Hospital-acquired Methicillin-resistant Staphylococcus Aureus Research Articles

SCCmec types and pvl gene in methicillin-resistant Staphylococcus aureus strains from children hospitalized in a tertiary care hospital in Mexico.

The aim of this study was to determine the prevalence, SCCmec types, presence of the Panton-Valentine leukocidin (PVL) gene, and susceptibility to antibiotics of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from hospitalized children. From August 2009 to September 2011, 291 S. aureus strains were isolated from normally sterile body sites, of which 190 (65%) were MRSA. One hundred and two of the MRSA strains were genetically evaluated. SCCmec genotypes were identified by M-PCR and the PVL gene (pvl) by end-point PCR. Resistance to erythromycin, rifampicin, clindamycin, and trimethoprim-sulfamethoxazole (SXT) was assessed by Kirby-Bauer disk diffusion method in accordance with the Clinical and Laboratory Standards Institute guidelines of 2012. Of the 102 strains evaluated, 97 (95%) were SCCmec type II, 5 (5%) were SCCmec type IVa, and all (100%) were pvl-negative. Resistance to erythromycin, clindamycin, rifampicin, and SXT was 97%, 95%, 0%, and 0%, respectively. The prevalence of hospital-acquired MRSA was high. SCCmec type II was predominant and the pvl gene appeared not to play any role in the virulence of the MRSA strains from hospitalized children.

Molecular epidemiological characteristics and clonal genetic diversity of Staphylococcus aureus with different origins in China.

To understand the intrinsic links and epidemic features of Staphylococcus aureus, isolates of this bacterium were collected from different origins in China. A total of 503 isolates from different sources were tested for the presence of methicillin-resistant Staphylococcus aureus (MRSA) and types of staphylococcal cassette chromosome mec (SCCmec) elements. Of these isolates, 250 were analyzed by multilocus sequence typing (MLST). Results showed that MRSA isolates account for 21.67% and have five types. SCCmec type I, II, and III isolates were all from humans, while SCCmec type IV, V, and untypeable MRSA isolates were from clinical origin, pigs, raw milk, or environments. The results by MLST showed considerable molecular heterogeneity in 52 different sequence types (STs) including 16 novel STs, which yielded 7 clonal complexes (CCs) and 5 doublets (Ds). The results from these analyses showed that hospital-acquired MRSA (HA-MRSA), rather than community-associated MRSA (CA-MRSA), remained the major pathogenic bacterium in the clinical setting. CA-MRSA infections have been increasing and forming new pandemic clones. CC630, CC239, D9, and D398 were important clones in this study. CC630 was a new epidemic CA clone circulating among humans, environments, and animals. CC239 was a HA-MRSA-III pandemic clone of clinical origin. The D9 clone was a livestock-associated (LA) clone, which up to now, has spread only in livestock and has not been found in humans that live in Jiangsu province. In Europe and America, there are many reports of the ST398-LA-clone in pigs and in humans who are in contact with pigs. However, various studies in China, including this one, indicate that the ST398 clone could be a CA clone rather than an LA clone. This clone also has been infecting humans for about 2 decades.

Contribution of peptidoglycan amidation to beta-lactam and lysozyme resistance in different genetic lineages of Staphylococcus aureus.

