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Tetracycline‐resistant propionibacteria from acne patients are cross‐resistant to doxycycline, but sensitive to minocycline
Author(s) -
EADY E.A.,
JONES C.E.,
GARDNER K.J.,
TAYLOR J.P.,
COVE J.H.,
CUNLIFFE W.J.
Publication year - 1993
Publication title -
british journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.304
H-Index - 179
eISSN - 1365-2133
pISSN - 0007-0963
DOI - 10.1111/j.1365-2133.1993.tb00235.x
Subject(s) - minocycline , doxycycline , tetracycline , acne , medicine , antibiotics , minimum inhibitory concentration , gastroenterology , microbiology and biotechnology , dermatology , biology
Summary Antibiotic‐resistant propionibacteria are being isolated with increasing frequency from antibiotictreated acne patients. Minimum inhibitory concentrations (MICs) of three tetracyclines, extensively used in acne therapy, were determined for 46 resistant and 19 sensitive propionibacterial isolates. Sensitive strains were inhibited by ≤1 μ/ml of all three tetracyclines. For every resistant strain tested, the MIC of tetracycline exceeded that of doxycycline which, in turn, exceeded that of minocycline. The mean MIC for resistant strains was 20.61±4.56 μ/ml of tetracycline, 9.70±2.03 μ/ml of doxycycline and 1.95±0.35 μ/ml of minocyciine. In order to determine whether these strains could be inhibited by concentrations of minocycline achievable in vivo , serum levels of minocycline were determined in acne patients receiving either the recommended dose of 50 mg b.d. (20 males, 14 females), or twice this dose (21 males, 12 females). Serum levels were significantly higher ( P <0.001, Student's t ‐test) in patients receiving 100 mg b.d. Males on 50 mg h.d. had significantly lower serum levels than females on the same dose ( P <0.05. Student's t ‐test). For all patients, the mean serum level on high‐dose minocycline was 246±0.45 μ/ml, compared with 1.38±0.30 μ/ml on the smaller dose. These results indicate that tetracycline‐resistant propionibacteria should be considered clinically minocycline sensitive, if patients who harbour such strains are prescribed 100 mg b.d. The recommended dose of minocycline for treating acne, especially in male patients, should be re‐assessed.