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.

Use of Fourier-transform infrared spectroscopy for real-time outbreak investigation of OXA-48-producing Escherichia coli.

BACKGROUND: Efficient infection control during carbapenem-resistant Enterobacterales outbreaks demands rapid and simple techniques for outbreak investigations. WGS, the current gold standard for outbreak identification, is expensive, time-consuming and requires a high level of expertise. Fourier-transform infrared (FTIR) spectroscopy (IR Biotyper) is a rapid typing method based on infrared radiation applied to samples, which provides a highly specific absorption spectrum. OBJECTIVES: To investigate an outbreak of OXA-48-producing Escherichia coli in real-time using FTIR and subsequently compare the results with WGS. METHODS: Twenty-one isolates were collected during a nosocomial outbreak, and identification and antibiotic susceptibilities were confirmed by VITEK®2. FTIR was conducted for all isolates, and nine representative isolates were sequenced. RESULTS: FTIR was able to correctly determine the clonal relatedness of the isolates and to identify the outbreak cluster, as confirmed by WGS. By WGS, isolates in the main FTIR cluster belonged to the same MLST type and core-genome MLST type, and they harboured similar plasmids and resistance genes, whereas the singletons external to the FTIR cluster had different genetic content. CONCLUSIONS: FTIR can operate as a rapid, efficient and reliable first-line tool for outbreak investigations during a real-time ongoing E. coli outbreak, which can contribute to limiting the spread of pathogens.

Global incidence in hospital-associated infections resistant to antibiotics: An analysis of point prevalence surveys from 99 countries.

BACKGROUND: Hospital-associated infections (HAIs) are an important cause of morbidity and mortality around the world. Many HAIs are caused by drug-resistant bacterial pathogens, but there are major gaps in our understanding of the number of hospital-associated drug-resistant infections (HARIs) worldwide. As such, we estimated trends in prevalence of HARIs caused by high priority pathogens (Escherichia coli, Acinetobacter spp., Klebsiella spp., Staphylococcus aureus, Enterobacter spp., and Pseudomonas spp.) in 195 countries. METHODS AND FINDINGS: Resistance prevalence estimates were extracted from 474-point prevalence surveys (PPS) from 99 countries published between 2010 and 2020 coupled with country-level estimates of hospitalization rates and length of stay. Prevalence estimates were transformed in yearly incidence of HARIs per year by country and income group. We estimate the global number of HARIs per year to be 136 million (95% credible interval (CI) 26 to 246 million) per year, with the highest burden in China (52 million, 95% CI 10 to 95 million), Pakistan (10 million, 95% CI 2 to 18 million), and India (9 million, 95% CI 3 to 15 million). Among income groups, middle-income countries bore the highest burden of HARIs per year (119 million, 95% CI 23 to 215 million). Our analysis was constrained by the limited number of PPS for HARIs, lack of community-associated data on antibiotic-resistant infections, and our population level analysis. CONCLUSIONS: In this study, we observe, in the absence of systematic surveillance systems for HARIs, a baseline overview of their rates. Our yearly estimates highlight the global threat of HARIs and may help define strategies to tackle resistance in hospital settings.

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.

Healthcare-associated infection prevention and control practices in Israel: results of a national survey.

BACKGROUND: Healthcare-associated infection (HAI) is a common and largely preventable cause of morbidity and mortality. The COVID-19 pandemic has presented unprecedented challenges to health systems. We conducted a national survey to ascertain hospital characteristics and the use of HAI prevention measures in Israel. METHODS: We e-mailed surveys to infection prevention and control (IPC) leads of acute care hospitals in Israel. The survey included questions about the use of practices to prevent catheter-associated urinary tract infection (CAUTI), central line-associated bloodstream infection (CLABSI), ventilator-associated pneumonia (VAP), and Clostridioides difficile infection (CDI). The survey also assessed COVID-19 impact and healthcare worker well-being. RESULTS: IPC leads from 15 of 24 invited hospitals (63%) completed the survey. Only one-third of respondents reported strong support for IPC from hospital leadership. Although several prevention practices were used by all hospitals (e.g., maximum sterile barrier precautions for CLABSI and real-time assessment of environmental cleaning for CDI), use of other practices was suboptimal-particularly for CAUTI and VAP. COVID-19 had a profound impact on Israeli hospitals, with all hospitals reporting opening of new units to care for COVID patients and most reporting moderate to extreme financial hardship. All hospitals reported highly successful plans to vaccinate all staff and felt confident that the vaccine is safe and effective. CONCLUSION: We provide a status report of the IPC characteristics and practices Israeli hospitals are currently using to prevent HAIs during the COVID-19 era. While many globally accepted IPC practices are widely implemented, opportunities to increase the use of certain IPC practices in Israeli hospitals exist.

