Current Status of Staphylococcal Cassette Chromosome mec (SCCmec)

Staphylococcal cassette chromosome mec (SCCmec) typing was established in the 2000s and has been employed as a tool for the molecular epidemiology of methicillin-resistant Staphylococcus aureus, as well as the evolution investigation of Staphylococcus species. Molecular cloning and the conventional sequencing of SCCmec have been adopted to verify the presence and structure of a novel SCCmec type, while convenient PCR-based SCCmec identification methods have been used in practical settings for many years. In addition, whole-genome sequencing has been widely used, and various SCCmec and similar structures have been recently identified in various species. The current status of the SCCmec types, SCCmec subtypes, rules for nomenclature, and multiple methods for identifying SCCmec types and subtypes were summarized in this review, according to the perspective of the International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements.

Comparison of the Staphylococcal Chromosome Cassette (SCC) mec in Methicillin-Resistant Staphylococcus aureus (MRSA) and Non-aureus Staphylococci (MRNAS) from Animals and Humans

Methicillin-resistant Staphylococcus aureus (MRSA) and non-aureus staphylococci (MRNAS) cause different infections in animals, including mastitis, in livestock and humans. This study aimed to identify and compare the staphylococcal chromosome cassette mec (SCCmec) types of MRSA or MRNAS isolated from several animal species and humans in different countries. Of 1462 S. aureus and non-aureus staphylococci, 68 grew on Chrom MRSA ID® agar, were phenotypically resistant to cefoxitin and tested positive with the PCR for the mecA gene. These 60 MRSA and 8 MRNAS were isolated in Belgium mainly from cows (livestock-associated (LA) MRS) and humans (community-acquired (CA) MRS) and in Japan from dogs and cats. The SCCmec cassettes were identified by multiplex PCR in 52 MRSA and 7 MRNAS and by whole genome sequencing (WGS) in 8 additional MRSA. The SCCmec types IV and V were the most frequent in Belgian LA-MRS and CA-MRS, while the SCCmec type II was identified in four of the five Japanese MRSA. The remaining isolate was a bovine S. haemolyticus in which no SCCmec was identified. These results confirm the high prevalence of the SCCmec types IV and V in LA-MRS and CA-MRS in Belgium, emphasizing the possible public health hazard of the former, and the absence of SCCmec in some MRNAS.

Distribution of virulence genes and SCCmec types among methicillin-resistant Staphylococcus aureus of clinical and environmental origin: a study from community of Assam, India

Objective This study was designed to discover the dissemination of virulence genes in Methicillin-resistant Staphylococcus aureus from clinical, community and environmental settings. Results This study includes 1165 isolates collected from hospital, community and environmental settings. Among them sixty three were confirmed as MRSA with varied SCCmec types viz; type I, type II, type III, type IV, type V, type VI, type VII, type VIII and type XII. The virulence gene such as sea (n = 54), seb (n = 21), eta (n = 27), etb (n = 2), cna (n = 24), ica (n = 2) and tst (n = 30) was also revealed from this study. The study underscores coexistence of resistance cassette and virulence genes among clinical and environment isolates which is first of its kind from this part of the world.

The Staphylococcal Cassette Chromosome mec (SCCmec) Analysis and Biofilm Formation of Methicillin-Resistant Staphylococcus cohnii Isolated from Clinical Samples in Tehran, Iran

Background: Methicillin-resistant coagulase-negative staphylococci is responsible for hospital and community-acquired infections. Objective: This study aimed to investigate the antibiotic-resistance patterns, antibiotic-resistance genes, namely, ermA, ermB, ermC, blaZ, msrA, tetK, tetM, mup, and vanA, biofilm formation, and prevalence of different SCCmec types among the Staphylococcus cohniistrains isolated from clinical samples in Tehran, Iran. Methods: In this study,S. cohniiisolates were screened from the clinical samples from March 2012 to February 2013 in Tehran, Iran.Antimicrobial susceptibility test and inducible clindamycin resistance were evaluated by disc diffusion method, andresistance genes were examined using Polymerase Chain Reaction (PCR) assays. Then, biofilm formation assay was analyzed by Microtiter-plate test to detect the icaA and icaDgenes. The SCCmec and the Arginine Catabolite Mobile Element (ACME) typing were performed using the PCRmethod. Results: FromtwentyS. cohnii, all isolates were resistant to cefoxitin. 95% of the S. cohnii was defined as multidrug resistance (MDR)strains. The ermB, ermC, and vanA genes were not detected in any isolates; however, the blaZ gene had the highest frequency.95% of the S. cohnii isolates produced biofilm. Also, 4 SCCmec types, including V, IV, III+ (C2), VIII+ (AB1), were identified. Therefore, the majority of SCCmec were untypable. Based on the ACME typing, arcA and opp3 genes were positive in 13 (65%) and 1 (5%) isolates, respectively. Conclusion: Due to the high antimicrobial resistance and the spread of untypableSCCmecamong the isolates studied, the control and treatment of methicillin-resistantS. cohnii in hospitals and public health centers is a significant concern.

