The natural history of carbapenemase-producing Enterobacterales: progression from carriage of various carbapenemases to bloodstream infection.

BACKGROUND: Little is known about the risk of progression from carbapenemase-producing Enterobacterales (CPE) carriage to CPE bloodstream infection (BSI) outside of high-risk settings. We aimed to determine the incidence of CPE BSI among CPE carriers and to assess whether the incidence differed by carbapenemase, species, and setting. METHODS: We conducted a nationwide population-based retrospective cohort study using national databases. The cohort consisted of all patients in Israel with CPE detected by screening from 1/1/2020 to 10/10/2022. We calculated the cumulative incidence of CPE BSI within 1 year among CPE carriers. We used a competing-risks model with BSI as the outcome and death as the competing risk. RESULTS: The study included 6,828 CPE carriers. The cumulative incidence of CPE BSI was 2.4% (95% CI: 2.1%-2.8%). Compared to KPC, the subhazard of BSI was lower for NDM (aSHR: 0.72, 95% CI: 0.49-1.05) and OXA-48-like (aSHR: 0.60, 95% CI: 0.32-1.12) but these differences did not reach statistical significance. Compared to K. pneumoniae, the subhazard of BSI was lower for carriers of carbapenemase-producing E. coli (aSHR: 0.31, 95% CI: 0.20-0.47). The subhazard of BSI was higher among patients with CPE carriage first detected in intensive care units (aSHR: 2.42, 95% CI: 1.50-3.92) or oncology/hematology wards (aSHR: 3.77, 95% CI: 2.40-5.93) compared to medical wards. CONCLUSIONS: The risk of CPE BSI among CPE carriers is lower than previously reported in studies that focused on high-risk patients and settings. The risk of BSI differs significantly by bacterial species and setting, but not by carbapenemase.

Plasmid-encoded VCC-1 ß-lactamase in a clinical isolate of Aeromonas caviae.

Vibrio cholerae carbapenemase (VCC-1) is a chromosomal encoded class A carbapenemase thus far reported in environmental Vibrio cholerae isolates. Here, we report the first isolation of a blaVCC-1 -carrying Aeromonas caviae from a clinical sample in Israel. The isolate was resistant to all ß-lactam agents, including carbapenems. The blaVCC-1 was located on a large plasmid. GC content suggests that the origin of the blaVCC-1 gene is neither Aeromonas nor Vibrio spp. but an unknown progenitor.

Impact of intensified prevention measures on rates of hospital-acquired bloodstream infection in medical-surgical intensive care units, Israel, 2011 to 2019.

BackgroundCentral line-associated bloodstream infection (CLABSI) is among the most common preventable infectious complications in patients in intensive care units (ICU). In 2011, the Israel National Center for Infection Control initiated a nationwide CLABSI prevention programme.AimTo evaluate the impact of different components of the programme on CLABSI and non-CLABSI rates in medical-surgical ICUs.MethodsWe included data collected from all 29 medical-surgical ICUs in Israel from November 2011 to December 2019. The study period was divided into three phases: I (baseline, initial CLABSI prevention guidelines introduced, initial feedback on rates provided), II (initial guidelines widely implemented, surveillance undertaken, feedback continued) and III (after implementation of additional prevention measures). Interrupted time series analysis was used to compare CLABSI and non-CLABSI rates during the three phases.ResultsThe pooled mean (SD) incidence of CLABSI per 1,000 central line-days dropped from 7.4 (0.38) in phase I to 2.1 (0.13) in phase III (p < 0.001). The incidence rate ratio (IRR) was 0.63 (95% CI: 0.51-0.79) between phases I and II, and 0.78 (95% CI: 0.59-1.02) between phases II and III. The pooled mean (SD) incidence of non-CLABSI per 1,000 patient-days declined from 5.3 (0.24) in phase I to 3.4 (0.13) in phase III (p < 0.001).ConclusionNational CLABSI prevention guidelines, surveillance and feedback resulted in significant reductions in CLABSI and non-CLABSI rates. In the wake of further interventions, significant reduction was achieved in ICUs reporting improvement in the uptake of additional prevention measures.

Large-scale WGS of carbapenem-resistant Acinetobacter baumannii isolates reveals patterns of dissemination of ST clades associated with antibiotic resistance.

