Nosocomial Transmission of Mycobacterium tuberculosis: Role of Health Care Workers in Outbreak Propagation

Abstract

To investigate an outbreak of tuberculosis (TB) among health care workers (HCWs) at a county hospital, all patients with culture-confirmed TB on wards A and B and all HCWs working at least one shift on these wards from January 1991 through March 1992 were studied. Tuberculin skin test conversions occurred in 30% (ward A) and 48% (ward B) of HCWs; 8 developed active TB. Workers exposed for at least one shift to workers or patients with active TB were more likely to have skin test conversion than were workers who were not exposed (ward A exposure relative risk [RR] for workers = 2.8, P = .005, and for patients = 2.2, P > .5; ward B exposure RR for workers = 2.8, P < .001, and for patients = 5.3, P < .001). Underlying conditions and performing charting activities in the nurses' work room were associated with progression to active TB among infected workers. Transmission was facilitated by delays of < or = 2.5 months in treatment of workers with skin test conversion or TB symptoms.

Evaluación de la respuesta a la tuberculina en estudiantes del área de la salud

“…La reemergencia de la TB en los paí-ses desarrollados, la aparición de cepas resistentes y la coinfección con el HIV han despertado nuevamente el interés sobre los riesgos profesionales del personal de salud expuesto a M. tuberculosis (2)(3)(4)(5)(6)(7)(8). La mayoría de los estudios publicados se han hecho con médicos o enfermeras en ejercicio (4, 7, 13-15), pero pocos han evaluado el riesgo de los estudiantes de pregrado en los diferentes programas de formación profesional (5,16).…”

“…Múltiples investigaciones han indagado sobre el riesgo de que el personal de salud desarrolle TB y se ha evaluado tanto el riesgo anual de infección en este personal mediante la conversión de la tuberculina como el riesgo de desarrollar la enfermedad a consecuencia de la transmisión nosocomial (2)(3)(4)(5)(6)(7)(8). Entre los factores que han contribuido a dicha transmisión se encuentran la convergencia en instituciones hospitalarias de pacientes altamente susceptibles, como los infectados por el VIH, el retraso en el diagnóstico y en la administración del tratamiento, la gestión inadecuada para garantizar el aislamiento respiratorio y las precauciones inadecuadas por parte del personal de salud durante procedimientos que inducen tos en los pacientes (9).…”

HETA 92-0232-2767, Grady Memorial Hospital, Atlanta, Georgia.

“…For purposes of analysis, age was defined as the worker's age at the midpoint of the study period (May 1, 1991) and salary was defined as the worker's average hourly salary over the study period. For the multivariate analysis, time employed in an occupational classification was calculated as the difference (in days) between date of hire (or, if hired before the beginning of the study, January 1,1990) and a termination date assigned based on the last quarter for which payroll records were available. For descriptive analysis, duration of employment (in years) was calculated based on date of hire and number of quarters the worker was an active employee at GMH.…”

The Changing Face of the Epidemiology of Tuberculosis due to Molecular Strain Typing: A Review

“…In contrast to most PCR-based typing methods, mixed-linker polymerase chain reaction (ML-PCR) typing sometimes generates more bands than traditional fingerprinting and can be applied directly on smearpositive clinical specimens. The reproducibility and applicability of the method using it directly in clinical samples for screening of TB-patients still has to be proven but the PCR-based RFLP method was used on TB-cultures derived from renal transplant patients to demonstrate an outbreak of TB in a transplant unit (Jereb et al 1993) and to demonstrate nosocomial transmission of M. tuberculosis in an outbreak among health care workers (Zaza et al 1995). Another elegant method for strain typing of M. tuberculosis strains is based on detection of DNA polymorphism in the DR cluster and is called "direct variable repeat polymer chain reaction" (DVR-PCR, Groenen et al 1993).…”