Stool colonization of healthcare workers with selected resistant bacteria.

We examined the carriage of selected resistant bacteria in the stools of healthcare workers who provided direct patient care. Neither vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, nor Clostridium difficile was recovered from the 55 stool specimens collected. A ceftazidime-resistant Citrobacter freundii was isolated from one specimen. We conclude that the stool of healthcare workers is colonized infrequently with these resistant organisms.

Clostridium difficile colonization and diarrhea at a tertiary care hospital.

Clostridium difficile is the major identifiable infectious cause of nosocomial diarrhea. A prospective study was conducted at New England Deaconess Hospital (Boston) to examine risk factors for C. difficile carriage at both admission and follow-up. Specimens from patients admitted to two wards (one medical, one surgical) and three intensive care units (two surgical, one medical) were cultured weekly until discharge. For 89 (18%) of 496 patient admissions, at least one culture was positive. The prevalence of culture positivity within 72 hours of admission was 11%. Risk factors for culture positivity at admission were prior C. difficile diarrhea (adjusted odds ratio [OR] = 9.5), renal insufficiency (OR = 6.7), and recent hospitalization elsewhere (OR = 3.1). Fifteen percent of patients for whom initial cultures were negative and for whom follow-up cultures were performed acquired C. difficile. Admission to the vascular surgery service (relative risk [RR] = 2.3) and liver transplantation (RR = 4.2) were significant risk factors for C. difficile acquisition. Patients asymptomatically colonized on admission had very low risk (1 in 44) for subsequent development of C. difficile diarrhea. In contrast, nine (47%) of 19 patients who acquired toxigenic strains developed C. difficile diarrhea, a finding suggesting that progression to diarrhea occurs early after acquisition or does not occur at all. The relatively high prevalence of culture positivity at admission may be characteristic of tertiary care hospitals and adds to the difficulty of controlling this nosocomial pathogen.

Nosocomial infection in adult patients with sickle cell anemia.

Although the vulnerability of patients with sickle cell disease to infection with encapsulated organisms is well recognized, nosocomial transmission of infection has not been studied in this population. We describe eight serious, nosocomially transmitted infections in four adult patients hospitalized for complications of sickle cell disease, which led to death in one patient and prolonged hospital stays in three others. Although we have not surveyed all patients with sickle cell disease for rates of nosocomial infection, the cases presented suggest that these patients may be at increased risk. Risk can be reduced if health care workers are especially vigilant in adhering to handwashing and other infection control measures when caring for these patients. Additionally, we recommend that a patient with sickle cell disease not share a room with a patient known to have or suspected of having a nosocomial or community-acquired infectious disease.

Nosocomial infection and fatality in medical and surgical intensive care unit patients.

We prospectively studied 526 patients admitted to the medical intensive care unit (MICU) and 799 patients admitted to the surgical intensive care unit (SICU) at a municipal hospital over a 20-month period. Rates of nosocomial infection were higher in the SICU patients (31% vs 24%). The SICU patients had more urinary tract infections, bacteremias, and wound infections, and the MICU patients were older, had higher acute physiology scores on admission and were more often admitted with shock or coma. The SICU patients were more likely to have received prior antibiotic therapy and had significantly higher numbers of endotracheal tubes, arterial lines, central venous lines, and indwelling bladder catheters. Of the 23 variables univariately associated with nosocomial infection, only five remained significant after entry into step-wise regression models. The MICU patients had a higher fatality rate in the MICU than did the SICU patients (18% vs 10%), but the relative risk of a death following nosocomial infection was 3.5 for both groups. Thirty variables were significantly associated with hospital fatality; nine remained significant after analysis by stepwise logistic regression.

Nosocomial bacterial pneumonia: an overview.

Nosocomial pneumonia accounts for 10% to 20% of all nosocomial infections and represents one of the most serious complications of hospitalization. This review focuses on the etiology, pathogenesis, and prevention of nosocomial pneumonia, with emphasis on infection control procedures to prevent and minimize its occurrence.

Risk factors for pneumonia and fatality in patients receiving continuous mechanical ventilation.

We studied risk factors for nosocomial pneumonia and fatality in 233 intensive care unit patients requiring continuous mechanical ventilation. Ventilator-associated pneumonia was diagnosed in 49 (21%) of the 233 patients. Of the 8 risk factors univariately associated with the development of pneumonia, only the presence of an intracranial pressure monitor (p less than 0.002), treatment with cimetidine (p less than 0.01), hospitalization during fall-winter seasons (p less than 0.04), and mechanical ventilator circuit changes every 24 h rather than every 48 h (p less than 0.02) remained significant after stepwise logistic regression. The overall fatality rate for the 49 patients who developed ventilator-associated pneumonia was 55%. Ventilator-associated pneumonia was 1 of 18 variables univariately associated with overall patient fatality, but it was not among the 7 variables present after multivariate analysis. The data delineate risk factors associated with the development of nosocomial pneumonia and fatality in patients receiving continuous mechanical ventilation.

A randomized study comparing a transparent polyurethane dressing to a dry gauze dressing for peripheral intravenous catheter sites.

