Tuberculin skin test and isoniazid prophylaxis among health care workers in high tuberculosis prevalence areas.

The tuberculin skin test (TST) is an important tool for the detection of latent tuberculosis (TB) and the identification of health care workers (HCWs) who require chemoprophylaxis. Although TST is inexpensive, easily available and the preferred test in most TB-prevalent settings, it has recognised limitations, including subjective interpretation, false positivity, cross reactivity with non-tuberculous mycobacteria, administration errors and the requirement for two visits. Given these limitations and the unavailability of better screening tests in resource-limited settings, the acceptance rate for chemoprophylaxis among HCWs has remained low. Furthermore, chemoprophylaxis in these settings is complicated by the high rate of drug-resistant TB, potential adverse reactions, prescription of chemoprophylaxis in undiagnosed active TB patients and the unavailability of follow-up systems provided by occupational health programmes. In the present article, we provide our viewpoint and a practical approach along with existing evidence supporting or discouraging the use of TST and isoniazid chemoprophylaxis for TB screening and management among HCWs in TB-prevalent settings.

The risk of occupational tuberculosis in Serbian health care workers.

SETTING: Health care workers in the Clinical Center of Serbia. OBJECTIVE: To evaluate tuberculosis (TB) incidence by job category comparing the rates of TB in health care workers (HCWs) working in pulmonary departments, other (non-pulmonary) departments, and in the general population in Serbia. DESIGN: Prospective cohort study from 1992 to 2004. Assessment of the relationship between employment in different departments and TB incidence was expressed by relative risk (RR), which was calculated using the annual TB incidence in the population of Serbia as the baseline rate. RESULTS: A total of 24 HCWs developed active TB in the study period. The mean incidence rate was 413.2 per 100000 persons (RR = 12.2) for hospital staff in the pulmonary department and 20.3/100000 (RR = 0.6) for other departments. Nurses and technicians were at 7.8 times higher risk of developing TB than doctors. The mean working period before the onset of illness was 15.1 years (95%CI 5.1-25.1) for HCWs in pulmonary departments and 8.1 years (95%CI 4.6-11.6) in non-pulmonary departments (P = 0.006). CONCLUSION: This study indicates that HCWs were at an increased risk of TB, most likely from nosocomial transmission in high-risk departments.

Management and outcome of tuberculosis in two St Louis hospitals, 1988 to 1994.

OBJECTIVE: To describe management and outcome of tuberculosis (TB) and current practices for isolation in two urban hospitals in the Midwest. DESIGN: Retrospective cohort study. SETTING: Barnes Hospital and Jewish Hospital, tertiary-care and community hospitals affiliated with Washington University School of Medicine in St Louis, Missouri. PATIENTS: All adult patients with a positive culture for Mycobacterium tuberculosis from 1988 to 1994. RESULTS: We identified 122 cases at Barnes and Jewish Hospitals (36.5/100,000 hospital discharges), median age was 59.0 years, 61.5% were non-Caucasian, and 54.9% resided within the city limits. Underlying risk conditions were common: substance abuse (25%), recent TB contact (24%), and foreign birth (13%). Coexistent human immunodeficiency virus infection (8%) was uncommon. Of skin-tested cases, 22% were anergic; of the rest, 22% tested negative. Almost 20% of cases had prior positive skin tests, and thus were preventable, but had not received adequate prophylaxis. Of hospitalized patients with pulmonary TB, 70% received respiratory isolation. Antibiotic resistance was recognized in 16%; only 19% of cases initially received four-drug therapy. TB-related death occurred in 16%. CONCLUSIONS: In this area, TB cases primarily involve traditional risk groups without HIV coinfection. Current infection control practices, diagnostic strategies, and initial treatment regimens are suboptimal. Education about local disease epidemiology is needed to prevent nosocomial TB transmission.

Tuberculosis infection and anergy in hemodialysis patients.

