Frequency and clinical course of invasive pneumococcal disease caused by penicillin-resistant and penicillin-sensitive Streptococcus pneumoniae in Thai children.

OBJECTIVE: This study assessed clinical differences between invasive pneumococcal disease (IPD) caused by penicillin-resistant and penicillin-sensitive Streptococcus pneumoniae. MATERIAL AND METHOD: Patients with IPD confirmed during January 1996-December 2007 at three hospitals were included. Clinical characteristics and outcomes were compared between patients infected with penicillin-resistant Streptococcus pneumoniae (PRSP) and penicillin-sensitive Streptococcus pneumoniae (PSSP). RESULTS: Sixty-nine patients with IPD were identified during the study period, 20 (29%) of whom were infected with PRSP and 49 (71%) with PSSP. Sex, mean age, underlying diseases and seasonal variation did not differ statistically between the two groups. No significant differences were identified in clinical course as measured by time until defervescence, duration of hospitalization and clinical outcome. Minimum inhibitory concentrations (MIC) for other antibiotics were determined; 20% and 10% of PRSP isolates were nonsusceptible to cephalosporins and meropenem, respectively, but all isolates were sensitive to vancomycin. CONCLUSION: There were no significant differences identified in the clinical epidemiology of lPD cases caused by PRSP and PSSP.

Incidence of pneumococcal bacteremia requiring hospitalization in rural Thailand.

BACKGROUND: Population-based estimates of the incidence of invasive pneumococcal disease are unavailable for Thailand and other countries in Southeast Asia. We estimated the incidence of pneumococcal bacteremia cases requiring hospitalization in rural Thailand. METHODS: Blood cultures were performed on samples from hospitalized patients in 2 rural provinces where active, population-based surveillance of community-acquired pneumonia is conducted. Blood cultures were performed at clinician discretion and were encouraged for all patients with suspected pneumonia and all children aged <5 years with suspected sepsis. Pneumococcal antigen testing was performed on positive blood culture specimens that failed to grow organisms on subculture. RESULTS: From May 2005 through June 2007, 23,853 blood culture specimens were collected overall, and 7319 were collected from children aged <5 years, which represented 66% and 47% of target patients, respectively. A total of 72 culture-confirmed pneumococcal bacteremia cases requiring hospitalization were identified. An additional 44 patients had media from positive blood cultures that yielded no growth on subculture but that had positive results of pneumococcal antigen testing. Of the 116 confirmed cases of bacteremia, 27 (23%) occurred in children aged <5 years; of these, 9 (33%) were confirmed by antigen testing only. The incidence of pneumococcal bacteremia cases requiring hospitalization among children aged <5 years had a range of 10.6-28.9 cases per 100,000 persons (incidence range if cases detected by antigen are excluded, 7.5-14.0 cases per 100,000 persons). CONCLUSIONS: Invasive pneumococcal disease is more common than was previously suspected in Thailand, even on the basis of estimates limited to hospitalized cases of bacteremia. These estimates, which are close to estimates of the incidence of hospitalized cases of pneumococcal bacteremia in the United States before introduction of pneumococcal conjugate vaccine, provide important data to guide public health care policy and to inform discussions about vaccine introduction in Thailand and the rest of Southeast Asia.

Multi-probe real-time PCR identification of common Mycobacterium species in blood culture broth.

Mycobacterium tuberculosis complex, M. avium, and M. intracellulare are the most common causes of systemic bacterial infection in AIDS patients. To identify these mycobacterial isolates in primary blood culture broths, we developed a multiple hybridization probe-based real-time PCR assay using the LightCycler system. The primers were designed to amplify a 320-bp fragment of Mycobacterium 16S rRNA genes. Reaction specificity was evaluated using PCR amplification curves along with specific melting temperatures of probes on DNA extracted from 13 Mycobacterium species. In this study, results showed 100% accuracy for the selected bacterial panel. Detection limits were 350, 600, and 650 colony-forming unit (CFU)/ml blood culture broths for M. tuberculosis complex, M. avium, and M. intracellulare, respectively (1 to 2 CFU/reaction). To evaluate clinical applicability, 341 acid-fast bacilli in blood culture broths were analyzed. In total, 327 (96%) were positively identified: 54.5% M. tuberculosis complex, 37.5% M. avium, and 3.8% M. intracellulare. Results can be available within 3 hours of receiving a broth sample, which makes this rapid and simple assay an attractive diagnostic tool for clinical use.

