Relationship between the isoniazid-resistant mutation katGS315T and the prevalence of MDR-/XDR-TB in Osaka, Japan.

OBJECTIVE: To determine the prevalence of katGS315T mutations in isoniazid (INH) resistant Mycobacterium tuberculosis and to elucidate the association of katGS315T mutations with the prevalence of multidrug-resistant tuberculosis (MDR-TB). DESIGN: From 2001 to 2004, 1655 isolates from all newly registered patients who visited the Osaka Prefectural Medical Centre for Respiratory and Allergic Diseases were tested for drug susceptibility. Genotyping was performed using insertion sequence (IS) 6110-restriction fragment length polymorphism (RFLP) in 1629 of 1655 (98.4%) cases. All 145 isolates of INH-resistant M. tuberculosis, including MDR strains, were tested to detect the katGS315T mutation. RESULTS: Five hundred and sixty isolates (34.4%) shared an RFLP pattern. Of the 145 INH-resistant isolates, 18/48 (37.5%) isolates belonging to the RFLP cluster had katGS315T and 23/97 (23.7%) did not have the mutation. Of the 66 MDR-TB cases, 18/29 (62.1%) isolates belonging to the RFLP cluster had katGS315T and 11/37 (29.7%) did not have the mutation. Of the 29 extensively drug-resistant (XDR) TB cases, 17/21 (80.9%) isolates belonging to the RFLP cluster had katGS315T and 3/8 (37.5%) did not have the mutation. CONCLUSION: The clustering rate by IS6110-RFLP was very high among MDR-/XDR-TB isolates with katGS315T. Our study indicates a strong correlation between the katGS315T mutation and the transmission dynamics of MDR-TB, and especially XDR-TB.

Comparison of partial ribosomal DNA sequences of Babesia gibsoni occurring in Miyazaki prefecture, Japan.

Nucleotide sequences of ribosomal DNA (rDNA) of Babesia (B.) gibsoni occurring in Miyazaki, western Japan, were examined using blood samples obtained from seven dogs suffering from natural canine babesiosis. DNA isolated from these blood samples was subjected to the polymerase chain reaction (PCR). The nucleotide sequences of the PCR products were determined and compared with other rDNA sequences of B. gibsoni isolated from Asia, Europe and U.S.A. Although homology values between our isolates and those isolated from Europe and U.S.A. were both 84.0%, respectively, our isolates were identical to the Asian types. In conclusion, B. gibsoni occurring in Miyazaki was revealed to have the genotype Asia 1 or Asia 2 from a comparison of the partial rDNA sequences.

Effect of clindamycin therapy on phagocytic and oxidative activity profiles of spleen mononuclear cells in Babesia rodhaini-infected mice.

Spleen weight, the number of spleen mononuclear cells, and their phagocytic activity in groups of Babesia rodhaini-infected mice treated with diminazene diaceturate and clindamycin increased significantly in the early stage of treatment, and then decreased in the final stage of treatment to approximately the pre-infection level. The number of F4/80-positive macrophages and their oxidative activity per mean whole-spleen weight also increased significantly during the course of treatment in comparison with the untreated group. The increases in the clindamycin-treated group were more prominent than those in the group treated with diminazene diaceturate, suggesting the effectiveness of clindamycin therapy for murine babesiosis.

Detection of babesia species from infected dog blood by polymerase chain reaction.

Polymerase chain reaction (PCR) was first applied to diagnosis of canine babesiosis in Japan. Blood samples from 13 dogs suffering from canine babesiosis were used for examination of specificity and sensitivity of the PCR diagnosis. Of the 13 dogs, three were experimentally infected, and ten were naturally infected with Babesia species in west part of Japan. We designed a nested PCR to amplify the babesial small subunit ribosomal RNA gene and found that only the nested PCR produced a visual band, which were not apparent by the first-round PCR to the positive samples. Specificity of the nested PCR was confirmed by amplification after the second-round PCR. Sensitivity of the nested PCR was examined by diluting the blood samples from infected and uninfected dogs. The nested PCR was found to show positive results on the most diluted blood at 0.0001% parasitemia. These results indicate that the nested PCR is highly sensitive and useful for diagnosis of canine babesiosis.

[Comparison of the newly developed MYCOACID system with mycobacteria growth indicator tube (MGIT) and newly developed 2% Ogawa medium (S) for recovery of mycobacteria in clinical specimens].

The detection rate of mycobacteria from patients' specimens and the time required to get positive culture were compared among newly developed MYCOACID SYSTEM, MGIT, Ogawa K medium and 2% Ogawa medium (S). A total of 249 sputum samples taken from patients were used as the study subjects and 124 kinds of mycobacteria were isolated. For 135 cases clinically diagnosed as pulmonary tuberculosis, the detection rate was 44.4% for MYCOACID, 47.4% for MGIT and 38.5% for Ogawa K medium, showing that there are no significant differences in the detection rate between MYCOACID and MGIT, and MYCOACID and Ogawa K medium but the differences was significant between MGIT and Ogawa K medium (p = 0.02). The mean days needed for detection of Mycobacterium tuberculosis complex was 12.3 days for MYCOACID, 13.4 days for MGIT, and 26.8 days for Ogawa K medium, indicating significant differences in the time to get positive culture between Ogawa K medium and either of both liquid media (p < 0.001). Furthermore, 2% Ogawa medium (S) was used only for the detection of mycobacteria among previously untreated tuberculosis and there were no significant differences in the detection rate between 2% Ogawa medium (S) and either of both liquid media. The time to get positive culture for 2% Ogawa medium (S) was 18.2 days, which was longer than that for either of liquid media, MYCOACID and MGIT, but it was significantly shorter (7.9 days) than that for Ogawa K medium (p = 0.003). These results demonstrate that the liquid culture systems both MYCOACID and MGIT were very useful for the detection of mycobacteria compared with Ogawa K medium.

Therapeutic effect of clindamycin and tetracycline on Babesia rodhaini infection in mouse model.

In order to identify the alternative effective chemotherapeutic agents for murine babesiosis, some selected drugs were examined for their efficacy against protozoan infection in the mouse-Babesia rodhaini (B. rodhaini) model. Clindamycin was not completely effective for elimination of parasites in a dose of 50 mg or 100 mg/kg BW/day b.i.d. but effective to prolong the life span of hosts, while it completely cured B. rodhaini infections in a dose of 200 mg. On the other hand, a double therapy consisting of 2 treatments with 100 mg clindamycin and 100 mg clindamycin and with 100 mg clindamycin and 100 mg tetracycline; respectively, and a single therapy with 100 mg tetracycline or 200 mg clindamycin, had a possibility to clear away B. rodhaini organisms from hosts. However, almost all the treatment groups, had a relapse of the infection within 10 days post treatment or re-treatment. Cured mice by treatment with clindamycin and clindamycin, or clindamycin and tetracycline showed complete resistance against challenge with B. rodhaini, while mice cured by administration of clindamycin at 200 mg or tetracycline at 100 mg showed incomplete resistance to challenge infection. The present data suggest that the two former chemotherapies can induce effective protective immunity (premunization), but the latter two chemotherapies induce incomplete premunization.