Risk factors and outcome associated with infection or colonization due to carbapenem-heteroresistant Escherichia coli

Economic and human burden attributable to antimicrobial resistance in Spain: a holistic macro-estimation of costs

Antimicrobial resistance (AMR) represents a major threat to medical practice, complicating infection management, and increasing mortality and healthcare costs. Macro estimations of this health issue remain underexplored because data are currently limited to hospital systems. This study aims to estimate the economic and human burden of AMR in Spain at a macro level. An economic model was constructed based on prevalence rates, premature deaths and published literature to assess costs. Methodology was based on several techniques depending on the type of cost to be estimated: hospital inpatient care costs (based on extra hospital days); outpatient care costs (employing reimbursement rates from regional health services); productivity losses due to premature deaths (using the Human Capital Approach) and morbidity (based on days absent from work). Using data from EARS-NET, ESAC-NET and GBD, a total of 30 bacteria-drug resistance combinations were analysed. The results showed that 77,870 infections, 6,199 premature deaths, and 426,495 extra hospital days were attributable to AMR in Spain, mostly due to Gram-negative bacteria. AMR was also responsible for 3,112 years of working life lost. The costs reached EUR 338.6 million (0.03% of GDP), costing each Spaniard EUR 7.15 per year. Direct costs accounted for 72% of total costs, while indirect costs represented 28%. To date, this is the first study that evaluates the cost of AMR across such a wide range of bacteria and infection sites. These estimates are useful for approximating the problem and for planning containment and action strategies.

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.