In vitro activity of ceftobiprole, linezolid, tigecycline, and 23 other antimicrobial agents against Staphylococcus aureus isolates in China

Antibacterial Activity of Selected Essential Oil Compounds Alone and in Combination with β-Lactam Antibiotics Against MRSA Strains

This study aimed to determine the effect of selected essential oil compounds (EOCs) on the antibacterial activity of β-lactam antibiotics (βLAs) against methicillin-resistant Staphylococcus aureus (MRSA) strains. The following parameters were studied: antibiotic susceptibility testing, detection of mecA gene and evaluation of genotypic relativity of isolates using molecular techniques, analysis of chemical composition applying Fourier-transform infrared (FTIR) spectroscopy, and determination of antibacterial activity of EOCs alone and in combination with βLAs against MRSA strains using microdilution and checkerboard methods. It was found that all isolates expressed MRSA and resistance phenotypes for macrolides, lincosamides, and streptogramins B. All isolates harbored the mecA gene and belonged to three distinct genotypes. Eight of the 10 EOCs showed efficient antimicrobial activity against the MRSA reference strain. The analysis of interaction between EOCs and βLAs against the MRSA reference strain revealed a synergistic and additive effect of the following combinations: methicillin (Met)-linalyl acetate (LinAc), penicillin G (Pen)-1,8-cineole (Cin), and Pen-LinAc. Analysis of EOC-βLA interactions showed a synergistic and additive effect in the following combinations: Met-LinAc (against low- and high-level βLAs resistance strains), Pen-Cin, and Pen-LinAc (against low-level βLAs resistance strains). It was also confirmed that changes in phosphodiester, -OH, -CH₂ and -CH₃ groups may change the interactions with βLAs. Moreover, the presence of two CH₃O- moieties in the Met molecule could also play a key role in the synergistic and additive mechanism of LinAc action with Met against MRSA strains. Direct therapy using a Met-LinAc combination may become an alternative treatment method for staphylococcal infections caused by MRSA. However, this unconventional therapy must be preceded by numerous cytotoxicity tests.

Bactericidal Capacity of a Heterogeneous TiO2/ZnO Nanocomposite against Multidrug-Resistant and Non-Multidrug-Resistant Bacterial Strains Associated with Nosocomial Infections

The surge of medical devices associated with nosocomial infection (NI) cases, especially by multidrug-resistant (MDR) bacterial strains, is one of the pressing issues of present health care systems. Metal oxide nanoparticles (MNPs) have become promising antibacterial agents against a wide range of bacterial strains. This work study is on the bactericidal capacity of heterogeneous TiO₂/ZnO nanocomposites with different weight percentages and concentrations against common MDR and non-MDR bacterial strains. The profiles on disk diffusion, minimum inhibitory concentration, minimum bactericidal concentration, tolerance determination, time-kill, and biofilm inhibition assay were determined after 24 h of direct contact with the nanocomposite samples. Findings from this work revealed that the heterogeneous TiO₂/ZnO nanocomposite with a 25T75Z weight ratio showed an optimal tolerance ratio against Gram-positive and -negative bacteria, indicating their bactericidal capacity. Further observation suggests that higher molar ratio of Zn²⁺ may possibly involve generation of active ion species that enhance bactericidal effect against Gram-positive bacterial strains, especially for the MDR strains. Nano-based technology using MNPs may provide a promising solution for the prevention and control of NIs. Further work on biocompatibility and cytotoxicity profiles of this nanocomposite are needed.

Screening of genes encoding adhesion factors and biofilm production in methicillin resistant strains of Staphylococcus aureus isolated from Palestinian patients

BACKGROUND

Intercellular adhesion and biofilm production by Staphylococcus aureus makes these bacteria resistant to antimicrobial therapy. Here, Methicillin-resistant Staphylococcus aureus (MRSA) strains were characterized and the prevalence of genes encoding adhesion factors and biofilm formation was determined.

RESULTS

All 248 MRSA isolates identified by cefoxitin disc diffusion were positive for the mecA gene. SCCmec-IV was the most frequently detected genotype (92.7%) and SCCmec-IVa was also very prevalent (84.3%). The quantitative microtiter plate assay showed that all the isolates were able to produce biofilm with levels ranging from high (21%) to moderate (46.4%) to low (32.7%). All the strains possessed the icaD/icaA genes and produced biofilm (P < 0.05). None of the isolates possessed the bap gene. Furthermore, 94.8% of the isolates were positive for eno, 80.2% for clfA and for clfB, 78.2% for fnbA, 76.2% for ebps, 62.2% for fib, 39.9% for cna and 29.0% for fnbB. Also, nearly 69.8% of the isolates were positive for the gene sarA. All four agr groups were present: agr group 1 was predominant with 39.5%; agr group 3. agr group 2 and 3 strains carried more toxin-producing genes, and frequently produced more toxin. Sixty-six (26.6%) of the strains were multidrug resistant. All were vancomycin sensitive. Agr group I is more resistant to ciprofloxacin and gentamicin while agr group III is more resistant to erythromycin. Maximum sensitivity was to gentamicin and SXT, and they could be considered drugs of choice for controlling MRSA mediated infections in this region.

CONCLUSIONS

Biofilm development in MRSA might be an ica dependent and one needs to investigate the involvement of other global regulators, agr and sarA, and their contribution to the biofilm phenotype, as the high rate of biofilm production among the studied strains of S. aureus.

Probing popular and political discourse on antimicrobial resistance in China

Background

Antimicrobial resistance (AMR) is an increasing threat to global public health that is largely exacerbated by the overuse and misuse of antimicrobial medicines. As the largest antimicrobials producer and user in the world, China has a critical role to play in combatting AMR. By examining Chinese news articles and policy statements, we aim to provide an authentic understanding of public discourse in China on AMR.

Methods

A search was conducted using two of the most comprehensive digital libraries for Chinese news media documents. Chinese policy documents were retrieved from official Chinese government websites. Records from June 2016 to May 2017 were included. Grounded theory was used to analyze included records, and we followed an iterative thematic synthesis process to categorize the key themes of each document.