The enzymes responsible for peptidoglycan amidation in Staphylococcus aureus, MurT and GatD, were recently identified and shown to be required for optimal expression of resistance to beta-lactams, bacterial growth, and resistance to lysozyme. In this study, we analyzed the impact of peptidoglycan amidation in representative strains of the most widespread clones of methicillin resistant S. aureus (MRSA). The inhibition of the expression of murT-gatD operon resulted in different phenotypes of resistance to beta-lactams and lysozyme according to the different genetic backgrounds. Further, clonal lineages CC1 and CC398 (community-acquired MRSA [CA-MRSA]) showed a stronger dependency on MurT-GatD for resistance to beta-lactams, when compared to the impact of the impairment of the cell wall step catalyzed by MurF. In the remaining backgrounds similar phenotypes of beta-lactam resistance were observed upon the impairment of both cell-wall-related genes. Therefore, for CA-related backgrounds, the predominant beta-lactam resistance mechanism seems to involve genes associated with secondary modifications of peptidoglycan. On the other hand, the lack of glutamic acid amidation had a more substantial impact on lysozyme resistance for cells of CA-MRSA backgrounds, than for hospital-acquired MRSA (HA-MRSA). However, no significant differences were found in the resistance level of the respective peptidoglycan structure, suggesting that the lysozyme resistance mechanism involves other factors. Taken together, these results suggested that the different genetic lineages of MRSA were able to develop different molecular strategies to overcome the selective pressures experienced during evolution.

Modifying the risk: Once-a-day bathing “at risk” patients in the intensive care unit with chlorhexidine gluconate

Chlorhexidine gluconate (CHG) decreases hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) that can cause colonization and infection. A standard approach is the bathing of all patients with CHG to prevent MRSA transmission. To decrease CHG utilization, this study assessed selective daily administration of CHG bathing to intensive care unit patients who had an MRSA-positive result or a central venous catheter. This risk-based approach was associated with a 72% decrease in hospital-acquired MRSA transmission rate.

Experimental phage therapy against lethal lung-derived septicemia caused by Staphylococcus aureus in mice

Nosocomial respiratory infections caused by methicillin-resistant Staphylococcus aureus (MRSA) can progress to lethal systemic infections. Bacteriophage (phage) therapy is expected to be effective against these critical infections. Previously, phage S13′ was proposed as a potential therapeutic phage. We here examined phage treatment in a mouse model of lung-derived septicemia using phage S13′. Intraperitoneal phage administration at 6 h postinfection reduced the severity of infection and rescued the infected mice. Phage S13′ can efficiently lyse hospital-acquired MRSA strains causing pneumonia-associated bacteremia in vitro. Thus, phage therapy may be a possible therapeutic intervention in staphylococcal lung-derived septicemia.

Methicillin‐resistant Staphylococcus aureus carriage among veterinary staff and dogs in private veterinary clinics in Hokkaido, Japan

To explore the prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in veterinary medical practices, MRSA carriage was tested among 96 veterinarians (Vets), 70 veterinary technicians (VTs) and 292 dogs with which they had contact at 71 private veterinary clinics (VCs) in Hokkaido, Japan. MRSA isolates were obtained from 22 Vets [22.9%] and 7 VTs [10%]. The prevalence of MRSA among Vets was as high as that found in an academic veterinary hospital in our previous study. In contrast, only two blood donor dogs and one dog with liver disease (1.0%, 3/292) yielded MRSA. All MRSA-positive dogs were reared or treated in different VCs, in each of which at least one veterinary staff member carrying MRSA worked. Sequence types (ST) identified by multilocus sequence typing, spa types, and SCCmec types for canine MRSA isolates (ST5-spa t002-SCCmec II [from two dogs] or ST30-spa t021-SCCmec IV [from a dog]) were concordant with those from veterinary staff members in the same clinics as the MRSA-positive dogs, with which they had potentially had contact. Most MRSA isolates from veterinary staff were the same genotype (SCCmec type II and spa type t002) as a major hospital-acquired MRSA clone in Japan. The remaining MRSA was the same genotypes as domestic and foreign community-associated MRSA. Measures against MRSA infection should be provided in private VCs.

