Seasonal variation in Escherichia coli bloodstream infections in northern Israel

Biofilm Formation by Hospital-Acquired Resistant Bacteria Isolated from Respiratory Samples

BACKGROUND

Hospital-acquired resistant infections (HARI) are infections, which develop 48 h or more after admission to a healthcare facility. HARI pose a considerably acute challenge, due to limited treatment options. These infections are associated bacterial biofilms, which act as a physical barrier to diverse external stresses, such as desiccation, antimicrobials and biocides. We assessed the influence of multiple factors on biofilm production by HARI -associated bacteria.

METHODS

Bacteria were isolated from samples of patients with respiratory HARI who were hospitalized during 2020-2022 in north Israel. Following antibiotic susceptibility testing by disc diffusion or broth microdilution, biofilm formation capacities of resistant bacteria (methicillin-resistant staphylococcus aureus, extended spectrum beta-lactamase-producing Escherichia coli and Klebsiela pneumonia, and multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii) was assessed using the crystalline violet staining method. Data regarding season, time to infection, bacterial species, patient age and gender, year, and medical department were collected from the patient medical records.

RESULTS

Among the 226 study isolates, K. pneumonia was the most prevalent (35.4%) bacteria, followed by P. aeruginosa (23.5%), and methicillin-resistant staphylococcus aureus (MRSA) (21.7%). A significantly higher rate of HARI was documented in 2022 compared to 2020-2021. The majority of isolates (63.3%) were strong biofilm producers, with K. pneumonia (50.3%) being most dominant, followed by P. aeruginosa (29.4%). Biofilm production strength was significantly affected by seasonality and hospitalization length, with strong biofilm production in autumn and in cases where hospitalization length exceeded 30 days.

CONCLUSION

Biofilm production by HARI bacteria is influenced by bacterial species, season and hospitalization length.

Nationwide epidemiology and clinical practice patterns of pediatric urinary tract infections: application of multivariate time-series clustering

BACKGROUND

The nationwide epidemiology and clinical practice patterns for younger children hospitalized with urinary tract infections (UTIs) were unclear.

METHODS

We conducted a retrospective observational study consisting of 32,653 children aged < 36 months who were hospitalized with UTIs from 856 medical facilities during fiscal years 2011-2018 using a nationally representative inpatient database in Japan. We investigated the epidemiology of UTIs and changes in clinical practice patterns (e.g., antibiotic use) over 8 years. A machine learning algorithm of multivariate time-series clustering with dynamic time warping was used to classify the hospitals based on antibiotic use for UTIs.

RESULTS

We observed marked male predominance among children aged < 6 months, slight female predominance among children aged > 12 months, and summer seasonality among children hospitalized with UTIs. Most physicians selected intravenous second- or third-generation cephalosporins as the empiric therapy for treating UTIs, which was switched to oral antibiotics during hospitalizations for 80% of inpatients. Whereas total antibiotic use was constant over the 8 years, broad-spectrum antibiotic use decreased gradually from 5.4 in 2011 to 2.5 days of therapy per 100 patient-days in 2018. The time-series clustering distinctively classified 5 clusters of hospitals based on antibiotic use patterns and identified hospital clusters that preferred to use broad-spectrum antibiotics (e.g., antipseudomonal penicillin and carbapenem).

CONCLUSIONS

Our study provided novel insight into the epidemiology and practice patterns for pediatric UTIs. Time-series clustering can be useful to identify the hospitals with aberrant practice patterns to further promote antimicrobial stewardship. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effect of daily chlorhexidine bathing on reducing infections caused by multidrug-resistant organisms in intensive care unit patients: A semiexperimental study with parallel controls

OBJECTIVE

To assess the effectiveness of daily bathing by chlorhexidine bathing on multidrug-resistant organisms in ICU, especially on carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and carbapenem-resistant Enterobacteriaceae (CRE).

METHODS

Semiexperimental study which employed both precontrols and a parallel control was conducted. In the intervention period (from July 1 to December 31, 2016), strengthened infection control measures and daily bathing with 2% CHG-impregnated wipes once daily was performed in the ICU. Fifty-seven non-ICU wards with the occurrence of multidrug-resistant organisms (MDRO) infections during the same time were selected as parallel control group (only CHG bathing was not performed). The net effect of the 2% CHG daily bathing was evaluated by the difference in difference (DID) model.

