William R. Jarvis

CDC definitions for nosocomial infections, 1988

The Centers for Disease Control (CDC) has developed a new set of definitions for surveillance of nosocomial infections. The new definitions combine specific clinical findings with results of laboratory and other tests that include recent advances in diagnostic technology; they are formulated as algorithms. For certain infections in which the clinical or laboratory manifestations are different in neonates and infants than in older persons, specific criteria are included. The definitions include criteria for common nosocomial infections as well as infections that occur infrequently but have serious consequences. The definitions were introduced into hospitals participating in the CDC National Nosocomial Infections Surveillance System (NNIS) in 1987 and were modified based on comments from infection control personnel in NNIS hospitals and others involved in surveillance, prevention, and control of nosocomial infections. The definitions were implemented for surveillance of nosocomial infections in NNIS hospitals in January 1988 and are the current CDC definitions for nosocomial infections. Other hospitals may wish to adopt or modify them for use in their nosocomial infections surveillance programs.

CDC Definitions of Nosocomial Surgical Site Infections, 1992: A Modification of CDC Definitions of Surgical Wound Infections

In 1988, the Centers for Disease Control (CDC) published definitions of nosocomial infections However, because of journalistic style and space constraints, these definitions lacked some of the detail provided to National Nosocomial Infections Surveillance (NNIS) System hospitals in the NNIS Manual (unpublished). After the NNIS System hospitals had had considerable experience with the definitions and in response to a request for review by The Surgical Wound Infection Task Force, a group composed of members of The Society for Hospital Epidemiology of America, the Association for Practitioners in Infection Control, the Surgical Infection Society, and the CDC, we slightly modified the definition of surgical wound infection and changed the name to surgical site infection (SSI).

SHEA Guideline for Preventing Nosocomial Transmission of Multidrug-Resistant Strains of Staphylococcus aureus and Enterococcus

patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with sur veillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed. CONCLUSION: Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC’s long-recommended contact precautions (Infect Control Hosp Epidemiol 2003;24:362-386).

Emergence of Vancomycin Resistance in Staphylococcus aureus

BACKGROUND Since the emergence of methicillin-resistant Staphylococcus aureus, the glycopeptide vancomycin has been the only uniformly effective treatment for staphylococcal infections. In 1997, two infections due to S. aureus with reduced susceptibility to vancomycin were identified in the United States. METHODS We investigated the two patients with infections due to S. aureus with intermediate resistance to glycopeptides, as defined by a minimal inhibitory concentration of vancomycin of 8 to 16 microg per milliliter. To assess the carriage and transmission of these strains of S. aureus, we cultured samples from the patients and their contacts and evaluated the isolates. RESULTS The first patient was a 59-year-old man in Michigan with diabetes mellitus and chronic renal failure. Peritonitis due to S. aureus with intermediate resistance to glycopeptides developed after 18 weeks of vancomycin treatment for recurrent methicillin-resistant S. aureus peritonitis associated with dialysis. The removal of the peritoneal catheter plus treatment with rifampin and trimethoprim-sulfamethoxazole eradicated the infection. The second patient was a 66-year-old man with diabetes in New Jersey. A bloodstream infection due to S. aureus with intermediate resistance to glycopeptides developed after 18 weeks of vancomycin treatment for recurrent methicillin-resistant S. aureus bacteremia. This infection was eradicated with vancomycin, gentamicin, and rifampin. Both patients died. The glycopeptide-intermediate S. aureus isolates differed by two bands on pulsed-field gel electrophoresis. On electron microscopy, the isolates from the infected patients had thicker extracellular matrixes than control methicillin-resistant S. aureus isolates. No carriage was documented among 177 contacts of the two patients. CONCLUSIONS The emergence of S. aureus with intermediate resistance to glycopeptides emphasizes the importance of the prudent use of antibiotics, the laboratory capacity to identify resistant strains, and the use of infection-control precautions to prevent transmission.

