. Case patients had a higher incidence of pneumonia and skin and soft tissue infection and longer duration of fever without differences in length of bacteremia. Clinical cure or expiration was comparable. These results are consistent with prior observations associating the PVL toxin with both community-acquired MRSA strains as well as severe staphylococcal pneumonia. The presence of the PVL toxin does not appear to otherwise influence the natural history of bacteremic S. aureus disease other than in prolonging the duration of fever.

C-reactive protein predicts persistent bacteremia caused by community-acquired methicillin-resistant Staphylococcus aureus strain.

There is limited data on persistent bacteremia (PB) caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Here, we aimed to investigate the clinical and microbiological characteristics of PB caused by the major CA-MRSA strain in Korea (ST72-SCCmecIV). All adult patients with S. aureus bacteremia were prospectively investigated from August 2008 to December 2018. Patients with ST72 MRSA bacteremia were included in the study. Patients were stratified into the PB group (defined as positive blood cultures for ≥ 3days) and short bacteremia (SB) group. A total of 291 patients were included, comprising 115 (39.5%) with PB and 176 (60.5%) with SB. Although the 30-day mortality did not differ between PB and SB, recurrent bacteremia within 12weeks was significantly more common in PB (8.7% vs 1.7%; P = 0.01). Multivariate analysis showed risk factors of PB were liver cirrhosis (adjusted odds ratio [aOR], 3.27; 95% confidence interval [CI], 1.50-7.12), infective endocarditis (aOR, 7.13; 95% CI, 1.37-37.12), bone and joint infections (aOR, 3.76; 95% CI, 1.62-8.77), C-reactive protein ≥ 10mg/dL (aOR, 2.20; 95% CI, 1.22-3.95), metastatic infection (aOR, 7.35; 95% CI, 3.53-15.29), and agr dysfunction (aOR, 2.47; 95% CI, 1.05-5.81). PB occurred in approximately 40% of bacteremia caused by ST72 MRSA with a significantly higher recurrence rate. Patients with risk factors of PB, including liver cirrhosis, high initial CRP, infective endocarditis, or bone and joint infections, might require early aggressive treatment.

Trends in Panton-Valentine Leukocidin (PVL)-Positive Methicillin-Resistant <i>Staphylococcus aureus</i> (MRSA) in Outpatients of a University Hospital

The isolation frequency of strains with genetic features of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has increased in inpatients. Additionally, the number of infectious diseases caused by Panton- Valentine leukocidin (PVL)-positive highly pathogenic MRSA strains has been increasing in communities. However, the prevalence of CA-MRSA strains in outpatients of hospitals is unknown. This study investigated the prevalence of CA-MRSA including PVL-positive MRSA strains among inpatients (n = 362) and outpatients (n = 184) between 2013 and 2017 at Tokai University Hachioji Hospital. The proportion of staphylococcal cassette chromosome (SCC) mec type IV, which is a major SCCmec type of CA-MRSA, increased significantly in inpatients (P < 0.01). In contrast, SCCmec type IV strains accounted for >50％ in outpatients every year. The isolation rate of PVL-positive MRSA strains in outpatients (12 strains, 6.5％) was significantly higher than that in inpatients (1 strain, 0.3％) (P < 0.01). Furthermore, the incidence of PVL-positive MRSA strains in 2016 to 2017 (8/70 strains, 11.4％) was significantly higher than that in 2013 to 2015 (4/114 strains, 3.5％) (P < 0.05). All PVL-positive MRSA strains were susceptible to minocycline, vancomycin, and linezolid. This study shows that the number of cases of PVL-positive MRSA strains is increasing in outpatients of a university hospital. Surveillance of PVL-positive MRSA strains for both inpatients and outpatients is necessary to prevent outbreaks of highly pathogenic MRSA strains.

Presence of egc-positive major clones ST 45, 30 and 22 among methicillin-resistant and\xa0methicillin-susceptible oral Staphylococcusaureus strains

