Diagnostic performance of whole-genome sequencing for identifying drug-resistant TB in Thailand

BACKGROUND: Whole-genome sequencing (WGS) is a promising tool for the detection of drug-resistant TB (DR-TB). To date, there have been few comparisons of diagnostic performance of WGS and phenotypic drug susceptibility testing (DST) in DR-TB.METHODS: We compared drug resistance-conferring mutations identified by WGS analysis using TB-Profiler and Mykrobe with phenotypic DST profiles based on the Löwenstein-Jensen proportion method using drug-resistant Mycobacterium tuberculosis (n = 537) isolates from across Thailand. Based on available phenotypic DST results, diagnostic performance was analysed for resistance against isoniazid, rifampicin, ethambutol (EMB), streptomycin, ethionamide (ETH), kanamycin, capreomycin (CPM), para-aminosalicylic acid, ofloxacin and levofloxacin.RESULTS: High agreement between the two methods was observed for most drugs (>91%), except EMB (57%, 95% CI 53-61) and ETH (70%, 95% CI 66-74). Also, low specificity was observed for EMB (49%, 95% CI 44-54) and ETH (66%, 95% CI 61-71). Sensitivity was high for most drugs (range 83-98%), except CPM (77%, 95% CI 59-88).CONCLUSION: Low agreement between WGS and phenotypic tests for drug resistance was found for EMB and ETH. The current genomic database is insufficient for the identification of CPM resistance. Challenges remain for routine usage of WGS-based DST, especially for second-line anti-TB drugs.

Prevalence and associated risk factors of drug-resistant tuberculosis in Thailand: results from the fifth national anti-tuberculosis drug resistance survey

OBJECTIVE

To assess the prevalence and risk factors of drug-resistant tuberculosis (TB), the fifth national anti-TB drug resistance survey was conducted in Thailand.

METHODS

A cross-sectional study was conducted by stratified cluster sampling with probability proportional to size of TB cases from public health facilities in 100 clusters throughout Thailand from August 2017 to August 2018. Susceptibility testing of TB isolates to first- and second-line anti-TB drugs was performed on Löwenstein-Jensen medium using the indirect proportion method. Multiple imputation was done for handling missing data using Stata 16. The proportion of TB cases with drug resistance was determined. The odds ratio was used to evaluate risk factors associated with drug-resistant TB.

RESULTS

Among 1501 new TB and 69 previously treated TB cases, 14.0% [95% confidence interval (CI): 12.1-16.1] and 33.4% (95% CI: 23.6-44.8), respectively, had resistance to any anti-TB drug. Multidrug-resistant TB accounted for 0.8% (95% CI: 0.5-1.4) of new TB cases and 13.0% (95% CI: 6.5-24.4) of previously treated TB cases. Drug-resistant TB was associated with prior TB treatment [odds ratio (OR), 2.9; 95% CI: 1.6-5.0], age at 45-54 years (OR, 1.6; 95% CI: 1.0-2.4), male (OR, 1.5; 95% CI: 1.0-2.1) and human immunodeficiency virus (HIV) infection (OR, 1.6; 95% CI: 1.0-2.4).

CONCLUSIONS

The burden of drug-resistant TB remains high in Thailand. Intensified prevention and control measures should be implemented to reduce the risks of drug-resistant TB in high-risk groups previously treated, especially individuals of late middle age, males and those with coinfection of TB and HIV.

Indo-Oceanic Mycobacterium tuberculosis strains from Thailand associated with higher mortality

