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Published on: May 8, 2013
Identification and characterization of SCCmec typing with psm-mec positivity in staphylococci from patients with
Jun Zhou1, Chuishun Yang1, Wenjuan Lei1
1Department of Nephrology and Rheumatology, Haikou People's Hospital Affiliated to Xiangya School of Medicine, Haikou, China.
Background:
Peritonitis is the most important complication of peritoneal dialysis (PD) and coagulase-negative staphylococci (CNS) are a frequent cause of dialysis-related infections. The association between SCCmec typing with psm-mec positivity in staphylococci and PD-related infections has not been identified. We aim to investigate the molecular epidemiology of CNS isolated from PD-peritonitis in a single Chinese center, focusing on the genetic determinants conferring methicillin resistance.
Methods:
We collected 10 genetically unrelated CNS isolates from 10 patients with CNS PD-related peritonitis. The patients were divided into two groups based on the results of MIC to oxacillin: the methicillin-resistant CNS (MRCNS) and methicillin-sensitive CNS (MSCNS) groups. The biofilm formation group (BFG) and the non-biofilm formation group (NBFG) were used as the control groups. Phenotypic and molecular methods were used to analyze SCCmec types I, II and III, associated genes and biofilm formation and the existence of psm-mec. The demographic data and clinical indicators were collected.
Results:
Ten CNS PD-related peritonitis patients were enrolled for this study. There were 6 MRCNS and 4 MRCNS isolates. SCCmec types were fully determined in 10 isolates. Seven staphylococci (70%) carried SCCmec, of which 4 isolates carried single SCCmec type I (40%) and 3 isolates had multiple SCCmec elements (I + III). Of the 6 MRCNS isolates, 3 carried SCCmec type I (50%) and 2 isolates carried SCCmec type I + III (33.3%). A high diversity of ccr types, mec complexes and ccr-mec complex combinations was identified among the 10 CNS isolates. The psm-mec gene was detected in 2/10 (20%) CNS isolates. There was no mutation in the psm-mec gene.
Conclusions:
The majority of isolates were hospital-associated isolates. Furthermore, 2 psm-mec positive isolates were MRCNS in the NBFG. The PD patients frequent exposure to hospital would be the main risk factor. The presence of the psm-mec signal in the spectra of the MRCNS tested here demonstrates the presence of certain SCCmec cassettes that convey methicillin resistance.
Insights
This study investigated coagulase-negative staphylococci (CNS) causing peritonitis in peritoneal dialysis (PD) patients. Methicillin-resistant CNS (MRCNS) isolates frequently carried SCCmec type I, with some also having psm-mec, highlighting hospital exposure as a risk factor.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Peritonitis is a major complication of peritoneal dialysis (PD).
- Coagulase-negative staphylococci (CNS) are common causes of PD-related infections.
- The link between SCCmec typing, psm-mec positivity, and PD infections is not well understood.
Purpose of the Study:
- To investigate the molecular epidemiology of CNS isolates from PD peritonitis.
- To identify genetic determinants of methicillin resistance in CNS.
- To explore the association between SCCmec types, psm-mec, and biofilm formation.
Main Methods:
- Collected 10 genetically unrelated CNS isolates from PD peritonitis patients.
- Classified isolates into methicillin-resistant (MRCNS) and methicillin-sensitive (MSCNS) groups.
- Analyzed SCCmec types (I, II, III), biofilm formation, and psm-mec gene presence using phenotypic and molecular methods.
Main Results:
- Seven out of ten (70%) CNS isolates carried SCCmec, with Type I being most common (40%).
- Six isolates were MRCNS, with 50% carrying SCCmec Type I.
- The psm-mec gene was detected in 20% of isolates, specifically in methicillin-resistant strains within the non-biofilm forming group.
Conclusions:
- Hospital-associated isolates were predominant, suggesting frequent hospital exposure as a key risk factor for PD patients.
- The presence of psm-mec in MRCNS indicates specific SCCmec cassettes conferring methicillin resistance.
- This study provides insights into the genetic makeup of CNS causing PD peritonitis.
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