To investigate the effect of preoperative initiation of low molecular weight heparin as prophylaxis for deep venous thrombosis in patients at risk of developing surgical-site infections after knee arthroplasty.

Case–control study nested in a cohort. The incidence of surgical-site infection in the cohort was calculated. With the use of data extracted from medical histories and after adjustment for other risk factors, the effect of preoperative heparinization on the risk of incisional and prosthetic infection among case-patients and control-patients (1:3 ratio) was assessed.

Orthopedic department in a tertiary-care referral hospital.

A cohort of 160 consecutive patients who had received prosthetic knee implants between October 1, 2001, and November 30, 2003.

Eighteen patients with surgical-site infections were identified, yielding an incidence of incisional and prosthetic infection of 6.9 (95% confidence interval [CI95], 3.5 to 12.0) and 4.4 (CI95,1.8 to 8.8) cases per 100 patients undergoing surgery, respectively. Surgical-site infection was associated with preoperative use of low molecular weight heparin (odds ratio [OR], 6.2 after adjustment for medical and surgical factors; CI95, 1.5 to 23). Prosthetic infection was strongly associated with preoperative use of prophylaxis (OR, undetermined [100% exposure in case-patients vs 35% exposure in control-patients]; P = .002), but incisional surgical-site infection was not.

The use of low molecular weight heparins immediately before knee arthroplasty as prophylaxis for deep venous thrombosis should be questioned because of probable increased risk of prosthetic infection.

To determine whether hepatitis B virus (HBV) transmission occurred among patients visiting a physician's office and to evaluate potential transmission mechanisms.

Serologic survey, retrospective cohort study, and observation of infection control practices.

Private medical office.

Those visiting the office between March 1 and December 26, 2001.

We identified 38 patients with acute HBV infection occurring between February 2000 and February 2002. The cohort study, limited to the 10 months before outbreak detection, included 91 patients with serologic test results and available charts representing 18 case-patients and 73 susceptible patients. Overall, 67 patients (74%) received at least one injection during the observation period. Case-patients received a median of 14 injections (range, 2-25) versus 2 injections (range, 0-17) for susceptible patients (P < .001). Acute infections occurred among 18 (27%) of 67 who received at least one injection versus none of 24 who received no injections (RR, 13.6; CI95, 2.4-undefined). Risk of infection increased 5.2-fold (CI95, 0.6-47.3) for those with 3 to 6 injections and 20.0-fold (CI95, 2.8-143.5) for those with more than 6 injections. Typically, injections consisted of doses of atropine, dexamethasone, vitamin B12, or a combination of these mixed in one syringe. HBV DNA genetic sequences of 24 patients with acute infection and 4 patients with chronic infection were identical in the 1,500-bp region examined. Medical staff were seronegative for HBV infection markers. The same surface was used for storing multidose vials, preparing injections, and dismantling used injection equipment.

Administration of unnecessary injections combined with failure to separate clean from contaminated areas and follow safe injection practices likely resulted in patient-to-patient HBV transmission in a private physician's office.

To evaluate the attitudes of pediatric healthcare workers (HCWs) toward influenza vaccination and to increase their rate of immunization.

A survey was conducted among pediatric HCWs using an anonymous questionnaire. Survey results were used to design an intervention to increase the immunization rate of staff. Immunization rates before (2003-2004) and after (2004-2005) intervention were assessed using immunization clinic records.

A university children's hospital in Switzerland.

(1) An informational letter based on misconceptions noted in the survey, (2) educational conversations with head nurses, (3) more “walk-in” immunization clinics, and (4) a direct offer of influenza immunization on the wards.

Among vaccine nonrecipients, doubts about the efficacy and necessity of influenza immunization were prevalent and more often reported by nurses than physicians (75% vs 41%, P = .002; and 55% vs 23%, P = .001, respectively). Physicians more often than nurses reported lack of time as a reason for not receiving influenza vaccination (23% vs 5%, P = .01). After intervention, the immunization rate of HCWs increased from 19% to 24% (P = .03). The immunization rate of physicians increased from 43% to 64% (P = .004). No change was noted among nurses (13% vs 14%) and other HCWs (16% vs 16%).