The Effect of Fluoroquinolone Use in the Respiratory Intensive Care Unit on the Development of Hospital-Acquired MRSA Infection and Its Prognosis

Methicillin-resistant Staphylococcus aureus (MRSA) which exhibits a worldwide spread, has become a serious public health problem. There are several studies indicating that there may be a relationship between the high rate of MRSA infections and long-term use of fluoroquinolones. The aim of this study was to investigate the effect of fluoroquinolone (FQ) use in the respiratory intensive care unit (ICU) on the development of the hospital-acquired MRSA infection and mortality. This was a single center experience, in which the clinical and laboratory data of the patients who were hospitalized in the respiratory ICU for two years, were retrospectively evaluated. The relationship between FQ use and the development of MRSA infection was evaluated with correlation analysis, and its relationship with the mortality was evaluated with regression analysis. A total of 302 patients were included in the study and 93 (30.7%) of them were found to be treated with FQs. Sixty-four of those 93 patients were male and the mean age was 71.1 ± 12.5 years. During the follow-up, MRSA infections developed in 11.9% (36/302) of the patients, and the rate of MRSA infection in FQ using patients was 15.1% (14/93), of them eight were ventilator-associated pneumonia (VAP) and six were secondary bacteremia. Although a positive correlation was found between FQ use and the development of MRSA infection, it was not statistically significant [P= 0.521 (Spearman), p= 0.037 (Pearson)]. In addition cut-off values for CRP and leukocyte counts, which were checked when a patient with FQ use admitted to the ICU, were determined as 7.85 mg/L and 7.650/mm3, respectively. The analysis of the relationship between CRP, leukocyte counts and the development of MRSA infection revealed a statistically significant positive relationship between high leukocyte levels (> 7.650/mm3) and the development of MRSA infection (P= 0.017, p= 0.246), but no such relationship for the CRP levels (P= 0.121, p= 0.178). The mortality rate in patients with FQ use was found as 42% (39/93), and it was determined that malignancy, history of admission to hospital in the previous six months and the presence of a hospital-acquired infection increased the risk of mortality (p= 0.020, p= 0.038 and p= 0.024, respectively). In the multivariate analysis, four independent risk factors related to the mortality in patients under FQ treatment were determined, namely malignancy (OR: 2.280, p= 0.002), re-intubation practices (OR: 4.071, p= 0.005), VAP (OR: 5.097, p= 0.009) and the use of FQ > 7 days (OR: 3.63, p= 0.003). In conclusion, our data indicated that the use of FQs in the ICU did not increase the development of hospital-acquired MRSA infection significantly, and FQ use for more than seven days was an independent risk factor for mortality. Additionally, it was thought that high leukocyte counts might be a predictive marker for the development of MRSA infection.

Prevalence and antimicrobial susceptibility pattern of methiciliin resistant Staphyllocococcus Aureus in tertiary care teaching hospital - Western India

Background: Methicillin resistant Staphylococcus aureus (MRSA) infection traditionally has been associated with healthcare settings, colonizing patients with underlying debilitating health conditions. Now a day, Hospital management has become increasingly aware of issues related to MRSA infections in the patient population. Aims & Objective: To know the prevalence of MRSA amongst hospitalized as well as OPD based patients and to find out and compare the antibiotic resistance patterns of Methicillin resistant and Methicillin sensitive S. aureus. Material and Methods: Total of 534 Staphylococcus aureus isolated from various clinical specimens using the standard procedures during June 2010 to June 2011. Screening and confirmation of MRSA isolates were done by standard methods recommended by Clinical and Laboratory Standards Institute (CLSI). CDC definition was used to classify hospital and community Acquired Methicillin-Resistant Staphylococcus aureus. Antibiotic susceptibility test was done using Kirby-Bauer disk diffusion method. Detailed information regarding duration in hospital stay, ward, unit and clinical history were collected. Results: Out of 534 Staphylococcus aureus recovered from different clinical samples, 152 (28.46%) were found to be Methicillin resistant. 113 out of 152 isolates (74.34%) were Hospital acquired MRSA (HA-MRSA) while 39 out of 152 isolates (25.66%) were Community acquired MRSA (CA-MRSA). The antibiotic susceptibility result shows that MRSA isolates were resistant to multiple antibiotics than MSSA isolates. All isolated MRSA were sensitive to Vancomycin. Conclusion: Measures to control the emergence and spread of MRSA are needed to be improved because there are fewer options available for the treatment of MRSA infections. Thus, together with good professional practice and routine infection control precautions constitute the major measures in controlling and preventing MRSA.