Results

Across 64 news articles, most articles delivered general knowledge about AMR and debunked AMR-related myths, explored the implications of AMR-relevant policies, and discussed the misuse of antimicrobials in the agricultural sector. All policy documents provided guidance for healthcare workers, encouraging them to better manage antimicrobial prescriptions and usage.

Conclusions

While the Chinese media actively educates the public on strategies for AMR prevention, certain news articles risk misleading readers by downplaying the hazards of domestic AMR issues. Further, although several national policies are geared towards combatting AMR, the government faces difficult challenges in overcoming public misconceptions regarding antimicrobial use. Records from the regional level should also be examined to further explore China’s public discourse on AMR.

Electronic supplementary material

The online version of this article (10.1186/s41256-019-0097-z) contains supplementary material, which is available to authorized users.

Molecular analysis of immune evasion cluster (IEC) genes and intercellular adhesion gene cluster (ICA) among methicillin-resistant and methicillin-sensitive isolates of Staphylococcus aureus

Introduction

Resistance to antibiotics and presence of virulence factors play an important role in increased mortality associated with infection due to Staphylococcus aureus. In this study, we determine antibiotic resistance pattern, presence of the icaADBC locus as well as biofilm formation and distribution and diversity the immune evasion cluster (IEC) genes in clinical isolate of S. aureus from Kerman, Iran.

Materials and methods

During 15 months, 100 clinical isolates S. aureus recovered from different patients were admitted to Kerman University affiliated hospitals. Resistance to different antibiotic agents was determined by disk diffusion method. Phenotypic method was used to the determination of biofilm formation ability and methicillin-resistance S. aureus (MRSA). Polymerase chain reaction technique (PCR) was used to the detection of nuc, mecA, icaA, icaD, icaB, icaC, scn, sea, sak, sep and chp genes.

Results

Forty-four isolates were considered as MRSA and all of isolates were sensitive to vancomycin and linezolid. Our results showed, 77.2% (34/44) of MRSA and 8.9 % (5/56) of MSSA isolates were multidrug resistant. The predominant IEC variant was type B and our results displayed that 77.7% of the MRSA isolates harbor loci icaD and mecA. There was no significant difference in production biofilm between MSSA and MRSA isolates (P ≥ 0.05). There was significant difference in presence IEC types between MSSA and MRSA isolates (P = 0.000).

Conclusions

The presence of icaADBC locus may not be a determining factor for biofilm formation in Staphtlocooci and other mechanisms might be involved in this process.The high prevalence IEC types in MSSA isolates can indicate that the presence of these genes can be an advantage for pathogenesis of these isolates in different infections.

Molecular Epidemiology and Antibiotic Resistance Profiles of Methicillin-Resistant Staphylococcus aureus Strains in a Tertiary Hospital in China

Analysis of the genotypic characteristics and antimicrobial susceptibility patterns of methicillin-resistant Staphylococcus aureus (MRSA) is essential for the control and treatment of diseases caused by this important pathogen. In this study, MRSA isolates obtained from a tertiary caret hospital in China were subjected to spa typing, SCCmec typing, multiple locus sequence typing (MLST), and PCR targeting of the genes encoding Panton-Valentine leukocidin (PVL). The disk diffusion method was used to test the antimicrobial susceptibility of the isolates to 10 non-beta-lactam antibiotics. Among the 120 MRSA isolates studied, 18 spa types and 15 ST types were identified. The spa t311 type was the most common (a total of 60 isolates; 50%) among the study strains, and nearly all the t311 strains belonged to ST5, which is the most common ST type that was previously reported from China among the t002 isolates. ST5-II/t311 was the major prevalent clone (55, 45.8%), which was followed by ST5-II/t002 (12, 10.0%) and ST59-IV/t437 (11, 9.2%). PVL-encoding genes were found in 6.7% of the isolates. Although the ST5-II/t311 and ST5-II/t002 clones are different spa types, they shared the same resistance profile (clindamycin, erythromycin, and ciprofloxacin). Most isolates of the ST239-III/t037 clone were resistant to clindamycin, erythromycin, ciprofloxacin, gentamicin, tetracycline, and trimethoprim/sulfamethoxazole. By contrast, the MRSA isolates of the ST239-III/t030 clone were more resistant to rifampin, but they were susceptible to trimethoprim/sulfamethoxazole. Our data emphasize the need for ongoing epidemiologic surveillance.

Modeling Nosocomial Infections of Methicillin-Resistant Staphylococcus aureus with Environment Contamination<sup/>

In this work, we investigate the role of environmental contamination on the clinical epidemiology of antibiotic-resistant bacteria in hospitals. Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes infections in different parts of the body. It is tougher to treat than most strains of Staphylococcus aureus or staph, because it is resistant to some commonly used antibiotics. Both deterministic and stochastic models are constructed to describe the transmission characteristics of MRSA in hospital setting. The deterministic epidemic model includes five compartments: colonized and uncolonized patients, contaminated and uncontaminated health care workers (HCWs), and bacterial load in environment. The basic reproduction number R ₀ is calculated, and its numerical and sensitivity analysis has been performed to study the asymptotic behavior of the model, and to help identify factors responsible for observed patterns of infections. A stochastic epidemic model with stochastic simulations is also presented to supply a comprehensive analysis of its behavior. Data collected from Beijing Tongren Hospital will be used in the numerical simulations of our model. The results can be used to provide theoretical guidance for designing efficient control measures, such as increasing the hand hygiene compliance of HCWs and disinfection rate of environment, and decreasing the transmission rate between environment and patients and HCWs.

Pharmacokinetic drug evaluation of ceftobiprole for the treatment of MRSA

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA), while decreasing in overall incidence, is still a prominent concern world-wide. New agents coming to market in the last 10 years allow practitioners to optimize treatment for MRSA infections. Ceftobiprole is a cephalosporin agent with MRSA activity, currently approved in selected countries for the treatment of community-acquired pneumonia and hospital-acquired pneumonia. Areas covered: Relevant literature regarding spectrum of activity, pharmacokinetics, pharmacodynamics, and clinical trials will be discussed. Expert opinion: Ceftobiprole is an addition to a growing number of antimicrobials with activity against MRSA. Concern for appropriate dosing in critically ill patients remains due to its ineffectiveness for the treatment of ventilator-associated pneumonia (VAP). While ceftobiprole has activity against gram-negative organisms, the allowance for use of an additional agent for gram-negative infections in clinical trials limits recommendations for monotherapy for empirical treatment of HAP. Ceftobiprole's place in therapy will lie in its activity against gram positive organisms, such as Streptococcus spp. and Staphylococcus spp.

