Risk stratification for surgical site infections in Australia: evaluation of the US National Nosocomial Infection Surveillance risk index

This study evaluated the US National Nosocomial Infection Surveillance (NNIS) risk index (RI) in Australia for different surgical site infection (SSI) outcomes (overall, in-hospital, post-discharge, deep-incisional and superficial-incisional infection) and investigated local risk factors for SSI. A SSI surveillance dataset containing 43 611 records for 13 common surgical procedures, conducted in 23 hospitals between February 2001 and June 2005, was used for the analysis. The NNIS RI was evaluated against the observed SSI data using diagnostic test evaluation statistics (sensitivity, specificity, positive predictive value, negative predictive value). Sensitivity was low for all SSI outcomes (ranging from 0.47 to 0.69 and from 0.09 to 0.20 using RI thresholds of 1 and 2 respectively), while specificity varied depending on the RI threshold (0.55 and 0.93 with thresholds of 1 and 2 respectively). Mixed-effects logistic regression models were developed for the five SSI outcomes using a range of available potential risk factors. American Society of Anaesthesiologists (ASA) physical status score >2, duration of surgery, absence of antibiotic prophylaxis and type of surgical procedure were significant risk factors for one or more SSI outcomes, and risk factors varied for different SSI outcomes. The discriminatory ability of the NNIS RI was insufficient for its use as an accurate risk stratification tool for SSI surveillance in Australia and its sensitivity was too low for it to be appropriately used as a prognostic indicator.     

Incidence of and risk factors for surgical-site infections in a Peruvian hospital.

OBJECTIVE: To determine the incidence of and risk factors for surgical-site infections (SSIs) after abdominal surgery. DESIGN: A cohort study was conducted from January to June 1998. CDC criteria for SSI and the NNIS System risk index were used. SETTING: A tertiary-care hospital in Peru. PATIENTS: Adult patients undergoing abdominal surgery who consented were enrolled and observed until 30 days after surgery. Patients who had undergone surgery at another hospital or who died or were transferred to another hospital within 24 hours after surgery were excluded. RESULTS: Four hundred sixty-eight patients were enrolled. Their mean age was 37.2 years. One hundred twenty-five patients developed SSIs, 18% of which were identified after discharge. The overall incidence rate (IR) was 26.7%. The IR was 13.9% for clean, 15.9% for clean-contaminated, 13.5% for contaminated, and 47.2% for dirty interventions. The IR was 3.6% for NNIS System risk index 0 and 60% for index 3. Risk factors for SSI on logistic regression analysis were dirty or infected wound (RR, 3.8; CI95, 1.7-8.4), drain use longer than 9 days (RR, 6.0; CI95, 2.5-12.5), and length of surgery greater than the 75th percentile (RR, 2.1; CI95, 1.0-4.4). Patients with SSI had a longer hospital stay than did non-infected patients (14.0 vs 6.1 days; p < .001). CONCLUSIONS: SSI is a major problem in this hospital, which has a higher IR (especially for clean interventions) than those of developed countries. In developing countries, prevention of SSI should include active surveillance and interventions targeting modifiable risk factors.     

Antimicrobial proficiency testing of National Nosocomial Infections Surveillance System hospital laboratories.

