Influence of Matching for Exposure Time on Estimates of Attributable Mortality Caused by Nosocomial Bacteremia in Critically Ill Patients

The Impact of Nosocomial Bloodstream Infections on Mortality: A Retrospective Propensity-Matched Cohort Study

Background

The mortality toll of nosocomial infections drives infection control efforts. We aimed to assess the contemporary mortality associated with nosocomial bloodstream infections (BSIs).

Methods

Retrospective propensity-matched cohort study conducted in 1 hospital in Israel between January 2010-December 2020. Adults >18 years old with nosocomial BSI were matched to controls using nearest neighbor matching of the propensity score for nosocomial BSI. We assessed all-cause mortality at 30 days, 90 days, and survival up to 1 year starting on the BSI day or matched hospital-day among controls; and the functional and cognitive change between admission and discharge using the Norton score among patients discharged alive. Residual differences between matched groups were addressed through Cox regression for 1-year survival.

Results

A total of 1361 patients with nosocomial BSI were matched to 1361 patients without BSI. Matching achieved similar patient groups, with small differences remaining in the Charlson score and albumin and hemoglobin levels. At 90 days, mortality was higher among patients with BSI (odds ratio [OR], 3.36 [95% confidence interval {CI}, 2.77-4.07]). ORs were higher when the BSI was caused by multidrug-resistant bacteria (OR, 5.22 [95% CI, 3.3-8.26]) and with inappropriate empirical antibiotics in the first 24 hours (OR, 3.85 [95% CI, 2.99-4.94]). Following full adjustment, the hazard ratio for 1-year mortality with nosocomial BSI was 2.28 (95% CI, 1.98-2.62). The Norton score declined more frequently among patients with BSI (OR, 2.27 [95% CI, 1.81-2.86]).

Conclusions

Nosocomial BSIs incur a highly significant mortality toll, particularly when caused by multidrug-resistant bacteria. Among hospital survivors, BSIs are associated with functional decline.

The healthcare costs of antimicrobial resistance in Lebanon: a multi-centre prospective cohort study from the payer perspective

Background

Our aim was to examine whether the length of stay, hospital charges and in-hospital mortality attributable to healthcare- and community-associated infections due to antimicrobial-resistant bacteria were higher compared with those due to susceptible bacteria in the Lebanese healthcare settings using different methodology of analysis from the payer perspective .

Methods

We performed a multi-centre prospective cohort study in ten hospitals across Lebanon. The sample size consisted of 1289 patients with documented healthcare-associated infection (HAI) or community-associated infection (CAI). We conducted three separate analysis to adjust for confounders and time-dependent bias: (1) Post-HAIs in which we included the excess LOS and hospital charges incurred after infection and (2) Matched cohort, in which we matched the patients based on propensity score estimates (3) The conventional method, in which we considered the entire hospital stay and allocated charges attributable to CAI. The linear regression models accounted for multiple confounders.

Results

HAIs and CAIs with resistant versus susceptible bacteria were associated with a significant excess length of hospital stay (2.69 days [95% CI,1.5–3.9]; p < 0.001) and (2.2 days [95% CI,1.2–3.3]; p < 0.001) and resulted in additional hospital charges ($1807 [95% CI, 1046–2569]; p < 0.001) and ($889 [95% CI, 378–1400]; p = 0.001) respectively. Compared with the post-HAIs analysis, the matched cohort method showed a reduction by 26 and 13% in hospital charges and LOS estimates respectively. Infections with resistant bacteria did not decrease the time to in-hospital mortality, for both healthcare- or community-associated infections. Resistant cases in the post-HAIs analysis showed a significantly higher risk of in-hospital mortality (odds ratio, 0.517 [95% CI, 0.327–0.820]; p = 0.05).

Conclusion

This is the first nationwide study that quantifies the healthcare costs of antimicrobial resistance in Lebanon. For cases with HAIs, matched cohort analysis showed more conservative estimates compared with post-HAIs method. The differences in estimates highlight the need for a unified methodology to estimate the burden of antimicrobial resistance in order to accurately advise health policy makers and prioritize resources expenditure.

Burden of Antimicrobial Resistance: Compared to What?

