Bacterial genotypic and patient risk factors for adverse outcomes in Escherichia coli bloodstream infections: a prospective molecular epidemiological study

Serum phosphate and 28-day mortality in adult sepsis with E.Coli infection: A critical care database study

OBJECTIVE

In this study, we aimed to explore the relationship between serum phosphate and clinical outcomes in sepsis with E.Coli infection based on a public database in order to help physicians do individualized medical decisions.

METHODS

We performed this retrospective study based on the Medical Information Mart for Intensive Care IV(MIMIC-IV) database (https://mimic.mit.edu/iv/). All the patients were hospitalized and serum phosphate was measured in 24 hours after hospitalization. E.Coli infection was confirmed by the positive blood culture of E.Coli in the database. Three models were utilized to investigate the relationship between serum phosphate and mortality in sepsis as follows: crude model (adjusted for none), model I (adjusted for age and gender) and model II (adjusted for all potential confounders). The smooth fitting curve was performed by the generalized additive model.

RESULTS

421 adult sepsis patients with E.Coli infection were included. The 28-day mortality was 10.69%(n=45). The median age was 70 and the proportion of males was 47.51%(n=200). The smooth fitting curve showed that the relationship between serum phosphate and 28-day mortality in sepsis with E.Coli infection was positive. When serum phosphate >2.1mg/dl, the relationship was significantly positive (OR=1.55, 95%CI:1.01-2.36, P=0.043).

CONCLUSION

The positive relationship between serum phosphate and 28-day mortality in adult sepsis patients with E.Coli infection was found based on MIMIC-IV database.

Prevalence and characteristics of ST131-O16 and ST131-O25b clones among extended-spectrum β-lactamase-producing Escherichia coli isolates causing bloodstream infection in Iran

BACKGROUND

The multidrug-resistant clone identified as Escherichia coli sequence type 131 (E. coli ST131) has spread worldwide. The current study is one of the first comprehensive investigations to ascertain the prevalence of ST131 and molecularly characterize the ST131-O25b and ST131-O16 subgroups causing bloodstream infections in Iran.

METHODS AND RESULTS

To this end, 119 consecutive, non-repetitive E. coli clinical strains were isolated from blood samples of patients with septicemia in different hospital wards for one year in Tehran. The isolates were provided by the laboratories of tertiary hospitals affiliated with Tehran University of Medical Sciences. The disk diffusion method was used to investigate the sensitivity of bacteria to antibiotics. All phylogroup B2 isolates were screened for E. coli ST131 status using a triplex PCR assay that combines the identification of ST131-O25b and -O16 clades. The seven putative virulence factor genes (kpmstII, fimH, afa A, iroN, Sat, ibeA, and ompT) and resistance genes (blaCTX-M-15, blaOXA-48, and blaCMY) were detected by PCR in E. coli ST131 isolates.

CONCLUSIONS

The highest incidence of antibiotic resistance among 74/119 (62.18%) extended-spectrum β-lactamases-producing E. coli isolates was observed, respectively, against Nalidixic acid (82%), and Aztreonam (75%), followed by Ciprofloxacin (70%). Twenty out of 74 ESBL-producing E. coli isolates were found to be ST131 (27%), with 13 (65%) ST131-O25b and 7 (35%) ST131-O16 clades, respectively. The ST131-O16 isolates had a higher prevalence of resistance to Ceftriaxone, Amikacin, Aztreonam, and Cefepime than the -O25b ones. Concerning virulence capacity, our findings demonstrated that kpmstII, fimH, and ompT genes were found in 85%, 65%, and 30% of ST131 isolates, respectively. Our results reinforce the surveillance of E. coli ST131 clone dissemination as a major drug-resistant pathogen and an important new public health threat in Iran. Accumulation of multiple virulence factors, ESBL carriage, and identified antimicrobial resistance patterns of ST131-O25b and ST131-O16 clones indicate a necessity to develop strategies to control the spread of these isolates in both community and hospital settings.

Genomic and growth fitness study of extended-spectrum β-lactamase-producing Escherichia coli from bloodstream infections after introduction of a national 4C antimicrobial stewardship policy in Scotland

BACKGROUND

Extended-spectrum β-lactamase-producing Escherichia coli remains a major cause of hospital-acquired bloodstream infections in countries with high antimicrobial stewardship compliance.

METHODS

Isolates from bloodstream infections that occurred between 2010 and 2020 in a tertiary-level hospital in North-East Scotland soon after introduction of the '4C' antimicrobial stewardship policy were analysed for phylogenetic structure, antimicrobial resistance, plasmid, and virulence gene carriage. Growth fitness was measured in kinetic assays. Non-metric-multidimensional-scaling was used to evaluate clonal relationships, antimicrobial resistance, and virulence profiles in early and later years after the 4C policy introduction. Clonal and fitness trends over the study period were determined by generalised additive modelling. The relationship between clonal type, antimicrobial resistance, and fitness was evaluated by linear regression.