OBJECTIVE: The National Nosocomial Infections Surveillance (NNIS) System personnel report trends in antimicrobial-resistant pathogens. To validate select antimicrobial susceptibility testing results and to identify test methods that tend to produce errors, we conducted proficiency testing among NNIS System hospital laboratories. SETTING: NNIS System hospital laboratories in the United States. METHODS: Each laboratory received five organisms (ie, an imipenem-resistant Serratia marcescens, an oxacillin-resistant Staphylococcus aureus, a vancomycin-resistant Enterococcus faecalis, a vancomycin-intermediate Staphylococcus epidermidis, and an extended-spectrum beta-lactamase (ESbetaL)-producing Klebsiella pneumoniae). Testing results were compared with reference testing results from the Centers for Disease Control and Prevention. RESULTS: Of 138 laboratories testing imipenem against the Serratia marcescens strain, 110 (80%) correctly reported minimum inhibitory concentrations (MICs) or zone sizes in the resistant range. All 193 participating laboratories correctly reported the Staphylococcus aureus strain as oxacillin resistant Of the 193 laboratories, 169 (88%) reported correct MICs or zone sizes for the vancomycin-resistant Enterococcus faecalis. One hundred sixty-two (84%) of 193 laboratories demonstrated the ability to detect a vancomycin-intermediate strain of Staphylococcus epidermidis, however, disk diffusion performed poorly when testing both staphylococci and enterococci with vancomycin. Although laboratory personnel correctly reported nonsusceptible extended-spectrum cephalosporins and aztreonam results for K. pneumoniae, only 98 (51%) of 193 correctly reported this organism as an ESbetaL producer. CONCLUSION: Overall, NNIS System hospital laboratory personnel detected most emerging resistance patterns. Disk diffusion continues to be unreliable for vancomycin testing of staphylococci and must be used cautiously for enterococci. Further education on the processing of ESbetaL-producing organisms is warranted.     

Risk factors for surgical site infection in a Tanzanian district hospital: a challenge for the traditional National Nosocomial Infections Surveillance system index.

The incidence of surgical site infections (SSIs) was 24% in a district hospital in Tanzania. Wound classification was not an independent risk factor for SSI, indicating that risk scores developed in industrialized countries may require adjustments for nonindustrialized countries. The National Nosocomial Infections Surveillance system score required adjustments to reliably predict SSI, probably to account for improper hygiene and the lack of adjustment for the duration of surgery (defined as the 75th percentile of the duration for each type of operative procedure) to reflect local circumstances. Multidrug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus and gram-negative pathogens expressing broad-spectrum beta-lactamases, have already emerged.     

Incidence and predictors of surgical-site infections in Vietnam.

OBJECTIVE: To determine the incidence of, and risk factors for, surgical-site infections (SSIs). DESIGN: Prospective observational study of all patients undergoing surgery during a 3-month period. SETTING: Two urban hospitals in Hanoi, Vietnam. PATIENTS: All 697 patients admitted for emergent and elective surgery. METHODS: Data were collected on all patients undergoing surgery during a 3-month period at each hospital. We stratified the data by type of surgery, wound class, and Study on the Efficacy of Nosocomial Infection Control (SENIC) risk index. The analysis was done with the data sets from each hospital separately and with the combined data. The risk factors for SSI were identified using a logistic-regression model. RESULTS: During the period of observation, 10.9% of 697 patients had SSI. The SSI rate was 8.3% for clean wounds, 8.6% for clean-contaminated, 12.2% for contaminated, and 43.9% for dirty wounds. The lowest rate of SSI (2.4%) was found in obstetric-gynecologic procedures and the highest rate (33.3%) in cardiothoracic operations. Using the SENIC risk index, the incidence of SSI in low-risk patients was 5.1%; for medium-risk patients, 13.5%, and high-risk patients, 24.2%. In a logistic-regression model, abdominal surgery (odds ratio [OR], 4.46; P<.01) and wound class IV (OR, 5.67; P<.01) were significant predictors of SSI. All patients were treated with prolonged courses of perioperative antibiotics. Overall infection control practices were poor as a result of deficient facilities, limited surgical instruments, and a lack of proper supplies for wound care and personal hygiene. CONCLUSIONS: There was a higher incidence of SSI in low-risk patients in Vietnam compared with developed countries. Excessive reliance on antimicrobial therapy as a means to limit SSI places patients at higher risk of adverse effects from treatment and also may contribute to worsening problems with antimicrobial resistance. Establishment of an infection control program with guidelines for antimicrobial use should improve the use of prophylactic antibiotics and attention to proper surgical and wound-care techniques. These interventions also should reduce the incidence of SSI and its associated morbidity and costs.     