RESULTS

The DID model analysis showed that CHG bathing reduced the incidence of CRAB- and CRPA-caused infections in ICU by 1.56 and 2.15 cases/1000 patient days, and bathing of every 19 patients (95CI% 13 to 41) and 39 patients (95CI% 24 to 110) were able to prevent one case of HAIs of total MDROs and CRPA, respectively. However, CHG bathing showed no effect on MRSA, VRE, and CRE (p > 0.05).

CONCLUSION

Daily bathing with 2% CHG-impregnated wipes can reduce HAIs caused by CRAB and CRPA, while it is not effective for the prevalence of infections caused by MRSA, VRE, and CRE.

How Antimicrobial Resistance Is Linked to Climate Change: An Overview of Two Intertwined Global Challenges

Globally, antimicrobial resistance (AMR) and climate change (CC) are two of the top health emergencies, and can be considered as two interlinked public health priorities. The complex commonalities between AMR and CC should be deeply investigated in a One Health perspective. Here, we provided an overview of the current knowledge about the relationship between AMR and CC. Overall, the studies included pointed out the need for applying a systemic approach to planetary health. Firstly, CC increasingly brings humans and animals into contact, leading to outbreaks of zoonotic and vector-borne diseases with pandemic potential. Although it is well-established that antimicrobial use in human, animal and environmental sectors is one of the main drivers of AMR, the COVID-19 pandemic is exacerbating the current scenario, by influencing the use of antibiotics, personal protective equipment, and biocides. This also results in higher concentrations of contaminants (e.g., microplastics) in natural water bodies, which cannot be completely removed from wastewater treatment plants, and which could sustain the AMR spread. Our overview underlined the lack of studies on the direct relationship between AMR and CC, and encouraged further research to investigate the multiple aspects involved, and its effect on human health.

Air temperature and incidence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae

BACKGROUND

Higher outdoor temperature may be related to an increase in antibiotic resistant bacteria. We investigated the association between local outdoor air temperature and the incidence of extended-spectrum betalactamase (ESBL)-producing Enterobacteriaceae (ESBL-PE) correcting for known drivers of antibiotic resistance.

METHODS

We performed a time-series regression study using prospectively collected weekly surveillance data on all ESBL-PE isolated from in- and outpatients of the University Hospital Basel, a tertiary care center in Switzerland, between 01/2008-12/2017. Temperature was measured hourly at the meteorological institute of the University Basel next to our institution over this time period. A time-series approach using a Poisson regression model and different lag terms for delayed exposure effects was performed to assess associations between minimal, mean and maximal weekly temperature and the number of ESBL-PE recovered.

RESULTS

Over 10 years, recovery of ESBL-PE increased (annual incidence rate ratio [IRR] 1.14, 95%CI 1.13-1.16), while mean weekly temperature measures remained stable. In multivariable analyses, increasing temperature was associated with higher recovery rates of ESBL-PE after three to four weeks, correcting for potential confounders, such as the number of admissions, proportion of long-term nursing facility- and ICU-admissions, age, Charlson comorbidity index and consumption of antimicrobials (IRRs per 10 °C ranging from 1.14 to 1.22, 95%CIs 1.07-1.33). These trends remained when analyzing correlations between temperature with the proportion of extended spectrum cephalosporin resistance of all recovered Enterobacteriaceae.

CONCLUSIONS

Higher outdoor temperature may be associated with an increase of ESBL-PE-incidence, independent of important confounders, such as antimicrobial consumption and thus should be considered for future resistance-trajectories.

Effect of temperature on Escherichia coli bloodstream infection in a nationwide population-based study of incidence and resistance

BACKGROUND

The incidence of Escherichia coli bloodstream infections (BSI) is high and increasing. We aimed to describe the effect of season and temperature on the incidence of E. coli BSI and antibiotic-resistant E. coli BSI and to determine differences by place of BSI onset.

METHODS

All E. coli BSI in adult Israeli residents between January 1, 2018 and December 19, 2019 were included. We used the national database of mandatory BSI reports and outdoor temperature data. Monthly incidence and resistance were studied using multivariable negative binomial regressions with season (July-October vs. other) and temperature as covariates.