SETTING: This study was conducted among tuberculosis (TB) patients in a highly endemic Thai province.OBJECTIVE: To evaluate the association between different Mycobacterium tuberculosis lineages and clinical characteristics, especially mortality.DESIGN: We enrolled 1,304 TB patients registered from 2002-2011 with culture isolates whose lineages were identified by specific regions of deletion. Data on mortality within 1 year of follow-up were extracted from the registration system and hospital records. Mortality-associated risk factors, including bacterial lineages, as independent variables were analysed using Cox regression models.RESULTS: Of 1,304 isolates, 521 (40.0%) and 582 (44.6%) belonged to Indo-Oceanic and East-Asian lineages, respectively. Indo-Oceanic strains significantly increased the mortality risk compared with East-Asian strains (adjusted hazard ratio [aHR] 1.42, 95%CI 1.02-1.99) or modern lineages (aHR 1.49, 95%CI 1.08-2.06) in the 172 patients who died within 1 year after TB diagnosis. The former also caused significantly higher mortality than modern lineages among patients who died within 6 months after TB diagnosis (aHR 1.62, 95%CI 1.12-2.35). No significant association was found between drug resistance and death.CONCLUSION: In Thailand, the Indo-Oceanic lineage of M. tuberculosis increased mortality risk compared with modern lineages or the East-Asian lineage, the latter being considered highly virulent in previous studies.

Second-line drug susceptibilities of multidrug-resistant tuberculosis strains isolated in Thailand: an update

The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) and the emergence of extensively drug-resistant tuberculosis (XDR-TB) globally hamper the successful treatment and effective control of TB. Information on second-line drug susceptibility, which is of utmost importance for patient care, is still limited. This study demonstrates the susceptibilities of 1447 strains of MDR-TB, including 58 XDR-TB strains, isolated from Siriraj Hospital, Bangkok, Thailand, to aminoglycosides, fluoroquinolones, ethionamide (ETH), para-aminosalicylic acid (PAS) and linezolid. Results revealed that 93-94% of the MDR-TB strains were susceptible to aminoglycosides, 85-98% to fluoroquinolones, 78% to ETH, 85% to PAS and 99% to linezolid.

Genotypic analysis of genes associated with isoniazid and ethionamide resistance in MDR-TB isolates from Thailand

Nucleotide sequences of genes conferring isoniazid resistance (katG, inhA, oxyR-ahpC and ndh) and ethionamide resistance (ethA) in 160 drug-resistant Mycobacterium tuberculosis clinical isolates from Thailand were analysed. Mutations in the katG gene were found in 129 isolates, predominantly at codon 315, which was mutated in 127 isolates. Twenty-two isolates had mutations in the inhA promoter and coding region. Mutations in the oxyR-ahpC intergenic region and in ndh were detected in four and one isolate(s), respectively. Of 24 ethionamide-resistant isolates, 13 had mutations in the ethA gene. However, these mutations were dispersed along the entire gene, with no codon predominating significantly.

Genome-wide SNP-based linkage analysis of tuberculosis in Thais

Tuberculosis, a potentially fatal infectious disease, affects millions of individuals annually worldwide. Human protective immunity that contains tuberculosis after infection has not been clearly defined. To gain insight into host genetic factors, nonparametric linkage analysis was performed using high-throughput microarray-based single nucleotide polymorphism (SNP) genotyping platform, a GeneChip array comprised 59 860 bi-allelic markers, in 93 Thai families with multiple siblings, 195 individuals affected with tuberculosis. Genotyping revealed a region on chromosome 5q showing suggestive evidence of linkage with tuberculosis (Z(lr) statistics=3.01, logarithm of odds (LOD) score=2.29, empirical P-value=0.0005), and two candidate regions on chromosomes 17p and 20p by an ordered subset analysis using minimum age at onset of tuberculosis as the covariate (maximum LOD score=2.57 and 3.33, permutation P-value=0.0187 and 0.0183, respectively). These results imply a new evidence of genetic risk factors for tuberculosis in the Asian population. The significance of these ordered subset results supports a clinicopathological concept that immunological impairment in the disease differs between young and old tuberculosis patients. The linkage information from a specific ethnicity may provide unique candidate regions for the identification of the susceptibility genes and further help elucidate the immunopathogenesis of tuberculosis.

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.

Restriction fragment length polymorphism study of nationwide samples of Mycobacterium tuberculosis in Thailand, 1997-1998

SETTING

During 1997-1998, a national anti-tuberculosis drug resistance survey was conducted in Thailand as a part of a global project.

OBJECTIVE

To evaluate the IS6110 hybridisation patterns and the level of clustering, which was expected to be low due to the short duration of the sample collection.