Misconceptions about influenza vaccination were prevalent among pediatric staff, particularly nurses. Active promotion and educational efforts were successful in increasing the immunization rate of physicians but not nurses and other HCWs.

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistant Staphylococcus aureus (MRSA) transmission among hospitalized patients.

General medical ward.

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)

We describe an effort to reduce transmission of a multidrug-resistant Streptococcus pneumoniae (MDRSP) in a long-term-care facility (LTCF).

Longitudinal cross-sectional study.

An LTCF in New York City with ongoing disease due to an MDRSP strain among residents with AIDS since a 1995 outbreak. The MDRSP outbreak strain was susceptible to vancomycin but not to other antimicrobials tested, including fluoroquinolones.

Residents and staff members of the LTCF during 1999 through 2001.

Implementing standard infection control measures, and developing and implementing "enhanced standard" infection control measures, modified respiratory droplet prevention measures to reduce inter-resident transmission.

Before the intervention, nasopharyngeal carriage of the MDRSP outbreak strain was detected in residents with AIDS and residents with tracheostomies who were not dependent on mechanical ventilation. The prevalence of nasopharyngeal carriage of the MDRSP outbreak strain was 7.8% among residents who had AIDS and 14.6% among residents with tracheostomies. After training sessions on standard and enhanced standard infection control measures, the staff appeared to have good knowledge and practice of the infection control measures. After the intervention, new transmission among residents with tracheostomies was prevented; however, these residents were prone to persistent tracheal carriage and needed ongoing enhanced standard infection control measures. Ongoing transmission among residents with AIDS, a socially active group, was documented, although fewer cases of disease due to the outbreak strain occurred.

Infection control contributed to less transmission of MDRSP in the LTCF. Additional strategies are needed to reduce transmission and carriage among certain resident populations.

The role of environmental surface contamination in the propagation of norovirus outbreaks is unclear. An outbreak of acute gastroenteritis was reported among residents of a 240-bed veterans long-term-care facility.

To identify the likely mode of transmission, to characterize risk factors for illness, and to evaluate for environmental contamination in this norovirus outbreak.

An outbreak investigation was conducted to identify risk factors for illness among residents and employees. Stool and vomitus samples were tested for norovirus by reverse transcription polymerase chain reaction (RT-PCR). Fourteen days after outbreak detection, ongoing cases among the residents prompted environmental surface testing for norovirus by RT-PCR.

One hundred twenty-seven (52%) of 246 residents and 84 (46%) of 181 surveyed employees had gastroenteritis. Case-residents did not differ from non-case-residents by comorbidities, diet, room type, or level of mobility. Index cases were among the nursing staff. Eight of 11 resident stool or vomitus samples tested positive for genogroup II norovirus. The all-cause mortality rate during the month of the outbreak peak was significantly higher than the expected rate. Environmental surface swabs from case-resident rooms, a dining room table, and an elevator button used only by employees were positive for norovirus. Environmental and clinical norovirus sequences were identical.

Extensive contamination of environmental surfaces may play a role in prolonged norovirus outbreaks and should be addressed in control interventions.

Clostridium difficile-associated diarrhea (CDAD) causes substantial healthcare-associated morbidity. Unlike other common healthcare-associated pathogens, little comparative information is available about CDAD rates in hospitalized patients.

To determine CDAD rates per 10,000 patient-days and per 1,000 hospital admissions at 7 geographically diverse tertiary-care centers from 2000 to 2003, and to survey participating centers on methods of CDAD surveillance and case definition.

Each center provided specific information for the study period, including case numbers, patient-days, and hospital characteristics. Case definitions and laboratory diagnoses of healthcare-associated CDAD were determined by each institution. Within institutions, case definitions remained consistent during the study period.

