Socioeconomic impact on device-associated infections in limited-resource neonatal intensive care units: findings of the INICC.

PURPOSE: To evaluate the impact of country socioeconomic status and hospital type on device-associated healthcare-associated infections (DA-HAIs) in neonatal intensive care units (NICUs). METHODS: Data were collected on DA-HAIs from September 2003 to February 2010 on 13,251 patients in 30 NICUs in 15 countries. DA-HAIs were defined using criteria formulated by the Centers for Disease Control and Prevention. Country socioeconomic status was defined using World Bank criteria. RESULTS: Central-line-associated bloodstream infection (CLA-BSI) rates in NICU patients were significantly lower in private than academic hospitals (10.8 vs. 14.3 CLA-BSI per 1,000 catheter-days; p < 0.03), but not different in public and academic hospitals (14.6 vs. 14.3 CLA-BSI per 1,000 catheter-days; p = 0.86). NICU patient CLA-BSI rates were significantly higher in low-income countries than in lower-middle-income countries or upper-middle-income countries [37.0 vs. 11.9 (p < 0.02) vs. 17.6 (p < 0.05) CLA-BSIs per 1,000 catheter-days, respectively]. Ventilator-associated-pneumonia (VAP) rates in NICU patients were significantly higher in academic hospitals than in private or public hospitals [13.2 vs. 2.4 (p < 0.001) vs. 4.9 (p < 0.001) VAPs per 1,000 ventilator days, respectively]. Lower-middle-income countries had significantly higher VAP rates than low-income countries (11.8 vs. 3.8 per 1,000 ventilator-days; p < 0.001), but VAP rates were not different in low-income countries and upper-middle-income countries (3.8 vs. 6.7 per 1,000 ventilator-days; p = 0.57). When examined by hospital type, overall crude mortality for NICU patients without DA-HAIs was significantly higher in academic and public hospitals than in private hospitals (5.8 vs. 12.5%; p < 0.001). In contrast, NICU patient mortality among those with DA-HAIs was not different regardless of hospital type or country socioeconomic level. CONCLUSIONS: Hospital type and country socioeconomic level influence DA-HAI rates and overall mortality in developing countries.

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.

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.

Are US hospitals making progress in implementing guidelines for prevention of Mycobacterium tuberculosis transmission?

BACKGROUND: Outbreaks of tuberculosis (TB) in hospitals have occurred when the Centers for Disease Control and Prevention (CDC) guideline recommendations for preventing the transmission of Mycobacterium tuberculosis were not fully implemented. OBJECTIVE: To determine whether US hospitals are making progress in implementing the CDC guidelines for preventing TB. METHODS: In 1992, we surveyed all public (city, county, Veterans Affairs, and primary medical school-affiliated) US hospitals (n = 632) and 444 (20%) random samples of all private hospitals with 100 beds or more. In 1996, we resurveyed 136 random samples (50%) of all 1992 respondent hospitals with 6 or more TB admissions in 1991. RESULTS: Of the 1076 hospitals surveyed in 1992, 763 (71%) respondents returned a completed questionnaire. Among these, 536 (71%) of 755 reported having rooms that met CDC criteria for acid-fast bacilli isolation, ie, negative air pressure, 6 or more air exchanges per hour, and air directly vented to the outside. The predominant respiratory protective device for health care workers was nonfitted surgical mask and attending physicians were infrequently (50%) included in tuberculin skin-testing programs. In the 1996 resurvey, 103 (76%) of 136 respondents returned a completed questionnaire. Of these, 99 (96%) reported having rooms that met CDC criteria for acid-fast bacilli isolation. The N95 respiratory protective devices were predominantly used by health care workers, and attending physicians were increasingly (69%) included in the hospitals' tuberculin skin-testing programs. CONCLUSIONS: Most US hospitals are making progress in the implementation of CDC guidelines for preventing the transmission of M tuberculosis.

Bloodstream infections with vancomycin-resistant enterococci.