RESULTS

We included 10,583 events, 9012 (85%) community onset (CO) and 1571 (15%) hospital onset (HO). For CO events, for each average monthly temperature increase of 5.5 °C, the monthly number of events increased by 6.2% (95% CI 1.6-11.1%, p = 0.008) and the monthly number of multidrug-resistant events increased by 4.9% (95% CI 0.3-9.7%, p = 0.04). The effect of season was not significant. For HO events, incidence of BSI and resistant BSI were not associated with temperature or season.

CONCLUSION

Temperature increases the incidence of CO E. coli BSI and CO antibiotic-resistant E. coli BSI. Global warming threatens to increase the incidence of E. coli BSI.

Gram-negative central line-associated bloodstream infection incidence peak during the summer: a national seasonality cohort study

Central line-associated bloodstream infections (CLABSI) cause increased morbidity, mortality, and hospital costs that are partially preventable. The phenomenon of seasonality among CLABSI rates has not been fully elucidated, but has implications for accurate surveillance and infection prevention trials. Longitudinal dynamic cohort of hospitals participating in hospital-wide and intensive care unit bloodstream infection surveillance for at least one full year over 2000 to 2014. Mixed-effects negative binomial regression analysis calculated the peak-to-low ratio between months as an adjusted CLABSI incidence rate ratio (IRR) with 95% confidence intervals (CI). Multivariate regression models examined the associations between CLABSI pathogens and ambient temperature and relative humidity. The study population included 104 hospital sites comprising 11,239 CLABSI. Regression analysis identified a hospital-wide increase in total CLABSI during July-August, with a higher gram-negative peak-to-low incidence rate ratio (IRR 2.52 [95% CI 1.92-3.30], p < 0.001) compared to gram-positive bacteria (IRR 1.29 [95% CI 1.11-1.48], p < 0.001). Subgroup analysis replicated this trend for CLABSI diagnosed in the intensive care unit. Only gram-negative CLABSI rates were associated with increased temperature (IRR + 30.3% per 5 °C increase [95% CI 17.3-43.6], p < 0.001) and humidity (IRR + 22.9% per 10% increase [95% CI 7.7-38.3), p < 0.001). The incidence and proportion of gram-negative CLABSI approximately doubled during the summer periods. Ambient temperature and humidity were associated with increases of hospital-acquired gram-negative infections. CLABSI surveillance, preventive intervention trials and epidemiological studies should consider seasonal variation and climatological factors when preparing study designs or interpreting their results.

Seasonal Variation of Chronic Villitis of Unknown Etiology

INTRODUCTION

Chronic villitis of unknown etiology (VUE) is a chronic inflammatory lesion of the placenta. VUE is hypothesized to result from an alloimmune response or as response to an unidentified infection. Lack of a seasonal trend is thought to support VUE as an alloimmune response, though data on seasonal VUE trends are limited.

METHODS

Data were obtained from a hospital in Chicago, Illinois, from 2011-2016. Placentas sent to pathology were reviewed using a standardized protocol, and VUE cases were identified based on an automated text search of pathology records. We used monthly VUE prevalence estimates to investigate the annual trend, and we used Poisson regression to evaluate seasonal variation in the number of VUE cases.

RESULTS

There were 79 825 deliveries within the study period. Pathologists evaluated 12 074 placentas and identified 2873 cases of VUE. Regression results indicate that the risk of VUE is 16% to 17% higher in the fall and winter as compared to the summer (fall relative risk [RR]: 1.17, 95% confidence interval [CI]: 1.06-1.29; winter RR: 1.16, 95% CI: 1.05-1.29).

DISCUSSION

Our results suggest that there may be seasonal variation in VUE prevalence, particularly for low-grade VUE. Future studies should evaluate seasonal variation in a representative sample rather than relying on pathology reports to estimate prevalence.

Summer, sun and sepsis-The influence of outside temperature on nosocomial bloodstream infections: A cohort study and review of the literature

BACKGROUND

The incidence of many infections is seasonal e.g. surgical site infections, urinary tract infection and bloodstream infections. We questioned whether there is seasonal variation even in climate-controlled hospitalized patients, and analyzed the influence of climate parameters on nosocomial bloodstream infections.

