Molecular Characterization of Staphylococcal Cassette Chromosome mec types I to V in Methicillin-resistant Staphylococcus aureus by Multiplex PCR

Objective To investigate molecular types and drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) in Zhejiang province. Methods One hundred and fourty-seven clinical MRSA isolates were collected from 11 grade A tertiary hospitals during January 2009 and December 2010 in Zhejiang province. Minimal inhibitory concentrations (MICs) of 13 antimicrobial agents were determined by agar dilution. Multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing and spa typing were used to examine the homology of the strains, and drug resistance patterns were compared among different molecular types. Simpson index was used to determine the discriminatory power of three typing methods. Results Fourteen STs were identified in 147 MRSA isolates, of which ST239 (75 isolates), ST5 (24 isolates) and ST59 (23 isolates) were the most prevalent clones. Four SCCmec types (types Ⅱ to Ⅴ) were identified in 141 isolates, and 6 isolates were not typed. SCCmec type Ⅲ was the predominant type (76 isolates), which was followed by type Ⅳ(32 isolates), type Ⅱ(24 isolates) and type Ⅴ(9 isolates). All MRSA isolates yielded 23 spa types, in which t030 (57 strains), t437 (17 strains), t002 (15 strains) and t037 (12 strains) were the predominant spa types. MRSA strains were sensitive to linezolid, teicoplanin, vancomycin and norvancomycin, but were highly resistant to other antibacterial agents, especially in strains carrying clone ST239 or of SCCmec type Ⅲ. The discriminatory power of MLST, SCCmec and spa typing were 0.6885, 0.6577 and 0.8165, respectively. Conclusion The predominant clone of MRSA strains in Zhejiang province was ST239-SCCmecⅢ-t030-MRSA, and these strains are highly resistant to most antibacterial agents, so that the surveillance of MRSA in hospital should be strengthened. Key words: Methicillin-resistant Staphylococcus aureus; Molecular typing; Multilocus sequence typing; SCCmec typing; spa typing; Microbial sensitivity tests

To investigate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates from Chinese children in seven cities. A total of 134 MRSA isolates were collected from nine hospitals. Multilocus sequence typing and spa typing were analyzed by polymerase chain reaction (PCR), and staphylococcal chromosomal cassette mec (SCCmec) type was analyzed by multiplex PCR. The Panton-Valentine leukocidin (pvl) gene was also detected. Most MRSA strains were isolated from pneumonia and skin and soft tissue infection (SSTIs) patients, accounting for 82.1%. Overall, 16 sequence types (STs) were obtained, and CC59 (51.7%) was found to be the most prevalent, which included ST 59 and ST 338, followed by ST239 (16.4%). SCCmec types II, III, IV, and V were also identified in the current study. SCCmec type IV was the most predominant type at 50.0%, followed by SCCmec type V at 23.9% and III at 23.9%. SCCmec subtypes IVa, IVc, and IVg were found among SCCmec type IV strains, whereas IVa was the main subtype at 77.6%. Twenty-six spa types were also identified, among which the predominant type was t437 (47.8%). The prevalence of pvl genes and the SCCmec type of strain was relevant, and the pvl gene positive rate was higher in SCCmec type IV and V-type strains than in SCCmec type II and III strains (58.6% vs. 14.3%, P < 0.05); there was a significant difference between them. In the strains isolated from pneumonia and SSTIs, ST59-MRSA-IVa(t437) was the predominant clone. There were five clones detected from the strains isolated from septicemia, with ST59-MRSA-IVa(t437) and ST59-MRSA-V(t437) as the main clones (57.1%). Various predominant clones existed in different regions. ST59-MRSA-IVa(t437) was the prevalent clone in the Guangzhou, Beijing, Chongqing, and Shenzhen areas, whereas ST239-MRSA-III(t037) was the prevalent clone in the Shanghai area. Fifty percent of the isolates from the Wenzhou area belonged to ST910-MRSA-V(t318), whereas three clinical strains isolated from the Shenyang region belonged to three different types. The results indicate that MRSA isolates from Chinese children are largely associated with the ST59-MRSA-IV(t437) and ST239-MRSA-III(t037) clones. These two may belong to community-acquired MRSA and hospital-acquired ones, respectively. Different prevalent clones were detected in different diseases and different regions. Therefore, there is a need to conduct further research on clinical isolates, which can guide the choice of antibiotic treatment and the examination of MRSA prevalence.

