Hospital outcomes of community-acquired COVID-19 versus influenza: Insights from the Swiss hospital-based surveillance of influenza and COVID-19.

BackgroundSince the onset of the COVID-19 pandemic, the disease has frequently been compared with seasonal influenza, but this comparison is based on little empirical data.AimThis study compares in-hospital outcomes for patients with community-acquired COVID-19 and patients with community-acquired influenza in Switzerland.MethodsThis retrospective multi-centre cohort study includes patients > 18 years admitted for COVID-19 or influenza A/B infection determined by RT-PCR. Primary and secondary outcomes were in-hospital mortality and intensive care unit (ICU) admission for patients with COVID-19 or influenza. We used Cox regression (cause-specific and Fine-Gray subdistribution hazard models) to account for time-dependency and competing events with inverse probability weighting to adjust for confounders.ResultsIn 2020, 2,843 patients with COVID-19 from 14 centres were included. Between 2018 and 2020, 1,381 patients with influenza from seven centres were included; 1,722 (61%) of the patients with COVID-19 and 666 (48%) of the patients with influenza were male (p < 0.001). The patients with COVID-19 were younger (median 67 years; interquartile range (IQR): 54-78) than the patients with influenza (median 74 years; IQR: 61-84) (p < 0.001). A larger percentage of patients with COVID-19 (12.8%) than patients with influenza (4.4%) died in hospital (p < 0.001). The final adjusted subdistribution hazard ratio for mortality was 3.01 (95% CI: 2.22-4.09; p < 0.001) for COVID-19 compared with influenza and 2.44 (95% CI: 2.00-3.00, p < 0.001) for ICU admission.ConclusionCommunity-acquired COVID-19 was associated with worse outcomes compared with community-acquired influenza, as the hazards of ICU admission and in-hospital death were about two-fold to three-fold higher.

Evolution of COVID-19 mortality over time: results from the Swiss hospital surveillance system (CH-SUR).

BACKGROUND: When the periods of time during and after the first wave of the ongoing SARS-CoV-2/COVID-19 pandemic in Europe are compared, the associated COVID-19 mortality seems to have decreased substantially. Various factors could explain this trend, including changes in demographic characteristics of infected persons and the improvement of case management. To date, no study has been performed to investigate the evolution of COVID-19 in-hospital mortality in Switzerland, while also accounting for risk factors. METHODS: We investigated the trends in COVID-19-related mortality (in-hospital and in-intermediate/intensive-care) over time in Switzerland, from February 2020 to June 2021, comparing in particular the first and the second wave. We used data from the COVID-19 Hospital-based Surveillance (CH-SUR) database. We performed survival analyses adjusting for well-known risk factors of COVID-19 mortality (age, sex and comorbidities) and accounting for competing risk. RESULTS: Our analysis included 16,984 patients recorded in CH-SUR, with 2201 reported deaths due to COVID-19 (13.0%). We found that overall in-hospital mortality was lower during the second wave of COVID-19 than in the first wave (hazard ratio [HR] 0.70, 95% confidence interval [CI] 0.63- 0.78; p <0.001), a decrease apparently not explained by changes in demographic characteristics of patients. In contrast, mortality in intermediate and intensive care significantly increased in the second wave compared with the first wave (HR 1.25, 95% CI 1.05-1.49; p = 0.029), with significant changes in the course of hospitalisation between the first and the second wave. CONCLUSION: We found that, in Switzerland, COVID-19 mortality decreased among hospitalised persons, whereas it increased among patients admitted to intermediate or intensive care, when comparing the second wave to the first wave. We put our findings in perspective with changes over time in case management, treatment strategy, hospital burden and non-pharmaceutical interventions. Further analyses of the potential effect of virus variants and of vaccination on mortality would be crucial to have a complete overview of COVID-19 mortality trends throughout the different phases of the pandemic.

Risk factors for severe outcomes for COVID-19 patients hospitalised in Switzerland during the first pandemic wave, February to August 2020: prospective observational cohort study.

