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Published on: November 4, 2016
MLST-Based Analysis and Antimicrobial Resistance of Staphylococcus epidermidis from Cases of Sheep Mastitis in Greece
Eleni I Katsarou1, Dimitris C Chatzopoulos1, Themis Giannoulis2
1Veterinary Faculty, University of Thessaly, 43100 Karditsa, Greece.
Abstract:
Staphylococcus epidermidis is an important causal agent of ovine mastitis. A literature search indicated a lack of systematic studies of causal agents of the infection by using multi-locus sequence typing (MLST). The objectives were to analyse MLST-based data and evaluate the antimicrobial resistance of S. epidermidis isolates from ovine mastitis in Greece. The database included 1593 isolates from 46 countries: 1215 of human, 195 of environmental and 134 of animal origin, distributed into 949 sequence types (STs) and cumulatively with 450 alleles therein. Among mastitis isolates, bovine isolates were distributed into 36 different STs and ovine ones into 15 STs. The 33 isolates from ovine mastitis in Greece were in 15 different STs, 6 of these (ST677, ST678, ST700, ST 709, ST710, ST711) assigned for the first time; in addition, 5 alleles (65 for arcC, 59 for aroE, 56 and 57 for gtr and 48 for tpiA) were identified for the first time. The spanning tree of these isolates included 15 nodes and 14 edges (i.e., branches). Among these isolates, 19 showed resistance to antimicrobial agents (tetracycline, penicillin, fucidic adic, erythromycin, clindamycin, cefoxitin). Resistance-related genes (tetK, tetT, msrA, tetM, tetS, ermC, mecA) were detected. There was no association between STs and resistance to antimicrobial agents. Isolates with antimicrobial resistance were recovered more often from flocks where hand-milking was practised.
Insights
This study analyzed Staphylococcus epidermidis causing ovine mastitis in Greece using multi-locus sequence typing (MLST). It identified novel sequence types and found antimicrobial resistance in some isolates, often linked to hand-milking practices.
Area of Science:
- Veterinary Microbiology
- Molecular Epidemiology
- Antimicrobial Resistance
Background:
- Staphylococcus epidermidis is a significant cause of ovine mastitis globally.
- Limited systematic studies using multi-locus sequence typing (MLST) exist for S. epidermidis in ovine mastitis.
- Understanding the genetic diversity and antimicrobial resistance profiles is crucial for effective disease management.
Purpose of the Study:
- To analyze MLST-based data of S. epidermidis isolates from ovine mastitis in Greece.
- To evaluate the antimicrobial resistance patterns of these isolates.
- To identify novel sequence types (STs) and alleles within the ovine mastitis population.
Main Methods:
- Utilized a comprehensive database of 1593 S. epidermidis isolates from various origins (human, environmental, animal).
- Applied multi-locus sequence typing (MLST) to characterize 33 ovine mastitis isolates from Greece.
- Determined antimicrobial susceptibility and detected resistance-related genes (e.g., mecA, tetK, ermC).
Main Results:
- The 33 Greek ovine mastitis isolates represented 15 distinct STs, including 6 newly assigned STs (ST677-ST711).
- Five novel alleles were identified across specific genes (arcC, aroE, gtr, tpiA).
- Nineteen isolates exhibited resistance to antimicrobials (tetracycline, penicillin, erythromycin, etc.), with resistance genes detected; no association between STs and resistance was found. Isolates with resistance were more common in hand-milked flocks.
Conclusions:
- MLST analysis revealed significant genetic diversity among S. epidermidis causing ovine mastitis in Greece.
- The presence of antimicrobial resistance highlights the need for monitoring and control strategies.
- Hand-milking practices may be associated with a higher prevalence of antimicrobial-resistant S. epidermidis.
