Pharmacokinetics and Pharmacodynamics of Temocillin

Population pharmacokinetics and dosing simulations of temocillin in liver-transplanted paediatric patients: a prospective, open-label, non-randomized study

OBJECTIVES

Temocillin is a β-lactam antibiotic used for preventing or treating bacterial infections in liver-transplanted children. We characterized its pharmacokinetics in plasma and ascitic fluid and proposed dosing regimens that maximize the achievement of effective drug exposures in this patient group.

METHODS

Patients aged 6-36 months received 25 mg/kg/12 h (n = 14) or 25 mg/kg/8 h (n = 23). Total and unbound temocillin concentrations were measured in plasma and ascitic fluid. Drug safety was monitored. Non-compartmental and population pharmacokinetic analyses were performed, together with Monte Carlo simulations.

RESULTS

No safety concerns were reported. For 25 mg/kg/12 h, the unbound mean (±standard deviation) Cmax and Cmin were 38 ± 16 and 2 ± 1 mg/L, respectively. For the 25 mg/kg/8 h dose, the unbound Cmax remained similar although the mean Cmin increased to 5 ± 3 mg/L. Protein binding was saturable. Median penetration in ascitic fluid from plasma was 82% (min-max: 63-95%). A three-compartment model with first-order elimination best described unbound pharmacokinetic profiles in plasma and ascitic fluid, with body weight and estimated glomerular filtration rate (GFR) as significant covariates. Monte Carlo simulations suggested that 90% probability of target attainment was achieved in both fluids with 25 mg/kg/12 h for MICs ≤4 mg/L, estimated GFR ≤180 mL/min/1.73 m2 or weight ≥6 kg, and with 25 mg/kg/8 h, for MICs ≤8 mg/L, GFR ≤120 mL/min/1.73 m2 or weight ≥11 kg.

DISCUSSION

Although adequate in many instances, the current dosing regimen is likely inadequate for patients with low body weight, high renal function, or bacteria with high MIC, emphasizing the need for patient-specific factors to be considered in dose selection. These data support the importance of paediatric pharmacokinetic studies to optimize drug dosing regimens.

Pharmacokinetic/pharmacodynamic model-based optimization of temocillin dosing strategies for the treatment of systemic infections

BACKGROUND

Temocillin is increasingly considered as an alternative to carbapenems. However, there is no consensus on optimal dosing strategies and limited data on temocillin efficacy in systemic infections.

OBJECTIVES

We compared temocillin dosing strategies using pharmacokinetic/pharmacodynamic (PK/PD) modelling and simulation based on plasma exposure and in vitro time-kill data.

METHODS

Temocillin effects on four Escherichia coli strains were evaluated using static time-kill experiments and the hollow-fibre infection model, in which unbound plasma concentrations following intermittent and continuous infusion regimens of 4 and 6 g daily were replicated over 72 h. A PK/PD model was developed to describe the time-kill data. The PK/PD model was coupled to a population PK model of temocillin in critically ill patients to predict bacterial killing and resistance development following various dosing regimens.

RESULTS

Amplification of resistant subpopulations was observed within 24 h for all strains. The PK/PD model described the observed bacterial kill kinetics and resistance development from both experimental systems well. Simulations indicated dose-dependent bacterial killing within and beyond the currently used daily dose range, and a superiority of continuous compared with intermittent infusions. However, regrowth of resistant subpopulations was frequently observed. For two strains, bacteriostasis over 72 h was predicted only with doses that are higher than those currently licensed.

CONCLUSIONS

Continuous infusions and 6 g daily doses of temocillin kill E. coli more effectively than 4 g daily doses and intermittent infusions, and may increase efficacy in the treatment of systemic infections. However, higher daily doses may be required to suppress resistance development.

Effectiveness of temocillin in treatment of non-urinary tract infections caused by ESBL-producing Enterobacterales and risk factors for failure

Objectives

To describe the real-life use of temocillin for non-urinary tract infections, to assess its effectiveness in infections caused by ESBL-producing Enterobacterales, and to identify risk factors for treatment failure.

Method

Retrospective multicentric study in 14 tertiary care hospitals, including all patients who received at least one dose of temocillin for ESBL infections from 1 January 2016 to 31 December 2021 for non-urinary tract infections. Failure was a composite criterion defined within 28 day follow-up by persistence or reappearance of signs of infection, and/or switch to suppressive antibiotic treatment and/or death from infection. Logistic regression with univariable and multivariable analysis was performed to identify risks associated with failure.

Results

Data on 163 infection episodes were collected; 133 were due to ESBL-producing Enterobacterales and 128 were included in the effectiveness analysis. Median (IQR) age was 61 (53-70) years and 61.7% of patients were male. Main indications were lower respiratory tract infection (LRTI; 28.9%), intra-abdominal infections (IAI; 28.1%) and cutaneous infections (12.5%). The main bacteria involved were Klebsiella pneumoniae (48.4%), Escherichia coli (25.0%) and Enterobacter cloacae (24.2%). Polymicrobial infections occurred in 45.3% of cases. Temocillin was used as monotherapy in 86/128 (67.2%). Failure was found in 36/128 (28.1%) cases. In multivariable analysis, the only factor associated with failure was initial severity of the episode [adjusted OR 3.0 (95% CI: 1.06-8.69)].

Conclusions

During non-urinary tract infections, the main use of temocillin was for LRTIs and IAIs due to ESBL-producing E. coli and K. pneumoniae. The main risk factor for failure was initial severity of the disease.

Impact of the phenotypic expression of temocillin resistance in Escherichia coli on temocillin efficacy in a murine peritonitis model

BACKGROUND

Temocillin is a narrow spectrum β-lactam active against MDR Enterobacterales. Mechanisms of acquired resistance to temocillin are poorly understood. We analysed resistance mechanisms in clinical isolates of Escherichia coli and evaluated their impact on temocillin efficacy in vitro and in a murine peritonitis model.

METHODS

Two sets of isogenic clinical E. coli strains were studied: a susceptible isolate (MLTEM16S) and its resistant derivative, MLTEM16R (mutation in nmpC porin gene); and temocillin-resistant derivatives of E. coli CFT073: CFT-ΔnmpC (nmpC deletion), CFTbaeS-TP and CFTbaeS-AP (two different mutations in the baeS efflux-pump gene).Fitness cost, time-kill curves and phenotypic expression of resistance were determined. Temocillin efficacy was assessed in a murine peritonitis model.

RESULTS

MICs of temocillin were 16 and 64 mg/L for MLTEM16S and MLTEM16R, respectively, and 8, 128, 256 and 256 mg/L for E. coli-CFT073, CFT-ΔnmpC, CFTbaeS-TP and CFTbaeS-AP, respectively. No fitness cost of resistance was evidenced. All resistant strains showed heteroresistant profiles, except for CFTbaeS-AP, which displayed a homogeneous pattern. In vitro, temocillin was bactericidal against MLTEM16R, CFT-ΔnmpC, CFTbaeS-TP and CFTbaeS-AP at 128, 256, 512 and 512 mg/L, respectively. In vivo, temocillin was as effective as cefotaxime against MLTEM16R, CFT-ΔnmpC and CFTbaeS-TP, but inefficient against CFTbaeS-AP (100% mortality).