The increased focus on the public health burden of antimicrobial resistance (AMR) raises conceptual challenges, such as determining how much harm multidrug-resistant organisms do compared to what, or how to establish the burden. Here, we present a counterfactual framework and provide guidance to harmonize methodologies and optimize study quality. In AMR-burden studies, 2 counterfactual approaches have been applied: the harm of drug-resistant infections relative to the harm of the same drug-susceptible infections (the susceptible-infection counterfactual); and the total harm of drug-resistant infections relative to a situation where such infections were prevented (the no-infection counterfactual). We propose to use an intervention-based causal approach to determine the most appropriate counterfactual. We show that intervention scenarios, species of interest, and types of infections influence the choice of counterfactual. We recommend using purpose-designed cohort studies to apply this counterfactual framework, whereby the selection of cohorts (patients with drug-resistant, drug-susceptible infections, and those with no infection) should be based on matching on time to infection through exposure density sampling to avoid biased estimates. Application of survival methods is preferred, considering competing events. We conclude by advocating estimation of the burden of AMR by using the no-infection and susceptible-infection counterfactuals. The resulting numbers will provide policy-relevant information about the upper and lower bound of future interventions designed to control AMR. The counterfactuals should be applied in cohort studies, whereby selection of the unexposed cohorts should be based on exposure density sampling, applying methods avoiding time-dependent bias and confounding.

Measuring the in-hospital costs of Pseudomonas aeruginosa pneumonia: methodology and results from a German teaching hospital

Background

Pseudomonas aeruginosa-related pneumonia is an ongoing healthcare challenge. Estimating its financial burden is complicated by the time-dependent nature of the disease.

Methods

Two hundred thirty-six cases of Pseudomonas aeruginosa-related pneumonia were recorded at a 2000 bed German teaching hospital between 2011 and 2014. Thirty-five cases (15%) were multidrug-resistant (MDR) Pseudomonas aeruginosa. Hospital- and community-acquired cases were distinguished by main diagnoses and exposure time. The impact of Pseudomonas aeruginosa-related pneumonia on the three endpoints cost, reimbursement, and length of stay was analyzed, taking into account (1) the time-dependent nature of exposure, (2) clustering of costs within diagnostic groups, and (3) additional confounders.

Results

Pseudomonas aeruginosa pneumonia is associated with substantial additional costs that are not fully reimbursed. Costs are highest for hospital-acquired cases (€19,000 increase over uninfected controls). However, community-acquired cases are also associated with a substantial burden (€8400 when Pseudomonas aeruginosa pneumonia is the main reason for hospitalization, and €6700 when not). Sensitivity analyses for hospital-acquired cases showed that ignoring or incorrectly adjusting for time-dependency substantially biases results. Furthermore, multidrug-resistance was rare and only showed a measurable impact on the cost of community-acquired cases.

Conclusions

Pseudomonas aeruginosa pneumonia creates a substantial financial burden for hospitals. This is particularly the case for nosocomial infections. Infection control interventions could yield significant cost reductions. However, to evaluate the potential effectiveness of different interventions, the time-dependent aspects of incremental costs must be considered to avoid introduction of bias.

Exposure density sampling: Dynamic matching with respect to a time-dependent exposure

Estimating the potential risk associated with an exposure occurring over time requires complex statistical techniques, since ignoring the time from study entry until the exposure leads to potentially seriously biased effect estimates. A prominent example is estimating the effect of hospital-acquired infections on adverse outcomes in patients admitted to the intensive care unit. Exposure density sampling has been proposed as an approach to dynamic matching with respect to a time-dependent exposure. Firstly, exposure density sampling can be useful to reduce the workload of study follow up, as it includes all exposed but only a subset of the not yet exposed individuals. Secondly, it can help to obtain a comparable control group by including propensity score matching. In the present article, we provide the theoretical justification that data obtained by exposure density sampling can be analyzed as a left-truncated cohort. It is shown that exposure density sampling allows estimation of the effect of a time-dependent exposure as well as further baseline covariates on a subsequent event, with only minor loss in precision as compared with a full cohort analysis. The sampling is applied to a real data example (hospital-acquired infections in intensive care units) and in a simulation study. We also provide an estimate of the loss in precision in terms of an increased standard error in the reduced data set after exposure density sampling as compared with the full cohort.