OBJECTIVES: To describe the population in whom bloodstream infections with vancomycin-resistant enterococci occur and the clinical and microbiologic features of infection. METHODS: From June 1, 1991, to January 31, 1994, 73 patients with bloodstream infections with vancomycin-resistant enterococci were identified by retrospective review of hospital charts and microbiology records. RESULTS: Fifty-two (73%) of 71 patients with evaluable data were hospitalized in an intensive care, unit, the adult oncology unit, or the acquired immunodeficiency syndrome unit. Before the development of the bloodstream infection with vancomycin-resistant enterococci, patients were hospitalized and received antibiotics for a median of 26 and 25.5 days, respectively. A hematologic malignancy, respiratory failure, or renal failure requiring dialysis was present in 59 patients (83%). Acute Physiology and Chronic Health Evaluation II scores of the patients ranged from 6 to 35 (median, 17). Forty-five (63%) of the patients died. Compared with 37 patients who had only a single positive blood culture, the 34 patients with 2 or more blood cultures positive for vancomycin-resistant enterococci more often were neutropenic or had acquired immunodeficiency syndrome (74% vs 35%; P = .002). CONCLUSIONS: Bloodstream infections with vancomycin-resistant enterococci predominantly affect severely ill patients who have received extensive antibiotic treatment during a prolonged hospitalization. Immunocompromised patients are more likely to have a persistent blood-stream infection with vancomycin-resistant enterococci.

Outbreak of invasive group A streptococcal infections in a nursing home. Lessons on prevention and control.

OBJECTIVE: Nine outbreaks of group A streptococcal (GAS) infections in nursing homes were reported to the Centers for Disease Control (Atlanta, Ga) during the past two winters. We conducted an intensive epidemiologic and laboratory investigation of one of these outbreaks to determine clinical characteristics, risk factors for transmission and infection, and methods of control and prevention. METHODS: Cases were detected using cultures and serologic tests. Matched case-control and retrospective cohort studies were performed to determine risk factors for infection. RESULTS: Between December 13, 1989, and January 31, 1990, 16 (20%) of 80 residents, and three (7%) of 45 staff, were infected with GAS. Eleven of the residents had invasive disease and four died. Isolates were available from four persons; all were serotype M-1, T-1. There was strong spatial clustering of cases within the nursing home; having a roommate with prior infection was the most important risk factor. Residents with preexisting decubiti had a reduced risk of infection, perhaps because of stricter infection control practices in their care. No evidence was found for common-source transmission of infection. No further cases occurred after improvement of infection control practices and administration of prophylactic antimicrobials to all residents and staff. CONCLUSIONS: Invasive GAS disease is increasing nationwide, and is a potentially serious problem in the growing and high-risk setting of nursing homes. These data suggest that, in this outbreak, a virulent GAS strain was introduced, with subsequent person-to-person transmission. Adherence to infection control practices can prevent or control GAS outbreaks. Prophylactic antimicrobials may be an effective adjunct to control severe or ongoing outbreaks.

Tuberculosis in health care workers at a hospital with an outbreak of multidrug-resistant Mycobacterium tuberculosis.

OBJECTIVE: Investigate reports of tuberculosis in health care workers employed at a hospital with an outbreak of multidrug-resistant Mycobacterium tuberculosis. DESIGN: Case series of tuberculosis in health care workers, January 1, 1989, through May 31, 1992. Antimicrobial susceptibility testing and restriction fragment length polymorphism analysis of M tuberculosis isolates. Longitudinal analysis of cumulative tuberculin skin test surveillance data. Assessment of infection control. The patients consisted of 361 health care workers who had either serial tuberculin skin tests or tuberculosis. RESULTS: Six health care workers, the largest number linked to one multidrug-resistant tuberculosis outbreak, had disease due to M tuberculosis that matched the outbreak strain from hospitalized patients. The two who were seropositive for human immunodeficiency virus died, one of tuberculous meningitis and the other of multiple causes including tuberculosis. The estimated risk of a skin test conversion was positively associated with time and increased by a factor of 8.3 (1979 to 1992). In 1992 the annual risk for workers in the lowest exposure occupational group was 2.4%. In comparison, nurses and housekeepers had relative risks of 8.0 (95% confidence interval, 3.2 to 20.3) and 9.4 (95% confidence interval, 2.7 to 32.3), respectively. Laboratory workers had a relative risk of 4.2 (95% confidence interval, 1.1 to 15.5). Tuberculosis admissions increased, but the hospital had inadequate ventilation to isolate tuberculosis patients effectively. There were lapses in infection control practices. CONCLUSIONS: Health care workers who were exposed during a hospital outbreak of multidrug-resistant tuberculosis had occupationally acquired active disease. The human immunodeficiency virus-infected health care workers with tuberculosis had severe disease and died. The risk of skin test conversion increased during the study period, and higher exposure occupations had elevated risk. Effective infection control is essential to prevent the transmission of tuberculosis to health care workers.