Methicillin-resistant Staphylococcus aureus nosocomial pneumonia: role of linezolid in the People's Republic of China

The burden of methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia in the People’s Republic of China is high, with methicillin-resistance rates greater than 80% reported for patients with S. aureus pneumonia treated in intensive care units. Historically, vancomycin was the treatment of choice for patients with hospital-acquired MRSA infections. Recent evidence suggests that the minimum inhibitory concentration for vancomycin is increasing. Additionally, patients treated with vancomycin require monitoring of vancomycin trough concentrations and can develop nephrotoxicity. Linezolid is a treatment option for patients with hospital-acquired MRSA infections that can be administered either intravenously or orally. Analysis of data from a worldwide linezolid surveillance program initiated in the year 2004 shows no evidence of increasing linezolid minimum inhibitory concentrations. The clinical efficacy of linezolid for patients with gram-positive, including MRSA, nosocomial pneumonia, was evaluated in numerous studies. In general, results from these studies show higher or similar clinical success with no mortality difference for linezolid compared to vancomycin treated patients. Results from a Phase IV study enrolling patients with MRSA-confirmed nosocomial pneumonia suggest higher clinical cure rates for linezolid compared to vancomycin treated patients. Although acquisition costs are higher for linezolid compared to vancomycin therapy, evidence suggests similar overall medical costs. Cost-analysis results from a Chinese perspective show that linezolid dominated vancomycin therapy for MRSA nosocomial pneumonia in ∼35% of bootstrap simulations whereas vancomycin dominated linezolid in less than 2% of bootstrap simulations. In summary, results from both clinical and economic studies, including studies conducted from a Chinese perspective, support the use of linezolid for the treatment of patients with MRSA nosocomial pneumonia.

Characterization of pediatric hospital-associated infection caused by methicillin-resistant Staphylococcus aureus in mainland China

BACKGROUND

This study was conducted to investigate the clinical features of hospital-associated infections (HAIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) in Chinese children, and the molecular characteristics of the bacteria.

METHODS

Patients with HAIs caused by MRSA were identified retrospectively. All isolates were analyzed using molecular typing and antimicrobial susceptibility tests.

RESULTS

In total, 150 patients were identified, with a median age of 18 months. The most common infection was pneumonia (55.3%), followed by skin and soft tissue infections (46%). Invasive infections were observed in 52 patients (34.7%), and their hospital stay was longer compared with non-invasive cases (21 vs 12 days, p = 0.047). A total of 16 sequence types (STs) were identified. ST239 and ST59 were common clones, accounting for 46% and 28% of cases, respectively. Compared with cases caused by ST239-SCCmecI-III, patients infected by ST59-SCCmecIV-V had a lower median age (11 vs 41 months, p = 0.047) and more commonly developed invasive infection (50% vs 18.8%, p = 0.006).

CONCLUSIONS

Invasive infections accounted for a large proportion of HAIs caused by MRSA. ST59-SCCmecIV/V, a common clone in the community, caused HAIs in Chinese children, more often infected younger children and caused invasive infections.

New epidemiology of Staphylococcus aureus infection in Asia

Not only is Asia the most populous region in the world, but inappropriate therapy, including self-medication with over-the-counter antimicrobial agents, is a common response to infectious diseases. The high antibiotic selective pressure among the overcrowded inhabitants creates an environment that is suitable for the rapid development and efficient spread of numerous multidrug-resistant pathogens. Indeed, Asia is among the regions with the highest prevalence rates of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) and community-associated methicillin-resistant S. aureus (CA-MRSA) in the world. Most hospitals in Asia are endemic for multidrug-resistant methicillin-resistant S. aureus (MRSA), with an estimated proportion from 28% (in Hong Kong and Indonesia) to >70% (in Korea) among all clinical S. aureus isolates in the early 2010s. Isolates with reduced susceptibility or a high level of resistance to glycopeptides have also been increasingly identified in the past few years. In contrast, the proportion of MRSA among community-associated S. aureus infections in Asian countries varies markedly, from <5% to >35%. Two pandemic HA-MRSA clones, namely multilocus sequence type (ST) 239 and ST5, are disseminated internationally in Asia, whereas the molecular epidemiology of CA-MRSA in Asia is characterized by clonal heterogeneity, similar to that in Europe. In this review, the epidemiology of S. aureus in both healthcare facilities and communities in Asia is addressed, with an emphasis on the prevalence, clonal structure and antibiotic resistant profiles of the MRSA strains. The novel MRSA strains from livestock animals have been considered to constitute a public health threat in western countries. The emerging livestock-associated MRSA strains in Asia are also included in this review.

Cost-Effectiveness of Linezolid versus Vancomycin among Patients with Methicillin-Resistant Staphylococcus aureus Confirmed Nosocomial Pneumonia in China

OBJECTIVE

To estimate the cost-effectiveness of intravenous linezolid as a first-line agent against intravenous vancomycin in treating methicillin-resistant Staphylococcus aureus-confirmed nosocomial pneumonia in four Chinese cities.

METHODS

A decision-analytic model of 4-week time horizon was used to conduct cost-effectiveness analyses from the payer's perspective. Clinical outcomes and resource use data were derived from a head-to-head trial, supplemented with local cost estimates based on hospital data via an expert panel. A series of scenario analyses were conducted to evaluate the impact of uncertainty around model inputs. All results were reported in 2012 Chinese Renminbi.