Two new flavones glycosides with antimicrobial activities from Clerodendrum formicarum Gürke (Lamiaceae)

Clerodendrum formicarum Gürke from the Lamiaceae family is a Cameroonian medicinal plant. The crude methanol, methanol residual and ethyl acetate extracts of leaves have been phytochemically studied using chromatography column to afford four compounds; two new flavones glycoside: clerodendronone 1a (3) and clerodendronone 1b (4) along with two known compounds: 5,7-dihydroxy-4'-methoxyflavone (1) and 5-hydroxy-7,4'-dimethoxyflavone (2). Compound structures have been elucidated on the basis of their spectroscopy data and with literature information. The anti-microbial activities of extracts and three isolated compounds were performed. The antibacterial activity was evaluated against four gram positive, five gram negative and three fungus. Clerodendronone 1b (4) showed good antibacterial activity against bacterial gram negative Shigella flexineri NR518 (MIC = 62.5 μg/ml) and moderate activity against Staphylococcus aureus NR46374 (MIC = 250 μ/ml). The ethyl acetate extract recorded good antibacterial activity against Staphylococcus aureus NR46003 (MIC = 125 µg/ml) and Staphylococcus aureus NR46374 (MIC = 125 μg/ml).

Assessment of extended-spectrum β-lactamases and integrons among Enterobacteriaceae in device-associated infections: multicenter study in north of Iran

BACKGROUND

Device-associated nosocomial infections (DA-NIs), due to MDR Enterobacteriaceae, are a major threat to patient safety in ICUs. We investigated on Extended-spectrum β-lactamases (ESBL) producing Enterobacteriaceae and incidence of integrons in these bacteria isolated from ventilator-associated pneumonia (VAP) and catheter-associated urinary tract infections (CAUTIs) in 18 governmental hospitals in the north of Iran.

METHODS

In this cross-section study, the antibiotic susceptibility test was performed using the MIC method; also, phenotypically detection of ESBL-producing bacteria was carried out by the double-disk synergy (DDS) test. Presence of ESBL-related genes and integron Classes 1 and 2 was evaluated by the PCR method.

RESULTS

Out of a total of 205 patients with DA-NIs, Enterobacteriaceae were responsible for (72.68%) of infections. The most common DA-NIs caused by Enterobacteriaceae were VAP (77.18%), CAUTI (19.46%), and sepsis due to VAP (3.35%). The most frequently Enterobacteriaceae were; Klebsiella pneumoniae 75 (24; 32% ESBL positive), E. coli 69 (6; 8.69% ESBL positive) and Enterobacter spp. 5 (5; 100% ESBL positive). Distribution of ESBL-related genes was as follows: bla-SHV (94.3%), bla-CTX (48.6%), bla-VEB (22.9%) and bla-GES (17.14%). The incidence rate of integron class 1 and class 2 was (82.92%) and (2.9%) respectively. Eight types of ESBL-producing bacteria were observed.

CONCLUSIONS

Due to the fact that the emergence rate of ESBL Enterobacteriaceae is increasing in DA-NIs, co-incidence of different types of ESBL genes with integrons in 75-100% of strains in our study is alarming for clinicians and healthcare safety managers. Therefore, regional and local molecular level estimations of ESBLs that are agents of DA-NIs are critical for better management of empiric therapy, especially for patients in ICUs.

Fluoroquinolone use is a risk factor for methicillin-resistant Staphylococcus aureus acquisition in long-term care facilities: a nested case-case-control study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is a well-established risk factor for subsequent infection and a key event in interindividual transmission. Some studies have showed an association between fluoroquinolones and MRSA colonization or infection. The present study was performed to identify specific risk factors for MRSA acquisition in long-term care facilities (LTCFs).

METHODS

A prospective cohort of patients naive for S. aureus colonization was established and followed (January 2008 through October 2010) in 4 French LTCFs. Nasal colonization status and potential risk factors were assessed weekly for 13 weeks after inclusion. Variables associated with S. aureus acquisition were identified in a nested-matched case-case-control study using conditional logistic regression models. Cases were patients who acquired MRSA (or methicillin-sensitive S. aureus [MSSA]). Patients whose nasal swab samples were always negative served as controls. Matching criteria were center, date of first nasal swab sample, and exposure time.

RESULTS

Among 451 included patients, 76 MRSA cases were matched to 207 controls and 112 MSSA cases to 208 controls. Multivariable analysis retained fluoroquinolones (odds ratio, 2.17; 95% confidence interval, 1.01-4.67), male sex (2.09; 1.10-3.98), and more intensive care at admission (3.24; 1.74-6.04) as significantly associated with MRSA acquisition, and body-washing assistance (2.85; 1.27-6.42) and use of a urination device (1.79; 1.01-3.18) as significantly associated with MSSA acquisition.