Comparison of antibiotic susceptibility pattern of community- and hospital-acquired methicillin-resistant Staphylococcus aureus with special reference to inducible clindamycin resistance in a tertiary care hospital in southern India

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial and community infections. Its prevalence varies markedly across different countries and among hospitals of the same country. Aims and Objectives: To estimate the prevalence of MRSA strains and investigate their antibiogram with special reference to inducible clindamycin resistance. Materials and Methods: All S. aureus isolates obtained from the clinical samples of microbiology laboratory were included in the study. All the isolates were identified by standard methods, and antimicrobial susceptibility testing was performed by Kirby Bauer disk diffusion method. Methicillin resistance was detected by combined cefoxitin and oxacillin disk diffusion method. Results were interpreted as per the Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: A total of 362 S. aureus strains were isolated, of which 36.1% (131/362) isolates were MRSA. Of these, 79.4% (104/131) were hospital-acquired MRSA (HA-MRSA) and 20.6% (27/131) were community-acquired MRSA (CA-MRSA). All the isolates were sensitive to vancomycin. Inducible clindamycin [macrolide-lincosamide-streptogramin B (iMLS B )] resistance (D test) among MRSA isolates was 12.3% (16/131). HA-MRSA isolates showed 12.5% (13/104) D test positivity, as compared to 11.2% (3/27) seen in CA-MRSA isolates. Conclusion: The reported rate of MRSA incidence is alarming. Regular surveillance of hospital-acquired infections, isolation nursing of patients who carry MRSA, monitoring of antimicrobial susceptibility pattern, and formulation of a definite antibiotic policy may be helpful.

Screening for methicillin-resistant Staphylococcus aureus carriers among individuals exposed and not exposed to the hospital environment and their antimicrobial sensitivity pattern

Aims: This study evaluated the influence of exposure to the hospital environment on methicillin-resistant Staphylococcus aureus (MRSA) carriage. The antibiograms of the MRSA isolates were examined. Materials and Methods: Nasal, throat, and web-space swabs were collected from 119 nursing students of the age group 18-23 years (exposed group) and 100 age-matched pharmacy students (nonexposed group). S. aureus was identified and antibiogram obtained as per Clinical and Laboratory Standards Institute (CLSI) guidelines. MRSA was detected by cefoxitin disc diffusion test and by growth on oxacillin screen agar as per CLSI guidelines. The presence of the mecA gene was confirmed by conventional polymerase chain reaction. Results: The MRSA carrier rates were 11.8% and 4% in the exposed and nonexposed groups, respectively. Association of exposure to the hospital environment with MRSA colonization was statistically significant. All MRSA isolates showed sensitivity to netilmicin, linezolid, tetracycline, vancomycin and teicoplanin. Among the exposed group, 71.4% MRSA isolates were resistant to ciprofloxacin, 64.3% to cotrimoxazole, 64.3% to erythromycin, 28.6% to gentamicin and 21.4% to clindamycin. Among the nonexposed group, 75% MRSA isolates were resistant to ciprofloxacin, 25% to cotrimoxazole, 25% to erythromycin, 25% to gentamicin and 25% to clindamycin. Conclusion: Exposure to the hospital environment was found to be a significant risk factor for MRSA carriage. Hospital-acquired MRSA (HA-MRSA) isolates showed greater resistance toward antimicrobials compared with community-acquired MRSA (CA-MRSA) isolates. This highlights the need for the appropriate institution of pharmacotherapy in cases of HA-MRSA and CA-MRSA infections and control of transmission by carriers.

Mupirocin resistant staphylococcus aureus nasal colonization among healthcare workers.

Mupirocin resistant staphylococcus aureus nasal colonization among healthcare workers.

