Characteristics of the Genetic Spread of Carbapenem-Resistant Acinetobacter baumannii in a Tertiary Greek Hospital

Acinetobacter baumannii (Ab) has increasingly been identified as a cause of hospital-acquired infections and epidemics. The rise of carbapenem-resistant Acinetobacter baumannii (CRAB) poses significant challenges in treatment. Nosocomial outbreaks linked to CRAΒ A. baumannii strains have been reported worldwide, including in Greece. This study aimed to analyze the molecular epidemiology trends of multidrug-resistant A. baumannii isolates in a tertiary hospital in Athens, Greece. A total of 43 clinical isolates of extensively drug-resistant (XDRAB), pan-drug-resistant (PDRAB), and CRAB were collected from patients suffering from blood infection, hospitalized between 2016 and 2020 at the internal medicine clinics and the ICU. A.baumannii isolates underwent testing for Ambler class B and D carbapenemases and the detection of ISAba1, and were typed, initially, using pulsed-field gel electrophoresis, and, subsequently, using sequence-based typing and multiplex PCR to determine European Clone lineages. The blaOXA-23 gene accompanied by ISAba1 was prevalent in nearly all A. baumannii isolates, except for one carrying blaOXA-58. The intrinsic blaOXA-51-like gene was found in all isolates. No Ambler class B carbapenemases (VIM, NDM) were detected. Isolates were grouped into four PF-clusters and no one-cluster spread was documented, consistent with the absence of outbreak. The study indicated that XDR/PDR-CRAB isolates predominantly produce OXA-23 carbapenemase and belong to European Clone II. Further research is needed to understand the distribution of resistant bacteria and develop effective prevention and control strategies.

In vitro activities of omadacycline, eravacycline, cefiderocol, apramycin, and comparator antibiotics against Acinetobacter baumannii causing bloodstream infections in Greece, 2020-2021: a multicenter study

Resistance of Acinetobacter baumannii to multiple clinically important antimicrobials has increased to very high rates in Greece, rendering most of them obsolete. The aim of this study was to determine the molecular epidemiology and susceptibilities of A. baumannii isolates collected from different hospitals across Greece. Single-patient A. baumannii strains isolated from blood cultures (n = 271), from 19 hospitals, in a 6-month period (November 2020-April 2021) were subjected to minimum inhibitory concentration determination and molecular testing for carbapenemase, 16S rRNA methyltransferase and mcr gene detection and epidemiological evaluation. 98.9% of all isolates produced carbapenemase OXA-23. The vast majority (91.8%) of OXA-23 producers harbored the armA and were assigned mainly (94.3%) to sequence group G1, corresponding to IC II. Apramycin (EBL-1003) was the most active agent inhibiting 100% of the isolates at ≤16 mg/L, followed by cefiderocol which was active against at least 86% of them. Minocycline, colistin and ampicillin-sulbactam exhibited only sparse activity (S <19%), while eravacycline was 8- and 2-fold more active than minocycline and tigecycline respectively, by comparison of their MIC₅₀/₉₀ values. OXA-23-ArmA producing A. baumannii of international clone II appears to be the prevailing epidemiological type of this organism in Greece. Cefiderocol could provide a useful alternative for difficult to treat Gram-negative infections, while apramycin (EBL-1003), the structurally unique aminoglycoside currently in clinical development, may represent a highly promising agent against multi-drug resistant A. baumanni infections, due to its high susceptibility rates and low toxicity.

In vitro activity of ceftolozane/tazobactam alone and in combination with amikacin against MDR/XDR Pseudomonas aeruginosa isolates from Greece

OBJECTIVES

We evaluated the in vitro activity of ceftolozane/tazobactam and comparator agents against MDR non-MBL Pseudomonas aeruginosa isolates collected from nine Greek hospitals and we assessed the potential synergistic interaction between ceftolozane/tazobactam and amikacin.

METHODS

A total of 160 non-MBL P. aeruginosa isolates collected in 2016 were tested for susceptibility to ceftolozane/tazobactam and seven comparator agents including ceftazidime/avibactam. Time-kill assays were performed for synergy testing using ceftolozane/tazobactam 60 or 7.5 mg/L, corresponding to the peak and trough concentrations of a 1.5 g q8h dose, respectively, in combination with 69 mg/L amikacin, corresponding to the free peak plasma concentration. Synergy was defined as a ≥2 log10 cfu/mL reduction compared with the most active agent.

RESULTS

Overall, ceftolozane/tazobactam inhibited 64.4% of the P. aeruginosa strains at ≤4 mg/L. Colistin was the most active agent (MIC50/90, 0.5/2 mg/L; 96.3% susceptible) followed by ceftazidime/avibactam (MIC50/90, 4/16 mg/L; 80.6% susceptible). GES-type enzymes were predominantly responsible for ceftolozane/tazobactam resistance; 81.6% of the non-producers were susceptible. MICs for the P. aeruginosa isolates selected for synergy testing were 2-32 mg/L ceftolozane/tazobactam and 2-128 mg/L amikacin. The combination of ceftolozane/tazobactam with amikacin was synergistic against 85.0% of all the isolates tested and against 75.0% of the GES producers. No antagonistic interactions were observed.

