|Year : 2018 | Volume
| Issue : 1 | Page : 119-120
In vitro analysis of the minimal inhibitory concentration values of different generations of anti-methicillin-resistant Staphylococcus aureus antibiotics
Aneta Guzek1, Zbigniew Rybicki2, Dariusz Tomaszewski2
1 Department of Microbiology, Military Institute of Medicine, Warsaw, Poland
2 Department of Anaesthesiology and Intensive Therapy, Military Institute of Medicine, Warsaw, Poland
|Date of Web Publication||2-May-2018|
Dr. Dariusz Tomaszewski
Department of Anaesthesiology and Intensive Therapy, Military Institute of Medicine, Szaserow 128 Street, 04-141 Warsaw
Source of Support: None, Conflict of Interest: None
Methicillin-resistant Staphylococcus aureus (MRSA) resistance to antimicrobials may result in the increased risk of treatment failure. The objective of the study was to analyse in vitro MRSA susceptibility to vancomycin, linezolid, daptomycin, tigecycline, ceftaroline, dalbavancin, clindamycin, ciprofloxacin and trimethoprim/sulfamethoxazole. All MRSA strains isolated from hospitalised patients were analysed according to the current microbiological recommendations. Finally, a total of 124 MRSA strains were analysed; all were susceptible to tested antibiotics. Dalbavancin had the lowest minimum inhibitory concentration (MIC), and vancomycin the highest MIC value. There were 28/124 strains of MRSA susceptible for clindamycin, 36/124 for ciprofloxacin and 121/124 for trimethoprim/sulfamethoxazole. Dalbavancin was the most effective antimicrobial in our study.
Keywords: Anti-methicillin-resistant Staphylococcus aureus antibiotics, methicillin-resistant Staphylococcus aureus, minimal inhibitory concentration
|How to cite this article:|
Guzek A, Rybicki Z, Tomaszewski D. In vitro analysis of the minimal inhibitory concentration values of different generations of anti-methicillin-resistant Staphylococcus aureus antibiotics. Indian J Med Microbiol 2018;36:119-20
|How to cite this URL:|
Guzek A, Rybicki Z, Tomaszewski D. In vitro analysis of the minimal inhibitory concentration values of different generations of anti-methicillin-resistant Staphylococcus aureus antibiotics. Indian J Med Microbiol [serial online] 2018 [cited 2018 Nov 15];36:119-20. Available from: http://www.ijmm.org/text.asp?2018/36/1/119/231659
| ~ Introduction|| |
Methicillin-resistant Staphylococcus aureus(MRSA) pathogens are resistant to almost all β-lactam antibiotics as well as being, in part, resistant to aminoglycosides, tetracyclines, macrolides, lincosamides and trimethoprim/sulfamethoxazole. As a result, the risk of treatment failure increases, especially in cases of the catheter-related blood infections and pneumonia.
The aim of this study was to analyse in vitro MRSA susceptibility to different generations of anti-MRSA antibiotics (vancomycin, linezolid, daptomycin, tigecycline, ceftaroline, dalbavancin, clindamycin, ciprofloxacin and trimethoprim/sulfamethoxazole).
| ~ Methods|| |
We analysed MRSA strains isolated from patients hospitalised in our centre. Only one, the first isolate per patient was included in the analysis.
Isolates of S. aureus were identified based on colony morphology, Gram stain characteristics, the positive tube coagulase test and a VITEK 2 automated system (bioMérieux, France).
Resistance to methicillin was confirmed with the Mueller-Hinton agar diffusion procedure with 30 μg cefoxitin disk according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST).
Minimum inhibitory concentration (MIC) values were determined by gradient stripes E-test (bioMérieux, France) for vancomycin, linezolid, daptomycin, tigecycline, ceftaroline and for dalbavancin (Liofilchem, Italy) according to manufacturer's instructions.
Pathogens' susceptibility tests to clindamycin, ciprofloxacin and trimethoprim/sulfamethoxazole were performed with AST-P644 card by VITEK 2 system.
Reference strains S. aureus ATCC 29213 and S. aureus ATCC 43300 were used as controls.
A microorganism was defined as clinically susceptible or clinically resistant to an antimicrobial agent according to the EUCAST clinical breakpoints.
| ~ Results|| |
Between May 2012 and January 2014, a total of 124 MRSA strains were isolated from wounds (93 swabs), abscesses (11), ulcers (9), fistulas (5) and from blood samples (6). All analysed strains of MRSA were susceptible to tested antibiotics. The MIC values of analysed antimicrobial agents were shown in [Table 1].
|Table 1: Distribution of vancomycin, linezolid, daptomycin, tigecycline, dalbavancin, and ceftaroline MIC values (μg/mL) against MRSA strains|
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There were only 28/124 (22.6%) strains of MRSA susceptible for clindamycin and 36/124 (29.0%) susceptible for ciprofloxacin in our material. Most of the isolated MRSA strains (121/124, 97.6%) were susceptible for trimethoprim/sulfamethoxazole.
| ~ Discussion|| |
In the last year, the increase in MIC values to vancomycin was observed, and administration of higher doses of this drug is necessary to achieve its therapeutic serum concentrations, especially in patients suffering from pneumonia caused by MRSA. However, MIC value of vancomycin above 1 μg/mL significantly predicts treatment failure and mortality.
The lowest MIC value had dalbavancin. This antimicrobial, with the convenient administration and long duration of action, is as effective as vancomycin in skin and subcutaneous tissue infections. Moreover, dalbavancin successfully reduced MRSA in biofilm, which can be useful in biofilm-associated infections.
In our study, MIC values of vancomycin for 45 of 124 (36.2%) strains of MRSA were 1.5 μg/L. This value (MIC-creep) is related to significant increase of mortality in cases of infection caused by MRSA.
The MIC values of daptomycin and linezolid were lower than MIC of vancomycin. The observations of Molina and Huang  were similar, suggesting that the role of vancomycin in the treatment of serious S. aureus infections becomes ineffective.
Such antimicrobials as clindamycin, ciprofloxacin and trimethoprim/sulfamethoxazole have its role in community-acquired MRSA infections. However, the utility of ciprofloxacin is quite limited, because the bacterial resistance to ciprofloxacin rapidly increases. Moreover, patients to whom clindamycin is administered are at risk of Clostridium difficile infections.
According to many recommendations, vancomycin is an antimicrobial of the first choice in the treatment of MRSA infections. Maybe, it is a time to re-evaluate this.
Financial support and sponsorship
Own funds of the Military Institute of Medicine, Warsaw, Poland.
Conflicts of interest
There are no conflicts of interest.
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