DESIGN

Eight hundred and twenty-eight bacterial isolates were available for fingerprinting by standard IS6110 hybridisation.

RESULTS

The restriction fragment length polymorphism patterns varied with geographic locations, ages of the patients, and resistance to rifampicin and streptomycin. The Beijing strain was more common among younger patients, and their prevalence appeared to decrease with the distance from Bangkok, while the opposite was true for the single-banded isolates. Excluding isolates containing five or less copies of IS6110, 26.4% were clustered. Clustering was more common among females. The clustered isolates were sometimes from different provinces and, if resistant to drugs, usually possessed different resistance profiles.

CONCLUSIONS

The results question the validity of inferring recent transmission from the clustering of IS6110 hybridisation patterns in some settings in Thailand. The level of recent transmission in a nationwide study in a country with a high incidence of tuberculosis should be evaluated with caution.

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.

Development and evaluation of a one-tube seminested PCR assay for the detection and identification of Penicillium marneffei

A one-tube seminested polymerase chain reaction (PCR) assay was developed to detect and identify Penicillium marneffei DNA coding for 18S rRNA both from purified DNA and from clinical samples. DNA from 120 strains of organisms and 19 blood samples from AIDS patients was amplified with F3, CPL1 and PM primers. Under optimized conditions, these primers detected 100% specifically amplified products of 251 and 331 bp from all P. marneffei DNA preparations (47 strains) and from two blood samples of AIDS patients suspected to suffer from penicilliosis marneffei. The assay was sensitive to detect as little as 10 pg purified DNA, which is equivalent to 250 cells. This PCR assay might be useful as an alternative test, if a rapid diagnosis of penicilliosis marneffei is needed.

Rapid and simple MTT method for rifampicin and isoniazid susceptibility testing of Mycobacterium tuberculosis

The MTT method for rifampicin and isoniazid susceptibility testing of Mycobacterium tuberculosis was developed by using bacterial suspension prepared from colonies on solid media. The MTT tube assay in 1 ml Middlebrook 7H9 broth was completed within 4 days for rifampicin (RMP) and within 7 days for isoniazid (INH). When MTT assay results with 279 M. tuberculosis clinical isolates were compared with those of the conventional proportion method on Löwenstein-Jensen medium, high specificity and sensitivity values of 100% and 94.1%, respectively, for RMP susceptibility testing, and 99.5% and 89.2%, respectively, for INH susceptibility testing were obtained. The accuracy of the MTT method for RMP and INH was > 0.97 concordance with the proportion method. The MTT method is simple, inexpensive and rapid. The high level of agreement with the conventional proportion method suggests a potential to rapidly detect drug-resistant M. tuberculosis in developing countries, as only basic microbiological equipment is need.

Protozoan enteric infection in AIDS related diarrhea in Thailand

The aim of this study was to determine the prevalence of enteric protozoa and other pathogens in AIDS patients with diarrhea in Bangkok, Thailand. Of 288 consecutive patients screened in the 10 month period between November 1999-August 2000 inclusive, 55 (19.2%) had Cryptosporidium spp, 13 (4.5%) had Isospora oocyst, 11 (3.8%) had Giardia lamblia, 3 (0.9%) had Entamoeba histolytica, and 1 (0.3%) had Iodamoeba butschlii infection. The prevalence of microsporidia was 11% in this study. Of 251 patients for whom stool culture for bacteria was performed, enteric bacterial pathogens isolated were Campylobacter spp in 18 (7.1%), Salmonella spp in 11 (4.3%), and Shigella spp in 1 (0.5%). Other pathogens found in these patients were Clostridium difficile in 16/102 (15.6%). Mycobacterium spp in 18/287 (6.2%), and Strongyloides stercoralis in 23/288 (8.0%). Overall, parasitic and bacterial pathogens were identified in 140 (48.6%) patients. These pathogens were identified by the routine simple wet smear technique in 32, formalin-ether concentration method in 46, culture for S. stercoralis in 5, and culture for bacteria in 30. Additional test, using modified Ziehl-Neelsen staining, identified cryptosporidial oocyst, isospora oocyst, and Mycobacterium spp in 72. The microsporidia, initially identified by modified trichrome blue staining, all were then determined to be Enterocytozoon bieneusi by thin sectioning electron microscopy. Protozoan and bacterial pathogens were confirmed to be important etiologic agents in diarrhea in AIDS in Thailand. They were all associated with increased mortality. Routine stool examination by simple wet smear detected only one-fourth of these pathogens. Therefore all diagnostic techniques for these organisms should be made more widely available in Thailand.