Overall, mean annual case rates of CDAD were 12.1 per 10,000 patient-days (range, 3.1 to 25.1) and 7.4 per 1,000 hospital admissions (range, 3.1 to 13.1). No significant increases were observed in CDAD case rates during the 4-year interval, either at individual centers or in the Prevention Epicenter hospitals as a whole. Prevention Epicenter hospitals differed in their CDAD case definitions. Different case definitions used by the hospitals applied to a fixed data set resulted in a 30% difference in rates. No associations were identified between diagnostic test or case definition used and the relative rate of CDAD at a specific medical center.

Rates of CDAD vary widely at tertiary-care centers across the United States. No significant increases in case rates were identified. The varying clinical and laboratory approaches to diagnosis complicated comparisons between hospitals. To facilitate benchmarking and comparisons between institutions, we recommend development of a more standardized case definition.

To describe the use of laminar airflow, body exhaust, and ultraviolet lights during total knee replacement (TKR) in four U.S. states.

Survey of healthcare facilities.

Hospitals in Illinois, North Carolina, Ohio, and Tennessee that performed TKR during 2000 as identified by Medicare claims data.

Hospitals responding to a mailed questionnaire.

Two hundred ninety-five (73%) of 405 eligible hospitals that performed 18,374 primary and revision TKR procedures responded to the questionnaire. Among responding hospitals, 30% reported regular use (for > 75% of procedures) of laminar airflow, 42% reported regular use of body exhaust, and 5% reported regular use of ultraviolet lights. Among hospitals providing complete data, 150 (58%) performing 66% of procedures reported regular use of at least one of these techniques. On regression analyses, laminar airflow was used more often by hospitals with a TKR volume greater than 25 procedures per year (odds ratio [OR], 2.0; 95% confidence interval [CI95], 1.1-3.7) and orthopedic residency programs (OR, 2.8; CI95,1.3-6.3), but its use was not significantly related to hospital setting or ownership status.

Although these clean air practices are not recommended by any U.S. governmental or professional organization, they are used in nearly two-thirds of TKR procedures. Better information about their impact on current practice and more explicit guidelines may aid decisions about the use of these resource-intensive infection control practices.

To identify modes of HCV transmission during an outbreak of HCV infection in a hemodialysis unit.

An epidemiologic study, virologie analysis, assessment of infection control practices and procedures, and technical examination of products and dialysis machines.

A private hemodialysis unit treating approximately 70 patients.

Detection of HCV RNA by PCR was performed among patients receiving dialysis in 2001. Case-patients were patients who had a first positive result for HCV RNA between January 2001 and January 2002 and either acute hepatitis, a seroconversion for HCV antibodies, or a previous negative result. Three control-patients were randomly selected per case-patient.

Of the 61 patients treated in the unit in 2001 and not infected with HCV, 22 (36.1%) became case-patients with onset from May 2001 to January 2002 for an incidence density rate of 70 per 100 patient-years. Phylogenic analysis identified four distinct HCV groups and an index case-patient for each with a similar virus among patients already known to be infected. No multidose medication vials or material was shared between patients. Connection to a dialysis machine by a nurse who had connected an HCV-infected patient “just before” or “one patient before” increased the risk of HCV infection, whereas using the same dialysis machine after a patient infected with HCV did not. Understating, lack of training, and breaches in infection control were documented. Direct observation of practices revealed frequent flooding of blood into the double filter on the arterial pressure tubing set.

During this outbreak, HCV transmission was mainly patient to patient via healthcare workers' hands. However, transmission via dialysis machines because of possible contamination of internal components could not be excluded.

Despite contact isolation precautions for patients with methicillin-resistant Staphylococcus aureus (MRSA), MRSA infections are increasing in many countries.

To evaluate the role of a potential unrecognized reservoir of MRSA carried by patients in acute care wards, we determined the prevalence of MRSA at hospital admission, with special emphasis on screening-specimen yields.