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.

Elevated MICs of Susceptible Antipseudomonal Cephalosporins in Non-Carbapenemase-Producing, Carbapenem-Resistant Pseudomonas aeruginosa: Implications for Dose Optimization.

The present study evaluated the in vitro potency of ceftazidime and cefepime among carbapenem-resistant Pseudomonas aeruginosa isolates collected as part of a global surveillance program and assessed the pharmacodynamic implications using previously published population pharmacokinetics. When susceptible, MICs resulted at the high end of distribution for both ceftazidime and cefepime, thus 6 g/day was required to achieve optimal pharmacodynamic profiles. These findings should be considered in the clinic and for the application of CLSI susceptibility breakpoints.

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.

Citrobacter telavivum sp. nov. with chromosomal mcr-9 from hospitalized patients.

Strains 6105T and 6106, recovered from colonized patients in a hospital in Tel-Aviv, Israel, were compared with currently known species of the genus Citrobacter by a polyphasic taxonomic approach. Strains were characterized by whole-genome sequencing, 16S rRNA and recN gene sequencing, multilocus sequence analysis (MLSA), average nucleotide identity (ANI), Genome-to-Genome Distance Calculator (GGDC), and biochemical tests. The location and genetic surrounding of antibiotic resistance genes were investigated, and antibiotic susceptibility profiles were determined by broth microdilution or agar dilution methods. Phylogenetic analysis based on recN and MLSA revealed that both strains formed a distinct cluster from all currently recognized species. The ANI and GGDC were 90.7% and 54.3% with Citrobacter farmeri, respectively. The ability to metabolize various compounds also differentiated both strains from closely related Citrobacter species. Chromosomes of the isolates contained locus encoding a novel class A ß-lactamase (TEL-1; 90.5% amino acid identity with CdiA of Citrobacter koseri) plus a LysR-like transcriptional regulator (TEL-R) and an ~ 25.5-kb mcr-9 mosaic region. The direct mcr-9 context matched with those previously identified in several plasmids and chromosomes of diverse Enterobacteriaceae, yet similarity with the plasmidic loci extended further. Untypeable plasmids, pCTEL-2 (~ 235 kb) and pCTEL-1 (~ 114 kb), devoid of resistance genes, were identified in the strains. The isolates were non-susceptible to ß-lactams. The name Citrobacter telavivum sp. nov. is proposed, with 6105T (CECT 9989T or DSM 110286T) as the type strain. C. telavivum may represent a bacterial species adapting to hospital settings, able to disseminate and acquire antimicrobial resistance genes.

The ERACE-PA Global Surveillance Program: Ceftolozane/tazobactam and Ceftazidime/avibactam in vitro Activity against a Global Collection of Carbapenem-resistant Pseudomonas aeruginosa.