CONCLUSIONS

Ceftolozane/tazobactam demonstrated good in vitro activity against MDR/XDR P. aeruginosa clinical isolates, including strains with co-resistance to other antipseudomonal drugs. In combination with amikacin, a synergistic interaction at 24 h was observed against 85.0% of P. aeruginosa strains tested, including isolates with ceftolozane/tazobactam MICs of 32 mg/L or GES producers.

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.

Failure of central venous catheter insertion and care bundles in a high central line-associated bloodstream infection rate, high bed occupancy hospital

BACKGROUND

Our hospital has several characteristics different from the settings in which the central venous catheter (CVC) care bundle has been implemented so far, that is, care bundles or protocols are not systematically used, and the prevalence of central line-associated bloodstream infections (CLABSI) is high, as is bed occupancy rate. We examined the effectiveness of CVC care bundles.

METHODS

Modified CVC bundles were implemented across all settings of our hospital. During both phases of the study, we collected data on CLABSI, and we monitored CVC insertion and management practices with direct observation audits.

RESULTS

We have studied 913 CVC insertions (454 in PRE and 459 in POST) for 11,871 catheter-days. The incidence of CLABSI was 8.3 per 1,000 catheter-days PRE, and 7.6 per 1,000 catheter-days POST (incidence rate ratio, 0.92; 95% confidence interval, 0.60-1.40). Compliance with the CVC insertion bundle increased from 8.4%-74.3% (P < .0001). The CVC management bundle compliance also increased from 11.4%-57.7% (P < .0001).

CONCLUSIONS

Despite improved compliance after the intervention, implementation of a modified CVC bundle failed to decrease CLABSI incidence. Higher bundle compliance rates may be necessary for a significant decrease in the incidence of CLABSI, along with the appropriate organizational culture and levels of staffing.

222. Bloodstream Infections by Gram(−) Bacteria in Kidney Transplant Patients: Risk Factors, Incidence and Outcome; Bloodstream Infections by Gram(−) Bacteria in Kidney Transplant Patients: Risk Factors, Incidence and Outcome

Background

Kidney transplant recipients are at increased risk for infections. The aims of this study were: i) to estimate the incidence of bloodstream infections (BSI) caused by Gram(−) bacteria in kidney transplant recipients, ii) to identify risk factors for BSI by multidrug-resistant Gram(−) bacteria, and iii) to identify predictors for outcome (death/loss of transplanted kidney).

Methods

We conducted a retrospective cohort study at the renal transplant unit (RTU) of a tertiary care hospital located in Athens, Greece, between September 2008 and September 2018. Kidney transplant recipients with Gram(−) BSIs were identified from the microbiology laboratory electronic records. Patient-, infection-, and treatment-related factors were extracted from the medical records. Species identification and susceptibility testing were performed by MicroScan automated system. The statistical analysis was performed using IBM SPSS Statistics v20.

Results

During the study period, 1962 kidney transplant patients were followed at our RTU. A total of 195 BSI episodes were recorded in 182 patients (male/female=97/85), with median (25th, 75th) age 57.2 (44, 64.9) years. The incidence of BSI was 1.393/100 patient-years. Median (25^th, 75^th) time interval between transplantation date and onset of BSI was 67.67 (8.3, 148) months. Escherichia coli was the most common cause (64.3%, 117/182), while the most common source of infection was urinary tract (70.9%, 129/182). 19.2% (53/182) of BSIs were caused by multidrug-resistant organisms (MDR). 6% (11/182) of patients died and 2.2% (4/182) were subjected to nephrectomy. Multivariate logistic regression showed that diabetes mellitus (odds ratio [OR] 7.714; 95% confidence interval [CI] 1.311–45.385), Pseudomonas aeruginosa BSI (OR 35.788; CI 3.3–388.182) and septic shock (OR 74.468; CI 3.513–1578.513) were predictors of an unfavorable outcome. Previous antibiotic use (OR 11.964; CI 2.686–53.293) and previous stay in Intensive Care Unit (OR 18.055; CI 1.046–311.536) were associated with MDR BSIs.

Conclusion

BSIs in kidney transplant recipients is a critical factor of morbidity and mortality. Recognizing the risk factors for unfavorable outcome and emergence of MDR bacteria could offer a significant advantage in early diagnosis and appropriate treatment.

Disclosures

All authors: No reported disclosures.

Changes in the rates and population structure of methicillin-resistant Staphylococcus aureus (MRSA) from bloodstream infections: A single-centre experience (2000-2015)

OBJECTIVES

The aim of this study was to assess the rate of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) and the population structure of MRSA isolates recovered between 2000-2015 in a tertiary-care hospital in Athens, Greece.