BACKGROUND: As clinical signs of COVID-19 differ widely among individuals, from mild to severe, the definition of risk groups has important consequences for recommendations to the public, control measures and patient management, and needs to be reviewed regularly. AIM: The aim of this study was to explore risk factors for in-hospital mortality and intensive care unit (ICU) admission for hospitalised COVID-19 patients during the first epidemic wave in Switzerland, as an example of a country that coped well during the first wave of the pandemic. METHODS: This study included all (n = 3590) adult polymerase chain reaction (PCR)-confirmed hospitalised patients in 17 hospitals from the hospital-based surveillance of COVID-19 (CH-Sur) by 1 September 2020. We calculated univariable and multivariable (adjusted) (1) proportional hazards (Fine and Gray) survival regression models and (2) logistic regression models for in-hospital mortality and admission to ICU, to evaluate the most common comorbidities as potential risk factors. RESULTS AND DISCUSSION: We found that old age was the strongest factor for in-hospital mortality after having adjusted for gender and the considered comorbidities (hazard ratio [HR] 2.46, 95% confidence interval [CI] 2.33−2.59 and HR 5.6 95% CI 5.23−6 for ages 65 and 80 years, respectively). In addition, male gender remained an important risk factor in the multivariable models (HR 1.47, 95% CI 1.41−1.53). Of all comorbidities, renal disease, oncological pathologies, chronic respiratory disease, cardiovascular disease (but not hypertension) and dementia were also risk factors for in-hospital mortality. With respect to ICU admission risk, the pattern was different, as patients with higher chances of survival might have been admitted more often to ICU. Male gender (OR 1.91, 95% CI 1.58−2.31), hypertension (OR  1.3, 95% CI 1.07−1.59) and age 55–79 years (OR 1.15, 95% CI 1.06−1.26) are risk factors for ICU admission. Patients aged 80+ years, as well as patients with dementia or with liver disease were admitted less often to ICU. CONCLUSION: We conclude that increasing age is the most important risk factor for in-hospital mortality of hospitalised COVID-19 patients in Switzerland, along with male gender and followed by the presence of comorbidities such as renal diseases, chronic respiratory or cardiovascular disease, oncological malignancies and dementia. Male gender, hypertension and age between 55 and 79 years are, however, risk factors for ICU admission. Mortality and ICU admission need to be considered as separate outcomes when investigating risk factors for pandemic control measures and for hospital resources planning.

Cohort profile: SARS-CoV-2/COVID-19 hospitalised patients in Switzerland.

BACKGROUND: SARS-CoV-2/COVID-19, which emerged in China in late 2019, rapidly spread across the world with several million victims in 213 countries. Switzerland was severely hit by the virus, with 43,000 confirmed cases as of 1 September 2020. AIM: In cooperation with the Federal Office of Public Health, we set up a surveillance database in February 2020 to monitor hospitalised patients with COVID-19, in addition to their mandatory reporting system. METHODS: Patients hospitalised for more than 24 hours with a positive polymerase chain-reaction test, from 20 Swiss hospitals, are included. Data were collected in a customised case report form based on World Health Organisation recommendations and adapted to local needs. Nosocomial infections were defined as infections for which the onset of symptoms was more than 5 days after the patient’s admission date. RESULTS: As of 1 September 2020, 3645 patients were included. Most patients were male (2168, 59.5%), and aged between 50 and 89 years (2778, 76.2%), with a median age of 68 (interquartile range 54–79). Community infections dominated with 3249 (89.0%) reports. Comorbidities were frequently reported, with hypertension (1481, 61.7%), cardiovascular diseases (948, 39.5%) and diabetes (660, 27.5%) being the most frequent in adults; respiratory diseases and asthma (4, 21.1%), haematological and oncological diseases (3, 15.8%) were the most frequent in children. Complications occurred in 2679 (73.4%) episodes, mostly respiratory diseases (2470, 93.2% in adults; 16, 55.2% in children), and renal (681, 25.7%) and cardiac (631, 23.8%) complications for adults. The second and third most frequent complications in children affected the digestive system and the liver (7, 24.1%). A targeted treatment was given in 1299 (35.6%) episodes, mostly with hydroxychloroquine (989, 76.1%). Intensive care units stays were reported in 578 (15.8%) episodes. A total of 527 (14.5%) deaths were registered, all among adults. CONCLUSION: The surveillance system has been successfully initiated and provides a robust set of data for Switzerland by including about 80% (compared with official statistics) of SARS-CoV-2/COVID-19 hospitalised patients, with similar age and comorbidity distributions. It adds detailed information on the epidemiology, risk factors and clinical course of these cases and, therefore, is a valuable addition to the existing mandatory reporting.

