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Published on: May 1, 2021
Identification of Major Sequence Types among Multidrug-Resistant Staphylococcus epidermidis Strains Isolated from
Smrutiti Jena1, Sasmita Panda1, Kinshuk C Nayak2
1Infectious Disease Biology, Institute of Life SciencesBhubaneswar, India.
Abstract:
We examined the presence of virulence and antibiotic resistance genes, SCCmec types and determined the genomic diversity among ocular S. epidermidis isolates (patients-23, healthy controls-29). PCR determined the presence of antibiotic resistance genes, virulence genes and SCCmec types among all isolates. MLST and PFGE determined the genomic relatedness among them. All isolates of S. epidermidis showed resistance to at least one class of antibiotics of which 48 isolates were multidrug resistant and carried ARGs. Thirty-five isolates were methicillin resistant and carried mecA gene. Majority of the isolates were resistant to fluoroquinolones and showed mutation in gyrA, parC, and parE genes, however, few isolates showed additional novel mutations in parC gene. Of the MRSE strains, 17 strains carried SCCmec type IV, four type V, two type II, and two UT4. Seven strains carried novel combination of ccr complex and SCCmercury element, not reported earlier. All the S. epidermidis strains harbored icaA and icaD genes, 47 carried ACME operon, and 50 contained IS256. A noteworthy finding was the presence of ST179 among 43% of infected eye isolates an observation rarely reported among S. epidermidis. PFGE and MLST analysis showed genomic diversity among them. Statistical analysis suggests that few healthy conjunctiva isolates had characteristics similar to infected eye isolates. S. epidermidis strains carrying mecA gene are multidrug resistant, virulent and diverse irrespective of sources of isolation. IS256 cannot be used as marker to differentiate isolates of infected eye from healthy conjunctiva.
Insights
Ocular Staphylococcus epidermidis strains exhibit significant antibiotic resistance and virulence. Methicillin-resistant strains are multidrug-resistant and genetically diverse, regardless of isolation source.
Area of Science:
- Microbiology
- Genomics
- Ophthalmology
Background:
- Ocular infections caused by Staphylococcus epidermidis are a growing concern.
- Understanding the genetic basis of virulence and antibiotic resistance in ocular S. epidermidis is crucial for effective treatment.
Purpose of the Study:
- To investigate the genetic characteristics, including virulence and antibiotic resistance genes, SCCmec types, and genomic diversity, of ocular S. epidermidis isolates from both infected patients and healthy controls.
- To determine if there are distinct genetic profiles associated with ocular infection.
Main Methods:
- Polymerase chain reaction (PCR) was used to detect antibiotic resistance genes, virulence genes, and SCCmec types.
- Multilocus Sequence Typing (MLST) and Pulsed-Field Gel Electrophoresis (PFGE) were employed to assess genomic relatedness.
- Sequence analysis was performed on specific genes like gyrA, parC, and parE.
Main Results:
- All S. epidermidis isolates displayed resistance to at least one antibiotic class; 48 were multidrug-resistant.
- Thirty-five isolates were methicillin-resistant (MRSE), carrying the mecA gene.
- Novel mutations in the parC gene were observed in fluoroquinolone-resistant strains. ST179 was prevalent in infected eye isolates (43%).
- Genomic diversity was evident through MLST and PFGE. Some healthy conjunctiva isolates shared characteristics with infected isolates.
Conclusions:
- S. epidermidis strains carrying the mecA gene are multidrug-resistant, virulent, and genetically diverse, irrespective of their isolation source (infected eyes or healthy conjunctiva).
- The presence of IS256 cannot reliably differentiate between ocular infection and healthy conjunctiva isolates.
- Further research is needed to understand the implications of novel mutations and the prevalence of specific sequence types in ocular infections.
