Antibiotic pressure is a major risk factor for rectal colonization by multidrug-resistant Pseudomonas aeruginosa in critically ill patients

Is screening of patients for Pseudomonas aeruginosa groin/rectal carriage useful in identifying those at risk of bacteraemia in haematology and other high-risk clinical settings?

BACKGROUND

P. aeruginosa is a leading cause of healthcare-associated infections (HAIs) in patients exposed to hospital waters. A rising incidence of P. aeruginosa bacteraemia prompted microbiological screening at patient-admission to support early identification of acquisition.

MATERIALS/METHODS

A 41-bed haematology ward (800-bed teaching-hospital, London) was surveyed between 24/01/2020-13/05/2020. Concurrent rectal and groin swabs were collected in duplicate (two swabs at a time) upon admission weekly. Results were compared with historical shower, drain and tap water contamination data.

RESULTS

606 groin/rectal swabs were collected from 154 patients; 61 female (median age: 53years [IQR-42-66; range:13-82]) and 93 male (median: 57years [IQR-36-67; range:20-93]). Six of 154 patients admitted (3.9%) were positive for P. aeruginosa. Two patients (1.3% (CI=0.16-4.6%)) were colonised at admission while four patients (2.6% (CI=0.7-6.5%)) became colonised by 33 days (IQR:13-54) of stay. Concurrent duplicate sampling yielded both positive and negative results in all colonised patient-cases. One patient subsequently developed P. aeruginosa bacteraemia. Shower water and corresponding drains from the four patient rooms where P. aeruginosa was acquired were heavily contaminated (>300 CFU/100 mL) with P. aeruginosa 265 days (median; range:247-283) before patient admission. Point-of-use filtration devices were installed to affected outlets to prevent patient acquisition. However, HWB waters in corresponding rooms were free of P. aeruginosa contamination.

CONCLUSIONS

Rectal/groin swab-screening at admission to hospital might be valuable for early-detection of patient colonisation but is intrusive, resource-demanding and yield may be low. In high-risk settings, enhanced environmental-monitoring, decontamination of surfaces and drains, and point-of-use filter-barriers is recommended, especially if expected duration of stay exceeds 30 days.

Risk factors and clinical impact of multidrug resistance in healthcare-associated bacteremic urinary tract infections: a post-hoc analysis of a multicenter prospective cohort in Spain

INTRODUCTION

The global burden associated with antimicrobial resistance is of increasing concern. The aim of this study was to evaluate risk factors associated with multidrug-resistant (MDR) infection and its clinical impact in a cohort of patients with healthcare-associated (HCA) bacteremic urinary tract infections (BUTI).

METHODS

This is a post-hoc analysis a prospective multicenter study of patients with HCA-BUTI (ITUBRAS-2). The primary outcome was MDR profile. Secondary outcomes were clinical response (at 48-72h and at hospital discharge) and length of hospital stay from onset of BUTI. Logistic regression was used to evaluate variables associated with MDR profile and clinical response. Length of hospital stay was evaluated using multivariate median regression.

RESULTS

443 episodes were included, of which 271 (61.17%) were classified as expressing an MDR profile. In univariate analysis, MDR profile was associated with E. coli episodes (OR 3.13, 95% CI 2.11-4.69, p<0.001) and the extensively drug-resistant (XDR) pattern with P. aeruginosa etiology (OR 7.84, 95% CI 2.37-25.95; p=0.001). MDR was independently associated with prior use of fluoroquinolones (aOR 2.43; 95% CI 1.25-4.69), cephalosporins (aOR 2.14; 95% CI 1.35-3.41) and imipenem or meropenem (aOR 2.08; 95% CI 1.03-4.20) but not with prior ertapenem. In terms of outcomes, MDR profile was not associated with lower frequency of clinical cure, but with longer hospital stay.

CONCLUSIONS

MDR profile was independently associated with prior use of fluoroquinolones, cephalosporins, imipenem and meropenem, but not with prior ertapenem. MDR-BUTI episodes were not associated with worse clinical cure, although was independently associated with longer duration of hospital stay.

Gut colonization with multidrug resistant organisms in the intensive care unit: a systematic review and meta-analysis

BACKGROUND

Gut colonization with multidrug-resistant organisms (MDRO) frequently precedes infection among patients in the intensive care unit (ICU), although the dynamics of colonization are not completely understood. We performed a systematic review and meta-analysis of ICU studies which described the cumulative incidence and rates of MDRO gut acquisition.

METHODS

We systematically searched PubMed, Embase, and Web of Science for studies published from 2010 to 2023 reporting on gut acquisition of MDRO in the ICU. MDRO were defined as multidrug resistant non-Pseudomonas Gram-negative bacteria (NP-GN), Pseudomonas spp., and vancomycin-resistant Enterococcus (VRE). We included observational studies which obtained perianal or rectal swabs at ICU admission (within 48 h) and at one or more subsequent timepoints. Our primary outcome was the incidence rate of gut acquisition of MDRO, defined as any MDRO newly detected after ICU admission (i.e., not present at baseline) for all patient-time at risk. The study was registered with PROSPERO, CRD42023481569.

RESULTS

Of 482 studies initially identified, 14 studies with 37,305 patients met criteria for inclusion. The pooled incidence of gut acquisition of MDRO during ICU hospitalization was 5% (range: 1-43%) with a pooled incidence rate of 12.2 (95% CI 8.1-18.6) per 1000 patient-days. Median time to acquisition ranged from 4 to 26 days after ICU admission. Results were similar for NP-GN and Pseudomonas spp., with insufficient data to assess VRE. Among six studies which provided sufficient data to perform curve fitting, there was a quasi-linear increase in gut MDRO colonization of 1.41% per day which was stable through 30 days of ICU hospitalization (R2 = 0.50, p < 0.01).

CONCLUSIONS

Acquisition of gut MDRO was common in the ICU and increases with days spent in ICU through 30 days of follow-up. These data may guide future interventions seeking to prevent gut acquisition of MDRO in the ICU.

Extensively drug-resistant Pseudomonas aeruginosa: clinical features and treatment with ceftazidime/avibactam and ceftolozane/tazobactam in a tertiary care university hospital center in Portugal - A cross-sectional and retrospective observational study

Introduction

Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) is a growing concern due to its increasing incidence, limited therapeutic options, limited data on the optimal treatment, and high mortality rates. The study aimed to characterize the population, the outcome and the microbiological characteristics of XDR-PA identified in a Portuguese university hospital center.

Methods

All XDR-PA isolates between January 2019 and December 2021 were identified. XDR-PA was defined as resistance to piperacillin-tazobactam, third and fourth generation cephalosporins, carbapenems, aminoglycosides and fluoroquinolones. A retrospective analysis of the medical records was performed.

Results

One hundred seventy-eight individual episodes among 130 patients with XDR-PA detection were identified. The most common sources of infection were respiratory (32%) and urinary tracts (30%), although skin and soft tissue infections (18%) and primary bacteremia (14%) were also prevalent. Colonization was admitted in 64 cases. Several patients had risk factors for complicated infections, most notably immunosuppression, structural lung abnormalities, major surgery, hemodialysis or foreign intravascular or urinary devices. XDR-PA identification was more frequent in male patients with an average age of 64.3 ± 17.5 years. One non-susceptibility to colistin was reported. Only 12.4% were susceptible to aztreonam. Ceftazidime-avibactam (CZA) was susceptible in 71.5% of the tested isolates. Ceftolozane-tazobactam (C/T) was susceptible in 77.5% of the tested isolates. Antibiotic regimens with XDR-PA coverage were reserved for patients with declared infection, except to cystic fibrosis. The most frequently administered antibiotics were colistin (41 cases), CZA (39 cases), and C/T (16 cases). When combination therapy was used, CZA plus colistin was preferred. The global mortality rate among infected patients was 35.1%, significantly higher in those with hematologic malignancy (50.0%, p < 0.05), followed by the ones with bacteremia (44.4%, p < 0.05) and those medicated with colistin (39.0%, p < 0.05), especially the ones with respiratory infections (60.0%). Among patients treated with CZA or C/T, the mortality rate seemed to be lower.

Discussion

XDR-PA infections can be severe and difficult to treat, with a high mortality rate. Even though colistin seems to be a viable option, it is likely less safe and efficient than CZA and C/T. To the best of the authors' knowledge, this is the first description of the clinical infection characteristics and treatment of XDR-PA in Portugal.

Impact of antibiotic exposure on antibiotic-resistant Acinetobacter baumannii isolation in intensive care unit patients: a systematic review and meta-analysis

BACKGROUND

Acinetobacter baumannii (AB) poses a significant threat to critically ill patients in intensive care units (ICUs). Although an association between antibiotic exposure and resistant AB is reported in the literature, a synthesis of evidence in ICU patients is still lacking.

AIM

To summarize the evidence on the association between prior antibiotic exposure and the occurrence of resistant AB in ICU patients.

METHODS

Online databases were searched for cohort and case-control studies providing data on the association of interest. Carbapenem/multidrug-resistant AB isolation was compared with non-isolation; carbapenem/multidrug-resistant AB was compared with carbapenem/antibiotic-susceptible AB; and extensively drug-resistant AB isolation was compared with non-isolation. Each comparison was subjected to a restricted maximum likelihood random-effects meta-analysis per antibiotic class, estimating pooled ORs. Stratified meta-analyses were performed by study design, outcome type and association-measure adjustment.