Diabetes mellitus is a risk factor for prolonged SARS-CoV-2 viral shedding in lower respiratory tract samples of critically ill patients.

PURPOSE: The length of time a critically ill coronavirus disease 2019 (COVID-19) patient remains infectious and should therefore be isolated remains unknown. This prospective study was undertaken in critically ill patients to evaluate the reliability of single negative real-time polymerase chain reaction (RT-PCR) in lower tracheal aspirates (LTA) in predicting a second negative test and to analyze clinical factors potentially influencing the viral shedding. METHODS: From April 9, 2020 onwards, intubated COVID-19 patients treated in the intensive care unit were systematically evaluated for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by RT-PCR of nasopharyngeal swabs and LTA. The time to negativity was defined as the time between the onset of symptoms and the viral clearance in LTA. In order to identify risk factors for prolonged viral shedding, we used univariate and multivariate Cox proportional hazards models. RESULTS: Forty-eight intubated SARS-CoV-2 patients were enrolled. Overall, we observed that the association of the first negative RT-PCR with a second negative result was 96.7%. Median viral shedding was 25 (IQR: 21.5-28) days since symptoms' onset. In the univariate Cox model analysis, type 2 diabetes mellitus was associated with a prolonged viral RNA shedding (hazard ratio [HR]: 0.41, 95% CI: 0.06-3.11, p = 0.04). In the multivariate Cox model analysis, type 2 diabetes was associated with a prolonged viral RNA shedding (HR: 0.31, 95% CI: 0.11-0.89, p = 0.029). CONCLUSION: Intubated patients with type 2 diabetes mellitus may have prolonged SARS-CoV-2 shedding. In critically ill COVID-19 patients, one negative LTA should be sufficient to assess and exclude infectivity.

Factors determining the adherence to antimicrobial guidelines and the adoption of computerised decision support systems by physicians: A qualitative study in three European hospitals.

BACKGROUND AND OBJECTIVES: Antimicrobial stewardship (AMS) programs aim to optimize antibiotic use and reduce inappropriate prescriptions through a panel of interventions. The implementation of clinical guidelines is a core strategy of AMS programs. Nevertheless, their dissemination and application remain low. Computerised decision support systems (CDSSs) offer new opportunities for semi-automated dissemination of guidelines. This qualitative study aimed at gaining an in-depth understanding of the determinants of adherence to antimicrobial prescribing guidelines and CDSSs adoption and is part of a larger project, the COMPASS trial, which aims to assess a CDSS for antimicrobial prescription. The final objective of this qualitative study is to 1) provide insights from end-users to assist in the design of the COMPASS CDSS, and to 2) help with the interpretation of the quantitative findings of the randomised controlled trial assessing the COMPASS CDSS, once data will be analysed. METHODS: We conducted semi-structured individual interviews among in-hospital physicians in two hospitals in Switzerland and one hospital in France. Physicians were recruited by convenience sampling and snowballing until data saturation was achieved. RESULTS: Twenty-nine physicians were interviewed. We identified three themes related to the potential barriers to guideline adherence: 1) insufficient clarity, accessibility and applicability of guidelines, 2) need of critical thinking skills to adhere to guidelines and 3) impact of the team prescribing process and peers on physicians in training. As to the perception of CDSSs, we identified four themes that could affect their adoption: 1) CDSSs are perceived as time-consuming, 2) CDSSs could reduce physicians' critical thinking and professional autonomy and raise new medico-legal issues, 3) effective CDSSs would require specific features, such as ease of use and speed, which affect usability and 4) CDSSs could improve physicians' adherence to guidelines and patient care. DISCUSSION: CDSSs have the potential to overcome several barriers for adherence to guidelines by improving accessibility and providing individualised recommendations backed by patient data. When designing CDSSs, mixed clinical and information technology teams should focus on user-friendliness, ergonomics, workflow integration and transparency of the decision-making process.

