Epidemiology of Bloodstream Infections Caused by Escherichia coli and Klebsiella pneumoniae That Are Piperacillin-Tazobactam-Nonsusceptible but Ceftriaxone-Susceptible

Clinical outcomes in patients with piperacillin/tazobactam-non-susceptible but ceftriaxone-susceptible E. coli or K. pneumoniae bloodstream infection

BACKGROUND

A small proportion of Escherichia coli and Klebsiella pneumoniae demonstrate in vitro non-susceptibility to piperacillin/tazobactam but retain susceptibility to ceftriaxone. Uncertainty remains regarding how best to treat these isolates.

OBJECTIVES

We sought to compare clinical outcomes between patients with piperacillin/tazobactam-non-susceptible but ceftriaxone-susceptible E. coli or K. pneumoniae bloodstream infection receiving definitive therapy with ceftriaxone versus an alternative effective antibiotic.

METHODS

We retrospectively identified patients with a positive blood culture for piperacillin/tazobactam-non-susceptible but ceftriaxone-susceptible E. coli or K. pneumoniae between 1 January 2013 and 31 December 2022. Patients were divided into one of two definitive treatment groups: ceftriaxone or alternative effective antibiotic. Our primary outcome was a composite of 90 day all-cause mortality, hospital readmission, or recurrence of infection. We used Cox proportional hazards models to compare time with the composite outcome between groups.

RESULTS

Sixty-two patients were included in our analysis. Overall, median age was 63 years (IQR 49.5-71.0), the most common source of infection was intra-abdominal (25/62; 40.3%) and the median total duration of therapy was 12.0 days (IQR 9.0-16.8). A total of 9/22 (40.9%) patients in the ceftriaxone treatment group and 18/40 (45.0%) patients in the alternative effective antibiotic group met the composite endpoint. In an adjusted time-to-event analysis, there was no difference in the composite endpoint between groups (HR 0.67, 95% CI 0.30-1.50). The adjusted Bayesian posterior probability that the HR was less than or equal to 1 (i.e. ceftriaxone is as good or better than alternative therapy) was 85%.

CONCLUSIONS

These findings suggest that ceftriaxone can be used to effectively treat bloodstream infections with E. coli or K. pneumoniae that are non-susceptible to piperacillin/tazobactam but susceptible to ceftriaxone.

Treatment of Piperacillin-Tazobactam-Nonsusceptible/Ceftriaxone-Susceptible Infections With Carbapenem Versus Carbapenem-Sparing Antimicrobials

Background

Escherichia coli and Klebsiella pneumoniae with a piperacillin-tazobactam-nonsusceptible/ceftriaxone-susceptible (TZP-NS/CRO-S) phenotype have been increasingly identified, with limited available literature evaluating treatment strategies.

Methods

This was a retrospective study of noncritically ill adults hospitalized between 2013 and 2021 and treated at least 48 hours for TZP-NS/CRO-S E coli or K pneumoniae infections. The primary composite endpoint included escalation to intensive care unit, infection- or treatment-related readmission, mortality, and infection recurrence. Outcomes were compared between groups who received carbapenem (CG) versus carbapenem-sparing agents (CSG) as targeted gram-negative therapy.

Results

Of 1062 patients screened, 200 were included (CG, n = 51; CSG, n = 149). Baseline characteristics, including Charlson Comorbidity Index (CCI; median [interquartile range], 6 [3-9] vs 6 [4-9]; P = .704), were similar between groups, except for more immunocompromised CG patients (29% vs 11%, P = .001). The most common infection sources were urinary (31% vs 57%, P = .002) and bloodstream (18% vs 17%, P = .887). Eighty-eight percent of the CG received meropenem, while 58% of the CSG received ceftriaxone as targeted therapy. There was no statistical difference in the primary endpoint between overall groups (27% vs 17%, P = .123), nor when stratified by infection source. More patients in the CSG switched to oral therapy (15 [29%] vs 100 [67%], P < .001). In multivariate analysis, CCI was an independent predictor of the primary outcome (odds ratio [OR], 1.199 [95% confidence interval, 1.074-1.340]; P = .001), while treatment with carbapenem-sparing therapy was not.

Conclusions

Our study did not find improved clinical outcomes with targeted carbapenem therapy for TZP-NS/CRO-S infections. Carbapenem-sparing agents may be considered to spare carbapenems in noncritically ill patients similar to those included in our cohort.