Evaluation of a cytolethal distending toxin (cdt) gene-based species-specific multiplex PCR assay for the identification of Campylobacter strains isolated from poultry in Thailand.

We have recently developed a cytolethal distending toxin (cdt) gene-based species-specific multiplex PCR assay for identifying Campylobacter jejuni, C. coli and C. fetus. In the present study, the applicability of this assay was evaluated with 34 Campylobacter-like organisms isolated from poultry in Thailand for species identification and was compared with other assays including API Campy, 16S rRNA gene sequence, and hippuricase (hipO) gene detection. Of the 34 strains analyzed, 20, 10 and 1 were identified as C. jejuni, C. coli, and Arcobacter cryaerophilus, respectively, and 3 could not be identified by API Campy. However, 16S rRNA gene analysis, showed that all 34 strains are C. jejuni/coli. To discriminate between these 2 species, the hipO gene, which is specifically present in C. jejuni, was examined by PCR and was detected in 20 strains, which were identified as C. jejuni by API Campy but not in the remaining 14 strains. Collective results indicated that 20 strains were C. jejuni whereas the 14 strains were C. coli. When the cdt gene-based multiplex PCR was employed, however, 19, 20 and 19 strains were identified as C. jejuni while 13, 14 and 13 were identified as C. coli by the cdtA, cdtB and cdtC gene-based multiplex PCR, respectively. Pulsed-field gel electrophoresis revealed that C. jejuni and C. coli strains analyzed are genetically diverse. Taken together, these data suggest that the cdt gene-based multiplex PCR, particularly cdtB gene-based multiplex PCR, is a simple, rapid and reliable method for identifying the species of Campylobacter strains.

Multiple mutations in katG and inhA identified in Thai isoniazid-resistant Mycobacterium tuberculosis isolates.

A total of 29 Thai multi-drug-resistant/isoniazid-resistant Mycobacterium tuberculosis isolates were analyzed for mutations in katG from codons 254 to 549, inhA promoter and inhA open reading frame by DNA sequencing and single strand conformation polymorphism. Twenty-five multi-drug resistant isolates exhibited single point mutations (17 isolates at Ser315Thr plus Arg463Leu, 1 at Thr308Pro plus Arg463Leu, 7 at either Ser315Thr or Arg463Leu) while the other 4 isoniazid-resistant isolates had single point mutation only at Arg463Leu. Seven of 25 multi-drug-resistant isolates [4 at C(-15)T, 1 at T(-8)C; 1 at C(-15)T plus Ser94Ala and 1 at Ile21Val] and 2 of 4 isoniazid-resistant isolates [1 at C(-15)T, 1 at C (-15)T plus Ile21Thr] had mutations in inhA promoter and open reading frame, while the other 20 isolates had no mutation at any position. No frame shift mutation was observed in any tested isolates. This is the first report of two mutations, Trp308Pro of katG and T (-8)C of inhA in Mycobacterium tuberculosis isolates.

Declining prevalence of drug-resistant tuberculosis among HIV/tuberculosis co-infected patients receiving antiretroviral therapy.