METHODS AND FINDINGS

The retrospective cohort study is based on two databases: The German national surveillance system for nosocomial infections in intensive care units (ICU-KISS) from 2001 to 2015 and aggregated monthly climate data. Primary bloodstream infection (PBSI) is defined as a positive blood culture with one (or more) pathogen(s) which are not related to an infection on another site and which were not present at admission. Monthly infection data were matched with postal code, calendar month and corresponding monthly climate and weather data. All analyses were exploratory in nature. 1,196 ICUs reported data on PBSI to KISS. The ICUs were located in 779 hospitals and in 728 different postal codes in Germany. The majority of the 19,194 PBSI were caused by gram-positive bacteria. In total, the incidence density of BSI was 17% (IRR 1.168, 95%CI 1.076-1.268) higher in months with high temperatures (≥20°C) compared to months with low temperatures (<5°C). The effect was most prominent for gram-negatives; more than one third (38%) higher followed by gram-positives with 13%. Fungi reached their highest IRR at moderately warm temperatures between 15-20°C. At such temperatures fungi showed an increase of 33% compared to temperatures below 5°C. PBSI spiked in summer with a peak in July and August. PBSI differed by pathogen: The majority of bacteria increased with rising temperatures. Enterococci showed no seasonality. S. pneumoniae reached a peak in winter time. The association of the occurrence of PBSI and temperatures ≥20°C was stronger when the mean monthly temperature in the month prior to the occurrence of BSI was considered instead of the temperature in the month of the occurrence of BSI. High average temperatures ≥20°C increased the risk of the development of a PBSI by 16% compared with low temperatures <5°C.

CONCLUSIONS

Most nosocomial infections are endogenous in nature; the microbiome plays a crucial role in host health. If gut and skin microbiome varies with season, environmental parameters will contribute to the observed incidence patterns. Similarly, the impact of global warming on both local weather patterns and extreme weather events may influence the acquisition of pathogens. A better understanding of the etiology of these infections is needed to provide guidance for future infection control strategies.

Low-temperature laminar flow ward for the treatment of multidrug resistance Acinetobacter baumannii pneumonia

This study was designed to investigate the effect of low-temperature laminar flow ward (LTLFW) on the Acinetobacter baumannii pneumonia (MDR-ABP) in neurosurgical intensive care unit (NICU) patients. We evaluated whether patients in a LTLFW had significantly improved clinical outcomes as compared to those in nonconstant-temperature NICU (room temperature). The association of temperature with the prevalence of ABP and A. baumannii isolates (ABI) found in NICU patients was specifically investigated. In vitro microbiological experiments were conducted to measure the proliferation, antibiotic sensitivity, and genomic profiles of A. baumannii (AB) that grew in variable temperatures. MDR-ABP patients in LTLFW had significantly improved outcomes than those in the room temperature NICU. In addition, the numbers of ABI were positively associated with mean ambient outdoor temperatures (P = 0.002), with the incidence of ABP and average numbers of ABI among NICU patients being substantially lower in the winter as compared to other seasons. However, there were no significant seasonal variations in the other strains of the top five bacteria. Consistent with these clinical observations, AB growing at 20°C and 25°C had significantly reduced viability and antibiotic resistance compared to those growing at 35°C. The expression of genes related to AB survival ability, drug resistance, and virulence also differed between AB growing at 20°C and those at 35°C. LTLFW is effective in promoting the recovery of MDR-ABP patients because low temperatures reduced the density and virulence of AB and enhanced the efficacy of antibiotics, likely at the genetic level.

Healthcare-associated bloodstream infection trends under a provincial surveillance program

OBJECTIVE

BACTOT, Quebec's healthcare-associated bloodstream infection (HABSI) surveillance program has been operating since 2007. In this study, we evaluated the changes in HABSI rates across 10 years of BACTOT surveillance under a Bayesian framework.

DESIGN

A retrospective, cohort study of eligible hospitals having participated in BACTOT for at least 3 years, regardless of their entry date. Multilevel Poisson regressions were fitted independently for cases of HABSI, catheter-associated bloodstream infections (CA-BSIs), non-catheter-associated primary BSIs (NCA-BSIs), and BSIs secondary to urinary tract infections (BSI-UTIs) as the outcome and log of patient days as the offset. The log of the mean Poisson rate was decomposed as the sum of a surveillance year effect, period effect, and hospital effect. The main estimate of interest was the cohort-level rate in years 2-10 of surveillance relative to year 1.

