Diversity of Sccmec types in Methicillin Resistant Staphylococcus Spp. Causing Hospital-Associated Infections

Review Article

Diversity of Sccmec types in Methicillin Resistant Staphylococcus Spp. Causing Hospital-Associated Infections

Corresponding author: Dr. Nilma Cintra Leal, Departamento de Microbiologia – Centro de Pesquisas Aggeu Magalhães – FIOCRUZ/PE, Campus da UFPE, Cidade Universitária, 50740-465, Recife-PE, Brazil.Tel: (+55) 81 2101 2568; Fax: (+55) 81 2101 2647;
Email: nilma@cpqam.fiocruz.br or nilmacleal@gmail.br

Abstract

The determination of SCCmec types among staphylococcal strains causing infections in the hospital environment is crucial for understanding the basis of genetic transfer, tracking the emergence and dispersion routes of the strains involved, and defining control strategies. The aim of this study was to determine the SCCmec types of methicillin-resistant (MR)Staphylococcus spp causing hospital-associated infections and to compare the diversity of SCCmec types betweenStaphylococcus aureus (S. aureus) and coagulase-negative Staphylococcus (CoNS) clinical MR isolates. SCCmec types were assessed via a PCR-based scheme using sets of primers targeting the ccr and mec complexes and other structures. The results revealed differences in the distribution of SCCmec types between the analyzed S. aureus and CoNS isolates.SCCmec types II, III and IV were evenly distributed among the S. aureus strains. Among the CoNS isolates, the SCCmectypes occurred in different proportions: the highest frequency was observed for SCCmec IV, followed by type III, while type V, which was absent from the S. aureus strains, occurred in a lower percentage of the CoNS strains. A number of isolates could not be categorized and were designated as non-typable (NT). The frequency of NT isolates was higher among the S. aureus strains than the CoNS strains, but the difference was not statistically signi ficant (p-value = 0.2485). We hope that this study will contribute to improving the understanding of the molecular epidemiology ofSCCmec types among hospital infection-associated S. aureus and CoNS strains in the study region.

Keywords: Staphylococcus aureus; Coagulase-Negative Staphylococcus; Sccmec Types; Hospital Infection.

Introduction

A large proportion of hospital-acquired staphylococcal infections are caused by methicillin-resistant Staphylococcusaureus (MRSA). However, methicillin-resistant coagulase-negative Staphylococcus (MRCoNS) nosocomial infections, particularly those associated with prosthetic devices, are increasing [1-3].

Methicillin resistance (MR) in staphylococci is conferred by an alternative penicillin-binding protein known as PBP2a or PBP2’, which is essential for cell wall synthesis and bacterial growth in the presence of β-lactam antibiotics. PBP2a is encoded by the mecA gene, which is located on a mobile genetic element (MGE) referred to as staphylococcal cassette chromosome mec (SCCmec) [3,4]. Structurally, SCCmec is composed of two major complexes (the mec gene complex and the ccr gene complex) and several nonessential components: three joining (J1-J3) regions and a few other genes or pseudogenes that may carry various other MGEs, such as insertion sequences, transposons and integrated plasmids carrying additional determinants of antimicrobial resistance to non-β-lactam antibiotics or heavy metals [5].

There are currently 11 major SCCmec types (I-XI) that have been identified among staphylococci based on the combination of the structures of the ccr and mec gene complexes. The distribution and prevalence of SCCmec types varies throughout the world depending on the source (related to the host species, hospital or community environment, antibiotic use, geographical origin and isolation period) [1, 5-14]: SCCmec types I-V appear to be globally distributed, while the other types are limited to the country of origin; SCCmec types I, II and III are hospital associated (HA), while types IV, V, VI and VII are community associated (CA) [15, 16]. However, changes are occurring worldwide [1, 5- 6, 8-14].

Methicillin resistance is more prevalent in CoNS than in S. aureus [17]. Hence, CoNS strains are considered to represent a
large SCCmec reservoir [17]. CoNS are regarded as potential SCCmec donors, and it is believed that they serve as donors  of SCCmec to S. aureus [2]. In fact, new MRSA clones are continuously emerging, spreading and adapting to the environment [6,11,17].

Therefore, it is necessary to determine the distribution of SCCmec types among staphylococcal strains causing hospital infections to understand the basis of genetic transfers, to track the emergence and dispersion routes of the strains involved and to define control strategies. In Brazil, most of the available information on this topic is limited to the south and southeast regions [18-23], while studies carried out in the northeast region [24,25] have not yet fully addressed this subject. Thus, with the aim of addressing this issue, we performed an analysis of nosocomial infection-associated MR S. aureus and CoNS isolates through multiplex PCR (M-PCR) and long-range PCR using primers targeting the ccr and mec complexes and associated structures.