The cephalosporin-ß-lactamase-inhibitor-combinations, ceftolozane/tazobactam and ceftazidime/avibactam, have revolutionized treatment of carbapenem-resistant Pseudomonas aeruginosa (CR-PA). A contemporary assessment of their in vitro potency against a global CR-PA collection and an assessment of carbapenemase diversity are warranted. Isolates determined as CR-PA by the submitting site were collected from 2019-2021 (17 centers in 12 countries) during the ERACE-PA Global Surveillance Program. Broth microdilution MICs were assessed per CLSI standards for ceftolozane/tazobactam, ceftazidime/avibactam, ceftazidime, and cefepime. Phenotypic carbapenemase testing was conducted (modified carbapenem inactivation method (mCIM)). mCIM positive isolates underwent genotypic carbapenemase testing using the CarbaR, the CarbaR NxG, or whole genome sequencing. The MIC50/90 was reported as well as percent susceptible (CLSI and EUCAST interpretation). Of the 807 isolates, 265 (33%) tested carbapenemase-positive phenotypically. Of these, 228 (86%) were genotypically positive for a carbapenemase with the most common being VIM followed by GES. In the entire cohort of CR-PA, ceftolozane/tazobactam and ceftazidime/avibactam had MIC50/90 values of 2/ > 64 and 4/64 mg/L, respectively. Ceftazidime/avibactam was the most active agent with 72% susceptibility per CLSI compared with 63% for ceftolozane/tazobactam. For comparison, 46% of CR-PA were susceptible to ceftazidime and cefepime. Against carbapenemase-negative isolates, 88 and 91% of isolates were susceptible to ceftolozane/tazobactam and ceftazidime/avibactam, respectively. Ceftolozane/tazobactam and ceftazidime/avibactam remained highly active against carbapenem-resistant P. aeruginosa, particularly in the absence of carbapenemases. The contemporary ERACE-PA Global Program cohort with 33% carbapenemase positivity including diverse enzymology will be useful to assess therapeutic options in these clinically challenging organisms with limited therapies.

Excluded versus included patients in a randomized controlled trial of infections caused by carbapenem-resistant Gram-negative bacteria: relevance to external validity.

BACKGROUND: Population external validity is the extent to which an experimental study results can be generalized from a specific sample to a defined population. In order to apply the results of a study, we should be able to assess its population external validity. We performed an investigator-initiated randomized controlled trial (RCT) (AIDA study), which compared colistin-meropenem combination therapy to colistin monotherapy in the treatment of patients infected with carbapenem-resistant Gram-negative bacteria. In order to examine the study's population external validity and to substantiate the use of AIDA study results in clinical practice, we performed a concomitant observational trial. METHODS: The study was conducted between October 1st, 2013 and January 31st, 2017 (during the RCTs recruitment period) in Greece, Israel and Italy. Patients included in the observational arm of the study have fulfilled clinical and microbiological inclusion criteria but were excluded from the RCT due to receipt of colistin for > 96 h, refusal to participate, or prior inclusion in the RCT. Non-randomized cases were compared to randomized patients. The primary outcome was clinical failure at 14 days of infection onset. RESULTS: Analysis included 701 patients. Patients were infected mainly with Acinetobacter baumannii [78.2% (548/701)]. The most common reason for exclusion was refusal to participate [62% (183/295)]. Non-randomized and randomized patients were similar in most of the demographic and background parameters, though randomized patients showed minor differences towards a more severe infection. Combination therapy was less common in non-randomized patients [31.9% (53/166) vs. 51.2% (208/406), p = 0.000]. Randomized patients received longer treatment of colistin [13 days (IQR 10-16) vs. 8.5 days (IQR 0-15), p = 0.000]. Univariate analysis showed that non-randomized patients were more inclined to clinical failure on day 14 from infection onset [82% (242/295) vs. 75.5% (307/406), p = 0.042]. After adjusting for other variables, non-inclusion was not an independent risk factor for clinical failure at day 14. CONCLUSION: The similarity between the observational arm and RCT patients has strengthened our confidence in the population external validity of the AIDA trial. Adding an observational arm to intervention studies can help increase the population external validity and improve implementation of study results in clinical practice. TRIAL REGISTRATION: The trial was registered with ClinicalTrials.gov, number NCT01732250 on November 22, 2012.

Multiplex lateral flow immunochromatographic assay is an effective method to detect carbapenemases without risk of OXA-48-like cross reactivity.