Risk of SARS-CoV-2 transmission by aerosols, the rational use of masks, and protection of healthcare workers from COVID-19.

OBJECTIVES: To determine the risk of SARS-CoV-2 transmission by aerosols, to provide evidence on the rational use of masks, and to discuss additional measures important for the protection of healthcare workers from COVID-19. METHODS: Literature review and expert opinion. SHORT CONCLUSION: SARS-CoV-2, the pathogen causing COVID-19, is considered to be transmitted via droplets rather than aerosols, but droplets with strong directional airflow support may spread further than 2 m. High rates of COVID-19 infections in healthcare-workers (HCWs) have been reported from several countries. Respirators such as filtering face piece (FFP) 2 masks were designed to protect HCWs, while surgical masks were originally intended to protect patients (e.g., during surgery). Nevertheless, high quality standard surgical masks (type II/IIR according to European Norm EN 14683) appear to be as effective as FFP2 masks in preventing droplet-associated viral infections of HCWs as reported from influenza or SARS. So far, no head-to-head trials with these masks have been published for COVID-19. Neither mask type completely prevents transmission, which may be due to inappropriate handling and alternative transmission pathways. Therefore, compliance with a bundle of infection control measures including thorough hand hygiene is key. During high-risk procedures, both droplets and aerosols may be produced, reason why respirators are indicated for these interventions.

Burkholderia cepacia complex outbreak originating from contaminated wash gloves.

Burkholderia cepacia complex isolates were detected from four patients who were admitted to the heart centre of southern Switzerland, between April and June 2019. An outbreak investigation was conducted. The three available patient samples were whole genome sequenced, showing that they all are Burkholderia cepacia species, and that two are identical. Isolates grown from sealed packages of disinfectant-free wash gloves used for personal hygiene were also genomically identical. The wash gloves appear to be the origin of the outbreak, contamination of which most likely occurred at the manufacturing site.

National point prevalence survey on healthcare-associated infections in acute care hospitals, Switzerland, 2017.

BackgroundAs a part of the national strategy on the prevention of healthcare-associated infections (HAI), a point prevalence survey (PPS) was conducted in acute care hospitals in Switzerland.AimOur objective was to assess the burden of HAI in Swiss acute care hospitals.MethodsAll acute care hospitals were invited to participate in this cross-sectional survey during the second quarter of 2017. The protocol by the European Centre for Disease Prevention and Control was applied. Patients of all ages, hospitalised on the day of survey were included, except when admitted to outpatient clinics, emergency and psychiatry.ResultsNinety-six acute care hospitals (79% of all hospitals ≥ 100 beds) provided data on 12,931 patients. Pooled and randomised HAI prevalences were 5.9% (95% confidence interval (CI): 5.5-6.3) and 5.4% (95% CI: 4.8-6.0), respectively. The HAI incidence was estimated at 4.5 (95% CI: 4.0-5.0). The most common type of HAI was surgical site infection (29.0%), followed by lower respiratory tract (18.2%), urinary tract (14.9%) and bloodstream (12.8%) infections. The highest prevalence was identified in intensive care (20.6%), in large hospitals > 650 beds (7.8%), among elderly patients (7.4%), male patients (7.2%) and patients with an ultimately (9.3%) or rapidly (10.6%) fatal McCabe score.DiscussionThis is the first national PPS of Switzerland allowing direct comparison with other European countries. The HAI prevalence was at European Union average (5.9% in 2016 and 2017), but higher than in some countries neighbouring Switzerland. Based on the limited information from previous surveys, HAI appear not to decrease.

Antimicrobial use in acute care hospitals: national point prevalence survey on healthcare-associated infections and antimicrobial use, Switzerland, 2017.