Patients on hemodialysis are at increased risk for developing active tuberculosis (TB) after primary infection. Although this increased risk is well documented, the prevalence of TB infection, as indicated by a positive tuberculin skin test (TST), is not well described. End-stage renal disease is also known to be a risk factor for skin test anergy, but the rate of anergy in hemodialysis patients is unclear. We sought to identify rates of anergy and TST positivity in patients at four hemodialysis units in St Louis, Missouri, from June 1996 through August 1996. Data obtained from patients and medical records included age, years on hemodialysis, medical history, and basic laboratory data. Patients without a history of TB or a positive TST had a TST with Tubersol, as well as candida and tetanus controls, placed by the Mantoux method. Tests were read 48 hours later. Of the patients enrolled at these units, 307 of 331 (93%) were evaluated. Patients had a mean age of 58 years (range, 19 to 91 years) and had been on hemodialysis for a mean of 3.7 years (range, 1 week to 18.7 years). Blacks made up 81% of the population. A history of a positive TST was obtained from 24 patients (8%), and an additional seven (2%) had a history of active TB. Of the 276 patients tested, 93 did not respond to either control antigen, but five of these patients had a positive TST, leaving 88 (32%) anergic. Anergy was related to age, immunosuppressive drug use, and the reagents used, but not to urea reduction ratio. Positive TSTs were found in 17 of 188 of nonanergic patients (9%) (6% of all tested patients). Overall, 48 of 307 patients (16%) had a positive TST or history of TB. TB or a positive TST was associated with liver disease and peptic ulcer disease, but not socioeconomic status. All 17 newly identified TST-positive patients received chest radiographs. No new cases of active TB were found. Only two of 17 of these patients (12%) were started on isoniazid (INH) prophylaxis. We identified high rates of TST positivity and anergy in the hemodialysis patients tested. Hemodialysis patients should receive regular TST screening, and INH prophylaxis needs to be more strongly encouraged. Studies are ongoing to define the rate of TST conversion over time.

Preventing nosocomial infections in the intensive care unit--lessons learned from outcomes research.

Patients in an ICU are at increased risk for a nosocomial infection. Infection control practices to reduce these risks have often been based on scant information. A recent trend to base infection control practices on actual patient outcome data has often provided surprising results. Basic measures such as good handwashing and appropriate patient isolation must be followed. Routine venous catheter placement does not increase the risk of bacteremia, and increases procedure morbidity. The role of different catheter dressings and antibiotic-impregnated catheters in reducing bacteremia is unclear. Nosocomial pneumonias and ventilator-associated pneumonia are common in the ICU. Outcome studies suggest that infrequent changes of ventilatory circuits do not increase the risk of ventilator-associated pneumonia, while allowing substantial cost savings. Manipulation of the pH or flora of the gastrointestinal tract seems to have little influence on patient outcomes, even if there may be a slight reduction in nosocomial pneumonias. Although large randomized trials may be outside the scope of hospital infection control programs and ICUs, any hospital should be able to implement outcomes-based studies of changes in infection control policies and procedures.

Varied approaches to tuberculosis control in a multihospital system.

OBJECTIVES: To document the actual tuberculosis (TB) control policies and procedures in a nonoutbreak setting in a variety of hospitals. To determine if any particular practices are linked to higher rates of employee tuberculin skin-test conversion. DESIGN: Survey of hospital occupational health and infection control practitioners for the year 1994 regarding hospital TB policies. Review of hospital records to verify the number of patients with TB at each hospital and to verify the number of employees with positive tuberculin skin tests. Smoke-stick testing of negative-pressure ventilation rooms. SETTING: A 13-hospital health system in the Midwest. RESULTS: Hospitals ranged in size from 40 to 1,208 beds (median 220) and employed 150 to 6,500 workers (median 875). There were seven rural and six urban centers, including four teaching hospitals. All 13 hospitals had TB control plans, and all performed annual tuberculin skin testing on employees. Annual skin-test positivity rates ranged from 0% to 1.0% (median 0.3%). Negative-pressure ventilation rooms were available in 11 hospitals. The percentage of negative-pressure rooms with effective negative pressure ranged from 44% to 100% (median 95%). Three of the 13 hospitals used high-efficiency particulate air (HEPA) masks as primary personal respiratory protection, and 8 used dust-mist or dust-mist-fume masks. We found no relation between the type of face mask used, number of functional negative-pressure rooms, or hospital TB risk category, and employee skin-test conversion rates. CONCLUSIONS: Considerable variation existed in the TB control policies and procedures between hospitals, but employee TB skin-test conversion rates were low in all settings.

Tuberculin skin testing of hospitalized patients.

