Aggressive Contact Investigation of In-Hospital Exposure to Active Pulmonary Tuberculosis

Ventilation strategies based on an aerodynamic analysis during a large-scale SARS-CoV-2 outbreak in an acute-care hospital

BACKGROUND

This study aimed to investigate ventilation strategies to prevent nosocomial transmission of coronavirus disease 2019 (COVID-19).

METHODS

We conducted a retrospective epidemiological investigation of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in a teaching hospital (February-March 2021). The largest outbreak ward was studied, and measurements were taken to determine the pressure difference and air change per hour (ACH) of the rooms. Airflow dynamics were assessed using an oil droplet generator, indoor air quality sensor, and particle image velocimetry in the index patient's room, corridor, and opposite rooms, by varying the opening and closing of windows and doors.

RESULTS

During the outbreak, 283 COVID-19 cases were identified. The SARS-CoV-2 spread occurred sequentially from the index room to the nearest room, especially the opposite. The aerodynamic study demonstrated that droplet-like particles in the index room diffused through the corridor and the opposite room through the opening door. The mean ACH of the rooms was 1.44; the air supply volume was 15.9% larger than the exhaust volume, forming a positive pressure. Closing the door prevented diffusion between adjacent rooms facing each other, and natural ventilation reduced the concentration of particles within the ward and minimised their spread to adjacent rooms.

CONCLUSIONS

Spread of droplet-like particles between rooms could be attributed to the pressure difference between the rooms and corridor. To prevent spread of SARS-CoV-2 between rooms, increasing the ACH in the room by maximising ventilation and minimising the positive pressure through supply/exhaust control and closing the room door are essential.

Predictive Factors and Clinical Impacts of Delayed Isolation of Tuberculosis during Hospital Admission

Delayed isolation of tuberculosis (TB) can cause unexpected exposure of healthcare workers (HCWs). This study identified the predictive factors and clinical impact of delayed isolation. We retrospectively reviewed the electronic medical records of index patients and HCWs who underwent contact investigation after TB exposure during hospitalization at the National Medical Center, between January 2018 and July 2021. Among the 25 index patients, 23 (92.0%) were diagnosed with TB based on the molecular assay, and 18 (72.0%) had a negative acid-fast bacilli smear. Sixteen (64.0%) patients were hospitalized via the emergency room, and 18 (72.0%) were admitted to a non-pulmonology/infectious disease department. According to the patterns of delayed isolation, patients were classified into five categories. Among 157 close-contact events in 125 HCWs, 75 (47.8%) occurred in Category A. Twenty-five (20%) HCWs had multiple TB exposures (n = 57 events), of whom 37 (64.9%) belonged to Category A (missed during emergency situations). After contact tracing, latent TB infection was diagnosed in one (1.2%) HCW in Category A, who was exposed during intubation. Delayed isolation and TB exposure mostly occurred during pre-admission in emergency situations. Effective TB screening and infection control are necessary to protect HCWs, especially those who routinely contact new patients in high-risk departments.

Estimating the burden of nosocomial exposure to tuberculosis in South Korea, a nationwide population based cross-sectional study

BACKGROUND/AIMS

The aim of the study was to investigate the current nationwide burden of nosocomial exposure to tuberculosis (TB) using national health insurance claims data.

METHODS

All patients who had claims for drug susceptibility testing for TB from 2012 to 2016, which indicated culture-proven TB, were included. The first day of the infectious period was defined as 3 months before a doctor's suspicion of TB in patients with respiratory symptoms and 1 month before in patients without symptoms. The last day of the infectious period was defined as one day before the prescription of anti-TB medications. Patients hospitalized during infectious periods were investigated and their hospitalization days were calculated. Records of medical procedures which increased the risk of nosocomial transmission by generating aerosols were also investigated.

RESULTS

A total of 7,186 cases with 94,636 person-days of hospitalization with unrecognized active TB were found. Patients above 60 years of age accounted for 63.99% of the total number and 69.70% of the total duration of hospitalization. TB patients in the older age group showed a trend toward higher risks for hospitalization with unrecognized active TB. Patients in their 80s showed the highest risk (12.65%). Bronchoscopy (28.86%), nebulizer therapy (28.48%), and endotracheal intubation (13.02%) were common procedures performed in these patients during hospitalization.

CONCLUSION

The burden of nosocomial exposure to TB in South Korea is still substantial. Hospitalization with unrecognized active TB, especially among the elderly TB patients could be a serious public health issue in South Korea.