CONCLUSIONS

Heteroresistant NmpC porin alteration and active efflux modification do not influence temocillin efficacy despite high MIC values, unfavourable pharmacokinetic/pharmacodynamic conditions and the absence of fitness cost, whereas homogeneously expressed BaeS efflux pump alteration yielding similar MICs leads to temocillin inefficacy. MIC as sole predictor of temocillin efficacy should be used with caution.

Evaluation of temocillin efficacy against KPC-2-producing Klebsiella pneumoniae isolates in a hollow-fibre infection model

BACKGROUND

Temocillin is an old antimicrobial that is resistant to hydrolysis by ESBLs but has variable activity against carbapenemase-producing Enterobacteriaceae. The current EUCAST susceptibility breakpoints for Enterobacterales are set at ≤16 mg/L (susceptible with increased exposure) based on a dose of 2 g q8h, but there is limited information on the efficacy of this dose against temocillin-susceptible carbapenemase-producing Klebsiella pneumoniae isolates.

OBJECTIVES

To evaluate the efficacy of this dose using a hollow-fibre infection model (HFIM) against six KPC-2-producing clinical isolates of K. pneumoniae.

METHODS

The isolates were characterized by WGS and temocillin susceptibility was determined using standard and high inoculum temocillin. Mutant frequencies were estimated and temocillin activity was tested in time-kill assays and in the HFIM. At standard conditions, three of the isolates were classified as susceptible (MIC ≤ 16 mg/L) and three as resistant (MIC > 16 mg/L). The HFIM was performed over 3 days to mimic human-like pharmacokinetics of 2 g q8h. Bacterial counts were performed by plating on Mueller-Hinton agar (MHA) and MHA containing 64 mg/L temocillin to detect resistant subpopulations.

RESULTS

All isolates showed a reduction in bacterial population of at least 3 log cfu/mL within the first 8 h of simulated treatment in the hollow-fibre assay. Regrowth was observed for the three resistant isolates and one of the susceptible ones. The MIC value for these isolates was higher by at least two dilutions compared with their initial values.

CONCLUSIONS

These data suggest that an optimized pharmacokinetic regimen may be of clinical interest for the treatment of KPC-2-producing K. pneumoniae susceptible to temocillin. These data showed activity of temocillin against KPC-2-producing K. pneumoniae susceptible to temocillin; however, a dose of 2g q8h administered over 30 min may be inadequate to prevent the emergence of resistant variants.

Population pharmacokinetics and dosing simulations of total and unbound temocillin in the plasma and CSF of neurocritically ill patients with external ventricular drain-related cerebral ventriculitis

BACKGROUND

Cerebral ventriculitis might be caused by Gram-negative bacteria, including ESBL producers. Temocillin may be a useful treatment option in this scenario; however, no consistent data are available regarding its penetration into the CSF.

OBJECTIVES

To describe the population pharmacokinetics of temocillin in plasma and CSF and to determine the probability for different simulated dosing regimens to achieve pharmacokinetic/pharmacodynamic (PK/PD) targets in the CSF.

METHODS

Ten post-neurosurgical critically ill adult patients requiring continuous drainage of CSF were included in this monocentric, prospective, open-label, non-randomized study. They received 2 g loading dose temocillin over 30 min IV infusion, followed by a 6 g continuous infusion over 24 h. Total and unbound concentrations were measured in plasma (n = 88 and 86) and CSF (n = 88 and 88) samples and used to build a population PK model. Monte Carlo simulations were performed to estimate the PTA at 100% Css>MIC (steady state concentration above the MIC) in CSF.

RESULTS

All patients were infected with Enterobacterales with temocillin MICs ≤8 mg/L. The median (min-max) temocillin penetration in CSF was 12.1% (4.3-25.5) at steady state. Temocillin unbound plasma pharmacokinetics were best described by a one-compartment model. PTA for the applied dosing regimen was >90% for bacteria with MIC ≤ 4 mg/L.

CONCLUSIONS

The currently approved dose of 6 g by continuous infusion may be adequate for the treatment of ventriculitis by Enterobacterales with MIC ≤ 4 mg/L if considering 100% Css>MIC as the PK/PD target to reach. Higher maintenance doses could help covering higher MICs, but their safety would need to be assessed.

Budget impact analysis of temocillin insurance coverage for urinary tract infections caused by ESBL-producing pathogens in Iran

BACKGROUND

One of the most prevalent infections with a significant disease burden is urinary tract infections (UTIs), which occurs in approximately 50% of women at least once in their lifetime. Antimicrobial resistance to pathogens causing UTIs is expanding worldwide and has been associated with increased use of broad-spectrum antibiotics, including carbapenems, leading to significant costs for insurance and healthcare systems. The emergence of resistance to carbapenems has led to an increasing need for and interest in carbapenem-sparing strategies, including the use of narrow-spectrum antibiotics, such as temocillin. Temocillin has a strong bactericidal effect, along with high tolerability and a good safety profile. It is also stable toward most extended-spectrum beta-lactamases (ESBL). The purpose of our study was to design a budget impact analysis (BIA) model and estimate the budget impact of temocillin insurance coverage for the treatment of UTIs caused by ESBL-producing bacteria from the perspective of the payer.

METHODS

The BIA model with insurance payer perspective was used to estimate the impact of temocillin insurance coverage on the treatment of UTIs caused by ESBL-producing bacteria over a 1-year time horizon in Iran. Direct medicine costs, hospitalization and paraclinical costs, and side effect costs were considered in this model. To assess the impact of uncertainty on the model inputs, 1-way sensitivity analyses were performed.

RESULTS

The model demonstrates that inclusion of temocillin in insurance coverage, decreasing treatment costs from $36 million to $34 million, will result in overall savings of > $1.9 million and lead to > $9 million savings in insurance costs for antimicrobial resistance.

CONCLUSION

The inclusion of temocillin in the insurance coverage in Iran for patients developing UTIs caused by ESBL-producing bacteria would be cost-saving for insurance and decrease the risk associated with emerging antimicrobial resistance.

Assumptions Underlying Hepatic Clearance Models: Recognizing the Influence of Saturable Protein Binding on Driving Force Concentration and Discrimination Between Models of Hepatic Clearance

One underlying assumption of hepatic clearance models is often underappreciated. Namely, plasma protein binding is assumed to be nonsaturable within a given drug concentration range, dependent only on protein concentration and equilibrium dissociation constant. However, in vitro hepatic clearance experiments often use low albumin concentrations that may be prone to saturation effects, especially for high-clearance compounds, where the drug concentration changes rapidly. Diazepam isolated perfused rat liver literature datasets collected at varying concentrations of albumin were used to evaluate the predictive utility of four hepatic clearance models (the well-stirred, parallel tube, dispersion, and modified well-stirred model) while both ignoring and accounting for potential impact of saturable protein binding on hepatic clearance model discrimination. In agreement with previous literature findings, analyses without accounting for saturable binding showed poor clearance prediction using all four hepatic clearance models. Here we show that accounting for saturable albumin binding improves clearance predictions across the four hepatic clearance models. Additionally, the well-stirred model best reconciles the difference between the predicted and observed clearance data, suggesting that the well-stirred model is an appropriate model to describe diazepam hepatic clearance when considering appropriate binding models. SIGNIFICANCE STATEMENT: Hepatic clearance models are vital for understanding clearance. Caveats in model discrimination and plasma protein binding have sparked an ongoing scientific discussion. This study expands the understanding of the underappreciated potential for saturable plasma protein binding. Fraction unbound must correspond to relevant driving force concentration. These considerations can improve clearance predictions and address hepatic clearance model disconnects. Importantly, even though hepatic clearance models are simple approximations of complex physiological processes, they are valuable tools for clinical clearance predictions.

