Clonal clusters and virulence factors of methicillin-resistant Staphylococcus Aureus: Evidence for community-acquired methicillin-resistant Staphylococcus Aureus infiltration into hospital settings in Chennai, South India

Background and Objective: Staphylococcus aureus is one of the major pathogens of nosocomial infections as wells as community-acquired (CA) infections worldwide. So far, large-scale comprehensive molecular and epidemiological characterisation of S. aureus from very diverse settings has not been carried out in India. The objective of this study is to evaluate the molecular, epidemiological and virulence characteristics of S. aureus in both community and hospital settings in Chennai, southern India. Methods: S. aureus isolates were obtained from four different groups (a) healthy individuals from closed community settings, (b) inpatients from hospitals, (c) outpatients from hospitals, representing isolates of hospital–community interface and (d) HIV-infected patients to define isolates associated with the immunocompromised. Antibiotic susceptibility testing, multiplex polymerase chain reactions for detection of virulence and resistance determinants, molecular typing including Staphylococcal cassette chromosome mec (SCCmec) and agr typing, were carried out. Sequencing-based typing was done using spa and multilocus sequence typing (MLST) methods. Clonal complexes (CC) of hospital and CA methicillin-resistant S. aureus (MRSA) were identified and compared for virulence and resistance. Results and Conclusion: A total of 769 isolates of S. aureus isolates were studied. The prevalence of MRSA was found to be 7.17%, 81.67%, 58.33% and 22.85% for groups a, b, c and d, respectively. Of the four SCCmec types (I, III, IV and V) detected, SCCmec V was found to be predominant. Panton-Valentine leucocidin toxin genes were detected among MRSA isolates harbouring SCCmec IV and V. A total of 78 spa types were detected, t657 being the most prevalent. 13 MLST types belonging to 9 CC were detected. CC1 (ST-772, ST-1) and CC8 (ST238, ST368 and ST1208) were found to be predominant among MRSA. CA-MRSA isolates with SCCmec IV and V were isolated from all study groups including hospitalised patients and were found to be similar by molecular tools. This shows that CA MRSA has probably infiltrated into the hospital settings.

Molecular characterisation of Panton–Valentine leucocidin‑producing methicillin‑resistant Staphylococcus aureus clones isolated from the main hospitals in Taif, KSA.

Introduction: Panton–Valentine leucocidin (PVL) is a bicomponent pore‑forming cytolytic toxin encoded by the lukF‑PV and lukS‑PV genes. Community‑acquired methicillin‑resistant Staphylococcus aureus (CA‑MRSA) may carry the pvl genes which may be related to increased disease severity. This study aimed to characterise the PVL‑producing MRSA recovered from different Taif Hospitals, Saudi Arabia. Methods: The study included 45 hospital‑acquired‑MRSA (HA‑MRSA) and 26 CA‑MRSA strains which were identified from 445 S. aureus strains isolated from different clinical samples. MRSA strains were identified by standard oxacillin salt agar screening procedure and by the detection of the mecA gene by the polymerase chain reaction (PCR). Detection of the S. aureus‑specific femA, mecA and pvl genes was performed by multiplex PCR. PCR‑restriction fragment length polymorphism (PCR‑RFLP) analysis was done for coagulase (coa) gene. Results: The staphylococcal cassette chromosome mec types of the 45 HA‑MRSA strains were Type I (n = 24), Type II (n = 7) and Type III (n = 14) whereas the 26 CA‑MRSA strains were Type IV (n = 14), Type V (n = 11) and one isolate was non‑typeable. All the HA‑MRSA and six CA‑MRSA strains were PVL‑negative PCR‑RFLP analysis of coa gene showed that PVL‑positive MRSA (n = 20) isolates showed six different patterns, and five patterns were shared by PVL‑positive methicillin‑susceptible S. aureus (MSSA). The eighth pattern was the most frequent in both MRSA and MSSA. Conclusion: PVL is more frequent among CA‑MRSA than MSSA. All the HA‑MRSA and 25% of CA‑MRSA strains were negative for PVL. The pvl gene was related to the severity of infection but not related to coa gene RFLP pattern.