FINDINGS

Overall, 25 high-quality studies were retrieved. Meta-analyses showed that carbapenem/multidrug-resistant AB isolation was associated with previous exposure to aminoglycosides, carbapenems, third-generation cephalosporines, glycylcyclines, and nitroimidazoles. Increased risk of isolation of carbapenem/multidrug-resistant AB isolation vs carbapenem/antibiotic-susceptible AB was shown for prior exposure to aminoglycosides, antipseudomonal penicillins, carbapenems, fluoroquinolones, glycopeptides, and penicillins. Third-generation cephalosporin exposure increased the risk of extensively drug-resistant AB isolation vs non-isolation.

CONCLUSION

This systematic review clarifies the role of antibiotic use in antibiotic-resistant AB spread in ICUs, although for some antibiotic classes the evidence is still uncertain due to the small number of adjusted analyses, methodological and reporting issues, and limited number of studies. Future studies need to be carried out with standardized methods and appropriate reporting of multivariable models.

Age of Antibiotic Resistance in MDR/XDR Clinical Pathogen of Pseudomonas aeruginosa

Antibiotic resistance in Pseudomonas aeruginosa remains one of the most challenging phenomena of everyday medical science. The universal spread of high-risk clones of multidrug-resistant/extensively drug-resistant (MDR/XDR) clinical P. aeruginosa has become a public health threat. The P. aeruginosa bacteria exhibits remarkable genome plasticity that utilizes highly acquired and intrinsic resistance mechanisms to counter most antibiotic challenges. In addition, the adaptive antibiotic resistance of P. aeruginosa, including biofilm-mediated resistance and the formation of multidrug-tolerant persisted cells, are accountable for recalcitrance and relapse of infections. We highlighted the AMR mechanism considering the most common pathogen P. aeruginosa, its clinical impact, epidemiology, and save our souls (SOS)-mediated resistance. We further discussed the current therapeutic options against MDR/XDR P. aeruginosa infections, and described those treatment options in clinical practice. Finally, other therapeutic strategies, such as bacteriophage-based therapy and antimicrobial peptides, were described with clinical relevance.

Gut to lung translocation and antibiotic mediated selection shape the dynamics of Pseudomonas aeruginosa in an ICU patient

Bacteria have the potential to translocate between sites in the human body, but the dynamics and consequences of within-host bacterial migration remain poorly understood. Here we investigate the link between gut and lung Pseudomonas aeruginosa populations in an intensively sampled ICU patient using a combination of genomics, isolate phenotyping, host immunity profiling, and clinical data. Crucially, we show that lung colonization in the ICU was driven by the translocation of P. aeruginosa from the gut. Meropenem treatment for a suspected urinary tract infection selected for elevated resistance in both the gut and lung. However, resistance was driven by parallel evolution in the gut and lung coupled with organ specific selective pressures, and translocation had only a minor impact on AMR. These findings suggest that reducing intestinal colonization of Pseudomonas may be an effective way to prevent lung infections in critically ill patients.

Pseudomonas aeruginosa Infections in Cancer Patients

Pseudomonas aeruginosa (P. aeruginosa) is one of the most frequent opportunistic microorganisms causing infections in oncological patients, especially those with neutropenia. Through its ability to adapt to difficult environmental conditions and high intrinsic resistance to antibiotics, it successfully adapts and survives in the hospital environment, causing sporadic infections and outbreaks. It produces a variety of virulence factors that damage host cells, evade host immune responses, and permit colonization and infections of hospitalized patients, who usually develop blood stream, respiratory, urinary tract and skin infections. The wide intrinsic and the increasing acquired resistance of P. aeruginosa to antibiotics make the treatment of infections caused by this microorganism a growing challenge. Although novel antibiotics expand the arsenal of antipseudomonal drugs, they do not show activity against all strains, e.g., MBL (metalo-β-lactamase) producers. Moreover, resistance to novel antibiotics has already emerged. Consequently, preventive methods such as limiting the transmission of resistant strains, active surveillance screening for MDR (multidrug-resistant) strains colonization, microbiological diagnostics, antimicrobial stewardship and antibiotic prophylaxis are of particular importance in cancer patients. Unfortunately, surveillance screening in the case of P. aeruginosa is not highly effective, and a fluoroquinolone prophylaxis in the era of increasing resistance to antibiotics is controversial.

High prevalence of Pseudomonas aeruginosa carriage in residents of French and German long-term care facilities

OBJECTIVES

To determine prevalence, incidence, and factors associated with Pseudomonas aeruginosa (PA) intestinal carriage in residents of long-term care facilities (LTCFs) and to understand the population structure of this pathogen in LTCFs from two European countries.

METHODS

We assessed the prevalence of PA intestinal carriage and the incidence of acquisition by collecting fecal samples from 403 residents of 20 LTCFs. We collected 289 environmental samples from sinks and drinking water. Factors associated with carriage and acquisition of intestinal PA were identified. All PA isolates had their antibiotic phenotypic resistance profile determined and their genome sequenced, from which we assessed the population structure of the collection and identified resistance determinants.

RESULTS

We found a high proportion of residents with PA intestinal carriage (51.6%) over the entire study period. Over the follow-up period, 28.6% of the residents acquired intestinal PA. Older age (Odds ratio [OR] = 1.29, 95% confidence interval [CI]: 1.09-1.52; p = 0.002), urinary incontinence (OR = 2.56, 95% CI: 1.37-4.88; p = 0.003), and male gender (OR = 2.55), 95% CI: 1.05-6.18; p = 0.039) were associated with higher probability of carriage. Wheelchair usage (OR = 4.56, 95% CI: 1.38-15.05; p = 0.013) and a body mass index >25 (OR = 3.71, 95% CI: 1.17-11.82; p = 0.026) were associated with higher risk of PA acquisition. Population structure of our isolates was mainly non-clonal with 112 different STs among the 241 isolates. Most represented STs were high risk clones ST253 (n=26), ST17 (n=11), ST244 (n=11), ST309 (n=10), and ST395 (n=10). Most PA isolates (86.3%) were susceptible to antibiotics, with no acquired genes conferring resistance to antipseudomonal agents.

CONCLUSIONS

We found an unexpected high prevalence of PA intestinal carriage in LTCF residents mainly associated with individual-level factors. Our study revealed a polyclonal PA population structure suggesting that individual acquisition is more frequent than resident-to-resident transmission.

Rectal colonization by resistant bacteria increases the risk of infection by the colonizing strain in critically ill patients with cirrhosis

BACKGROUND & AIMS

It remains unclear whether rectal colonization with multidrug-resistant organisms (MDROs) is prevalent and predisposes to infections by the same pathogens in patients with cirrhosis.

METHODS

Two series of critically ill patients were evaluated. In the Barcelona cohort, 486 consecutive patients were prospectively evaluated, 129 with and 357 without cirrhosis (2015-2016). Rectal swabs were performed at admission and weekly thereafter (until intensive care unit [ICU] discharge) to detect MDRO colonization. Risk factors for colonization and infection by MDROs were evaluated. A retrospective cohort from Frankfurt (421 patients with cirrhosis; 2010-2018) was investigated to evaluate MDRO rectal colonization in another epidemiological scenario.

RESULTS

In the Barcelona cohort, 159 patients were colonized by MDROs (32.7%), 102 (64.2%) at admission and 57 (35.8%) during follow-up. Patients with cirrhosis showed higher rates of rectal colonization at admission than those without cirrhosis (28.7% vs. 18.2%, p = 0.01) but similar colonization rates during ICU stay. Extended-spectrum beta-lactamase-Enterobacterales were the most frequent MDROs isolated in both groups. Colonization by MDROs independently increased the risk of infection by MDROs at admission and during follow-up. Risk of new infection by the colonizing strain was also significantly increased in patients with (hazard ratio [HR] 7.41) and without (HR 5.65) cirrhosis. Rectal colonization by MDROs was also highly prevalent in Frankfurt (n = 198; 47%; 131 at admission [66.2%] and 67 [33.8%] during follow-up), with vancomycin-resistant enterococci being the most frequent colonizing organism. Rectal colonization by MDROs was also associated with an increased risk of infection by MDROs in this cohort. Infections occurring in MDR carriers were mainly caused by the colonizing strain.

CONCLUSION

Rectal colonization by MDROs is extremely frequent in critically ill patients with cirrhosis. Colonization increases the risk of infection by the colonizing resistant strain.

LAY SUMMARY

Rectal colonization by multidrug-resistant organisms (MDROs) is a prevalent problem in patients with cirrhosis requiring critical care. The pattern of colonizing bacteria is heterogeneous with relevant differences between centers. Colonization by MDROs is associated with increased risk of infection by the colonizing bacteria in the short term. This finding suggests that colonization data could be used to guide empirical antibiotic therapy and de-escalation policies in patients with cirrhosis.

Risk Factors for Multidrug-Resistant Gram-Negative Bacteria Carriage upon Admission to the Intensive Care Unit

Multidrug-resistant Gram-negative bacteria (MDR-GNB) are microorganisms that have acquired resistance to extended-spectrum antibacterials and constitute an emerging threat to public health. Although carriers are an important source of transmission in healthcare settings, data about risk factors for MDR-GNB carriage are limited. Therefore, we aimed to identify risk factors for MDR-GNB carriage upon intensive care unit (ICU) admission and to optimise screening strategies. We conducted a case–control study. Admissions of adult patients to the ICU of a 1000-bed hospital during a year were included. We collected sociodemographic, clinical and microbiological data and performed a multivariate logistic regression model. A total of 1342 patients resulted in 1476 episodes of ICU admission, 91 (6.2%) of whom harboured MDR-GNB (38.5% women; median age 63.9 years). The most frequently isolated pathogens were Escherichia coli (57%) and Klebsiella pneumoniae (16%). The most frequent resistance mechanism was production of extended-spectrum beta lactamases. MDR-GNB carriage was associated to liver cirrhosis (OR 6.54, 95% CI 2.17–19.17), previous MDR-GNB carriage (OR 5.34, 1.55–16.60), digestive surgery (OR 2.83, 1.29–5.89) and length of hospital stay (OR 1.01 per day, 1.00–1.03). Several risk factors for MDR-GNB carriage upon admission to a high-risk setting were identified; the main comorbidity was liver cirrhosis.