We studied rates of peripheral intravenous (IV) catheter tip and insertion site colonization after randomly assigning patients to transparent polyurethane (TP) dressings (N = 316) or dry gauze (DG) dressings (N = 421). The study was conducted during both summer and fall seasons, in a facility which lacked air conditioning. All patients had a teflon plastic catheter inserted, maintained and cultured by a member of the IV therapy team; no antibiotic or antiseptic ointments were used. Colonization rates were higher in the summer than in the fall for both catheter tips (9.0% vs 3.5%, p = 0.005) and sites (21.6% vs 7.0%, p = 0.001). During the summer season, the rate of catheter tip colonization with TP dressings was nearly twice that of DG dressings (12.4% vs 6.8%, p = 0.04). Logistic regression analysis indicated that catheter tip colonization was associated with the summer season (odds ratio = 3.0, 95% CI 1.4-6.2) and TP dressings (odds ratio = 1.8, 95% CI 1.1-3.2), and that site colonization was associated with both summer (odds ratio = 4.0, 95% CI 2.2-7.1) and receipt of antibiotics (odds ratio = 1.9, 95% CI 1.1-3.2). Coagulase-negative staphylococci were isolated from 55.5% of the colonized catheter tips and insertion sites. The data suggest that bacterial colonization of peripheral IV catheters is increased in summer, and that use of TP dressings may increase both tip colonization and cost nearly twofold.

Contaminated medication nebulizers in mechanical ventilator circuits. Source of bacterial aerosols.

The contamination rates of medication nebulizers inserted into mechanical ventilator circuits were studied. Semiquantitative techniques were used to sample the reservoir fluid from in-line nebulizers during the first 24 hours after a circuit change. In the initial survey, high levels of contamination (organism concentrations above 10(3)/ml) were present in 13 (68 percent) of the 19 nebulizer reservoirs, and bacterial aerosols were produced by 10 (71 percent) of 14 nebulizers. Gram-negative bacilli were the predominant organisms isolated. Nebulizer contamination originated primarily from reflux of contaminated condensate in the ventilator circuit. When nebulizers were cleaned after each treatment, a reduced rate of contamination was found. Small bacterial aerosols (less than 3 microns in size) were produced in vitro after inoculation of nebulizers with gram-negative bacilli in concentrations isolated from in-use nebulizers. Contaminated in-line medication nebulizers generate small-particle bacterial aerosols that may increase the risk of ventilator-associated pneumonia and therefore should be cleaned or disinfected after each treatment rather than every 24 hours.

Serratia marcescens contamination of antiseptic soap containing triclosan: implications for nosocomial infection.

During a recent investigation in our surgical intensive care unit, we found that several bottles of the antiseptic handwashing soap, OR Scrub, were contaminated with Serratia marcescens. OR Scrub contains 1% triclosan, lanolin, and detergents. The antimicrobial efficacy of OR Scrub was examined in vitro using serial two-fold dilutions of soap inoculated with various concentrations of different nosocomial pathogens. The minimal bactericidal concentration (MBC) of OR Scrub against Pseudomonas aeruginosa and several strains of S. marcescens was less than or equal to 1:2. By comparison, a non-antiseptic soap from the same manufacturer (Wash) and 4% chlorhexidine (Hibiclens) had MBCs for all strains tested of at least 1:64. Time-kill curves confirmed the findings of the initial experiments. This is the first report of extrinsic contamination of antiseptic soap containing triclosan. No infections could be attributed to the contaminated soap, but sporadic outbreaks of Serratia have occurred in the intensive care unit with no identifiable source. Although there have been few studies on the impact of antiseptic soap in reducing nosocomial infection, we question whether a soap with the limitations of OR Scrub should be used in intensive care units or operating rooms.

Pseudobacteremia traced to cross-contamination by an automated blood culture analyzer.

Twenty-three episodes of pseudobacteremia occurring over a seven-month period were traced to cross-contamination by the automated blood culture analyzer (BACTEC 460) used in the microbiology laboratory. An epidemiologic investigation of an unusual cluster of three patients with pseudobacteremia caused by oxacillin-resistant Staphylococcus aureus led to the identification of the problem. Mock trials of the blood culture procedure confirmed that the blood culture analyzer was the source of contamination. After the needle sterilizer was replaced by the manufacturer, the problem of cross-contamination abated. Contamination of sterile blood cultures by an instrument intended to identify bacteremia rapidly may lead to incorrect diagnosis, unnecessary administration of antibiotics and prolonged hospitalization. Because of the widespread use of automated blood culture analyzers in the US, physicians, microbiologists, and infection control personnel should be alert to the possibility of cross-contamination and the subtle way in which it may present.

Contamination of mechanical ventilators with tubing changes every 24 or 48 hours.

We studied the contamination of ventilator circuits in order to assess the need for daily changes of tubing. Patients requiring continuous mechanical ventilation were randomly selected for tubing changes at 24 hours (Group 1) or at 48 hours (Group 2). Samples of inspiratory-phase gas from ventilators with standardized settings were cultured according to the tube-broth method of Edmondson and Sanford. The frequency of positive cultures from 128 ventilators in Group 1 (30 per cent) was not significantly different from that for 112 ventilators in Group 2 (32 per cent). Gram-negative bacteria were most frequently isolated from patient's sputum and ventilator inspiratory-phase gas, but no species predominated in either group of patients. Further studies performed with the Aerotest and Andersen air samplers confirmed that the levels of inspiratory-phase-gas contamination were low in both groups. In addition, quantitative analysis of colonization of the tubing demonstrated no significant increase in colonization between 24 and 48 hours. The absence of a significant difference in inspiratory-phase-gas contamination or tubing colonization suggests that ventilator tubing need be changed only every 48 hours.