BACKGROUND: Drug-resistant tuberculosis (DR-TB) is a serious threat in developing countries where the prevalence of both HIV and TB are high. Antiretroviral therapy (ART) has been more accessible in these countries. The present study aimed to determine the impact of ART on the prevalence of DR-TB among HIV/TB co-infected patients. MATERIAL AND METHOD: A retrospective cohort study was conducted among HIV-infected patients with culture-proved TB from 1999 to 2004. Susceptibilities of Mycobacterium tuberculosis to antituberculous drugs and rate ofART use were studied. RESULTS: There were 225 patients, mean age 35.8 years, 72.4% male and median CD, 44 cells/mm(3). Patients who had received ART increased from 18.5% in 1999 to 92.1% in 2004 (p

Antifungal susceptibilities of Cryptococcus neoformans cerebrospinal fluid isolates and clinical outcomes of cryptococcal meningitis in HIV-infected patients with/without fluconazole prophylaxis.

OBJECTIVES: To compare the MICs of FLUconazole (FLU) and amphotericin B against isolates of Cryptococcus neoformans (C. neoformans) obtained from the CerebroSpinal Fluid (CSF); and clinical outcomes of HIV-infected patients diagnosed with cryptococcal meningitis. MATERIAL AND METHOD: There were two groups including those who did not receive FLU (group A) and those who did receive either FLU 400 mg/week for primary prophylaxis cryptococosis or 200 mg/day for secondary prophylaxis cryptococosis (group B). CSF isolates of C. neoformans from group A and group B between January 2003 and October 2004 were retrospectively studied. The MICs were determined by using the standard NCCLS broth microdilution methods (M27-A). The MICs of FLU and amphotericin B, and clinical outcomes after 10 weeks of cryptococcal meningitis treatment were determined. RESULTS: There were 98 isolates; 80 in group A and 18 in group B. The patients in group B had a higher proportion of previous opportunistic infections (p = 0.008). The other baseline characteristics between the two groups were not different. The median (range) MIC of FLU was 8.0 (0.5-32) microg/ml in group A, and 6.0 (0.5-32) microg/ml in group B (p = 0.926). The median (range) MIC of amphotericin B was 0.25 (0.03-1.0) microg/ml in group A, and 0.25 (0.12-1.0) microg/ml in group B (p = 0.384). Sixty patients from group A and 14 from group B received standard treatment and continued to follow-up. After the 10-week treatment, 39/60 (65%) patients in group A and 7/14 (50%) in group B had complete recovery (p = 0.364; RR = 0.538, 95%CI = 0.166-1.742). The overall mortality rate was 14/60 (23.3%) in group A and 7/14 (50.0%) in group B (p = 0.096; RR = 3.286, 95%CI = 0.983-10.979). CONCLUSION: The MICs of FLU and amphotericin B against CSF isolates of C. neoformans and clinical outcomes between HIV-infected patients who receive or did not receive FLU prophylaxis are not different.

Antifungal susceptibilities of Cryptococcus neoformans.

Susceptibility profiles of medically important fungi in less-developed countries remain uncharacterized. We measured the MICs of amphotericin B, 5-flucytosine, fluconazole, itraconazole, and ketoconazole for Cryptococcus neoformans clinical isolates from Thailand, Malawi, and the United States and found no evidence of resistance or MIC profile differences among the countries.

Comparison of Cryptosporidium parvum development in various cell lines for screening in vitro drug testing.

This study describes the development of Cryptosporidium parvum in MDCK, MA-104, Hep-2 and Vero cell lines. Differences in susceptibility, infectivity, and the methodology of excystation were determined. Various solutions were considered to determine the factors which enhanced the excystation (eg with and without sodium hypochlorite, trypsin or sodium taurocholate). It was shown that the sporozoites could be excysted in media either with or without trypsin and sodium taurocholate, but the number of sporozoites in the latter solution was less than the former one. Only oocysts digested by sodium hypochlorite and trypsin can enter the culture cells. Numerous meronts and oocysts were demonstrated and persisted for 9 days. Asexual stages were not observed in MA-104. Only few oocysts could be detected 1-3 days post-inoculation. There was a significant difference between the number of oocysts, which invaded MDCK, MA-104, and Hep-2 cells. MDCK gave the highest susceptibility to oocyst invasion among the three cell lines and asexual stages were also found. Among the 25 isolates, which had been cultivated, 23 isolates could infect MDCK and Hep-2. Only 2 isolates could not infect the MDCK cell. These 2 isolates could infect the Vero cell and yielded high numbers of trophozoites. Praziquantel (PZQ), doxycycline, and paromomycin (PRM) were tested on the infecting parasites. The drugs were added either with the inoculum or 24 hours after inoculation. None of them was effective, including PRM, which had been previously reported as effective.