Comparative evaluation of Candi Select test and conventional methods for identification of Candida albicans in routine clinical isolates

The Candi Select test (Sanofi Diagnostics, Pasteur, Marnes-La-Coquette, France) is a new yeast-selective medium for the identification of Candida albicans in the clinical laboratory. The performance of this test was compared with the conventional methods of chlamydospore formation, germ tube formation and carbohydrate fermentation. Four hundred and twenty clinical yeast isolates from 412 fresh clinical specimens, including 283 C. albicans, 59 C. tropicalis, 39 Trichosporon spp., 19 C. glabrata, 11 Cryptococcus neoformans and 9 other yeasts, were evaluated. Colonies of C. albicans produced a blue-green colour on the Candi Select media which could be distinguished from the other yeasts with the naked eye within 24-48 h. The sensitivity and specificity of the Candi Select test for the identification of C. albicans were 99.65% and 97.08%, respectively. The blue-green colonies of C. albicans were easy to identify and recognize in mixed cultures and did not need detailed microscopic examination.

Can serial qualitative polymerase chain reaction monitoring predict outcome of pulmonary tuberculosis treatment?

BACKGROUND

The aim of this study was to assess the use of qualitative one-tube nested polymerase chain reaction (PCR) for monitoring the treatment response in smear-positive pulmonary tuberculosis, and the factors determining the negative conversion of sputum smear, culture, and PCR during treatment.

METHODOLOGY

A total of 53 patients receiving a standard short course of chemotherapy with 24 months follow-up period after treatment cessation were included in the study. Sputum specimens were collected serially for smear, culture, and PCR until the treatment was complete.

RESULTS

The conversion rate for sputum culture, smear, and PCR at 8 weeks after treatment were 84.9, 58.5, and 47.1%, and at 16 weeks of treatment were 100, 88.7, and 79.2%, respectively. At the end of the treatment period, there were four PCR persisters, one of whom had disease relapse. Only cavitary disease had an influence over the negative conversion of the smear and PCR at 8 weeks (RR 3.5, 95% CI 1.04-11.95, P=0.04 for smear; RR 5.06, 95% CI 1.196-21.42, P=0.03 for PCR).

CONCLUSION

Qualitative PCR was not useful for monitoring therapy in smear-positive pulmonary tuberculosis. Mycobacterium DNA was cleared slowly in cavitary disease. The PCR may be performed at the time of treatment cessation to identify those with potential for disease relapse.

Antibody detection for the diagnosis of tuberculous pleuritis

SETTING

University Hospital, Bangkok, Thailand.

OBJECTIVE

To evaluate the diagnostic value of antibody detection in serum and in pleural effusion as a marker of tuberculous pleuritis (TBP).

DESIGN

Cross-sectional study.

MATERIALS AND METHODS

One hundred and fifty-five patients with pleural effusion who underwent diagnostic evaluation at Siriraj Hospital between March 1999 and May 2000 were recruited. Samples of pleural fluid were examined biochemically, cytologically and microbiologically. Pathological examination of pleural tissue was also performed. The diagnosis of TBP or other diagnosis was made by either pathological finding or culture result. Immunochromatographic tuberculosis (ICT-TB) tests for antibody detection were then performed using the stored serum samples and effusions from those patients with a final definite diagnosis. This test detects antibodies to five secreted antigens of Mycobacterium tuberculosis, including the 38 kDa antigen.

