A Study On The Condition Of Drug Susceptibility For Mycobacterium Tuberculosis

Purpose: To assess the drug susceptibility for Mycobacteriumtuberculosis, discuss factors influencing drug resistance toMycobacterium tuberculosis, and provide evidence for a reasonable drugselection in clinical use.Methods: 322 sputum specimens, positive for Mycobacteriumtuberculosis in culture, were collected from all in-patient cases oftuberculosis from January to December 2006 in a third-referral hospital ofChangsha. Cultured Mycobacterium tuberculosis bacilli were typed byPNB and TCH using absolute concentration in modified acid-fast media,and were used for testing drug susceptibility. Data were analyzed bySPSS13.0 statistical software.Results: Among 322 sputum samples containing Mycobacteriumtuberculosis, 264 were from patients of primary tuberculosis, while 58from patients of recurrent tuberculosis. In the former group, the rate ofdrug resistance to eleven common anti-tuberculosis medicationsincluding rifampin, streptomycin, isoniazid, ethambutol, pyrazinamide,rifapentine, kanamycin, prothionamide, ofloxacin, para-aminosalicylicacid, and levofloxacin was 12.88%,20.45%,18.94%,6.06%,5.68%,9.85%,10.61%,7.58%,5.68%,5.30%,and 0.38%, respectively, withstreptomycin, isoniazid and rifampin being the top three of the most resistible drugs. In the latter group, the rate of resistance to elevenaforementioned drugs was 51.72%,34.48%,43.10%,25.86%,20.69%,43.10%,12.07%,20.69%,12.07%,10.34%,and 1.72%, respectively,with rifampin, isoniazid and rifapentine being the top three drugs.Comparing sputum samples from primary versus recurrent tuberculosisevaluated by x~2 test, there was a statistically significant difference in thefrequency of drug resistance to seven tested drugs listed as follows:rifampin (P＜0.001),streptomycin (P＜0.05),isoniazid (P＜0.001),ethambutol (P＜0.001),pyrazinamide (P＜0.001),rifapentine (P＜0.001),and prothionamide (P＜0.01). The rate of multi-drug resistance in primarytuberculosis and recurrent tuberculosis was 5.68% and 37.93%,respectively; such a difference was statistically significant by x2 test.Furthermore, by foursquare pair x~2 test, with the exception of levofloxacin,the rate of resistance of eleven aforementioned drugs was significantlydifferent at high versus low concentration.Conclusions: Currently, the problem of drug resistance was noted inall anti-tuberculosis medications to various degrees. This studydemonstrated that the top three highly-resisted drugs were isoniazid,streptomycin and rifampin. Seven drugs including rifampin (P＜0.001),streptomycin (P＜0.05),isoniazid (P＜0.001),ethambutol (P＜0.001),pyrazinamide (P＜0.001),rifapentine (P＜0.001),and prothionamide hadmore resistance when used for recurrent tuberculosis than primary tuberculosis. All anti-tuberculosis medications were less resistant whenused at higher concentrations. Routine mycobacterial culture and drugsusceptibility test were helpful in selecting anti-tuberculosis drugs in ascientific, reasonable and effective manner. Such tests also hadepidemiological significance for managing tuberculosis as well as forcontrolling spread of tuberculosis.