Clostridium difficile. Colonization and toxin production in a cohort of patients with malignant hematologic disorders.

We examined 45 (80%) of 56 consecutive adult patients with malignant hematologic disorders who were hospitalized during a 15-week period at Emory University Hospital, Atlanta. Stool samples for Clostridium difficile culture and cytotoxin assay were obtained on admission and then weekly during each patient's hospitalization. On admission, four patients had detectable C difficile in their stool samples, which was associated with prior antimicrobial use but not with prior cancer chemotherapy. One of the four patients with positive stool samples also had toxin present in the stool sample and was the only one with diarrhea. Eight (36%) of 22 patients hospitalized for one or more weeks had C difficile isolated from at least one stool specimen. The positive cultures showed no clustering in time, and no risk factors were identified for colonization. Only seven of 15 culture-positive stool samples and three of seven toxin-positive samples were associated with diarrhea.

Antimicrobial resistance in Staphylococcus aureus.

Recognized since 1883 as a common cause of infection, Staphylococcus aureus' preantimicrobial-era bacteremia mortality rate was 82%. The mortality of that era threatens to return as evidence of growing vancomycin resistance undermines the utility of vancomycin therapy. Successful treatment of S. aureus infections requires knowledge of its antimicrobial resistance capacity.

Nosocomial outbreaks: the Centers for Disease Control's Hospital Infections Program experience, 1980-1990. Epidemiology Branch, Hospital Infections Program.

From January 1980 to July 1990, the Hospital Infections Program of the Centers for Disease Control conducted 125 on-site epidemiologic investigations of nosocomial outbreaks. Seventy-seven (62%) were caused by bacterial pathogens, 11 (9%) were caused by fungi, 10 (8%) were caused by viruses, five (4%) were caused by mycobacteria, and 22 (18%) were caused by toxins or other organisms. The majority of fungi and mycobacterial outbreaks occurred since July 1985. Fourteen (11%) outbreaks were device related, 16 (13%) were procedure related, and 28 (22%) were product related. The proportion of outbreaks involving products, procedures, or devices increased from 47% during 1980-1985 to 67% between 1986 and July 1990. Recent outbreaks have shown that packed red blood cell transfusion-associated Yersinia enterocolitica sepsis results from contamination of the blood by the asymptomatic donor; that povidone-iodine solutions can become intrinsically contaminated and cause outbreaks of infection and/or pseudoinfection; and that rapidly growing mycobacteria can cause chronic otitis media, surgical wound infection, and hemodialysis-associated infections. These and other outbreaks demonstrate how epidemiologic and laboratory investigations can be combined to identify new pathogens and sources of infection and ultimately result in disease prevention.

Analysis of risk factors for surgical wound infections following vascular surgery.