A Large Multicenter Prospective Study of Community-Onset Healthcare Associated Bacteremic Urinary Tract Infections in the Era of Multidrug Resistance: Even Worse than Hospital Acquired Infections?

INTRODUCTION

Healthcare-associated (HCA) infections represent a growing public health problem. The aim of this study was to compare community-onset healthcare associated (CO-HCA) bacteremic urinary tract infections (BUTI) and hospital-acquired (HA)-BUTI with special focus on multidrug resistances (MDR) and outcomes.

METHODS

ITUBRAS-project is a prospective multicenter cohort study of patients with HCA-BUTI. All consecutive hospitalized adult patients with CO-HCA-BUTI or HA-BUTI episode were included in the study. Exclusion criteria were: patients < 18 years old, non-hospitalized patients, bacteremia from another source or primary bacteremia, non-healthcare-related infections and infections caused by unusual pathogens of the urinary tract. The main outcome variable was 30-day all-cause mortality with day 1 as the first day of positive blood culture. Logistic regression was used to analyze factors associated with clinical cure at hospital discharge and with receiving inappropriate initial antibiotic treatment. Cox regression was used to evaluate 30-day all-cause mortality.

RESULTS

Four hundred forty-three episodes were included, 223 CO-HCA-BUTI. Patients with CO-HCA-BUTI were older (p < 0.001) and had more underlying diseases (p = 0.029) than those with HA-BUTI. The severity of the acute illness (Pitt score) was also higher in CO-HCA-BUTI (p = 0.026). Overall, a very high rate of MDR profiles (271/443, 61.2%) was observed, with no statistical differences between groups. In multivariable analysis, inadequate empirical treatment was associated with MDR profile (aOR 3.35; 95% CI 1.77-6.35), Pseudomonas aeruginosa (aOR 2.86; 95% CI 1.27-6.44) and Charlson index (aOR 1.11; 95% CI 1.01-1.23). Mortality was not associated with the site of acquisition of the infection or the presence of MDR profile. However, in the logistic regression analyses patients with CO-HCA-BUTI (aOR 0.61; 95% CI 0.40-0.93) were less likely to present clinical cure.

CONCLUSION

The rate of MDR infections was worryingly high in our study. No differences in MDR rates were found between CO-HCA-BUTI and HA-BUTI, in the probability of receiving inappropriate empirical treatment or in 30-day mortality. However, CO-HCA-BUTIs were associated with worse clinical cure.

Screening for Antimicrobial-Resistant Gram-negative bacteria in hospitalised patients, and risk of progression from colonisation to infection: Systematic review

BACKGROUND

Transmission of antimicrobial-resistant Gram-negative bacteria (AMR-GNB) among hospitalised patients can lead to new cases of carriage, infection and outbreaks, hence the need for early carrier identification. We aim to explore two key elements that may guide control policies for colonisation/infection in hospital settings: screening practices on admission to hospital wards and risk of developing infection from colonisation.

METHODS

We searched on PubMed, Scopus and Cochrane databases for studies published from 2010 up to 2021 reporting on adult patients hospitalised in high-income countries.

RESULTS

The search retrieved 11853 articles. After screening, 100 studies were included. Combining target patient groups and setting type, we identified six screening approaches. The most reported approach was all admitted patients to high-risk (HR) wards (49.4%). The overall prevalence of AMR-GNB was 13.8% (95%CI 9.3-19.0) with significant differences across regions and time. Risk of progression to infection among colonised patients was 11.0% (95%CI 8.0-14.3) and varied according to setting and pathogens' group (p value<0.0001), with higher values reported for Klebsiella species (18.1%; 95%CI 8.9-29.3).

CONCLUSIONS

While providing a comprehensive overview of the screening approaches, our study underlines the considerable burden of AMR-GNB colonisation and risk of progression to infection in hospitals by pathogen, setting and time.

Acquisition of MDR-GNB in hospital settings: a systematic review and meta-analysis focusing on ESBL-E

INTRODUCTION

Extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-E) and other multi-drug-resistant Gram-negative bacteria (MDR-GNB) have disseminated globally since their discovery in the late 20^th century. Various infection prevention and control measures are in place to prevent nosocomial transmission of these organisms, but their efficacy remains disputed. New literature has emerged in recent years providing further evidence which can be used to formulate effective strategies to tackle this issue in the future.

METHODS

A systematic review was performed to characterize the prevalence of colonization of multi-drug-resistant organisms and subsequent acquisition of these organisms within hospital settings. A meta-analysis was performed to characterize the prevalence and acquisition of ESBL-E in Europe and North America.

RESULTS

Twenty-eight studies fulfilled the inclusion criteria. Escherichia coli formed the main burden of MDR-GNB colonization worldwide. Patient-to-patient transmission of ESBL-E was found to be rare, but increased transmissibility of Klebsiella pneumoniae was described over E. coli. Within European and North American healthcare settings, a meta-analysis of eight studies identified a pooled prevalence of ESBL-E on admission to hospital of 7.91% and an acquisition rate of 3.73%.

DISCUSSION

Low prevalence at the point of hospital admission and insufficient evidence of patient-to-patient transmission suggests that infection prevention and control measures such as universal surveillance screening and single-room isolation are unlikely to be practical or effective interventions in reducing the overall burden of ESBL-E in hospitals, in line with current European guidelines. Instead, it is argued that efforts should be placed on controlling the spread of these organisms and other MDR-GNB in the community, predominantly long-term care facilities.

Approach to the Treatment of Patients with Serious Multidrug-Resistant Pseudomonas aeruginosa Infections

Multidrug resistance(MDR) among Pseudomonas aeruginosa (PSA) isolates presents a significant clinical challenge and can substantially complicate the approach to selection of optimal antibiotic therapy. This review addresses major considerations in antibiotic selection for patients with suspected or documented serious MDR-PSA infections. Common mechanisms contributing to MDR among clinical PSA isolates are summarized. Empiric and definitive therapy considerations are addressed including the potential role of combination therapy. Newer agents with in vitro activity against MDR-PSA (e.g., ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, and cefiderocol) and their potential roles in clinical settings are discussed. Although these newer agents are promising options for the treatment of MDR-PSA, clinical data remain generally limited. Future studies are needed to determine optimal agents for the empiric and definitive treatment of MDR-PSA.

Altering Routine Intensive Care Unit Practices to Support Commensalism

The gastrointestinal (GI) tract consists of trillions of organisms that support multiple functions in the body, from immunity, digestion, and absorption to drug metabolism. These microbes form an overall collection of microorganisms that form the body's microbiome. In critical illness, many of these functions are aberrant, and the microbiome is altered, leading to untoward effects. Some of the most common medications received by patients include antibiotics and proton pump inhibitors, which affect particular changes in the microbiome. In addition, patients receiving prolonged enteral and parenteral nutrition experience changes in the microbiological composition and diversity of their GI tracts. Research is ongoing to characterize the crosstalk between the microbiome and immune function as targets for drug and nutrition therapy.

Epidemiology and Treatment of Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa Infections

In recent years, the worldwide spread of the so-called high-risk clones of multidrug-resistant or extensively drug-resistant (MDR/XDR) Pseudomonas aeruginosa has become a public health threat. This article reviews their mechanisms of resistance, epidemiology, and clinical impact and current and upcoming therapeutic options. In vitro and in vivo treatment studies and pharmacokinetic and pharmacodynamic (PK/PD) models are discussed. Polymyxins are reviewed as an important therapeutic option, outlining dosage, pharmacokinetics and pharmacodynamics, and their clinical efficacy against MDR/XDR P. aeruginosa infections. Their narrow therapeutic window and potential for combination therapy are also discussed. Other "old" antimicrobials, such as certain β-lactams, aminoglycosides, and fosfomycin, are reviewed here. New antipseudomonals, as well as those in the pipeline, are also reviewed. Ceftolozane-tazobactam has clinical activity against a significant percentage of MDR/XDR P. aeruginosa strains, and its microbiological and clinical data, as well as recommendations for improving its use against these bacteria, are described, as are those for ceftazidime-avibactam, which has better activity against MDR/XDR P. aeruginosa, especially strains with certain specific mechanisms of resistance. A section is devoted to reviewing upcoming active drugs such as imipenem-relebactam, cefepime-zidebactam, cefiderocol, and murepavadin. Finally, other therapeutic strategies, such as use of vaccines, antibodies, bacteriocins, anti-quorum sensing, and bacteriophages, are described as future options.

Risk factors and the resistance mechanisms involved in Pseudomonas aeruginosa mutation in critically ill patients

Background

The objective of this study was to determine the main risk factors of Pseudomonas aeruginosa mutation as well as the mechanisms of acquired resistance.

Methods

We conducted a 2-year prospective study in patients who were carriers of a Pseudomonas aeruginosa strain and who had been admitted to a medical/surgical ICU.