The oral cavity may comprise a significant reservoir for Staphylococcus aureus but the data on molecular epidemiology and clonal distribution of oral strains are really scarce. This study aimed to evaluate the clonal relatedness in S. aureus isolated from oral cavity and their relationship with carriage of virulence genes, and antimicrobial resistance profiles. A total of 139 oral S. aureus isolates were obtained from 2327 analysed oral samples of dental patients. Antimicrobial susceptibility testing was performed. Isolates were characterized using protein A gene (spa) typing, spa-CC clonal complexes, toxin genes and SCCmec typing for MRSA. High resistance rates for penicillin, tetracycline and gentamicin were detected, respectively 58.3%, 42.4%, and 35.2%. Twelve (8.6%) S. aureus isolates were identified as MRSA. All of MRSA isolates were mecA-positive and mecC-negative. SCCmec IV was the most common type (66.7%), which was typical for community-acquired MRSA (CA-MRSA). Overall, the enterotoxin gene cluster (egc) was the most frequent detected virulence factor (44.9%), both in MSSA and MRSA isolates. Presence of genes encoding for the enterotoxins (sea, seb, sec, seh, sek), exfoliative toxin A (eta), and toxic shock syndrome toxin-1 (tst) was also observed. Strains carrying lukS-PV/lukF-PV genes belonged to SCCmecV- spa type t437. The most prevalent spa types were t091, t015, t084, t002, t571, and t026 among all 57 identified. Spa types, including 3 new ones, grouped in 6 different spa-CC clonal complexes, with four major dominated; CC45, CC30, CC5, and CC15. This study demonstrated that both methicillin-susceptible and methicillin-resistant major European clones of S. aureus could be isolated from the oral cavity of dental patients, with the emergence of PVL-positive CA-MRSA strains. The oral cavity should be considered as a possible source of toxigenic egc-positive S. aureus strains, in terms of potential risk of cross-infection and dissemination to other body sites.

A risk as an infection route: Nasal colonization of methicillin-resistant Staphylococcus aureus USA300 clone among contact sport athletes in Japan

Panton-Valentine leukocidin (PVL)-positive USA300 clone is a highly pathogenic and global epidemic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone. Athletes are particularly vulnerable to CA-MRSA infection because of the frequency of skin trauma, close-contact situations, and sharing of equipment that is customary in the athletic setting. We experienced a case of Japanese collegiate football player with septic pulmonary emboli secondary to infectious iliofemoral deep venous thrombosis caused by the USA300 clone. Here, we screened the nasal carriage of USA300 clone colonization among asymptomatic teammate of the patient to elucidate the infection route. Among 69 nasal samples, CA-MRSA strains were found in 5.8% (four samples). Molecular epidemiological analyses showed that three of the CA-MRSA strains were USA300 clone. Furthermore, pulsed-field gel electrophoresis revealed that all nasal USA300 clones showed 100% identity with the USA300 clone isolated from their teammate with critical infection. Our findings indicate that nasal colonization of the PVL-positive CA-MRSA, especially USA300 clone, pose a threat among contact sport athletes in Japan likewise other countries. An immediate infection control strategy for contact sport athletes is necessary to prevent outbreaks of PVL-positive CA-MRSA infections.

Protective activity of anti-lipoteichoic acid monoclonal antibody in single or combination therapies in methicillin-resistant Staphylococcus aureus-induced murine sepsis models

Previously, we generated and screened a panel of monoclonal antibodies (mAbs) against methicillin-resistant Staphylococcus aureus (MRSA) to identify protective mAbs in mouse infection models. One of these mAbs, ZBIA3H, bound to lipoteichoic acid (LTA) and exerted protective effects in a mouse sepsis model. To reinforce the ability of the mAb to protect against infection, combination therapies with the mAb and antibiotics need to be examined. Therefore, herein, we studied the efficacy of ZBIA3H (in combination or alone) in a mouse sepsis model. ZBIA3H improved the survival rate in the mouse models of sepsis induced by highly virulent or refractory S. aureus (community-acquired MRSA strain MW2, vancomycin-intermediate S. aureus strain Mu3, or vancomycin-resistant S. aureus strain VRS1). Furthermore, ZBIA3H remarkably improved the survival rate in combination with antimicrobial agents (vancomycin, daptomycin, or linezolid) in mouse sepsis models. From these results we conclude that anti-LTA mAb ZBIA3H or its humanized form is a promising mAb individually, or in combination with antibiotics, against clinical refractory infection of S. aureus.

Enantiomeric glycosylated cationic block co-beta-peptides eradicate Staphylococcus aureus biofilms and antibiotic-tolerant persisters

The treatment of bacterial infections is hindered by the presence of biofilms and metabolically inactive persisters. Here, we report the synthesis of an enantiomeric block co-beta-peptide, poly(amido-D-glucose)-block-poly(beta-L-lysine), with high yield and purity by one-shot one-pot anionic-ring opening (co)polymerization. The co-beta-peptide is bactericidal against methicillin-resistant Staphylococcus aureus (MRSA), including replicating, biofilm and persister bacterial cells, and also disperses biofilm biomass. It is active towards community-acquired and hospital-associated MRSA strains which are resistant to multiple drugs including vancomycin and daptomycin. Its antibacterial activity is superior to that of vancomycin in MRSA mouse and human ex vivo skin infection models, with no acute in vivo toxicity in repeated dosing in mice at above therapeutic levels. The copolymer displays bacteria-activated surfactant-like properties, resulting from contact with the bacterial envelope. Our results indicate that this class of non-toxic molecule, effective against different bacterial sub-populations, has promising potential for the treatment of S. aureus infections.