OBJECTIVES: To describe the population genetics and antibiotic resistance gene distribution of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates causing infections in three Mediterranean countries. METHODS: Isolates were collected during the 2013-17 AIDA clinical trial in six hospitals in Israel, Greece and Italy. WGS, bioinformatic characterization and antibiotic resistance profiling were performed. RESULTS: In the 247 CRAB isolates characterized in this study, ST distribution varied by country: 29/31 (93.5%) Greek isolates, 34/41 (82.9%) Italian isolates and 70/175 (40.0%) Israeli isolates belonged to ST2. The identified ST2 isolates included eight distinct clades: 2C, 2D and 2H were significantly more common in Italy, while 2F was unique to Greece. The uncommon ST3 was not present among Greek isolates and constituted only 5/41 (12%) Italian isolates. On the other hand, it was much more common among Israeli isolates: 78/175 (44.6%) belonged to ST3. The vast majority of isolates, 240/247 (97.2%), were found to harbour acquired carbapenemases, primarily blaOXA-23. The chromosomal oxaAb (blaOXA-51-like) and ampC genes characteristic of this organism were also ubiquitous. Most (96.4%) ST3 isolates carried a broad-host-range plasmid IncP1α. CONCLUSIONS: The geographical differences in CRAB populations support the theory that clonal spread of CRAB leads to endemicity in hospitals and regions. The close association between antibiotic resistance genes and clades, and between plasmids and STs, suggest that de novo creation of MDR A. baumannii is rare. The clustering of antibiotic resistance genes and plasmids that is unique to each clade/ST, and nearly uniform within clades/STs, suggests that horizontal transmission is rare but crucial to the clade's/ST's success.

National Policy for Carbapenem-Resistant Enterobacteriaceae (CRE) Clearance and Discontinuation of Contact Precautions for CRE Carriers in Post-Acute Care Hospitals in Israel: Impact on Isolation-Days and New Acquisitions.

BACKGROUND: In 2009, the Israeli Ministry of Health implemented in post-acute care hospitals (PACHs) a process of discontinuing carbapenem-resistant Enterobacteriaceae (CRE) carrier status. We evaluated the policy's impact on isolation-days, CRE prevalence among known carriers who had completed clearance testing, and CRE acquisition among noncarriers. METHODS: This retrospective study summarized findings from all 15 PACHs in 2009-2017. CRE carriers were considered cleared and removed from contact isolation after 2 rectal cultures negative for CRE and polymerase chain reaction negative for carbapenemases. Data sources included routine surveillance and 4 point prevalence surveys conducted from 2011 to 2017. RESULTS: During the study period, 887 of 6101 CRE carriers (14.5%) completed clearance testing. From 2013 to 2016, the percentage of patient-days in CRE isolation decreased from 9.4% to 3.9% (P = .008). In all surveys combined, there were 819 known CRE carriers; 411 (50%) had completed clearance testing. Of these, 11.4% (47/411) were CRE positive in the survey. At the ward level, the median percentage of patients with no CRE history who were positive on survey decreased from 11.3% in 2011 to 0% in 2017 (P < .001). We found no ward-level correlation between the proportion of carriers who completed clearance and new acquisitions (ρ = 0.02, P = .86). CONCLUSIONS: A process for discontinuing CRE carrier status in PACHs led to a significant reduction in the percentage of patient-days in contact isolation without increasing CRE acquisitions among noncarriers.

Surgical antibiotic prophylaxis in patients colonized with multidrug-resistant Gram-negative bacteria: practical and conceptual aspects.

Antibiotic resistance threatens the effectiveness of surgical antibiotic prophylaxis (SAP) regimens aimed at preventing surgical site infection (SSI). With a focus on procedures in which Gram-negative bacteria (GNB) are the main pathogens causing SSI, this review summarizes the evidence and describes how SAP must evolve in response to carriage of MDR GNB among surgical patients. Randomized controlled trials of SAP for carriers of resistant GNB require prohibitively large sample sizes. No professional guidelines address the topic of adapting SAP for known carriers of resistant GNB. For patients whose carrier status is unknown, the effects of different SAP strategies have been studied for transrectal ultrasound-guided prostate biopsy and colorectal surgery. The four possible strategies for SAP in the era of antibiotic resistance are: no SAP; universal standard SAP; pre-surgical screening for carriage of antibiotic-resistant pathogens before surgery and targeted SAP (i.e. broad-spectrum antibiotics only for those who screen positive); and universal broad-spectrum SAP. The prevalence of carriage determines the efficiency of each strategy. Decolonization is a potential adjunct to SAP.

