Distribution of rpoB mutations among multidrug-resistant Mycobacterium tuberculosis (MDRTB) strains from Thailand and development of a rapid method for mutation detection

Since rifampicin resistance is a surrogate marker for multidrug-resistant Mycobacterium tuberculosis (MDRTB), the present study aimed to investigate rpoB mutations conferring rifampicin resistance in M. tuberculosis strains from Thailand, and to develop a rapid, inexpensive and simple PCR-based method for rapid detection of MDRTB. Overall, 267 M. tuberculosis isolates, including 143 MDRTB isolates, were investigated. Isolates of the Beijing strain predominated among the MDRTB isolates (79.1%), but accounted for only 45.5% of the susceptible isolates. Mutations in the rpoB gene were found most commonly at codons 531, 526 and 516 (58%, 25.2% and 9.1%, respectively). A multiplex allele-specific PCR was developed and tested with 216 clinical isolates. In comparison with the proportion method, the method showed 94.2% sensitivity and 100% specificity, and had a 100% positive predictive value and a 95% negative predictive value, which suggested that this method could be useful for screening for MDRTB, particularly in resource-limited countries.

Second-line drug susceptibilities of Thai multidrug-resistant Mycobacterium tuberculosis isolates

The emergence of multidrug-resistant tuberculosis (MDR-TB) is increasing and is exacerbated by the human immunodeficiency virus (HIV) epidemic. The standard short-course regimen used for the treatment of tuberculosis is likely to be ineffective against MDR-TB, leading to the need for second-line drugs. In such situations, drug susceptibility testing (DST) is necessary to select an appropriate treatment regimen. In this study, DST of 99 MDR-TB strains isolated in Thailand was performed using a drug-impregnated disc method. The results showed that 94.95% of the strains were susceptible to amikacin and kanamycin, 90.91% to ciprofloxacin and ofloxacin, 85.86% to para-aminosalicylic acid, and 78.79% to ethionamide.

Genotypic subtyping of the HIV-1 polymerase gene in 30 naåve patients from Thailand

To investigate the subtype classification of the circulating virus strains among infected Thai patients with human immunodeficiency virus type 1 (HIV-1). A random population of patients who were HIV-1 antibody positive after two independent screening assays was selected. HIV RNA from plasma samples was reverse-transcribed and amplified with specific primers that annealed to conserve regions of the HIV-1 pol gene. Amplified products were sequenced directly by using an automated sequencer. The sequencing products represent about 1.2 kb of the pol gene from each patient and they were phylogenetically analyzed and compared to the corresponding pol sequences of the published HIV-1 sequences of known genotypes. Genotype E was found in 25 of 30 patients (83.3%), and 5 patients (16.7%) were HIV-1 genotype B. The result confirmed that HIV-1 subtype E is still predominant in Thailand. Genotype B is found frequently, but there have been no examples of genotype A. In concordance with the serotypic assay, which was previously reported using the V3-peptide enzyme immunoassay (V3-PEIA), the genotypic assay of subtype E was high, at 80% and 83.3% in serotyping and genotyping, respectively. These findings of two subtypes with low heterogeneity indicate that Thailand may be a desirable site for evaluating candidate HIV-1 antiretroviral drugs and vaccines. The mixture of subtype E and B' strains also offers the opportunity to study phenotypic differences between the two subtypes.

Spontaneous resolution of mediastinal pancreatic pseudocyst

We report the findings in a 39-year-old man with alcoholic pancreatitis and a lower posterior mediastinal mass. Endoscopic retrograde pancreatographic and ultrasonographic studies permitted an unequivocal diagnosis of mediastinal pancreatic pseudocyst. The pseudocyst resolved spontaneously five weeks after diagnosis, without specific therapy.