A 1,100-bed teaching hospital in Paris, France.

Nasal screening cultures were performed at admission to a tertiary-care teaching hospital for patients older than 75 years.

MRSA was isolated from 63 (7.9%) of 797 patients. On the multivariate analysis, variables significantly associated with MRSA carriage were presence of chronic skin lesions (adjusted odds ratio [AOR], 5.10; 95% confidence interval [CI95], 2.52–10.33); transfer from a nursing home, rehabilitation unit, or long-term-care unit (AOR, 4.52; CI95, 2.23–9.18); and poor chronic health status (AOR, 1.80; CI95, 1.02–3.18). Without admission screening, 84.1% of MRSA carriers would have been missed at hospital admission and 76.2% during their hospital stay. Furthermore, 81.1% of days at risk for MRSA dissemination would have been spent without contact isolation precautions had admission screening not been performed.

MRSA carriage at hospital admission is far more prevalent than MRSA-positive clinical specimens. This may contribute to failure of contact isolation programs. Screening cultures at admission help to identify the reservoir of unknown MRSA patients.

To describe an outbreak of hospital-acquired MRSA in a NICU and to identify the risk factors for, outcomes of, and interventions that eliminated it.

An 18-bed, level III-IV NICU in a community hospital.

Interventions to control MRSA included active surveillance, aggressive contact isolation, and cohorting and decolonization of infants and HCWs with MRSA. A case–control study was performed to compare infants with and without MRSA.

A cluster of 6 cases of MRSA infection between September and October 2001 represented an increased attack rate of 21.2% compared with 5.3% in the previous months. Active surveillance identified unsuspected MRSA colonization in 6 (21.4%) of 28 patients and 6 (5.5%) of 110 HCWs screened. They were all successfully decolonized. There was an increased risk of MRSA colonization and infection among infants with low birth weight or younger gestational age. Multiple gestation was associated with an increased risk of colonization (OR, 37.5; CI95, 3.9–363.1) and infection (OR, 5.36; CI95, 1.37–20.96). Gavage feeding (OR, 10.33; CI95, 1.28–83.37) and intubation (OR, 5.97; CI95, 1.22–29.31) were associated with increased risk of infection. Infants with MRSA infection had a significantly longer hospital stay than infants without MRSA (51.83 vs 21.46 days; P = .003). Rep-PCR with mec typing and PVL analysis confirmed the presence of a single common strain of hospital-acquired MRSA.

Active surveillance, aggressive implementation of contact isolation, cohorting, and decolonization effectively eradicated MRSA from the NICU for 2½ years following the outbreak. (Infect Control Hosp Epidemiol 2005;26:616-621)

To describe an outbreak of hepatitis C virus (HCV).

Retrospective cohort study.

Outpatient department of a hospital in Rome, Italy.

All 42 patients exposed to ozone therapy by autohemotherapy or intramuscular injection from January to June 2001.

Epidemiologic investigation, serologic analysis, and virus genotyping.

Thirty-one (74%) of the patients agreed to participate in the study. Three (9.7%) had symptoms of HCV infection. This incidence rate was higher than the rate of 1.4 per 100,000 per year in the regional population. Six patients were positive for HCV antibodies and HCV RNA for a prevalence rate of 19.4%, which was much higher than the estimate of 0.9% in the population. Virus genotype lb was found in two case-patients (one symptomatic) and 2c in four case-patients (two symptomatic), one of whom was known to have an HCV infection since 1986 and could have been the source of infection. The infected patients were all being exposed to ozone-enriched transfusions of autologous blood. Although the specific mode of transmission between patients was not detected, transmission probably occurred during one of the three busiest therapeutic sessions in the 6-month period.

Transmission of HCV infection may occur during medical procedures with limited bleeding. Standard precautions must be applied in any healthcare setting; restricting the number of individuals treated during each therapeutic session could be an effective way of avoiding accidental transmission of infection.