Skin Test Conversion Research Articles

Tuberculosis infection among staff at a Canadian community hospital.

To determine risks for tuberculin skin-test conversion among employees of a community hospital in Ontario, Canada. Cohort morbidity study. Of 14 metropolitan Toronto area hospitals surveyed for data on tuberculin skin-test conversions, only one provided tuberculosis (TB) test data on all employees. Between 1991 and June 1994, 24 patients were treated at this hospital for pulmonary TB. The population at risk included those on staff from January 1991 through December 1993 who previously were skin-test negative; they were followed until the end of June 1994. Exposure was estimated (a) based on ranking departments according to an estimate of the number of hours of direct patient contact during a typical day, and (b) based on location of sputum-positive patients. Risks of skin-test conversion among hospital employees with documented prior negative skin tests. A total of 809 skin-test negative employees were followed for 2,084 person-years; 18 employees with skin-test conversions were identified. The overall conversion rate was 0.9% per year (0.86 per 100 person-years). After excluding two conversions attributed to contact with coworkers, the relative risk of conversion was 4.5 (5.5 after adjusting for age and gender) among those in the highest exposure category (> or = 4 hours per day), compared to those in departments ranked as having the lowest exposure (< 2 hours per day). Among those working in wards in which sputum-positive patients were treated, 2.4% converted; the risk of conversion was over six times greater than among those working on wards with no TB patients or in departments with no patient contact, of whom 0.4% converted. Among the emergency room staff, the department in which the greatest number of sputum-positive patients were treated, at least 5% of staff converted. In those instances in which conversions were associated with exposure to a specific TB patient, the involved patients had been in the hospital for at least 4 days prior to being isolated. These results indicate that even in a hospital with few admissions due to tuberculosis, skin-test conversions associated with occupational exposure may occur (Infect Control Hosp Epidemiol 1996; 17:29-35).

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

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.

Dramatic decrease in tuberculin skin test conversion rate among employees at a hospital in New York City

Background: The Centers for Disease Control and Prevention recently issued updated guidelines for preventing the transmission of tuberculosis in health care facilities. Many recommendations, including the use of high-efficiency particulate air filter respirators, are expensive to implement and of unproven efficacy. We therefore reviewed the tuberculin skin test conversion rate among our employees from 1991 to 1993, before introduction of high-efficiency particulate air filter respirators. During this period, several other improvements in tuberculosis control were implemented. Methods: Employee tuberculin test conversion rates were reviewed by 6-month interval from 1991 to 1993. Results: Throughout the study period, several tuberculosis control measures were implemented, including early isolation of patients with suspected cases of tuberculosis in rooms with negative-pressure ventilation, placement of germicidal UV light fixtures into patient rooms and common areas, and use of Technol shields (Technol, Inc., Fort Worth, Texas) (1991), particulate respirators (1992), and dust-mist-fume respirators (1993). With these improvements, the conversion rate among employees fell from 20.7% in the first 6 months of 1991 to 5.8% in the latter half of 1993. Conclusions: The rate of skin test conversion among our employees decreased before introduction of high-efficiency particulate air filter respirators. This suggests that nosocomial spread of tuberculosis can be decreased by means of previously established, less costly methods.

Institutional Control Measures for Tuberculosis in the Era of Multiple Drug Resistance: ACCP/ATS Consensus Conference

Institutional Control Measures for Tuberculosis in the Era of Multiple Drug Resistance: ACCP/ATS Consensus Conference