RESULTS

Overall, 17,479 cases and 33,029,870 patient days were recorded for the cohort of 77 hospitals. The pooled 10-year HABSI rate was 5.20 per 10,000 patient days (95% CI, 5.12-5.28). For HABSI, CA-BSI, and BSI-UTI, there was no difference between the estimated posterior rates of years 2-10 compared to year 1. The posterior means of the NCA-BSI rate ratios increased from the seventh year until the tenth year, when the rate was 29% (95% confidence interval, 1%-89%) higher than the first year rate.

CONCLUSIONS

HABSI rates and those of the most frequent subtypes remained stable over the surveillance period. To achieve reductions in incidence, we recommend that more effort be expended in active interventions against HABSI alongside surveillance.

The relationship of seasonality and the increase in urinary tract infections among hospitalized patients with spinal cord injury

BACKGROUND

Urinary tract infection (UTI) is the most frequent complication in patients who have spinal cord injury (SCI). The occurrence rate of UTI in this type of hospitalized patients was correlated to seasonality, age, and gender.

METHODS

Patients hospitalized during the 4-year study period with underlying SCI were identified from Taiwan's National Health Insurance Research Database. Patients with a discharge diagnosis of UTI were identified as those with SCI and UTI; they were divided into the following four age groups: <18 years, 18 to 44 years, 45 to 64 years, and ≥65 years. The gender, monthly number of cases, major complication rate, seasonal differences, and odds ratios (ORs) of associated factors were analyzed.

RESULTS

Data of 30 149 hospitalized patients diagnosed with SCI were retrieved. SCI and UTI were diagnosed in 3405 (11.3%) patients, of them 2296 were males (67.4%) and 1109 were females (32.6%). The UTI occurrence rate in hospitalized SCI patients was higher in males (11.8%) than in females (10.4%) (OR: 1.24; 95% CI: 1.15-1.34); it was highest in the ≥65-year-old age group (12.8%) and lowest in the <18-year-old age group (5.8%) (OR: 2.51; 95% CI: 1.83-3.44). The UTI occurrence rate varied from 7% to 18%, and it was highest in the summer (13.0% ± 2.6%) and lowest in the winter (10.2% ± 1.9%) (OR: 1.27; 95% CI: 1.15-1.40). Acute pyelonephritis was the most common complication in SCI and UTI cases.

CONCLUSION

The mean occurrence rate of UTI in hospitalized SCI patients was 11.3%; it was higher in males, in patients aged ≥65 years, and in the summer. Therefore, physicians should pay attention to the occurrence of UTI in aged male patients with SCI, especially in the summer.

Seasonal Variation and Weather Changes Related to the Occurrence and Severity of Acute Hematogenous Osteomyelitis in Children

BACKGROUND

Acute hematogenous osteomyelitis (AHO) demonstrates regional variability in incidence and severity. In this study, we evaluated seasonal variations of AHO and assessed the effects of weather trends on the occurrence and severity of illness in affected children.

METHODS

National Weather Service data from the dates of symptom onset and of admission of children with AHO were gathered. Seasonal occurrence rates and the weather patterns were studied according to severity-of-illness category. Statistical analysis was performed with Pearson and Spearman correlations and analysis of variance.

RESULTS

A total of 209 children with AHO were admitted within 21 days of symptom onset (average, 5.0 ± 3.8 days). Severity-of-illness scores ranged from 0 to 10 (average, 3.2 ± 3.2). Symptom onset occurred most commonly in summer (73 [34.9%]) or spring (54 [25.8%]). We found a significant correlation between severity of illness and minimum temperature at symptom onset during the summer season (P = .020). A significant change in average humidity (21.6%) occurred during the winter between the date of symptom onset and the date of admission for children with severe illness (P = .020).

DISCUSSION

This study identified seasonal variation in the occurrence of AHO in children; summer was the most common season for occurrence. To our knowledge, this is the first detailed evaluation of weather parameters and trends in weather changes from symptom onset to admission with consideration of the effects of weather on the occurrence of infection and severity of illness.