METHODS

Non-duplicate MRSA blood isolates recovered during the study period were examined. Antimicrobial susceptibility testing was performed by Kirby-Bauer and gradient strip methods. Carriage of PVL and mecA genes was examined by PCR. Genetic relatedness of the isolates was studied by SCCmec, spa and multilocus sequence typing.

RESULTS

A total of 398 MRSA BSI cases were identified. A decreasing trend in incidence from 1.69/10 000 patient-days in 2000 to 1.39/10 000 patient-days in 2015 (P=0.038) and in prevalence from 64.7% to 36.4% (P=0.008), respectively, was observed, whereas the incidence of methicillin-susceptible S. aureus BSI increased. MRSA isolates exhibiting resistance to common antistaphylococcal agents (excluding glycopeptides and the newer antistaphylococcals) decreased from 84.8% in 2000 to 0% in 2011 and were progressively 'replaced' by more susceptible phenotypes. A strong association between antimicrobial resistance phenotype and molecular type was observed. The pandemic HA-MRSA clone ST239-III progressively declined in parallel with increasing isolation frequency of two clonal complexes (CCs): HA-MRSA CC5, with the majority of isolates belonging to ST5-II; and CA-MRSA CC80, represented mainly by ST80-IV-t044, PVL+.

CONCLUSION

The decline in MRSA BSI rates observed in our institution was associated with changes in population structure of the organism. This decline may be related to biological properties of the prevailing MRSA clones.

Pre-intensive care unit intubation and subsequent delayed intensive care unit admission is independently associated with increased occurrence of ventilator-associated pneumonia

INTRODUCTION

Critically ill intubated patients are at risk for ventilator-associated pneumonia. However, intubation may not occur in intensive care unit (ICU) and subsequent ICU admission may be delayed.

OBJECTIVES

To evaluate whether intubation >24 h prior ICU admission and delay in ICU admission is associated with ventilator-associated pneumonia (VAP) in non-trauma critically ill patients.

MATERIALS AND METHODS

Prospective observational study conducted in a medical-surgical ICU of a tertiary hospital. Consecutive patients with >48 h of invasive mechanical ventilation and >72 h hospitalization, were recruited in the study. Pre-ICU intubation and delay in ICU admission, demographical, clinical, microbiological data and ICU interventions were assessed as risk factors for VAP and ICU mortality.

RESULTS

100 patients were included in the study. Pre-ICU intubation and delayed (>24 h) ICU admission (PDA patients) (P = 0.014, OR = 3.294, confidence interval 1.268-8.557) and SOFA score on ICU admission (P = 0.045, OR = 1.154, confidence interval 1.003-1.328) were independent risk factors for VAP in ICU care setting. Yet, PDA patients, presented significantly increased incidence of VAP due to MDR bacteria, mainly from Acinetobacter baumannii. Acinetobacter baumannii infection was the only independent risk factor for ICU mortality (P = 0.049, OR = 3.253, confidence interval 1.006-10.521). SOFA score on ICU admission, presented a fair prognostic accuracy of overall ICU mortality (SOFA ≥ 8.5, AUC = 0.850, P < 0.001).

CONCLUSIONS

Pre-ICU intubation and delayed ICU admission was independent risk factor for VAP Acinetobacter baumannii infection and a high SOFA score on ICU admission were predictors of increased ICU mortality.

Cefditoren: Comparative efficacy with other antimicrobials and risk factors for resistance in clinical isolates causing UTIs in outpatients

BACKGROUND

To investigate a possible role of Cefditoren, a recently marketed in Greece third-generation oral cephalosporin in urinary infections of outpatients.

METHODS

During a multicenter survey of Enterobacteriaceae causing UTIs in outpatients during 2005-2007, Cefditoren MICs were determined by agar dilution method in a randomly selected sample of uropathogens. Susceptibility against 18 other oral/parenteral antimicrobials was determined according to Clinical and Laboratory Standards Institute methodology.

RESULTS

A total of 563 isolates (330 Escherichia coli, 142 Proteus mirabilis and 91 Klebsiella spp) was studied; MIC50/MIC90 of Cefditoren was 0.25/0.5 mg/L respectively, with 97.1% of the isolates being inhibited at 1 mg/L. All 12 strains producing ESBLs or AmpC enzymes were resistant to cefditoren. Susceptibility rates (%) for amoxicillin/clavulanic acid, cefuroxime axetil, cefotaxime, ciprofloxacin, trimethoprim/sulfamethoxazole and fosfomycin were 93.1- 94.1- 96.8-93.1-71.9 and 92.8% respectively. Cefditoren MIC was significantly higher in nalidixic/ciprofloxacin non-susceptible strains; resistance to cefditoren was not associated with resistance to mecillinam, fosfomycin nitrofurantoin and aminoglycosides. Multivariate analysis demonstrated history of urinary infection in the last two weeks or three months as risk factors for cefditoren resistance.

CONCLUSIONS

Cefditoren exhibited enhanced in vitro activity against the most common uropathogens in the outpatient setting, representing an alternative oral treatment option in patients with risk factors for resistance to first-line antibiotics.