Antibiotic exposure and the risk of hospital-acquired diarrhoea and Clostridioides difficile infection: a cohort study.

BACKGROUND: Hospital-acquired diarrhoea (HAD) and Clostridioides difficile infection (CDI) may be triggered by antibiotic use. OBJECTIVES: To determine the effect of specific antibiotic agents and duration of therapy on the risk of HAD and CDI. PATIENTS AND METHODS: A single-centre retrospective cohort study was conducted between May 2012 and December 2014 in the internal medicine division. HAD was defined based on documentation of diarrhoea in the medical record or an uncancelled C. difficile test in the laboratory database. CDI was diagnosed using a two-step test (initial glutamate dehydrogenase and toxin A/B EIA, with PCR for discrepant results). Outcomes first occurred on hospital Day 4 or later. Treatment with antibiotics and days of therapy were modelled. RESULTS: In 29 063 hospitalizations there were 970 HAD events [incidence rate per 10 000 patient days (IR) = 38.5] and 105 CDI events (IR = 3.9). Any antibiotic treatment increased the risk of HAD [adjusted relative risk (aRR) 2.79; 95% CI 2.27-3.43] and CDI (aRR 5.31; 95% CI 2.23-12.69). Each day of ß-lactam/ß-lactamase inhibitors (ßL/ßLIs), carbapenems, IV glycopeptides and metronidazole increased the risk of HAD. Each day of ßL/ßLIs, third- and fourth-generation cephalosporins and carbapenems increased the risk of CDI by over 2%. CONCLUSIONS: Preventing HAD and CDI should focus on reducing the overall use of antibiotics and shortening antibiotic exposure, rather than focusing on specific agents.

Personalized Ertapenem Prophylaxis for Carriers of Extended-spectrum ß-Lactamase-producing Enterobacteriaceae Undergoing Colorectal Surgery.

BACKGROUND: Carriers of extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-PE) who receive cephalosporin-based prophylaxis have twice the risk of surgical site infection (SSI) following colorectal surgery as noncarriers. We tested whether ESBL-PE screening and personalized prophylaxis with ertapenem reduces SSI risk among carriers. METHODS: We conducted a prospective nonrandomized, nonblinded, interventional study in 3 hospitals in Israel, Switzerland, and Serbia. Patients were screened for ESBL-PE carriage before elective colorectal surgery. During the baseline phase, departmental guidelines advised prophylaxis with a cephalosporin plus metronidazole. In the intervention phase, guidelines were changed for ESBL-PE carriers to receive ertapenem. The primary outcome was any type of SSI within 30 days. We calculated adjusted risk differences (ARDs) following logistic regression. RESULTS: The intention-to-treat analysis compared 209 ESBL-PE carriers in the baseline phase to 269 in the intervention phase. SSI rates were 21.5% and 17.5%, respectively (ARD, -4.7% [95% confidence interval {CI}, -11.8% to 2.4%]). Unplanned crossover was high (15%), so to assess efficacy we performed an as-treated analysis comparing 247 patients who received cephalosporin-based prophylaxis with 221 who received ertapenem. SSI rates were 22.7% and 15.8%, respectively (ARD, -7.7% [95% CI, -14.6% to -.8%]), and rates of SSI caused by ESBL-PE were 6.5% and 0.9%, respectively (ARD, -5.6% [95% CI, -8.9% to -2.3%]). There was no significant difference in the rate of deep SSI. The number needed to treat to prevent 1 SSI in ESBL-PE carriers was 13. CONCLUSIONS: Screening for ESBL-PE carriage before colorectal surgery and personalizing prophylaxis for carriers is efficacious in reducing SSI.

Fourier Transform Infrared Spectroscopy Is a New Option for Outbreak Investigation: a Retrospective Analysis of an Extended-Spectrum-Beta-Lactamase-Producing Klebsiella pneumoniae Outbreak in a Neonatal Intensive Care Unit.

