TST reversion in a BCG-revaccinated population of nursing and medical students, São Paulo, Brazil, 1997-2000.

SETTING: A major university in São Paulo, Brazil, where vaccination against tuberculosis (TB) with bacille Calmette-Guerin (BCG) was routinely offered to first-year medical and nursing students. OBJECTIVES: To estimate the probability of negative tuberculin skin test (TST) results over a 4-year period following BCG revaccination, and to evaluate the effect of factors associated with reversion. DESIGN: Students were enrolled in 1997, initially given a two-step TST, and were retested annually or biannually for the duration of the study. Data on TB exposures and potential risk factors for TST negativity and reversion were collected through annual surveys. A linear mixture survival model was used to estimate the probability of negative TST results over time. RESULTS: Of 159 students, an estimated 20% had a negative TST result despite revaccination, and a further 31% reverted to negative over 4 years of follow-up. No cofactors significantly affected the probability of reversion. CONCLUSION: Overall, in the absence of reported exposure to Mycobacterium tuberculosis, 51% of students revaccinated upon entering nursing or medical school would have a negative TST result by the time they begin their internships. In this recently vaccinated population, reversion was common, suggesting that annual TST screening may remain a useful tool.

A multicenter evaluation of tuberculin skin test positivity and conversion among health care workers in Brazilian hospitals.

SETTING: Four general Brazilian hospitals. OBJECTIVE: To assess the occupational risk of Mycobacterium tuberculosis (TB) in participating hospitals. DESIGN: In phase one of this longitudinal study, a cross-sectional survey documented baseline tuberculin skin test (TST) positivity rates. In phase two, TST conversion rates were evaluated in participants with an initial negative two-step TST. TST conversion data were analyzed to determine risk factors for TB infection using an increase of > or = 10 mm compared to baseline TST. RESULTS: The initial TST positivity rate was 63.1%; the follow-up TST conversion rate was 10.7 per 1000 person-months (p-m). Hospital of employment, recent bacille Calmette-Guerin (BCG) vaccination, nosocomial TB exposure, and employment as a nurse were independent risk factors for TST conversion. Hospitals without TB infection control measures had higher conversion rates than those with control measures (16.0 vs. 7.8/ 1000 p-m, P < 0.001). CONCLUSIONS: This study indicates an important occupational risk of infection in health care settings with a high TB incidence. Longitudinal TST studies are a valuable tool to assess the occupational risk of TB, even in BCG-vaccinated populations, and should be used to direct limited resources for infection control.

Prevalence of nosocomial infections in neonatal intensive care unit patients: Results from the first national point-prevalence survey.

OBJECTIVES: Patients admitted to neonatal intensive care units (NICUs) are at high risk of nosocomial infection. We conducted a national multicenter assessment of nosocomial infections in NICUs to determine the prevalence of infections, describe associated risk factors, and help focus prevention efforts. STUDY DESIGN: We conducted a point prevalence survey of nosocomial infections in 29 Pediatric Prevention Network NICUs. Patients present on the survey date were included. Data were collected on underlying diagnoses, therapeutic interventions/treatments, infections, and outcomes. RESULTS: Of the 827 patients surveyed, 94 (11.4%) had 116 NICU-acquired infections: bloodstream (52.6%), lower respiratory tract (12.9%), ear-nose-throat (8.6%), or urinary tract infections (8.6%). Infants with infections were of significantly lower birth weight (median 1006 g [range 441 to 4460 g] vs 1589 g [range 326 to 5480 g]; P <.001) and had longer median durations of stay than those without infections (88 days [range 8 to 279 days] vs 32 days [range 1 to 483 days]; P <.001). Most common pathogens were coagulase-negative staphylococci and enterococci. Patients with central intravascular catheters (relative risk = 3.81, CI 2.32-6.25; P <.001) or receiving total parenteral nutrition (relative risk = 5.72, CI 3.45-9.49; P <.001) were at greater risk of bloodstream infection. CONCLUSIONS: This study documents the high prevalence of nosocomial infections in patients in NICUs and the urgent need for more effective prevention interventions.

Susceptibility of Panamanian Aotus lemurinus lemurinus to sporozoite-induced Plasmodium falciparum (Santa Lucia) infection.

Aotus monkeys are good models for erythrocyte-induced Plasmodium falciparum and P. vivax infections and have been extensively used in malarial drug and vaccine development. Recently, it has been shown that certain species of Aotus can be infected with sporozoites, and that the degree of susceptibility varies among species. We demonstrate here that Panamanian Aotus lemurinus lemurinus are susceptible to a sporozoite-induced infection, opening the possibility that this species of Aotus could be used as models for testing the efficacy of pre-erythrocytic P. falciparum vaccines and drug candidates directed at the pre-erythrocytic stages of P. falciparum and P. vivax malaria. In this species, we compared sporozoite infection rates. Two of four animals splenectomized prior to infection with sporozoites developed patent parasitemias. Seven of eight animals splenectomized either 7 or 35 days after infection became parasitemic. Additionally, we used a P. falciparum-specific polymerase chain reaction (PCR) method to detect the early appearance of parasitized erythrocytes in the blood prior to detection by conventional microscopy, and found that the parasitemia was detected first in five animals by the PCR method, first in three animals by blood film, with one parasitemia detected simultaneously. We also demonstrated the feasibility of infecting monkeys located in Panama with sporozoites isolated at an insectary in Atlanta, thus documenting the feasibility of similar studies where the insectary and monkey colony are not in the same location. A subsequent attempt to infect these monkeys using sporozoites was not successful, suggesting that this model of human malaria is not yet ready for routine use in vaccine or drug efficacy screening. This model merits further study because of the importance of testing pre-erythrocytic P. falciparum malaria vaccines and drugs in animals.