RESULTS

The predicted probability of overall treatment success was 0.629 and 0.602 for linezolid and vancomycin, respectively. Total inpatient costs varied across the four cities, ranging from ¥58,835 to ¥86,894 for linezolid and ¥58,390 to ¥87,033 for vancomycin, respectively. Linezolid was demonstrated to be a dominant treatment strategy in Guangzhou. In Beijing, Nanjing, and Xi'an, incremental cost-effectiveness ratios in terms of additional successfully treated patient were ¥1,861, ¥163, and ¥16,509, respectively. Dominance by linezolid was observed in some scenario analyses with parameters such as treatment duration, inclusion of cost of managing adverse events, and drug acquisition costs being the main drivers of cost-effectiveness results.

CONCLUSIONS

Despite linezolid's higher drug acquisition cost, its superior clinical efficacy renders it a likely cost-effective alternative for the treatment of methicillin-resistant Staphylococcus aureus-confirmed nosocomial pneumonia as compared with branded vancomycin from the payer perspectives of Beijing, Guangzhou, Nanjing, and Xi'an.

An improved MLVF method and its comparison with traditional MLVF, spa typing, MLST/SCCmec and PFGE for the typing of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has become an important nosocomial pathogen, causing considerable morbidity and mortality. During the last 20 years, a variety of genotyping methods have been introduced for screening the prevalence of MRSA. In this study, we developed and evaluated an improved approach capillary gel electrophoresis based multilocus variable-number tandem-repeat fingerprinting (CGE/MLVF) for rapid MRSA typing. A total of 42 well-characterized strains and 116 non-repetitive clinical MRSA isolates collected from six hospitals in northeast China between 2009 and 2010 were tested. The results obtained by CGE/MLVF against clinical isolates were compared with traditional MLVF, spa typing, Multilocus sequence typing/ staphylococcal cassette chromosome mec (MLST/SCCmec) and pulse field gel electrophoresis (PFGE). The discriminatory power estimated by Simpson's index of diversity was 0.855 (28 types), 0.855 (28 patterns), 0.623 (11 types), 0.517 (8 types) and 0.854 (28 patterns) for CGE/MLVF, traditional MLVF, spa typing, MLST/SCCmec and PFGE, respectively. All methods tested showed a satisfied concordance in clonal complex level calculated by adjusted Rand's coefficient. CGE/MLVF showed better reproducibility and accuracy than traditional MLVF and PFGE methods. In addition, the CGE/MLVF has potential to produce portable results. In conclusion, CGE/MLVF is a rapid and easy to use MRSA typing method with lower cost, good reproducibility and high discriminatory power for monitoring the outbreak and clonal spread of MRSA isolates.

Antimicrobial resistance and molecular epidemiology of Staphylococcus aureus from Ulaanbaatar, Mongolia

This study aimed to characterize Staphylococcus aureus (S. aureus) strains isolated from human infections in Mongolia. Infection samples were collected at two time periods (2007–08 and 2011) by the National Center for Communicable Diseases (NCCD) in Ulaanbaatar, Mongolia. S. aureus isolates were characterized using polymerase chain reaction (PCR) for mecA, PVL, and sasX genes and tested for agr functionality. All isolates were also spa typed. A subset of isolates selected by frequency of spa types was subjected to antimicrobial susceptibility testing and multilocus sequence typing. Among 251 S. aureus isolates, genotyping demonstrated methicillin resistance in 8.8% of isolates (22/251). Approximately 28% of the tested S. aureus isolates were observed to be multidrug resistant (MDR). Sequence type (ST) 154 (spa t667) was observed to be a strain with high virulence potential, as all isolates for this spa type were positive for PVL, had a functional agr system and 78% were MDR. S. aureus isolates of ST239 (spa t037) were observed to cause infections and roughly 60% had functional agr system with a greater proportion being MDR. Additionally, new multilocus sequence types and new spa types were identified, warranting continued surveillance for S. aureus in this region.

Current status of Staphylococcus aureus infection in a central teaching hospital in Shanghai, China

Background

To control the spread of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, infection control measures such as hand hygiene practices were introduced into the teaching hospitals in Shanghai, China, in 2008. Currently, there is limited information characterizing the latest hospital-acquired S. aureus infections in this area. Therefore, we sought to determine the prevalence, molecular characteristics, and genotype-phenotype correlation of hospital-acquired S. aureus infections in Huashan Hospital, one of the largest teaching hospitals in Shanghai.

Results

Among 608 hospital-acquired S. aureus clinical isolates obtained from January to December of 2011 in Huashan Hospital, 68.1% were MRSA. The predominant MRSA clones were ST239-SCCmecIII and ST5-SCCmecII. ST239 was mainly recovered from respiratory specimens and sterile body fluids, ST5 was associated with respiratory specimens and blood, and ST1 was most prevalent in urine samples. In this study, 31 dispersed sequence types (STs) of methicillin-susceptible S. aureus (MSSA) were identified, most of which caused skin/soft tissue infection and bacteremia. The frequencies of pvl-, muPA-, and qacA/B-positive isolates were 1.6, 9.9, and 11.8% respectively. MuPA was more frequently identified in ST1 and ST5, and qacA/B was more prevalent in ST239 and ST5. Most of the pvl-positive isolates were MSSA, whereas the majority of muPA- and qacA/B-positive isolates were MRSA. ST239 and ST5 had higher resistance rates to multiple antibiotics. In Huashan Hospital, the infection rate in the intensive care unit (ICU) was 3.9 per 1000 hospitalized days, but only 1.2 per 1000 hospitalized days in the other wards. Each ward harbored its own dominant STs. Pulsed-field gel electrophoresis showed diversity within the same epidemic S. aureus clones originating from the same wards.

Conclusion

There is still a high prevalence of MRSA infections in the teaching hospital in Shanghai. There were also differences in the major infection types caused by MRSA and MSSA, and hospital-acquired S. aureus infections in the ICU of Huashan Hospital pose a greater threat to patient safety than in other wards. The high proportion of multiple antibiotic and chlorhexidine-based antiseptic-resistant clones in this hospital underscores the need for more effective infection control measures to help curtail dissemination of MRSA to hospitalized patients.