Perioperative Skin Preparation

Liaison: Anthony T Tokarski BS Leaders: David Blaha MD (US), Michael A. Mont MD (US), Parag Sancheti MS, DNB, MCh (International) Delegates: Lyssette Cardona MD, MPH, MHA, AAHIVS, FIDSA, Gilberto Lara Cotacio MD, Mark Froimson MD, Bhaveen Kapadia MD, James Kuderna MD, PhD, Juan Carlos Lopez MD, Wadih Y Matar MD, MSc, FRCSC, Joseph McCarthy MD, Rhidian Morgan-Jones MB BCh, FRCS, Michael Patzakis MD, Ran Schwarzkopf MD, Gholam Hossain Shahcheraghi MD, Xifu Shang MD, Petri Virolainen MD, PhD, Montri D. Wongworawat MD, Adolph Yates Jr, MD

Community-Associated Methicillin-ResistantStaphylococcus aureusin a Pediatric Emergency Department in Newfoundland and Labrador

First-generation cephalosporins and antistaphylococcal penicillins are typically the first choice for treating skin and soft tissue infections (SSTI), but are not effective for infections caused by methicillin-resistant Staphylococcus aureus (MRSA). It is currently unclear what percentage of SSTIs is caused by community-associated MRSA in different regions in Canada. To determine the incidence of MRSA in children presenting to a pediatric emergency department with SSTI, and to determine which antibiotics were used to treat these infections. All visits to a pediatric emergency department were reviewed from April 15, 2010 to April 14, 2011. Diagnoses of cellulitis, abscess, impetigo, folliculitis and skin infection (not otherwise specified) were reviewed in detail to determine whether a culture was taken and which antibiotic was prescribed. There were 367 cases of SSTI diagnosed over the study period. Forty-five (12.3%) patients had lesions that were swabbed for culture and sensitivity. S aureus was the most common organism found, with 14 (66%) methicillin-sensitive cases and seven (33%) methicillin-resistant cases. Of the seven cases of MRSA identified, only one patient had clear risk factors for hospital-acquired MRSA. First-generation cephalosporins were initially prescribed for 280 (76%) patients. The overall incidence of MRSA in the population presenting to a pediatric emergency department in Newfoundland and Labrador appeared to be low, although only a small percentage of infections were cultured. At this time, there appears to be no need to change empirical antibiotic coverage, which remains a first-generation cephalosporin.

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Introduction: Major Operating room procedures (MORP) are frequently performed in hospitalized patients for a variety of causes and are associated with significant morbidity and mortality. Hospital-Acquired Methicillin Resistant Staphylococcus Aureus (HA-MRSA) is associated with severe and invasive disease, longer hospital stays, higher mortality, and higher healthcare costs. MRSA infection rates in hospitalized surgical patients and outcomes vary widely among reported single center studies. Methods: A retrospective analysis of the Nationwide Inpatient Sample (NIS) for the years 2009 and 2010 was used for the current study. The NIS is the largest all-payer hospital discharge database in the United States that is a part of the Healthcare Cost and Utilization Project sponsored by the Agency for Healthcare Research and Quality. All hospitalizations that underwent a MORP were selected for analysis. Occurrence of MRSA infection (ICD-9-CM code of 041.12), MRSA septicemia (038.12), and MRSA pneumonia (482.42) were identified from secondary diagnoses fields. Carrier/suspected carrier status of MRSA and personal history of MRSA were also identified. Patient and hospital-level factors associated with occurrence of MRSA were identified by a multivariable logistic regression model. Association between MRSA and outcomes including hospital length of stay (LOS) and in-hospital mortality (IHM) were examined by multivariable linear and logistic regression models respectively. Results: During the study period a total of 22,932,947 hospitalizations had an MORP. Among these, 0.84% had MRSA infection, 0.09% had MRSA septicemia, and 0.10% had methicillin resistant pneumonia due to staphylococcus aureus. MRSA was present in 1.03% of all hospitalizations that had a MORP. Carrier/suspected status of MRSA was present in 0.27% of all hospitalizations that had an MORP and personal history of MRSA was found in 0.19% of all hospitalizations. Amongst those that had at least one type of MRSA infection (n=235,636 hospitalizations), carrier/suspected MRSA status was present in 1.7% and personal history of MRSA was found in 2.9%. Those with MRSA had a higher co-morbid burden (mean of 3.1 co-morbid conditions) compared to those who did not have MRSA (mean of 1.6 conditions). The mean hospital LOS among those with MRSA was 14 days (5 days for those without MRSA). Hospital mortality rate for patients with MRSA was 3.7% (1.2% for those without MRSA). Factors that were associated with a significantly (p<0.05) higher odds for occurrence of MRSA event included female sex, race (black and native Americans compared to whites), emergency/urgent admission, increased co-morbid burden, uninsured patients, non-teaching hospitals, and small/medium hospitals (number of beds). Following adjustment for all other patient and hospital level confounding factors, occurrence of an MRSA event was associated with significantly longer hospital LOS (estimate is 0.68, p<0.01) and higher odds of IHM (OR=1.39, 95% CI=1.30 – 1.48, p<0.01) Conclusions: In this large retrospective study, hospitalized patients who underwent a major operating room procedure and developed an MRSA infection had a higher risk of mortality and increased hospital resource utilization. Certain predictors of MRSA infection are identified.