CONCLUSIONS

Our results suggest that fluoroquinolones are a risk factor for MRSA acquisition. Control measures to limit MRSA spread in LTCFs should also be based on optimization of fluoroquinolone use.

Hospital-acquired infections--appropriate statistical treatment is urgently needed!

Research on hospital-acquired infections (HAIs) requires the highest methodological standards to minimize the risk of bias and to avoid misleading interpretation. There are two major issues related specifically to studies in this area, namely the timing of infection and the occurrence of so-called competing risks, which deserve special attention. Just as a patient who acquires a serious infection during hospital admission needs appropriate antibiotic treatment, data being collected in studies on hospital-acquired infections need appropriate statistical analysis. We illustrate the urgent need for appropriate statistical treatment of hospital-acquired infections with some examples from recently conducted studies.The considerations presented are relevant for investigations on risk factors for HAIs as well as for outcome studies.

Risk factors and mortality for nosocomial bloodstream infections in elderly patients

OBJECTIVE

To determine risk factors for nosocomial bloodstream infection (BSI) and associated mortality in geriatric patients in geriatric and internal medicine wards at a university hospital.

METHODS

Single-center retrospective (1992-2007), pairwise-matched (1:1-ratio) cohort study. Geriatric patients with nosocomial BSI were matched with controls without BSI on year of admission and length of hospitalization before onset of BSI. Demographic, microbiological, and clinical data are collected.

RESULTS

One-hundred forty-two BSI occurred in 129 patients. Predominant microorganisms were Escherichia coli (23.2%), coagulase-negative Staphylococci (19.4%), Pseudomonas aeruginosa (8.4%), Staphylococcus aureus (7.1%), Klebsiella pneumoniae (5.8%) and Candida spp. (5.8%). Matching was successful for 109 cases. Compared to matched control subjects, cases were more frequently female, suffered more frequently from arthrosis, angina pectoris and pressure ulcers, had worse Activities of Daily Living-scores, had more often an intravenous or bladder catheter, and were more often bedridden. Logistic regression demonstrated presence of an intravenous catheter (odds ratio [OR] 7.5, 95% confidence interval [CI] 2.5-22.9) and being bedridden (OR 2.9, 95% CI 1.6-5.3) as independent risk factors for BSI. In univariate analysis nosocomial BSI was associated with increased mortality (22.0% vs. 11.0%; P=0.029). After adjustment for confounding co-variates, however, nosocomial BSI was not associated with mortality (hazard ratio 1.3, 95% CI 0.6-2.6). Being bedridden and increasing age were independent risk factors for death.

CONCLUSION

Intravenous catheters and being bedridden are the main risk factors for nosocomial BSI. Although associated with higher mortality, this infectious complication seems not to be an independent risk factor for death in geriatric patients.

Estimating the impact of healthcare-associated infections on length of stay and costs

Healthcare-associated infections (HAIs) unquestionably have substantial effects on morbidity and mortality. However, quantifying the exact economic burden attributable to HAIs still remains a challenging issue. Inaccurate estimations may arise from two major sources of bias. First, factors other than infection may affect patients' length of stay (LOS) and healthcare utilization. Second, HAI is a time-varying exposure, as the infection can impact on LOS and costs only after the infection has started. The most frequent mistake in previously published evidence is the introduction of time-dependent information as time-fixed, on the assumption that the impact of such exposure on the outcome was already present on admission. Longitudinal and multistate models avoid time-dependent bias and address the time-dependent complexity of the data. Appropriate statistical methods are important in analysis of excess costs and LOS associated with HAI, because informed decisions and policy developments may depend on them.

Estimating attributable mortality due to nosocomial infections acquired in intensive care units

BACKGROUND

The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken.

OBJECTIVE

To assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients.

SETTING

Eleven ICUs of a French university hospital.

DESIGN

We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was defined as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis.

RESULTS

Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%-14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection.

CONCLUSIONS

ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assessed.

Is Candida really a threat in the ICU?

PURPOSE OF REVIEW

The epidemiological and clinical relevance of Candida in the ICU is reviewed. Three issues were appraised. First is the prevalence of Candida. Second is the relevance of nonblood cultures positive for Candida and multisite colonization. Third is the importance of invasive candidiasis in terms of mortality.