The IR Biotyper is a new automated typing system based on Fourier-transform infrared (FT-IR) spectroscopy that gives results within 4 h. We aimed (i) to use the IR Biotyper to retrospectively analyze an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) in a neonatal intensive care unit and to compare results to BOX-PCR and whole-genome sequencing (WGS) results as the gold standard and (ii) to assess how the cutoff values used to define clusters affect the discriminatory power of the IR Biotyper. The sample consisted of 18 isolates from 14 patients. Specimens were analyzed in the IR Biotyper using the default analysis settings, and spectra were analyzed using OPUS 7.5 software. The software contains a feature that automatically proposes a cutoff value to define clusters; the cutoff value defines up to which distance the spectra are considered to be in the same cluster. Based on FT-IR, the outbreak represented 1 dominant clone, 1 secondary clone, and several unrelated clones. FT-IR results, using the cutoff value generated by the accompanying software after 4 replicates, were concordant with WGS for all but 1 isolate. BOX-PCR was underdiscriminatory compared to the other two methods. Using the cutoff value generated after 12 replicates, the results of FT-IR and WGS were completely concordant. The IR Biotyper can achieve the same typeability and discriminatory power as genome-based methods. However, to attain this high performance requires either previous, strain-dependent knowledge about the optimal technical parameters to be used or validation by a second method.

Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test.

BACKGROUND: Gram-negative bacterial capsules are associated with production of carbohydrates, frequently resulting in a mucoid phenotype. Infections caused by capsulated or mucoid A. baumannii are associated with increased clinical severity. Therefore, it is clinically and epidemiologically important to identify capsulated A. baumannii. Here, we describe a density-dependent gradient test to distinguish between capsulated and thin/non-capsulated A. baumannii. RESULTS: Thirty-one of 57 A. baumannii isolates displayed a mucoid phenotype. The density-dependent gradient test was comprised of two phases, with silica concentrations of 30% (top phase) and 50% (bottom phase). Twenty-three isolates migrated to the bottom phase, indicating thin or non-capsulated strains, and 34 migrated to the top phase, suggesting strains suspected to be capsulated. There was agreement between the mucoid and the non-mucoid phenotypes and the density-dependent gradient test for all but three isolates. Total carbohydrates extracted from strains suspected to be capsulated were significantly higher. Transmission electron microscopy confirmed the presence of a capsule in the six representative strains suspected to be capsulated. CONCLUSIONS: The density-dependent gradient test can be used to verify capsule presence in mucoid-appearing A. baumannii strains. Identifying capsulated strains can be useful for directing infection control measures to reduce the spread of hypervirulent strains.

Utilising sigmoid models to predict the spread of antimicrobial resistance at the country level.

BackgroundThe spread of antimicrobial resistance (AMR) is of worldwide concern. Public health policymakers and pharmaceutical companies pursuing antibiotic development require accurate predictions about the future spread of AMR.AimWe aimed to identify and model temporal and geographical patterns of AMR spread and to predict future trends based on a slow, intermediate or rapid rise in resistance.MethodsWe obtained data from five antibiotic resistance surveillance projects spanning the years 1997 to 2015. We aggregated the isolate-level or country-level data by country and year to produce country-bacterium-antibiotic class triads. We fitted both linear and sigmoid models to these triads and chose the one with the better fit. For triads that conformed to a sigmoid model, we classified AMR progression into one of three characterising paces: slow, intermediate or fast, based on the sigmoid slope. Within each pace category, average sigmoid models were calculated and validated.ResultsWe constructed a database with 51,670 country-year-bacterium-antibiotic observations, grouped into 7,440 country-bacterium-antibiotic triads. A total of 1,037 triads (14%) met the inclusion criteria. Of these, 326 (31.4%) followed a sigmoid (logistic) pattern over time. Among 107 triads for which both sigmoid and linear models could be fit, the sigmoid model was a better fit in 84%. The sigmoid model deviated from observed data by a median of 6.5%; the degree of deviation was related to the pace of spread.ConclusionWe present a novel method of describing and predicting the spread of antibiotic-resistant organisms.

Zero or More: Methodological Challenges of Counting and Estimating Deaths Related to Antibiotic-resistant Infections.