Although surgical wound infections (SWI) following implantation of prosthetic devices can be catastrophic and often require removal of the prosthesis, few studies have identified risk factors for these infections. We conducted a prospective multicenter study to identify risk factors for SWI. Of 561 vascular surgery patients enrolled in the study, 23 (4.1%) developed SWI. Multivariate analysis using logistic regression analyses identified surgery on lower extremities, delayed surgery, diabetes mellitus, past history of vascular surgery, and short antimicrobial prophylaxis (three doses of cefamandole) as independent risk factors for SWI. Consequences of SWI were serious; two (9%) died, 11 (48%) required reoperation, and five (22%) had their prosthesis removed. A risk index was developed using the independent risk factors for SWI identified by logistic regression analyses. When no risk factors were present, no SWI was observed (0 of 100), and the rate of SWI increased from 2.5% when one risk factor was present to 53.8% (7 of 13) when greater than or equal to 4 risk factors were present.

Serratia marcescens surgical wound infection following breast reconstruction.

Surgical wound infections due to gram-negative bacilli have been rarely reported following breast implant surgery. From April to November 1989, four patients from one plastic surgeon's practice developed Serratia marcescens surgical wound infection (SWI) following breast reconstruction procedures with implantation of six expandable mammary implants. All six implants were removed for unabated S. marcescens SWI. Symptoms developed 13-161 days (median, 66 days) after surgery. When compared with nonexpandable silicone breast implants used during the period November 1, 1988, to October 31, 1989, expandable implants were associated with a greater risk of S. marcescens SWI (4/10 versus 0/11 patients, p = 0.04). Epidemiologic studies revealed that infection was associated with saline expansion of the implants performed in the surgeon's office. S. marcescens was cultured from a bag of commercial saline used on at least two of the four patients with SWI; the isolate from the saline and the three available patient isolates had identical serotype (O-undetermined:H4) and antimicrobial susceptibility patterns. Review of office procedures revealed that hands were not routinely washed before and aseptic technique was not used during the expansion procedure. Cultures of unopened bags of saline and an unused expandable implant were sterile. We hypothesize that multiple use of saline bags and nonsterile expansion technique extrinsically contaminated saline solutions and resulted in implant and/or surgical site infection. This investigation underscores the importance of avoiding multiple use of solutions intended for single use and of using aseptic technique when manipulating prosthetic devices.

Prevalence and incidence of human immunodeficiency virus among patients undergoing long-term hemodialysis. The Cooperative Dialysis Study Group.

PURPOSE: The purpose of this voluntary multicenter study was to estimate the prevalence and incidence of human immunodeficiency virus (HIV) infection and the risk of nosocomial transmission of HIV in hemodialysis patients in the United States. PATIENTS AND METHODS: In June 1986, we began collecting epidemiologic data, risk factor information, and serum for HIV antibody testing from long-term hemodialysis patients on entry into the study and 1 year later. RESULTS: Initial data and specimens were collected from 1,324 patients in 28 dialysis centers in 12 states. On entry, 26 were positive or equivocal by enzyme immunoassay; 13 of these were positive by Western blot assay (overall seroprevalence 0.98%). Seroprevalence was higher for patients tested in eight centers located in areas from which a high cumulative incidence of acquired immunodeficiency syndrome has been reported (500 or more cases per 1 million persons) than for patients in other areas (10 of 387 [2.6%] versus three of 937 [0.3%]; p = 0.00048). According to their dialysis records, all 13 of the Western blot-positive patients had received transfusions. Seropositive patients were not more likely to have received a transfusion than seronegative patients (13 of 13 versus 1,038 of 1,311; p = 0.08). The confidential risk factor questionnaire was completed by 1,206 (91%) patients including nine of 13 (69%) of the seropositive patients. A question on sharing needles for injection of drugs was answered by 1,158 patients; seropositive patients were more likely to report they had shared needles than seronegative patients (five of nine versus 17 of 1,149; p = 0.0000002). After 1 year of follow-up, data were collected from 667 patients, including 254 negative patients who underwent dialysis at centers with seropositive patients. None of the previously seronegative patients seroconverted, yielding an incidence rate of 0% (upper limit of 95% confidence interval = 0.45%). No case of possible nosocomial transmission was identified. CONCLUSION: These results suggest that use of long-standing infection control precautions is effective minimizing the risk of transmission of HIV in hemodialysis settings.

Pseudomonas fluorescens bacteremia from blood transfusion.