RESULTS

Three hierarchical phylogenetic clusters were identified, with the most dominant cluster (O25:H4/fimH30) including all, and nearly exclusively, Clade C ST131 isolates as well as minor non-ST131 sequence types. The prevalence of ST131 was largely stable over the study period. Resistance to aminoglycosides and aztreonam in ST131 was lower (P = 0.019 and P = 0.004, respectively) during later years (2016-2020) by 28% on average compared to early years soon after 4C policy implementation (2010-2014). Carriage of virulence factors involved in bacterial adaptation was higher in ST131 compared to non-ST131 but mostly stable in early vs. later years. Growth fitness of ST131 was lower than non-ST131 and declined steadily in later years (P < 0.0001).

CONCLUSIONS

Despite stable virulence factor carriage, population structure, and resistance to cephalosporins, we show increased susceptibility of ST131 to aminoglycosides and aztreonam and concurrent fitness decline years after the introduction of the 4C policy.

Association of microbiological factors with mortality in Escherichia coli bacteraemia presenting with sepsis/septic shock: a prospective cohort study

OBJECTIVES

This study aimed to determine the association of Escherichia coli microbiological factors with 30-day mortality in patients with bloodstream infection (BSI) presenting with a dysregulated response to infection (i.e. sepsis or septic shock).

METHODS

Whole-genome sequencing was performed on 224 E coli isolates of patients with sepsis/septic shock, from 22 Spanish hospitals. Phylogroup, sequence type, virulence, antibiotic resistance, and pathogenicity islands were assessed. A multivariable model for 30-day mortality including clinical and epidemiological variables was built, to which microbiological variables were hierarchically added. The predictive capacity of the models was estimated by the area under the receiver operating characteristic curve (AUROC) with 95% confidence intervals (CI).

RESULTS

Mortality at day 30 was 31% (69 patients). The clinical model for mortality included (adjusted OR; 95% CI) age (1.04; 1.02-1.07), Charlson index ≥3 (1.78; 0.95-3.32), urinary BSI source (0.30; 0.16-0.57), and active empirical treatment (0.36; 0.11-1.14) with an AUROC of 0.73 (95% CI, 0.67-0.80). Addition of microbiological factors selected clone ST95 (3.64; 0.94-14.04), eilA gene (2.62; 1.14-6.02), and astA gene (2.39; 0.87-6.59) as associated with mortality, with an AUROC of 0.76 (0.69-0.82).

DISCUSSION

Despite having a modest overall contribution, some microbiological factors were associated with increased odds of death and deserve to be studied as potential therapeutic or preventive targets.

Whole-genome characterisation of Escherichia coli isolates from patients with bacteraemia presenting with sepsis or septic shock in Spain: a multicentre cross-sectional study

BACKGROUND

Escherichia coli is the most frequent cause of bloodstream infections (BSIs). About one-third of patients with BSIs due to E coli develop sepsis or shock. The objective of this study is to characterise the microbiological features of E coli blood isolates causing sepsis or septic shock to provide exploratory information for future diagnostic, preventive, or therapeutic interventions.

METHODS

E coli blood isolates from a multicentre cross-sectional study of patients older than 14 years presenting with sepsis or septic shock (according to the Third International Consensus Definitions for Sepsis and Septic Shock criteria) from hospitals in Spain between Oct 4, 2016, and Oct 15, 2017, were studied by whole-genome sequencing. Phylogroups, sequence types (STs), serotype, FimH types, antimicrobial resistance (AMR) genes, pathogenicity islands, and virulence factors were identified. Susceptibility testing was performed by broth microdilution. The main outcome of this study was the characterisation of the E coli blood isolates in terms of population structure by phylogroups, groups (group 1: phylogroups B2, F, and G; group 2: A, B1, and C; group 3: D), and STs and distribution by geographical location and bloodstream infection source. Other outcomes were virulence score and prevalence of virulence-associated genes, pathogenicity islands, AMR, and AMR-associated genes. Frequencies were compared using χ² or Fisher's exact tests, and continuous variables using the Mann-Whitney test, with Bonferroni correction for multiple comparisons.