Estimates of the number of deaths from antimicrobial-resistant (AMR) infections are important data for clinicians and public health officials advocating for resources to prevent and treat these infections. The aims of this article are to describe the various approaches to calculating deaths from AMR infections, to compare the tally of deaths by each approach, and to explain how to interpret the results. Currently, none of the 3 methods employed by vital statistics systems to count deaths from specific causes (underlying cause of deaths, multiple causes of death, and avoidable deaths) count deaths from AMR infections. These deaths can be estimated by 4 approaches: case-fatality rate, infection-related mortality, and excess mortality using controls with antibiotic-susceptible infections or controls without antibiotic-resistant infections. When encountering discrepant estimates of AMR-related deaths, it is important to consider which method was used and whether it was the right method to answer the question being asked.

Success of a National Intervention in Controlling Carbapenem-resistant Enterobacteriaceae in Israel's Long-term Care Facilities.

BACKGROUND: Long-term care facilities (LTCFs) are a major reservoir of carbapenem-resistant Enterobacteriaceae (CRE) in healthcare facilities, contributing to rapid regional dissemination of CRE. METHODS: In 2008, The Israeli National Center for Infection Control (NCIC) initiated a coordinated, comprehensive intervention in Israel's LTCFs, encompassing approximately 25000 beds in over 300 institutions. The intervention included implementation of population-tailored contact precautions and early detection of carriers. The NCIC established a real-time repository of all CRE carriers and events of acquisition, supervised information exchange between healthcare facilities and directed intervention at the institutional level during local outbreaks. CRE incidence was determined based on detection of CRE, either during LTFC stay or on admission to another facility. Prevalence was determined by a series of 5 cross-sectional surveys commenced between 2008 and 2015. RESULTS: From January 2009 through December 2015, 5265 patients acquired CRE in LTCFs. During the study period, incidence of acquisition declined in all facility types, to approximately 50% of the baseline (P < .001). The number of skilled nursing facilities and nursing homes experiencing ≥ 5 CRE acquisitions annually decreased from 35 to 11 during this period. The point prevalence of newly detected CRE carriage in post-acute care hospitals decreased from 12.3% in the survey commenced in 2008 to 0.8% in that begun in 2015 (P < .001). CONCLUSIONS: A national, coordinated intervention resulted in a sustained decrease in CRE incidence and prevalence in LTCFs. These results support the assumption that centrally coordinated intervention is an essential public health tool in reducing CRE in healthcare facilities.

Carriage of Extended-spectrum Beta-lactamase-producing Enterobacteriaceae and the Risk of Surgical Site Infection After Colorectal Surgery: A Prospective Cohort Study.

BACKGROUND: Antibiotic prophylaxis that covers enteric pathogens is essential in preventing surgical site infections (SSIs) after colorectal surgery. Current prophylaxis regimens do not cover extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE). We aimed to determine whether the risk of SSI following colorectal surgery is higher in ESBL-PE carriers than in noncarriers. METHODS: We conducted a prospective cohort study of patients who underwent elective colorectal surgery in 3 hospitals in Israel, Switzerland, and Serbia between 2012 and 2017. We included patients who were aged ≥18 years, were screened for ESBL-PE carriage before surgery, received routine prophylaxis with a cephalosporin plus metronidazole, and did not have an infection at the time of surgery. The exposed group was composed of ESBL-PE-positive patients. The unexposed group was a random sample of ESBL-PE-negative patients. We collected data on patient and surgery characteristics and SSI outcomes. We fit logistic mixed effects models with study site as a random effect. RESULTS: A total of 3600 patients were screened for ESBL-PE; 13.8% were carriers SSIs occurred in 55/220 carriers (24.8%) and 49/440 noncarriers (11.1%, P < .001). In multivariable analysis, ESBL-PE carriage more than doubled the risk of SSI (odds ratio [OR], 2.36; 95% confidence interval [CI], 1.50-3.71). Carriers had higher risk of deep SSI (OR, 2.25; 95% CI, 1.27-3.99). SSI caused by ESBL-PE occurred in 7.2% of carriers and 1.6% of noncarriers (OR, 4.23; 95% CI, 1.70-10.56). CONCLUSIONS: ESBL-PE carriers who receive cephalosporin-based prophylaxis are at increased risk of SSI following colorectal surgery.

Antimicrobial use trends, Israel, 2012 to 2017.