Characterization of SCCmec and spa types of methicillin-resistant Staphylococcus aureus isolates from health-care and community-acquired infections in Kerman, Iran

The goal of this study was to delineate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Ninety-six MRSA isolates were collected from the blood cultures of different patients during the period July to December of 2008. The spa typing, staphylococcal chromosomal cassette (SCCmec) typing, mec-associated direct repeat unit (dru) copy numbers, and toxin genes (sea, seb, sec, tst, lukS/F) of each isolate were determined. Thirty-eight, 28, 18, and 12 MRSA isolates were SCCmec type II, SCCmec type III, SCCmec type IV, and SCCmec type V, respectively. Most (31/38, 81.6%) of the SCCmec type II isolates were of spa t002 with four dru repeats. Some of them also carried the sec or tst toxin gene (67.7 and 80.6%, respectively). Of the 28 SCCmec type III MRSA isolates, 15 (53.6%) were of t037 with 14 dru repeats, and all also carried the sea gene. Of the 18 SCCmec type IV MRSA isolates, 13 (72.2%) were of t437 with nine dru repeats, and ten of them also had the seb gene. Among the SCCmec type V MRSA isolates, nine were type V(T). Five (55.6%) of them were of t437 with 11 dru repeats, and all contained the lukS/F gene. The clonal spreading of SCCmec MRSA strains with specific spa and dru types was found. Further longitudinal, multiple-site surveillance is required in order to define the MRSA evolution in Taiwan.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial infection-causing pathogen. The clonal shift from staphylococcal cassette chromosome mec (SCCmec) type II MRSA to SCCmec type IV MRSA has occurred rapidly in acute-care hospitals. However, the epidemiology and clinical impacts of MRSA in geriatric hospitals are poorly documented. We performed a molecular epidemiological analysis of the clinical isolates and retrospectively investigated the clinical characteristics of SCCmec type IV MRSA in elderly individuals. MRSA isolates were grouped according to the SCCmec type and virulence genes (tst, sea, seb, sec, and lukS/F-PV), and multi-locus sequence typing (MLST) was performed. Of the 145 MRSA isolates obtained from patients with a median age of 85 years, 100 (69.0%) were obtained from sputum samples, 22 (15.2%) from skin and soft tissues, and seven (4.8%) from blood samples. The most prevalent clone was SCCmec type IV/clonal complex (CC)1/sea+ (59.3%), followed by SCCmec type I/sequence type (ST) 8 (17.3%). Of the 17 (11.7%) strains to which an anti-MRSA drug was administered by a physician, only three were SCCmec type IV/CC1/sea+ (17.6%) and five were SCCmec type I/ST8 (29.4%). SCCmec type IV/CC1/sea+ MRSA was more frequently isolated in long-term care wards than were SCCmec type I/ST8 strains (odds ratio: 2.85, 95% confidence interval: 1.08-7.54) and was less frequently treated as the cause of MRSA infections (odds ratio: 0.15, 95% confidence interval: 0.03-0.73). SCCmec type IV/CC1/sea+ MRSA was the predominant clone and could be easily transmissible and be capable of colonization. Geriatr Gerontol Int 2023; 23: 744-749.

Molecular analysis and susceptibility patterns of methicillin-resistant Staphylococcus aureus strains causing community- and health care-associated infections in the northern region of Palestine

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) plays an important role in causing many serious nosocomial infections. In this study, the antimicrobial susceptibility and the frequency of aminoglycoside modifying enzyme encoding genes among clinical isolates of methicillin-resistant Staphylococcus aureus was investigated from two university hospitals of Zanjan province of Iran. Methods: In this study, the antimicrobial susceptibility of MRSA isolates to various antibiotics was investigated by the disk diffusion method. Multiplex PCR assays were used for the determination of aminoglycoside modifying enzyme (AME) genes and staphylococcal cassette chromosome mec (SCCmec) types in MRSA strains. Results: All 58 MRSA isolates were sensitive to vancomycin. Resistance to penicillin G, oxacilin, gentamicin, erythromycin, clindamycin, kanamycin, and tobramycin was found in 96.4%, 98.3%, 51.7%, 53.4%, 55.2%, 62% and 58.6% of the isolates, respectively. The most prevalent AME genes were aac(6′)/aph(2′′) (48.3 %) followed by ant(4)-Ia (24%). The aph(3′)-Ia gene was the least frequent AME gene among MRSA isolates (19%). Of the 58 tested MRSA isolates, 5 (8.6%) were harboured SCCmec type I, 11 (19%) SCCmec type II, 20 (34.5%) SCCmec type III, 17 (29.3%) SCCmec type IVa, 1 (1.7%) SCCmec type IVb, 2 (3.4%) SCCmec type IVc, 11 (19%) SCCmec type IVd, and, 18 (31%) SCCmec type V. Nineteen isolates were not typeable. Conclusion: In conclusion, the aac (6′)/aph (2′′) was the most common aminoglycoside modifying enzyme gene and SCCmec type II and V were the most frequent types detected in hospital isolates, respectively.