Materials and Methods

Bacterial isolates and growth conditions

The study included 39 clinical S. aureus and 45 CoNS mecA PCR-positive isolates from the bacteriotheque of the Department of Microbiology, CPqAM/FIOCRUZ-PE. The isolates originated from a university hospital in Recife, PE, Brazil, between 2002-2010 and were stored at -80ºC in brain heart infusion (BHI) broth (HiMedia Laboratories Pvt Ltd 23, Vadhani Industrial Estate, LBS Marg, Ghatkopar West, Mumbai, Maharashtra 400086, India) / 25% glycerol.

The sources of the strains are shown in Tables 1 and 2. The infections from which the isolates were obtained were characterized as nosocomial infections according to the Centers for Disease Control and Prevention criteria [26], and the isolates were identified using the conventional bacteriological catalase test, the coagulase tube test, the thermonuclease growth test, and the mannitol salt agar test. All of the samples were methicillin resistant, as determined by the presence of the mec gene via PCR [27]. The absence of coagulase in the strains was confirmed by a PCR test negative for the coa gene [28].

The following reference strains were used as controls: MRSA05166 and MRSA05279 (SCCmec type II), MRSA04673 and MRSA05616 (SCCmec type III); MRSA01171 and MRSA03343 (SCCmec type IV); and MRSA02928 and MRSA03231 (SCCmec type V).

Unless otherwise stated, all cultures were grown on sheep blood agar plates overnight at 37º C.

Bacterial DNA extraction

DNA samples were extracted following a protocol based on Ausubel et al. [29]. Briefly, 1 ml of each bacterial culture in BHI
was centrifuged for 10 min at 20,000 x g. The resulting pellet was washed with 500 μL of Tris: EDTA (10:1), and 10 μg of lysostaphin and 5 μg proteinase K were added to lyse the cells. The samples were subsequently incubated at 60°C for 20 minutes, and 100 μL of STE (2.5% SDS, 0.25 M EDTA, 10 mM Tris pH 8.0) was added. The samples were next incubated at 60°C for 15 minutes, then at room temperature for 5 minutes and in an ice bath for 5 minutes, after which 130 μL of 7.5 M sodium acetate was added, followed by incubation in an ice bath for 15 minutes and centrifugation for 3 minutes at 20,000 x g. At this point, 700 μL of the supernatant was transferred to a new tube; 420 μL of isopropanol was added; and the samples were then incubated at -80°C for 30 minutes and centrifuged at 20,000 x g for 10 minutes. The supernatant was discarded, and the pellet DNA was vacuum dried and resuspended in 10 μL of 0.02% RNAse. The obtained DNA was quantified using a NanoDrop 2000 (Thermo Fisher Scientific Inc. 81 Wyman Street, Waltham, MA 02451 USA).

Determination of SCCmec types

SCCmec types were determined via multiplex PCR (M-PCR) following Kondo et al. [30] using primers targeting the mec gene complex, the ccr gene complex and other structures, including the mercury resistance operon (SCCHg) and the IS1272 and IS431 elements (Table 3). The reactions were prepared in a final volume of 50 μL containing 5 μL of l Green Go Taq buffer (Promega Corporation. 2800 Woods Hollow Road, Madison, WI 53711 USA), 2.5 mM of each deoxynucleotide, 25 mM MgCl2, 1.5 U of Go Taq DNA polymerase (Promega), 20 ng of DNA from each sample and the primers at 10 μM. Thermocycler amplifications were performed as follows: 30 cycles of 94°C for 1 min, 57°C for 1 min, and 72°C for 1 min, with a final extension at 72°C for 7 minutes. The amplification products were electrophoresed on 2% agarose gels stained with the GelRed Nucleic Acid Stain (Biotium Inc. 3159 Corporate Place, Hayward, CA 94545 USA), visualized in a UV transilluminator and digitalized using KODAK 1D software, version 3.5.2 (Eastman Kodak Company, 1669 Lake Avenue, Rochester, NY 14652 USA).