The changing face of community-acquired methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, both in hospitalised patients with significant healthcare exposure and in patients without healthcare risk factors. Community-acquired methicillinresistant S. aureus (CA-MRSA) are known for their rapid community transmission and propensity to cause aggressive skin and soft tissue infections and community-acquired pneumonia. The distinction between the healthcare-associated (HA)-MRSA and CA-MRSA is gradually fading owing to the acquisition of multiple virulence factors and genetic elements. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community or HA status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacotherapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-β-lactam antibacterial agents. This review aimed at illuminating the characteristic features of CA-MRSA, virulence factors, changing clinical settings and molecular epidemiology, insurgence into the hospital settings and therapy with drug resistance.

SCCmec genotyping and antimicrobial susceptibility of community-ac-quired methicillin-resistant Staphylococcus aureus / 中国感染控制杂志

Objective To investigate the types of staphylococcal cassette chromosome mec (SCCmec)gene and an-timicrobial resistance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA)isolated from outpatients and inpatients in a hospital.Methods MRSA strains isolated between May 2011 and August 2015 in a hospi-tal and the relevant case data were collected,polymerase chain reaction(PCR)method was used to identify mecA gene of MRSA and SCCmec gene of CA-MRSA,antimicrobial susceptibility testing of CA-MRSA were performed and analyzed. Results A total of 305 MRSA isolates were collected,296 of which were mecA positive,29.73% (88/296)were CA-MR-SA. The genotyping of CA-MRSA showed that 48 strains were SCCmec type Ⅳ,36 were SCCmec type V,the other 4 strains were undefined. Antimicrobial susceptibility testing results showed that susceptibility rates of CA-MRSA to vanco-mycin,linezolid,and tigecycline were all 100% ,resistance rates to penicillin and oxacillin were both 100% ;resistance rates of SCCmec type IV and SCCmec type V CA-MRSA strains to levofloxacin,rifampicin,and ciprofloxacin were all signifi-cantly different (all P58% .Conclusion The main SCCmec type of CA-MRSA are type IV and type V in this hospital,antimicrobial resistance rate is high,clinicians should pay high attention,and use antimicrobial agents according to antimicrobial susceptibility testing results.

Estudio descriptivo de infecciones osteo-articulares en niños en tiempos de Staphylococcus aureus resistente a meticilina de la comunidad (SARM-Co) / Descriptive study of bone and joint infections in children in times of community-acquired methicillin- resistant Staphylococcus aureus (CA-MRSA)

Background: Bone and joint infections (BJI) are relatively common in children, and community -acquired methicillin resistant Staphylococcus aureus (CA-MRSA) is the leading cause in some countries. Aim: To evaluate epidemiological data, clinical and microbiological features and outcome of BJI. Methods: A prospective descriptive study was conducted. Results: 40 patients (p) completed the study. Bacterial cultures were positives in 30 p (75%): CA-MRSA was found in 19 p, methicillin-sensitive S. aureus in 6 p, and others in 5 p. Cultures were negatives in 10 p (25%). Median treatment duration was 28 days (r: 21-40 d); Analyzing patients with CA-MRSA positive cultures separately, initial CRP was higher (Md 76 vs 50 mg/L, p < 0.02), normalization occurred later (Md 14 days vs 7days, p < 0.03), and duration of treatment (Md 32 days vs 23, p < 0.004) as well as hospital stay (Md 9 days vs 7, p = 0.12) were longer. Sequelae were present in 3 p and 1 relapsed: All of them with CA-SAMR. Conclusion: CA-MRSA was the leading cause of BJI and was associated with higher CRP on admission, later normalization and longer treatment duration. Complications as drainage requirement, and sequelae were common in those p.

Introducción: Las infecciones osteo-articulares (IOA) son relativamente comunes en los niños, siendo la infección por Staphylococcus aureus resistente a meticilina de la comunidad (SARM-Co) una de las más frecuentes. Objetivo: Evaluar los datos epidemiológicos, características clínicas, microbiológicas y de evolución en niños con IOA. Métodos: Estudio descriptivo prospectivo. Resultados: Se incluyeron 40 pacientes (p). Los cultivos fueron positivos en 30 p (75%). Se aisló SARM-Co en 19 p; S. aureus sensible a meticilina en 6 p; otros microorganismos en 5 p. La duración del tratamiento fue de 28 días Md (r: 21-40 d). En los p con cultivos positivos para SARM-Co, la PCR inicial fue mayor (Md 76 vs 50 mg/L, p < 0,02), la normalización se produjo después (Md 14 días vs 7 días, p < 0,03) y la duración del tratamiento (Md 32 días vs 23, p < 0,004), así como la estancia hospitalaria (Md 9 días vs 7, p = 0,12) fueron más prolongados. En la evolución 1 p recayó y 3 tuvieron secuelas; en todos se aisló SARM-Co. Conclusión: SARM-Co fue la causa más frecuente de las IOA y se asoció con mayor valor de PCR al ingreso, normalización tardía, mayor duración del tratamiento, y complicaciones.