Background: Methicillin resistant Staphylococcus aureus (MRSA) is an increasingly common hospital pathogen in burn patients, which is known to cause over 50% of burn related deaths. One of the serious threats associated with clinical isolates of MRSA is multi-drug resistance, which is associated with integrons. Objectives: The aim of this study was to determine the distribution and molecular types of MRSA in burn patients and their carriage of integrons. Methods: During a 7-month period, 106 MRSA isolates were collected from burn wounds of patients admitted to a referral burn hospital in Tehran. Antimicrobial susceptibility testing (AST) was performed for 12 antimicrobial agents. Polymerase chain reaction (PCR) was used to detect nucA, mecA, pvl and tsst-1 genes, and class 1 and 2 integrons. Multiplex PCR technique was used to determine the Staphylococcal cassette chromosome mec (SCCmec) types of MRSA strains. All isolates were genotyped by staphylococcal protein A (spa) typing. Results: AST showed the lowest rate of resistance to quinupristin-dalfopristin (19.8%), mupirocin (31.3%), and rifampicin (37.7%). All isolates were susceptible to vancomycin, teicoplanin, and linezolid. Multi-drug resistance was observed in 97% of isolates. The most SCCmec type was SCCmec type III (98.1%) while only 2 (1.9%) MRSA isolates harbored SCCmec type IV. SCCmec types I, II, and V were not detected. The study revealed the presence of class 1 integron in 58 (54.7%) isolates and class 2 integron in 3.8% of isolates. Six different spa types of t030 (66%), t037 (14.2%), t065 (9.4%), t1358 (4.7%), t937 (3.8%), and t084 (1.9%) were identified amongst the isolates. Conclusions: The study revealed a high prevalence of multi-drug resistance (MDR), class 1 integron, SCCmec type III, and spa type t030 amongst MRSA associated with burn wounds in an Iranian hospital. The existence of SCCmec type III in burn patients emphasizes the nosocomial origin of these strains.

Background and Objectives:The ever-increasing of antibiotic resistance in methicillin-resistant Staphylococcus aureus (MRSA) has become a major threat to public health worldwide. Molecular typing is used to determine the source of MRSA infections as well as to control and prevent the spread of these pathogens. The present study aimed to investigate the characteristics of staphylococcal cassette chromosome mec (SCCmec) types and antibiotic resistance of community- acquired (CA-) and hospital acquired (HA-) MRSA isolates.Materials and Methods:In this cross-sectional study, the antibiotic susceptibility patterns of 109 clinical S. aureus isolates were determined by the Kirby-Bauer disk-diffusion and microdilution broth methods. MRSA isolates were confirmed using the polymerase chain reaction (PCR) method for the detection of the mecA gene. SCCmec typing was performed by a multiplex PCR assay among MRSA isolates.Results:The prevalence of MRSA isolates was 39.4%. Linezolid, vancomycin, and ceftaroline were the most effective agents against MRSA isolates. The incidence of multidrug-resistant (MDR) and resistance to most antibiotics were significantly higher in MRSA than methicillin-susceptible S. aureus (MSSA) isolates (P<0.05). SCCmec types I, III, and IV were identified in 27.9%, 23.3%, and 37.2% of MRSA isolates, respectively. SCCmec type I and IV were the most prevalent SCCmec types in HA-MRSA isolates (each was 32.4%). While SCCmec type IV (66.7%) was the most frequently SCCmec type associated with CA-MRSA isolates.Conclusion:Our findings demonstrated a high rate of MDR among MRSA isolates. The high existence of SCCmec type IV was reported among the HA-MRSA isolates, which can indicate the spread of MRSA community isolates to hospital settings. Therefore, appropriate antibiotic stewardship plans and microbiological surveillance initiatives must be implemented in healthcare facilities to monitor and limit the spread of these resistant bugs.

This cross-sectional descriptive study was conducted at the University of Health Sciences, Lahore, over 5 years (2016-2020) to explore the association of Panton-Valentine leucocidin (pvl) genes and staphylococcal cassette chromosome mec (SCCmec) types with hospital-acquired (HA) and community-acquired methicillin-resistant Staphylococcus aureus (MRSA). Panton-Valentine leucocidin genes in MRSA have been found in HA-MRSA strains, thereby raising the prevalence of highly virulent and resistant strains. Furthermore, the usage of staphylococcal cassette chromosome mec (SCCmec) typing is crucial for understanding the epidemiology and evolution of MRSA. The isolates of Staphylococcus aureus were acquired from clinical samples of the patients. Gram staining, catalase, coagulase, and DNAse tests were used for S. aureus confirmation. The methicillin resistance genes A and C (mecA and mecC) genes were detected to confirm MRSA by using a 30 µg cefoxitin disk. Panton-Valentine leucocidin gene identification and SCCmec typing (types I-V and XI) were conducted through polymerase chain reaction testing. Only 440 strains of MRSA were isolated, and 31.6% were positive for the pvl gene. The most prevalent SCCmec type among the MRSA isolates was type III, which was found in 42.7% of isolates. The pvl gene was detected in 74% of SCCmec types IV and V and in only 14% of SCCmec types I, II, III, and IIIA. This study revealed the dynamic adaptability of MRSA strains within healthcare settings, with the cooccurrence of the pvl gene and various SCCmec types highlighting the complexity of MRSA epidemiology. The urgent implementation of comprehensive strategies that integrate molecular surveillance and infection control measures is crucial for mitigating MRSA.

