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Updated: Sep 10, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Susceptibility of staphylococci and enterococci to glycopeptides comparison of 3 test methods
B Jansen1, F Schumacher-Perdreau, G Pulverer
1Institute of Medical Microbiology and Hygiene, University of Cologne, Köln, Germany.
Abstract:
The significance of grampositive bacteria, especially staphylococci and enterococci, as nosocomial pathogens has increased in the last decade. Furthermore, resistance to commonly used antibiotics like beta-lactams has also become more common and even resistance to glycopeptides has been observed. We evaluated the susceptibility of 150 staphylococcal clinical isolates (52 S. epidermidis, 52 S. haemolyticus, 10 S. saprophyticus, 10 S. hominis, 4 S. warneri, 4 S. simulans, 4 S. capitis and 14 S. aureus) and of 50 enterococci (49 E. faecalis, 1 E. faecium) to the glycopeptides, vancomycin and teicoplanin. The data from the agar dilution test used as reference method were compared with the results from the E test and the agar disk diffusion test. Concerning vancomycin, no resistance among all the staphylococcal isolates was observed whereas one single enterococcal strain (E. faecium) proved to be resistant. The overall resistance of staphylococcal isolates against teicoplanin was about 10.7% (15 S. haemolyticus, 1 S. epidermidis) being mainly due to the high proportion of S. haemolyticus strains (52 out of 150) among the staphylococcal isolates. Teicoplanin resistance among the enterococci was not detected. For vancomycin, a very close correlation between the MICs from the agar dilution test and the E test was noticed. As concerns teicoplanin, the MICs from the E-test were usually somewhat lower than those obtained by the agar dilution test. No correlation was found between the MICs of resistant and intermediate staphylococcal strains and the results from the teicoplanin agar disk diffusion test. For routine teicoplanin susceptibility testing of staphylococci, the determination of the MIC (e.g., by the E test) is much more reliable for detecting resistant strains than the agar disk diffusion test.
Insights
Gram-positive bacteria like staphylococci and enterococci are increasing nosocomial pathogens. This study found vancomycin resistance rare in staphylococci but present in one enterococcus, while teicoplanin resistance was observed in staphylococci, particularly S. haemolyticus.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Gram-positive bacteria, particularly staphylococci and enterococci, are significant causes of hospital-acquired infections.
- Increasing antibiotic resistance, including to beta-lactams and glycopeptides, poses a major challenge in treating these infections.
Purpose of the Study:
- To evaluate the susceptibility of clinical isolates of staphylococci and enterococci to vancomycin and teicoplanin.
- To compare the accuracy of E test and agar disk diffusion methods against the agar dilution reference method for susceptibility testing.
Main Methods:
- Agar dilution, E test, and agar disk diffusion methods were used to determine the minimum inhibitory concentrations (MICs) of vancomycin and teicoplanin.
- 150 staphylococcal isolates (including S. epidermidis, S. haemolyticus, S. aureus) and 50 enterococcal isolates (E. faecalis, E. faecium) were tested.
Main Results:
- No vancomycin resistance was observed in staphylococci; one Enterococcus faecium isolate was resistant.
- Teicoplanin resistance was detected in 10.7% of staphylococcal isolates, primarily S. haemolyticus.
- The E test showed good correlation with agar dilution for vancomycin but yielded lower MICs for teicoplanin.
- Agar disk diffusion was unreliable for detecting teicoplanin resistance in staphylococci.
Conclusions:
- Vancomycin remains effective against most staphylococci, but resistance in enterococci is a concern.
- Teicoplanin resistance is present in staphylococci, necessitating reliable susceptibility testing methods.
- The E test is a more reliable method than agar disk diffusion for routine teicoplanin susceptibility testing of staphylococci.