Multiplex Polymerase Chain Reaction Based Typing of Staphylococcal Chromosomal Cassette mec of Methicillin Resistant Staphylococcus aureus from Selected Hospitals in Lahore

Introduction: Staphylococcus aureus is one of the leading causes of nosocomial infections. Prevalence of methicillin resistant Staphylococcus aureus (MRSA) has been reported in up to 42% of isolates in Pakistan. Methicillin resistance is encoded by the mecA gene and it is transferred by a unique genetic vector called staphylococcal chromosomal cassette (SCCmec). Depending upon the selection pressures of antibiotics, different types of SCCmec elements may prevail in different parts of the world. Materials and Methods: Therefore, this study was designed to fi nd out the major SCCmec types present in selected hospitals of Lahore. For this purpose thirty fi ve MRSA isolates were collected. These strains were reconfi rmed and SCCmec types were determined by multiplex PCR. Results: It was found that 21 (60%) isolates possess SCCmec type IA while 14 (40%) isolates possess SCCmec type IIC. Conclusion: These cassettes are shown to be multiresistant and have not been reported in other Asian countries so far.

Antimicrobial Resistance and Virulence of Methicillin-Resistant Staphylococcus aureus from Human, Chicken and Environmental Samples within Live Bird Markets in Three Nigerian Cities

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major threat to public health. This study investigated the occurrence of MRSA in humans, chickens, chicken meat and environmental samples within poultry farms and live bird markets in southwestern Nigeria. Methods: MRSA were isolated using selective culture and tested for antimicrobial susceptibility by broth microdilution. Selected isolates were characterized by whole genome sequencing (WGS). From WGS data, spa, dru, multilocus sequence typing (MLST) and SCCmec types, but also virulence and antimicrobial resistance genes, were identified. Results: Fifty-six MRSA isolates were detected in 734 samples. They showed resistance to β-lactams (100%), tetracycline (60.7%), ciprofloxacin (33.9%), erythromycin (28.6%), gentamicin (32.1%), and trimethoprim/sulfamethoxazole (10.7%). All 30 isolates investigated by WGS carried mecA, dfrG, and tet(38) genes. Other resistance genes detected were blaZ (83.3%), fosB (73.3%), tet(K) (60.0%), aacA-aphD (36.6%), aphA3 (33.3%), msr(A) (30.0%), mph(C) (30.0%), dfrS1 (3.3%), and sat4 (3.3%). Seven spa types (t091, t314, t657, t1476, t2331, t4690 and t12236), four known (dt9aw, dt10ao, dt10cj, and dt11a) and two novel (dt10dr and dt11dw) dru types, as well as five sequence types (ST8, ST121, ST152, ST772 and ST789) were found among the MRSA isolates. All ST121 isolates carried an SCCmec type IV cassette and were not dru-typeable. ST152 and ST121 were found only in specific sample categories within defined locations, while ST8 and ST772 were distributed across most sample categories and locations. Three SCCmec types, IVa, V and Vc, were identified. All MRSA isolates possessed virulence genes including aur, clpP, coa, fnbA, esaA, hly, hla, ica, isdA, srtB, sspA, and vWbp, among others. The toxic shock syndrome toxin gene (tst) was not detected in any isolate, whereas the Pantone–Valentine leukocidin genes lukF-PV/lukS-PV were present in all ST121, all ST772, and all but one ST152 isolates. Conclusion: The results of this study (i) showed that chicken meat is contaminated by MRSA and (ii) suggested that live bird markets may serve as focal points for the dissemination of MRSA within the community.