Methicillin-resistant staphylococcus aureus (MRSA) infection has now become a major public health concern. The aim of this study is to determine the antibiotic resistance pattern and prevalence of different staphylococcal cassette chromosome mec (SCCmec) types among the MRSA isolates from a teaching hospital in Shantou, China. The minimum inhibitory concentrations (MICs) ofseventeen antimicrobial agents against MRSA isolates were determined using the micro broth dilution method. SCCmec types were identified by multiplexpolymerase chain reaction (PCR) strategy. The results show that all MRSA isolates were resistant to ampicillin, oxacillin, gentamycin, erythromycin and ciprofloxacin. Fewer than 6% of isolates were resistant to doxycycline, but more than 90% were resistant to cefazolin, cefuroxime, cefotaxime, cefepime, sparfloxacin and tetracycline. There was no minocycline, chloramphenicol or vancomycin resistant. S. aureus was found in this study. SCCmec type III and IIIA were predominant in our study. Our data highlighted that multidrug-resistant strains of MRSA caused severe problems in Shantou, China. However, some of the old agents, such as minocycline, doxycycline and chloramphenicol are highly effective against MRSA isolates. Key words: Methicillin-resistant staphylococcus aureus (MRSA), staphylococcal cassette chromosome mec (SCCmec), antimicrobial agent resistance.

Background:Methicillin-resistant Staphylococcus aureus (MRSA) is known as a common pathogen in nosocomial and community-acquired infections. Sewage acts as an environmental reservoir and may have a significant role in development and dissemination of antibiotic resistance.Objectives:This study was undertaken to determine the epidemiological relatedness between the MRSA isolated from sewage and human infections.Materials and Methods:Samples were collected from a referral hospital and also a sewage treatment plant in Tehran, Iran, during 2010. All the MRSA isolates were identified at the species level and typed using Phene plate (PhP) system and SCCmec typing. Antibiotic susceptibility tests were also performed.Results:Of the 1142 isolates, 200 MRSA strains from the sewage (n = 100) and the clinic (n = 100) were isolated. Distinct PhP types, consisting of 16 common types and 13 single types, and also 3 different staphylococcal cassette chromosome mec (SCCmec) types (III, IVa and IVc) were found amongst the MRSA isolated from the two different sources. The results of antibiotic susceptibility testing showed an increased resistance to penicillin, ciprofloxacin, erythromycin, clindamycin and tetracycline. In addition, none of the isolates showed resistance to vancomycin, quinupristin -dalfopristin and linezolid.Conclusions:The presence of common PhP types and also SCCmec type III, as an indicator for hospital strains, among the isolates, may indicate an epidemiological link between clinical and sewage MRSA isolates in Tehran.

PurposeTo evaluate the rate of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) in healthy children and to determine the staphylococcal chromosomal cassette mec (SCCmec) type and toxin profile of these...

To identify the staphylococcal cassette chromosome mec (SCCmec) types of methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine milk, and examine the genetic relatedness between MRSA from bovine milk and MRSA from human isolates. Antimicrobial susceptibility tests were performed on MRSA isolated from bovine milk. PCR and sequencing analysis were performed to determine the SCCmec type of MRSA, and to confirm their toxin carriage. Genetic relatedness among the bovine isolates and between bovine and human isolates was detected with PFGE and multilocus sequence typing (MLST). Fourteen MRSA and a silent mecA-carrying methicillin-susceptible S. aureus (smMSSA) were isolated from the milk of cows with an isolation ratio of 0.18%. SCCmec of 14 MRSA strains were designated as new subtype IVg, and one smMSSA strain was not classified. All 14 MRSA strains shared Panton-Valentine leucocidin (PVL) and staphylococcal enterotoxin D (SED), SEI and SEJ; the smMSSA strain had only PVL. All MRSA and smMSSA isolates showed no multidrug resistance and had community-acquired MRSA (CA-MRSA) characteristics. PFGE revealed that all isolates except the smMSSA belonged to the same genetic lineage, and MLST analysis showed that they had no genetic relatedness with CA-MRSA which had caused human infection in Korea. MRSA isolated from bovine milk harboured a unique SCCmec subtype, and they may not be correlated with the emergence of CA-MRSA in human infection in Korea.

Methicillin-resistant Staphylococcus aureus in retail meat, Detroit, Michigan, USA.