Emergence of methicillin resistance and Panton‐Valentine leukocidin positivity in hospital‐ and community‐acquired Staphylococcus aureus infections in Beira, Mozambique

The objective of this study was to investigate the antibiotic resistance patterns, including methicillin resistance, inducible macrolide-lincosamide-streptogramin B (MLSB ) resistance and Panton-Valentine leukocidin (PVL) toxin gene carriage among hospital-acquired Staphylococcus aureus (HA-SA) and community-acquired S. aureus (CA-SA), in Beira, Mozambique. In 2010-2011, two prospective surveillance studies were conducted on post-operative and burn wound infections at the Central Hospital of Beira and on skin and soft tissue abscesses at the São Lucas Health Centre. We cultured pus samples, identified suspected S. aureus isolates and performed antimicrobial susceptibility testing, including detection of MLSB resistance. Real-time polymerase chain reaction was used to detect mecA, Martineau and PVL genes. The prevalence of hospital-acquired methicillin-resistant S. aureus (HA-MRSA) infection among 53 inpatients was 15.1%; the prevalence of community-acquired methicillin-resistant S. aureus (CA-MRSA) infection among 100 outpatients was 1.0%. Inducible MLSB resistance was present in 41.7% and 10.7% of HA-SA and CA-SA isolates, respectively. PVL toxin gene was detected in 81.1% of methicillin-susceptible S. aureus (MSSA) compared with 11.1% of methicillin-resistant S. aureus. Our study shows, for the first time in Mozambique, the emergence of HA-MRSA. The prevalence of CA-MRSA was low, whereas the rate of PVL toxin gene carriage in MSSA was high. The high rate of inducible MLSB resistance indicates the importance of performing routine D-tests. Overall, our results show the need of strengthening laboratory facilities to provide microbiological data for both directed therapy and surveillance.

Contamination of Public Buses with MRSA in Lisbon, Portugal: A Possible Transmission Route of Major MRSA Clones within the Community