RESULTS

We investigated 67 patients with TBP, 44 with malignant pleural effusions, seven with transudates and one with cryptococcal pleuritis. The combined ICT-TB serum and effusion tests were positive in 34/67 TBP and 22/52 non-TBP patients. The sensitivity, specificity, positive predictive value and negative predictive value of the ICT-TB test were 50.7, 57.7, 60.7 and 47.6%, respectively. In 11 TBP patients with human immunodeficiency virus (HIV) co-infection, the sensitivity of the ICT-TB test was 45.6%. There was no correlation between the test positivity and culture result or duration of disease.

CONCLUSIONS

The diagnostic value of antibody detection in TBP is modest in an area with intermediate prevalence of tuberculosis, independently of HIV serological status.

Microbial killing activity of peracetic acid

In vitro killing activity of peracetic acid (Perasafe) at a concentration of 0.26 per cent w/v was tested against Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Salmonella paratyphi A, Acinetobacter baumannii, Sternotrophomonas maltophilia, Enterococcus faecium, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), Bacillus subtilis spore, Mycobacterium tuberculosis and human immuno-deficiency virus type I. Exposure to Peracetic acid (0.26% w/v) for 10 minutes resulted in massive killing of all the aforementioned organisms and spore.

Penicillium marneffei: types and drug susceptibility

The PCR fingerprints of 30 Penicillium marneffei isolates from Chiang Rai in Northern Thailand and Bangkok in central Thailand were studied through use of single-nucleotide primers (GACA)4 and the phage M13 core sequence. Discrimination of fingerprint patterns was based on differences in the number of major bands. The P. marneffei isolates were divided into four types, i.e., A, B, C, and D. Type A was found in two isolates from Chiang Rai (6.7%). Types B and C respectively were found in two (6.7%) and one (3.3%) isolates from Bangkok. The predominate type D (83.3%) was found in isolates obtained from Chiang Rai and Bangkok. The PCR fingerprinting method was found to be useful for the epidemiological study of P. marneffei, a dimorphic opportunistic fungus and an emerging pathogen in the HIV pandemic. In vitro drug susceptibility testing by broth macrodilution to four antifungal agents against the yeast form of P. marneffei was performed. The MIC ranges for amphotericin B, fluconazole, itraconazole, and ketoconazole were 0.125-0.5, 4.0-8.0, < 0.032, and < 0.125 microgram/ml respectively.

Detection of Mycobacterium tuberculosis from sputum specimens using one-tube nested PCR

One-tube nested PCR was developed for diagnosis of pulmonary tuberculosis using sequences based on thel6SrRNA gene. The usage of primers 16SOL, 16SOR, 16SIL and 16SIR with optimized conditions could detect 555 bp DNA band from 21 species, 41 strains of mycobacteria and one isolate of Nocardia asteroides. It also revealed a specific 306 bp DNA band from 59 strains of M. tuberculosis complex. Cross amplification was observed in M. marinum, M. ulcerans and a few isolates of M. fortuitum complex. The developed method could detect as little as 100 fg of M. tuberculosis DNA. The PCR mixtures could be stored at 0 degrees C for 2 months or at -20 degrees C for at least 20 months without decrease in sensitivity. Using one-tube nested PCR for detection of M. tuberculosis compared with acid fast staining and culture results from 153 sputum specimens revealed 88.6% sensitivity and 89.2% specificity in smear positive specimens and 93.2% sensitivity and 85.0% specificity in culture positive specimens.

Penicilliosis-associated hemophagocytic syndrome in a human immunodeficiency virus-infected child: the first case report in children

Infection-associated hemophagocytic syndrome (IAHS) has been found in many systemic infectious conditions with a high mortality rate. Disseminated Penicillium marneffei infection is a common opportunistic condition among HIV-infected patients in many regions in Southeast Asia. We report the first case of IAHS caused by penicilliosis in an HIV-infected child who presented with cytopenias and recovered promptly after antifungal and intravenous immunoglobulin therapy.