National nosocomial infections surveillance system (NNIS): Description of surveillance methods

The National Nosocomial Infections Surveillance System (NNIS) is an ongoing collaborative surveillance system sponsored by the Centers for Disease Control (CDC) to obtain national data on nosocomial infections. The CDC uses the data that are reported voluntarily by participating hospitals to estimate the magnitude of the nosocomial infection problem in the United States and to monitor trends in infections and risk factors. Hospitals collect data by prospectively monitoring specific groups of patients for infections with the use of protocols called surveillance components. The surveillance components used by the NNIS are hospitalwide, intensive care unit, high-risk nursery, and surgical patient. Detailed information including demographic characteristics, infections and related risk factors, pathogens and their antimicrobial susceptibilities, and outcome, is collected on each infected patient. Data on risk factors in the population of patients being monitored are also collected; these permit the calculation of risk-specific rates. An infection risk index, which includes the traditional wound class, is being evaluated as a predictor of the likelihood that an infection will develop after an operation. A major goal of the NNIS is to use surveillance data to develop and evaluate strategies to prevent and control nosocomial infections. The data collected with the use of the surveillance components permit the calculation of risk-specific infection rates, which can be used by individual hospitals as well as national health-care planners to set priorities for their infection control programs and to evaluate the effectiveness of their efforts. The NNIS will continue to evolve in finding more effective and efficient ways to assess the influence of patient risk and changes in the financing of health care on the infection rate.

Secular trends in nosocomial primary bloodstream infections in the United States, 1980–1989

More than 25,000 primary bloodstream infections (BSIs) were identified by 124 National Nosocomial Infections Surveillance System hospitals performing hospital-wide surveillance during the 10-year period 1980-1989. These hospitals reported 6,729 hospital-months of data, during which time approximately 9 million patients were discharged. BSI rates by hospital stratum (based on bed size and teaching affiliation) and pathogen groups were calculated. In 1989, the overall BSI rates for small (less than 200 beds) nonteaching, large nonteaching, small (less than 500 beds) teaching, and large teaching hospitals were 1.3, 2.5, 3.8, and 6.5 BSIs per 1,000 discharges, respectively. Over the period 1980-1989, significant increases (p less than 0.0001) were observed within each hospital stratum, in the overall BSI rate and the BSI rate due to each of the following pathogen groups: coagulase-negative staphylococci, Staphylococcus aureus, enterococci, and Candida species. In contrast, the BSI rate due to gram-negative bacilli remained stable over the decade, in all strata. Except for small nonteaching hospitals, the greatest increase in BSI rates was observed in coagulase-negative staphylococci (the percentage increase ranged between 424% and 754%), followed by Candida species (219-487%). In small nonteaching hospitals, the greatest increase was for S. aureus (283%), followed by enterococci (169%) and coagulase-negative staphylococci (161%). Our analysis documents the emergence over the last decade of coagulase-negative staphylococci as one of the most frequently occurring pathogens in BSI.

Risk Factors for Candidal Bloodstream Infections in Surgical Intensive Care Unit Patients: The NEMIS Prospective Multicenter Study

To assess risk factors for development of candidal blood stream infections (CBSIs), a prospective cohort study was performed at 6 sites that involved all patients admitted to the surgical intensive care unit (SICU) for >48 h over a 2-year period. Among 4276 such patients, 42 CBSIs occurred (9.82 CBSIs per 1000 admissions). The overall incidence was 0.98 CBSIs per 1000 patient days and 1.42 per 1000 SICU days with a central venous catheter in place. In multivariate analysis, factors independently associated with increased risk of CBSI included prior surgery (relative risk [RR], 7.3), acute renal failure (RR, 4.2), receipt of parenteral nutrition (RR, 3.6), and, for patients who had undergone surgery, presence of a triple lumen catheter (RR, 5.4). Receipt of an antifungal agent was associated with decreased risk (RR, 0.3). Prospective clinical studies are needed to identify which antifungal agents are most protective and which high-risk patients will benefit from antifungal prophylaxis.

Risk factors for candidemia in neonatal intensive care unit patients.