DNA sequencing

Each mec class element was amplified via long-range PCR using previously described primers [31, 32] and other primers designed specifically for this study (Table 3). The reactions were performed in a final volume of 50 μL, containing 5 μL of 10 × PfuUltra ™ II buffer (Stratagene, 1834 W. Hwy 71, Cedar Creek, TX 78612 USA), 200 mM dNTPs, 10 mM primers, 1 μL of PfuUltra ™ II fusion HS DNA polymerase (Stratagene) and 10 ng of DNA. The reactions were performed in a Mastercycler ep gradient thermal cycler (Eppendorf, HQ Barkhausenweg 1 22339 Hamburg, Germany) under the conditions recommended by the manufacturer. The amplicons were purified using ExoSAP-IT® (Affymetrix, 3420 Central Expressway, Santa Clara, CA 95051 USA) and sequenced via the Sanger method. The obtained sequences were processed using SeqMan II (Lasergene software, DNASTAR, Inc., Madison, WI), assembled using ClustalW and compared with GenBank sequences using BLAST (http://www.ncbi.nih.gov/BLAST).

Statistical analysis

The data were analyzed with Pearson’s chi-square statistic test using R software [33]. For the purpose of this work, a p-value of ≤0.05 was considered statistically significant.

Results

SCCmec types were determined based on the classes of the mec gene and ccr gene complex structures (Table 3). According to the amplification results, out of the 84 isolates, 68 were assigned to SCCmec types II (mec gene complex class A / ccr gene complex class ccrAB2), III (mec gene complex class A / ccr gene complex class ccrAB3), IV (mec gene complex class B / ccr gene complex class ccrAB2) and V (mec gene complex class C / ccr gene complex class ccrC). Overall, 16.7% of the isolates were classified as SCCmec type II; 26.2% as SCCmec type III; 34.5% as SCCmec type IV; and 3.6% as SCCmec type V.

The remaining 16 (19%) isolates (10 S. aureus and six CoNS), could not be typed according to the scheme that was employed and were designated as SCCmec non-typable (NT). The NT isolates showed amplification of the ccr gene complex class ccr- AB2, but there was no PCR amplification of the targeted mec complex genes.

The percentage of NT isolates (Table 4) was higher among the S. aureus strains (25.6%) than the CoNS strains (13.3%). However, this difference was not statistically significant (p-value = 0.2485).

The 39 S. aureus strains harbored SCCmec types II, III and IV in similar proportions, and the percentage of NT isolates was also similar (p-value = 0.99). The SCCmec type V element was not found among the analyzed strains (Table 4).

The 45 CoNS isolates harbored SCCmec types II, III, IV and V and NT in significantly different proportions (p-value = 0.000368) (Table 4). SCCmec type IV was the most prevalent (42.2%), followed by SCCmec type III (29.0%).

To obtain further insight into the structure of the SCCmec elements, the presence of the SCCHg operon was investigated in the 22 isolates harboring type III SCCmec, and all of them (9 S. aureus and 13 CoNS) yielded amplification products using the primers targeting the ccrC element (Table 3). The amplified segments were sequenced via long-range PCR and were found to show homology with the sequence of the SCCHg operon, confirming the identity of the segment.

For further confirmation, the SCCmec type IV strains were analyzed with primers targeting the IS1272 and IS431 elements. Both sequences were amplified in all 29 SCCmec type IV isolates (10 S. aureus and 19 CoNS), and the segments were confirmed via sequencing.

Analysis of the amplified sequences revealed 99% identity with the sequences deposited in GenBank: accession numbersD86934 for SCCmec type II, AB037671 for SCCmec type III, AB063172 for SCCmec type IV and AB121219 forSCCmec type V.

Discussion

In this study, we addressed the occurrence of the various SCCmec types in MR Staphylococcus spp. causing hospital-associated infections. Previous studies have reported the occurrence of SCCmec types I, II, III, IV and V in Brazilian hospitals in the south and southeast regions [18-23]. Thus far, SCCmec types VI, VII, IX, X and XI have not been reported in Brazil. In the present study, the isolates were classified as SCCmec types II,III, IV, V and NT (non-typable).

The failure to determine the SCCmec types of some strains was previously attributed to the presence of new structures and rearrangements or recombination within the mec complex [1,6,9,13,21]. New variants of the ccr genes continue to be identified, which cannot be typed using the currently available schemes, and new schemes for the classification ofSCCmec are in need of improvement [14,34-36].

SCCmec types IV, V, VI and VII are traditionally categorized as community associated (CA) and types I, II and III as hospital associated (HA) [15,16]. However, changes in this epidemiological profile are being observed worldwide, with an increase in the prevalence of CA clonal lineages within hospital environments, abolishing the separation between traditional CA and HA clones [15,16].

