In vitro susceptibility of clinical isolates of Mycobacterium tuberculosis to cefadroxil - a cephalosporin antibiotic.

Selvakumar, N.; Vanaja Kumar; Paramasivan, C.N.

Indian Journal of Medical Research; 1997; 105; 58-60.

The bactericidal activity (BA) of cefadroxil, a semisynthetic cephalosporin antibiotic, against M. tuberculosis H 37 Rv was studied in Middlebrook 7H9 medium. Cefadroxil showed good BA (average fall of viable counts = log 10 0.32 colony forming units/ml/day) against the log phase culture of M. tuberculosis H 37 Rv. Its minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were found to be 15 mg/ml or less. The MIC of cefadroxil for 29 clinical isolates of M. tuberculosis and a laboratory strain, M. tuberculosis H 37 Rv was also determined by agar dilution method using Middlebrook 7H11 agar as a screening procedure. The MIC of cefadroxil was found to be 10 mg/ml or less for M. tuberculosis H 37 Rv and 16 (55.1%) of 29 clinical isolates tested. The MIC for 3 of 10 drug sensitive and 9 of 19 drug resistant isolates was 40 or more, a concentration much higher than the peak plasma concentration (28 mg/ml) attained in human beings. The higher MIC observed in 12 of 29 clinical isolates irrespective of their susceptibility pattern requires further studies to assess the usefulness of cefadroxil in the treatment of tuberculosis.

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