Temocillin Resistance in the Enterobacter cloacae Complex Is Conferred by a Single Point Mutation in BaeS, Leading to Overexpression of the AcrD Efflux Pump

The Enterobacter cloacae complex (ECC) has become a major opportunistic pathogen with antimicrobial resistance issues. Temocillin, an "old" carboxypenicillin that is remarkably stable toward β-lactamases, has been used as an alternative for the treatment of multidrug-resistant ECC infections. Here, we aimed at deciphering the never-investigated mechanisms of temocillin resistance acquisition in Enterobacterales. By comparative genomic analysis of two clonally related ECC clinical isolates, one susceptible (Temo_S [MIC of 4 mg/L]) and the other resistant (Temo_R [MIC of 32 mg/L]), we found that they differed by only 14 single-nucleotide polymorphisms, including one nonsynonymous mutation (Thr175Pro) in the two-component system (TCS) sensor histidine kinase BaeS. By site-directed mutagenesis in Escherichia coli CFT073, we demonstrated that this unique change in BaeS was responsible for a significant (16-fold) increase in temocillin MIC. Since the BaeSR TCS regulates the expression of two resistance-nodulation-cell division (RND)-type efflux pumps (namely, AcrD and MdtABCD) in E. coli and Salmonella, we demonstrated by quantitative reverse transcription-PCR that mdtB, baeS, and acrD genes were significantly overexpressed (15-, 11-, and 3-fold, respectively) in Temo_R. To confirm the role of each efflux pump in this mechanism, multicopy plasmids harboring mdtABCD or acrD were introduced into either Temo_S or the reference strain E. cloacae subsp. cloacae ATCC 13047. Interestingly, only the overexpression of acrD conferred a significant increase (from 8- to 16-fold) of the temocillin MIC. Altogether, we have shown that temocillin resistance in the ECC can result from a single BaeS alteration, likely resulting in the permanent phosphorylation of BaeR and leading to AcrD overexpression and temocillin resistance through enhanced active efflux.

Hypoalbuminemia and Pharmacokinetics: When the Misunderstanding of a Fundamental Concept Leads to Repeated Errors over Decades

Surprisingly, misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs seems to be a current problem, even though hypoalbuminemia has no impact on the pharmacologically active exposure. Exceptions to this fact are highly protein-bound anaesthetics with high elimination capacity (i.e., <5 drugs on the market). To assess the frequency of misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs between 1975 and 2021, a PubMed literature review was conducted. Each paragraph on albumin binding was classified as correct, ambiguous or incorrect, creating two acceptable categories: (1) content without any errors, and (2) content containing some incorrect and/or ambiguous statements. The analyses of these articles showed that fewer than 11% of articles contained no interpretation errors. In order to contain this misinterpretation, several measures are proposed: (1) Make the message accessible to a wide audience by offering a simplified and didactic video representation of the lack of impact of albumin binding to drugs. (2) Precise terminology (unbound/free form/concentration) should be used for highly bound drugs. (3) Unbound/free forms should be systematically quantified for highly plasma protein bound drugs for clinical trials as well as for therapeutic drug monitoring.

Evaluation of the stability of temocillin in elastomeric infusion devices used for outpatient parenteral antimicrobial therapy in accordance with the requirements of the UK NHS Yellow Cover Document

OBJECTIVE

To evaluate the stability of temocillin solution in two elastomeric infusion devices - Easypump II LT 270-27- S and Dosi-Fusor L25915-250D1 for OPAT administration during 14 days of 5°C±3°C fridge storage followed by 24 hour exposure at an in-use temperature of 32°C, when reconstituted with 0.3% citrate buffer at pH7.

METHODS

Stability testing was conducted in accordance with standard protocols in the UK National Health Service Yellow Cover Document (YCD). A stability indicating assay method was applied using a high-performance liquid chromatography (HPLC) system with a photodiode array detector. Low (500 mg/240 mL), intermediate (4000 mg/240 mL) and high (6000 mg/240 mL) temocillin concentrations were tested in triplicate devices with duplicate samples taken at 11 time points during fridge storage and subsequent in-use temperature exposure.

RESULT

The percentage of temocillin remaining after 14 days of fridge storage was greater than 97% in both devices and at all concentrations tested. During subsequent in-use temperature exposure, a 95% stability limit was achieved for 12 hours except for the high concentration (25 mg/mL) in the Dosi-Fusor device. It met this criterion for only 10 hours - the percent of temocillin remaining at 12 hours was 94.5%. However, for all devices and the doses tested, the degradation of temocillin was <9% at the end of 24 hours in-use temperature exposure.

CONCLUSION

Temocillin reconstituted with 0.3% citrate buffer at pH7 in elastomeric infusion devices can be stored in a fridge (2°C-8°C) for 14 days meeting the YCD acceptance criteria. Considering <5% degradation, the current data supports twice daily dosing of temocillin within the OPAT setting. In jurisdictions where a <10% degradation limit is acceptable, once daily dosing with 24-hour continuous infusion may be considered. Temocillin is a useful alternative to other broad-spectrum anti-Gram-negative agents currently utilised in the OPAT setting and supports the wider antimicrobial stewardship agenda.

Pharmacodynamics of Temocillin in Neutropenic Murine Infection Models

Temocillin is used for the treatment of various infections caused by Enterobacterales. The pharmacokinetic (PK)/pharmacodynamic (PD) index that is best correlated with the activity of beta-lactams is the percentage of time that the unbound concentration exceeds the MIC (%fT>MIC). However, the %fT>MIC needed for a bacteriostatic or killing effect of temocillin is unknown in thigh and lung infection models. In the present study, we studied the temocillin PK in plasma and epithelial lining fluid (ELF) of infected neutropenic mice and determined the plasma exposure-response relationships for Escherichia coli and Klebsiella pneumoniae. Neutropenic murine thigh and lung infection models were used. The bacterial loads in the thighs or lungs were determined. A sigmoid maximum-effect model was used to fit the plasma exposure-response relationship. A one-compartment model with first-order absorption best described temocillin PK (clearance [CL], 1.03 L/h/kg; volume of distribution [V], 0.457 L/kg). Protein binding was 78.2% ± 1.3% across different plasma concentrations. A static effect was achieved for all strains in both the thigh and lung infection models. However, the median %fT>MIC needed for a static effect was much lower in the lung infection model (27.8% for E. coli and 38.2% for K. pneumoniae) than in the thigh infection model (65.2% for E. coli and 64.9% for K. pneumoniae). A 1-log kill was reached for all strains in the lung infection model (median %fT>MIC values of 42.1% for E. coli and 44.1% for K. pneumoniae) and 7 out of 8 strains in the thigh infection model (median %fT>MIC values of 85.4% for E. coli and 74.5% for K. pneumoniae). These data support the use of temocillin in patients with pneumonia.