In a previous study we have shown that public buses in Oporto, the second largest city in Portugal, were highly contaminated with MRSA. Here we describe the results of a similar study performed in another urban area of Portugal–Lisbon, the capital. Between May 2011 and May 2012, hand touched surfaces of 199 public buses in Lisbon were screened for MRSA contamination. Subsequently, the hands of 575 passengers who frequently use these bus lines were also screened. All hand carriers of MRSA were further screened for nasal carriage. The isolates were characterized by PFGE, staphylococcal cassette chromosome (SCC) mec typing, spa typing, MLST and were tested for the presence of mecA, Panton-Valentine leukocidin and arginine catabolic mobile element genes. MRSA contamination was shown in 72 buses (36.2%). The majority of the isolates belonged to three major clones: Clone A was identified as EMRSA-15 defined by pattern PFGE A, spa types t2357/t747/t025/t379/t910, ST22, and SCCmec IVh (n = 21; 29%). Clone B was the New York/Japan clone characterized by PFGE B-t002/t10682-ST5-II (n = 15; 21%). Clone C included isolates with characteristics of the international community-acquired USA300 or related clones, PFGE C-t008-ST8-IVa/IVc/IVg/IVnt/VI (n = 19; 26%). The first two clones are currently the two major lineages circulating in Portuguese hospitals. The hands of 15 individuals were contaminated with MRSA belonging to the nosocomial clones A or B. Eleven of these individuals were not nasal carriers of MRSA and all but one had travelled by public transportation, namely by bus, prior to sampling. In conclusion, public buses in two major cities in Portugal are often contaminated with MRSA representing clones dominant in hospitals in the particular geographic area. MRSA contamination of public transport and the transfer of the bacteria to the hands of passengers may represent a route through which hospital-acquired MRSA clones may spread to the community.

Characterization of PVL-positive MRSA from Norway

Norway is a country in which the Methicillin-resistant Staphylococcus aureus (MRSA) prevalence has been low for the last decades. There are virtually no epidemic, hospital-acquired MRSA because of an emphasis on strict infection control rules and restrictive use of antibiotics. However, community-acquired and/or Panton-Valentine leucocidin (PVL)-positive MRSA need to be monitored as these strains are transmitted outside of healthcare facilities and cannot be contained by healthcare-centred strategies. All 179 non-repetitive isolates of PVL-positive MRSA that were received during 2011 at the regional infection control laboratory at Akershus University Hospital were preserved and spa typed. Seventy isolates were further characterized by DNA microarray hybridization. The most common PVL-MRSA lineages were ST8-MRSA-IV and CC30-MRSA-IV. Further common clones were CC80-MRSA-IV and CC5-MRSA-IV. Other clones were found sporadically. These included ST772-MRSA-V and ST834-MRSA-IV, the latter in patients with epidemiological connections to the Philippines. Small-scale family outbreaks affecting at least 49 individuals were noted, with numbers of known cases per outbreak ranging from two to seven. At least 24 cases were related to foreign travel to Eritrea, India, Iraq, Macedonia, Pakistan, the Philippines, Poland, Singapore, Turkey, the USA and Vietnam. These data show that community-acquired/PVL-positive MRSA are not yet a major public health problem in Southern Norway. Our study corroborates the current practice of mandatory screening of patients and staff with travel histories, admissions or employment in healthcare institutions outside the Scandinavian countries or with known MRSA contacts.

Characterization of SCCmectypes, antibiotic resistance, and toxin gene profiles ofStaphylococcus aureusstrains

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious nosocomial and community acquired infections. Resistance to methicillin is mediated by the mecA gene, which is inserted in a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). We determined the SCCmec types, the occurrence of genes encoding toxic shock syndrome toxin (tst), exfoliative toxin (eta, etb), Panton-Valentine leukocidin (pvl) as well as antibiotic susceptibility of these isolates. Among 65 hospital-acquired methicillin-resistant S. aureus (HA-MRSA) strains, SCCmec types II, III and IV were identified. Type III SCCmec was the most prevalent (62%), followed by mec types II (24%) and IV (14%). Four community acquired methicillin-resistant S. aureus (CA-MRSA) strains carried SCCmec type IV and were pvl-positive. The most prevalent gene among HA-MRSA was pvl. The toxic shock syndrome toxin and exfoliative toxin genes were found only in hospital-acquired methicillin-resistant S. aureus. The results of this study demonstrate that the SCCmec type III is predominant among strains recovered from hospitalized patients with infections and that these strains were resistant to many antibiotics used in the treatment of staphylococcal infections.