Staphylococcus aureus nasal carriage among outpatients attending primary health care centers: a comparative study of two cities in Saudi Arabia and Egypt

Epidemiological and molecular data on community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are still scarce in both Egypt and Saudi Arabia. There is almost no data regarding methicillin resistant Staphylococcus aureus (MRSA) prevalence in both countries. This study was conducted to investigate the prevalence and molecular epidemiology of S. aureus and MRSA nasal carriage among outpatients attending primary health care centers in two big cities in both countries. A total of 206 nasal swabs were obtained, 103 swabs from each country. S. aureus isolates were characterized by antibiotic susceptibility, presence of mecA and PVL genes, SCCmec-typing and spa typing, the corresponding Multi locus sequence typing clonal complex was assigned for each spa type based on Ridom StaphType database. MRSA was detected in 32% of the Egyptian outpatients while it was found in 25% of the Saudi Arabian outpatients. All MRSA isolates belonged to SCCmec type V and IVa, where some isolates in Saudi Arabia remained nontypeable. Surprisingly PVL+ isolates were low in frequency: 15% of MRSA Egyptian isolates and 12% of MRSA isolates in Saudi Arabia. Two novel spa types were detected t11839 in Egypt, and t11841 in Saudi Arabia. We found 8 spa types among 20 isolates from Egypt, and 12 spa types out of 15 isolates from Saudi Arabia. Only two spa types t008 and t223 coexisted in both countries. Four clonal complexes (CC5, CC8, CC22, and CC80) were identified in both Egypt and Saudi Arabia. However, the data collected lacked a representation of isolates from different parts of each country as only one health center from each country was included, it still partially illustrates the CA-MRSA situation in both countries. In conclusion a set of control measures is required to prevent further increase in MRSA prevalence.

Prevalence and invasiveness of community-acquired methicillin-resistant Staphylococcus aureus: A meta-analysis.

Background: Reports suggest that the prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has increased, and that CA-MRSA is more virulent than healthcare-associated (HA)-MRSA. Aims: The aim of this study is to gain a better understanding of the invasiveness and prevalence of CA-MRSA in patients; we systematically reviewed the literature by conducting a meta-analysis. Materials and Methods: We searched the MEDLINE and PUBMED databases from the year these databases were established to January 2013. Results: The pooled CA-MRSA prevalence among 50,737 patients from 33 studies was 39.0% (range, 30.8-47.8%). The pooled CA-MRSA prevalence rates among pediatric and adult patients with MRSA infection were 50.2% (range, 37.5-62.8%) and 42.3% (range, 16.4-73.3%), respectively. The pooled CA-MRSA prevalence rates of MRSA-infected patients in Asia, Europe, and North America were 23.1% (range, 12.0-39.8%), 37.4% (range, 21.1-56.4%), and 47.4% (range, 35.8-59.4%), respectively. Using the random effects model, we determined that the pooled odds ratio of invasive infections in CA- and HA-MRSA was 0.30 (95% confidence interval: 0.08-1.10; P = 0.07, test for heterogeneity P < 0.00001). Conclusions: The prevalence of CA-MRSA in MRSA infection varied with area and population. No difference in the ability to cause invasive infections was found between CA- and HA-MRSA. This finding challenges the view that CA-MRSA is more virulent than HA-MRSA.

Infección por Staphyloccus aureus resistente a la meticillina adquirido en la comunidad (SAMR-AC) / Community-acquired methicillin-resistant Staphylococcus aureus infection (CA-MRSA)

Se presenta un paciente de 1 año de edad con antecedentes de salud, que desarrolló infección estafilocócica de piel y partes blandas, que lo llevó al desarrollo de shock tóxico, disfunción múltiple de órganos y muerte. Se aisló en cultivo de tejido pulmonar posmorten cepa de Staphylococcus aureus resistente a la meticillina, productor de la toxina Panton-Valantine leucocidina demostrado por caracterización molecular. Se estableció el diagnóstico anatomopatológico de sepsis generaliza y bronconeumonía necrosante bilateral.