Tuberculosis Infection-Control Practices in United States Emergency Departments

Study objective: To determine the frequency with which patients with suspected tuberculosis (TB) or TB risk factors present to US emergency departments and to describe current ED TB infection-control facilities and practices. Design: Mailed survey of a sample of EDs in US acute care facilities. Participants: A random sample (n=446) of subjects who responded to a 1992 survey of all US municipal, Veterans Affairs, and university-affiliated hospitals and a 20% random sample of all private hospitals with more than 100 beds conducted by the Centers for Disease Control and Prevention (CDC). Results: We collected data on patient demographics and general ED characteristics, TB isolation facilities and policies, and employee tuberculin skin-testing policies and results. Of 446 facilities surveyed, 305 surveys (68.4%) were returned. The proportions of facilities reporting that patients suspected of having TB are seen daily, weekly, monthly, and less frequently were, respectively, 12.6%, 17.2%, 23.3%, and 46.9%. The proportion of EDs in which indigent patients are cared for on a daily basis was 89%; the homeless, 57.5%; the HIV-infected, 35.9%; IV drug users, 45.4%; and recent immigrants, 30%. Written criteria for isolation of patients with suspected TB at triage or in the ED were in place in 56% and 76% of facilities, respectively. TB isolation rooms fulfilling CDC guidelines were available in triage or waiting areas in 1.7% of facilities and in 19.6% of EDs. Air venting directly outside, high-efficiency particulate air filtration of recirculated air, and UV germicidal lights were used in 21%, 17%, and 8% of general patient care areas of EDs, respectively. At least one ED employee had shown tuberculin skin test conversion in 16.1% of EDs in 1991; this figure was 26.9% in 1992. Conclusion: Patients with TB or at risk for TB are often treated in US EDs, and the risk for transmission of TB in this setting appears to be increasing. Prolonged waiting times and lack of infection-control facilities in EDs may contribute to this problem. Consideration should be given to implementation of policies and facilities recommended by the CDC. [Moran GJ, Fuchs MA, Jarvis WR, Talan DA: Tuberculosis infection-control practices in United States emergency departments. Ann Emerg Med September 1995;26:283-289.]

Underutilization of Isoniazid Chemoprophylaxis in Tuberculosis Contacts 50 Years of Age and Older: A Prospective Analysis

To examine the utilization of chemoprophylaxis for tuberculosis in certain high-risk groups, ie, infected contacts 50 years and older, and to study the safety of isoniazid (INH) preventive therapy in such persons. From 1987 to 1992, two-part questionnaires were sent to each of the regional health offices within the 95 counties of Tennessee to document cases of purified protein derivative skin test conversion or reaction among close contacts of new patients with active tuberculosis. Infected contacts 50 years and older were included in the study. Data collected from these questionnaires were grouped according to age, sex, race, liver functions test (LFT), and whether chemotherapy was completed. Reasons for early discontinuation were also recorded. High values of LFTs were classified in the various groups as either twofold elevation or greater than threefold elevation. Of the 829 responses for persons fitting the criteria for INH chemoprophylaxis, 415 began treatment; 249 (60%) of those completed the full course (9 months) and 166 stopped prematurely. Of the 414 persons (50%) who did not start preventive therapy, 233 (56.5%) respondents listed age as the reason. No patients started on a regimen of therapy developed hepatitis. Of those completing therapy, 6.9% had a rise in liver enzyme values but remained asymptomatic for hepatitis. Liver enzyme level elevation was significantly higher among patients who discontinued therapy, particularly white women, than those who completed the full course. Asymptomatic liver enzyme level elevation (> or = 3 times normal value), private practitioners' preferences, and patients arbitrarily stopping therapy were the leading reasons for incomplete INH preventive therapy. We conclude that 30% of tuberculosis-infected contacts deserving chemoprophylaxis were actually provided the full benefit of INH preventive therapy, indicating underutilization of this prevention strategy, particularly in contacts older than 50 years.

Tuberculosis Surveillance of Community Hospital Employees

To suggest a cost-effective strategy with a high degree of surveillance for the transmission of tuberculosis infection to employees in community hospitals. We performed a cost-benefit analysis of tuberculin skin testing over a 4-year period. The setting was a community hospital in Bronx, NY. The subjects consisted of employees of the hospital who were categorized into high-risk employees defined as individuals who worked daily in patient care and low-risk employees defined as those not directly involved in patient care. All cases of tuberculin skin test conversion among employees were reviewed over a 4-year period. The departments involved, total number of employees, chest radiographic findings, and prophylaxis instituted were noted. The number of employees who were screened over the past 4 years consisted of 897 in 1990, 857 in 1991, 1357 in 1992, and 1316 in 1993. The mean annual conversion rate was 1%, 1.5%, 1.7%, and 1.4% for the 4 years, respectively. Skin test conversions according to job description revealed that of the total number of conversions 42% were from the nursing staff, 6.2% among the physicians and residents, and 52% among the ancillary staff. There was no difference in conversion between medical and nonmedical services such as the gynecology and surgical floors. Since tuberculin conversion rates of high-risk employees and those exposed to infectious tuberculosis cases have been low, we suggested a comprehensive strategy of 6-month tuberculin testing for high-risk employees and yearly testing for low-risk employees and eliminating boosting and repeated testing at 12 weeks in those exposed to infectious cases of tuberculosis.

