If you have calculated the sample size required for an employee survey or an observational study of departmental practices but found that the number of observations required is larger than the number of employees, chances are the error is due to use of approximation formulae. Many of us unknowingly were taught to use approximations that fail to include the finite population correction factor. Depending on the objective of a study and the proportion of a population sampled, it may be necessary to consider this correction factor in order to estimate standard error and sample size accurately.

During a 2-week period, three infants with a cough lasting at least 8 days with whoops, were admitted to the pediatric unit; Bordetella pertussis was isolated from nasopharyngeal aspirates collected from the three infants. Approximately 1 week later, a nurse working on the same unit developed influenza-like symptoms followed by whooping cough; B pertussis was isolated. Isolates from the nurse and from one of the infants were shown to be indistinguishable by pulsed-field gel electrophoresis. These data demonstrate that B pertussis transmission to healthcare workers is possible and emphasize the need to use respiratory protection devices (Droplet Precautions) for healthcare workers having close contact with infected children.

To determine compliance with nosocomial tuberculosis control measures, 541 healthcare worker observations were made for 52 patients placed in respiratory isolation. Sixty-four total violations were noted, of which 45% occurred in physicians in training. Overall compliance with tuberculosis control measures appeared to be good, but additional educational efforts are warranted.

A survey was conducted to estimate how often healthcare providers were exposed to patients' blood and the percentage of incidents in which patients agreed to human immunodeficiency virus (HIV) testing. Data from 38 hospitals with 53,508 employees revealed 2,244 exposures. Of 1,732 requests for information regarding the HIV status of the source patient, only 77 (6%) resulted in the patient's refusal to consent to an HIV test.

We report the case of a pediatrician who developed meningococcal meningitis after performing endotracheal intubation without protection on a child who was suspected of having meningoencephalitis. This case emphasizes the necessity for healthcare workers who perform high-risk procedures to use personal protection devices (ie, respirators and protective goggles). Unprotected healthcare workers with high exposure to Neisseria meningitidis should receive chemoprophylaxis.

Three patients colonized with vancomycin-resistant Enterococcus were admitted to one or more of three long-term-care facilities. Six point-prevalence surveys revealed no transmission of vancomycin-resistant Enterococcus after a total of 234 days of exposure during which moderately strict infection control measures were implemented. Four of 116 environmental cultures were positive.

To assess the rubella immune status of a cohort of high-risk pregnant women visiting a Midwestern clinic, we retrospectively studied 50 random pregnancies per year from 1990 through 1996. Of 350 patients analyzed, 53 (15.1%) were not immune to rubella, and vaccination opportunities were missed.

A prospective study was undertaken to determine colonization rates, susceptibility profiles, and outcomes in patients with clinical isolates of Acinetobacter baumannii. Fifty percent of patients became colonized with A baumannii, and 29% of these patients had clinical and colonizing isolates with discordant susceptibility profiles, without apparent relation to antibiotic use. Barrier infection control measures are necessary to prevent nosocomial transmission.

Rotavirus environmental contamination in a pediatric unit was investigated. Surfaces were swabbed, then viruses eluted, ultracentrifuged, and detected by polymerase chain reaction (PCR) amplification. Of 55 samples, 25 (46%) tested positive. Rotavirus RNA was more prevalent on surfaces in direct contact with children (thermometers and play mats) than on other environmental surfaces (washbasins, door handles, etc). PCR has proved useful for monitoring rotavirus environmental contamination.

Retrospective chart review of 1,702 patients undergoing laparoscopic cholecystectomy (LC) revealed an overall infection rate of 2.3% and a surgical-site infection rate of 0.4%. Preoperative antimicrobial prophylaxis was received by 79% of patients, but only 33% of these received the agent within 1 hour or less prior to surgery. These facts suggest that antimicrobial prophylaxis may not be necessary for low-risk LC patients.