Akademik Veri Yönetim Sistemi
2. Uluslararası Sağlık Bilimleri Kongresi, Tekirdağ, Türkiye, 15 - 17 Kasım 2018, ss.15-16
Introduction
and Aim
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-acquired
infections worldwide (1-3). This pathogen may develop resistance to almost all
antibiotics, thereby complicating infection management (1-4). After first being
reported in 1961, methicillin-resistant S.
aureus (MRSA) has become endemic in hospitals worldwide, rendering the
entire β-lactam class of antibiotics ineffective (2-4). Over the last few
decades, especially in nosocomial environments, multiple antibiotic resistant
MRSA have been a huge increase and emergence. In addition to antibiotic
resistance, toxins contributing to bacterial virulence have a significant role
in pathogenesis of MRSA infections (2-4). S.
aureus have been well documented to produce a variety of extracellular
protein toxins including enterotoxins, toxic shock syndrome toxin-1,
exfoliative toxin, hemolysins and coagulase (1). The production of
multiple virulence factors, as well as the presence of antibiotic resistance,
makes this microorganism a highly succesful human pathogen.
In this study, we aimed
to determine the toxigenic properties and antibiotic susceptibility profiles of
MRSA isolated from various clinical samples.
Materials
and Methods
A total of 27 MRSA
isolates from various clinical samples were included in this study.
Identification of the isolates was performed by MALDI-TOF MS (Vitek MS,
bioMérieux, France) and antibiotic susceptibility was determined by using an
automated system (VITEK 2 Compact, bioMérieux). Total bacterial DNA was
isolated from colonies on 5% sheep blood agar plates grown overnight. We used PCR amplification with appropriate
reaction steps to detect the toxin genes encoding for Panton-Valentine
leukocidin (PVL, luk S/F), toxic
shock toxin 1 (tst) and
staphylococcal enterotoxins (sea, sed).
PCR products were analysed with gel electrophoresis and detected bands were
evaluated comparing their size with DNA mass-ladder.
Results
Most of the study
isolates (n=16, 59.2%) obtained from intensive-care units. The examined
clinical samples were as follows; blood (n=19), respiratory specimens (n=6) and
sterile body fluid samples (n=2). Twenty-three isolates (23/27; 85.2%) were
detected positive for one or more toxin genes. Seventeen isolates (62.9%) were
carrying both PVL and sea. PVL and sea toxin genes were detected in 6
isolates (3 isolates were found positive for each gene). The sed and tst genes could not be detected in any of the isolates.
Regarding to antibiotic susceptibility, all isolates
were found to be sensitive to linezolid and vancomycin. Resistance rates
against other tested antibiotics ranged from 7.4% to 88.9%. Most prominent
resistance rates were levofloxacin (88.9%), tetracycline (85.2%), erythromycin
(77.8%), gentamicin and rifampicin (74.1%) and clindamycin (63.0%).
In isolates carrying PVL and sea
together, resistance to teicoplanin was found to be 29.4%, also two daptomycin
resistant isolates were in this group.
Conclusion
In our study, toxin
production rate in clinical MRSA isolates was found to be as high as 85.2%.
Among the toxin-positive isolates, PVL and sea
carriers have a significant share (62.9%). PVL, one of the most severe S. aureus toxins, being the most common
(74%) amongst all of the isolates. S.
aureus strains that are positive for PVL production are usually associated
with skin and soft-tissue infections, and were first isolated in the 1960s.
Sina et al. reported similar findings
regarding to PVL detection rate (70%) and antibiotic resistance such as
rifampicin (67%), tetracycline (60%) (5). However, the rate of trimetroprim/sulfamethoxazol
resistant isolates (57%) was significantly higher compared to our results
(7.5%). Interestingly, antibiotic resistance rates are especially
high in our study isolates carrying PVL and sea.
Monitoring of toxigenic properties and antibiotic resistance, and analysing the
relationship between those have an importance regarding to public health. In addition to toxin production capability
and antibiotic susceptibility profiles, identification of the clonal relationship
of these isolates and monitoring of spread in the hospital environment would be
beneficial in terms of infection control.