Standardized infection ratios for three general surgery procedures: a comparison between Spanish hospitals and U.S. centers participating in the National Nosocomial Infections Surveillance System.

OBJECTIVES: To compare Spanish surgical wound infection (SWI) rates for three procedures with those published by the U.S. NNIS System, and to analyze quarterly trends. DESIGN: This was a 4-year prospective analysis of SWI using data from a Spanish nosocomial infection surveillance network based on CDC classification criteria. SWI rates were computed as standardized infection ratios (SIRs). Trends for both SWIs and SIRs were evaluated by linear regression. SETTING: Forty-three Spanish hospitals during 1997 through 2000. PATIENTS: Those undergoing cholecystectomy (n = 7,631), appendectomy (n = 5,780), and herniorrhaphy (n = 9,864). RESULTS: For cholecystectomy patients, the SWI rate was 4.38% and the SIR was 3.32. Both of these variables showed a slightly rising, although nonsignificant, linear trend during the study period. For appendectomy patients, the SWI rate was 7.94% and the SIR was 2.86. The linear trend was increasing for both, but only the SWI rate attained significance. For herniorrhaphy patients, the SWI rate was 1.77% and the SIR was 1.64. Both of these variables showed a significant descending tendency during the 4 years. CONCLUSIONS: Because the SIR takes into account the patient risk category, it is the best indicator of the trend shown by the SWI rate over time for a given surgical procedure. According to our comparison of SIRs with reference NNIS System values, SWI rates for cholecystectomy and appendectomy were high. Monitoring of the SIR will provide a basis for the design of infection control measures and the assessment of their effectiveness.     

Implementation of the Active Nosocomial Infections Surveillance System in Polish hospitals

Characteristics the organisation of infection control in hospitals participating in the Active Nosocomial Infections Surveillance System in Poland. Analysis of the data obtained from a questionnaire on organization of nosocomial infections surveillance in hospitals participating in the Active Nosocomial Infections Surveillance System coordinated by the Polish Society of Hospital Infections. Analyzed data were obtained from 32 hospitals of different size number of hospital beds) and type of reference. Most questions focused on the structures of infection control, postdischarge surveillance and role of microbiological laboratory. NIs surveillance system is based on the work of infection control team consisting of epidemiological nurse and physician representing different specializations, but there is no specialist or doctor specializing in medical microbiology. Additionally, the Infection Control Committee exists in 25 hospitals. Only in 37.5% of those hospitals the postdischarge surveillance is performed, but related only to surgical site infections. There is no microbiological surveillance in 25% of the hospitals, which means that neither registration nor collecting of drug-resistant strains are performed. Implementation of the Active Nis Surveillance System is based on the common organizational structure, programme and definitions of infections. The postdischarge surveillance and microbiological surveillance are the main activities which still need improvement.     

A survey of methods used to detect nosocomial legionellosis among participants in the National Nosocomial Infections Surveillance System.

OBJECTIVE: To help define the scope of nosocomial legionnaire's disease (LD) and to assess use of recommended diagnostic methods and transmission control practices. METHODS: We surveyed 253 hospitals participating in the National Nosocomial Infections Surveillance (NNIS) System. The anonymous survey included questions about episodes of nosocomial LD, environmental sampling practices, maintenance of hospital water systems, and diagnostic techniques. RESULTS: Of 192 hospitals that responded, 29% reported at least one episode of nosocomial LD from 1990 through 1996, and 61% of these reported at least two episodes. Of 79 hospitals with transplant programs, 42% reported nosocomial LD, compared with 20% of hospitals without transplant programs. Environmental sampling had been conducted by 55% of hospitals, including 79% of those reporting nosocomial LD. Legionella were isolated in 34% that sampled potable water and 19% that sampled cooling system reservoirs. Supplemental potable-water decontamination systems were installed in 20% of hospitals. Only 19% routinely performed testing for legionellosis among patients at high risk for nosocomial LD. CONCLUSIONS: Nosocomial LD is relatively common among NNIS hospitals, especially those performing organ transplants. Environmental sampling for Legionella is a common practice among NNIS hospitals, and Legionella often are isolated from sampled hospital cooling towers and hospital potable-water systems. Hospitals have responded to suspected nosocomial LD infection with a variety of water sampling and control strategies; some have not attempted to sample or decontaminate water systems despite identified transmission.     

