TRANSMISSION AND RISK FACTORS FOR LATENT TUBERCULOSIS INFECTIONS AMONG INDEX CASE-MATCHED HOUSEHOLD CONTACTS.

An understanding of the risk factors associated with acquiring and transmitting Mycobacterium tuberculosis (MTB) is required for controlling tuberculosis (TB). We aimed to determine the risk factors and transmission factors for latent tuberculosis infection (LTBI) in northeastern Thailand. Household contact persons (n = 70) and matched index patients with pulmonary TB (n = 42) who presented to Srinagarind Hospital, Khon Kaen, Thailand were interviewed from September 1, 2012 to March 31, 2014. LTBI was determined by positive results on both a tuberculin skin test and the QuantiFERON-TB Gold In-Tube test. Multivariate analysis of host and environmental risk factors was performed. Among contact persons, being aged 20 years (adjusted OR=14.0; 95% CI: 1.2-159.5), having a family relationship with a TB subject such as being a spouse or parent (adjusted OR=24.9; 95% CI: 2.4-263.9) and exposure to a TB subject for 5 hours/day (adjusted OR=9.2; 95% CI: 1.4-58.1) were risk factors for LTBI. Having a high bacillary load (adjusted OR=2; 95% CI: 1.26-3.17) or a moderate bacillary load (adjusted OR=1.39; 95% CI: 1.04-1.84) among TB subjects correlated with increased transmissibility compared to having a low bacillary load. The type of dwelling and density of household members were not found to be risk factors for LTBI in our study. We conclude being aged 20 years and having a relationship with a TB patient as a spouse or parent were risk factors for acquiring LTBI, and having a higher bacillary load was a risk factor for transmitting TB. Keywords: latent tuberculosis infection, transmission factor, risk factor, Mycobacterium tuberculosis, interferon-gamma release assay, Thailand

Evaluation of the QuantiFERON?-TB Gold In-Tube assay and tuberculin skin test for the diagnosis of Mycobacterium tuberculosis infection in northeastern Thailand.

BACKGROUND: The diagnosis of latent Mycobacterium tuberculosis infection (LTBI) is currently based on the immunological response of T-cells to M. tuberculosis (MTB) antigens. However, the QuantiFERON®-TB Gold In-Tube assay (QFT) has not yet been evaluated in the Thai adult population. OBJECTIVE: To evaluate the diagnostic performance and determine predictors of discordant results between the QFT and tuberculin skin test (TST). METHODS: Active tuberculosis (ATB) patients (n=54), close contacts (CCs) living in the same household as a TB patient (n=100) and healthy controls (HCs) (n=60) were interviewed and underwent the QFT and TST at Srinagarind Hospital in Thailand. Various cut-off values for the QFT (0.25-0.35 IU/mL) and TST (5-15 mm) were applied. RESULTS: The maximum agreement rate between the tests was 71.5% (κ=0.41) with cut-offs of 0.35 IU/mL and 10 mm or 0.25 IU/mL and 10 mm. Based on standard cut-off values (0.35 IU/mL and 10 mm) and using ATB patients and HCs as positive and negative controls, the TST was more sensitive than the QFT (87.0% vs. 66.7%, respectively), whereas the QFT was more specific than the TST (83.3% vs. 70.0%, respectively). Being underweight (OR 3.86, 95%CI 1.3-11.48) or overweight (OR 5.9, 95%CI 1.24-28.16) was significantly associated with TST+/QFT- results. Diabetes (OR 32.56, 95%CI 1.73-613.49) and poor or fair nutrition (OR 7.4, 95%CI 1.23-44.57) were significantly associated with TST-/QFT+ results. CONCLUSION: The TST should be used as a screening test based on its higher sensitivity, whereas the QFT should be used as a confirmatory test because of its higher specificity.

T-CELL RESPONSES ASSESSED USING IGRA AND TST ARE NOT CORRELATED WITH AFB GRADE AND CHEST RADIOGRAPH IN PULMONARY TUBERCULOSIS PATIENTS.

A definitive marker determining the bacillary load of Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), and hence disease severity, is required for patient monitoring and management. In this study, the association among T-cell responses based on the interferon-gamma release assay (IGRA) and the tuberculin skin test (TST), the sputum acid-fast bacilli (AFB) grade and types of radiological lesions were analyzed in new cases of pulmonary TB patients (n = 54) at Srinagarind Hospital, Khon Kaen, Thailand between September 1, 2012 and March 31, 2014. It was found that infiltrative and cavitary lesions from chest radiographs were associated with high sputum AFB grade (p = 0.048). T-cell responses from both IGRA and TST were not correlated with sputum AFB grade. Neither IGRA nor TST was correlated with the bacillary load as defined by AFB grade and chest radiographs. Patients with cavitary lesions on chest radiographs tended to have high IFN-γ concentrations and large TST indurations. In addition, TB patients with previous BCG vaccination showed significantly higher IFN-γ induction compared to the non-vaccinated group (p = 0.001). This study showed T-cell responses based on both IGRA and TST were not correlated with AFB grade and chest radiograph. In areas of high rates of BCG vaccination, as in Thailand, the BCG may affect IGRA and TST interpretations.

