Preliminary Study on Drug Susceptibility Profile and Resistance Mechanisms to Macrolides of Clinical Isolates of Non-tuberculous Mycobacteria from China.

OBJECTIVE: Macrolide susceptibility and drug resistance mechanisms of clinical non-tuberculous mycobacteria (NTM) isolates were preliminarily investigated for more accurate diagnosis and treatment of the infection in China. METHODS: Four macrolides, including clarithromycin (CLAR), azithromycin (AZM), roxithromycin (ROX), and erythromycin (ERY), were used to test the drug susceptibility of 310 clinical NTM isolates from six provinces of China with the broth microdilution method. Two resistance mechanisms, 23S rRNA and erm, were analyzed with nucleotide sequence analysis. RESULTS: Varied effectiveness of macrolides and species-specific resistance patterns were observed. Most Mycobacterium abscessus subsp. massiliense were susceptible and all M. fortuitum were highly resistant to macrolides. All the drugs, except for erythromycin, exhibited excellent activities against slow-growing mycobacteria, and drug resistance rates were below 22.2%. Only four highly resistant strains harbored 2,058/2,059 substitutions on rrl and none of other mutations were related to macrolide resistance. G2191A and T2221C on rrl were specific for the M. abscessus complex (MABC). Seven sites, G2140A, G2210C, C2217G, T2238C, T2322C, T2404C, and A2406G, were specifically carried by M. avium and M. intracellulare. Three sites, A2192G, T2358G, and A2636G, were observed only in M. fortuitum and one site G2152A was specific for M. gordonae. The genes erm(39) and erm(41) were detected in M. fortuitum and M. abscessus and inducible resistance was observed in relevant sequevar. CONCLUSION: The susceptibility profile of macrolides against NTM was demonstrated. The well-known macrolide resistance mechanisms, 23S rRNA and erm, failed to account for all resistant NTM isolates, and further studies are warranted to investigate macrolide resistance mechanisms in various NTM species.

[Molecular subtyping of Vibrio cholerae isolates from outbreaks of cholera by pulsed-field gel electrophoresis in Hainan in 2008].

OBJECTIVE: To analyze the molecular characteristics and genetic correlations of Vibrio cholerae isolates in Hainan in 2008, so as to provide pathogenic proof to diagnose the plague. METHODS: Seventy six cholera strains were isolated from this cholera epidemic.69 strains were obtained from patients, 7 were isolated from external environment, among which, one was from patient's toilet, one from water sample, three were isolated from fish pond near patient's home, one came from swab of the patient vomit on the ground of health center and one from swab of kitchen knife from Hainan University canteen respectively. With conventional aetiological methods, pulse-field gel electrophoresis was conducted and the patterns of the 76 isolates were analyzed. The PFGE image was analyzed using BioNumerics (Version4.0, Applied Maths BVBA, Belium). Image bands were identified and similarity coefficient was automatically generated. RESULTS: Seventy six strains were isolated from Vibrio cholerae outbreaks in Hainan in 2008.5 PFGE patterns of patient's isolates in June were the same, sharing a similarity coefficient of 100%. 70 PFGE patterns of patients and water in October and November were completely same, the similarity coefficient being 100%. But they were not same as that of June. 1 PFGE pattern of isolate from the sample in Hainan University was different, only sharing a similarity coefficient of 79.7%, which showed no correlation with the outbreak. CONCLUSION: Different outbreaks of Vibrio cholera occurred in Hainan in 2008. The epidemic in October and November at different counties was one outbreak. The pollution of water in environment was an important factor for outbreak.