Results

Of the 153 patients who were included, 34 had a mutation in their strain. In a multivariate analysis, a duration of ventilation > 24 days was a risk factor for mutation (risk ratio 4.29; CI 95% 1.94-9.49) while initial resistance was a protective factor (RR 0.36; CI 95% 0.18-0.71). In a univariate analysis, exposure of P. aeruginosa to ceftazidime was associated with an over-production of AmpC cephalosporinase and exposure to meropenem was associated with impermeability. A segmentation method based on the duration of ventilation (> 24 days), initial resistance, and exposure of strains to ceftazidime made it possible to predict at 83% the occurrence of mutation.

Conclusion

The duration of ventilation and the presence of resistance as soon as P. aeruginosa is identified are predictive factors of mutation in ICU patients.

Antibiotics with activity against intestinal anaerobes and the hazard of acquired colonization with ceftriaxone-resistant Gram-negative pathogens in ICU patients: a propensity score-based analysis

Background

Intestinal colonization resistance is mainly exerted by commensal anaerobes.

Objectives

To assess whether exposure to non-carbapenem antibiotics with activity against intestinal anaerobes (namely, piperacillin/tazobactam, amoxicillin/clavulanate and metronidazole) may promote the acquisition of gut colonization with ceftriaxone-resistant Gram-negative bacteria (CFR-GNB) in ICU patients.

Patients and methods

All patients with a first stay >3 days in a single surgical ICU over a 30 month period were retrospectively included. Rectal carriage of CFR-GNB (i.e. ESBL-producing Enterobacteriaceae, AmpC-hyperproducing Enterobacteriaceae, Pseudomonas aeruginosa, Stenotrophomonas maltophilia and CFR Acinetobacter baumannii) was routinely screened for at admission then weekly. The impact of anti-anaerobe antibiotics was investigated in propensity score (PS)-matched cohorts of patients exposed and not exposed to these drugs and through PS-based inverse probability of treatment weighting on the whole study cohort, treating in-ICU death or discharge as competing risks for CFR-GNB acquisition.

Results

Among the 352 included patients [median ICU stay 16 (9–30) days, in-ICU mortality 12.2%], 120 (34.1%) acquired one or more CFR-GNB, mostly AmpC-hyperproducing Enterobacteriaceae (17.6%) and P. aeruginosa (14.8%). Exposure to anti-anaerobe antibiotics was the main predictor of CFR-GNB acquisition in both the PS-matched cohorts [adjusted HR (aHR) 3.92, 95% CI 1.12–13.7, P = 0.03] and the whole study cohort (aHR 4.30, 95% CI 1.46–12.63, P = 0.01). Exposure to other antimicrobials—especially ceftriaxone and imipenem/meropenem—exerted no independent impact on the likelihood of CFR-GNB acquisition.

Conclusions

Exposure to non-carbapenem antibiotics with activity against intestinal anaerobes may predispose to CFR-GNB acquisition in ICU patients. Restricting the use of these drugs appears to be an antibiotic stewardship opportunity.

Multicentre randomised controlled trial to investigate usefulness of the rapid diagnostic βLACTA test performed directly on bacterial cell pellets from respiratory, urinary or blood samples for the early de-escalation of carbapenems in septic intensive care unit patients: the BLUE-CarbA protocol

INTRODUCTION

The dramatic increase of the incidence of infections caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) has led to an increase of 50% of carbapenem consumption all around Europe in only 5 years. This favours the spread of carbapenem-resistant Gram-negative bacilli (GNB), causing life-threatening infections. In order to limit use of carbapenems for infections actually due to ESBL-PE, health authorities promote the use of rapid diagnostic tests of bacterial resistance. The objective of this work conducted in the intensive care unit (ICU) is to determine whether an early de-escalation of empirical carbapenems guided by the result of the βLACTA test is not inferior to the reference strategy of de-escalating carbapenems after the antibiogram result has been rendered.

METHODS AND ANALYSIS

This multicentre randomised controlled open-label non-inferiority clinical trial will include patients suffering from respiratory and/or urinary and/or bloodstream infections documented with GNB on direct examination and empirically treated with carbapenems. Empirical carbapenems will be adapted before the second dose depending on the results of the βLACTA test performed directly on the microbiological sample (intervention group) or after 48-72 hours depending on the definite antibiogram (control group). The primary outcome will combine 90-day mortality and percentage of infection recurrence during the ICU stay. The secondary outcomes will include the number of carbapenems defined daily doses and carbapenem-free days after inclusion, the proportion of new infections during ICU stay, new colonisation of patients' digestive tractus with multidrug-resistant GNB, ICU and hospital length of stay and cost-effectiveness ratio.

ETHICS AND DISSEMINATION

This protocol has been approved by the ethics committee of Paris-Ile-de-France IV, and will be carried out according to the principles of the Declaration of Helsinki and the Good Clinical Practice guidelines. The results of this study will be disseminated through presentation at scientific conferences and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03147807.

Influence of antibiotic pressure on multi-drug resistant Klebsiella pneumoniae colonisation in critically ill patients

Background

The aim of this study is to evaluate the risk factors for colonisation by multidrug resistant (MDR) K. pneumoniae in a critical care unit and the relationship between colonisation and the antibiotic pressure exerted by the antimicrobial treatments received by patients.

Methods

A prospective observational was designed. Patients admitted for more than 48 h to an intensive care unit were included. Samples for surveillance cultures were obtained from all the patients upon admission and once a week. The association between risk factors and colonisation by MDR K. pneumoniae was determined by logistic regression. A Cox regression model was used to evaluate the effect of the use of antimicrobials on the colonisation rate. An ARMIA model was used to investigate the association between the incidence of colonisation by MDR strains and the global consumption of antimicrobials in the unit.

Results

One thousand seven hundred twenty-five patients were included, from which 308 (17.9%) were positive for MDR K. pneumoniae. In the multivariate analysis, hospitalisation for longer than 7 days together with respiratory infection and administration of any antibiotic was associated with increased MR K. pneumoniae colonisation. Patients who received antibiotics for more than 48 h were colonised earlier than patients who did not receive antibiotic treatment [HR: 2.16 (95%CI:1.55–3.03)]. The ARIMA model found a significant association between the monthly colonisation rate for MR K. pneumoniae and the consumption of cephalosporins and carbapenems in the previous month.

Conclusion

Individual antibiotic administration and the global antibiotic pressure of cephalosporins and carbapenems are associated to an increased colonisation by MDR K. pneumoniae strains.

Multidrug resistant Pseudomonas aeruginosa in Estonian hospitals

Background

We aimed to identify the main spreading clones, describe the resistance mechanisms associated with carbapenem- and/or multidrug-resistant P. aeruginosa and characterize patients at risk of acquiring these strains in Estonian hospitals.

Methods

Ninety-two non-duplicated carbapenem- and/or multidrug-resistant P. aeruginosa strains were collected between 27th March 2012 and 30th April 2013. Clinical data of the patients was obtained retrospectively from the medical charts. Clonal relationships of the strains were determined by whole genome sequencing and analyzed by multi-locus sequence typing. The presence of resistance genes and beta-lactamases and their origin was determined. Combined-disk method and PCR was used to evaluate carbapenemase and metallo-beta-lactamase production.

Results

Forty-three strains were carbapenem-resistant, 11 were multidrug-resistant and 38 were both carbapenem- and multidrug-resistant. Most strains (54%) were isolated from respiratory secretions and caused an infection (74%). Over half of the patients (57%) were ≥ 65 years old and 85% had ≥1 co-morbidity; 96% had contacts with healthcare and/or had received antimicrobial treatment in the previous 90 days.

Clinically relevant beta-lactamases (OXA-101, OXA-2 and GES-5) were found in 12% of strains, 27% of which were located in plasmids. No Ambler class B beta-lactamases were detected. Aminoglycoside modifying enzymes were found in 15% of the strains. OprD was defective in 13% of the strains (all with CR phenotype); carbapenem resistance triggering mutations (F170 L, W277X, S403P) were present in 29% of the strains. Ciprofloxacin resistance correlated well with mutations in topoisomerase genes gyrA (T83I, D87N) and parC (S87 L). Almost all strains (97%) with these mutations showed ciprofloxacin-resistant phenotype.

Multi-locus sequence type analysis indicated high diversity at the strain level – 36 different sequence types being detected. Two sequence types (ST108 (n = 23) and ST260 (n = 18)) predominated. Whereas ST108 was associated with localized spread in one hospital and mostly carbapenem-resistant phenotype, ST260 strains occurred in all hospitals, mostly with multi-resistant phenotype and carried different resistance genotype/machinery.

Conclusions

Diverse spread of local rather than international P. aeruginosa strains harboring multiple chromosomal mutations, but not plasmid-mediated Ambler class B beta-lactamases, were found in Estonian hospitals.

Trial registration

This trial was registered retrospectively in ClinicalTrials.gov (NCT03343119).

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3421-1) contains supplementary material, which is available to authorized users.

Carbapenems and alternative β-lactams for the treatment of infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae: What impact on intestinal colonisation resistance?