PCR detection and prevalence of enterotoxin (cpe) gene in Clostridium perfringens isolated from diarrhea patients.

UNLABELLED: Clostridium perfringens isolated from patients with diarrhea (n=233) were analysed by a duplex PCR assay, in order to determine the prevalence of enterotoxin (cpe) gene and various factors involved in patients with cpe-positive isolates. This duplex PCR uses two sets of primers which amplify in the same reaction two different gene fragments: the phospholipase C (plc, alpha-toxin) and the enterotoxin (cpe) genes in C. perfringens. PCR analysis of 477 colonies of fecal spore isolates, from 159 patients who had a spore count > or = 10(3) cfu/g, gave positive plc gene detection in 436 colonies. The results were consistent with those obtained by using the standard method of C. perfringens species identification. 21 of 436 colonies gave positive results for both plc and cpe genes, indicating a prevalence of 4.8 per cent of C. perfringens that carried the cpe gene in cases of diarrhea. The majority of cases with cpe-positive isolates were women over 50 years of age (71.4%). These patients had diarrhea more than 6 times per day (71.4%) with a duration of 1-3 days (100%). Furthermore, 85.7 per cent of cases developed diarrhea after food consumption, 28.6 per cent had high spore counts of more than 106/g in their feces, and 71.4 per cent were co-infected with other enteric pathogens. The spore count should be interpreted with caution because not all isolates of C. perfringens from diarrhea patients with high fecal spore count carried the cpe gene, which encodes a sporulation-associated enterotoxin. CONCLUSION: The duplex PCR assay can thus become a tool for C. perfringens species identification together with the detection of enterotoxin gene. This PCR assay is faster, less expensive and more suitable for large-scale use in epidemiological studies than conventional procedures. The authors recommend this assay to screen for enterotoxigenic C. perfringens isolates from primary fecal spore isolation cultures, particularly in elderly patients with food-borne diarrhea and non-food related diarrhea.

A prevalence of Cryptosporidium infections among Thai HIV-infected patients.

The prevalence of Cryptosporidium in 156 HIV-infected Thai patients who had acute diarrheal illness at Bamrasnaradura Infectious Diseases Hospital, was studied. This cross-sectional study was performed from March to August in year 2001. The patients ranged in age from 1 month-65 years old. A stool sample from each subject was stained to find the oocysts by modified Ziehl Nelson carbolfuchsin staining. According to the present study, a diagnosis of Cryptosporidium parvum infection was found in 20 patients (11 males and 9 females). The prevalence of cryptosporidiosis in the present series was 12.8 per cent (10.0% in males and 19.1% in females). This infection rate between males and females was not significantly different. Comparing this prevalence to a report in the previous 5 years in the same hospital, the same high rate can be seen.

Distribution of Aeromonas hydrophila serogroups in different clinical samples and the development of polyclonal antibodies for rapid identification of the genus Aeromonas by direct agglutination.

We characterized a collection of 256 Aeromonas hydrophila strains isolated from blood, discharge and stool for their serogroup designation. Of these, 2.3% were untypable and 15.2% were rough strains. Among the typable strains, about 50% comprised serogroups O:11, O:16, O:18, O:34 and O:83. To develop rapid differentiation of Aeromonas from other oxidase-positive bacteria, antisera against Aeromonas were produced to establish a direct, genus-specific, agglutination test. It was found that among 105 isolates of Aeromonas, 102 showed positive results with the agglutination test. The calculated sensitivity and specificity were 97.1% and 90.7%, respectively.