A user evaluation of the Nosocomial Infection National Surveillance System: surgical site infection module

The Nosocomial Infection National Surveillance Scheme (NINSS) enables hospitals in England to undertake surveillance of healthcare associated infection, compare their results with national aggregated data, and use the information to improve patient care. A surgical site infection (SSI) module was introduced in 1997, and participation has increased steadily since its inception. This survey was undertaken to assess the views of users on the current service, and how the module should be developed to best meet their needs and resources. Survey forms were sent to infection control teams (ICTs) at the 113 hospitals that had participated at any time during the first three years of the programme. The response rate was 90% (102). The views of users were generally very positive and indicated considerable support for the approach to this type of surveillance. The ability to compare hospital infection rates with national data, the availability of standardized surveillance methods, and centralized data analysis and report production were key reasons for participation for over 80% of users. Most did not wish to see any major changes made to the protocol, although more than a third of users suggested additional data items. Overall, users were satisfied with both the content and timescale for receipt of feedback reports, and 77% disseminated them to at least three groups of clinicians and managers. The majority of ICTs (89%) gave the results directly to the surgeons. For some users (29%) it was too early to assess the value of the surveillance. Of the remainder, although results provided evidence of good performance for some, 46% identified high rates of SSI in one or more groups of surgical patients. In about two-thirds of these hospitals, a review or change in clinical practice was initiated as a result. Three main areas for development were identified: an extended range of surgical procedures, post-discharge surveillance and improved local data collection and analysis systems. Users said they would also like training in handling and interpreting surveillance data. These needs should be addressed in order to ensure the continuing success of national surveillance.     

Active surveillance of nosocomial infections in heart surgery patients: implementation of the American National Nosocomial Infections Surveillance (NNIS) System in a large hospital in Rome

The authors present the implementation of the American NNIS System method for active surveillance in the heart surgery and its intensive care unit (ICU) of a large hospital in Rome (almost 1.000 beds). This surveillance was based on full time infection control professionals. Device-associated infection rates were calculated for adult ICU surveillance component. For surgical patient surveillance component we used the surgical site infection (SSI) risk index based on wound class, duration of operation and American Society of Anesthesiology score. The NNIS System method allowed us to understand the most relevant problems in heart surgery patients: in comparison with NNIS data, we found high rates of SSIs both in procedures on valves and in coronary artery bypass grafts. The central line-associated bloodstream infection rate was higher than the American median rate. Therefore, we decided to focus on surgical risk factors linked to SSIs and to revise recommendations for intravascular-device use. In conclusion, in our experience the NNIS System method proved to be a very useful and versatile tool for nosocomial infections active surveillance.     

Nosocomial infections in geriatric long-term-care and rehabilitation facilities: exploration in the development of a risk index for epidemiological surveillance.