The ongoing pandemic of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is responsible for a global rise in carbapenem consumption that may hasten the dissemination of carbapenemase-producing Enterobacteriaceae (CPE). Hence, carbapenem sparing through the use of alternative β-lactams is increasingly considered as a potential option in patients with ESBL-E infections. However, at the individual level, this strategy implies an in-depth understanding of how carbapenems and their alternatives impair the gut microbiota, especially the anaerobic bacteria and the colonisation resistance (CR) that it confers. In this review, we sought to appraise the impact of carbapenems and their main alternatives for ESBL-E infections (namely β-lactam/β-lactamase inhibitor combinations, cephamycins and temocillin) on the gut ecosystem and the resulting hazard for acquisition of CPE. Although limited, the available evidence challenges our perception of the ecological side effects of these antimicrobials and highlights knowledge gaps regarding antibiotic-induced alterations in intestinal CR. These alterations may depend not only on anti-anaerobic properties but also on a panel of parameters with marked interindividual variability, such as baseline characteristics of the gut microbiota or the degree of biliary excretion for the considered drug. In the current context of ESBL-E dissemination and increasing opportunities for carbapenem-sparing initiatives, large, comparative, high-quality studies based on new-generation sequencing tools are more than ever warranted to better define the positioning of alternative β-lactams in antimicrobial stewardship programmes.

A prospective surveillance study for multidrug-resistant bacteria colonization in hospitalized patients at a Thai University Hospital

Background

Colonization with multidrug-resistant (MDR) bacteria is a major risk factor for developing subsequent MDR infections.

Methods

We performed a prospective surveillance study in hospitalized patients at Siriraj Hospital. Nasal cavity, throat, inguinal area and rectal swabs were obtained within the first 48-h after admission, on day-5 after hospitalization and then every 7 days until discharge. Target bacteria included extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL), carbapenem-resistant-P.aeruginosa (CR-PA), carbapenem-resistant-A.baumannii (CR-AB) and methicillin-resistant S.aureus (MRSA).

Results

From January 2013–December 2014, 487 patients were enrolled. The baseline prevalence of colonization by ESBL, CR-PA, CR-AB and MRSA at any site was 52.2%, 6.8%, 4.7% and 7.2%, respectively. After 3-week of hospitalization, the prevalence of colonization by ESBL, CR-PA, CR-AB and MRSA increased to 71.7%, 47.2%, 18.9% and 18.9%, respectively. Multivariable analysis revealed that diabetes mellitus and recent cephalosporin exposure were the independent risk factors for baseline colonization by ESBL. The independent risk factors for CR-AB and/or CR-PA colonization were cerebrovascular diseases, previous hospitalization, transfer from another hospital/a LTCF and previous nasogastric tube use, whereas those for MRSA colonization were previous fluoroquinolone exposure and previous nasogastric tube use.

Conclusions

The baseline prevalence of colonization by ESBL was relatively high, whereas the baseline prevalence of colonization by CR-PA, CR-AB and MRSA was comparable to previous studies. There was an increasing trend in MDR bacteria colonization after hospitalization.

Poultry and beef meat as potential seedbeds for antimicrobial resistant enterotoxigenic Bacillus species: a materializing epidemiological and potential severe health hazard

Although Bacillus cereus is of particular concern in food safety and public health, the role of other Bacillus species was overlooked. Therefore, we investigated the presence of eight enterotoxigenic genes, a hemolytic gene and phenotypic antibiotic resistance profiles of Bacillus species in retail meat samples. From 255 samples, 124 Bacillus isolates were recovered, 27 belonged to B. cereus and 97 were non-B. cereus species. Interestingly, the non-B. cereus isolates carried the virulence genes and exhibited phenotypic virulence characteristics as the B. cereus. However, correlation matrix analysis revealed the B. cereus group positively correlates with the presence of the genes hblA, hblC, and plc, and the detection of hemolysis (p < 0.05), while the other Bacillus sp. groups are negatively correlated. Tests for antimicrobial resistance against ten antibiotics revealed extensive drug and multi-drug resistant isolates. Statistical analyses didn't support a correlation of antibiotic resistance to tested virulence factors suggesting independence of these phenotypic markers and virulence genes. Of special interest was the isolation of Paenibacillus alvei and Geobacillus stearothermophilus from the imported meat samples being the first recorded. The isolation of non-B. cereus species carrying enterotoxigenic genes in meat within Egypt, suggests their impact on food safety and public health and should therefore not be minimised, posing an area that requires further research.

Risk factors for hospitalized patients with resistant or multidrug-resistant Pseudomonas aeruginosa infections: a systematic review and meta-analysis

Background

Identifying risk factors predicting acquisition of resistant Pseudomonas aeruginosa will aid surveillance and diagnostic initiatives and can be crucial in early and appropriate antibiotic therapy. We conducted a systematic review examining risk factors of acquisition of resistant P. aeruginosa among hospitalized patients.

Methods

MEDLINE®, EMBASE®, and Cochrane Central were searched between 2000 and 2016 for studies examining independent risk factors associated with acquisition of resistant P. aeruginosa, among hospitalized patients. Random effects model meta-analysis was conducted when at least three or more studies were sufficiently similar.

Results

Of the 54 eligible articles, 28 publications (31studies) examined multi-drug resistant (MDR) or extensively drug resistant (XDR) P. aeruginosa and 26 publications (29 studies) examined resistant P. aeruginosa. The acquisition of MDR P. aeruginosa, as compared with non-MDR P. aeruginosa, was significantly associated with intensive care unit (ICU) admission (3 studies: summary adjusted odds ratio [OR] 2.2) or use of quinolones (4 studies: summary adjusted OR 3.59). Acquisition of MDR or XDR compared with susceptible P. aeruginosa was significantly associated with prior hospital stay (4 studies: summary adjusted OR 1.90), use of quinolones (3 studies: summary adjusted OR 4.34), or use of carbapenems (3 studies: summary adjusted OR 13.68). The acquisition of MDR P. aeruginosa compared with non-P. aeruginosa was significantly associated with prior use of cephalosporins (3 studies: summary adjusted OR 3.96), quinolones (4 studies: summary adjusted OR 2.96), carbapenems (6 studies: summary adjusted OR 2.61), and prior hospital stay (4 studies: summary adjusted OR 1.74). The acquisition of carbapenem-resistant P. aeruginosa compared with susceptible P. aeruginosa, was statistically significantly associated with prior use of piperacillin-tazobactam (3 studies: summary adjusted OR 2.64), vancomycin (3 studies: summary adjusted OR 1.76), and carbapenems (7 studies: summary adjusted OR 4.36).

Conclusions

Prior use of antibiotics and prior hospital or ICU stay was the most significant risk factors for acquisition of resistant P. aeruginosa. These findings provide guidance in identifying patients that may be at an elevated risk for a resistant infection and emphasize the importance of antimicrobial stewardship and infection control in hospitals.

Recent Anti-Microbial Exposure Is Associated with More Complications after Elective Surgery

BACKGROUND

Recent anti-microbial exposure has been associated with poor outcomes after infection in a mixed population. We hypothesized that recent anti-microbial exposure would be associated with poor outcomes of elective surgery.

METHODS

From August 2015 to August 2016, all elective surgical patients were questioned prospectively about anti-microbial exposure during the prior three months. Multivariable models were used to calculate risk-adjusted odds ratios for anti-microbial exposure controlling for surgeon influence. Primary outcomes were any serious complication, any complication, any infection, and surgical site infection. Secondary outcomes were length of stay, C. difficile infection, and death. A separate analysis of patients excluding those having colorectal surgery who had undergone an oral antibiotic bowel preparation also was performed.

RESULTS

Ninety-four percent of eligible patients (n = 1,538) answered the exposure question, with a three-month anti-microbial exposure rate of 34.1%. Colorectal surgery patients had the highest exposure rate, whereas hernia patients had the lowest. Exposed patients had higher rates of any complication, any infection, and surgical site infection, as well as a median two-day longer hospital stay. There were no differences in C. difficile infection or death between the groups. After risk adjustment, anti-microbial exposure was independently associated with any serious complication for all patients as well as with complications and infection in patients having an operation other than colorectal surgery.

CONCLUSION

Recent anti-microbial exposure is associated with more complications of elective surgery. Anti-microbial drug-induced alterations in microbiome-related inflammatory responses may play a role, highlighting an opportunity for pre-surgical intervention in this at-risk population.

Prevention and Control of Multidrug-Resistant Gram-Negative Bacteria in Adult Intensive Care Units: A Systematic Review and Network Meta-analysis

Background

This study evaluated the relative efficacy of strategies for the prevention of multidrug-resistant gram-negative bacteria (MDR-GNB) in adult intensive care units (ICUs).

Methods

A systematic review and network meta-analysis was performed; searches of the Cochrane Library, PubMed, Embase, and CINAHL (Cumulative Index to Nursing and Allied Health Literature) included all randomized controlled trials and observational studies conducted in adult patients hospitalized in ICUs and evaluating standard care (STD), antimicrobial stewardship program (ASP), environmental cleaning (ENV), decolonization methods (DCL), or source control (SCT), simultaneously. The primary outcomes were MDR-GNB acquisition, colonization, and infection; secondary outcome was ICU mortality.

Results

Of 3805 publications retrieved, 42 met inclusion criteria (5 randomized controlled trials and 37 observational studies), involving 62068 patients (median age, 58.8 years; median APACHE [Acute Physiology and Chronic Health Evaluation] II score, 18.9). The majority of studies reported extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and MDR Acinetobacter baumannii. Compared with STD, a 4-component strategy composed of STD, ASP, ENV, and SCT was the most effective intervention (rate ratio [RR], 0.05 [95% confidence interval {CI}, .01-.38]). When ENV was added to STD+ASP or SCT was added to STD+ENV, there was a significant reduction in the acquisition of MDR A. baumannii (RR, 0.28 [95% CI, .18-.43] and 0.48 [95% CI, .35-.66], respectively). Strategies with ASP as a core component showed a statistically significant reduction the acquisition of ESBL-producing Enterobacteriaceae (RR, 0.28 [95% CI, .11-.69] for STD+ASP+ENV and 0.23 [95% CI, .07-.80] for STD+ASP+DCL).