OBJECTIVES: We sought to define the prevalence of tuberculin skin test (TST) positivity in a group of newly hospitalized patients, to identify risk factors for positive tests, and to examine the impact of testing on infection control practices. DESIGN: Unblinded cohort study over 5 days in July 1992. SETTING: A 1,000-bed university-affiliated hospital. PATIENTS: All patients admitted (excluding obstetric patients and newborns) were interviewed. Patients without a history of tuberculosis (TB) or a positive TST were offered a TST with Candida and tetanus controls. RESULTS: Of 346 patients offered the test, 21 (6%) had a prior history of TB or a positive TST, and 36 (10%) declined to participate; 279 of the remaining 289 completed the study. Anergy was demonstrated in 94 (33.7%) of 279 patients. New positive TSTs were identified in 19 (10.3%) of 185 nonanergic patients. Of the 19 TST-positive patients, 6 (32%) had infiltrates on chest radiographs and were evaluated for active TB. One patient was treated empirically for active TB, and five received isoniazid prophylaxis. Risk factors for a new positive TST included age (odds ratio [OR], 1.56 per decade of life; P = .021), African American race (OR, 4.81; P = .008), alcohol abuse (OR, 5.53; P = .005), and peptic ulcer disease (OR, 4.53; P = .017). Risk factors for anergy included admission to a surgical service (OR, 2.1; P = .006), current use of steroids (OR, 2.65; P = .005), and human immunodeficiency virus (HIV) infection (OR, undefined; P = .034). CONCLUSIONS: Despite a high rate of anergy, routine tuberculin skin testing identified a substantial number of patients with TB infection who might otherwise have gone unrecognized.

Serious Pseudomonas aeruginosa infections in patients infected with human immunodeficiency virus: a case-control study.

We conducted a case-control study to determine the incidence and clinical features of and risk factors for Pseudomonas aeruginosa infections in patients infected with human immunodeficiency virus (HIV). Twenty-five patients who had 37 episodes of P. aeruginosa infection from 1990 through 1992 were identified. Most of the patients (92%) were homosexual men with low CD4+ lymphocyte counts and a history of AIDS. The annual incidence rates of P. aeruginosa infection were 3.5% (1990), 6.3% (1991), and 8.7% (1992). Most infections were community-acquired (68%) and involved the respiratory tract (73%). Patients were more likely than HIV-infected controls to have AIDS and had more AIDS-defining opportunistic illnesses. The overall mortality was 36%. Recurrent episodes were common (39%). We conclude that P. aeruginosa infections may be an increasing problem in patients with extremely advanced HIV infection. Clinicians should consider including antibiotics with activity against P. aeruginosa in the empirical treatment for suspected bacterial infection in patients with advanced HIV infection.

New insights into the mitochondrial carnitine palmitoyltransferase enzyme system.

Dissection of the mitochondrial carnitine palmitoyltransferase (CPT) enzyme system in terms of its structure/function relationships has proved to be a formidable task. Although no one formulation has gained universal agreement we believe that the weight of evidence supports a model with the following features: a) in any given tissue CPT I and CPT II are distinct proteins; b) CPT I, unlike CPT II, is detergent labile; c) within a species CPT II is expressed body wide, whereas CPT I exists as tissue specific isoforms; d) malonyl-CoA and other CPT I inhibitors probably interact at the catalytic center of the enzyme, not with a regulatory subunit. The amino acid sequences of rat and human CPT II (deduced from cDNA clones) show them to be similar proteins (greater than 80% identity) but encoded by mRNAs of significantly different sizes. Efforts to clone and sequence the cDNA for rat liver CPT I are presently underway.

Cloning, sequencing, and expression of a cDNA encoding rat liver mitochondrial carnitine palmitoyltransferase II.

We report the isolation and characterization of a full-length cDNA encoding rat liver carnitine palmitoyltransferase II (CPT II). Beginning with the purified protein CNBr fragments were generated and sequenced. Corresponding oligonucleotides were used to screen a rat liver cDNA library constructed in the plasmid cloning vector, pcDV. The clone ultimately obtained consisted of a 62 nucleotide 5'-untranslated region, a single open reading frame of 1,974 bases predicting a protein of 658 amino acids (Mr = 74,119), and a 3'-untranslated segment of 260 nucleotides followed by the poly (A) tail. The identity of the cDNA was confirmed by the findings that (a) the open reading frame encoded all three peptides found in the original protein; (b) a fourth peptide synthesized from a portion of the deduced amino acid sequence and used to immunize a rabbit resulted in the generation of an antibody that recognized pure CPT II on a Western blot; (c) in vitro transcription and translation of the cDNA (ligated into pBlue-script KS (+] generated a protein that was specifically immunoprecipitated by anti-CPT II antibody and having a Mr slightly greater than that of mature CPT II; (d) transfection of COS cells with the cDNA subcloned into the expression vector, pCMV4, resulted in a 6-fold induction of mitochondrial CPT II catalytic activity. It seems likely that the de novo synthesized enzyme gains entry into the mitochondrion via a targeting peptide that is subsequently cleaved. The mature protein probably associates (relatively loosely) with the inner membrane through a limited number of membrane spanning domains. The predicted amino acid sequence of CPT II shows strong identity with those of two other acyltransferases, namely, rat liver peroxisomal carnitine octanoyltransferase and porcine choline acetyltransferase.