In October 1980, two units of blood contaminated with Pseudomonas fluorescens caused septic transfusion reactions in two recipients at a Chicago hospital; one patient died. Both units had been purchased from the same blood center. Investigation at the blood center and at other hospitals it supplied revealed another fatal case of P. fluorescens sepsis that had occurred one year earlier. Despite extensive environmental culturing at the blood center, the source of P. fluorescens was not identified. However, comparison of the interval between collection and administration of contaminated and non-contaminated units indicated that prolonged storage was a risk factor that may have caused clustering of cases in one hospital. Laboratory studies showed that small inocula of P. fluorescens proliferated in refrigerated fresh whole blood and reached 10(6) to 10(7) colony-forming units per milliliter seven days after incubation. These data suggest that prolonged storage of blood may be an important risk factor for the development of transfusion-related sepsis.

Nosocomial infection rates in adult and pediatric intensive care units in the United States. National Nosocomial Infections Surveillance System.

To determine which intensive care unit (ICU) infection rate may be best for interhospital and intrahospital comparisons and to assess the influence of invasive devices and type of ICU on infection rates, we analyzed data from the National Nosocomial Infections Surveillance System. From October 1986 to December 1990, 79 hospitals reported 2,334 hospital-months of data from 196 hospital units. The median overall infection rate was 9.2 infections per 100 patients. However, this infection rate had a strong positive correlation with average length of ICU stay (r = 0.60, p less than 0.0001). When patient-days was used in the denominator, the median overall nosocomial infection rate was 23.7 infections per 1,000 patient-days. Although there was a marked reduction in the correlation with average length of stay, this rate had a strong positive correlation with device utilization (r = 0.59, p less than 0.0001). To attempt to control for average length of stay and device utilization, we examined device-associated nosocomial infection rates. Central line-associated bloodstream infection rates, catheter-associated urinary tract infection rates, and ventilator-associated pneumonia rates varied by ICU type. The distributions of device-associated infection rates were different between some ICU types and were not different between others (coronary and medical ICUs or medical-surgical and surgical ICUs). Comparison of device-associated infection rates and overall device utilization identified hospital units with outlier infection rates or device utilization. These data show that: (1) choice of denominator is critical when calculating ICU infection rates; (2) device-associated infection rates vary by ICU type; and (3) intrahospital and interhospital comparison of ICU infection rates may best be made by comparing ICU-type specific, device-associated infection rates.

Comparison of rates of nosocomial infections in neonatal intensive care units in the United States. National Nosocomial Infections Surveillance System.

To determine nosocomial infection (NI) rates among neonatal intensive care units (NICUs) that are useful for interhospital comparison, we analyzed data reported in 1986-1990 from 35 hospitals that have level III NICUs and used standard National Nosocomial Infections Surveillance protocols and NI site definitions. Overall rates of NI were calculated as the number of NI per 100 patients (overall NI patient rates) or the number of NI per 1,000 NICU patient-days (overall NI patient-day rates). A strong positive association was found between overall NI patient rates and the neonates' average length of stay, a marker for duration of exposure to important risk factors. No correlation was found between overall NI patient-day rates and average length of stay. However, a strong positive correlation between overall NI patient-day rates and a measure of device utilization (total device-days/total patient-days x 100) was found. Additionally, a positive correlation between overall NI patient rates and device utilization was found. Stratification among the three birthweight groups (less than 1,500 g, 1,500-2,500 g, greater than 2,500 g) did not eliminate the need to control for variations in these factors among NICUs. Device-associated, device-day infection rates, calculated as the number of umbilical or central line-associated blood-stream infections per 1,000 umbilical or central line-days and the number of ventilator-associated pneumonias per 1,000 ventilator days, were not correlated with a unit's site-specific device utilization. These data suggest that calculation of device-associated NI rates in NICUs using device-days as the denominator helps to control for the duration of exposure to the primary risk factor and will be more meaningful for purposes of interhospital comparison.

Nosocomial infections in elderly patients in the United States, 1986-1990. National Nosocomial Infections Surveillance System.