BackgroundIn 2012, Israel's National Center for Infection Control initiated a national stewardship programme that included mandatory annual reporting of antimicrobial use. Here we present nationwide Israeli data for the period 2012 to 2017.AimThe goal of this study was to detect trends in antimicrobial use in Israel following the introduction of the stewardship programme, as part of an assessment of the programme's impact.MethodsIn this retrospective observational study, data were collected from Israel's health maintenance organisations (HMOs), acute care hospitals and post-acute care hospitals (PACHs). Acute care hospital data were collected for general medical and surgical wards, and medical/surgical intensive care units (ICUs). Data were converted into defined daily doses (DDD), with use rates presented as DDD per 1,000 insured/day in the community and DDD per 100 patient-days in hospitals and PACHs. Trends were analysed using linear regression.ResultsAntimicrobial use decreased across sectors between 2012 and 2017. In the community, the decrease was modest, from 22.8 to 21.8 DDD per 1,000 insured per day (4.4%, p = 0.004). In acute care hospitals, antibiotic DDDs per 100 patient-days decreased from 100.0 to 84.0 (16.0%, p = 0.002) in medical wards, from 112.8 to 94.2 (16.5%, p = 0.004) in surgical wards and from 154.4 to 137.2 (11.1%, p = 0.04) in ICUs. Antimicrobial use decreased most markedly in PACHs, from 29.1 to 18.1 DDD per 100 patient-days (37.8%, p = 0.005).ConclusionBetween 2012 and 2017, antimicrobial use decreased significantly in all types of healthcare institutions in Israel, following the introduction of the nationwide antimicrobial stewardship programme.

Ceftazidime-Avibactam as Salvage Therapy for Infections Caused by Carbapenem-Resistant Organisms.

Ceftazidime-avibactam (CAZ-AVI) is a recently approved ß-lactam-ß-lactamase inhibitor combination with the potential to treat serious infections caused by carbapenem-resistant organisms. Few patients with such infections were included in the CAZ-AVI clinical trials, and clinical experience is lacking. We present a case series of patients with infections caused by carbapenem-resistant Enterobacteriaceae (CRE) or Pseudomonas aeruginosa (CRPa) who were treated with CAZ-AVI salvage therapy on a compassionate-use basis. Physicians who had prescribed CAZ-AVI completed a case report form. We used descriptive statistics to summarize patient characteristics and treatment outcomes. We used the Wilcoxon rank sum test and Fisher's exact test to compare patients by treatment outcome. The sample included 36 patients infected with CRE and two with CRPa. The most common infections were intra-abdominal. Physicians categorized 60.5% of patients as having life-threatening infections. All but two patients received other antibiotics before CAZ-AVI, for a median of 13 days. The median duration of CAZ-AVI treatment was 16 days. Twenty-five patients (65.8%) concurrently received other antibiotics to which their pathogen was nonresistant in vitro Twenty-eight patients (73.7%, 95% confidence interval [CI], 56.9 to 86.6%) experienced clinical and/or microbiological cure. Five patients (20.8%) with documented microbiological cure died, whereas 10 patients (71.4%) with no documented microbiological cure died (P = 0.01). In three-quarters of cases, CAZ-AVI (alone or combined with other antibiotics) cured infections caused by carbapenem-resistant organisms, 95% of which had failed previous therapy. Microbiological cure was associated with improved survival. CAZ-AVI shows promising clinical results for infections for which treatment options are limited.

Epidemiological interpretation of studies examining the effect of antibiotic usage on resistance.

Bacterial resistance to antibiotics is a growing clinical problem and public health threat. Antibiotic use is a known risk factor for the emergence of antibiotic resistance, but demonstrating the causal link between antibiotic use and resistance is challenging. This review describes different study designs for assessing the association between antibiotic use and resistance and discusses strengths and limitations of each. Approaches to measuring antibiotic use and antibiotic resistance are presented. Important methodological issues such as confounding, establishing temporality, and control group selection are examined.

The Yield of One vs. Two Blood Cultures in Children: Under-Detection and Over-Testing.

