The effect of control group selection in the analysis of risk factors for extended spectrum β-lactamase-producing Klebsiella pneumoniae infections. A prospective controlled study

Risk factors for bloodstream infections due to carbapenem-resistant Enterobacterales: a nested case-control-control study

BACKGROUND

Carbapenem-resistant Enterobacterales (CRE) bloodstream infections (BSIs) are a major threat to patients. To date, data on risk factors have been limited, with low internal and external validity. In this multicentre study, risk factors for CRE BSI were determined by comparison with two control groups: patients with carbapenem-susceptible Enterobacterales (CSE) BSI, and patients without Enterobacterales infection (uninfected patients).

METHODS

A multicentre, case-control-control study was nested in a European prospective cohort study on CRE (EURECA). CRE BSI:CSE BSI matching was 1:1, CRE BSI:Uninfected patients matching was 1:3, based on hospital, ward and length of stay. Conditional logistic regression was applied.

RESULTS

From March 2016 to November 2018, 73 CRE BSIs, 73 CSE BSIs and 219 uninfected patients were included from 18 European hospitals. For CRE versus CSE BSI, previous CRE colonization/infection [incidence rate ratio (IRR) 7.32; 95% CI 1.65-32.38) increased the risk. For CRE versus uninfected controls, independent risk factors included: older age (IRR 1.03; 95% CI 1.01-1.06), patient referral (long-term care facility: IRR 7.19; 95% CI 1.51-34.24; acute care hospital: IRR 5.26; 95% CI 1.61-17.11), previous colonization/infection with other MDR organisms (MDROs) (IRR 9.71; 95% CI 2.33-40.56), haemodialysis (IRR 8.59; 95% CI 1.82-40.53), invasive procedures (IRR 5.66; 95% CI 2.11-15.16), and β-lactam/β-lactamase inhibitor combinations (IRR 3.92; 95% CI 1.68-9.13) or third/fourth generation cephalosporin (IRR 2.75; 95% CI 1.06-7.11) exposure within 3 months before enrolment.

CONCLUSIONS

Evidence of previous CRE colonization/infection was a major risk factor for carbapenem resistance among Enterobacterales BSI. Compared with uninfected patients, evidence of previous MDRO colonization/infection and healthcare exposure were important risk factors for CRE BSI. Targeted screening, infection prevention and antimicrobial stewardship should focus on these high-risk patients.

Weighted nearest neighbours-based control group selection method for observational studies

Although in observational studies, propensity score matching is the most widely used balancing method, it has received much criticism. The main drawback of this method is that the individuals of the case and control groups are paired in the compressed one-dimensional space of propensity scores. In this paper, such a novel multivariate weighted k-nearest neighbours-based control group selection method is proposed which can eliminate this disadvantage of propensity score matching. The proposed method pairs the elements of the case and control groups in the original vector space of the covariates and the dissimilarities of the individuals are calculated as the weighted distances of the subjects. The weight factors are calculated from a logistic regression model fitted on the status of treatment assignment. The efficiency of the proposed method was evaluated by Monte Carlo simulations on different datasets. Experimental results show that the proposed Weighted Nearest Neighbours Control Group Selection with Error Minimization method is able to select a more balanced control group than the most widely applied greedy form of the propensity score matching method, especially for individuals characterized with few descriptive features.

Risk factors for carbapenem-resistant Klebsiella pneumoniae infection relative to two types of control patients: a systematic review and meta-analysis

Background

Studies on risk factors for carbapenem-resistant Klebsiella pneumoniae (CRKP) infection have provided inconsistent results, partly due to the choice of the control group. We conducted a systematic review and meta-analysis to assess the risk factors for CRKP infection by comparing CRKP-infected patients with two types of controls: patients infected with carbapenem-susceptible Klebsiella pneumoniae (comparison 1) or patients not infected with CRKP (comparison 2).

Methods

Data on potentially relevant risk factors for CRKP infection were extracted from studies indexed in PubMed, EMBASE, Web of Science or EBSCO databases from January 1996 to April 2019, and meta-analyzed based on the outcomes for each type of comparison.

Results

The meta-analysis included 18 studies for comparison 1 and 14 studies for comparison 2. The following eight risk factors were common to both comparisons: admission to intensive care unit (ICU; odds ratio, OR_{comparison 1} = 3.20, OR_{comparison 2} = 4.44), central venous catheter use (2.62, 3.85), mechanical ventilation (2.70, 4.78), tracheostomy (2.11, 8.48), urinary catheter use (1.99, 0.27), prior use of antibiotic (6.07, 1.61), exposure to carbapenems (4.16, 3.84) and exposure to aminoglycosides (1.85, 1.80). Another 10 risk factors were unique to comparison 1: longer length of hospital stay (OR = 15.28); prior hospitalization (within the previous 6 months) (OR = 1.91); renal dysfunction (OR = 2.17); neurological disorders (OR = 1.52); nasogastric tube use (OR = 2.62); dialysis (OR = 3.56); and exposure to quinolones (OR = 2.11), fluoroquinolones (OR = 2.03), glycopeptides (OR = 3.70) and vancomycin (OR = 2.82).