Pharmacokinetics of Antimicrobials in Children with Emphasis on Challenges Faced by Low and Middle Income Countries, a Clinical Review

Effective antimicrobial exposure is essential to treat infections and prevent antimicrobial resistance, both being major public health problems in low and middle income countries (LMIC). Delivery of drug concentrations to the target site is governed by dose and pharmacokinetic processes (absorption, distribution, metabolism and excretion). However, specific data on the pharmacokinetics of antimicrobials in children living in LMIC settings are scarce. Additionally, there are significant logistical constraints to therapeutic drug monitoring that further emphasize the importance of understanding pharmacokinetics and dosing in LMIC. Both malnutrition and diarrheal disease reduce the extent of enteral absorption. Multiple antiretrovirals and antimycobacterial agents, commonly used by children in low resource settings, have potential interactions with other antimicrobials. Hypoalbuminemia, which may be the result of malnutrition, nephrotic syndrome or liver failure, increases the unbound concentrations of protein bound drugs that may therefore be eliminated faster. Kidney function develops rapidly during the first years of life and different inflammatory processes commonly augment renal clearance in febrile children, potentially resulting in subtherapeutic drug concentrations if doses are not adapted. Using a narrative review approach, we outline the effects of growth, maturation and comorbidities on maturational and disease specific effects on pharmacokinetics in children in LMIC.

Assessing Clinical Potential of Old Antibiotics against Severe Infections by Multi-Drug-Resistant Gram-Negative Bacteria Using In Silico Modelling

In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria.

Clinical and microbiological evaluation of temocillin for bloodstream infections with Enterobacterales: a Belgian single-centre retrospective study

Background

Expanding the use of temocillin could be an important weapon in the fight against antimicrobial resistance. However, EUCAST defined clinical breakpoints for a limited number of species and only for urinary tract infections (UTI), including urosepsis but excluding severe sepsis and septic shock. Moreover, a dosage of 2 g q8h is advised in most cases.

Objectives

Evaluation of temocillin use for the treatment of bacteraemia, correlating clinical and microbiological outcomes with infection site, infection severity, temocillin dosage, Enterobacterales species and MIC.

Patients and methods

All adult patients with blood cultures positive for temocillin-susceptible Enterobacterales and treated with temocillin for ≥72 h from June 2018 until June 2021 were considered for inclusion. The primary outcome was clinical success, defined as resolution of infection signs, no relapse of the same infection and no antibiotic switch due to insufficient clinical improvement. The secondary outcome was microbiological success.

Results

In total, 182 episodes were included [140 UTI versus 42 non-UTI, 171 Escherichia coli, Klebsiella species (except Klebsiella aerogenes) and Proteus mirabilis (EKPs) versus 11 non-EKPs]. Clinical and microbiological failure were low (8% and 3%, respectively). No difference in outcome was observed for dosages of 2 g q12h versus 2 g q8h, either for EKP versus non-EKP isolates or MIC values ≤8 versus 16 mg/L. Considering only bacteraemia episodes of UTI origin, using the 16 mg/L breakpoint, there was no difference in success rate between regimens of 2 g q12h and 2 g q8h.

Conclusions

Temocillin 2 g q12h can be successfully used for the treatment of systemic UTI. Prospective studies are needed to assess outcomes and evaluate non-inferiority compared with other broad-spectrum antibiotics in non-UTI infections, including bacteraemia.

E. coli bacterial meningitis after transrectal prostate biopsy under antibiotic prophylaxis: a case report and literature review

Prostate biopsy, a frequently performed procedure, is not harmless. In rare cases, life‐threatening complications occur. We document a potential lethal bacterial meningitis after transrectal biopsy. In addition to our overview of all previously documented cases, we highlight the evidence of prevention of infectious complications when performing a prostate biopsy.

Even after antibiotic prophylaxis, severe infections sometimes follow transrectal prostate biopsy. Involvement of the central nervous system is not well known but demands early recognition. In this situation, intravenous antibiotics with a high penetration through the blood–brain barrier are of vital importance. The most effective preventive measure against infectious complications is to change the biopsy approach to transperineal.

CTX-M-producing Escherichia coli strains: resistance to temocillin, fosfomycin, nitrofurantoin and biofilm formation

Aim: ESBL-producing and bacterial biofilms-forming Escherichia coli are associated with antimicrobial treatment failure. This study aimed to investigate the phenotypic resistance mechanisms of CTX-M E. coli against old antibiotics - cell wall synthesis inhibitors temocillin, nitrofurantoin and fosfomycin. Materials & Methods: Susceptibility to old antibiotics testing was performed using disk diffusion method, biofilm formation was evaluated spectrophotometrically, and PCR was used for the determination of CTX-M type. Results & conclusion: Temocillin was active against nearly 93%, nitrofurantoin and fosfomycin, respectively, 91.7% and 98.6% of tested E. coli. Thus, it demonstrated to be a good alternative therapeutic option against ESBL infections. Bacteria resistant to old antibiotics had CTX-M-15 or CTX-M-15, TEM-1 and OXA-1 combinations. No significant association was found between CTX-M E. coli resistance to temocillin, nitrofurantoin and fosfomycin; however, the level of biofilm formation was found as not affected by the type of CTX-M β-lactamases.

Anti-infective Medicines Use in Children and Neonates With Pre-existing Kidney Dysfunction: A Systematic Review

Background

Dosing recommendations for anti-infective medicines in children with pre-existing kidney dysfunction are derived from adult pharmacokinetics studies and adjusted to kidney function. Due to neonatal/pediatric age and kidney impairment, modifications in renal clearance and drug metabolism make standard anti-infective dosing for children and neonates inappropriate, with a risk of drug toxicity or significant underdosing. The aim of this study was the systematic description of the use of anti-infective medicines in pediatric patients with pre-existing kidney impairment.

Methods

A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The EMBASE, Medline and Cochrane databases were searched on September 21st, 2021. Studies in all languages reporting data on pre-defined outcomes (pharmacokinetics-PK, kidney function, safety and efficacy) regarding the administration of anti-infective drugs in children up to 18 years with pre-existing kidney dysfunction were included.

Results

29 of 1,792 articles were eligible for inclusion. There were 13 case reports, six retrospective studies, nine prospective studies and one randomized controlled trial (RCT), reporting data on 2,168 pediatric patients. The most represented anti-infective class was glycopeptides, with seven studies on vancomycin, followed by carbapenems, with five studies, mostly on meropenem. Antivirals, aminoglycosides and antifungals counted three articles, followed by combined antibiotic therapy, cephalosporins, lipopeptides with two studies, respectively. Penicillins and polymixins counted one study each. Nine studies reported data on patients with a decreased kidney function, while 20 studies included data on kidney replacement therapy (KRT). Twenty-one studies reported data on PK. In 23 studies, clinical outcomes were reported. Clinical cure was achieved in 229/242 patients. There were four cases of underdosing, one case of overdosing and 13 reported deaths.