Conclusions

A 4-component strategy was the most effective intervention to prevent MDR-GNB acquisition. As some strategies were differential for certain bacteria, our study highlighted the need for further evaluation of the most effective prevention strategies.

Prevalence of Recent Antimicrobial Exposure among Elective Surgical Patients

BACKGROUND

The annual prevalence of antimicrobial exposure is high in the outpatient setting and should be a common exposure for surgical patients. Antimicrobials have negative side effects and may be associated with poor outcomes. Logically, one would expect surgical patients to be particularly susceptible to any negative effects of recent antimicrobial exposure. Despite these observations, however, the prevalence of recent antimicrobial exposure among surgical patients remains undefined. The purpose of this study is to define the prevalence of antimicrobial exposure in patients undergoing elective surgical procedures.

METHODS

Patients presenting for elective operations between August 4, 2015 and August 3, 2016 at our institution were asked prospectively about any antimicrobial exposure in the previous three months. Answers were recorded as either Yes, No, or Unsure. Patients were grouped according to age, American Society of Anesthesiologists (ASA) score, primary operative service, and post-operative destination. Descriptive statistics were employed using simple percentages and chi-square analysis when appropriate. Cochrane-Armitage test was used to evaluate temporal trends.

RESULTS

There were 21,473 elective surgical procedures performed during the study period across 13 operative services. Answers were recorded for 91.2% cases. The overall prevalence of exposure during this period was 28.6%. Exposure varied with age, ASA score, and surgical specialty. Vascular and transplant operations had the highest prevalence of exposure while ophthalmology and pediatric orthopedic procedures had the lowest. Patients with recent antimicrobial exposure were less likely to be discharged home on the same day and more likely to be admitted to an intensive care or intermediate care unit than those who denied recent exposure.

CONCLUSION

In this descriptive analysis, the prevalence of recent antimicrobial exposure is overall approximately 28.6% and is higher than anticipated. Further work is needed to determine to what extent, if any, recent antimicrobial exposure impacts post-operative outcomes.

Is surveillance for colonization of carbapenem-resistant gram-negative bacteria important in adult bone marrow transplantation units?

BACKGROUND

The aim of this study was to investigate the rate of carbapenem-resistant gram-negative bacilli (CRGNB) colonization and to analyze the risk factors associated with CRGNB colonization.

METHODS

This prospective study was conducted in adult patients hospitalized in hematopoietic stem cell transplantation (HSCT) units over a period of 8 months. Rectal swab samples were obtained from each participant every Monday, and patients CRGNB positive on admission were excluded.

RESULTS

Of 185 participants, the median age was 47 years, and 59.5% were men. CRGNB colonization was detected in 21 (11.4%) patients. The most commonly isolated CRGNB were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Multivariate analysis revealed that busulfan use (11.9 times), fludarabine use (6.4 times), transfer from another hospital (7.8 times), transfer between units (9.3 times), and central venous catheterization (5.1 times) were risk factors for CRGNB colonization. During the study period, febrile neutropenia (FN) developed in 9 (56.2%) of the 21 colonized patients, and 1 patient died.

CONCLUSIONS

Screening of patients for CRGNB colonization may have a role in preventing the spread of CRGNB. However, the empirical antimicrobial treatment for FN in patients with CRGNB colonization did not change, and their mortality rates were similar.

Aggressive Antimicrobial Initiation for Suspected Intensive Care Unit-Acquired Infection Is Associated with Decreased Long-Term Survival after Critical Illness

BACKGROUND

The long-term significance of early and prolonged antibiotic use in critically ill patients is yet to be described. Several studies suggest that antimicrobial exposure may have as yet unrecognized long-term effects on clinically meaningful outcomes. Our group previously conducted a quasi-experimental, before and after observational cohort study of hemodynamically stable surgical patients suspected of having an intensive care unit-acquired infection. This study demonstrated that aggressive initiation of antimicrobial therapy was associated with increased 30-day deaths. In a follow-up survival analysis, we hypothesized that aggressive antimicrobial treatment would not be a significant predictor of long-term death.

METHODS

Survival data for the 201 patients included in the initial study were obtained from our clinical data repository. Univariable analysis, Kaplan-Meier, and Cox proportional hazards models were used. Survival was evaluated at one and four years. Age, gender, Acute Physiology and Chronic Health Evaluation (APACHE) II score, and co-morbidities were chosen a priori for potential inclusion in the model. Variables that met the model assumptions after testing were included in the final model.

RESULTS

Follow-up data were available for 190 patients (95 in each group) representing 94.5% of the initial cohort. Twenty-four (25.3%) patients in the aggressive group had initial APACHE II scores of less than 15 compared with 13 (13.7%) patients in the conservative group (p = 0.04). There was a trend toward higher deaths in the aggressive group at four years (41.1% vs. 30.5%; p = 0.13). Kaplan-Meier analysis demonstrated a difference in survival at one year but not at four years. The Cox proportional hazards model showed a higher long-term death for patients in the aggressive antimicrobial group at both one and four years (hazard rate: 2.26 and 1.70, respectively).

CONCLUSION

Aggressive initiation of antimicrobial therapy is independently associated with decreased long-term survival after critical illness. While further work is needed to confirm these findings, waiting for evidence of infection before initiation of antibiotic agents may be beneficial.

Host and Pathogen Biomarkers for Severe Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa is among the leading causes of severe nosocomial infections, particularly affecting critically ill and immunocompromised patients. Here we review the current knowledge on the factors underlying the outcome of P. aeruginosa nosocomial infections, including aspects related to the pathogen, the host, and treatment. Intestinal colonization and previous use of antibiotics are key risk factors for P. aeruginosa infections, whereas underlying disease, source of infection, and severity of acute presentation are key host factors modulating outcome; delayed adequate antimicrobial therapy is also independently associated with increased mortality. Among pathogen-related factors influencing the outcome of P. aeruginosa infections, antibiotic resistance, and particularly multidrug-resistant profiles, is certainly of paramount relevance, given its obvious effect on the chances of appropriate empirical therapy. However, the direct impact of antibiotic resistance in the severity and outcomes of P. aeruginosa infections is not yet well established. The interplay between antibiotic resistance, virulence, and the concerning international high-risk clones (such as ST111, ST175, and ST235) still needs to be further analyzed. On the other hand, differential presence or expression of virulence factors has been shown to significantly impact disease severity and mortality. The likely more deeply studied P. aeruginosa virulence determinant is the type III secretion system (T3SS); the production of T3SS cytotoxins, and particularly ExoU, has been well established to determine a worse outcome both in respiratory and bloodstream infections. Other relevant pathogen-related biomarkers of severe infections include the involvement of specific clones or O-antigen serotypes, the presence of certain horizontally acquired genomic islands, or the expression of other virulence traits, such as the elastase. Finally, recent data suggest that host genetic factors may also modulate the severity of P. aeruginosa infections.

A prospective survey of Pseudomonas aeruginosa colonization and infection in the intensive care unit

Background

Pseudomonas aeruginosa (PA) surveillance may improve empiric antimicrobial therapy, since colonizing strains frequently cause infections. This colonization may be ‘endogenous’ or ‘exogenous’, and the source determines infection control measures. We prospectively investigated the sources of PA, the clinical impact of PA colonization upon admission and the dynamics of colonization at different body sites throughout the intensive care unit stay.

Methods

Intensive care patients were screened on admission and weekly from the pharynx, endotracheal aspirate, rectum and urine. Molecular typing was performed using Enterobacterial Repetitive Intergenic Consensus Polymerase Chain reaction (ERIC-PCR).

Results

Between November 2014 and January 2015, 34 patients were included. Thirteen (38%) were colonized on admission, and were at a higher risk for PA-related clinical infection (Hazard Ratio = 14.6, p = 0.0002). Strains were often patient-specific, site-specific and site-persistent. Sixteen out of 17 (94%) clinical isolates were identical to strains found concurrently or previously on screening cultures from the same patient, and none were unique. Ventilator associated pneumonia-related strains were identical to endotracheal aspirates and pharynx screening (87–75% of cases). No clinical case was found among patients with repeated negative screening.

Conclusion

PA origin in this non-outbreak setting was mainly ‘endogenous’ and PA-strains were generally patient- and site-specific, especially in the gastrointestinal tract. While prediction of ventilator associated pneumonia-related PA-strain by screening was fair, the negative predictive value of screening was very high.

Prolonged outbreak of clonal MDR Pseudomonas aeruginosa on an intensive care unit: contaminated sinks and contamination of ultra-filtrate bags as possible route of transmission?

BACKGROUND

We report on an outbreak in a surgical, interdisciplinary intensive care unit (ICU) of a tertiary care hospital. We detected a cluster of ICU patients colonized or infected with multidrug-resistant Pseudomonas aeruginosa. We established an outbreak investigation team, performed an exploratory epidemiological analysis and initiated an epidemiology-based intervention.

METHODS

As part of the outbreak investigation, we performed microbiological examinations of the sinks in the patient rooms and a retrospective case-control study. All patients admitted to the outbreak ICU between January 2012 and February 2014 were included. Cases were patients colonized with the outbreak strain. Controls were patients with a different Pseudomonas aeruginosa strain. Risk factors were evaluated using multivariable conditional logistic regression analysis. Strain typing was performed using the repetitive element-based polymerase chain reaction (rep-PCR) DiversiLab system.