RECENT FINDINGS

The diagnosis of invasive candidiasis remains problematic in nonblood cultures. Consequently, the true prevalence of invasive candidiasis is difficult to assess. Another result of the complicated diagnosis is the risk for delayed antifungal therapy in case of systemic Candida infection. Therefore, pre-emptive therapy has become increasingly popular in high-risk patients.

SUMMARY

Candida spp. cause a minority of nosocomial bloodstream infections ( approximately 4-9%). Yet, delayed initiation of appropriate antifungal therapy results in significant attributable mortality. Given the inability to efficiently discriminate colonization from invasive candidiasis, this is a problematic issue. The presence of Candida in tracheal aspirates, urine cultures or wound swabs frequently reflects colonization. Yet, multisite colonization frequently precedes systemic invasion. As such, multisite Candida colonization is a crucial element in the decision to start pre-emptive therapy. However, the predictive value of multisite colonization in the absence of an overt risk profile for invasive candidiasis appears to be low.

Prevention of catheter-related bloodstream infections

CRBSIs are expensive, prevalent, and often fatal complications. In the past few years, several preventive interventions have been applied with excellent results toward decreasing CRBSIs. Studies show that most CRBSIs are preventable; therefore, health care organizations should strive to substantially reduce if not eliminate them. In addition to being a measure of quality of care, reducing infections will soon be a bottom-line issue, given that the Centers for Medicare and Medicaid Services announced its decision to cease paying hospitals from October 2008 for some care necessitated by "preventable complications", including CRBSIs. Therefore, health care facilities that do not make the necessary adjustments to improve the quality of their patient care and avoid harm may be economically penalized. This article reviews the available evidence on and possible barriers to the widespread use of preventive strategies. The health care community has struggled to build a culture that can eliminate the barriers obstructing high-quality care. These new approaches must facilitate collaboration among caregivers. During the past few years, much effort has been dedicated to researching causes for inadequate patient care and executing interventions to improve processes of care; only now are projects beginning to focus on evaluating whether patients are safer. This article discusses the prevention of CRBSIs and shows that substantial reductions in the rate of these infections are possible. It is no longer acceptable for health care organizations to have the goal of being at the CDC mean for rate of infections; they should strive to substantially reduce or even eliminate them. Patients deserve no less.

Mortality associated with bloodstream infection after coronary artery bypass surgery

BACKGROUND

Mortality attributable to bloodstream infection (BSI) is still controversial. We studied the impact of BSI on mortality after coronary artery bypass surgery, including the specific impact of different etiologic organisms.

METHODS

Our cohort consisted of 4515 patients who underwent coronary artery bypass procedures at a university hospital from 1996 through 2004. We used Society of Thoracic Surgery data supplemented with laboratory and infection control data. Mortality dates were identified using Society of Thoracic Surgery data and the Social Security Death Index. BSI within 90 days after surgery was defined by a positive blood culture result. Cox proportional hazards and propensity score models were used to analyze the association between BSI and mortality.

RESULTS

Patients with BSI had a 4.2-fold increased risk of death (95% confidence interval [CI], 3.0-5.9) 2-90 days after coronary artery bypass surgery, compared with uninfected patients. The risk of death was higher among patients with BSI due to gram-negative bacteria (hazard ratio [HR], 6.8; 95% CI, 3.9-12.0) and BSI due to Staphylococcus aureus (HR, 7.2; 95% CI, 3.3-15.7) and lowest among patients with BSI caused by gram-positive bacteria other than S. aureus (HR, 2.2; 95% CI, 1.1-4.6). The risk of death was highest among patients who developed BSI but had the lowest likelihood of infection (HR, 10.0; 95% CI, 3.5-28.8) and was lowest among patients who developed BSI but had the highest likelihood of infection (HR, 2.3; 95% CI, 1.2-4.6).

CONCLUSIONS

BSIs due to gram-negative bacteria and BSIs due to S. aureus contributed significantly to mortality. Mortality attributable to BSI was highest among patients predicted to be least likely to develop infection and was lowest among severely ill patients who were most likely to develop infection. BSI appears to be an important contributor to death after coronary artery bypass surgery, particularly among the healthiest patients.