Disseminated infection due to rapidly growing mycobacteria in immunocompetent hosts presenting with chronic lymphadenopathy: a previously unrecognized clinical entity

Disseminated infection due to rapidly growing mycobacteria is uncommon and occurs mostly in immunocompromised patients. We report 16 cases of such infection with an unusual presentation seen at Srinagarind Hospital, a university hospital in northeastern Thailand. The clinical features were different from those in previous reports. All of the patients presented with chronic bilateral cervical lymphadenopathy. Twelve had mycobacterial involvement of other organs (sinuses, 6 patients; lungs, 4; liver, 4; spleen, 3; skin, 3; bone and joint, 2; and tonsils, 2). An interesting occurrence in 11 patients was 14 episodes of reactive skin manifestations (Sweet's syndrome, 9; generalized pustulosis and erythema nodosum, 2 each; and pustular psoriasis, 1). No identifiable predisposing factors, including human immunodeficiency disease, were found in these patients. However, 8 patients had 11 episodes of prior infection or coinfection with other opportunistic pathogens (salmonellosis, 4; penicilliosis, 3; pulmonary tuberculosis, 2; and melioidosis and cryptococcosis, 1 each). These findings suggest that cell-mediated immunity is defective in these patients.

Antifungal drug combinations for Cryptococcus neoformans and Prototheca spp

Seventy-one isolates of Cryptococcus neoformans and 5 isolates of Prototheca spp. were tested for in vitro susceptibility against amphotericin B alone and against the combination of amphotericin B with each clinically relevant concentration of flucytosine (5-FC) and rifampin by broth dilution methods. The combinations of amphotericin B and rifampin produced greater effect on reduction of the minimal inhibition concentration (MIC) of amphotericin B than did either drug used individually. Flucytosine combined with amphotericin B produced little or no reduction of the MIC compared with amphotericin B alone.

Deep fungal and higher bacterial skin infections in Thailand: clinical manifestations and treatment regimens

BACKGROUND

Deep fungal and higher bacterial skin infections occur fairly frequently in Thailand.

METHODS

Cases with a provisional diagnosis of deep fungal and higher bacterial infections were prospectively collected from 1994 to 1997 in the Granuloma Clinic, Department of Dermatology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. Demographic data, clinical manifestations, causative organisms, histologic features, treatment, and outcome were investigated.

RESULTS

The total cases in a 4-year period numbered 27. The male to female ratio was approximately 1:1. Mycetoma was most common, followed by chromoblastomycosis. Actinomycetoma was similar in incidence to eumycetoma. The only causative organism that could be identified among the mycetoma cases was Cladosporium carrionii, which caused mycetoma of the buttock of an aplastic anemia patient at the site of bone marrow aspiration. Surgical treatment was recommended for eumycetoma. Chromoblastomycosis was caused by C. carrionii and F. compactum and responded well with itraconazole orally. Mycotic abscesses were found in four cases, basidiobolomycosis in two cases, and cutaneous nocardiosis in one case. Cotrimoxazole was recommended in the treatment of actinomycetoma, cutaneous nocardiosis, and basidiobolomycosis.

CONCLUSIONS

Localized, chronic, slow, progressive, and usually asymptomatic were the main cutaneous manifestations of deep fungal and higher bacterial skin infections. A skin biopsy for histologic study and culture identification should be performed in every suspected case. The causative organisms were found in the histologic sections of every case, but only about one-third were found by culture.

Prolonged fever due to Mycobacterium avium complex (MAC) disease in advanced HIV infection: a public health concern

From March 1997 to June 1998, infectious etiologies of prolonged fever was prospectively investigated in 104 advanced human immunodeficiency virus (HIV) infected patients admitted to Siriraj Hospital. The etiology could be identified in 91 cases (87.5%). Of these, blood cultures from 68 patients yielded mycobacteria and fungi. Mycobacterium avium complex was the most common blood isolate in 24 per cent of the patients; followed by Mycobacterium tuberculosis in 20.2 per cent, Cryptococcus neoformans in 5.8 per cent, Penicillium marneffei in 5.8 per cent. During the course of febrile illness, 79 of the 91 patients (86.8%) exhibited focal lesions. Weight loss, elevated serum alkaline phosphatase were often found to be significantly more associated with MAC bacteremia (P < 0.05). Pulmonary involvement significantly correlated more with M. tuberculosis bacteremia than MAC bacteremia (P < 0.05). No cause could be identified in 13 cases. Mycobacterium blood culture alone established the etiologies in 68 cases (65.4%). Of the 25 patients with disseminated MAC (DMAC) infection, nine patients died during hospitalization. Another three cases died within a few months of appropriate anti-MAC chemotherapy. We concluded that the risk of DMAC infection in advanced AIDS patients in Thailand is high when low CD4 lymphocyte count is established. The prolonged fever resulted from DMAC in advanced HIV infection is warrant to be public health concern. Mycobacterium blood culture is a most valuable tool contributing to the diagnosis of infectious agents in this condition. The guidelines of 1997 USPHS/IDSA should be followed to give chemoprophylaxis against DMAC disease in patients with advanced HIV infection and a CD4 count less than 50 cells/mm3.