OBJECTIVE: To compute a risk index for nosocomial infection (NI) surveillance in geriatric long-term-care facilities (LTCFs) and rehabilitation facilities. DESIGN: Analysis of data collected during the French national prevalence survey on NIs conducted in 1996. Risk indices were constructed based on the patient case-mix defined according to risk factors for NIs identified in the elderly. SETTING: 248 geriatric units in 77 hospitals located in northern France. PARTICIPANTS: All hospital inpatients on the day of the survey were included. RESULTS: Data from 11,254 patients were recorded. The overall rate of infected patients was 9.9%. Urinary tract, respiratory tract, and skin were the most common infection sites in both rehabilitation facilities and LTCFs. Eleven risk indices, categorizing patients in 3 to 7 levels of increasing NI risk, ranging from 2.7% to 36.2%, were obtained. Indices offered risk adjustment according to NI rate stratification and clinical relevance of risk factors such as indwelling devices, open bedsores, swallowing disorders, sphincter incontinence, lack of mobility, immunodeficiency, or rehabilitation activity. CONCLUSION: The optimal index should be tailored to the strategy selected for NI surveillance in geriatric facilities in view of available financial and human resources.     

全国医院感染监控网1998～1999年监测资料分析

目的 总结和分析全国感染监控网医院感染发病率及病原菌分布。方法 对监控网医院１９９８年６月～１９９９年５月逐月上报资料进行统计分析。结果 １年共监测患者１２５３６７１人,发生医院感染４９１０９人共５１８２０例次,医院感染发病率为３．９２％,医院感染例次感染率４．１３％;感染部位以下呼吸道感染最多见,次为胃肠道、术后伤口、泌尿道感染;共分离病原体１２２６５株,以大肠埃希菌、铜绿单胞菌、金黄色葡萄球菌、表皮葡萄球菌、肠杆菌属细菌、白色念珠菌、克雷伯菌属细菌多见。结论 监控网医院感染发病率为３．９２％,以下呼吸道感染最常见,病原菌以大肠埃希菌、铜绿假单胞菌、金黄色葡萄球菌多见。     

骨科手术切口感染发生率及相关危险因素回顾性调查分析

目的 了解医院2007年1月-2011年12月骨科手术切口感染相关危险因素,为减少术后切口感染提供依据.方法 回顾性分析患者临床资料及同期医院感染报表.结果共有骨科手术患者5429例,术后切口感染发生166例,感染率为3.06％,其中骨折内固定术后感染率为2.67％、骨折内固定物取出术后感染率为1.83％、关节置换术后感染率为4.12％、截肢术后感染率为19.20％、囊肿摘除术后感染率为2.27％、其他骨科手术后感染率为3.21％;2007-2011年度骨科术后切口感染率分别为4.03％、3.79％、3.15％、2.58％、2.01％,呈现逐年下降趋势;患者年龄、低蛋白血症、中重度贫血、急诊手术、切口长度、手术时间、手术部位、切口类型、术前住院时间是影响患者术后切口感染的危险因素(P＜0.05).结论引起骨科术后切口感染的危险因素较多,医院骨科术后切口感染发生率虽呈现逐年下降趋势,但仍然要根据引起切口感染的相关危险因素进行积极干预,以期进一步控制切口感染的发生.     

综合医院ICU中心静脉导管相关性血流感染发生率及危险因素

目的了解ICU中心静脉导管相关性血流感染(CRBSI)的发病率及危险因素,为制定预防控制措施提供依据。方法采用前瞻性调查方法对江苏省19所三级综合医院ICU中心静脉置管的患者进行监测,并对置管后的维护进行全过程管理;通过logistic回归分析模型,对CRBSI的相关因素进行分析。结果 CRBSI的发病密度为3.82/1000导管日,调查时间段中后三个季度CRBSI的发生率分别为2.55%、3.30%和2.99%,明显低于监测开始的4.73%,综合ICU CRBSI的发生率为3.50%,高于专科ICU的1.74%,导管留置天数和置管地点是CRBSI的独立危险因素。结论开展ICU医院感染目标性监测有助于降低CRBSI发病率,注重中心静脉导管置管后的维护和操作时的最大无菌屏障是降低CRBSI发生率的重要措施,缩短中心静脉导管留置时间可以减少CRBSI的概率。     

Prospective pilot study on the incidence of infections caused by peripheral venous catheters at a general surgical ward