BACKGROUND: It is essential to detect carriers of carbapenemase-producing Enterobacterales in order to implement infection control measures. The objectives of this study was to evaluate the NG-Test® CARBA 5 (CARBA 5) assay for detection of five carbapenemases and to assess the cross reactivity of other OXA-type carbapenemases with the OXA-48-like specific antibodies. METHODS: A total of 197 Enterobacterales isolates were tested. To evaluate the cross reactivity, 73 carbapenem-resistant A. baumannii, harboring OXA-type variants, were tested. Polymerase chain reaction (PCR) served as gold standard for carbapenemase identification. RESULTS: Excellent agreement was found between PCR and CARBA 5, for all but one isolate. The single false positive result (a blaSME positive S. marcescens isolate) was incorrectly positive for blaOXA-48 by CARBA 5. No cross reactivity was observed. The sensitivity and specificity were 100.0% and 98.0%, respectively. CONCLUSIONS: The CARBA 5 assay is highly sensitive and specific and is recommended as a tool for the detection of the main carbapenemases of interest in clinical microbiology laboratories.

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.

Colistin Resistance Development Following Colistin-Meropenem Combination Therapy Versus Colistin Monotherapy in Patients With Infections Caused by Carbapenem-Resistant Organisms.

BACKGROUND: We evaluated whether carbapenem-colistin combination therapy reduces the emergence of colistin resistance, compared to colistin monotherapy, when given to patients with infections due to carbapenem-resistant Gram-negative organisms. METHODS: This is a pre-planned analysis of a secondary outcome from a randomized, controlled trial comparing colistin monotherapy with colistin-meropenem combination for the treatment of severe infections caused by carbapenem-resistant, colistin-susceptible Gram-negative bacteria. We evaluated rectal swabs taken on Day 7 or later for the presence of new colistin-resistant (ColR) isolates. We evaluated the emergence of any ColR isolate and the emergence of ColR Enterobacteriaceae (ColR-E). RESULTS: Data were available for 214 patients for the primary analysis; emergent ColR organisms were detected in 22 (10.3%). No difference was observed between patients randomized to treatment with colistin monotherapy (10/106, 9.4%) versus patients randomized to colistin-meropenem combination therapy (12/108, 11.1%; P = .669). ColR-E organisms were detected in 18/249 (7.2%) patients available for analysis. No difference was observed between the 2 treatment arms (colistin monotherapy 6/128 [4.7%] vs combination therapy 12/121 [9.9%]; P = .111). Enterobacteriaceae, as the index isolate, was found to be associated with development of ColR-E (hazard ratio, 3.875; 95% confidence interval, 1.475-10.184; P = .006). CONCLUSIONS: Carbapenem-colistin combination therapy did not reduce the incidence of colistin resistance emergence in patients with infections due to carbapenem-resistant organisms. Further studies are necessary to elucidate the development of colistin resistance and methods for its prevention.

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.

Performance of Rapid Polymyxin™ NP and Rapid Polymyxin™ Acinetobacter for the detection of polymyxin resistance in carbapenem-resistant Acinetobacter baumannii and Enterobacterales.

BACKGROUND: The global spread of carbapenem-resistant Enterobacterales (CRE) and Acinetobacter baumannii (CRAB) has prompted the reintroduction of colistin as a last-resort treatment. Although the recommended method for colistin susceptibility testing is broth microdilution (BMD), methods that are more rapid and easy to use are needed. OBJECTIVES: To evaluate the performance of two commercial kits for colistin susceptibility testing: Rapid Polymyxin™ NP (RP-NP) for CRE and Rapid Polymyxin™ Acinetobacter (RP-AB) for CRAB. METHODS: A total of 76 CRE and 87 CRAB isolates were collected from hospitalized patients in Europe and Israel. The isolates were subcultured twice on 5% sheep blood in tryptic soy agar. We tested colistin susceptibility using the RP-NP and RP-AB kits and compared the results with those from BMD. RESULTS: Of the CRE isolates, 25% (19/76) were resistant to colistin using BMD. Categorical agreement between RP-NP and BMD was 93.4% (71/76), major errors 1.8% (1/57) and very major errors 21.1% (4/19). Sensitivity was 78.9% and specificity was 98.2%. Of the CRAB isolates, 58.6% (51/87) were resistant to colistin by BMD. Categorical agreement between RP-AB and BMD was 59.8% (52/87), major errors 13.9% (5/36) and very major errors 58.8% (30/51). Sensitivity of RP-AB was 41.2% and specificity was 86.1%. CONCLUSIONS: In many of the tested isolates, weak or inconclusive colour changes in the test wells caused difficulty in interpretation, resulting in an unacceptable rate of very major errors.

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.