Isoniazid Preventive Therapy in Areas of High Isoniazid Resistance

<h3>Background:</h3> Previous decision analyses of isoniazid preventive therapy for low-risk tuberculin reactors aged 20 to 34 years have not accounted for the recently increased isoniazid resistance rate. Drug resistance trends could also affect the decision to use isoniazid preventive therapy for patients with recent conversion of tuberculin skin tests who are seronegative for human immunodeficiency virus. <h3>Methods:</h3> A decision analysis was performed with a Markov simulation to assess the difference in life expectancy between those who receive isoniazid preventive therapy and those who do not. Probability estimates were determined from a review of the literature. <h3>Results:</h3> For tuberculin reactors aged 20 to 34 years living in areas with 26% isoniazid resistance, isoniazid preventive therapy increases life expectancy by 2 days. Withholding isoniazid is clearly favored if the isoniazid hepatitis rate is 1.1% and the hepatitis fatality rate exceeds 2.8%. For recent tuberculin converters, isoniazid preventive therapy increases life expectancy by 14 to 17 days, depending on patient age. Withholding isoniazid from converters is favored only if the isoniazid resistance rate exceeds 90% to 98%, according to patient age. Two-way sensitivity analysis of isoniazid-associated hepatitis and hepatitis-related fatality rate did not affect the decision to use isoniazid for recent converters. <h3>Conclusions:</h3> For tuberculin reactors aged 20 to 34 years who are seronegative for human immunodeficiency virus and living in areas with high isoniazid resistance, there is minimal net benefit of isoniazid preventive therapy. The current recommendation to provide isoniazid preventive therapy to this patient population should be reexamined. For recent tuberculin converters aged 20 to 64 years who are seronegative for human immunodeficiency virus, isoniazid preventive therapy provides a small increase in life expectancy. Withholding isoniazid preventive therapy for human immunodeficiency virus—seronegative skin test converters at high risk for isoniazid-induced hepatitis may be considered; preventive therapy is advisable for all other recent converters. (Arch Intern Med. 1995;155:1622-1628)

The Risk for Transmission of Mycobacterium tuberculosis at the Bedside and during Autopsy

To emphasize the differing infectious potentials of a patient with tuberculosis. Hospital ward and autopsy room. An epidemiologic investigation of tuberculin skin test conversions in a clinical setting and during autopsy when results of tuberculin tests done before exposure were available for all participants. Tuberculin skin test results after the discovery of tuberculosis exposure from a patient with unsuspected tuberculosis for comparison with the test results before exposure; culture of sputum and autopsy material for Mycobacterium tuberculosis; and DNA fingerprinting of organisms. Preventive therapy for persons with skin test conversion. None of the 40 skin test-negative health care workers caring for the patient for 3 weeks on an open medical ward showed a skin test conversion, even though they had not used respiratory precautions. By contrast, among personnel present during the 3-hour autopsy, the test results of all five nonreactors converted from negative to positive (mean reaction, 24 mm). Two of these persons had a positive sputum culture 8 weeks later. The DNA fingerprints of all three isolates were identical. A patient who did not transmit tuberculosis before death released a prodigious number of tubercle bacilli during autopsy.

Management of health care workers after inadvertent exposure to tuberculosis: a guide for the use of preventive therapy.

To quantify the protection of previously infected persons from developing tuberculosis after intense exposure. 6 hospitals and 22 nursing homes in which heavy tuberculosis exposure had occurred. Results of tuberculin skin tests before and after exposure and the development of tuberculosis among known reactors, both converters and nonconverters. All converters were given preventive therapy with isoniazid as soon as they could be identified. Nonconverters and previously known reactors were not treated. In 6 hospital outbreaks, largely aborted by prompt preventive therapy, 98 of 336 nonreactors (29%) showed skin test conversion, and, before therapy could be started, 19 (19% [95% CI, 12% to 29%]) had developed tuberculosis. No tuberculosis developed among the 238 nonconverters (0% [CI, 0% to 1.5%]) or the 76 known reactors who were not treated (0% [CI, 0.5% to 2%]). Tuberculosis developed in 5 of 209 known reactors (2.4% [CI, 0.8% to 5.5%]) in 22 nursing homes with heavy exposure, little more than 10 of 921 known reactors (1.1% [CI, 0.5% to 2%]) in 76 homes where there was no exposure (P = 0.17). Healthy persons who remain nonreactive to tuberculin after heavy exposure have escaped infection and require no chemotherapy. However, if exposure is discovered immediately, it is wise to start preventive therapy in particularly heavily exposed non-reactors and discontinue it if the skin test result is still negative at 3 months. Persons who react after exposure fall into three groups: 1) converters, in whom the risk for tuberculosis warrants preventive chemotherapy, regardless of age; 2) reactors with no preexposure test results, who should be treated as converters; and 3) previously known reactors, in whom the risk for tuberculosis generally is too slight to warrant therapy. However, those who are younger than age 35 years, have human immunodeficiency virus infection, are receiving cancer chemotherapy or long-term corticosteroid therapy, or are otherwise immunocompromised should be considered for preventive therapy, regardless of the exposure.