Preclinical Models and Methodologies for Monitoring Staphylococcus aureus Infections Using Noninvasive Optical Imaging.

In vivo whole-animal optical (bioluminescence and fluorescence) imaging of Staphylococcus aureus infections has provided the opportunity to noninvasively and longitudinally monitor the dynamics of the bacterial burden and ensuing host immune responses in live anesthetized animals. Herein, we describe several different mouse models of S. aureus skin infection, skin inflammation, incisional/excisional wound infections, as well as mouse and rabbit models of orthopedic implant infection, which utilized this imaging technology. These animal models and imaging methodologies provide insights into the pathogenesis of these infections and innate and adaptive immune responses, as well as the preclinical evaluation of diagnostic and treatment modalities. Noninvasive approaches to investigate host-pathogen interactions are extremely important as virulent community-acquired methicillin-resistant S. aureus strains (CA-MRSA) are spreading through the normal human population, becoming more antibiotic resistant and creating a serious threat to public health.

Staphylococcal Cassette Chromosome mec (SCCmec) Analysis of MRSA.

Methicillin-susceptible S. aureus changes to methicillin-resistant S. aureus (MRSA) upon the acquisition of staphylococcal cassette chromosome mec (SCCmec), a genomic island that encodes methicillin resistance. SCCmec elements in S. aureus are classified into different types based on the combination of mec gene complexes and ccr gene complexes, which share variations, five classes in mec and eight in ccr. To date, at least 13 types of SCCmec elements have been identified and each SCCmec type has individual characteristics. It is known that hospital-associated MRSA strains carry SCCmec elements of types, I, II, and III, and the majority of community-acquired MRSA strains carry characteristic SCCmec elements, type IV SCCmec or type V SCCmec. We herein describe multiplex PCR methods to type SCCmec elements by identifying the mec gene complex class and ccr gene complex type.

Detection and Colonization of Multidrug Resistant Organisms in a Regional Teaching Hospital of Taiwan.

This study evaluated the prevalence of clinical multidrug-resistant organisms (MDROs) and analyzed correlations between MDROs and patient characteristics in a regional teaching hospital of Taiwan. A retrospective comparative case-control study was conducted from January 2016 to August 2018 by collecting data from 486 hospitalized and non-hospitalized patients (M = 286, F = 200), including patient gender and age, microbial species, and antibiotic susceptibility. The results indicated that at least one MDRO was isolated from 5.3–6.3% of patients (p < 0.05), with an average age of 61.08 years. Of the MDROs strains, vancomycin-resistant enterococcus and carbapenem-resistant acinetobacter baumannii increased annually (p < 0.002 and p < 0.012, respectively). Three factors of age (over 60 years), treatment in an intensive care unit (ICU), and specimen category were statistically significant (p < 0.039, p < 0.001 and p < 0.001, respectively) and indicated that elderly patients in an ICU have a higher risk of being infected by MDROs. The outpatients infected by methicillin-resistant staphylococcus aureus (MRSA) were more frequent than inpatients, implying the existence of community-acquired MRSA strains. The results of this study could provide valuable information for the detection and colonization of multidrug-resistant organisms in hospital infection control systems.

SCCmec typing of PVL-positive community-acquired Staphylococcus aureus (CA-MRSA) at a Japanese hospital

The epidemiology of Panton-Valentine leukocidin (PVL)-positive MRSA in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was examined. Three hundred and forty-two CA-MRSA strains that were susceptible to imipenem and cefazolin were isolated from 1107 samples (intravenous catheter, blood, sputum, urine, skin, wound, and pharynx) from outpatients at Showa University Hospital in Japan between September 2009 and March 2017. The PVL gene was detected in 46 of 342 CA-MRSA strains, accounting for 13.5%. The type of SCCmec was determined by detection of each SCCmec-specific region, class complex, and ccr. SCCmec type IV comprised 33 strains, type V comprised 5 strains, type VII comprised 4 strains, and the unclassified type comprised 4 strains. Among the type IV strains, subtype IVa was dominant, comprising 23 of 33 strains, and the remaining 10 strains were of varying subtypes. The SCCmec type III-specific region, CZ049, was amplified in 2 type V strains, 4 type VII strains, and 4 unclassified strains. In 4 unclassified strains, CZ049 and ccr5 were detected, but neither the SCCmec-specific region nor class complex was detected.The PVL-positive rate was lower than that in Western countries. The SCCmec types of PVL-positive CA-MRSA strains were found to vary, indicating a diverse spreading route.

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 10years. 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 10years in Japan.