Hyperglycaemia upon onset of ICU-acquired bloodstream infection is associated with adverse outcome in a mixed ICU population

This study aimed to assess whether a relationship exists between hyperglycaemia and outcome in a mixed cohort of critically ill patients with nosocomial bloodstream infection (BSI), and to evaluate patterns of blood glucose levels between survivors and non-survivors. A historical observational cohort study was conducted in the intensive care unit (ICU) of a tertiary care referral centre. One-hundred-and-thirty patients with a microbiologically documented ICU-acquired BSI (period 2003 to 2004) were included. For the study, morning blood glucose levels were evaluated from one day prior until five days after onset of BSI. The contribution of hyperglycaemia, divided in three subgroups (> or = 150 mg/dl, > or = 175 mg/dl and > or = 200 mg/dl), to in-hospital mortality was estimated by logistic regression. In-hospital mortality was 36.2%. Over the seven study days, no differences were found in daily morning blood glucose levels between survivors (n = 83) and non-survivors (n = 47). Nevertheless, the trend of blood glucose levels upon onset of BSI showed a remarkable increase in the non-survivors, whereas it decreased in the survivors. Hyperglycaemia (> or = 175 mg/dl and > or = 200 mg/dl) was observed more often among the non-survivors. Multivariate logistic regression showed that APACHE II (P = 0.002), antibiotic resistance (P = 0.004) and hyperglycaemia (> or = 175 mg/dl) upon onset of BSI (P = 0.017) were independently associated with in-hospital mortality, whereas a history of diabetes (P = 0.041) was associated with better outcome. Hyperglycaemia (> or = 175 mg/dl) upon onset of ICU-acquired BSI is associated with worse outcome in a heterogeneous ICU population. Patterns of morning blood glucose levels have only limited value in the prediction of the individual course.

Impact of multiresistance of gram-negative bacteria in bloodstream infection on mortality rates and length of stay

BACKGROUND

Bloodstream infections (BSI) with gram-negative bacteria (GNB) are one of the most serious infections in the hospital setting, a situation compounded by the increasing antibiotic resistance of gram-negative bacteria causing BSI. The aim of the study was to assess the impact of antibiotic multiresistance of GNB in BSI on mortality rates and length of stay (LOS).

MATERIALS AND METHODS

The setting was the University Hospital Aachen, a 1,500-bed tertiary-care hospital with over 100 ICU beds providing maximal medical care in all disciplines. We performed a 5-year hospital-wide matched cohort study (January 1996 to February 2001) in which 71 cases and 99 controls were enrolled. Matching criteria were sex, age and GNB isolated in blood cultures. Multiresistance was defined as resistance against at least two different classes of antibiotics such as penicillins (+beta-lactamase-inhibitor), third-generation cephalosporins, fluoroquinolones or carbapenems.

RESULTS

BSI were mainly nosocomially acquired, and cases of BSI with multiresistant bacteria were associated with a higher mortality (p=0.0418) and a prolonged LOS in the intensive care unit (ICU) (p=0.0049). Risk factors for BSI with multiresistant GNB were antibiotic treatment (p=0.0191) and mechanical ventilation (p=0.0283).

CONCLUSION

Multiresistance of GNB causing BSI was associated with higher mortality rates and longer LOS in ICU. The initial antibiotic therapy was significantly more often inadequate and might have had an impact on overall mortality. Thus, an effective strategy to administer an appropriate initial empirical antibiotic therapy, especially in patients with risk factors, must be sought. Moreover, the overall usage of antimicrobials must be limited and infection control guidelines should be followed to reduce the emergence and transmission of multiresistant GNB.

Measuring the impact of multidrug resistance in nosocomial infection

PURPOSE OF REVIEW

The review examines potential confounders hampering measurement of the impact of multidrug resistance in nosocomial infections. Methodological techniques dealing with the problem of confounding are discussed and current findings in how multidrug resistance affects outcome in patients with nosocomial infection are highlighted.

RECENT FINDINGS

Outcome comparisons between patients infected with multidrug-resistant pathogens and patients infected with susceptible microorganisms are hampered by confounders such as differences in disease severity, prolonged hospitalization prior to onset of infection (exposure time), the causative pathogen, the type of infection, and the rate of appropriate empirical antimicrobial therapy. The confounding effect can be countered by means of either multivariable regression techniques or matched cohort studies, or a combination of both. Recent literature on the impact of multidrug resistance (methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase producing Enterobacteriaceae, etc) is conflicting and highly dependable on the way disturbing variables are accounted for.

SUMMARY

Recent data underscore that the impact of multidrug resistance on the outcome of nosocomial infection might differ depending on the study population, type of infection, type of pathogen and appropriateness of therapy, and hence, that any conclusion drawn prior to accurate accounting for imbalanced confounders is premature and potentially false.