Tuberculin skin test conversion in hospital employees vaccinated with bacille Calmette-Guérin: Recent Mycobacterium tuberculosis infection or booster effect?

Objective: A rise in the incidence of purified protein derivative (PPD) skin test conversions among employees at our medical center between 1991 and 1993 prompted an examination of factors associated with PPD skin test conversion. We focused on the effect of bacille Calmette-Guérin (BCG) vaccination on PPD skin test conversion because of changes in employee health service policies in 1990 regarding testing of persons who had received BCG vaccination. Methods: The study took place in a university teaching hospital employee health service. Charts of employees who had PPD skin test conversion (> 10 mm increase in induration of the PPD response within 2 years if younger than 35 years of age or > 15 mm if older than 35 years of age) between 1988 and 1993 were reviewed for factors that could have influenced PPD skin test conversion and compared with data from 271 randomly selected charts of employees who underwent annual employee assessments in 1993 but did not have PPD skin test conversion. Results: PPD skin test conversions rose from 0.06% ( 1 1604 ) to 1.3% ( sol22 1760 ; p = 0.000001) in employees tested between 1988 and 1993. Of 41 persons with PPD skin test conversion between 1991 and 1993, 29 (71%) had received BCG vaccination. Only 21% of control subjects ( 56 271 ) had received BCG vaccination ( p < 0.000001 for comparison of BCG vaccination among those with PPD skin test conversion with that among control subjects). When BCG recipients were not included as having PPD skin test conversion, there was no significant increase in PPD skin test conversions. Twenty-three BCG recipients had PPD skin test conversion on their second PPD skin tests. Conclusion: A large proportion of PPD skin test conversions at hospitals that employ large numbers of health care workers who have received BCG vaccination may not represent recently acquired tuberculosis. Rather, these conversions may be effects of previous BCG vaccination. Two-step initial PPD skin testing may help to eliminate nearly 80% of such false-positive conversions.

Preventing the nosocomial transmission of tuberculosis.

To study the efficacy of expanded tuberculosis infection control measures consisting primarily of administrative controls. Descriptive case series. University-affiliated, inner-city hospital. Introduction of expanded tuberculosis infection control measures (including an expanded respiratory isolation policy). The number of tuberculosis exposure episodes and skin test conversion rates of health care workers were measured before and after implementation of expanded infection control measures. Tuberculosis exposure episodes (the number of patients who were not placed in respiratory isolation at admission but who subsequently had a diagnosis of acid-fast bacilli smear-positive pulmonary tuberculosis during that admission or within 2 weeks of discharge) were compared for two time periods: the 8 months before and the 28 months after implementation of infection control measures. Tuberculin skin test conversion rates among health care workers were evaluated during a 2.5-year period. After expanded infection control measures were implemented, the number of tuberculosis exposure episodes decreased from 4.4 per month (35 episodes among 103 patient admissions for potentially infectious tuberculosis over 8 months) to 0.6 per month (18 episodes among 358 patient admissions for smear-positive pulmonary tuberculosis over 28 months) (odds ratio, 9.72; 95% CI, 4.99 to 19.25 [P < 0.001]). The cumulative number of days per month that potentially infectious patients with tuberculosis were not in isolation decreased from 35.4 to 3.3 (P < 0.001). A concomitant decrease in tuberculin skin test conversion rates in health care workers was seen; 6-month tuberculin skin test conversion rates decreased steadily from 3.3% (118 conversions in 3579 health care workers; 1/92 to 6/92), 1.7%, 1.4%, 0.6%, to 0.4% (23 conversions in 5153 workers [1/94 to 6/94]) (P < 0.001). Infection control measures effectively prevented nosocomial transmission of tuberculosis to health care workers. Administrative controls appear to be the most important component of a tuberculosis infection control program and should be the first focus of such a program, especially at public hospitals, where resources are most likely to be limited.