Causative agents and resistance among hospital-acquired and ventilator-associated pneumonia patients at Srinagarind Hospital, northeastern Thailand.

Abstract. Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) have an impact on health care costs and mortality. The aim of this study was to identify the causative agents, antibiotics prescribed, cost of treatment and drug resistance trends among HAP and VAP patients at a tertiary-care hospital in northeastern Thailand during 2008 and 2009. The incidences of HAP in 2008 and 2009 were 0.7/1,000 and 0.55/1,000 hospital days, respectively. The incidences of VAP in 2008 and 2009 were 13.6/1,000 and 12.6/1,000 ventilator days, respectively. About 70% of HAP were caused by Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae; and 70% of VAP were caused by A. baumannii, P. aeruginosa, and K. pneumoniae. The ranking in the causative agents of HAP and VAP was not different, but more antimicrobial resistant organisms were seen in 2009. More than half of the costs of nosocomial infection treatment in 2008 and 2009 were the costs for HAP and VAP, 16.8 and 17.5 million Baht, respectively. Fewer A. baumannii and P. aeruginosa isolates were sensitive to carbapenems. Only one-fifth of A. baumannii isolates were sensitive to cefoperazone/sulbactam. The only two antimicrobial agents with consistently good activity against A. baumannii were tigecycline (approximately 85%) and colistin (approximately 99%). Fifty-seven point six percent of P. aeruginosa isolates were sensitive to ceftazidime, 72.4% were sensitive to piperacillin/tazobactam, 95.9% were sensitive to netilmycin and 99.2% were sensitive to colistin. Forty-seven percent of K. pneumoniae isolates were extended spectrum beta-lactamase and sensitive to carbapenems. Methicillin-resistant S. aureus was the cause of 6-7% of HAP/VAP cases in our study.

Clinical factors predictive of PCR positive in pandemic H1N1 2009 influenza virus infection.

OBJECTIVE: Pandemic H1N1 2009 influenza virus (H1N1) has been spreading globally. Clinical features might be predictive and may be different among countries. Even though the PCR test is a confirmatory test for this viral infection, it is expensive and limited in most Thai health care facilities. We studied predictive factors of PCR positive in H1N1 suspected patients. METHODS: Consecutive patients who had influenza-like illness less than seven days and had been tested for H1N1 by the real-time PCR method between May and July 2009 were enrolled. Clinical data was collected and compared between those who had positive and negative PCR tests. RESULTS: There were 6494 patients had flu-like symptoms. Of those, 166 patients were done PCR test and 75 patients (45·18%) had positive PCR test. There were four predictors for positive PCR test including history of contact with confirmed H1N1 patients, headache, body temperature, and coryza with the adjusted odds ratio (95% confidence interval) of 2·84 (1·09-7·40), 6·25 (1·42-27·49), 1·69 (1·08-2·66), and 0·31 (0·12-0·79), respectively. CONCLUSIONS: Clinical factors can be both suggestive and protective factors for H1N1 infection. These factors may be helpful in clinical practice to assess the possibility of the H1N1 infection in people who are at risk; particularly in resource-limited health care facilities.

Can workplaces be predictors for recent onset latent tuberculosis in health care workers?

OBJECTIVE: To study the association of workplaces and recent onset latent tuberculosis (LTB) in health care workers (HCW). METHODS: A case-control study was conducted at Srinagarind Hospital, Khon Kaen University, Thailand. We recruited HCW who had results of tuberculin test within 2 consecutive years from 2001-2008 and also had fixed workplaces (working hours more than 40 hours/week). Cases were subjects with tuberculin conversion, while controls were subjects with negative results of tuberculin test in two consecutive years. Tuberculin conversion was defined if a subject had a negative baseline tuberculin test and a positive tuberculin test in the next consecutive years. Baseline characteristics, workplaces (office, in-patient unit, out-patient unit, intensive care, operating room, and laboratory unit), tuberculosis related variables, and prevention strategies were studied. Multiple logistic regression analysis was used to identify predictors for tuberculin conversion. RESULTS: There were 624 subjects who met the criteria and 163 subjects had tuberculin conversion (26.1%; case group). The median age and male/female ratio of both groups were 39 years old and about 1:4. The cases group had higher percentage of subjects who worked at in- and out-patient department (30.7 vs 20.2 and 17.2 vs 12.2, respectively), had history of tuberculosis exposure in the past year (32.1 vs 16.1), and had history of prevention by any method and by surgical mask (49.4 vs 37.0 and 54.3 vs 38.3, respectively). Workings at in- and out-patient unit and history of tuberculosis exposure in the past year were significant predictors for tuberculin conversion (adjusted odds ratio and [95% confidence interval] of 1.99 [1.25-3.17], 1.91 [1.10-3.17], and 2.26 [1.47-4.96], respectively). SUMMARY: Workplaces in health care facilities do increase risks of LTB in HCW, particularly in in- and out-patient unit. Policy development regarding tuberculosis infection control programs focused on workplace prevention in health care facilities in Thailand is needed.