In vitro activity of sodium new houttuyfonate alone and in combination with oxacillin or netilmicin against methicillin-resistant Staphylococcus aureus

Background

Staphylococcus aureus can cause severe infections, including bacteremia and sepsis. The spread of methicillin-resistant Staphylococcus aureus (MRSA) highlights the need for novel treatment options. Sodium new houttuyfonate (SNH) is an analogue of houttuynin, the main antibacterial ingredient of Houttuynia cordata Thunb. The aim of this study was to evaluate in vitro activity of SNH and its potential for synergy with antibiotics against hospital-associated MRSA.

Methodology

A total of 103 MRSA clinical isolates recovered in two hospitals in Beijing were evaluated for susceptibility to SNH, oxacillin, cephalothin, meropenem, vancomycin, levofloxacin, minocycline, netilmicin, and trimethoprim/sulfamethoxazole by broth microdilution. Ten isolates were evaluated for potential for synergy between SNH and the antibiotics above by checkerboard assay. Time-kill analysis was performed in three isolates to characterize the kill kinetics of SNH alone and in combination with the antibiotics that engendered synergy in checkerboard assays. Besides, two reference strains were included in all assays.

Principal Findings

SNH inhibited all test strains with minimum inhibitory concentrations (MICs) ranging from 16 to 64 µg/mL in susceptibility tests, and displayed inhibition to bacterial growth in concentration-dependent manner in time-kill analysis. In synergy studies, the combinations of SNH-oxacillin, SNH-cephalothin, SNH-meropenem and SNH-netilmicin showed synergistic effects against 12 MRSA strains with median fractional inhibitory concentration (FIC) indices of 0.38, 0.38, 0.25 and 0.38 in checkerboard assays. In time-kill analysis, SNH at 1/2 MIC in combination with oxacillin at 1/128 to 1/64 MIC or netilmicin at 1/8 to 1/2 MIC decreased the viable colonies by ≥2log₁₀ CFU/mL.

Conclusions/Significance

SNH demonstrated in vitro antibacterial activity against 103 hospital-associated MRSA isolates. Combinations of sub-MIC levels of SNH and oxacillin or netilmicin significantly improved the in vitro antibacterial activity against MRSA compared with either drug alone. The SNH-based combinations showed promise in combating MRSA.

Molecular and phenotypic evidence for the spread of three major methicillin-resistant Staphylococcus aureus clones associated with two characteristic antimicrobial resistance profiles in China

OBJECTIVES

The distribution of methicillin-resistant Staphylococcus aureus (MRSA) clones is dynamic and geographically unique. To understand the changing epidemiology of MRSA infections in China, we performed a prospective, multicity surveillance study with molecular typing and phenotypic analysis to determine the association of major prevalent clones with their antimicrobial resistance profiles.

METHODS

A total of 517 S. aureus isolates collected between January 2009 and March 2012 from six cities in China were subjected to antibiogram analysis and molecular typing, including staphylococcal cassette chromosome mec typing, multilocus sequence typing, staphylococcal protein A gene typing and PFGE typing.

RESULTS

Among the isolates collected, 309 were characterized as MRSA, with a prevalence of 59.8%. Three major clones were found to be prevalent in China: ST239-MRSA-III-t030, ST239-MRSA-III-t037 and ST5-MRSA-II-t002. These three clones were associated with two characteristic resistance profiles, namely, gentamicin/ciprofloxacin/rifampicin/levofloxacin for the first clone and gentamicin/ciprofloxacin/clindamycin/erythromycin/tetracycline/levofloxacin/trimethoprim/sulfamethoxazole for the latter two. Several geographically unique minor clones were also identified.

CONCLUSIONS

The predominant MRSA clones in China were associated with characteristic antimicrobial resistance profiles. Antibiotics for treating patients with MRSA infections can be selected based on the strain typing data.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pharmacokinetic and pharmacodynamics evaluation of ceftobiprole medocaril for the treatment of hospital-acquired pneumonia

INTRODUCTION

Ceftobiprole is a cephalosporin with activity against methicillin-resistant Staphylococcus aureus, Enterobacteriaceae, and Pseudomonas aeruginosa with a promising role in the treatment of hospital-acquired pneumonia (HAP). Cure rates, however, with ceftobiprole at the doses studied may be inferior to conventional treatment in the ventilator-acquired subset of HAP.

AREAS COVERED

Literature was sought using PubMed and through abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy (2006 - 2012) and the European Congress of Clinical Microbiology and Infectious Diseases (2007 - 2012). The authors used the search terms "ceftobiprole," "BAL9141," "RO63-9141," "BAL5788," and 'RO5788." The article discusses the activity, mechanism of action, pharmacokinetics (PK), pharmacodynamics (PD), and clinical trials of ceftobiprole in HAP. The article also provides discussion of how PK/PD parameters play a role in the outcome of HAP treatment and how dosing in ventilator-associated pneumonia (VAP) should be reconsidered in light of altered PK/PD.

EXPERT OPINION

In patients with normal PK and non-VAP, ceftobiprole is effective for the treatment of HAP in the recommended doses, ceftobiprole is unlikely to achieve the desired PD targets when PK parameters are altered in VAP (e.g., increased volume of distribution and clearance). In these settings, off-label use at higher doses may overcome these limitations; but in the presence of alternative therapies, it cannot be currently recommended.

Phenotypic and molecular characterization of Staphylococcus aureus recovered from different clinical specimens of inpatients at a teaching hospital in Shanghai between 2005 and 2010