Tuberculosis in health care workers at a hospital with an outbreak of multidrug-resistant Mycobacterium tuberculosis

<h3>Objective:</h3> Investigate reports of tuberculosis in health care workers employed at a hospital with an outbreak of multidrug-resistant<i>Mycobacterium tuberculosis</i>. <h3>Design:</h3> Case series of tuberculosis in health care workers, January 1, 1989, through May 31, 1992. Antimicrobial susceptibility testing and restriction fragment length polymorphism analysis of<i>M tuberculosis</i>isolates. Longitudinal analysis of cumulative tuberculin skin test surveillance data. Assessment of infection control. The patients consisted of 361 health care workers who had either serial tuberculin skin tests or tuberculosis. <h3>Results:</h3> Six health care workers, the largest number linked to one multidrug-resistant tuberculosis outbreak, had disease due to<i>M tuberculosis</i>that matched the outbreak strain from hospitalized patients. The two who were seropositive for human immunodeficiency virus died, one of tuberculous meningitis and the other of multiple causes including tuberculosis. The estimated risk of a skin test conversion was positively associated with time and increased by a factor of 8.3 (1979 to 1992). In 1992 the annual risk for workers in the lowest exposure occupational group was 2.4%. In comparison, nurses and housekeepers had relative risks of 8.0 (95% confidence interval, 3.2 to 20.3) and 9.4 (95% confidence interval, 2.7 to 32.3), respectively. Laboratory workers had a relative risk of 4.2 (95% confidence interval, 1.1 to 15.5). Tuberculosis admissions increased, but the hospital had inadequate ventilation to isolate tuberculosis patients effectively. There were lapses in infection control practices. <h3>Conclusions:</h3> Health care workers who were exposed during a hospital outbreak of multidrug-resistant tuberculosis had occupationally acquired active disease. The human immunodeficiency virus—infected health care workers with tuberculosis had severe disease and died. The risk of skin test conversion increased during the study period, and higher exposure occupations had elevated risk. Effective infection control is essential to prevent the transmission of tuberculosis to health care workers. (Arch Intern Med. 1995;155:854-859)

Tuberculosis in Health Care Workers at a Hospital With an Outbreak of Multidrug-Resistant Mycobacterium tuberculosis

Investigate reports of tuberculosis in health care workers employed at a hospital with an outbreak of multidrug-resistant Mycobacterium tuberculosis. Case series of tuberculosis in health care workers, January 1, 1989, through May 31, 1992. Antimicrobial susceptibility testing and restriction fragment length polymorphism analysis of M tuberculosis isolates. Longitudinal analysis of cumulative tuberculin skin test surveillance data. Assessment of infection control. The patients consisted of 361 health care workers who had either serial tuberculin skin tests or tuberculosis. Six health care workers, the largest number linked to one multidrug-resistant tuberculosis outbreak, had disease due to M tuberculosis that matched the outbreak strain from hospitalized patients. The two who were seropositive for human immunodeficiency virus died, one of tuberculous meningitis and the other of multiple causes including tuberculosis. The estimated risk of a skin test conversion was positively associated with time and increased by a factor of 8.3 (1979 to 1992). In 1992 the annual risk for workers in the lowest exposure occupational group was 2.4%. In comparison, nurses and housekeepers had relative risks of 8.0 (95% confidence interval, 3.2 to 20.3) and 9.4 (95% confidence interval, 2.7 to 32.3), respectively. Laboratory workers had a relative risk of 4.2 (95% confidence interval, 1.1 to 15.5). Tuberculosis admissions increased, but the hospital had inadequate ventilation to isolate tuberculosis patients effectively. There were lapses in infection control practices. Health care workers who were exposed during a hospital outbreak of multidrug-resistant tuberculosis had occupationally acquired active disease. The human immunodeficiency virus-infected health care workers with tuberculosis had severe disease and died. The risk of skin test conversion increased during the study period, and higher exposure occupations had elevated risk. Effective infection control is essential to prevent the transmission of tuberculosis to health care workers.

Risk factors for a positive tuberculin skin test among employees of an urban, midwestern teaching hospital.