Conclusion

This is the first systematic review providing evidence of the use of anti-infective medicines in pediatric patients with impaired kidney function or requiring KRT. Dosing size or interval adjustments in pediatric patients with kidney impairment vary according to age, critical illness status, decreased kidney function and dialysis type. Our findings underline the relevance of population PK in clinical practice and the need of developing predictive specific models for critical pediatric patients.

Temocillin: Applications in Antimicrobial Stewardship as a Potential Carbapenem-Sparing Antibiotic

Temocillin is an old antibiotic, but given its particular characteristics, it may be a suitable alternative to carbapenems for treating infections due to ESBL-producing Enterobacterales and uncomplicated UTI due to KPC-producers. In this narrative review, the main research question was to summarize current evidence on temocillin and its uses in infectious diseases. A search was run on PubMed using the terms ('Temocillin' [Mesh]) AND ('Infection' [Mesh]). Current knowledge regarding temocillin in urinary tract infection, blood-stream infections, pneumonia, intra-abdominal infections, central nervous system infections, skin and soft tissues infections, surgical sites infections and osteoarticular Infections were summarized. Temocillin retain a favourable profile on microbiota and risk of Clostridioides difficile infections and could be an option for treating outpatients. Temocillin may be a valuable tool to treat susceptible pathogens and for which a carbapenem could be spared. Other advantages in temocillin use are that it is well-tolerated; it is associated with a low rate of C. difficile infections; it is active against ESBL, AmpC, and KPC-producing Enterobacterales; and it can be used in the OPAT clinical setting.

Modelled target attainment after temocillin treatment in severe pneumonia: systemic and epithelial lining fluid pharmacokinetics of continuous versus intermittent infusions

Objectives: To describe the population pharmacokinetics of temocillin administered via continuous versus intermittent infusion in critically ill patients with pneumonia. Secondary objectives included characterization of epithelial lining fluid (ELF)/plasma penetration ratios and determination of the probability of target attainment (PTA) for a range of MICs. Methods: Thirty-two mechanically ventilated patients who were treated for pneumonia with 6g of temocillin daily for in vitro sensitive pathogens were assigned either to the II (2g every 8h over 0.5h) or to the CI (6g over 24h after a loading dose of 2g) group. A population pharmacokinetic model was developed using unbound plasma and total ELF concentrations of temocillin and related Monte Carlo simulations were performed to assess PTAs. Results: The AUC_0-24 ELF/plasma penetration ratio was 0.73, at steady-state, for both modes of infusion and whatever the level of creatinine clearance. Monte Carlo simulations showed for the minimal pharmacodynamic (PD) targets of 50% T> 1X MIC (II group) and 100% T > 1X MIC (CI group), PK/PD breakpoints of 4 mg/L in plasma and 2 mg/L in ELF and 4mg/L in plasma and ELF, respectively. The breakpoint was 8 mg/L in ELF for both modes of infusion in patients with CL_CR<60mL/min. Conclusion: While CI provides better PKPD indexes, the latter remain below available recommendations for systemic infections, except in case of moderate renal impairment, thereby warranting future clinical studies in order to determine the efficacy of temocillin in severe pneumonia.

OUP accepted manuscript

Background

With increasing resistance to common antibiotics the treatment of urinary tract infections has become challenging and alternative therapeutic options are needed. In the present study, we evaluate the activity of three older and less frequently used antibiotics against MDR Enterobacterales.

Methods

Susceptibility of mecillinam, temocillin and nitroxoline was assessed in Enterobacterales isolated from urinary specimens with elevated MICs of third-generation cephalosporins. Susceptibility was determined by the recommended reference MIC methods and additionally by disc diffusion. All isolates were characterized for common β-lactamases by phenotypic and molecular assays.

Results

In total 394 Enterobacterales were included. The most common resistance mechanisms were ESBLs (n = 273), AmpC (n = 132), carbapenemases [n = 12, including OXA-48-like (n = 8), VIM (n = 2), KPC (n = 1) and NDM (n = 1)] or others (n = 2). Resistance was observed in 59% of isolates to ceftazidime, in 41% to piperacillin/tazobactam and in 54% to ciprofloxacin. In comparison, resistance was less frequent against mecillinam (15%), temocillin (13%) or nitroxoline (2%). Mecillinam showed higher activity in Enterobacter spp., Escherichia coli and in OXA-48-like-producing isolates compared with temocillin, which was more active in Proteus mirabilis and in ESBL-producing isolates. Activity of nitroxoline was high against all isolates, including carbapenemase-producing isolates. Correlation between disc diffusion and MIC methods was good for mecillinam and moderate for temocillin and nitroxoline.

Conclusions

Mecillinam, temocillin and nitroxoline show good to excellent in vitro activity in MDR Enterobacterales. The activity of mecillinam and temocillin was higher in certain species and restricted depending on β-lactamase production while nitroxoline showed universally high activity irrespective of species or β-lactamase present.

The clinical and microbiological efficacy of temocillin versus cefotaxime in adults with febrile urinary tract infection, and its effects on the intestinal microbiota: a randomised multicentre clinical trial in Sweden

BACKGROUND

Use of third-generation cephalosporins, such as cefotaxime, is associated with an increased risk of selection for antimicrobial resistance, so alternative antibiotics need to be considered. The aim of the present study was to evaluate intestinal colonisation with third-generation cephalosporin-resistant pathogens following use of temocillin-an alternative antibiotic to cefotaxime that is potentially less prone to disturbing the intestinal microbiota-in empirical treatment of febrile urinary tract infection (UTI).

METHODS

We did a randomised, multicentre, superiority, open-label phase 4 trial in patients who had been admitted to inpatient care in 12 Swedish hospitals with suspected or diagnosed febrile UTI (complicated or uncomplicated). To meet inclusion criteria, a patient was required to have at least one sign or symptom of pyelonephritis (ie, flank pain; costovertebral angle tenderness; and changes to urinary frequency or urgency or dysuria), a fever of 38·0°C or higher, and a positive urine dipstick (for nitrites, white blood cells, or both). Participants were also required to have an indication for intravenous antibiotic treatment. Participants were randomly assigned (1:1) to receive either 2 g temocillin or 1-2 g cefotaxime, by local investigators opening consecutive sealed randomisation envelopes that were generated centrally in advance. Both drugs were administered intravenously every 8 h. The trial was open label for investigators and patients, but those doing the microbiological analyses were masked to the groups. Participants were treated with antibiotics for 7-10 days (or up to 14 days if they had bacteraemia), at least 3 days of which were on the study drug; at day 4 and later, participants who were showing improvement could be given an oral antibiotic (ciprofloxacin, ceftibuten, cefixime, or co-trimoxazole). Patients not showing improvement were regarded as having treatment failures. Rectal swabs were collected at three timepoints: at baseline (before the first dose), after the last dose of study drug, and 7-10 days after treatment stopped. The composite primary outcome was colonisation with Enterobacterales with reduced susceptibility to third-generation cephalosporins, or colonisation with toxin-producing Clostridioides difficile, or both, to evaluate disturbance of the intestinal microbiota. The study is registered in the EU Clinical Trials Register (EudraCT 2015-003898-15).

