+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Detection of borderline oxacillin-resistant Staphylococcus aureus and differentiation from methicillin-resistant strains



Detection of borderline oxacillin-resistant Staphylococcus aureus and differentiation from methicillin-resistant strains



European Journal of Clinical Microbiology and Infectious Diseases 9(10): 717-724



Eighty-eight Staphylococcus aureus clinical isolates meeting criteria for borderline oxacillin resistance (intermediate susceptibility or resistance to oxacillin but susceptibility to amoxicillin/clavulanic acid upon disk diffusion testing) were studied to determine optimal test techniques and conditions for differentiating borderline oxacillin-resistant Staphylococcus aureus (BORSA) from methicillin-resistant Staphylococcus aureus (MRSA). Further testing revealed three distinct resistance patterns: 61 strains (69%) consistently met BORSA criteria and had average beta-lactamase levels five- to six-fold higher than oxacillin-susceptible controls; 11 strains (13%) were markedly heteroresistant MRSA with delayed appearance of resistant colonies leading to spurious susceptibility to amoxicillin/clavulanic acid; 16 strains (18%) appeared to be oxacillin-susceptible on repetitive testing. Under conditions used to elicit intrinsic methicillin resistance in Staphylococcus aureus, a large percentage of BORSA appeared resistant to amoxicillin/clavulanic acid. This clearly shows that BORSA may be misidentified as MRSA while heteroresistant MRSA may appear to be BORSA. It is concluded that amoxicillin/clavulanic acid zone sizes should be measured after a full 24 hours of incubation, that susceptibility testing of Staphylococcus aureus under certain environmental conditions should be interpreted with caution, and that MIC testing is the most reliable technique for differentiating these two resistance patterns in Staphylococcus aureus.

Please choose payment method:






(PDF emailed within 1 workday: $29.90)

Accession: 039774244

Download citation: RISBibTeXText

PMID: 2261916


Related references

The differential detection of methicillin-resistant, methicillin-susceptible and borderline oxacillin-resistant Staphylococcus aureus by surface plasmon resonance. Biosensors and Bioelectronics 49: 334-340, 2014

Evaluation of the MRSA-Screen Latex Agglutination Test for detection of methicillin-resistant Staphylococcus aureus, and performance against borderline oxacillin-resistant isolates. Abstracts of the Interscience Conference on Antimicrobial Agents & Chemotherapy 43: 180, 2003

Detection of borderline oxacillin-resistantStaphylococcus aureusand differentiation from methicillin-resistant strains. European Journal of Clinical Microbiology & Infectious Diseases 9(10): 717-724, 1990

Disk with high oxacillin content discriminates between methicillin-resistant and borderline methicillin-susceptible Staphylococcus aureus strains in disk diffusion assays using a low salt concentration. Journal of Clinical Microbiology 37(6): 2047-2050, 1999

Frequency of mecA gene and borderline oxacillin resistant Staphylococcus aureus in nosocomial acquired methicillin resistance Staphylococcus aureus infections. Pakistan Journal of Biological Sciences 11(9): 1282-1285, 2008

Comparison of seven agglutination systems, and the slide and tube coagulase tests for the rapid identification of methicillin-resistant and borderline methicillin-resistant strains of Staphylococcus aureus. Abstracts of the General Meeting of the American Society for Microbiology 96(0): 67, 1996

Detection of methicillin/oxacillin resistance and typing in aminoglycoside-susceptible methicillin-resistant and kanamycin-tobramycin-resistant methicillin-susceptible Staphylococcus aureus. Microbial Drug Resistance 12(3): 177-185, 2006

Comparison of conventional susceptibility tests with direct detection of penicillin-binding protein 2a in borderline oxacillin-resistant strains of Staphylococcus aureus. Antimicrobial Agents and ChemoTherapy 35(12): 2574-2579, 1991

Phage pattern-specific oxacillin-resistant and borderline oxacillin-resistant Staphylococcus aureus in U.S. hospitals: epidemiological significance. Journal of Clinical Microbiology 30(1): 252-254, 1992

Mupirocin resistance among consecutive isolates of oxacillin-resistant and borderline oxacillin-resistant Staphylococcus aureus at a university hospital. Antimicrobial Agents and ChemoTherapy 38(7): 1664-1667, 1994

Emergence of multidrug-resistant sequence type 45 strains among mecA-positive borderline oxacillin-resistant Staphylococcus aureus causing bacteraemia in a medical centre in Taiwan. International Journal of Antimicrobial Agents 52(1): 70-75, 2018

Analysis of borderline-resistant strains of methicillin-resistant Staphylococcus aureus using polymerase chain reaction. Microbiology and Immunology 36(5): 445-453, 1992

Oxacillin sensitization of methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus pseudintermedius by antisense peptide nucleic acids in vitro. Bmc Microbiology 15: 262, 2016

Identification of two borderline oxacillin-resistant strains of Staphylococcus aureus from routine nares swab specimens by one of three chromogenic agars evaluated for the detection of MRSA. American Journal of Clinical Pathology 134(6): 921-927, 2010

Molecular characterization of borderline oxacillin-resistant Staphylococcus aureus strains. Abstracts of the General Meeting of the American Society for Microbiology 98: 47, 1998