RESULTS

The outbreak strain was found in the sinks of five (of 16) patient rooms. Altogether 21 cases and 21 (randomly selected) controls were included. In the univariate analysis, there was no significant difference in baseline data of the patients. In the multivariate analysis, stay in a room with a colonized sink (Odds Ratio[OR] 11.2, p = 0.007) and hemofiltration (OR 21.9, p = 0.020) were independently associated with an elevated risk for colonization or infection by the outbreak strain. In a subsequent evaluation of the work procedures associated with hemofiltration, we found that the ultra-filtrate bags had been on average five times per day emptied in the sinks of the patient rooms and were used multiple for the same patient. We exchanged the traps of the contaminated sinks and eliminated work procedures involving sinks in patient rooms by implementation of single use bags, which are emptied outside patient rooms to reduce splash water at the sinks. In the 20 month follow-up period, the outbreak strain was detected only once, which indicated that the outbreak had been ceased (incidence 0.75% vs. 0.04%, p < 0.001) Furthermore, the incidence of Pseudonomas aeruginosa overall was significantly decreased (2.5% vs. 1.5%, p < 0.001).

CONCLUSION

In ICUs, limiting work processes involving sinks results in reduced multidrug-resistant Pseudomonas aeruginosa rates. ICUs with high rates of Pseudomonas aeruginosa should consider eliminating work processes that involve sinks and potentially splash water in close proximity to patients.

TRIAL REGISTRATION

All data were surveillance based data which were obtained within the German Law on Protection against Infection ("Infektionsschutzgesetz"). Therefore a trial registration was not required.

Patient specific risk stratification for antimicrobial resistance and possible treatment strategies in gram-negative bacterial infections

INTRODUCTION

The isolation of multi-drug-resistant gram-negative (MDRGN) pathogens has progressively increased worldwide and has been associated with important delays in the prescription of an adequate antibiotic treatment, resulting in increased mortality rates. Patient's stratification for MDRGN infections to optimize the prescription of an adequate empiric antimicrobial regimen is crucial. Areas covered: This article covers MDRGN epidemiology, with a specific focus on risk factors for harbouring infections sustained by extended-spectrum-Beta-lactamase (ESBL), carbapenem resistant Enterobacteriacae (CRE), MDR Pseudomonas aeruginosa and MDR Acinetobacter baumanii. Moreover, we will propose an algorithm for the choice of empiric treatment when a MDRGN infection is suspected. Expert commentary: Although in clinical practice, a patient's stratification represents a challenge, whenever a MDRGN pathogen is suspected broad-spectrum, combination empiric treatment should be promptly started, looking for a balance between the prescription of an adequate empiric treatment and the risk of resistance selection.

Acute Inflammatory Response of Patients with Pseudomonas aeruginosa Infections: A Prospective Study

The severity of Pseudomonas aeruginosa (PA) infection may be determined by the interaction with the host immune system. We designed a prospective study to assess the relationship between the inflammatory response and the clinical presentation and outcome of PA infection. We also investigated whether there are differences in the inflammatory response depending on the resistance profile of PA. Interleukin-6 (IL-6), IL-10, procalcitonin (PCT), and C-reactive protein (CRP) were measured. Sixty-nine infection episodes were recorded; 40 caused by non-multidrug-resistant (non-MDR) strains [29 (73%) respiratory; 8 (20%) bacteremia], 12 by MDR non-extensively drug-resistant (MDR-non-XDR) [9 (75%) respiratory; 3 (25%) bacteremia], and 17 by XDR strains [9 (53%) respiratory; 7 (41%) bacteremia]. All inflammatory parameters were significantly higher in patients who developed acute organ dysfunction and bacteremia. PCT levels were higher in patients with early mortality [p = 0.050]. Inflammatory biomarkers were higher in patients with XDR than in those with non-MDR PA [IL-6 430 (67-951) vs. 77 (34-216), p = 0.02; IL-10 3.3 (1.5-16.3) vs. 1.3 (0-3.9), p = 0.02; and PCT 1.1 (0.6-5.2) vs. 0.3 (0.1-1.0), p = 0.008]. The intensity of inflammatory response was associated with the severity of PA infection, particularly if bacteremia occurred. Only PCT was documented useful to predict the outcome. XDR infections presented a higher inflammatory response; related in part to the larger number of bloodstream infections in this group.

IV Immunoglobulin for Acute Lung Injury and Bacteremia in Pseudomonas aeruginosa Pneumonia

OBJECTIVES

Virulent and multidrug-resistant Pseudomonas aeruginosa causes a lethal pneumonia, especially in patients who are artificially ventilated. It has been reported that the virulence mechanism used by P. aeruginosa, which is linked to acute lung injury, is strongly associated with the type III secretion system, and specific antibodies targeting this system have shown a protective effect in both experimental and clinical settings. We investigated the effect of administering IV immunoglobulins on P. aeruginosa pneumonia, including its associated bacteremia and mortality, although focusing especially on type III secretion system-associated P. aeruginosa virulence.

DESIGN

Prospective randomized and controlled animal study.

SETTING

University laboratory.

SUBJECTS

Male ICR mice.

INTERVENTIONS

Mice were infected intratracheally with a lethal dose of the virulent P. aeruginosa PA103 strain. IV immunoglobulin administration was examined in three different settings: 1) premixed; 2) pre-IV, prophylactic administration before bacterial infection; and 3) post-IV, therapeutic administration after bacterial infection. The effect of specific antigen titer depletion of IV immunoglobulins was also examined.

MEASUREMENTS AND MAIN RESULTS

Survival and body temperature were monitored for 24 hours. Bacteremia, cytokine concentration, myeloperoxidase activity, WBC counts in the blood, and lung bacterial load were evaluated. Survival improved significantly in mice that received IV immunoglobulins (p < 0.05). Lung edema, lung bacteriologic load, and bacteremia decreased significantly in the IV immunoglobulin-treated mice (p < 0.05). The mechanism of protection was associated with the presence of antibodies against both PcrV and some bacterial surface antigens in the IV immunoglobulins.

CONCLUSIONS

IV immunoglobulin administration had a significantly protective effect against lethal infection from virulent P. aeruginosa. Prophylactic IV immunoglobulin administration at the highest dose was comparable with that achieved by administrating a specific anti-PcrV polyclonal IgG into the mice. The mechanism of protection is likely to involve the synergic action of anti-PcrV titers and antibodies against some surface antigen(s) that block the type III secretion system-associated virulence of P. aeruginosa.

Rates of gastrointestinal tract colonization of carbapenem-resistant Enterobacteriaceae and Pseudomonas aeruginosa in hospitals in Saudi Arabia

Carbapenem-resistant Enterobacteriaceae (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPAE) are globally a major medical issue, especially in intensive care units. The digestive tract is the main reservoir for these isolates; therefore, rectal swab surveillance is highly recommended. The purpose of this study was to detect the prevalence of gastrointestinal tract colonization of CRE and CRPAE in patients admitted to intensive care units in Saudi Arabia. This project also aimed to characterize carbapenem-hydrolyzing enzyme production in these isolates. From February to May 2015, 200 rectal swab specimens were screened by CHROMagar KPC. Organism identification and susceptibility testing were performed using the Vitek 2 system. One CRE and 13 CRPAE strains were identified, for a prevalence of 0.5% (1/200) and 6.5% (13/200) respectively. Strains showed high genetic diversity using enterobacterial repetitive intergenic consensus sequence-based PCR. NDM type and VIM type were detected by PCR in four and one CRPAE isolates respectively. ampC overexpression was detected in eight CRPAE isolates using Mueller-Hinton agar containing 1000 μg/mL cloxacillin. CTX-M-15 type was detected in 1 CRE by PCR. The prevalence of CRE strain colonization was lower than that of CRPAE isolates. The detection of NDM and VIM in the colonizing CRPAE strains is a major infection control concern. To our knowledge, this is the first study in Saudi Arabia and the gulf region focusing on digestive tract colonization of CRE and CRPAE organisms and characterizing the mechanisms of carbapenem resistance.

Prevalence and risk factors associated with colonization and infection of extensively drug-resistant Pseudomonas aeruginosa: a systematic review

Pseudomonas aeruginosa is a Gram-negative human pathogen with extensively drug-resistant (XDR) strains emerging in hospitals across the globe. This systematic review is focused on the worldwide prevalence of XDR P. aeruginosa (XDR-PA) and on the risk factors associated with its colonization and infection, based on literature available through PubMed, Web of Science and BioMed Central databases. An overview of surveillance systems is provided as well as a synopsis on the prevalence of XDR-PA, showing an increase in recent reports. Risk factors independently associated with XDR-PA colonization or infections are described in four groups with reference to antimicrobial therapy, medical devices as well as patient- and hospital environment-related factors.

