In people with HIV living in settings where mycobacterial culture is not routinely available to all patients, a third sputum smear adds little to the diagnosis of TB. Broth-based culture of three sputum specimens diagnoses most TB cases, and lymph node aspiration provides the highest incremental yield of any nonpulmonary specimen test for TB.

Diagnostic techniques based on PCR have two major problems: false-positive reactions due to contamination with DNA fragments from previous PCRs (amplicons) and false-negative reactions caused by inhibitors that interfere with the PCR. We have improved our previously reported PCR based on the amplification of a fragment of the Mycobacterium tuberculosis complex-specific insertion element IS6110 with respect to both problems. False-positive reactions caused by amplicon contamination were prevented by the use of uracil-Nglycosylase and dUTP instead of dTTP. We selected a new set of primers outside the region spanned by the formerly used primers to avoid false-positive reactions caused by dTTP-containing amplicons still present in the laboratory. With this new primer set, 16 copies of the IS6110 insertion element, the equivalent of two bacteria, could be amplified 1010 times in 40 cycles, resulting in a mean efficiency of 77% per cycle. To detect the presence of inhibitors of the Taq polymerase, which may cause false-negative reactions, part of each sample was spiked with M. tuberculosis DNA. The DNA purification method using guanidinium thiocyanate and diatoms effectively removed most or all inhibitors of the PCR. However, this was not suitable for blood samples, for which we developed a proteinase K treatment followed by phenol-chloroform extraction. This method permitted detection of 20 M. tuberculosis bacteria per ml of whole blood. Various laboratory procedures were introduced to reduce failure or inhibition of PCR and avoid DNA cross contamination. We have tested 218 different clinical specimens obtained from patients suspected of having tuberculosis. The samples included sputum (n = 145), tissue biopsy samples (n = 25), cerebrospinal fluid (n = 15), blood (n = 14), pleural fluid (n = 9), feces (n = 7), fluid from fistulae (n = 2), and pus from a wound (n = 1). The results obtained by PCR were consistent with those obtained with culture, which is the "gold standard." We demonstrate that PCR is a useful technique for the rapid diagnosis of tuberculosis at various sites.

Although people with HIV frequently have sputum cultures positive for NTM, few meet a strict case definition for NTM disease. Consistent with previous studies, ART was associated with lower odds of having NTM disease. Further studies of NTM in HIV-infected individuals in tuberculosis-endemic countries are needed to develop and validate case definitions.

Bloodstream infections (BSIs) are a major cause of illness in HIV-infected persons. To evaluate prevalence of and risk factors for BSIs in 2,009 HIV-infected outpatients in Cambodia, Thailand, and Vietnam, we performed a single Myco/F Lytic blood culture. Fifty-eight (2.9%) had a clinically significant BSI (i.e., a blood culture positive for an organism known to be a pathogen). Mycobacterium tuberculosis accounted for 31 (54%) of all BSIs, followed by fungi (13 [22%]) and bacteria (9 [16%]). Of patients for whom data were recorded about antiretroviral therapy, 0 of 119 who had received antiretroviral therapy for >14 days had a BSI, compared with 3% of 1,801 patients who had not. In multivariate analysis, factors consistently associated with BSI were fever, low CD4+ T-lymphocyte count, abnormalities on chest radiograph, and signs or symptoms of abdominal illness. For HIV-infected outpatients with these risk factors, clinicians should place their highest priority on diagnosing tuberculosis.

SUMMARY BACKGROUND Delayed diagnosis of tuberculosis (TB) increases mortality. OBJECTIVE To evaluate whether stool culture improves the diagnosis of TB in people living with the human immunodeficiency virus (PLHIV). DESIGN We analysed cross-sectional data of TB diagnosis in PLHIV in Cambodia, Thailand and Viet Nam. Logistic regression was used to assess the association between positive stool culture and TB, and to calculate the incremental yield of stool culture. RESULTS A total of 1693 PLHIV were enrolled with a stool culture result. Of 228 PLHIV with culture-confirmed TB from any site, 101 (44%) had a positive stool culture; of these, 91 (90%) had pulmonary TB (PTB). After adjusting for confounding factors, a positive stool culture was associated with smear-negative (odds ratio [OR] 26, 95% confidence interval [CI] 12–58), moderately smear-positive (OR 60, 95%CI 23–159) and highly smear-positive (OR 179, 95%CI 59–546) PTB compared with no PTB. No statistically significant association existed with extrapulmonary TB compared with no extrapulmonary TB (OR 2, 95%CI 1–5). The incremental yield of one stool culture above two sputum cultures (5%, 95%CI 3–8) was comparable to an additional sputum culture (7%, 95%CI 4–11). CONCLUSION Nearly half of the PLHIV with TB had a positive stool culture that was strongly associated with PTB. Stool cultures may be used to diagnose TB in PLHIV.