BackgroundA point prevalence survey (PPS) on healthcare-associated infections (HAI) and antimicrobial use was conducted in Swiss acute care hospitals in 2017.AimOur objective was to assess antimicrobial use in Swiss acute care hospitals.MethodsAll patients hospitalised in any acute care hospital in Switzerland were eligible. We used the most recent version of the PPS protocol of the European Centre for Disease Prevention and Control.ResultsData from 12,931 patients of 96 hospitals were collected. Of these, 4,265 (33%; 95% confidence interval (CI): 32.2-33.8) were on 5,354 antimicrobials for 4,487 indications. Most of the 2,808 therapeutic indications addressed 1,886 community-acquired infections (67.2%; 95% CI: 65.4-68.9). Of the 1,176 surgical prophylaxes, 350 (29.8%; 95% CI: 27.1-32.4) exceeded the duration of 1 day. Of the 1,090 antimicrobial regimens that were changed, 309 (28.3%; 95% CI: 25.7-31.0) were escalated and 337 (30.9%; 95% CI: 28.2-33.7) were de-escalated. Amoxicillin/clavulanic acid was the most frequent antimicrobial (18.8%; 95% CI: 17.7-19.8), prescribed mainly for therapeutic indications (76.0%; 95% CI: 73.3-78.7). A total of 1,931 (37.4%; 95% CI: 36.1-38.8) of the 5,158 antimicrobials for systemic use were broad-spectrum antibiotics, most frequently third- and fourth-generation cephalosporins (35.9%; 95% CI: 33.8-38.1).ConclusionsAntimicrobial consumption was at European average, the use of broad-spectrum antibiotics in the lower third. Swiss acute care hospitals should invest in antimicrobial stewardship, particularly in reducing the use of broad-spectrum antibiotics.

Nation-wide survey of screening practices to detect carriers of multi-drug resistant organisms upon admission to Swiss healthcare institutions.

As emergence and spread of multi-drug resistant organisms (MDRO) requires a standardized preventive approach, we aimed to evaluate current MDRO admission screening practices in Swiss hospitals and to identify potential barriers impeding their implementation. In early 2018, all Swiss public and private healthcare institutions providing inpatient care were contacted with a 34-item questionnaire to investigate current MDRO admission screening policies. Among 139 respondents representing 180 institutions (response rate, 79%), 83% (149) of institutions implemented MDRO admission screening, while 28% of private and 9% of public institutions did not perform any screening. Targeted high-risk screening included carbapenemase producers, extended-spectrum beta-lactamase producers and methicillin-resistant Staphylococcus aureus at the institutional level for respectively 78% (115), 81% (118) and 98% (145) of screening institutions. Vancomycin-resistant enterococci (44% of institutions), multi-resistant Acinetobacter baumanii (41%) and Pseudomonas aeruginosa (37%) were systematically searched only by a minority of screening institutions. A large diversity of risk factors for targeted screening and some heterogeneity in body sites screened were also observed. Admission-screening practices were mostly impeded by a difficulty to identify high-risk patients (44%) and non-compliance of healthcare workers (35%). Heterogeneous practices and gaps in small and privately-owned institutions, as well as a mismatch between current epidemiologic MDRO trends and screening practices were noticed. These results highlight the need for uniform national MDRO screening standards.

Antibiotic resistance in Swiss nursing homes: analysis of National Surveillance Data over an 11-year period between 2007 and 2017.

Background: We evaluated data from isolates of nursing home (NH) patients sent to the Swiss centre for antibiotic resistance (ANRESIS). We focussed on carbapenem-resistance (CR) among Gram-negative pathogens, extended-spectrum cephalosporin-resistant (ESC-R) Escherichia coli/Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), and glycopeptide-resistant enterococci (GRE). Methods: NH patient isolates from 01/2007 to 10/2017 were extracted. Temporal trends in resistance were described and risk factors associated with ESC-R and MRSA were assessed. For every administrative subdivision in Switzerland (i.e. canton), we calculated a coverage rate, defined as number of beds of governmentally-supported nursing homes, which sent ≥1 isolate in each 2014, 2015, and 2016, divided by the total number of supported beds. Results: We identified 16'804 samples from 9'940 patients. A majority of samples (12'040; 71.6%) originated from the French/Italian speaking part of Switzerland. ESC-R E. coli increased from 5% (16/299) in 2007 to 22% (191/884) in 2017 (P < 0.01), whereas MRSA decreased from 34% (35/102) to 26% (21/81) (P < 0.01). Provenience from the German (vs. French/Italian) speaking part of Switzerland was associated with decreased risk for ESC-R (OR 0.5, 95% CI 0.4-0.7) and for MRSA (OR 0.1, 95% CI 0.1-0.2). CR among Pseudomonas aeruginosa was 10% (105/1096) and showed an increasing trend over time; CR among Enterobacteriaceae (37/12'423, 0.3%) and GRE (5/1'273, 0.4%) were uncommon. Overall coverage rate was 9% (range 0-58% per canton). There was a significant difference between the French/Italian (median 13%, interquartile range [IQR] 4-43%) and the German speaking cantons (median 0%, IQR 0-5%) (P = 0.02). Conclusions: ESC-R among E. coli is emerging in Swiss NHs, whereas MRSA show a declining trend over time. A minority of NHs are represented in ANRESIS, with a preponderance of institutions from the French/Italian speaking regions. Efforts should be undertaken to improve resistance surveillance in this high-risk setting.