Staphylococcus aureus, including meticillin-sensitive and -resistant S. aureus (MSSA and MRSA, respectively), is associated with severe nosocomial human infections. This study aimed to investigate the molecular profile, including the dynamic changes and genotype/phenotype correlation, of S. aureus isolates recovered from different clinical specimens of inpatients with S. aureus infection over a 6-year span at a teaching hospital in Shanghai, China. Between 2005 and 2010, a random sample of 610 unique S. aureus isolates was collected from different clinical samples of inpatients with S. aureus infection for molecular and antibiotic susceptibility analysis. The results showed that, among the 610 S. aureus isolates, 20 sequence types (STs) determined by multi-locus sequence typing (primarily ST239, ST5, ST7, ST188 and ST398) and 52 spa types (primarily t002, t037, t030 and t601) were found. In total, 444 isolates (72.8 %) were MRSA and 166 (27.2 %) were MSSA. ST239-MRSA-III-spa t037 and ST5-MRSA-II-spa t002 were the predominant MRSA clones. From 2005 to 2010, spa t002, spa t037 and their corresponding STs (ST5 and ST239) were the most frequent clones among all of the S. aureus isolates and showed the most resistant phenotypes to various antibiotics. Generally, the different genotypes showed different drug resistance rates, but no isolates were resistant to vancomycin, teicoplanin or linezolid. The profiles of virulence and resistance genes differed by genetic background, with the ST239 and ST5 strains showing higher resistance rates to gentamicin, cefoxitin, ampicillin, cefazolin, erythromycin, clindamycin and levofloxacin than strains of other types. Moreover, the antiseptic resistance genes qacA/B were generally associated with these two types. The prevalence of STs was different among different clinical specimens and also changed by year. Recently (2009-2010), the distribution of predominant MRSA clones decreased, whilst the prevalence of non-predominant MSSA clones increased, especially for the isolates causing bacteraemia. Continual monitoring of clinical isolates is necessary to develop and maintain an effective strategy against S. aureus infection in the hospital setting.

Multidrug-resistant clones of community-associated meticillin-resistant Staphylococcus aureus isolated from Chinese children and the resistance genes to clindamycin and mupirocin

This study aimed to correlate the multidrug resistance (MDR) and sequence type (ST) clones of community-associated (CA) meticillin-resistant Staphylococcus aureus (MRSA) to identify the genes responsible for clindamycin and mupirocin resistance in S. aureus isolates from paediatric hospitals in mainland China. A total of 435 S. aureus isolates were collected. Compared with CA meticillin-susceptible S. aureus (MSSA), the resistance rates of CA-MRSA to ciprofloxacin, chloramphenicol, gentamicin and tetracycline were higher (19.0 vs 2.6 %, P<0.001; 14.7 vs 3.1 %, P<0.001; 14.7 vs 3.1 %, P<0.01; and 46.0 vs 13.3 %, P<0.001, respectively). Compared with hospital-associated (HA)-MRSA, the resistance rates of CA-MRSA to ciprofloxacin, gentamicin, rifampicin, tetracycline and trimethoprim-sulfamethoxazole were lower (19 vs 94.8 %, P<0.001; 14.7 vs 84.4 %, P<0.001; 5.5 vs 88.3 %, P<0.001; 46 vs 94.8 %, P<0.001; and 1.8 vs 9.1 %, P<0.01, respectively). The resistance rates of CA-MRSA, HA-MRSA and CA-MSSA to clindamycin (92.0, 77.9 and 64.1 %, respectively) and erythromycin (85.9, 77.9 and 63.1 %, respectively) were high. The MDR rates (resistance to three or more non-β-lactams) were 49.6, 100 and 14 % in the CA-MRSA, HA-MRSA and CA-MSSA isolates, respectively. Five of seven ST clones in the CA-MRSA isolates, namely ST59, ST338, ST45, ST910 and ST965, had MDR rates of >50 % (67.9, 87.5, 100, 50 and 83.3 %, respectively). The constitutive phenotype of macrolide-lincosamide-streptogramin B (MLS(B)) resistance (69 %) and the ermB gene (38.1 %) predominated among the MLS(B)-resistant CA S. aureus strains. The resistance rate to mupirocin was 2.3 % and plasmids carrying the mupA gene varied in size between 23 and 54.2 kb in six strains with high-level resistance as determined by Southern blot analysis. The present study showed that resistance to non-β-lactams, especially to clindamycin, is high in CA-MRSA isolates from Chinese children and that the profile of resistance is related to clonal type. This study revealed distinctive patterns of MLS(B)-resistant genes among CA S. aureus isolates.

Molecular characterization and antimicrobial susceptibility of nasal Staphylococcus aureus isolates from a Chinese medical college campus

Staphylococcus aureus colonization and infection occur more commonly among persons living or working in crowded conditions, but characterization of S. aureus colonization within medical communities in China is lacking. A total of 144 (15.4%, 144/935) S. aureus isolates, including 28 (3.0%, 28/935) MRSA isolates, were recovered from the nares of 935 healthy human volunteers residing on a Chinese medical college campus. All S. aureus isolates were susceptible to vancomycin, quinupristin/dalfopristin and linezolid but the majority were resistant to penicillin (96.5%), ampicillin/sulbactam (83.3%) and trimethoprim/sulfamethoxazole (93.1%). 82%, (23/28) of the MRSA isolates and 66% (77/116) of the MSSA isolates were resistant to multiple antibiotics, and 3 MRSA isolates were resistant to mupirocin—an agent commonly used for nasal decolonization. 16 different sequence types (STs), as well as SCCmec genes II, III, IVd, and V, were represented among MRSA isolates. We also identified, for the first time, two novel STs (ST1778 and ST1779) and 5 novel spa types for MRSA. MRSA isolates were distributed in different sporadic clones, and ST59-MRSA-VId- t437 was found within 3 MRSA isolates. Moreover, one isolate with multidrug resistance belonging to ST398-MRSA-V- t571 associated with animal infections was identified, and 3 isolates distributed in three different clones harbored PVL genes. Collectively, these data indicate a high prevalence of nasal MRSA carriage and molecular heterogeneity of S. aureus isolates among persons residing on a Chinese medical college campus. Identification of epidemic MRSA clones associated with community infection supports the need for more effective infection control measures to reduce nasal carriage and prevent dissemination of MRSA to hospitalized patients and health care workers in this community.