Human pythiosis

Pythiosis is a cosmopolitan granulomatous disease caused by an aquatic fungus Pythium insidiosum which usually occurs in horses, cattle, dogs, cats or fishes. There have been 28 cases of human pythiosis published in the literature. Twenty three patients have been reported from all over Thailand. Human pythiosis presents in one of three clinical forms: cutaneous or subcutaneous, systemic or vascular and ophthalmic (e.g., corneal ulcer or keratitis). Systemic antibiotics or antimycotics are not effective in the treatment of this infection. A saturated solution of KI gives a beneficial result only in the subcutaneous form. Surgical removal of the source of infection is the method of therapy of vascular and ophthalmic forms.

Assessment of a PCR technique for the detection and identification of Cryptococcus neoformans

The 18S ribosomal RNA gene of Cryptococcus neoformans was amplified by polymerase chain reaction (PCR). The primers CPL1 and CPR4 were tested for their ability to amplify DNA from 30 strains of C. neoformans and 27 specimens of cerebrospinal fluid (CSF) from patients with cryptococcal meningitis. A 343 bp product was obtained and its specificity confirmed by Southern hybridization with an internal sequence (INSR4) probe. The sensitivity was 100 fg by Southern analysis and 1 pg using the PCR. Neither human nor a variety of other fungal and bacterial strains (n = 78) gave an amplified product. This PCR method can detect as few as 5 cells ml-1 of C. neoformans in spiked-CSF following a simple processing procedure. The developed system of PCR was more sensitive than the culture method and revealed a very high specificity. The PCR was easy to perform and needed only 4 h for all processes from receiving the CSF to detection of a specific DNA band after agarose gel electrophoresis. This would provide another rapid laboratory method for the diagnosis of cryptococcal meningitis.

Differentiation of Mycobacterium species by restriction enzyme analysis of amplified 16S-23S ribosomal DNA spacer sequences

SETTING

Mycobacteriology research and service laboratories in Thailand.

OBJECTIVE

To evaluate the possibility of differentiating species of mycobacteria by amplifying 16S-23S ribosomal deoxyribonucleic acid (DNA) spacer and restriction enzyme analysis of the products.

DESIGN

DNA of 113 strains of mycobacteria belonging to 18 species of the genus Mycobacterium were amplified by primers PL1 (5'-GAAGTCGTAACAAGG) and PL2 (5'-CAAGGCATCCACCAT). The amplified products as well as their HaeIII-, MspI- and BstXI-digested products were visualized after agarose gel electrophoresis.

RESULTS

The amplified products of rapid-growing mycobacteria were different from the slow-growing mycobacteria. The restriction profiles of members of M. tuberculosis complex were the same as each other but different from other investigated species. The restriction profiles of some species, such as M. avium, M. intracellulare and M. gordonae, were unique, while those of the other species had more than one pattern. However, the restriction profiles of most investigated species were different from each other.

CONCLUSION

This preliminary study suggested that the method might be useful for species differentiation of some commonly isolated pathogenic mycobacteria.