Contact tracing investigation after professional exposure to tuberculosis in a Swiss hospital using both tuberculin skin test and IGRA.

SETTING: A 950 bed teaching hospital in Switzerland. AIM: To describe the result of a contact investigation among health care workers (HCW) and patients after exposure to a physician with smear-positive pulmonary tuberculosis in a hospital setting using standard tuberculin skin tests (TST) and Interferon-gamma release assay (IGRA). METHOD: HCW with a negative or unknown TST at hiring had a TST two weeks after the last contact with the index case (T0), repeated six weeks later if negative (T6). All exposed HCW had a T-SPOT.TB at T0 and T6. Exposed patients had a TST six weeks after the last contact, and a T-SPOT.TB if the TST was positive. RESULTS: Among 101 HCW, 17/73 (22%) had a positive TST at T0. TST was repeated in 50 at T6 and converted from negative to positive in eight (16%). Twelve HCW had a positive T-SPOT.TB at T0 and ten converted from negative to positive at T6. Seven HCW with a positive T-SPOT.TB reverted to negative at T6 or at later controls, most of them with test values close to the cut-off. Among 27 exposed patients tested at six weeks, ten had a positive TST, five of them confirmed by a positive T-SPOT.TB. CONCLUSIONS: HCW tested twice after exposure to a case of smear-positive pulmonary TB demonstrated a possible conversion in 10% with T-SPOT and 16% with TST. Some T-SPOT.TB reverted from positive to negative during the follow-up, mostly tests with a value close to the cut-off. Due to the variability of the test results, it seems advisable to repeat the test with values close to the cut-off before diagnosing the presence of a tuberculous infection.

High proportion of healthcare-associated urinary tract infection in the absence of prior exposure to urinary catheter: a cross-sectional study.

BACKGROUND: Exposure to urinary catheters is considered the most important risk factor for healthcare-associated urinary tract infection (UTI) and is associated with significant morbidity and substantial extra-costs. In this study, we assessed the impact of urinary catheterisation (UC) on symptomatic healthcare-associated UTI among hospitalized patients. METHODS: A nationwide period prevalence survey of healthcare-associated infections was conducted during 1 May to 30 June 2004 in 49 Swiss hospitals and included 8169 adult patients (4313 female; 52.8%) hospitalised in medical, surgical, intermediate, and intensive care wards. Additional data were collected on exposure to UC to investigate factors associated with UTI among hospitalised adult patients exposed and non-exposed to UC. RESULTS: 1917 (23.5%) patients were exposed to UC within the week prior to survey day; 126 (126/8169; 1.5%) developed UTI. Exposure to UC preceded UTI only in 73 cases (58%). By multivariate logistic regression analysis, UTI was independently associated with exposure to UC (odds ratio [OR], 3.9 [95% CI, 2.6-5.9]), female gender (OR, 2.1 [95% CI, 1.4-3.1]), an American Society of Anesthesiologists' score > 2 points (OR, 3.2 [95% CI, 1.1-9.4], and prolonged hospital stay >20 days (OR, 1.9 [95% CI, 1.4-3.2]. Further analysis showed that the only significant factor for UTI with exposure to UC use was prolonged hospital stay >40 days (OR, 2.9 [95% CI, 1.3-6.1], while female gender only showed a tendency (OR, 1.6 [95% CI, 1.0-2.7]. In the absence of exposure to UC, the only significant risk factor for UTI was female gender (OR, 3.3 [95% CI, 1.7-6.5]). CONCLUSIONS: Exposure to UC was the most important risk factor for symptomatic healthcare-associated UTI, but only concerned about half of all patients with UTI. Further investigation is warranted to improve overall infection control strategies for UTI.