FINDINGS

Between May 20, 2016, and July 31, 2019, 207 patients were screened for eligibility, of whom 55 patients were excluded. 152 participants were randomly assigned to groups: 77 (51%) patients received temocillin, 75 (49%) patients received cefotaxime. The composite primary endpoint was met by 18 (26%) of 68 participants receiving temocillin versus 30 (48%) of 62 patients receiving cefotaxime (risk difference -22% [95% CI -42% to -3%]), showing superiority of temocillin versus cefotaxime (ie, less disturbance of the intestinal microbiota). 43 adverse events were reported in 40 (52%) of 77 patients in the temocillin group, versus 46 adverse events in 34 (45%) of 75 patients in the cefotaxime group. Most events were of mild to moderate severity. 21 (27%) patients in the temocillin and 17 (23%) patients in the cefotaxime group had an adverse event that was considered to be associated with the study drug.

INTERPRETATION

Temocillin was found to be less selective than cefotaxime of Enterobacterales with reduced susceptibility to third-generation cephalosporins, and it could therefore be a favourable alternative in the empirical treatment of febrile UTI. Use of this antibiotic could reduce hospital transmission and health-care-associated infections by these pathogens.

FUNDING

Public Health Agency of Sweden.

Temocillin versus meropenem for the targeted treatment of bacteraemia due to third-generation cephalosporin-resistant Enterobacterales (ASTARTÉ): protocol for a randomised, pragmatic trial

INTRODUCTION

Alternatives to carbapenems are needed in the treatment of third-generation cephalosporin-resistant Enterobacterales (3GCR-E). Temocillin is a suitable candidate, but comparative randomised studies are lacking. The objective is to investigate if temocillin is non-inferior to carbapenems in the targeted treatment of bacteraemia due to 3GCR-E.

METHODS AND ANALYSIS

Multicentre, open-label, randomised, controlled, pragmatic phase 3 trial. Patients with bacteraemia due to 3GCR-E will be randomised to receive intravenously temocillin (2 g three times a day) or carbapenem (meropenem 1 g three times a day or ertapenem 1 g once daily). The primary endpoint will be clinical success 7-10 days after end of treatment with no recurrence or death at day 28. Adverse events will be collected; serum levels of temocillin will be investigated in a subset of patients. For a 10% non-inferiority margin, 334 patients will be included (167 in each study arm). For the primary analysis, the absolute difference with one-sided 95% CI in the proportion of patients reaching the primary endpoint will be compared in the modified intention-to-treat population.

ETHICS AND DISSEMINATION

The study started after approval of the Spanish Regulatory Agency and the reference institutional review board. Data will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04478721.

Efficacy of temocillin against MDR Enterobacterales: a retrospective cohort study

OBJECTIVES

EUCAST recently advised against temocillin use, except for non-serious urinary tract infections (UTI) caused by Escherichia coli, Klebsiella spp. (except Klebsiella aerogenes) and Proteus mirabilis (EKP) treated with a dose of 2 g q8h. We aimed to analyse our practice in the context of a larger temocillin use in France.

PATIENTS AND METHODS

All ≥3 day temocillin prescriptions from 2016 to 2019 were reviewed, with reference to French recommendations and a susceptibility breakpoint of 8 mg/L. The primary outcome was early clinical failure (antibiotic switch, relapse or death within 10 days after the completion of antibiotic treatment).

RESULTS

Overall, 153 cases were analysed: 123 cases of UTI (80.4%) and 133 cases of monomicrobial infection with Enterobacterales (86.9%). A total of 160 Enterobacterales were isolated, comprising 108 (67.5%) ESBL producers and 30 (20.7%) non-EKP species. The rate of early clinical failure was 9.2% and was significantly lower for UTI compared with non-UTI (4.9% versus 26.7%, P = 0.001) and for sepsis compared with severe sepsis or septic shock (6.2% versus 25%, P = 0.011). It was not different between 2 g q12h and 2 g q8h doses (10% versus 7.4%, P = 0.81) and between EKP and other Enterobacterales (8.7% versus 14.3%, P = 0.41).

CONCLUSIONS

EUCAST recommendations on urinary isolates seem to be too restrictive. Our data support the efficacy of temocillin at a dose of 2 g q12h to treat patients with non-severe complicated UTI caused by MDR Enterobacterales with an MIC of ≤8 mg/L, whatever the species.

Single-dose pharmacokinetics of temocillin in plasma and soft tissues of healthy volunteers after intravenous and subcutaneous administration: a randomized crossover microdialysis trial

BACKGROUND

The antibiotic temocillin has recently been rediscovered as a promising therapeutic option against MDR Gram-negative bacteria. However, some aspects of the pharmacokinetic (PK) profile of the drug are still to be elucidated: subcutaneous administration of temocillin might be of interest as an alternative to the intravenous route in selected patients. Similarly, information on the penetration of temocillin into human soft tissues is lacking.

OBJECTIVES

To investigate the feasibility and plasma PK of subcutaneous dosing as well as soft tissue PK of temocillin after intravenous administration to healthy volunteers.

METHODS

Eight healthy volunteers received 2 g of temocillin both as intravenous and subcutaneous infusion in a randomized two-period crossover study. Concentration-time profiles of total temocillin in plasma (after both routes) and of unbound temocillin in plasma, muscle and subcutis (only after intravenous dosing) were determined up to 12 h post-dose.

RESULTS

Subcutaneous dosing caused some infusion site discomfort but resulted in sustained drug concentrations over time with only slightly decreased overall exposure compared with intravenous dosing. Plasma protein binding of temocillin showed concentration-dependent behaviour and was higher than previously reported. Still, unbound drug concentrations in muscle and subcutis determined by microdialysis markedly exceeded those in plasma, suggesting good tissue penetration of temocillin.

CONCLUSIONS

The subcutaneous administration of temocillin is a valid and feasible alternative to intravenous dosing. With the description of plasma protein binding and soft tissue PK of temocillin in healthy volunteers, this study provides important information that adds to the ongoing characterization of the PK profile of temocillin and might serve as input for PK/PD considerations.

Temocillin dosage adjustment in a preterm infant with severe renal disease: a case report

BACKGROUND

Temocillin is a carboxypenicillin antibiotic indicated in complicated urinary tract infections due to susceptible ESBL-producing Enterobacteriaceae. While temocillin therapeutic schemes for adult patients with normal or impaired renal function are evidence based, little is known in paediatric populations.

OBJECTIVES

We report herein the management of temocillin treatment in a preterm infant with end-stage renal disease.

PATIENTS AND METHODS

The patient was a 7-month-old preterm infant born at 35 weeks gestation and treated by temocillin for 10 days for a bacteraemic urinary tract infection due to a susceptible ESBL-producing Enterobacter cloacae complex strain. Temocillin was administered by continuous infusion using a loading dose of 25 mg followed by a maintenance dose of 70 mg daily. Determination of MIC and temocillin plasma and urinary concentration was performed.