Modelling the transmission dynamics of meticillin-resistant Staphylococcus aureus in Beijing Tongren hospital

Semi-professional volunteers work in many tertiary care hospitals in China as healthcare assistants. Proper infection control measures are needed to reduce nosocomial transmission involving volunteers. A compartmental model was constructed to describe the transmission characteristics of meticillin-resistant Staphylococcus aureus (MRSA) in the emergency ward (EW) and respiratory intensive care unit (RICU) for volunteers in Beijing Tongren Hospital, Beijing, China. The model consists of components describing uncolonized and colonized patients, uncontaminated and contaminated healthcare workers (HCWs), and uncontaminated and contaminated volunteers. The basic reproduction number (R(0)) was calculated, and the dependence of R(0) on various model parameters was analysed. Moreover, simulations of the model were performed for comparision with the reported data on the numbers of colonized patients in the EW and RICU from 3 March 2009 to 28 February 2010, respectively. Sensitivity analysis of R(0) showed that increasing handwashing compliance among HCWs and volunteers would reduce the risk of transmission dramatically. As volunteers care for patients on a one-to-one basis, this study showed that the number of MRSA-positive patients would increase if volunteers were replaced by HCWs. Therefore, in addition to improving hand hygiene among HCWs, the employment of properly trained volunteers is an attractive alternative to decrease MRSA and other multi-drug resistant bacteria infections in the hospital setting.

In vitro activity of minocycline combined with fosfomycin against clinical isolates of methicillin-resistant Staphylococcus aureus

This study aimed to evaluate the in vitro activity of minocycline combined with fosfomycin against isolates of methicillin-resistant Staphylococcus aureus (MRSA). A total of 87 clinical isolates of MRSA collected from three Chinese hospitals were included in the study. The checkerboard method with determination of the fractional IC index (FICI) was used to determine whether antibiotic combinations act synergistically against these isolates. The susceptibility results for minocycline and fosfomycin were interpreted according to the most relevant criteria. The results demonstrated the following interactions: 76 isolates (87.4%) showed synergistic interactions (FICI0.5) and 11 isolates (12.6%) showed indifferent interactions (0.5<FICI<4). No antagonistic interactions (FICI4) were observed. The combination of minocycline and fosfomycin can be synergistic against MRSA. Further studies are required to determine the potential clinical role of this combination regimen as a therapeutic alternative for certain types of MRSA infections.

Increasing resistance in multiresistant methicillin-resistant Staphylococcus aureus clones isolated from a Chinese hospital over a 5-year period

BACKGROUND

The aim was to study the changes in the antimicrobial resistance of methicillin-resistant Staphylococcus aureus (MRSA) clones over a 5-year period (from 2000 to 2005) at a representative hospital in Beijing, China.

METHODS

A total of 100 randomly selected MRSA strains were analyzed using antimicrobial susceptibility testing, pulsed-field gel electrophoresis, spa typing, multilocus sequence typing, SCCmec typing, and PCR for the Panton-Valentine leukocidin virulence factor.

RESULTS

Resistance to rifampin greatly increased from 32% (16/50) to 68% (34/50). High-level mupirocin-resistant isolates were found only in 2005, when four were identified. Intermediate susceptibly to quinupristin-dalfopristin increased from 22% (11/50) to 52% (26/50) between 2000 and 2005. The main antimicrobial resistance profiles changed from TC-GM-CI-EM-CM in 2000 to TC-GM-CI-EM-CM-RI in 2005. The main pulsed-field gel electrophoresis type changed from types C, L, and E in 2000 to types J, F, and N, respectively, in 2005. ST239-MRSA-III was the most predominant clone in 2000 and 2005, whereas ST5-MRSA-II was found only in 2005.

CONCLUSIONS

There were increasing levels of antimicrobial resistance and epidemiological changes in the hospital-associated MRSA strains isolated in this facility between 2000 and 2005.

Characterization of virulence factors and genetic background of Staphylococcus aureus isolated from Peking University People's Hospital between 2005 and 2009

The aim of this study was to investigate both the genetic features of MRSA strains and the occurrence of virulence factors produced by Staphylococcus aureus strains isolated from Peking University People's Hospital in Beijing, China, between 2005 and 2009. A total of 179 S. aureus strains were isolated, 139 of which were MRSA. The MRSA strains were characterized epidemiologically by SCCmec typing, spa typing and agr typing, then were classified into different genetic groups. The prevalence of genes coding for 14 exotoxins and eight adhesion factors among the S. aureus samples was assessed via polymerase chain reaction. Cluster analysis based on virulence factors-encoding gene content was performed to divide the MRSA isolates into valid clusters. Correspondence analysis was done to analyze the correlation between virulence factors clusters and genetic groups. JCSC1716-agrI-t030 (67.6%), SCCmec-IIIA-agrI-t030 (14.4%), SCCmec-IIIA-agrI-t037 (8.6%) and SCCmecII-agrII-t002 (2.2%) were four predominant MRSA clones. PVL was positive only in MSSA strains, there were at least three superantigenic toxins in our HA-MRSA clones, the prevalence of 16 virulence factors genes (sea, seb, sec, sed, seg, sei, sej, pvl, lukE-lukD, eta, bbp, can, ebp, clfA, fib, fnbB) in MRSA and MSSA was found to be significantly different from MSSA (P < 0.05). Results of correspondence analysis among clusters based on virulence factors genes and groups based on genetic typing illustrated not only the correspondence relationship between groups and clusters overall (P < 0.001), but also the genetic diversity of MRSA strains with respect to virulence factors genes.

Rapid change of methicillin-resistant Staphylococcus aureus clones in a Chinese tertiary care hospital over a 15-year period

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) has been increasing yearly at Peking Union Medical College Hospital (PUMCH). In order to understand the molecular evolution of MRSA at PUMCH, a total of 466 nonduplicate S. aureus isolates, including 302 MRSA and 164 methicillin-susceptible (MSSA) isolates recovered from 1994 to 2008 were characterized by staphylococcal cassette chromosome mec (SCCmec) typing, spa typing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). The 302 MRSA isolates were classified into 12 spa types and 9 sequence types (STs). During the years from 1994 to 2000, the most predominant MRSA clone was ST239-MRSA-III-spa t037. Since 2000, ST239-MRSA-III-spa t030 has rapidly replaced t037 and become the major clone. Another clone, ST5-MRSA-II-spa t002 emerged in 2002 and constantly existed at a low prevalence rate. The 164 MSSA isolates were classified into 62 spa types and 40 STs. ST398 was the most common MLST type for MSSA, followed by ST59, ST7, ST15, and ST1. Several MSSA genotypes, including ST398, ST1, ST121, and ST59, were identical to well-known epidemic community-acquired MRSA (CA-MRSA) isolates. MLST eBURST analysis revealed that the ST5, ST59, and ST965 clones coexisted in both MRSA and MSSA, which suggested that these MRSA clones might have evolved from MSSA by the acquisition of SCCmec. Two pvl-positive ST59-MRSA-IV isolates were identified as CA-MRSA according to the clinical data. Overall, our data showed that the ST239-MRSA-III-spa t037 clone was replaced by the emerging ST239-MRSA-III-spa t030 clone, indicating a rapid change of MRSA at a tertiary care hospital in China over a 15-year period.