Evaluation of the in vitro activity of ceftaroline and its potential against a collection of hospital-acquired methicillin-resistant S.aureus and hospital-acquired methicillin-susceptible S.aureus isolates recovered from various clinical samples

Aim of the study was the evaluation of the in vitro activity of ceftaroline and its potential against a collection of Hospital-Acquired Methicillin-Resistant Staphylococcus aureus (HA-MRSA) and Hospital-Acquired Methicillin-Susceptible S. aureus (HA-MSSA) isolates. S. aureus isolates from outpatients were also examined. A total of 30 MSSA and 50 MRSA strains were studied.The isolates were collected during a four-year period (2006-2010) from the Pavia area (North-West of Italy). MICs and MBCs were performed in duplicate by broth dilution method (EUCAST 2012). Susceptibility category assessments for ceftaroline was made using EUCAST 2013 breakpoints. MICs of the antibiotics included in MicroScan Pos Breakpoint Combo Type 32 Panels (Siemens) were also evaluated. Genotyping was performed by PFGE. Ceftaroline MIC values for MSSA strains ranged from 0.06 mg/L to 0.5 mg/L and from 0.125 mg/L to 2 mg/L for MRSA strains, of which 4/50 exhibited a MIC value of 2 mg/L. The MIC value of these 4 isolates was confirmed by macromethod. Two out of four, clonally related, belonged to hVISA category. Furthermore, MIC50 and MIC90 were evaluated: MSSA MIC50 value was 0.125 mg/L, while MIC90 was 0.25 mg/L; MIC50 and MIC90 values of the MRSA were 0.5 mg/L and 1 mg/L, respectively. Finally, the bactericidal activity of this molecule was investigated by MBC method. Ceftaroline MIC and MBC values coincided in 96.25% of cases, only in 3 cases the MBC value was one dilution higher than MIC value. Ceftaroline demonstrated bactericidal activity against a large number of S. aureus, included MRSA and hVISA.

Epidemiological and molecular characterization of community and hospital acquired Staphylococcus aureus strains prevailing in Shenyang, Northeastern China

In order to obtain adequate information for the treatment of methicillin resistant Staphylococcus aureus (MRSA) infections, it is crucial to identify trends in epidemiological and antimicrobial resistance patterns of local S. aureus strains. Community and hospital acquired S. aureus isolates (n=202) were characterized using staphylococcal cassette chromosome mec (SCCmec) typing, pulse field gel electrophoresis (PFGE) analysis, spa typing and minimal inhibitory concentration (MIC) determination. The prevalence of the Panton-Valentine leukocidine (pvl) and several antibiotic resistance genes among the isolates were also detected by PCR. All of the S. aureus isolates were susceptible to vancomycin, daptomycin and linezolid. Three hospital isolates were resistant to teicoplanin while 14 showed intermediate resistance to teicoplanin. The resistance patterns of community-acquired MRSA (CA-MRSA) isolates to other antimicrobials were similar to those of hospital-acquired MRSA (HA-MRSA) isolates except for clindamycin and gentamicin. There was excellent correlation between phenotypes and genotypes in the determination of S. aureus resistance to erythromycin, gentamicin, and tetracycline. The SCCmec type II and SCCmec type IV were the predominant types detected in hospital and community isolates, respectively. The most frequently encountered spa types were t002 and t030 both in HA- and CA-MRSA isolates. Pulsotype A was the most predominant pulsotype identified among the isolates tested, followed by pulsotype B. Seventy-two hospital isolates (19 HA-MRSA and 53 HA-MSSA) and 10 CA-MRSA were positive for the pvl gene. This study shows that the combination of susceptibility testing and various molecular methods has provided useful information on the antibiotic resistance and molecular diversity of S. aureus in a specific region of China. The high proportion of pvl positive MSSA and MRSA isolates observed in this study indicates that adequate measures are needed to curtail the spread of those MRSA and MSSA clones prevailing both in hospital and the community.