Seasonal Variation of Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae Bacteremia According to Acquisition and Patient Characteristics: A Population-Based Study

OBJECTIVE Seasonal variation is a characteristic of many infectious diseases, but relatively little is known about determinants thereof. We studied the impact of place of acquisition and patient characteristics on seasonal variation of bacteremia caused by the 3 most common pathogens. DESIGN Seasonal variation analysis. METHODS In 3 Danish health regions (2.3 million total inhabitants), patients with bacteremia were identified from 2000 through 2011 using information from laboratory information systems. Analyses were confined to Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Additional data were obtained from the Danish National Hospital Registry for the construction of admission histories and calculation of the Charlson comorbidity index (CCI). Bacteremias were categorized as community acquired, healthcare associated (HCA), and hospital acquired. We defined multiple subgroups by combining the following characteristics: species, acquisition, age group, gender, CCI level, and location of infection. Assuming a sinusoidal model, seasonal variation was assessed by the peak-to-trough (PTT) ratio with a 95% confidence interval (CI). RESULTS In total, we included 16,006 E. coli, 6,924 S. aureus, and 4,884 S. pneumoniae bacteremia cases. For E. coli, the seasonal variation was highest for community-acquired cases (PTT ratio, 1.24; 95% CI, 1.17-1.32), was diminished for HCA (PTT ratio, 1.14; 95% CI, 1.04-1.25), and was missing for hospital-acquired cases. No seasonal variation was observed for S. aureus. S. pneumoniae showed high seasonal variation, which did not differ according to acquisition (overall PTT ratio, 3.42; 95% CI, 3.10-3.83). CONCLUSIONS Seasonal variation was mainly related to the species although the place of acquisition was important for E. coli. Infect Control Hosp Epidemiol 2016;37:946-953.

Seasonal changes in the incidence of Escherichia coli bloodstream infection: variation with region and place of onset

Previous research has shown that Escherichia coli infection rates peak in the summer; however, to date there has been no investigation as to whether this is seen in both hospital and community-onset cases, and how this differs across regions. We investigated and quantified E. coli bloodstream infection (BSI) seasonality. A generalized additive Poisson model was fitted to mandatory E. coli BSI surveillance data reported in England. There was no impact of seasonality in hospital-onset cases; however, for the community-onset cases, there was statistically significant seasonal variation over time nationally. When examined regionally, seasonality was significant in the North of England only. This variation resulted in an absolute increase of 0.06 (95% CI 0.02-0.1) cases above the mean (3.25) in each hospital trust for each week of the peak summer season, and a decrease of (-) 0.07 (95% CI -0.1 to -0.03) in the autumn. We estimate that fewer than one hospital bed-day per week per hospital is lost because of seasonal increases during the summer. Our findings highlight the need to understand the distinct community and hospital dynamics of E. coli BSI, and to explore the regional differences driving the variation in incidence, in order to design and implement effective control measures.

The warmer the weather, the more gram-negative bacteria - impact of temperature on clinical isolates in intensive care units

Background

We investigated the relationship between average monthly temperature and the most common clinical pathogens causing infections in intensive care patients.

Methods

A prospective unit-based study in 73 German intensive care units located in 41 different hospitals and 31 different cities with total 188,949 pathogen isolates (102,377 Gram-positives and 86,572 Gram-negatives) from 2001 to 2012. We estimated the relationship between the number of clinical pathogens per month and the average temperature in the month of isolation and in the month prior to isolation while adjusting for confounders and long-term trends using time series analysis. Adjusted incidence rate ratios for temperature parameters were estimated based on generalized estimating equation models which account for clustering effects.

Results

The incidence density of Gram-negative pathogens was 15% (IRR 1.15, 95%CI 1.10–1.21) higher at temperatures ≥20°C than at temperatures below 5°C. E. cloacae occurred 43% (IRR = 1.43; 95%CI 1.31–1.56) more frequently at high temperatures, A. baumannii 37% (IRR = 1.37; 95%CI 1.11–1.69), S. maltophilia 32% (IRR = 1.32; 95%CI 1.12–1.57), K. pneumoniae 26% (IRR = 1.26; 95%CI 1.13–1.39), Citrobacter spp. 19% (IRR = 1.19; 95%CI 0.99–1.44) and coagulase-negative staphylococci 13% (IRR = 1.13; 95%CI 1.04–1.22). By contrast, S. pneumoniae 35% (IRR = 0.65; 95%CI 0.50–0.84) less frequently isolated at high temperatures. For each 5°C increase, we observed a 3% (IRR = 1.03; 95%CI 1.02–1.04) increase of Gram-negative pathogens. This increase was highest for A. baumannii with 8% (IRR = 1.08; 95%CI 1.05–1.12) followed by K. pneumoniae, Citrobacter spp. and E. cloacae with 7%.