[Update on antimicrobial chemotherapy]

There is a constant need for new antibacterial agents because of the unavoidable development of bacterial resistance that follows the introduction of antibiotics in clinical practice. As observed in many fields, innovation generally comes by series. For instance, a wide variety of broad-spectrum antibacterial agents became available between the 1970s and the 1990s, such as cephalosporins, penicillin/beta-lactamase inhibitor combinations, carbapenems, and fluoroquinolones. Over the last 2 decades, the arrival of new antibacterial drugs on the market has dramatically slowed, leaving a frequent gap between isolation of resistant pathogens and effective treatment options. In fact, many pharmaceutical companies focused on the development of narrow-spectrum antibiotics targeted at multidrug-resistant Gram-positive bacteria (e.g. methicillin-resistant Staphylococcus aureus, penicillin resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecium). Therefore, multidrug-resistant Gram-negative bacteria (e.g. extended-spectrum beta-lactamase-producing Enterobacteriaceae, carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter baumannii) recently emerged and rapidly spread worldwide. Even if some molecules were developed, new molecules for infections caused by these multidrug-resistant Gram-negative bacteria remain remarkably scarce compared to those for Gram-positive infections. This review summarises the major microbiological, pharmacological, and clinical properties of systemic antibiotics recently marketed in France (i.e. linezolid, daptomycin, tigecycline, ertapenem, and doripenem) as well as those of antibacterial drugs currently in development (i.e. ceftobiprole, ceftaroline, dalbavancin, telavancin, oritavancin, iclaprim, and ramoplanin) or available in other countries (i.e. garenoxacin, sitafloxacin, and temocillin).

Nasal colonization of and clonal transmission of methicillin-susceptible Staphylococcus aureus among Chinese military volunteers

Military facilities provide unique opportunities for studying Staphylococcus aureus nasal colonization and transmission patterns. In this cross-sectional observational study, we assessed the prevalence of S. aureus nasal colonization among Chinese military volunteers in two camps in the Beijing area. Antimicrobial resistance patterns, risk factors for colonization, and transmission patterns using pulsed-field gel electrophoresis were also evaluated. From May to July 2007, 1,044 nasal swabs were collected from military volunteers from suburban (560) and urban (484) camps. A total of 209 S. aureus isolates were recovered, of which all were methicillin susceptible. Independent factors associated with methicillin-susceptible S. aureus (MSSA) nasal colonization included younger age (odds ratio [OR] = 1.51, 95% confidence interval [95% CI] = 1.03 to 2.21, P = 0.0347), higher education (OR = 1.38, 95% CI = 1.10 to 1.73, P = 0.0056), shorter length of service (OR = 1.74, 95% CI = 1.28 to 2.36, P = 0.0004), nonsmoking (OR = 1.61, 95% CI = 1.14 to 2.28, P = 0.0069), and inactive participation in social events (OR = 2.40, 95% CI = 1.25 to 5.49, P = 0.0082). Among 209 MSSA isolates, 126 (60.3%) were determined to be epidemic and a total of 12 genotypes were identified, of which four (90 isolates [71.4%]) represented the majority of strains. Length of service and camp location were statistically related to the four major MSSA genotype clonal transmissions. Our data indicated that MSSA, not methicillin-resistant S. aureus (MRSA), nasal colonization and clonal transmission occur in healthy military volunteers in Beijing. Younger, female, nonsmoking volunteers with higher education, little or no participation in social events, and less time in service are at higher risk for nasal MSSA carriage.

Molecular evidence for spread of two major methicillin-resistant Staphylococcus aureus clones with a unique geographic distribution in Chinese hospitals

Methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) is a serious problem worldwide. To investigate the molecular epidemiology of MRSA isolates in China, a total of 702 MRSA isolates collected from 18 teaching hospitals in 14 cities between 2005 and 2006 were characterized by antibiogram analysis, pulsed-field gel electrophoresis (PFGE), staphylococcal cassette chromosome mec (SCCmec) typing, and spa typing; and 102 isolates were selected for multilocus sequence typing (MLST). Overall, SCCmec type III was the most popular type and was found in 541 isolates (77.1%), followed by SCCmec type II (109/702; 15.5%). Twenty-four PFGE types were obtained among 395 isolates collected in 2005, and 18 spa types were obtained among 702 isolates. spa type t030, which corresponded to PFEG types A to E, constituted 52.0% (365/702) of all isolates, and isolates of this type were present in all 14 cities; spa type t037, which corresponded to PFGE types F and G, accounted for 25.5% (179/702) of all isolates, and isolates of this type were identified in 12 cities. The two spa genotypes belonged to sequence type 239 (ST239) and carried SCCmec type III. spa type t002, which included isolates of PFGE types L to T, made up 16.0% (112/702) of the isolates that belonged to ST5 and SCCmec type II, and isolates of this type were distributed in 12 cities. The distribution of spa types varied among the regions. spa type t002 was the most common in Dalian (53.4%) and Shenyang (44.4%); spa type t037 was predominant in Shanghai (74.8%), whereas spa type t030 was the most common in the other cities. Two isolates from Guangzhou that harbored SCCmec type IVa with ST59 and ST88 were identified as community-associated MRSA. The prevalence of the Panton-Valentine leukocidin gene was 2.3%. The data documented two major epidemic MRSA clones, ST239-MRSA-SCCmec type III and ST5-MRSA-SCCmec type II, with unique geographic distributions across China.