Risk factor for intestinal carriage of carbapenem-resistant Acinetobacter baumannii and the impact on subsequent infection among patients in an intensive care unit: an observational study

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.

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

Incidence of infection with multidrug-resistant Gram-negative bacteria and vancomycin-resistant enterococci in carriers: a systematic review and meta-regression analysis

BACKGROUND

Carriers of multidrug-resistant bacteria are at risk of infections with these bacteria; the precise size of this risk is unclear. We aimed to quantify the effect of gut colonisation on subsequent risk of infection with multidrug-resistant bacteria.

METHODS

We performed a systematic review and meta-regression analysis. We searched PubMed, Embase, Web of Science Core Collection, and Google Scholar for follow-up studies published from Jan 1, 1995, to March 17, 2022, that measured the incidence of infections with multidrug-resistant Gram-negative bacteria (MDR-GNB) and from Jan 1, 1995, to March 15, 2022, that measured the incidence of infections with vancomycin-resistant enterococci (VRE). We included original cohort studies and case-control studies that used incidence-density sampling, included 50 or more patients with enteric colonisation or positive urinary samples as a surrogate marker of colonisation, or both, and analysed infections clearly preceded by colonisation. We did not use any language restrictions. We excluded studies not reporting length of follow-up. Summary data were extracted and independently cross-verified by two authors. Carriage was defined as MDR-GNB or VRE, detected in faecal or urinary cultures. Our primary outcomes were cumulative incidence and incidence density of infection in patients colonised by multidrug-resistant bacteria. To estimate pooled incidences, general linearised mixed-effects meta-regressions were used, adjusting for varying follow-up durations. This study is registered with PROSPERO, CRD42020222415.

FINDINGS

Of the 301 studies identified, 44 studies (26 on MDR-GNB, 14 on VRE, and four on both MDR-GNB and VRE) from 14 countries were retained for qualitative synthesis, 40 of which were analysed with meta-regression, comprising data for 14 049 patients colonised with multidrug-resistant bacteria. The pooled cumulative incidence of infection was 14% (95% CI 10-18; p<0·0001) at a median follow-up time of 30 days for MDR-GNB (845 cases of infection in 9034 patients colonised) and 8% (5-13; p<0·0001) at 30 days for VRE (229 cases of infection in 4747 patients colonised). Infection incidence density (4·26 infections per 1000 patient-days; 95% CI 1·69-6·82) and cumulative incidence of infection (19%, 95% CI 15-25; p<0·0001; 602 cases of infection in 4547 patients colonised) were highest for carbapenem-resistant Gram-negative bacteria at 30 days. Risk of bias was rated low to moderate.

INTERPRETATION

The risk of infection was substantial, with the highest risk for patients colonised with carbapenem-resistant Gram-negative bacteria and the lowest in patients with VRE. These data might help to guide prophylactic and treatment decisions and form a valuable resource for planning clinical trials on targeted prevention.

FUNDING

The Netherlands Organization for Health Research and Development.

Carbapenem-resistant Acinetobacter baumannii: A challenge in the intensive care unit

Carbapenem-resistant Acinetobacter baumannii (CRAB) has become one of the leading causes of healthcare-associated infections globally, particularly in intensive care units (ICUs). Cross-transmission of microorganisms between patients and the hospital environment may play a crucial role in ICU-acquired CRAB colonization and infection. The control and treatment of CRAB infection in ICUs have been recognized as a global challenge because of its multiple-drug resistance. The main concern is that CRAB infections can be disastrous for ICU patients if currently existing limited therapeutic alternatives fail in the future. Therefore, the colonization, infection, transmission, and resistance mechanisms of CRAB in ICUs need to be systematically studied. To provide a basis for prevention and control countermeasures for CRAB infection in ICUs, we present an overview of research on CRAB in ICUs, summarize clinical infections and environmental reservoirs, discuss the drug resistance mechanism and homology of CRAB in ICUs, and evaluate contemporary treatment and control strategies.

Small wards in the ICU: a favorable measure for controlling the transmission of carbapenem-resistant Klebsiella pneumoniae

PURPOSE

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the leading causes of healthcare-associated infections (HAIs) and is particularly pervasive in intensive care units (ICUs). This study takes ICU layout as the research object, and integrates clinical data and bacterial genome analysis to clarify the role of separate, small wards within the ICU in controlling the transmission of CRKP.