Inter-tissue and inter-species characteristics of the mitochondrial carnitine palmitoyltransferase enzyme system.

Properties of the carnitine palmitoyltransferase (EC 2.3.1.21) (CPT) enzyme system were compared in isolated mitochondria from a range of tissues in rodents, monkey, and man. Common features were as follows: (a) while membrane-bound, CPT I, but not CPT II, was inhibited reversibly by malonyl-coenzyme A (CoA) and irreversibly by CoA esters of certain oxirane carboxylic acids; (b) the detergent, Tween-20, readily solubilized CPT II in active form while leaving CPT I membrane associated and catalytically functional; (c) octyl glucoside and Triton X-100 released active CPT II but caused essentially complete loss of CPT I activity. Use of [3H]tetradecylglycidyl-CoA, a covalent ligand for CPT I, yielded estimates of the enzyme's monomeric molecular size: approximately 86 kDa in non-hepatic tissues and approximately 90-94 kDa in liver, depending upon species. A polyclonal antibody to purified rat liver CPT II recognized a single protein in each tissue; its apparent molecular mass was approximately 70 kDa in all rat tissues and approximately 68 kDa in all mouse tissues as well as monkey and human liver. On Northern blot analysis a rat liver CPT II cDNA probe detected a single approximately 2.5-kilobase mRNA in all rat and mouse tissues examined. The following points are emphasized. First, CPT I and II are different proteins. Second, within a species CPT II, but not CPT I, is probably conserved across tissue lines. Third, slight variations in size of both enzymes were found in different species, although, at least in the case of CPT II, significant amino acid identity exists among the various isoforms. Fourth, CPT I, unlike CPT II, requires membrane integrity for catalytic function. Finally, the strategic use of detergents provides a simple means of discriminating between the two enzyme activities.

Characterization of the mitochondrial carnitine palmitoyltransferase enzyme system. II. Use of detergents and antibodies.

Exposure of rat liver mitochondrial membranes to octyl glucoside, Triton X-100, or Tween 20 solubilized an active and tetradecylglycidyl-CoA (TG-CoA)-insensitive carnitine palmitoyltransferase (presumed to be carnitine palmitoyltransferase II). The residual membranes after octyl glucoside or Triton X-100 treatment were devoid of all transferase activity. By contrast, Tween 20-extracted membranes were still rich in transferase; this was completely blocked by TG-CoA and thus was presumed to be carnitine palmitoyltransferase I. The residual carnitine palmitoyltransferase activity disappeared from the membranes upon subsequent addition of octyl glucoside or Triton X-100 and could not be recovered in the supernatant fraction. Antibody raised against purified rat liver transferase II (Mr 80,000) recognized only this protein in immunoblots from untreated liver mitochondrial membranes containing both transferases I and II. Tween 20-extracted membranes, which contained only transferase I, did not react with the antibody. Purified transferase II from skeletal muscle (also of Mr 80,000) was readily recognized by the antiserum, suggesting antigenic similarity with the liver enzyme. These and other studies on the effects of detergents on the mitochondrial [3H]TG-CoA binding protein provide further support for the model of carnitine palmitoyltransferase proposed in the preceding paper. They suggest that: 1) carnitine palmitoyltransferases I and II in rat liver are immunologically distinct proteins; 2) transferase I is more firmly anchored into its membrane environment than transferase II; 3) association of carnitine palmitoyltransferase I with a membrane component(s) is necessary for catalytic activity. While carnitine palmitoyltransferase I is a different protein in liver and muscle, it seems likely that both tissues share the same transferase II.