C A Ison1, N Tekki, M J Gill. 1. Department of Medical Microbiology, St. Mary's Hospital Medical School, Paddington, London, England.
Abstract
BACKGROUND AND OBJECTIVES: Plasmid-mediated high level resistance to tetracycline in Neisseria gonorrhoeae has become a therapeutic problem in many parts of the world. Simple, fast and accurate screening tests are required to enable rapid detection. GOAL OF THE STUDY: To evaluate screening tests for high-level tetracycline resistance for their ability to predict the presence of the tetM determinant in Neisseria gonorrhoeae. STUDY DESIGN: Strains considered to exhibit plasmid-mediated (90) and chromosomal resistance (19) to tetracycline were used to compare the screening tests, growth on tetracycline agar, disc testing, MIC and plasmid content, with confirmation by hybridization to the tetM probe. A polymerase chain reaction to amplify tetM in N. gonorrhoeae was also evaluated. RESULTS: All strains defined as presumptive TRNG by the screening tests hybridized with the tetM probe. None of the low-level resistant strains were positive in the screening tests or hybridized with the probe. In addition, the polymerase chain reaction (PCR) on whole bacterial cells detected tetM in all TRNG tested. Restriction enzyme digests of the PCR product gave three patterns suggesting genetic diversity within the tetM determinant of N. gonorrhoeae. CONCLUSION: Simple screening tests were found to be reliable predictors of TRNG. tetM was detected by PCR in all strains tested and exhibited some genetic variation that may be of use for epidemiological typing.
BACKGROUND AND OBJECTIVES: Plasmid-mediated high level resistance to tetracycline in Neisseria gonorrhoeae has become a therapeutic problem in many parts of the world. Simple, fast and accurate screening tests are required to enable rapid detection. GOAL OF THE STUDY: To evaluate screening tests for high-level tetracycline resistance for their ability to predict the presence of the tetM determinant in Neisseria gonorrhoeae. STUDY DESIGN: Strains considered to exhibit plasmid-mediated (90) and chromosomal resistance (19) to tetracycline were used to compare the screening tests, growth on tetracycline agar, disc testing, MIC and plasmid content, with confirmation by hybridization to the tetM probe. A polymerase chain reaction to amplify tetM in N. gonorrhoeae was also evaluated. RESULTS: All strains defined as presumptive TRNG by the screening tests hybridized with the tetM probe. None of the low-level resistant strains were positive in the screening tests or hybridized with the probe. In addition, the polymerase chain reaction (PCR) on whole bacterial cells detected tetM in all TRNG tested. Restriction enzyme digests of the PCR product gave three patterns suggesting genetic diversity within the tetM determinant of N. gonorrhoeae. CONCLUSION: Simple screening tests were found to be reliable predictors of TRNG. tetM was detected by PCR in all strains tested and exhibited some genetic variation that may be of use for epidemiological typing.