To determine the prevalence and incidence of and the relative risks for positive tuberculin skin tests among employees of a large, urban teaching hospital. Retrospective cohort study. Barnes Hospital, St. Louis, Missouri. Hospital personnel employed at any time between January 1989 and July 1991. 684 of 6070 employees screened (11.3% [95% CI, 10.4% to 12.1%]) had positive tuberculin skin tests. Factors associated with a positive result were age (odds ratio, 2.02 per decade [CI, 1.87 to 2.18]; P < 0.0001); black race (odds ratio, 1.58 [Cl, 1.26 to 2.00]; P < 0.0001); Asian race (odds ratio, 16.7 [CI, 9.33 to 29.9]; P < 0.0001); Hispanic ethnicity (odds ratio, 9.45 [CI, 3.58 to 25.0]; P < 0.0001); and percentage of low-income persons within the employee's residential postal zone (odds ratio, 1.14 per 10% [CI, 1.05 to 1.23]; P = 0.001). Twenty-nine of 3106 employees who had at least two tests had skin-test conversions (0.93% [CI, 0.60% to 1.3%]); 15 of these conversions (52%) occurred among employees who had no direct contact with patients. Only the percentage of low-income persons within the employee's residential postal zone (odds ratio 1.39 [CI, 1.09 to 1.78]; P = 0.0075) was independently associated with conversion. The most important associations with a positive tuberculin skin test were older age, minority group status, and the proportion of low-income persons within the employee's residential postal zone. Skin-test conversion was independently associated only with the percentage of low-income persons in the employee's postal zone. Stratifying employees according to degree of contact with patients or according to departmental group was not useful in determining risk for a positive tuberculin skin test or for skin-test conversion. For certain groups of employees, an exposure to tuberculosis in the community probably poses a greater risk than exposure in the hospital setting.

Respiratory protection devices

OSHA authority and responsibility have led to the requirement that health care workers potentially exposed to patients with active tuberculosis in situations where engineering controls are not feasible for protection must utilize personal protective equipment at least equivalent to HEPA respirators. ICPs generally believe that this approach is unnecessarily conservative and imposes undue burdens on patient care. The arguments on both sides of this controversy have some merit. Reported cases of tuberculosis and skin-test conversions among health care workers since 1988 and the absence of a demonstrated safe level of exposure have led many to the conclusion that HEPA respirators are justified. On the other side, tuberculosis currently is not a major problem in some areas of the country, and many believe that less stringent personal protective devices (e.g., DM respirators) may provide protection equivalent to HEPA filters--at least in terms of preventing infection if not in terms of filtration efficiency. They believe that the lesser discomfort and lower cost associated with DM respirators justify the argument for a more flexible standard. Perhaps additional research can help to resolve the remaining controversy. Definitive answers are unlikely to surface quickly, however, and it is likely that the controversy and confusion will continue for at least awhile longer.

The natural history of exposure to the imported fire ant ( Solenopsis invicta)

Background: Imported fire ants (IFA) are a common cause of insect venom hypersensitivity in the southeastern United States. The purpose of this study was to determine the sting attack rate and development of specific IgE in an unsensitized population. Methods: Study participants consisted of 137 medical students with limited exposure to IFA-endemic areas who were temporarily training in San Antonio, Tex. Subjects were surveyed for prior IFA exposure with a questionnaire, and IFA-specific IgE was evaluated with RAST and intradermal skin testing. Evaluations were performed on arrival and reported at departure from the endemic area 3 weeks later. Results: One hundred seven subjects completed the study. Field stings were reported in 55 subjects, resulting in a sting attack rate of 51%. In these 55 subjects 53 (96%) reported a pustule or a small local reaction at the sting site, one (2%) reported an isolated large local reaction, and none reported a systemic reaction. At the 3-week follow-up skin test and RAST conversions occurred in seven subjects (13%) and in one subject (1.8%), respectively. Conclusions: Even brief exposures to IFA-endemic areas result in significant sting rates and concurrent rapid development of IFA-specific IgE in 16% of stung subjects. (J A LLERGY C LIN I MMUNOL 1995;95:824-8.) Copyright © 1995 by Mosby–Year Book, Inc.