FINDINGS

We analysed 224 isolates: 140 isolates (63%) were included in phylogenetic group 1, 52 (23%) in group 2, and 32 (14%) in group 3. 85 STs were identified, with four comprising 44% (n=98) of the isolates: ST131 (38 [17%]), ST73 (25 [11%]), ST69 (23 [10%]), and ST95 (12 [5%]). No significant differences in phylogroup or ST distribution were found according to geographical areas or source of bloodstream infection, except for ST95, which was more frequent in urinary tract infections than in other sources (11 [9%] of 116 vs 1 [1%] of 108, p=0·0045). Median virulence score was higher in group 1 (median 25·0 [IQR 20·5-29·0) than in group 2 (median 14·5 [9·0-20·0]; p<0·0001) and group 3 (median 21 [16·5-23·0]; p<0·0001); prevalence of several pathogenicity islands was higher in group 1. No significant differences were found between phylogenetic groups in proportions of resistance to antibiotics. ST73 had higher median virulence score (32 [IQR 29-35]) than the other predominant clones (median range 21-28). Some virulence genes and pathogenicity islands were significantly associated with each ST. ST131 isolates had higher prevalence of AMR and a higher proportion of AMR genes, notably blaCTX-M-15 and blaOXA-1.

INTERPRETATION

In this exploratory study, the population structure of E coli causing sepsis or shock was similar to previous studies that included all bacteraemic isolates. Virulence genes, pathogenicity islands, and AMR genes were not randomly distributed among phylogroups or STs. These results provide a comprehensive characterisation of invasive E coli isolates causing severe response syndrome. Future studies are required to determine the contribution of these microbiological factors to severe clinical presentation and worse outcomes in patients with E coli bloodstream infection.

FUNDING

Instituto de Salud Carlos III.

Mortality and length of hospital stay after bloodstream infections caused by ESBL-producing compared to non-ESBL-producing E. coli

OBJECTIVE

To compare mortality and length of hospital stay between patients with ESBL-producing E. coli bloodstream infections (BSIs) and patients with non-ESBL E. coli BSIs. We also aimed at describing risk factors for ESBL-producing E. coli BSIs and time to effective antibiotic treatment for the two groups.

METHODS

A retrospective case-control study among adults admitted between 2014 and 2021 to a Norwegian University Hospital.

RESULTS

A total of 468 E. coli BSI episodes from 441 patients were included (234 BSIs each in the ESBL- and non-ESBL group). Among the ESBL-producing E. coli BSIs, 10.9% (25/230) deaths occurred within 30 days compared to 9.0% (21/234) in the non-ESBL group. The adjusted 30-day mortality OR was 1.6 (95% CI 0.7-3.7, p = 0.248). Effective antibiotic treatment was administered within 24 hours to 55.2% (129/234) in the ESBL-group compared to 86.8% (203/234) in the non-ESBL group. Among BSIs of urinary tract origin (n = 317), the median length of hospital stay increased by two days in the ESBL group (six versus four days, p < 0.001). No significant difference in the length of hospital stay was found for other sources of infection (n = 151), with a median of seven versus six days (p = 0.550) in the ESBL- and non-ESBL groups, respectively.

CONCLUSION

There was no statistically significant difference in 30-day mortality in ESBL-producing E. coli compared to non-ESBL E. coli BSI, despite a delay in the administration of an effective antibiotic in the former group. ESBL-production was associated with an increased length of stay in BSIs of urinary tract origin.

IS1-related large-scale deletion of chromosomal regions harbouring the oxygen-insensitive nitroreductase gene nfsB causes nitrofurantoin heteroresistance in Escherichia coli

Nitrofurantoin is a broad-spectrum first-line antimicrobial used for managing uncomplicated urinary tract infection (UTI). Loss-of-function mutations in chromosomal genes nfsA, nfsB and ribE of Escherichia coli are known to reduce nitrofurantoin susceptibility. Here, we report the discovery of nitrofurantoin heteroresistance in E. coli clinical isolates and a novel genetic mechanism associated with this phenomenon. Subpopulations with lower nitrofurantoin susceptibility than major populations (hereafter, nitrofurantoin-resistant subpopulations) in two E. coli blood isolates (previously whole-genome sequenced) were identified using population analysis profiling. Each isolate was known to have a loss-of-function mutation in nfsA. From each isolate, four nitrofurantoin-resistant isolates were derived at a nitrofurantoin concentration of 32 mg l-1, and a comparator isolate was obtained without any nitrofurantoin exposure. Genomes of derived isolates were sequenced on Illumina and Nanopore MinION systems. Genetic variation between isolates was determined based on genome assemblies and read mapping. Nitrofurantoin minimum inhibitory concentrations (MICs) of both blood isolates were 64 mg l-1, with MICs of major nitrofurantoin-susceptible populations varying from 4 to 8 mg l-1. Two to 99 c.f.u. per million demonstrated growth at the nitrofurantoin concentration of 32 mg l-1, which is distinct from that of a homogeneously susceptible or resistant isolate. Derived nitrofurantoin-resistant isolates had 11-66 kb deletions in chromosomal regions harbouring nfsB, and all deletions were immediately adjacent to IS1-family insertion sequences. Our findings demonstrate that the IS1-associated large-scale genetic deletion is a hitherto unrecognized mechanism of nitrofurantoin heteroresistance and could compromise UTI management. Further, frequencies of resistant subpopulations from nitrofurantoin-heteroresistant isolates may challenge conventional nitrofurantoin susceptibility testing in clinical settings.