Conclusion

Clinical pathogens vary by incidence density with temperature. Significant higher incidence densities of Gram-negative pathogens were observed during summer whereas S. pneumoniae peaked in winter. There is increasing evidence that different seasonality due to physiologic changes underlies host susceptibility to different bacterial pathogens. Even if the underlying mechanisms are not yet clear, the temperature-dependent seasonality of pathogens has implications for infection control and study design.

A method to assess seasonality of urinary tract infections based on medication sales and google trends

BACKGROUND

Despite the fact that urinary tract infection (UTI) is a very frequent disease, little is known about its seasonality in the community.

METHODS AND FINDINGS

To estimate seasonality of UTI using multiple time series constructed with available proxies of UTI. Eight time series based on two databases were used: sales of urinary antibacterial medications reported by a panel of pharmacy stores in France between 2000 and 2012, and search trends on the Google search engine for UTI-related terms between 2004 and 2012 in France, Germany, Italy, the USA, China, Australia and Brazil. Differences between summers and winters were statistically assessed with the Mann-Whitney test. We evaluated seasonality by applying the Harmonics Product Spectrum on Fast Fourier Transform. Seven time series out of eight displayed a significant increase in medication sales or web searches in the summer compared to the winter, ranging from 8% to 20%. The eight time series displayed a periodicity of one year. Annual increases were seen in the summer for UTI drug sales in France and Google searches in France, the USA, Germany, Italy, and China. Increases occurred in the austral summer for Google searches in Brazil and Australia.

CONCLUSIONS

An annual seasonality of UTIs was evidenced in seven different countries, with peaks during the summer.

Seasonal variation in the occurrence of delirium in patients admitted to medical units of a general hospital in Italy

OBJECTIVE

Delirium syndrome is common in the hospitalised population. However, data on its aetiological factors are scarce. Clinical observations suggest a relationship between delirium occurrence and seasons. The aim of study was to determine whether a seasonal variation exists in the occurrence of delirium events in-hospital patients.

METHODS

The study included all admissions to the medical units of the Hospital of Ferrara, Italy, between January 2002 and December 2010. On the basis of date admission, cases have been analysed for seasonal variation (four 3-month intervals by seasons) by means of conventional statistics. Moreover, cases categorised into twelve 1-month intervals were also analysed by means of a validated chronobiologic inferential method (single cosinor) to search for cyclic variability.

RESULTS

During the analysed period, the hospital database contained 74 379 records referring to 42 625 subjects (52.7% females). Delirium diagnoses were 1300 (1.7% of total sample), 668 of whom in females (51.4%) and 632 in males (48.6%). Events of delirium were more frequent in winter and autumn (26.6 and 26.5%, respectively) than in spring (23.5%) and summer (23.4%). Chronobiological analysis yielded a significant peak of delirium events in January, when considering both the total raw number of cases and the percent of admissions.

CONCLUSIONS

The study seems to indicate in patients hospitalised in medical units, a higher rate of occurrence of delirium in autumn-winter, similar to that reported for acute medical diseases. The role of possible underlying favouring or triggering factors deserves further research.

Methods to assess seasonal effects in epidemiological studies of infectious diseases--exemplified by application to the occurrence of meningococcal disease

Seasonal variation in occurrence is a common feature of many diseases, especially those of infectious origin. Studies of seasonal variation contribute to healthcare planning and to the understanding of the aetiology of infections. In this article, we provide an overview of statistical methods for the assessment and quantification of seasonality of infectious diseases, as exemplified by their application to meningococcal disease in Denmark in 1995-2011. Additionally, we discuss the conditions under which seasonality should be considered as a covariate in studies of infectious diseases. The methods considered range from the simplest comparison of disease occurrence between the extremes of summer and winter, through modelling of the intensity of seasonal patterns by use of a sine curve, to more advanced generalized linear models. All three classes of method have advantages and disadvantages. The choice among analytical approaches should ideally reflect the research question of interest. Simple methods are compelling, but may overlook important seasonal peaks that would have been identified if more advanced methods had been applied. For most studies, we suggest the use of methods that allow estimation of the magnitude and timing of seasonal peaks and valleys, ideally with a measure of the intensity of seasonality, such as the peak-to-low ratio. Seasonality may be a confounder in studies of infectious disease occurrence when it fulfils the three primary criteria for being a confounder, i.e. when both the disease occurrence and the exposure vary seasonally without seasonality being a step in the causal pathway. In these situations, confounding by seasonality should be controlled as for any confounder.