As previously reported in hospitals from southern and southeastern Brazil [19,20], in our study, SCCmec types III and IV occurred at a higher frequency than SCCmec types II and V (Table 4). SCCmec type I was not identified, despite being reported in other studies conducted in southern and southeastern Brazil [19-22]. The frequency of SCCmec type II was higher among the S. aureus strains (25.6%) than the CoNS strains (8.9%) (Table 4).

The frequency of SCCmec type III in S. aureus (23.2%) was quite close to that in the CoNS isolates (29.0%). SCCmectype III encodes the largest number of resistance genes, and strains harboring this type are important pathogens in hospitals, where they cause severe infections, and should therefore be considered in infection control policies [7]. It was observed that the SCCmec type III element is a composite of two smaller SCC elements integrated in tandem: the SCCmercury (SCCHg) operon and the type III SCCmec element [5,35]. The presence of SCC Hg was confirmed in the isolates through PCR and sequencing.

Although SCCmec type IV is categorized as CA, in our study this type was the most prevalent among the CoNS strains (42.2%), and it was also found at a high frequency (25.6%) among the S. aureus strains (Table 4). The occurrence of SCCmec type IV in Brazilian nosocomial isolates was previously reported [37-38]. The higher prevalence of SCCmec type IV could be attributed to the small size of this element, which is likely to increase in  revalence over time due to the low metabolic cost of its transfer [7].

SCCmec type V, which is seldom reported in Brazil [18,19], was found in a low percentage of the CoNS isolates (6.7%) and was absent among the S. aureus strains (Table 4) in the present study.

Rather than representing a mere contaminant, as was previously indicated, CoNS is now recognized as an important nosocomial infectious agent acting as a reservoir of virulence genes in the hospital environment, in addition to serving as a reservoir and donor of resistance genes [2,17,39]. A previous study on methicillin-resistant Staphylococcus spp. causing hospital- associated infections [40] revealed the toxigenic potential of CoNS strains. It was observed that out of 43 CoNS isolates analyzed, 18 (41.86%) showed amplification of at least one toxigenic gene. Carrying staphylococcal toxigenic genes indicates the ability of CoNS to incorporate toxigenic genes, which increases their toxigenic potential as well as their ability to invade sterile sites and their ability to cause serious hospital-acquired infections.

In conclusion, differences were observed in the distribution of SCCmec types between S. aureus and CoNS isolates obtained from hospital-associated infections in this study (Table 4). In general, the CoNS strains displayed an absence ofSCCmec type I; a low frequency of SCCmec type II; and a higher frequency of SCCmec type IV. In contrast, SCCmectypes II, III, IV and NT were evenly distributed among the S. aureus strains. Among the CoNS strains, the SCCmecelements occurred in different proportions: the highest frequency was observed of SCCmec type IV (42.2%), followed bySCCmec type III (29.0%). SCCmec type V was absent from S. aureus and displayed a low frequency (6.7%) among the CoNS strains. The frequency of NT (25.6%) was higher among the S. aureus strains than the CoNS strains (13.3%), but this difference was not statistically significant. This study contributes to reducing the gap in our knowledge of the molecular epidemiology of SCCmec types among hospital infection-associated S. aureus and CoNS strains in the study region.

Acknowledgments

We thank the Foundation of Science and Technology of the State of Pernambuco (FACEPE) for financial support and the Technology Platform CPqAM / FIOCRUZ / PE for the DNA sequencing. This work was supported in part by a Fogarty International Center Global Infectious Diseases Research Training Program grant, National Institutes of Health, to the University of Pittsburgh (D43TW006592).

Conflict of interest

There is no conflict of interest to declare.

References

1.Garza-gonzalez E, Morfin-Otero R, Llaca-Díaz JM, Rodriguez-Noriega E. Staphylococcal cassette chromosome mec (SCCmec) in methicillin-resistant coagulase-negative staphylococci. A review and the experience in a tertiary- care setting. Epidemiol Infect. 2010, 138(5): 645–654.

2.Hiramatsu K, Cui L, Kuroda M, Ito T. The emergence and evolution of methicillin-resistant Staphylococcus aureus Trends  Microbiol. 2001, 9(10): 486-493.

3.Hiramatsu K, Ito T, Tsubakishita S, Sasaki T, Takeuchi F et al. Genomic Basis for Methicillin Resistance in Staphylococcus aureus. Infect Chemother. 2013, 45(2): 117-136.

4.Shore AC, Coleman DC. Staphylococcal cassette chromosome mec: recent advances and new insights. Int J Med Microbiol. 2013, 303(6-7): 350-359.