Outbreak of Tinea capitis caused by Microsporum ferrugineum in Thailand

There was an outbreak of Tinea capitis at the Pak-kred Home for Mentally and Physically Handicapped Babies, Bangkok, Thailand in 1993. One hundred and thirty-eight cases were diagnosed as tinea capitis based on clinical signs and positive laboratory investigations. The results of Wood's light examination, KOH preparation and fungal culture were positive in 89.9, 75.9 and 27.4% respectively. The non-inflammatory form had a higher rate of positive KOH and culture than in the inflammatory form. Microsporum ferrugineum was the major pathogen (66.7%) and most of its infections (80.4%) caused a non-inflammatory type of tinea capitis. Griseofulvin, in a dosage of 10-15 mg/kg/day and selenium sulfide shampoos, yielded an 84.8% cure rate within 14.9 weeks. No recurrence or obvious adverse reactions were observed.

Diagnostic role of fiberoptic bronchoscopy in suspected smear negative pulmonary tuberculosis

Fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy (TBB) was performed in 40 patients suspected to have pulmonary tuberculosis, in whom chest roentgenogram revealed minimal infiltration and sputum smears were negative for acid-fast bacilli. Bronchoscopic procedures provided overall diagnostic yields in 47.5% (19/40) of patients. The diagnostic yield of overall bronchoscopic procedures for tuberculosis in this study was 32.5% (13/40) of patients. It consisted of positive BAL smear in 7.5% (3/40) of patients, positive for mycobacterial culture in 15% (6/40) of patients and TBB revealing granuloma in 17.5% (7/40) of patients. Non-tuberculosis conditions were diagnosed by the bronchoscopic method in six patients (15%). These results suggest that in an area with a high prevalence of tuberculosis, bronchoscopic procedures should be performed in those cases in which other diagnoses such as malignancy must be ruled out. Transbronchial biopsy has a major role for early diagnosis and should be performed in all cases, if possible.

Fatal arteritis due to Pythium insidiosum infection in patients with thalassaemia

Six thalassaemic patients had a distinct clinical syndrome characterized by progressive ischemia of the lower extremities, with ascending arteritis and thrombosis of the main arteries of the lower limbs. With periodic acid Schiff and Gomori's methenamine silver staining a large number of hyphae were revealed in the arterial wall and the outer part of the thrombus. Pythium insidiosum was isolated from 3 patients. The clinical course of the disease was progressive gangrene of the extremities and the patients invariably died when the infectious process reached the bifurcation of the aorta. There is no effective antimicrobial agent for the syndrome and radical amputation was the only method to ensure survival of the patients. P. insidiosum infection should be considered in thalassaemic patients with leg ulcers or arterial occlusion of the lower limbs.

Serum precipitins in pulmonary aspergillosis: preliminary results

Definitive diagnosis of pulmonary aspergillosis is difficult to establish. Thus, confirmative evidence of active fungal aggression is imperative. In this study, an immunodiffusion test was carried out on 36 cases of pulmonary aspergillosis and two groups of subjects comprising 133 patients with non-fungal diseases and 134 healthy volunteers as controls. The test was positive in 92.3% of the patients with mycetoma, in 50% of the patients with allergic bronchopulmonary aspergillosis, and in 25% of the patients with invasive aspergillosis. Results were negative in all subjects in the two control groups. The findings indicate the efficacy of the test under study for supporting the diagnosis of pulmonary aspergillosis.

Subcutaneous mucormycosis caused by Saksenaea vasiformis in a thalassaemic child: first case report in Thailand

A first case of subcutaneous infection caused by Saksenaea vasiformis in an 11-year-old Thai thalassaemic boy was described. The specific diagnosis of infection was attained from microscopic demonstration of the causal agent as well as the isolation of the fungus. The patient was successfully treated by debridement of the lesion and parenteral amphotericin B. The predisposing factors, source of infection and regimen for treatment are discussed.

Induction of zoospore formation in Thai isolates of Pythium insidiosum

Three human isolates of Pythium insidiosum De Cock 1987, the aetiologic agent of pythiosis, were induced for zoosporogenesis. The isolates were grown on Sabouraud glucose agar for 2 days before being inoculated into boiled spikelets of Axonopus compressus (Gramineae) and then into induction medium (IM). Optimum zoospore formation was demonstrated under the light microscope after incubation for 24 h at 37 degrees C in IM.