The impact of the Xpert MTB/RIF screening among hospitalized patients with pneumonia on timely isolation of patients with pulmonary tuberculosis

In South Korea where the tuberculosis (TB) burden is intermediate, the risk of in-hospital transmission of TB remains high. We conducted a retrospective cohort study of 244 inpatients diagnosed with pulmonary TB (2015–2018) to evaluate the impact of the Xpert MTB/RIF assay (Xpert) screening on timely isolation. TB screening was performed with smear microscopy and a polymerase chain reaction test, and the Xpert was additionally used from November 2016. Among all patients with pulmonary TB, the median time-to-isolation was significantly reduced (22.6 vs. 69.7 h; p < 0.001) and segmented regression analysis adjusting for the time trend showed a reduction in time-to-isolation with the introduction of the Xpert (− 39.3 h; 95% CI − 85.6, 7.0; p = 0.096). Among 213 patients who were timely screened (≤ 72 h after admission), time-to-isolation decreased significantly (− 38.2 h; 95% CI − 70.6, − 5.8; p = 0.021) with the introduction of the Xpert, and its decreasing trend continued. The Xpert provided a shorter turnaround time (4.8 vs. 49.1 h; p < 0.001) and higher sensitivity (76.6% vs. 47.8%; p < 0.001) than smear microscopy. Thus, the Xpert can be a useful screening test for pulmonary TB in real-life hospital settings with an intermediate TB burden.

Delayed Isolation of Active Pulmonary Tuberculosis in Hospitalized Patients: A Pivotal Role of Radiologic Evaluation

OBJECTIVE. The purpose of this study was to determine factors related to delayed isolation of patients hospitalized with active pulmonary tuberculosis (TB). MATERIALS AND METHODS. A total of 130 immunocompetent hospitalized patients with active pulmonary TB who had positive sputum culture results from January 2015 to December 2017 were reviewed. Delayed isolation of pulmonary TB was defined as failure to initiate airborne isolation within the first 3 days of hospitalization. Clinical and microbiologic characteristics of the patients and radiologic features on chest radiography (n = 130) and chest CT (n = 118) were retrospectively reviewed. Findings were compared between patients with early isolation and those with delayed isolation. Univariate and multivariate analyses were performed to determine independent predictors of delayed isolation. RESULTS. Forty-four patients (34%) had delayed isolation after initial hospitalization. On univariate and multivariate analyses, atypical presentation of active pulmonary TB on CT (odds ratio, 7.203; 95% CI, 2.203-23.551; p = 0.001) and concurrent lung parenchymal diseases on CT (odds ratio, 14.605; 95% CI, 3.274-65.155; p < 0.001) were significant predictors of delayed isolation of patients with active pulmonary TB. CONCLUSION. Awareness of the factors related to delayed diagnosis of active pulmonary TB is important to avoid an unexpected in-hospital outbreak of TB and control the disease. Atypical presentation of active pulmonary TB and concurrent lung parenchymal diseases on CT are significant factors related to delayed isolation of hospitalized patients with active pulmonary TB.

Screening and Treatment of Latent Tuberculosis Infection among Healthcare Workers at a Referral Hospital in Korea

Background

Healthcare workers (HCWs) have a high risk of tuberculosis (TB) infection. Since August 2017, Korea has mandated the testing of latent TB infection (LTBI) and recommended treatment from HCWs at medical institutions. However, the acceptance/completion rate and adverse events of LTBI treatment have not been analyzed.

Materials and Methods

From February to August 2017, we conducted a retrospective study at a referral university hospital in Korea, to screen the interferon-gamma release assay (IGRA) tests conducted for all HCWs for detecting and treating LTBI. HCWs diagnosed with LTBI were offered a 9-month isoniazid (9H), 3-month isoniazid/rifampin (3HR), or 4-month rifampin regimen. We investigated the acceptance/completion rate, adverse events, and causes of discontinuation or change in LTBI medication. A major adverse event was one wherein a patient had any adverse event ≥grade 3 causing LTBI treatment interruption.

Results

Of the 1,538 HCWs, 1,379 underwent IGRA testing for LTBI. Among them, 13.6% (187/1,379) tested positive and 73.3% (137/187) received treatment. The overall completion rate was 97.8% (134/137). HCWs were significantly more likely to complete first-line therapy with 3HR than with 9H (91.4% vs. 76.7%, P = 0.02). The most common major adverse event was hepatotoxicity (n = 7), followed by thrombocytopenia (n = 1) and anaphylactic shock (n = 1). Hepatotoxicity and hepatotoxicity (≥ grade 2) were more frequent in 9H than in 3HR (39.5% vs. 17.2%, P = 0.006 and 18.6% vs. 3.7%, P = 0.005, respectively). The median time to hepatotoxicity was 96 days (interquartile range, 20 – 103 days).

Conclusion

Completion of first-line therapy for LTBI is more likely with 3HR than with 9H. This might be related to the development of hepatotoxicity after around 3 months of treatment. Anaphylactic shock and platelet count should be carefully monitored in those receiving rifampin-containing regimens.