Seasonality in Gram-negative and healthcare-associated infections

To assess seasonal variations in Gram-negative and healthcare-associated infections (HCAIs), a literature search was performed with combinations of the keywords 'seasonality', 'seasonal variations', 'Gram-negative bacilli', 'infections', 'nosocomial infections', and 'health care associated infections', to retrieve articles published in English in peer-reviewed journals from 1 January 1970 to 29 February 2012. Seasonality was demonstrated for infections, mostly bloodstream infections (BSIs), caused by Acinetobacter spp., Escherichia coli, Enterobacter cloacae, Klebsiella spp., and Pseudomonas aeruginosa, with higher rates of infection during the summer months in North America, Europe, the Middle East, Australia, and Asia. Correlations were observed between temperature increase and rates of BSI for Acinetobacter spp., P. aeruginosa, E. coli, Klebsiella pneumoniae, and extended-spectrum β-lactamase-producing Enterobacteriaceae. A significant correlation between lower urinary tract infections and higher temperature and decreased relative humidity could explain the seasonality of some BSIs. Regarding HCAI, seasonality is intrinsically present in most viral respiratory and gastrointestinal infections, because viruses are introduced into hospitals during seasonal community outbreaks. Other HCAIs subject to seasonal variations include surgical wound infections, with winter peaks in the USA and summer peaks in Finland, central-line-associated BSIs in haematology/oncology paediatric outpatients, and dialysis-associated peritonitis. In summary, seasonal variations have been shown for infections caused by many Gram-negative bacilli, as well as for a few HCAIs, but many studies remain to be performed in order to better understand the mechanisms of these variations.

Increasing incidence of Escherichia coli bacteraemia is driven by an increase in antibiotic-resistant isolates: electronic database study in Oxfordshire 1999-2011

OBJECTIVES

To investigate trends in Escherichia coli resistance, bacteraemia rates and post-bacteraemia outcomes over time.

METHODS

Trends in E. coli bacteraemia incidence were monitored from January 1999 to June 2011 using an infection surveillance database including microbiological, clinical risk factor, infection severity and outcome data in Oxfordshire, UK, with imported temperature/rainfall data.

RESULTS

A total of 2240 E. coli (from 2080 patients) were studied, of which 1728 (77%) were susceptible to co-amoxiclav, cefotaxime, ciprofloxacin and gentamicin. E. coli bacteraemia incidence increased from 3.4/10,000 bedstays in 1999 to 5.7/10,000 bedstays in 2011. The increase was fastest around 2006, and was essentially confined to organisms resistant to ciprofloxacin, co-amoxiclav, cefotaxime and/or aminoglycosides. Resistant E. coli isolation rates increased similarly in those with and without recent hospital contact. The sharp increase also occurred in urinary isolates, with similar timing. In addition to these long-term trends, increases in ambient temperature, but not rainfall, were associated with increased E. coli bacteraemia rates. It is unclear whether resistant E. coli bacteraemia rates are currently still increasing [incidence rate ratio = 1.07 per annum (95% CI = 0.99-1.16), P = 0.07], whereas current susceptible E. coli bacteraemia rates are not changing significantly [incidence rate ratio = 1.01 (95% CI = 0.99-1.02)]. However, neither mortality nor biomarkers associated with mortality (blood creatinine, urea/albumin concentrations, neutrophil counts) changed during the study.

CONCLUSIONS

E. coli bacteraemia rates have risen due to rising rates of resistant organisms; little change occurred in susceptible E. coli. Although the severity of resistant infections, and their outcome, appear similar to susceptible E. coli in the setting studied, the increasing burden of highly resistant organisms is alarming and merits on-going surveillance.