Device-associated infections comprise a significant proportion of all nosocomial infections. In this prospective, observational pilot study the incidence of infections in 89 peripheral venous catheters (PVCs) was documented on a general surgical ward employing an infection data sheet developed by the Institute of Hygiene and Environmental Medicine, Greifswald in adherence to CDC standards for infections. 16 of 20 infections were documented during a four-week time period when medical students in the first four months of their practical year performed their compulsory rotation on the general surgical ward. Insufficient knowledge of adequate hygienic measures as well as non-compliance to aseptical procedural measures prior to and following insertion of a peripheral venous catheter are the assumed instigators of these infections. In order to ensure a uniform hygienic standard in the performance of applied procedures, it is essential that medical students during this practical year receive not only theoretical, but also hands-on schooling prior to initiation of their subsequent official residency.     

Suitability of the NNIS index for estimating surgical-site infection risk at a small university hospital in Brazil.

OBJECTIVES: To detect the occurrence of surgical-site infection (SSI) in our study sample, using the traditional variables of the National Nosocomial Infection Surveillance (NNIS) index with a locally modified cut-off point for the "T time" defining length of surgical procedure; to compare the modified and the traditional NNIS index under the hypothesis that a cut-off point discriminating procedures of short and long duration, based upon the actual experience of the study sample, can adequately predict the risk of SSI. DESIGN: A retrospective chart review of 9,322 patients undergoing surgical procedures in the period January 1993 to December 1998. SETING: A small university hospital (UH) in southern Brazil. RESULTS: The composite index using the local sample procedure-duration cut-off point (UH-index) performed better than any of the individual components of the composite index (anesthesia risk index and surgical-wound class [SWC]). The UH-index also predicted adequately the risk of SSI when compared to the traditional NNIS index, particularly when stratifying by SWC. CONCLUSIONS: A modified NNIS index, using the sample cut-off point, can adequately predict the risk of SSI in a given population. Further studies are needed to compare and validate the NNIS index of risk for populations other than those of the NNIS-participating hospitals. Larger samples using different hospitals with similar characteristics are needed to investigate the risk of SSI associated with specific operations.     

Incidence of surgical site infections and accompanying risk factors in Vietnamese orthopaedic patients

A cohort study of surgical site infections (SSIs) was conducted in 582 orthopaedic surgical patients at Cho Ray Hospital, a reference hospital in Ho Chi Minh City, Vietnam, in order to determine the incidence and analyse risk factors for SSIs in this population. The SSI incidence rate was 12.5% (73 of 582); 3.6% incisional SSIs, 6.8% deep incisional SSIs and 2.1% organ/space SSIs. The incidence increased from 2% in clean wounds to 44.6% in dirty wounds, or 1.3% in patients with a National Nosocomial Infections Surveillance (NNIS) risk index of 0 to 75% in patients with an NNIS risk ratio of 3. In multi-variate analysis, having a dirty wound [odds ratio (OR) 8.7; 95% confidence intervals (CI) 4.6--16.4], American Society of Anesthesiologists' score >2 (OR 3.9; 95%CI 1.8-8.8), procedures with external fixation (OR 2.9; 95%CI 1.4-5.9), emergency surgery with motor-vehicle-related trauma (OR 2.1; 95%CI 1.2-3.9), or duration of procedure >2h (OR 2.1; 95%CI 1.1-4.2) were independent risk factors for SSI. Lack of appropriate prophylaxis was of borderline significance (OR 3.2; 95%CI 0.9-11.1, P=0.06). Among 76 patients with SSIs, 22 patients were discovered during postdischarge follow-up. These late SSIs had age as an additional risk factor (OR 2.8; 95%CI 1.1-7.2). Our data show that SSIs were frequent and differed widely by wound class. The NNIS risk index was predictive of SSI for this population. With a high number of motor vehicle accidents in Vietnam, the majority of orthopaedic operations are trauma related. Emergency surgery for injuries sustained in these accidents, and procedures with external fixation were especially prone to infections.