We analyzed 101,479 nosocomial infections in 75,398 adult patients (greater than 15 years) that were reported to the National Nosocomial Infections Surveillance (NNIS) system between 1986 and 1990 by 89 hospitals using the NNIS hospital-wide surveillance component. Overall, 54% of the infections occurred in elderly patients (greater than or equal to 65 years). In the elderly, 44% of the infections were urinary tract infections (UTIs), 18% were pneumonias, 11% were surgical wound infections (SWIs), 8% were bloodstream infections (BSIs), and the remainder were infections at other sites. When we compared the infections in elderly patients with those in younger adult patients, ages 15 to 64 years, a far greater percentage of the infections in elderly patients were UTIs, and there were more pneumonias than SWIs. Elderly and younger patients with ventilator-associated pneumonia were about 1.5 times more likely to develop a secondary BSI than those with pneumonia not associated with ventilator use. When the pathogens isolated from the infections were compared to those reported to the NNIS system in 1984, the percentage that were coagulase-negative staphylococci had increased in both elderly and younger patients. The patient died in 12% of all of the infections. Surveillance personnel reported that 54% of the infections in elderly infected patients who died were related to death compared with 59% in younger infected patients who died. When the infection was related to the patient's death, it was most often pneumonia or a BSI. The risk of an infection-related death was significantly higher when the infected patient developed a secondary BSI. Infection prevention efforts should target infections that occur frequently, are amenable to intervention, and have an adverse outcome.

Secular trends in nosocomial primary bloodstream infections in the United States, 1980-1989. National Nosocomial Infections Surveillance System.

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.

The National Nosocomial Infections Surveillance System: plans for the 1990s and beyond.

The National Nosocomial Infections Surveillance (NNIS) System is an ongoing collaborative surveillance system among the Centers for Disease Control (CDC) and United States hospitals to obtain national data on nosocomial infections. This system provides comparative data for hospitals and can be used to identify changes in infection sites, risk factors, and pathogens, and develop efficient surveillance methods. Data are collected prospectively using four surveillance components: hospital-wide, intensive care unit, high-risk nursery, and surgical patient. The limitations of NNIS data include the variability in case-finding methods, infrequency or unavailability of culturing, and lack of consistent methods for post-discharge surveillance. Future plans include more routine feedback of data, studies on the validity of NNIS data, new components, a NNIS consultant group, and more rapid data exchange with NNIS hospitals. Increasing the number of NNIS hospitals and cooperating with other agencies to exchange data may allow NNIS data to be used better for generating benchmark nosocomial infection rates. The NNIS system will continue to evolve as it seeks to find more effective and efficient ways to measure the nosocomial infection experience and assess the influence of patient risk, changes in the delivery of hospital care, and changes in infection control practices on these measures.

Surgical wound infection rates by wound class, operative procedure, and patient risk index. National Nosocomial Infections Surveillance System.

To perform a valid comparison of rates among surgeons, among hospitals, or across time, surgical wound infection (SWI) rates must account for the variation in patients' underlying severity of illness and other important risk factors. From January 1987 through December 1990, 44 National Nosocomial Infections Surveillance System hospitals reported data collected under the detailed option of the surgical patient surveillance component protocol, which includes definitions of eligible patients, operations, and nosocomial infections. Pooled mean SWI rates (number of infections per 100 operations) within each of the categories of the traditional wound classification system were 2.1, 3.3, 6.4, and 7.1, respectively. A risk index was developed to predict a surgical patient's risk of acquiring an SWI. The risk index score, ranging from 0 to 3, is the number of risk factors present among the following: (1) a patient with an American Society of Anesthesiologists preoperative assessment score of 3, 4, or 5, (2) an operation classified as contaminated or dirty-infected, and (3) an operation lasting over T hours, where T depends upon the operative procedure being performed. The SWI rates for patients with scores of 0, 1, 2, and 3 were 1.5, 2.9, 6.8, and 13.0, respectively. The risk index is a significantly better predictor of SWI risk than the traditional wound classification system and performs well across a broad range of operative procedures.