Background. Candida species are important nosocomial pathogens in neonatal intensive care unit (NICU) patients. Methods. A prospective cohort study was performed in six geographically diverse NICUs from 1993 to 1995 to determine the incidence of and risk factors for candidemia, including the role of gastrointestinal (GI) tract colonization. Study procedures included rectal swabs to detect fungal colonization and active surveillance to identify risk factors for candidemia. Candida strains obtained from the GI tract and blood were analyzed by pulsed field gel electrophoresis to determine whether colonizing strains caused candidemia. Results. In all, 2847 infants were enrolled and 35 (1.2%) developed candidemia (12.3 cases per 1000 patient discharges or 0.63 case per 1000 catheter days) including 23 of 421 (5.5%) babies ≤1000 g. After adjusting for birth weight and abdominal surgery, forward multivariate logistic regression analysis demonstrated significant risk factors, including gestational age <32 weeks, 5‐min Apgar <5; shock, disseminated intravascular coagulopathy, prior use of intralipid, parenteral nutrition, central venous catheters, H2 blockers, intubation or length of stay >7 days before candidemia (P < 0.05). Catheters, steroids and GI tract colonization were not independent risk factors, but GI tract colonization preceded candidemia in 15 of 35 (43%) case patients. Conclusions. Candida spp. are an important cause of late onset sepsis in NICU patients. The incidence of candidemia might be decreased by the judicious use of treatments identified as risk factors and avoiding H2 blockers.

Nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis : a risk to patients and health care workers

OBJECTIVE To determine the factors associated with the development of multidrug-resistant tuberculosis among patients at a New York City Hospital and to investigate possible nosocomial transmission. DESIGN A retrospective case-control study and tuberculin skin test survey. PATIENTS Twenty-three patients with tuberculosis whose isolates were resistant to at least isoniazid and rifampin (case patients) were compared with patients with tuberculosis whose isolates were susceptible to all agents tested (controls). Tuberculin skin test conversion rates were compared among health care workers assigned to wards where patients with tuberculosis were frequently or rarely admitted. SETTING A large, teaching hospital in New York City. MEASUREMENTS Mycobacterium tuberculosis isolates from case patients and controls were typed by restriction fragment length polymorphism analysis. RESULTS Case patients were younger (median age, 34 compared with 42 years; P = 0.006), more likely to be seropositive for HIV (21 of 23 compared with 11 of 23 patients; odds ratio, 11.5; 95% CI, 1.9 to 117), and more likely to have had a previous hospital admission within 7 months before the onset of tuberculosis (19 of 23 compared with 5 of 23 patients; odds ratio, 17.1; CI, 3.3 to 97), particularly on one ward (12 of 23 compared with 0 of 23 patients; odds ratio, undefined; P = 0.002). Health care workers assigned to wards housing case patients were more likely to have tuberculin skin test conversions than were health care workers assigned to other wards (11 of 32 compared with 1 of 47 health care workers; P less than 0.001). Few (6 of 23) case patients were placed in acid-fast bacilli isolation, and no rooms tested had negative pressure. Of 16 available multidrug-resistant isolates obtained from case patients, 14 had identical banding patterns by restriction fragment length polymorphism analysis. In contrast, M. tuberculosis isolates from controls with drug-susceptible tuberculosis had patterns distinct from each other and from those of case patients. CONCLUSIONS These data suggest nosocomial transmission of multidrug-resistant tuberculosis occurred from patient to patient and from patient to health care worker and underscore the need for effective acid-fast bacilli isolation facilities and adherence to published infection control guidelines in health care institutions.

Selected aspects of the socioeconomic impact of nosocomial infections: morbidity, mortality, cost, and prevention.

Approximately 2 million nosocomial infections occur annually in the United States. These infections result in substantial morbidity, mortality, and cost. The excess duration of hospitalization secondary to nosocomial infections has been estimated to be 1 to 4 days for urinary tract infections, 7 to 8.2 days for surgical site infections, 7 to 21 days for bloodstream infections, and 6.8 to 30 days for pneumonia. The estimated mortalities associated with nosocomial bloodstream infections and pneumonia are 23.8% to 50% and 14.8% to 71% (overall), or 16.3% to 35% and 6.8% to 30% (attributable), respectively. The estimated average costs of these infections are