RESULTS

Clinical improvement was observed 24 h after the initiation of temocillin treatment. Temocillin concentrations ranged between 21.6 and 35.5 mg/L in urine between the first and the sixth day of treatment and between 47.0 and 61.8 mg/L in plasma after 6 and 10 days of treatment, respectively. Temocillin concentrations were found to be above the determined MIC of 6 mg/L. From the measured concentrations, we can postulate that 100%fT>MIC was achieved in urine and at least equal to 40% in plasma.

CONCLUSIONS

Temocillin dosing adjustment performed in the present reported case allowed safe and effective treatment. The strategy described herein could be used as a basis for further clinical studies relative to temocillin use in a paediatric population with renal impairment.

Temocillin as an alternative treatment for acute bacterial cholangitis: a retrospective microbiology susceptibility-based study of 140 episodes

With rising antibiotic resistance, alternatives to carbapenems are needed for acute cholangitis (AC). Temocillin reaches high biliary concentrations with limited impact on microbiota. We retrospectively included 140 AC episodes and assessed the efficacy of temocillin using microbiology susceptibility testing from blood cultures. Considering all bacteria collected by episode, resistance to temocillin, PIP/TAZ and 3GC occurred in 27/140 (26%), 32 (22.8%) and 31 (22%) episodes, respectively (p = 0.7). After documentation, temocillin could have spared PIP/TAZ or carbapenems in 14/26 and 4/11 episodes. Temocillin may constitute an alternative treatment after microbiological documentation by sparing carbapenems and/or PIP/TAZ, but not as an empirical therapeutic option.

Temocillin breakpoints in pyelonephritis: evaluation in a murine model due to ESBL-producing Escherichia coli clinical isolates

BACKGROUND

Due to a spectrum restricted to Enterobacteriaceae and stability against ESBL and AmpC enzymes, temocillin is of major interest for the treatment of pyelonephritis. But there are still uncertainties about the optimal regimen and clinical breakpoints.

OBJECTIVES

To study in a murine model of pyelonephritis the activity of temocillin against Escherichia coli isolates with different MICs in order to evaluate clinical breakpoints.

METHODS

Four clinical uropathogenic E. coli isolates with temocillin MICs of 8 mg/L (Ec8), 16 mg/L (Ec16), 32 mg/L (Ec32) and 64 mg/L (Ec64) were evaluated. Antibiotic 24 h T>MIC achieved in humans was reproduced in mice with either intravenous temocillin (2 g q12h or 2 g q8h) or intravenous imipenem (1 g q8h). Efficacy was assessed by bacterial count in kidneys.

RESULTS

Compared with controls, temocillin at 2 g q12h was highly efficient against Ec8 (-3.32 log10 cfu/g and negative cultures in 93% of mice; P < 0.001); imipenem gave similar results. Temocillin at 2 g q12h also induced high reduction of bacterial count against Ec16 (-2.92 log10 cfu/g; P < 0.001), albeit cultures were negative in only 48% of mice. In contrast, no significant effect was observed in mice infected by Ec32 (-0.01 log10 cfu/g; P = 0.981) or Ec64 (-0.55 log10 cfu/g; P = 0.523). Even temocillin at 2 g q8h failed to control Ec32 infection (-1.55 log10 cfu/g; P = 0.197).

CONCLUSIONS

This model suggests a clinical breakpoint up to 16 mg/L for non-severe pyelonephritis treated with temocillin at 2 g q12h, a value consistent with the few previous available data.

Antimicrobial Stewardship: From Bedside to Theory. Thirteen Examples of Old and More Recent Strategies from Everyday Clinical Practice

"Antimicrobial stewardship" is a strategy that promotes the responsible use of antimicrobials. The objective of this paper is to focus on consolidated and more recent improvements in clinical strategies that should be adopted in hospitalized patients to ameliorate their infectious diseases' outcome and to reduce the antibiotic resistance risk through judicious use of antibiotics. We present 13 common clinical scenarios, the respective suggested interventions and the explanations of the supporting evidence, in order to help clinicians in their decision-making process. Strategies including the choice of antibiotic and dose optimization, antibiotic spectrum narrowing (de-escalation), shortening of duration, shift to oral route or outpatient parenteral antibiotic (including elastomeric pumps), and biomarkers are described and discussed.

Activity of temocillin against ESBL-, AmpC-, and/or KPC-producing Enterobacterales isolated in Poland

We evaluated the in vitro effectiveness of temocillin and several commonly used antimicrobials against Enterobacterales bacteria in isolates from Polish patients. We tested 400 isolates: 260 extended-spectrum β-lactamase (ESBL)- and/or ampC β-lactamase (AmpC)-producing isolates; 40 Klebsiella pneumoniae carbapenemase (KPC)-producing isolates; and 100 ESBL-, AmpC-, and KPC-negative isolates. The minimal inhibitory concentrations (MICs) of temocillin and 16 other antimicrobials were determined by reference microdilution. We also determined the activities of fosfomycin and ceftazidime/avibactam in KPC-producing isolates. The antibiotic sensitivities were interpreted according to EUCAST, BSAC, and CLSI criteria. Overall, 91% of the isolates were susceptible to temocillin using the urinary tract infection breakpoint (≤ 32 mg/L), and 61.8% were susceptible using the systemic infection breakpoint (≤ 8 mg/L). Meropenem and imipenem were the most active drugs (MIC50 values of 0.06 and 0.5 mg/L, respectively). Colistin and ertapenem (both MIC50 = 0.12 mg/L) were less active than meropenem or imipenem, but some strains were 77% susceptible to each of them. Among the KPC-producing isolates, 42.5% had MIC values of ≤ 32 mg/L (urinary tract infection breakpoint), but 100% were resistant to temocillin (systemic infection breakpoint). Ceftazidime/avibactam was active against 100% of the KPC-producing isolates, and fosfomycin was active against 40%. The empirical susceptibility rate observed among the urinary isolates suggests that temocillin may be considered as an alternative to carbapenems in the absence of KPC-producing bacteria. With regard to isolates from other sources, temocillin might be useful as a documented therapy agent or an empirical treatment in hospitals with a low prevalence of ESBL/AmpC-producing strains.

Optimizing therapy of bloodstream infection due to extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE OF REVIEW

Infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are increasing worldwide. Carbapenems are usually regarded as the antibiotics of choice for the treatment of serious ESBL infections. However, because of the alarming emergence or carbapenem resistance, interest in effective alternatives has emerged. The present review summarizes the findings published on the antibiotics currently available for treatment of patients with an ESBL-E bloodstream infection (BSI).

RECENT FINDINGS

Meropenem and imipenem are the drugs recommended for treatment of ESBL BSIs in critically ill patients, and in infections with high bacterial loads or elevated β-lactam minimum inhibitory concentrations. Ertapenem should be reserved for patients with less severe presentations, and should be used at high doses. In milder presentations or BSIs from low-risk sources, other carbapenem-sparing alternatives could be considered: cephamycins, fluoroquinolones, and particularly a β-lactam/β-lactam inhibitor combination (particularly piperacillin/tazobactam). Optimized dosing of piperacillin/tazobactam is recommended (high doses and extended infusion). There are few data on the use of the promising newly available drugs (e.g. ceftolozane/tazobactam, ceftazidime/avibactam, cefiderocol, and plazomicin), and it seems reasonable to reserve them as last-resort drugs.