Introduction This describes variations in facility peritoneal dialysis (PD) effluent (PDE) culture techniques and local microbiology laboratory practices, competencies, and quality assurance associated with peritonitis, with a specific emphasis on factors associated with culture-negative peritonitis (CNP). Methods Peritonitis data were prospectively collected from 22 Thai PD centers between May 2016 and October 2017 as part of the Peritoneal Dialysis Outcomes and Practice Patterns Study. The first cloudy PD bags from PD participants with suspected peritonitis were sent to local and central laboratories for comparison of pathogen identification. The associations between these characteristics and CNP were evaluated. Results CNP was significantly more frequent in local laboratories (38%) compared with paired PDE samples sent to the central laboratory (12%, P < 0.05). Marked variations were observed in PD center practices, particularly with respect to specimen collection and processing, which often deviated from International Society for Peritoneal Dialysis Guideline recommendations, and laboratory capacities, capabilities, and certification. Lower rates of CNP were associated with PD nurse specimen collection, centrifugation of PDE, immediate transfer of samples to the laboratory, larger hospital size, larger PD unit size, availability of an on-site nephrologist, higher laboratory capacity, and laboratory ability to perform aerobic cultures, undertake standard operating procedures in antimicrobial susceptibilities, and obtain local accreditation. Conclusion There were large variations in PD center and laboratory capacities, capabilities, and practices, which in turn were associated with the likelihood of culturing and correctly identifying organisms responsible for causing PD-associated peritonitis. Deviations in practice from International Society for Peritoneal Dialysis guideline recommendations were associated with higher CNP rates.

Background: The diagnosis of tuberculous lymphadenitis (TBLN) ranges from therapeutic diagnosis to open biopsy with tissue culture. The open biopsies are accepted as the gold standard to diagnose TBLN, but it requires skin incision that leaves unwanted scars. Objective: Test the sensitivity and specificity of fine needle aspiration (FNA) using tissue culture in mycobacteria growth indicator tube (MGIT) and tissue polymerase chain reaction (PCR) for comparison with open biopsy using tissue culture. Subject and methods: Forty patients with clinically suspected cervical tuberculous lymphadenitis were recruited at King Chulalongkorn Memorial Hospital. The patients underwent FNA followed by open biopsies either excisional or incisional. Specimens from FNA were collected for tissue culture in MGIT and for tissue PCR. The specimens from open biopsies were divided into two portions for tissue culture in MGIT (the gold standard) and for hispathology. Results: FNA for tissue culture in MGIT had a moderate sensitivity (65%) but high specificity (83%) (73% positive and 76% negative predictive value). FNA for tissue PCR had a moderate sensitivity (53%) but very high specificity (96%) (90% positive and 73% negative predictive values). Combination of either FNA for tissue culture or FNA tissue PCR revealed an increase in sensitivity and specificity to 83.6% and 80.0%, respectively. However, a combination of both FNA for tissue culture and FNA tissue PCR revealed a decrease in sensitivity (34.5%) but a highly increase in specificity (99.0%). Conclusion: Either the FNA using tissue culture in MGIT or tissue PCR had a moderate sensitivity but high specificity. FNA using tissue culture or FNA tissue PCR may be used as an alternative test for diagnosis TBLN. The techniques may replace the open biopsies because of its effectiveness and low complication rate.

An additional yield of culture from the removed peritoneal dialysis (PD) catheter in diagnosis of pathogen causing refractory peritonitis was assessed in 118 eligible patients from 7 PD centers. Peritoneal dialysis fluid (PDF) culture identified organisms in 86 (72.9%) patients, while the catheter culture identified organisms in 55 (46.6%) patients. PD catheter culture could additionally identify organisms in 19 patients whose PDF culture were negative, increasing the positive culture rate to 89%, in other word 16.1% reducing the culture-negative rate. PD catheter culture provided additional yield, especially in fungal and enterococcal infections.