Prospective observational study of prior rectal colonization status as a predictor for subsequent development of Pseudomonas aeruginosa clinical infections

The potential role of Pseudomonas aeruginosa (PA) intestinal colonization in the subsequent development of infections has not been thoroughly investigated. The aims of this study were to assess the role of PA intestinal colonization as a predictor of subsequent infections and to investigate the risk factors associated with the development of PA infection in patients in the intensive care unit (ICU). For this purpose, a prospective study was conducted that included (i) active surveillance of PA rectal colonization at ICU admission and weekly until ICU discharge, (ii) detection of PA clinical infections, and (iii) genotypic analysis by pulsed-field gel electrophoresis (PFGE). A total of 414 patients were included, of whom 179 (43%) were colonized with PA. Among the 77 patients who developed PA infection, 69 (90%) had prior PA colonization, and 60 (87%) of these showed genotyping concordance between rectal and clinical isolates. The probability of PA infection 14 days after ICU admission was 26% for carriers versus 5% for noncarriers (P < 0.001). Cox regression analysis identified prior PA rectal colonization as the main predictor of PA infection (hazard ratio [HR], 15.23; 95% confidence interval [CI], 6.9 to 33.7; P < 0.001). Prior use of nonantipseudomonal penicillins was also identified as an independent variable associated with PA infection (HR, 2.15; 95% CI, 1.3 to 3.55; P < 0.003). Our study demonstrated that prior PA rectal colonization is a key factor for developing PA infection.

Profile of ceftolozane/tazobactam and its potential in the treatment of complicated intra-abdominal infections

Drug-resistant pathogens have gained a foothold especially in the most vulnerable patient populations, hospitalized and immunocompromised individuals. Furthermore, extended-spectrum β-lactamase and carbapenemase-producing organisms are finding their way even into the community, with patients presenting to the hospital with established colonization and infection with resistant Enterobacteriaceae in particular. Recently, a novel antipseudomonal cephalosporin in combination with an established Class A β-lactamase inhibitor, ceftolozane/tazobactam has been approved by the FDA for use in the treatment of complicated urinary tract infections and complicated intra-abdominal infections. Ceftolozane is a uniquely potent antipseudomonal cephalosporin because of its high affinity for the penicillin-binding proteins of Pseudomonas aeruginosa, its low affinity for the intrinsic Class C β-lactamases of P. aeruginosa, its ability to enter P. aeruginosa through the outer membrane without the utilization of OprD protein, and the fact that it is not a substrate of the often upregulated MexAB/OprM efflux system of P. aeruginosa. The biological chemistry, pharmacokinetics/pharmacodynamics, microbiologic spectrum, and clinical trials that led to the approval of ceftolozane is reviewed. A discussion regarding its potential role in the treatment of complicated intra-abdominal infections and other infectious disease syndromes associated with drug-resistant pathogens follows.

The role of systemic antibiotics in acquiring respiratory tract colonization with gram-negative bacteria in intensive care patients: a nested cohort study

OBJECTIVE

Colonization of the respiratory tract with Gram-negative bacteria in intensive care patients increases the risk of subsequent infections. Application of systemic antibiotics may prevent colonization with Gram-negative bacteria, but this effect has never been quantified. The objective of this study was to determine associations between systemic antibiotic use and acquisition of respiratory tract colonization with Gram-negative bacteria in ICUs.

DESIGN

A nested cohort study.

SETTING

A university hospital and a teaching hospital.

PATIENTS

Patients with ICU stay of more than 48 hours and absence of respiratory tract colonization with Gram-negative bacteria on ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acquisition was determined through protocolized surveillance. Associations were investigated with Cox regression models with antibiotics as a time-dependent covariate. In all, 250 of 481 patients (52%) acquired respiratory tract colonization with Gram-negative bacteria after a median of 5 days (interquartile range, 3-8 d) (acquisition rate, 77.1/1,000 patient-days at risk). Antibiotic exposure during ICU admission was present in 78% and 72% of the patients with and without acquired Gram-negative bacteria colonization, respectively. In Kaplan-Meier curve analysis, the median times to acquisition of Gram-negative bacteria were 9 days (95% CI, 7.9-10.1) and 6 days (95% CI, 4.8-7.2) in patients receiving and not receiving antibiotics, respectively. In time varying Cox regression analysis, however, the association between acquired colonization and systemic antibiotics was not statistically significant (hazard ratio, 0.90; 95% CI, 0.70-1.16).

CONCLUSIONS

Among patients not colonized with Gram-negative bacteria in the respiratory tract at admission to ICU, systemic antibiotics during ICU stay were not associated with a reduction in acquisition of Gram-negative bacteria carriage in the respiratory tract during the ICU stay.

Acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill medical patients: role of colonization pressure and antibiotic exposure

INTRODUCTION

The objective of this work was to investigate the risk factors for the acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill patients, taking into account colonization pressure.

METHODS

We conducted a prospective cohort study in an 8-bed medical intensive care unit during a 35-month period. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48 hours of admission and thrice weekly thereafter. During the study, a policy of consecutive mixing and cycling periods of three classes of antipseudomonal antibiotics was followed in the unit.

RESULTS

Of 850 patients admitted for ≥ 3 days, 751 (88.3%) received an antibiotic, 562 of which (66.1%) were antipseudomonal antibiotics. A total of 68 patients (8%) carried P. aeruginosa upon admission, and among the remaining 782, 104 (13%) acquired at least one strain of P. aeruginosa during their stay. Multivariate analysis selected shock (odds ratio (OR) = 2.1; 95% confidence interval (CI), 1.2 to 3.7), intubation (OR = 3.6; 95% CI, 1.7 to 7.5), enteral nutrition (OR = 3.6; 95% CI, 1.8 to 7.6), parenteral nutrition (OR = 3.9; 95% CI, 1.6 to 9.6), tracheostomy (OR = 4.4; 95% CI, 2.3 to 8.3) and colonization pressure >0.43 (OR = 4; 95% CI, 1.2 to 5) as independently associated with the acquisition of P. aeruginosa, whereas exposure to fluoroquinolones for >3 days (OR = 0.4; 95% CI, 0.2 to 0.8) was protective. In the whole series, prior exposure to carbapenems was independently associated with carbapenem resistance, and prior amikacin use predicted piperacillin-tazobactam, fluoroquinolone and multiple-drug resistance.

CONCLUSIONS

In critical care settings with a high rate of antibiotic use, colonization pressure and non-antibiotic exposures may be the crucial factors for P. aeruginosa acquisition, whereas fluoroquinolones may actually decrease its likelihood. For the acquisition of strains resistant to piperacillin-tazobactam, fluoroquinolones and multiple drugs, exposure to amikacin may be more relevant than previously recognized.

Carbapenemases: A worldwide threat to antimicrobial therapy

Carbapenems are potent β-lactams with activity against extended-spectrum cephalosporinases and β-lactamases. These antibiotics, derived from thienamycn, a carbapenem produced by the environmental bacterium Streptomyces cattleya, were initially used as last-resort treatments for severe Gram-negative bacterial infections presenting resistance to most β-lactams but have become an empirical option in countries with high prevalence of Extended Spectrum β-lactamase-producing bacterial infections. Imipenem, the first commercially available carbapenem, was approved for clinical use in 1985. Since then, a wide variety of carbapenem-resistant bacteria has appeared, primarily Enterobacteriaceae such as Escherichia coli or Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa and Acinetobacter baumannii, presenting different resistance mechanisms. The most relevant mechanism is the production of carbapenem-hydrolyzing β-lactamases, also known as carbapenemases. These enzymes also inactivate all known β-lactams, and some of these enzymes can be acquired through horizontal gene transfer. Moreover, plasmids, transposons and integrons harboring these genes typically carry other resistance determinants, rendering the recipient bacteria resistant to almost all currently used antimicrobials, as is the case for K. pneumoniae carbapenemase - or New Delhi metallo-β-lactamases-type enzymes. The recent advent of these enzymes in the health landscape presents a serious challenge. First, the emergence of carbapenemases limits the currently available treatment options; second, these enzymes pose a risk to patients, as some studies have demonstrated high mortality associated with carbapenemase-producing bacterial infections; and third, these circumstances require an extra cost to sanitary systems, which are particularly cumbersome in developing countries. Therefore, emphasis should be placed on the early detection of these enzymes, the prevention of the spread of carbapenemase-producing bacteria and the development of new drugs resistant to carbapenemase hydrolysis.

Genome Sequence of a Pandrug-Resistant Pseudomonas aeruginosa Strain, YN-1

A highly rampant multidrug-resistant strain of Pseudomonas aeruginosa appeared in a hospital in Yunnan Province, China. Here, we report the genome sequence of the pandrug-resistant (PDR) P. aeruginosa strain recovered from a patient in 2013.

Clinical and treatment-related risk factors for nosocomial colonisation with extensively drug-resistant Pseudomonas aeruginosa in a haematological patient population: a matched case control study

Background

This study aimed to investigate risk factors for colonisation with extensively drug-resistant P. aeruginosa (XDR-PA) in immunocompromised patients and to build a clinical risk score (CRS) based on these results.

Methods

We conducted a matched case–control study with 31 cases and 93 controls (1:3). Cases were colonised with XDR-PA during hospitalisation. Independent risk factors were determined using a three step conditional logistic regression procedure. A CRS was built with respect to the corresponding risk fraction of each risk factor, and its discriminatory power was estimated by receiver operating characteristic (ROC) analysis.

Results

The presence of a central venous catheter (OR 7.41, P = 0.0008), the presence of a urinary catheter (OR 21.04, P < 0.0001), CRP > 10 mg/dl (OR 7.36, P = 0.0015), and ciprofloxacin administration (OR 5.53, P = 0.025) were independent risk factors. The CRS exhibited a high discriminatory power, defining a high risk population with an approximately fourteen times greater risk for XDR-PA colonisation.

Conclusions

Unnecessary use of antibiotics, particularly ciprofloxacin should be avoided, and a high standard of infection control measures must be achieved when using medical devices. A CRS can be used for adaptation of the active screening culture policy to the local setting.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0650-9) contains supplementary material, which is available to authorized users.