SUMMARY

Carbapenems should be used in patients with serious infections; alternatives could be used individually, particularly for definitive treatment of patients with milder presentations.

Activity of fosfomycin alone or combined with temocillin in vitro and in a murine model of peritonitis due to KPC-3- or OXA-48-producing Escherichia coli

Background

Alternative therapeutic regimens are urgently needed against carbapenemase-producing Enterobacteriaceae. Fosfomycin often remains active against KPC and OXA-48 producers, but emergence of resistance is a major limitation. Our aim was to determine whether the association of temocillin with fosfomycin might be useful to treat KPC- or OXA-48-producing Escherichia coli infections.

Methods

Isogenic derivatives of E. coli CFT073 with blaKPC-3- or blaOXA-48-harbouring plasmids (named CFT073-KPC-3 and CFT073-OXA-48, respectively) were used. The addition of temocillin to fosfomycin was tested using the chequerboard method and time-kill curves as well as in a fatal peritonitis murine model. Mice were treated for 24 h with fosfomycin alone or in combination with temocillin. Bacterial loads, before and after treatment, were determined in the peritoneal fluid and fosfomycin-resistant mutants were detected.

Results

Temocillin MICs were 8, 32 and 256 mg/L for CFT073 (WT), CFT073-KPC-3 and CFT073-OXA-48, respectively. Fosfomycin MIC was 0.5 mg/L for all strains. The chequerboard experiments demonstrated synergy for all three strains. In time-kill curves, combining temocillin with fosfomycin was synergistic, bactericidal and prevented emergence of resistance for CFT073-pTOPO and CFT073-KPC-3, but not CFT073-OXA-48. In vivo, for the three strains, bacterial counts were lower in peritoneal fluid with the combination compared with fosfomycin alone (P < 0.001) and inhibited growth of resistant mutants in all cases.

Conclusions

The combination of fosfomycin and temocillin demonstrated a benefit in vitro and in vivo against E. coli strains producing KPC-3 or OXA-48-type carbapenemases. This combination prevented the emergence of fosfomycin resistance and proved to be more bactericidal than fosfomycin alone.

Temocillin against Enterobacteriaceae isolates from community-acquired urinary tract infections: low rate of resistance and good accuracy of routine susceptibility testing methods

Background

Temocillin is an old 'revived' antibiotic that may play an important role in the treatment of febrile urinary tract infection (UTI). Data regarding its activity against current Enterobacteriaceae isolates as well as the performance of routine susceptibility testing methods are, however, scarce.

Objectives

To determine the MICs of temocillin for Enterobacteriaceae strains reflecting the current epidemiology and to analyse the accuracy of three commercial methods.

Methods

Enterobacteriaceae isolates causing community-acquired UTI were prospectively collected from September 2015 to January 2017 in two French centres. Temocillin MIC was determined by agar dilution (AD) as the reference method and then compared with: (i) susceptibility testing by disc diffusion; (ii) MIC determination by Etest; and (iii) MIC estimation by the Vitek 2 automated system.

Results

A total of 762 Enterobacteriaceae were analysed comprising 658 (86.4%) Escherichia coli and 37 (4.9%) ESBL-producing isolates. Susceptibility rate assessed by AD was 99.6% according to the 8 mg/L clinical breakpoint and was significantly lower against the ESBL-producing isolates than the non-ESBL-producing isolates (94.6% versus 99.9%, P < 0.01). The MIC50 and MIC90 for the total set were 3 and 6 mg/L, respectively. According to the 8 mg/L clinical breakpoint, the major error rate was <1% for disc diffusion and Etest, and significantly higher for Vitek 2 (4.3%, P < 0.01), but still low. No very major error was noticed.

Conclusions

Temocillin showed a high level of activity against Enterobacteriaceae from community-acquired UTI and good to excellent reliability of routine methods for susceptibility testing in such a setting.

AmpC β-lactamase-producing Enterobacterales: what a clinician should know

BACKGROUND

Enterobacterales are among the most common causes of bacterial infections in the community and among hospitalized patients, and multidrug-resistant (MDR) strains have emerged as a major threat to human health. Resistance to third-generation cephalosporins is typical of MDRs, being mainly due to the production of extended spectrum β-lactamases or AmpC-type β-lactamases.

OBJECTIVE

The objective of this paper is to review the epidemiological impact, diagnostic issues and treatment options with AmpC producers.

FINDINGS

AmpC enzymes encoded by resident chromosomal genes (cAmpCs) are produced by some species (e.g., Enterobacter spp., Citrobacter freundii, Serratia marcescens), while plasmid-encoded AmpCs (pAmpCs) can be encountered also in species that normally do not produce cAmpCs (e.g., Salmonella enterica, Proteus mirabilis, Klebsiella pneumoniae and Klebsiella oxytoca) or produce them at negligible levels (e.g., Escherichia coli). Production of AmpCs can be either inducible or constitutive, resulting in different resistance phenotypes. Strains producing cAmpCs in an inducible manner (e.g., Enterobacter spp.) usually appear susceptible to third-generation cephalosporins, which are poor inducers, but can easily yield mutants constitutively producing the enzyme which are resistant to these drugs (which are good substrates), resulting in treatment failures. pAmpCs are usually constitutively expressed. Production of pAmpCs is common in community-acquired infections, while cAmpC producers are mainly involved in healthcare-associated infections.

CONCLUSIONS

To date, there is no conclusive evidence about the most appropriate treatment for AmpC-producing Enterobacterales. Carbapenems are often the preferred option, especially for severe infections in which adequate source control is not achieved, but cefepime is also supported by substantial clinical evidences as an effective carbapenem-sparing option.

Carbapenems and alternative β-lactams for the treatment of infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae: What impact on intestinal colonisation resistance?

The ongoing pandemic of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is responsible for a global rise in carbapenem consumption that may hasten the dissemination of carbapenemase-producing Enterobacteriaceae (CPE). Hence, carbapenem sparing through the use of alternative β-lactams is increasingly considered as a potential option in patients with ESBL-E infections. However, at the individual level, this strategy implies an in-depth understanding of how carbapenems and their alternatives impair the gut microbiota, especially the anaerobic bacteria and the colonisation resistance (CR) that it confers. In this review, we sought to appraise the impact of carbapenems and their main alternatives for ESBL-E infections (namely β-lactam/β-lactamase inhibitor combinations, cephamycins and temocillin) on the gut ecosystem and the resulting hazard for acquisition of CPE. Although limited, the available evidence challenges our perception of the ecological side effects of these antimicrobials and highlights knowledge gaps regarding antibiotic-induced alterations in intestinal CR. These alterations may depend not only on anti-anaerobic properties but also on a panel of parameters with marked interindividual variability, such as baseline characteristics of the gut microbiota or the degree of biliary excretion for the considered drug. In the current context of ESBL-E dissemination and increasing opportunities for carbapenem-sparing initiatives, large, comparative, high-quality studies based on new-generation sequencing tools are more than ever warranted to better define the positioning of alternative β-lactams in antimicrobial stewardship programmes.