Piperacillin/tazobactam-resistant, cephalosporin-susceptible Escherichia coli bloodstream infections are driven by multiple acquisition of resistance across diverse sequence types

Resistance to piperacillin/tazobactam (TZP) in Escherichia coli has predominantly been associated with mechanisms that confer resistance to third-generation cephalosporins. Recent reports have identified E. coli strains with phenotypic resistance to piperacillin/tazobactam but susceptibility to third-generation cephalosporins (TZP-R/3GC-S). In this study we sought to determine the genetic diversity of this phenotype in E. coli (n=58) isolated between 2014–2017 at a single tertiary hospital in Liverpool, UK, as well as the associated resistance mechanisms. We compare our findings to a UK-wide collection of invasive E. coli isolates (n=1509) with publicly available phenotypic and genotypic data. These data sets included the TZP-R/3GC-S phenotype (n=68), and piperacillin/tazobactam and third-generation cephalosporin-susceptible (TZP-S/3GC-S, n=1271) phenotypes. The TZP-R/3GC-S phenotype was displayed in a broad range of sequence types, which was mirrored in the same phenotype from the UK-wide collection, and the overall diversity of invasive E. coli isolates. The TZP-R/3GC-S isolates contained a diverse range of plasmids, indicating multiple acquisition events of TZP resistance mechanisms rather than clonal expansion of a particular plasmid or sequence type. The putative resistance mechanisms were equally diverse, including hyperproduction of TEM-1, either via strong promoters or gene amplification, carriage of inhibitor-resistant β-lactamases, and an S133G bla_CTX-M-15 mutation detected for the first time in clinical isolates. Several of these mechanisms were present at a lower abundance in the TZP-S/3GC-S isolates from the UK-wide collection, but without the associated phenotypic resistance to TZP. Eleven (19%) of the isolates had no putative mechanism identified from the genomic data. Our findings highlight the complexity of this cryptic phenotype and the need for continued phenotypic monitoring, as well as further investigation to improve detection and prediction of the TZP-R/3GC-S phenotype from genomic data.

Fast-track identification of CTX-M-extended-spectrum-β-lactamase- and carbapenemase-producing Enterobacterales in bloodstream infections: implications on the likelihood of deduction of antibiotic susceptibility in emergency and internal medicine departments

This study aims at presenting a reliable fast-track diagnostics for the detection of CTX-M ESBL- (CTX-M-p) and carbapenemase-producers (CA-p) directly from blood cultures (BCs) of patients with Enterobacterales (EB) bloodstream infections (BSIs) admitted in emergency and internal medicine departments and its contribution in estimation of in vitro antibiotic susceptibility. A fast-track workflow including MALDI-TOF species identification and two lateral flow immunochromatographic assays for the detection of CTX-M-p and CA-p directly from BCs was performed in parallel with conventional routine, and results were compared. A total of 236 BCs of patients suffering from EB BSI were included. Accuracy of the fast-track workflow ranged from 99.6 to 100%. Among E. coli isolates, CTX-M-p (20.5%) were susceptible to ceftolozane-tazobactam (C/T, 97%), ceftazidime-avibactam (CZA, 100%), and piperacillin-tazobactam (TZP, 84.8%), whereas CTX-M-and-main-carbapenemases-non-producer (CTX-M-CA-np, 79.5%) isolates were susceptible to all the antibiotics tested. Among K. pneumoniae isolates, CTX-M-p (23.3%) were poorly susceptible to TZP (40%) but widely susceptible to C/T (90%), CZA (100%), and amikacin (90%), whereas CTX-M-CA-np (55.8%) were also susceptible to cefepime. CA-p K. pneumoniae (20.9%) were susceptible to CZA (88.9%). All the species other than E. coli and K. pneumoniae were CTX-M-CA-np and were widely susceptible to the antibiotics tested except for isolates of the inducible and derepressed AmpC- or AmpC/ESBL-p species. Rapid identification of species and phenotype together with knowledge of local epidemiology may be crucial to determine the likelihood of deduction of in vitro antibiotic susceptibility on the same day of positive BC processing.

Cefoperazone/sulbactam: New composites against multiresistant gram negative bacteria?