METHODS

This study prospectively observed the carriage and spread of CRKP from a long-term in-hospital patient (hereafter called the Patient) colonized with CRKP in the gut and located in a separate, small ward within the ICU. The study also retrospectively investigated CRKP-HAIs in the same ICU. The relationship and transmission between CRKP isolates from the Patient and HAI events in the ICU were explored with comparative genomics.

RESULTS

In this study, 65 CRKP-HAI cases occurred during the investigation period. Seven CRKP-HAI outbreaks were also observed. A total of 95 nonrepetitive CRKP isolates were collected, including 32 strains from the Patient in the separate small ward. Phylogenetic analysis based on core genome single-nucleotide polymorphism (cgSNP) showed that there were five possible CRKP clonal transmission events and two clonal outbreaks (A1, A2) during the study. CRKP strains from the Patient did not cause CRKP between-patient transmission or outbreaks in the ICU during the 5-year study period.

CONCLUSION

The presence of a long-term hospitalized patient carrying CRKP and positioned in a separate, small ward did not lead to CRKP transmission or infection outbreaks in the ICU. Combining a small-ward ICU layout with normative HAI control measures for multidrug-resistant pathogen infection was effective in reducing CRKP transmission.

Efficacy of Lactobacillus fermentum Isolated from the Vagina of a Healthy Woman against Carbapenem-Resistant Klebsiella Infections In Vivo

Carbapenem-resistant Enterobacteriaceae (CRE) that produce Klebsiella pneumoniae carbapenemase are increasingly reported worldwide and have become more and more resistant to nearly all antibiotics during the past decade. The emergence of K. pneumoniae strains with decreased susceptibility to carbapenems, which are used as a last resort treatment option, is a significant threat to hospitalized patients worldwide as K. pneumoniae infection is responsible for a high mortality rate in the elderly and immunodeficient individuals. This study used Lactobacillus fermentum as a candidate probiotic for treating CRE-related infections and investigated its effectiveness. We treated mice with L. fermentum originating from the vaginal fluid of a healthy Korean woman and evaluated the Lactobacilli's efficacy in preventive, treatment, non-establishment, and colonization mouse model experiments. Compared to the control, pre-treatment with L. fermentum significantly reduced body weight loss in the mouse models, and all mice survived until the end of the study. The oral administration of L. fermentum after carbapenemresistant Klebsiella (CRK) infection decreased mortality and illness severity during a 2-week observation period and showed that it affects other strains of CRK bacteria. Also, the number of Klebsiella bacteria was decreased to below 5.5 log₁₀ CFU/ml following oral administration of L. fermentum in the colonization model. These findings demonstrate L. fermentum's antibacterial activity and its potential to treat CRE infection in the future.

[A systematic review and expert's analysis of risk factors of infections in adults due to carbapenem-resistant Pseudomonas aeruginosa or Acinetobacter baumannii in Spain]

OBJECTIVE

The aim of the study is to identify risk factors associated to infections caused by carbapenem-resistant Pseudomonas aeruginosa (CRPA) and carbapenem-resistant Acinetobacter baumannii (CRAB) in adult patients through a systematic literature review, classify them according to their importance and provide recommendations by experts in the Spanish context.

METHODS

We developed a systematic literature review to identify risk factors associated to CRPA or CRAB infections and they were evaluated and discussed by a multidisciplinary panel of experts.

RESULTS

There were included 29 studies for P. aeruginosa and 23 for A. baumannii out of 593 identified through systematic literature review. We identified 38 risk factors for P. aeruginosa and 36 for A. baumannii. After risk factor evaluation by the panel of experts, results for CRPA were: 11 important, 10 slightly important and 15 unimportant risk factors; and for CRAB were: 9 important, 5 slightly important and 19 unimportant risk factors. For both pathogens, previous use of antibiotics and hospitalization were important risk factors.

CONCLUSIONS

We could identify the main risk factors associated to CRPA and CRAB through literature review. There is a need for developing additional studies with higher levels of evidence to identify sooner and better infected patients through associated risk factors.