A one-year old patient with history of health problems, who developed Staphylococcus aureus-caused infection in the skin and soft tissues that led him to toxic shock, multiple organ failure and death. Methilline-resistant Staphylococcus aureus strain was isolated in pulmonary tissue culture after death. This strain produced Panton-Valantine toxin called leukocidin as proved in molecular characterization. There was established the anatomic-pathological diagnosis of generalized sepsis and bilateral necrosing bronchopneumonia.

Embolia pulmonar séptica de origen cutáneo / Septic pulmonary embolism of cutaneous origin

La embolia pulmonar séptica es una enfermedad grave y poco frecuente que se caracteriza por presentar infiltrados pulmonares bilaterales asociados a un foco infeccioso extrapulmonar. Se relaciona principalmente a endocarditis derecha, tromboflebitis pelviana, accesos vasculares y menos frecuentemente a infecciones profundas como osteomielitis, artritis séptica o piomiositis. El Staphylococcus aureus meticilino-resistente adquirido en la comunidad (SAMR-AC) es un patógeno emergente, con alta virulencia y de rápida propagación, que afecta a sujetos sin enfermedades previas relacionadas o factores de riesgo conocidos. Causa infecciones de piel y partes blandas y con menor frecuencia infecciones graves como fascitis necrotizante, artritis séptica, osteomielitis, piomiositis y neumonía necrotizante. Su epidemiología, patogenia y manifestaciones clínicas difieren de las causadas por el SAMR adquirido en el hospital. Presentamos el caso de un varón de 67 años con embolias pulmonares sépticas causadas por SAMR-AC con origen en una infección cutánea.

Septic pulmonary embolism is a serious and rare illness characterized by pulmonary infiltrates associated with an extrapulmonary infectious focus. It is mainly related to right-sided endocarditis, pelvic thrombophlebitis, vascular access and less frequently to deep infections such as osteomyelitis, septic arthritis and pyomyositis. The community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen with high virulence and rapid spread involving subjects without previous related diseases or known risk factors. It causes infections of skin and soft tissue and less frequently other serious infections such as necrotizing fascitits, septic arthritis, osteomyelitis, pyomyositis and necrotizing pneumonia. Epidemiologically, pathogenesis and clinical manifestations differ from those caused by MRSA acquired in the hospital. We present the case of a 67 year-old male with septic pulmonary embolism caused by community acquired MRSA that started with a skin infection.

Advances of community-acquired methicillin-resistant Staphylococcus aureus / 国际儿科学杂志

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major pathogens of the hospital infection.Its clinical features and drug-resisetance situations have always been concerned.But since the late 1990s,another class of MRSA has become a major concern worldwide as an emerging pathogen in the community.This new class of MRSA is called community-acquired MRSA (CA-MRSA).With the rapid development of the infection of CA-MRSA in 20 years,especially in the latest 3 years,CA-MRSA may be replacing the hospital-acquired MRSA strains(HA-MRSA) as one of the major pathogens in the hospital and the community as well.The characteristics of CA-MRSA are very different from those of HA-MRSA.This review summarizes the current studies of CA-MRSA on the epidemiology and the molecular characteristics.

Distribution of Staphylococcus aureus strains colonized in healthy community population and molecular epidemiological characteristics for MRSA strains / 中华流行病学杂志