Sulbactam, a class A β-lactamase inhibitor, added to cefoperazone either at a fixed 8 mg/L level of sulbactam or at a level of fixed cefoperazone: sulbactam ratio (2:1) would constitute a combination form of cefoperazone/sulbactam, which has better activities against Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii than cefoperazone alone. Cefoperazone/sulbactam (1:1 or 1:2) has greater in-vitro activity against most multidrug-resistant organisms (ESBL- and AmpC-producing Enterobacteriaceae and carbapenem-resistant A. baumannii except for carbapenem-resistant P. aeruginosa) than a 2:1 ratio. However, increased sulbactam concentration may induce AmpC production. Besides, sulbactam concentration might not be readily achievable in serum if the susceptibility rates were defined by the breakpoints of higher sulbactam composites, such as ≤16/16 (1:1) or 16/32 (1:2) mg/L. Carbapenemases (KPC-, OXA-type enzymes and metallo-β-lactamases) can't be inhibited by sulbactam. Some in-vitro studies showed that increasing sulbactam composites of cefoperazone/sulbactam had no effect on carbapenem-resistant P. aeruginosa, suggesting the presence of carbapenemases or AmpC overproduction that could not be overcome by increasing sulbactam levels to recover cefoperazone activity. Sulbactam alone has good intrinsic activity against carbapenem-resistant Acinetobacter strains sometimes even in the presence of carbapenemase genes, suggesting unsteady levels of carbapenemases. In conclusion, appropriate composites of cefoperazone and β-lactamase inhibitor sulbactam may expand the clinical use if the pharmacokinetic optimization could be achieved in the human serum.

Piperacillin/tazobactam resistance in a clinical isolate of Escherichia coli due to IS26-mediated amplification of blaTEM-1B

A phenotype of Escherichia coli and Klebsiella pneumoniae, resistant to piperacillin/tazobactam (TZP) but susceptible to carbapenems and 3rd generation cephalosporins, has emerged. The resistance mechanism associated with this phenotype has been identified as hyperproduction of the β-lactamase TEM. However, the mechanism of hyperproduction due to gene amplification is not well understood. Here, we report a mechanism of gene amplification due to a translocatable unit (TU) excising from an IS26-flanked pseudo-compound transposon, PTn6762, which harbours blaTEM-1B. The TU re-inserts into the chromosome adjacent to IS26 and forms a tandem array of TUs, which increases the copy number of blaTEM-1B, leading to TEM-1B hyperproduction and TZP resistance. Despite a significant increase in blaTEM-1B copy number, the TZP-resistant isolate does not incur a fitness cost compared to the TZP-susceptible ancestor. This mechanism of amplification of blaTEM-1B is an important consideration when using genomic data to predict susceptibility to TZP.

A randomized control trial evaluating efficacy of antimicrobial impregnated hospital privacy curtains in an intensive care setting

BACKGROUND

Acquisition of pathogens into health care settings from prior room occupants has been documented. Hospital room privacy curtains are at high risk for pathogenic bacterial contamination. Antimicrobial impregnated curtains could be effective in reducing contamination.

METHODS

Rooms within an intensive care unit at The University of Iowa Hospitals and Clinics were randomized to 3 arms. The 2 intervention arms: (1) halamine antimicrobial curtains (BioSmart curtain [BSC]) and (2) halamine antimicrobial curtains sprayed twice weekly with a sodium hypochlorite-based disinfecting spray (BSC-pre and BSC-post) and a third control arm (standard curtain [SC]). Samples were collected twice weekly for 3 weeks to assess pathogenic bacterial contamination.

RESULTS

The likelihood of remaining uncontaminated was 38% for SC, 37% for BSC, and 60% for the BSC-pre group. Time to event (contamination) analysis found no statistically significant difference between pathogenic contamination between the SC, BSC, and BSC-pre groups (P value = .1921). There was a decrease in average colony count for BSC curtains compared with control, however, this difference was not statistically significant. Hypochlorite spray was found to transiently decontaminate curtains, but effects dissipated after 72 hours.

CONCLUSIONS

BSC did not show a significant reduction in pathogenic contamination compared with control. Antimicrobial curtains could have a role in reducing environmental contamination in the health care setting. Future studies should be done to determine the long-term effects of using antimicrobial curtains in health care.

Piperacillin-Tazobactam-Resistant/Third-Generation Cephalosporin-Susceptible Escherichia coli and Klebsiella pneumoniae Isolates: Resistance Mechanisms and In vitro-In vivo Discordance