Virulence Factor Genes in Invasive Escherichia coli Are Associated with Clinical Outcomes and Disease Severity in Patients with Sepsis: A Prospective Observational Cohort Study

BACKGROUND

Escherichia coli harbours virulence factors that facilitate the development of bloodstream infections. Studies determining virulence factors in clinical isolates often have limited access to clinical data and lack associations with patient outcome. The goal of this study was to correlate sepsis outcome and virulence factors of clinical E. coli isolates in a large cohort.

METHODS

Patients presenting at the emergency department whose blood cultures were positive for E. coli were prospectively included. Clinical and laboratory parameters were collected at admission. SOFA-score was calculated to determine disease severity. Patient outcomes were in-hospital mortality and ICU admission. Whole genome sequencing was performed for E. coli isolates and virulence genes were detected using the VirulenceFinder database.

RESULTS

In total, 103 E. coli blood isolates were sequenced. Isolates had six to 41 virulence genes present. One virulence gene, kpsMII_K23, a K1 capsule group 2 of E. coli type K23, was significantly more present in isolates of patients who died. kpsMII_K23 and cvaC (Microcin C) were significantly more frequent in isolates of patients who were admitted to the ICU. Fourteen virulence genes (mchB, mchC, papA_fsiA_F16, sat, senB, iucC, iutA, iha, sfaD, cnf1, focG, vat, cldB, and mcmA) significantly differed between patients with and without sepsis.

CONCLUSIONS

Microcins, toxins, and fimbriae were associated with disease severity. Adhesins and iron uptake proteins seemed to be protective. Two genes were associated with worse clinical outcome. These findings contribute to a better understanding of host-pathogen interactions and could help identifying patients most at risk for a worse outcome.

Oral ciprofloxacin activity against ceftriaxone-resistant Escherichia coli in an in vitro bladder infection model

OBJECTIVES

Pharmacodynamic profiling of oral ciprofloxacin dosing for urinary tract infections caused by ceftriaxone-resistant Escherichia coli isolates with ciprofloxacin MIC ≥ 0.25 mg/L.

BACKGROUND

Urine-specific breakpoints for ciprofloxacin do not exist. However, high urinary concentrations may promote efficacy in isolates with low-level resistance.

METHODS

Ceftriaxone-resistant E. coli urinary isolates were screened for ciprofloxacin susceptibility. Fifteen representative strains were selected and tested using a dynamic bladder infection model. Oral ciprofloxacin dosing was simulated over 3 days (250 mg daily, 500 mg daily, 250 mg 12 hourly, 500 mg 12 hourly and 750 mg 12 hourly). The model was run for 96 h. Primary endpoint was change in bacterial density at 72 h. Secondary endpoints were follow-up change in bacterial density at 96 h and area-under-bacterial-kill-curve. Bacterial response was related to exposure (AUC0-24/MIC; Cmax/MIC). PTA was determined using Monte-Carlo simulation.

RESULTS

Ninety-three clinical isolates demonstrated a trimodal ciprofloxacin MIC distribution (modal MICs at 0.016, 0.25 and 32 mg/L). Fifteen selected clinical isolates (ciprofloxacin MIC 0.25-512 mg/L) had a broad range of quinolone-resistance genes. Following ciprofloxacin exposure, E. coli ATCC 25922 (MIC 0.008 mg/L) was killed in all dosing experiments. Six isolates (MIC ≥ 16 mg/L) regrew in all experiments. Remaining isolates (MIC 0.25-8 mg/L) regrew variably after an initial period of killing, depending on simulated ciprofloxacin dose. A >95% PTA, using AUC0-24/MIC targets, supported 250 mg 12 hourly for susceptible isolates (MIC ≤ 0.25 mg/L). For isolates with MIC ≤ 1 mg/L, 750 mg 12 hourly promoted 3 log10 kill at the end of treatment (72 h), 1 log10 kill at follow-up (96 h) and 90% maximal activity (AUBKC0-96).

CONCLUSIONS

Bladder infection modelling supports oral ciprofloxacin activity against E. coli with low-level resistance (ciprofloxacin MIC ≤ 1 mg/L) when using high dose therapy (750 mg 12 hourly).