Overall burden of healthcare-associated infections among surgical patients. Results of a national study.

OBJECTIVE: To assess the overall burden of healthcare-associated infections (HAIs) in patients exposed and nonexposed to surgery. BACKGROUND: Targeted HAI surveillance is common in healthcare institutions, but may underestimate the overall burden of disease. METHODS: Prevalence study among patients hospitalized in 50 acute care hospitals participating in the Swiss Nosocomial Infection Prevalence surveillance program. RESULTS: Of 8273 patients, 3377 (40.8%) had recent surgery. Overall, HAI was present in 358 (10.6%) patients exposed to surgery, but only in 206 (4.2%) of 4896 nonexposed (P < 0.001). Prevalence of surgical site infection (SSI) was 5.4%. Healthcare-associated infections prevalence excluding SSI was 6.5% in patients with surgery and 4.7% in those without (P < 0.0001). Patients exposed to surgery carried less intrinsic risk factors for infection (age >60 years, 55.6% vs 63.0%; American Society of Anesthesiologists score >3,5.9% vs 9.3%; McCabe for rapidly fatal disease, 3.9% vs 6.6%; Charlson comorbidity index >2, 12.3% vs 20.9%, respectively; all P < 0.001) than those nonexposed, but more extrinsic risk factors (urinary catheters, 39.6%vs 14.1%; central venous catheters, 17.8% vs 7.1%; mechanical ventilation, 4.7% vs 1.3%; intensive care stay, 18.3% vs 8.8%, respectively; all P<0.001). Exposure to surgery independently predicted an increased risk of HAI (odds ratio 2.43; 95% CI 2.0­3.0). CONCLUSIONS: Despite a lower intrinsic risk, patients exposed to surgery carried more than twice the overall HAI burden than those nonexposed; almost half was accountable to SSI. Extending infection control efforts beyond SSI prevention in these patients might be rewarding, especially because of the extrinsic nature of risk factors.

Genetic diversity and ecological success of Staphylococcus aureus strains colonizing humans.

The genetic determinants and phenotypic traits which make a Staphylococcus aureus strain a successful colonizer are largely unknown. The genetic diversity and population structure of 133 S. aureus isolates from healthy, generally risk-free adult carriers were investigated using four different typing methods: multilocus sequence typing (MLST), amplified fragment length polymorphism analysis (AFLP), double-locus sequence typing (DLST), and spa typing were compared. Carriage isolates displayed great genetic diversity which could only be revealed fully by DLST. Results of AFLP and MLST were highly concordant in the delineation of genotypic clusters of closely related isolates, roughly equivalent to clonal complexes. spa typing and DLST provided considerably less phylogenetic information. The resolution of spa typing was similar to that of AFLP and inferior to that of DLST. AFLP proved to be the most universal method, combining a phylogeny-building capacity similar to that of MLST with a much higher resolution. However, it had a lower reproducibility than sequencing-based MLST, DLST, and spa typing. We found two cases of methicillin-resistant S. aureus colonization, both of which were most likely associated with employment at a health service. Of 21 genotypic clusters detected, 2 were most prevalent: cluster 45 and cluster 30 each colonized 24% of the carrier population. The number of bacteria found in nasal samples varied significantly among the clusters, but the most prevalent clusters were not particularly numerous in the nasal samples. We did not find much evidence that genotypic clusters were associated with different carrier characteristics, such as age, sex, medical conditions, or antibiotic use. This may provide empirical support for the idea that genetic clusters in bacteria are maintained in the absence of adaptation to different niches. Alternatively, carrier characteristics other than those evaluated here or factors other than human hosts may exert selective pressure maintaining genotypic clusters.