Conclusions

Eighteen factors may increase the risk of carbapenem resistance in K. pneumoniae infection; eight factors may be associated with both K. pneumoniae infections in general and CRKP in particular. The eight shared factors are likely to be ‘true’ risk factors for CRKP infection. Evaluation of risk factors in different situations may be helpful for empirical treatment and prevention of CRKP infections.

Risk factors of extended-spectrum beta-lactamaseproducing Enterobacteriaceae bacteremia in Thai emergency department: a retrospective case-control study

Background: Infections caused by resistant extended-spectrum beta-lactamase (ESBL)-producing enteric bacteria and their risk factors are globally recognized. However, such risk factors have not been explored in emergency department (ED) where the first choice of empirical antimicrobials is crucial.

Objective: Determine risk factors of ESBL bacteremia in ED, especially in our geographic area.

Methods: A retrospective case-double-control study was conducted at King Chulalongkorn Memorial Hospital. All adult ED patients with ESBL-producing E. coli and K. pneumoniae in blood cultures between October 2007 and October 2008 were recruited for this study. The potential risk factors were analyzed and compared with non- ESBL-producing bacteremic patients (control group 1) and matched general ED patients (control group 2). Nonbeta- lactam susceptibility testing among the cohort was also evaluated.

Results: Thirty ESBL (cases), 103 group 1 controls, and 100 group 2 controls were assessed. Based on the univariate analysis, age, chronic kidney diseases, malignancy, poor functional status, previous hospitalization within 90 days, and previous antimicrobial exposure especially to cephalosporins, quinolones, and carbapenems within 30 days were the risk factors for ESBL bacteremia compared with both types of control patients. Age > 60 and previous cephalosporin use were consistently identified as the risk factors by multivariate models using both control groups. The susceptibility to non-beta-lactam agents in the ESBL group was significantly lower than the non-ESBL. No carbapenem resistance was found.

Conclusion: Elderly ED patients, especially those who had previous cephalosporin exposure within 30 days, were at higher risk of ESBL-producing bacteremic infections. ESBLs tended to have less susceptibility to the non-β-lactam agents.

Enterobacteriaceae resistant to third generation cephalosporins upon hospital admission: risk factors and clinical outcomes

Objectives

Evaluate risk factors and clinical outcomes of infections caused by Enterobacteriaceae resistant to third-generation cephalosporins present in samples collected upon hospital admission.

Methods

Risk factors were evaluated using a 1:2 ratio case–control study. Influence of resistance on the appropriateness of antibiotic therapy, length of stay, and hospital mortality were prospectively evaluated. Characteristics independently associated with the presence of resistant enterobacteria were assessed by logistic regression.

Results

Enterobacteria resistant to third-generation cephalosporins were quite common (26.0%). Male gender (OR: 2.66; 95% CI, 1.17–5.06; p = 0.019), invasive prosthesis (OR: 3.79; 95% CI, 1.29–11.08; p = 0.015), previous use of cephalosporins (OR: 2.77; 95% CI, 1.10–6.97; p = 0.029) and hospitalization in the last 6 months (OR: 5.33; 95% CI, 2.29–12.44; p < 0.001) were independently associated with the presence of these microorganisms. These bacteria were associated with higher frequency of inappropriate antimicrobial therapy, worse clinical response, and longer length of stay. Finally, older age, admission to the ICU, and site of infection other than urinary tract were independently associated to higher hospital mortality.

Conclusions

Risk factors identified in this study may help in the choice of empirical antibiotic therapy for infected patients suspected of harboring these bacteria and in the early implementation of measures to avoid the spread of these bacteria in the hospital environment.

Detecting risk and predicting patient mortality in patients with extended-spectrum β-lactamase-producing Enterobacteriaceae bloodstream infections

Extended-spectrum β-lactamases (ESBLs) have been increasingly described worldwide, especially among Enterobacteriaceae isolates, and recently not only in the nosocomial, but also in the community setting. Bloodstream infections (BSIs) caused by ESBL-producing Enterobacteriaceae have been associated with increased rates of treatment failure, mortality and hospital costs. Any delay in the initiation of adequate antibiotic therapy is potentially lethal for patients with BSIs caused by ESBL-producing Enterobacteriaceae. The awareness of changes in bacterial resistance patterns, the careful knowledge of risk factors for ESBL infection and of factors facilitating adverse outcome, giving attention to local epidemiology, can improve the efficacy of empirical treatment protocols. The aim of this review is to focus on the main characteristics of BSIs caused by ESBL-producing Enterobacteriaceae, with particular emphasis on risk factors for these infections and factors related to mortality.