SHEA-CDC TB Survey, Part II: Efficacy of TB Infection Control Programs at Member Hospitals, 1992

AbstractObjective:To assess the efficacy of current Myco-bacterium tuberculosis control measures.Design:Voluntary questionnaire to members of the Society for Healthcare Epidemiology of America.Results:Healthcare worker (HCW) tuberculin skin-test (TST) conversion rates were significantly higher in larger hospitals ( ≥ 437 beds) (0.9% versus 0.6%; P &lt; 0.05), or in hospitals reporting ≥ 6 TB patients in 1992 (1.2% versus 0.6%; P &lt; 0.05). Among larger hospitals or those hospitals surveyed reporting ≥ 6 TB patients, those without at least three of the four criteria suggested in the 1990 Centers for Disease Control and Prevention (CDC) TB guidelines for acid-fast bacilli (AFB) isolation (specifically, a single-patient room; negative pressure; and air exhausted directly outside) had significantly higher annual TST conversion rates than those with these criteria (1.8% versus 0.6%; P &lt; 0.05). Respiratory therapist or bronchoscopist TST conversion rates were significantly lower in hospitals compliant with the exhaust criteria (1.2% versus 2.8%; P &lt; 0.05). Regardless of hospital characteristic, HCW TST conversion rates did not differ between hospitals in which HCWs used surgical masks or used disposable particulate respirators.Conclusion:Among larger hospitals or hospitals reporting ≥ 6 TB patients per year, failure to comply with the 1990 CDC TB recommendations for AFB isolation room guidelines was associated with higher HCW TST conversion rates. These data suggest that complete implementation of the 1990 CDC TB guidelines would decrease HCWs’ risk of nosocomial transmission of TB in larger hospitals or those reporting more TB patients. However, in nonoutbreak situations, disposable particulate respirators or submicron surgical masks may not offer significantly greater protection to HCWs than surgical masks.

Tuberculosis risk in the hospital dental practice.

Tuberculosis has re-emerged as a serious public health concern. Multidrug-resistant strains and an increase in the number of high-risk groups are posing a difficult problem for health care providers. The risk of TB transmission in hospital dental practices is potentially increasing. A 20-question survey was mailed to the membership of the American Association of Hospital Dentists, addressing various issues relating to tuberculosis. One hundred thirty-two surveys were analyzed. Twelve per cent of respondents reported at least one TB skin test conversion by a dental provider within the past year at their institution. Five respondents reported one dental provider contracting TB through patient contact. Oral TB was reported in 21 cases. Over 34% reported that active TB patients are not isolated to negative-pressure isolation rooms, 45% reported that patients are allowed to frequent public areas, and only 59% believed that drug compliance monitoring was adequate. Over 86% support TB screening in the Hospital Dental Practice. It was concluded that Hospital Dental Practice personnel may be at increased risk for exposure to TB. Dental providers must exercise strict TB prevention and employ meticulous referral and follow-up procedures for high-risk patients.

Evaluation of Infection Control Measures in Preventing the Nosocomial Transmission of Multidrug-Resistant Mycobacterium tuberculosis in a New York City Hospital

AbstractObjective:To evaluate the efficacy of Centers for Disease Control and Prevention (CDC)-recommended infection control measures implemented in response to an outbreak of multidrug-resistant (MDR) tuberculosis (TB).Design:Retrospective cohort studies of acquired immunodeficiency syndrome (AIDS) patients and healthcare workers. The study period (January 1989 through September 1992) was divided into period I, before changes in infection control; period II, after aggressive use of administrative controls (eg, rapid placement of TB patients or suspected TB patients in single-patient rooms); and period III, while engineering changes were made (eg, improving ventilation in TB isolation rooms).Setting:A New York City hospital that was the site of one of the first reported outbreaks of MDR-TB among AIDS patients in the United States.Participants:All AIDS patients admitted during periods I and II. Healthcare workers on nine inpatient units with TB patients and six without TB patients.Results:The epidemic (38 patients) waned during period II and only one MDR-TB patient presented during period III. The MDR-TB attack rate among AIDS patients hospitalized on the same ward on the same days as an infectious MDR-TB patient was 8.8% (19 of 216) during period I, decreasing to 2.6% (5 of 193; P= 0.01) during period II. In a small group of healthcare workers with tuberculin skin test data, conversions during periods II through III were higher on wards with than without TB patients (5 of 29 versus 0 of 15; P= 0.15), although the difference was not statistically significant.Conclusions:Transmission of MDR-TB among AIDS patients decreased markedly after enforcement of readily implementable administrative measures, ending the outbreak. However, tuberculin skin-test conversions among healthcare workers may not have been prevented by these measures. CDC guidelines for prevention of nosocomial transmission of TB should be implemented fully at all US hospitals.