We previously reported the detection of Escherichia coli and Klebsiella pneumoniae that displayed in vitro piperacillin-tazobactam (TZP) resistance but were susceptible to third-generation cephalosporins (TZP-R/Ceph3-S). In this study, we assessed the phenotypic and genotypic profiles of 12 clinical non-clonal TZP-R/Ceph3-S E. coli and K. pneumoniae isolates derived from bloodstream infections. Whole-genome sequencing revealed that most of the TZP-R/Ceph3-S E. coli and K. pneumoniae isolates examined harbored bla_TEM-1 and bla_SHV-1 genes, respectively, but none harbored extended-spectrum β-lactamase, AmpC β-lactamase or carbapenemase genes. Increasing the tazobactam concentration from 4 mg/L to 16 mg/L restored TZP in vitro susceptibility among E. coli isolates expressing TEM-1, but had minimal impact on the susceptibility of K. pneumoniae to TZP. Real-time qPCR analysis showed that bla_TEM-1 expression was amplified in TZP-R E. coli upon incubation with sub-inhibitory TZP concentrations. Using an immunocompetent murine septicemia model, the efficacy of TZP against TZP-R/Ceph3-S isolates was assessed using TZP doses that mimicked human plasma exposures following intravenous (IV) administration of TZP 4.5 g q6h over 0.5 h for 24 h. Efficacy was assessed by survival through 96 h. There was high mortality in untreated control mice for all tested isolates. Compared with controls, TZP human-simulated exposure significantly improved survival for all TZP-R/Ceph3-S E. coli and K. pneumoniae isolates examined (P < 0.05). Thus, TZP was associated with remarkable in vivo activity against TZP-R/Ceph3-S E. coli and K. pneumoniae despite the observed resistance in vitro.

SHV Hyperproduction as a Mechanism for Piperacillin-Tazobactam Resistance in Extended-Spectrum Cephalosporin-Susceptible Klebsiella pneumoniae

This study aimed to determine the mechanism of resistance to piperacillin-tazobactam (TZP) in Klebsiella pneumoniae bloodstream isolates that are susceptible to extended-spectrum cephalosporins (ESCs). Antibiotic susceptibility was determined for K. pneumoniae isolated from children with bacteremia. The β-lactamase genes were detected using a large-scale bla detection method (_LARGE-SCALEblaFinder) and confirmed by sequencing analysis. The isolates were further characterized by β-lactamase activity assays and multilocus sequence typing. Among the 300 bloodstream isolates of K. pneumoniae, 11 (3.7%) were TZP resistant but ESC susceptible. The TZP minimum inhibitory concentrations (MICs) of the isolates ranged from 128/4 to >2,048/4 mg/L. Avibactam markedly inhibited piperacillin resistance, reducing the MICs to the range of ≤1 to 8 mg/L. Among the 11 isolates, four hyperproduced SHV-1 and two hyperproduced SHV-11, exhibiting 77- to 496-fold higher β-lactamase activity compared with the SHV-1- and SHV-11-producing reference strains that are susceptible to TZP. OXA-1 was coproduced in three isolates, and the remaining two isolates produced TEM-30. Transformants with recombinant plasmids carrying the β-lactamase genes demonstrated an increase in MICs of TZP. The TZP-resistant and ESC-susceptible isolates were not epidemiologically related. Hyperproduction of SHV-1 and SHV-11 represents a novel mechanism for reducing TZP activity in K. pneumoniae isolates resistant to ESCs. Continuous monitoring and investigation of TZP-resistant isolates are needed in the current era of high TZP consumption.

Resistance to piperacillin/tazobactam in Escherichia coli resulting from extensive IS26-associated gene amplification of blaTEM-1

Background

bla TEM-1 encodes a narrow-spectrum β-lactamase that is inhibited by β-lactamase inhibitors and commonly present in Escherichia coli. Hyperproduction of blaTEM-1 may cause resistance to penicillin/β-lactamase inhibitor (P/BLI) combinations.

Objectives

To characterize EC78, an E. coli bloodstream isolate, resistant to P/BLI combinations, which contains extensive amplification of blaTEM-1 within the chromosome.

Methods

EC78 was sequenced using Illumina and Oxford Nanopore Technology (ONT) methodology. Configuration of blaTEM-1 amplification was probed using PCR. Expression of blaTEM-1 mRNA was determined using quantitative PCR and β-lactamase activity was determined spectrophotometrically in a nitrocefin conversion assay. Growth rate was assessed to determine fitness and stability of the gene amplification was assessed by passage in the absence of antibiotics.

Results

Illumina sequencing of EC78 identified blaTEM-1B as the only acquired β-lactamase preceded by the WT P3 promoter and present at a copy number of 182.6 with blaTEM-1B bracketed by IS26 elements. The chromosomal location of the IS26-blaTEM-1B amplification was confirmed by ONT sequencing. Hyperproduction of blaTEM-1 was confirmed by increased transcription of blaTEM-1 and β-lactamase activity and associated with a significant fitness cost; however, the array was maintained at a relatively high copy number for 150 generations. PCR screening for blaTEM amplification of isolates resistant to P/BLI combinations identified an additional strain containing an IS26-associated amplification of a blaTEM gene.

Conclusions

IS26-associated amplification of blaTEM can cause resistance to P/BLI combinations. This adaptive mechanism of resistance may be overlooked if simple methods of genotypic prediction (e.g. gene presence/absence) are used to predict antimicrobial susceptibility from sequencing data.