5.IWG-SCC. Classification of staphylococcal cassette chromosome mec (SCCmec): guidelines for reporting novel SCCmec elements. Antimicrob Ag Chemoth. 2009, 53(12): 4961–4967.

6.Garza-González E, López D, Pezina C, Muruet W, Bocanegra- García V et al. Diversity of staphylococcal cassette  chromosome mec structures in coagulase negative staphylococci and relationship to drug resistance. J Med Microbiol. 2010, 59(3): 323-329.

7.Ito T, Katayama Y, Asada K, Mori N, Tsutsumimoto K et al. Structural comparison of three types of staphylococcal cassette chromosome mec integrated in the chromosome in methicillin-resistant Staphylococcus aureus. Antimicrob Ag Chemoth. 2001, 45(5): 1323–1336.

8.IWG-SCC: International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements; 2012.

9.Li S, Skov RL, Han X, Larsen AR, Larsen J et al. Novel types of staphylococcal cassette chromosome mec elements identified in clonal complex 398 methicillin-resistant Staphylococcus aureus strains. Antimicrob Ag Chemoth. 2011, 55(6): 3046–3050.

10.Shore AC, Deasy EC, Slickers P, Brennan G, O’Connell B et al. Detection of staphylococcal cassette chromosome mec type XI carrying highly divergent mecA, mecI, mecR1, blaZ, and ccr genes in human clinical isolates of clonal complex 130 methicillin-resistant Staphylococcus aureus. Antimicrob Ag. Chemother. 2011, 55(8): 3765–3773.

11.Vitali LC, Petrelli D, Lamikanra A, Prenna M, Akinkunmi EO et al. Diversity of antibiotic resistance genes and staphylococcal cassette chromosome mec elements in faecal isolates of coagulase-negative staphylococci from Nigeria. BMC Microb. 2014, 14: 106.

12.Zhang Y, Agidi S, LeJeune JT. Diversity of staphylococcal cassette chromosome in coagulase-negative staphylococci from animal sources. J Appl Microbiol. 2009, 107(4): 1375–1383.

13.Zhiyong Z, Chunhong P, Xiaoju, L. Diversity of SCCmec elements in methicillin resistant coagulase negative Staphylococci clinical isolates. Plos One. 2011, 6(5): e20191.

14.Zong Z, Lü X. Characterization of a new SCCmec element in Staphylococcus cohnii. PLoS ONE. 2010, 5(11): e14016.

15.Katayama Y, Teruyo I, Hiramatsu K. Genetic organization of the chromosome region surrounding mecA in clinical Staphylococcal strains: role of IS431-mediated mecI deletion in expression of resistance in mecA-carrying, low-level methicillin-resistant Staphylococcus haemolyticus. Antimicrobial Agents Chemotherapy. 2001, 45(7): 1955-1963.

16.Deurenberg RH, Stobrering EE. The evolution of Staphylococcus aureus. Infect Genet Evol. 2008, 8(6): 747-763.

17.Fluit AC, Carpaij N, Majoor EA, Bonten MJM, Willems RJL et al. Shared reservoir of ccrB gene sequences between   coagulase- negative staphylococci and methicillin-resistant Staphylococcus aureus. J Antimicrob Chemother. 2013, 68(8): 1707-1713.

18.Lamaro-Cardoso J, de Lencastre H, Kipnis A, Pimenta FC, Oliveira LSC et al. Molecular epidemiology and risk factors for nasal carriage of Staphylococcus aureus and methicillin- resistant S. aureus in infants attending day care centers in Brazil. J Clin Microbiol. 2009, 47(12): 3991–3997.

19.Garza-gonzalez E, Morfin-Otero R, Llaca-Díaz JM, Rodriguez- Noriega E. Staphylococcal cassette chromosome mec (SCCmec) in methicillin-resistant coagulase-negative staphylococci. A review and the experience in a tertiary- care setting. Epidemiol Infect. 2010, 138(5): 645–654.

20.Hiramatsu K, Cui L, Kuroda M, Ito T. The emergence and evolution of methicillin-resistant Staphylococcus aureus Trends Microbiol. 2001, 9(10): 486-493.

21.Hiramatsu K, Ito T, Tsubakishita S, Sasaki T, Takeuchi F et al. Genomic Basis for Methicillin Resistance in Staphylococcus aureus. Infect Chemother. 2013, 45(2): 117-136.