We aimed to determine whether obtaining two blood cultures (BCs) instead of one improved the detection of bloodstream infections (BSIs) in children. For this descriptive study, we used surveillance data collected in 2019-2021 from all Israeli hospitals serving children. The sample included 178,702 culturing episodes. One BC was taken in 90.1% of all episodes and 98.2% of episodes in the emergency department. A true pathogen was detected in 1687/160,964 (1.0%) of single-culture episodes and 1567/17,738 (8.9%) of two-culture episodes (p < 0.001). The yield was significantly different even when considering only the first BC in two-culture episodes: 1.0% vs. 7.5%. Among 1576 two-culture episodes that were positive for a true pathogen, the pathogen was detected only in the second culture in 252 (16.0%). We estimated that if a second culture had been taken in all episodes, an additional 343 BSIs by a true pathogen would have been detected. Among 1086 two-culture episodes with commensal bacteria, the second BC was sterile in 530 (48.8%), suggesting contamination. A commensal was isolated in 3094/4781 (64.7%) positive single-culture episodes, which could represent BSI or contamination. The yield of a single BC bottle was low, reflecting both lower sensitivity of a single bottle and the taking of single bottles in patients with a low probability of BSI.

Zophobas morio larvae as a novel model for the study of Acinetobacter virulence and antimicrobial resistance.

The use of mammalian models for in vivo testing of bacterial virulence raises ethical concerns and is expensive and time-consuming. As an alternative, non-mammalian models are sought. Galleria mellonella larvae have been used as a model to study several bacterial pathogens. However, their maintenance is challenging, and commercial supply is low. In this study, we aimed to establish the Zophobas morio larvae as an alternative non-mammalian model for the evaluation of the pathogenicity and antimicrobial susceptibility of Acinetobacter baumannii. We infected Z. morio with Acinetobacter strains and determined the optimal temperature and inoculum. To visualize the bacterial distribution within the larvae, hematoxylin and eosin (H&E) staining was performed. Next, a survival model of infected larvae was established, and virulence was compared between strains. The effect of antimicrobial treatment in relation to antibiotic susceptibility was studied. Our results demonstrate that Z. morio can be used as a model system for in vivo studies of A. baumannii.

Carbapenem-resistant Acinetobacter baumannii carrier detection: a simple and efficient protocol.

Timely detection of carbapenem-resistant Acinetobacter baumannii (CRAB) carriers is essential to direct infection control measures. In this work, we aimed to develop a practical protocol to detect CRAB from screening samples. To choose a selective medium that detects CRAB with high sensitivity and specificity, 111 A. baumannii clinical isolates were inoculated on three types of agar: mSuperCARBA (SC), CHROMagar Acinetobacter (CaA), and modified CHROMagar Acinetobacter (mCaA) containing 4.5 mg/mL meropenem. SC was non-selective, CaA was the most sensitive (100%), but only moderately specific (72%), and mCaA was highly specific (97%) and sensitive (98%). Confirmation of the carbapenem-resistant phenotype using PCR-based detection of blaOXA-23, blaOXA-24, and blaOXA-58 genes was specific but not sensitive, detecting only 58% of CRAB isolates. Identification of A. baumannii using either gyrB or blaOXA-51 PCR was excellent. Next, we used the same methodology in routine screening for CRAB carriage. mCaA had the best yield, with high sensitivity but moderate specificity to differentiate between CRAB and other carbapenem-resistant organisms. Skin sampling using sponges and 6 hour enrichment was highly sensitive (98%), while other body sites had poor sensitivity (27%- 41%). Shorter incubation had slightly lower yield, and longer incubation did not improve the detection. Performing PCR for blaOXA-51 and gyrB on colonies growing on modified mCaA differentiated between CRAB and other species with high accuracy (98% and 99%, respectively). Based on our results, we present a procedure for easy and reliable detection of CRAB carriage using skin sampling, short enrichment, selection on mCaA, and PCR-based identification. IMPORTANCE: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a substantial cause of nosocomial infections, classified among the most significant multidrug-resistant pathogens by the World Health Organization and by the US Centers for Disease Control. Limiting the spread of CRAB is an important goal of infection control, but laboratory methods for identification of CRAB carriers are not standardized. In this work, we compared different selective agar plates, tested the efficiency of A. baumannii identification by PCR for species-specific genes, and used PCR-based detection of common resistance genes to confirm the carbapenem-resistant phenotype. During a prospective study, we also determined the optimal sample enrichment time. Based on our results, we propose a simple and efficient protocol for the detection of CRAB carriage using skin sampling, short enrichment, selection on appropriate agar plates, and PCR-based identification, resulting in a turn-around time of 24 hours.