Objective To investigate the nasal colonization of Staphylococcus (S.) aureus strains among medical university students in Shenyang and to study the molecular epidemiological characteristics of methicillin resistant S. aureus (MRSA) strains. Methods Sterilized nasal swabs were used to collect nasal bacteria from both nares of the students. Nasal specimens were further identified as S. aureus strains, sensitive or resistant to methicillin through a series of tests. Molecular related methods including staphylococcal cassette chromosome mec (SCCmec) typing, pulsed- field gel electrophoresis (PFGE) , coagulase isotyping and minimum inhibitory concentration (MIC) determination etc. were used to characterize the isolates. Prevalence of the panton-valentine leukocidin (pvl) genes (lukS and F-PV) among the isolates was also assessed. Results Staphylococci were found in 488 specimens from 977 participants through the surveillance program, conducted in 2009. Of the 488 specimens being tested, 364 were identified as coagulase-negative staphylococci (CoNS) and 124 as S. aureus. MRSA strain among the S. aureus isolates was accounted for 3.4%. In the surveillance program conducted in 2010, staphylococci grew in 310 specimens fiom 657 participants. Of the 310 specimens tested, 195 were identified as CoNS and 115 as S. aureus. The percentage of MRSA strains among the S. aureus isolates was 7.7%. In total, 239 students carried S.aureus, and the percentage of MRSA carriers among the total specimens tested in this study was 5.1%.Most of the MRSA strains could be classified into one of the five types of SCCmec elements. Type Ⅳ a SCCmec strains were most frequent seen overall (10 isolates). A total of 11 pulsotypes were identified among the MRSA strains and were classified into 7 major groups (A to G) by the mutual correlations of their banding patterns. Ten MRSA strains were identified as pvl positive strains. Conclusion An MRSA clone (Ⅳ a SCCmec pulsotype A) carrying pvl toxin gene was found to be prevalent in the nares of the healthy university students.

Methicillin/Oxacillin-resistant Staphylococcus aureus as a hospital and public health threat in Brazil

Methicillin-resistant Staphylococcus aureus is an established nosocomial pathogen (HA-MRSA, hospital acquired MRSA), but has recently begun to appear in the community (CA-MRSA, community acquired MRSA). The cause of resistance to methicillin and all other â-lactam antibiotics is the mecA gene, which is situated on a mobile genetic element, the Staphylococcal Cassette Chromosome mec (SCCmec). Seven major variants of SCCmec, type I to VII are distinguished. HA-MRSA disseminated worldwide and causes the majority of S. aureus nosocomial infections with a limited number of clones disseminated including the Brazilian Epidemic Clone (BEC, ST239-MRSA-III). CA-MRSA isolates are susceptible to non-â-lactam antibiotics, usually isolated from healthy individuals which do not possess any unknown risk factors for MRSA infection and are associated with a larger clonal diversity compared with HA-MRSA. However, during recent years distinction between HA-MRSA and CA-MRSA is beginning to fade. Actually, knowledge about MRSA disseminating clones is required to implement any strategies to control the transmission of MRSA either within hospitals or in community. For this reason, rapid identification of strains is an important issue. The rate of HA-MRSA can be reduced substantially through the implementation of interventions strategies, even in settings where MRSA is endemic as in most Brazilian hospitals. However, these policies could be quite complicated in the light of an increasing CA-MRSA prevalence in healthcare facilities, considering that distinction between HA-MRSA and CA-MRSA has started to disappear.

A Case of Acute Pyelonephritis Caused by Community Acquired Methicillin-Resistant Staphylococcus aureus

In the past decade, methicillin-resistant staphylococcus aureus (MRSA) have emerged in the community, causing serious infection in young and healthy persons without established risk factors for MRSA acquisition. This community acquired methicillin- resistant S. aureus (CA-MRSA) has been usually reported to cause the skin and soft tissue infection and necrotizing pneumonia. We have experienced a case of acute pyelonephritis caused by CA-MRSA without health care-associated risk factors. The staphylococcal cassette chromosome mec (SCCmec) typing and multilocus sequence typing (MLST) revealed the ST5- MRSA-IV clone, which showed SCCmec type IV and MLST allelic profile of ST5 (1-4-1-4-12-1-10).

A Case of Acute Pyelonephritis Caused by Community Acquired Methicillin-Resistant Staphylococcus aureus

In the past decade, methicillin-resistant staphylococcus aureus (MRSA) have emerged in the community, causing serious infection in young and healthy persons without established risk factors for MRSA acquisition. This community acquired methicillin- resistant S. aureus (CA-MRSA) has been usually reported to cause the skin and soft tissue infection and necrotizing pneumonia. We have experienced a case of acute pyelonephritis caused by CA-MRSA without health care-associated risk factors. The staphylococcal cassette chromosome mec (SCCmec) typing and multilocus sequence typing (MLST) revealed the ST5- MRSA-IV clone, which showed SCCmec type IV and MLST allelic profile of ST5 (1-4-1-4-12-1-10).