22.Shore AC, Coleman DC. Staphylococcal cassette chromosome mec: recent advances and new insights. Int J Med Microbiol. 2013, 303(6-7): 350-359.

23.IWG-SCC. Classification of staphylococcal cassette chromosome mec (SCCmec): guidelines for reporting novel SCCmec elements. Antimicrob Ag Chemoth. 2009, 53(12): 4961–4967.

24.Garza-González E, López D, Pezina C, Muruet W, Bocanegra- García V et al. Diversity of staphylococcal cassette  chromosome mec structures in coagulase negative staphylococci and relationship to drug resistance. J Med Microbiol. 2010, 59(3): 323-329.

25.Ito T, Katayama Y, Asada K, Mori N, Tsutsumimoto K et al. Structural comparison of three types of staphylococcal cassette chromosome mec integrated in the chromosome in methicillin-resistant Staphylococcus aureus. Antimicrob Ag Chemoth. 2001, 45(5): 1323–1336.

26.IWG-SCC: International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements; 2012.

27.Li S, Skov RL, Han X, Larsen AR, Larsen J et al. Novel types of staphylococcal cassette chromosome mec elements  identified in clonal complex 398 methicillin-resistant Staphylococcus aureus strains. Antimicrob Ag Chemoth. 2011, 55(6): 3046–3050.

28.Shore AC, Deasy EC, Slickers P, Brennan G, O’Connell B et al. Detection of staphylococcal cassette chromosome mec type XI carrying highly divergent mecA, mecI, mecR1, blaZ, and ccr genes in human clinical isolates of clonal complex 130 methicillin-resistant Staphylococcus aureus. Antimicrob Ag. Chemother. 2011, 55(8): 3765–3773.

29.Vitali LC, Petrelli D, Lamikanra A, Prenna M, Akinkunmi EO et al. Diversity of antibiotic resistance genes and staphylococcal cassette chromosome mec elements in faecal isolates of coagulase-negative staphylococci from Nigeria. BMC Microb. 2014, 14: 106.

30.Zhang Y, Agidi S, LeJeune JT. Diversity of staphylococcal cassette chromosome in coagulase-negative staphylococci from animal sources. J Appl Microbiol. 2009, 107(4): 1375–1383.

31.Zhiyong Z, Chunhong P, Xiaoju, L. Diversity of SCCmec elements in methicillin resistant coagulase negative Staphylococci clinical isolates. Plos One. 2011, 6(5): e20191.

32.Zong Z, Lü X. Characterization of a new SCCmec element in Staphylococcus cohnii. PLoS ONE. 2010, 5(11): e14016.

33.R Development Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: the R Foundation for Statistical Computing. 2013.

34.Chongtrakool P, Ito T, Ma XX, Kondo Y, Trakulsomboon S et al. Staphylococcal cassette chromosome mec (SCCmec) typing of methicillin resistant Staphylococcus aureus strains isolated in 11 Asian countries: a proposal for a new nomenclature for SCCmec elements. Antimicrob Ag Chemoth. 2006, 50(3):1001–1012.

36.Oliveira DC, Santos M, Milheiriço C, Carriço JA, Vinga S et al. ccrB typing tool: an online resource for staphylococci ccrB sequence typing. J Antimicrob Chemoth. 2008, 61(4): 959–964.

37.de Miranda OP, Silva-Carvalho MC, Ribeiro A, Portela F, Cordeiro RP et al. Emergence in Brazil of methicillin-resistant Staphylococcus aureus isolates carrying SCCmec IV that are related genetically to the USA800 clone. Clin Microbiol Infect. 2007, 13: 1165-1172.

38.Trindade PA, Pacheco RL, Costa SF, Rossi F, Barone AA et al. Levin AS (2005) Prevalence of SCCmec Type IV in  Nosocomial  Bloodstream Isolates of Methicillin-Resistant Staphylococcus aureus. J Clin Microbiol. 43(7): 3435-3437.

39.Longauerova A. Review: Coagulase negative staphylococci and their participation in pathogenesis of human infections. Bratisl Lek Listy. 2006, 107(11-12): 448-452.

40.Oliveira WLM, Ferreira EL, Mangueira EVC, Vilela MA, Almeida AMP, Leal NC. Coagulase-negative staphylococci from hospital-associated infections harboring virulence genes. J J Microbiol Pathol. 2014, 1(2): 013.

Be the first to comment on "Diversity of Sccmec types in Methicillin Resistant Staphylococcus Spp. Causing Hospital-Associated Infections"

Leave a comment

Your email address will not be published.


*