Short CommunicationResistance to quinolones, cephalosporins and macrolides in Escherichia coli causing bacteraemia in Peruvian children
Introduction
Bloodstream infections (BSIs) are a major cause of morbidity and mortality worldwide, with Escherichia coli being considered one of the most relevant pathogens, especially in early-onset neonatal sepsis [1]. Third-generation cephalosporins are one of the main treatment options for neonatal and childhood BSIs. Other antimicrobial agents, such as fluoroquinolones, also play a key role in the treatment of neonatal BSIs in the case of multidrug-resistant (MDR) micro-organisms or as rescue treatment [2]. A continuous rise in antimicrobial resistance has been observed globally [3], [4], [5], [6], causing treatment failures with associated case fatality and leading to increasing hospital costs [4].
Extended-spectrum β-lactamases (ESBL) confer resistance to cephalosporins and monobactams [4], [7], [8]. Infections caused by ESBL-producing bacteria have been associated with poor outcomes and increasing mortality rates [4], [9]. ESBL proportions in Peru range from 54% to 77% in hospital settings, representing the highest proportion in the region [5], [10], [11]. In addition to ESBLs, so-called plasmid-encoded AmpC (pAmpC) enzymes, also involved in the acquisition of cephalosporin resistance, are being increasingly reported. Usually, cephalosporin-resistant micro-organisms present a MDR profile [8], [11], becoming a higher risk for treatment failure both with cephalosporins and other antimicrobial agents [7]. Resistance determinants to other antibiotics may be located on different genetic structures, often together ESBLs or pAmpCs. These determinants include, amongst others, transferable mechanisms of quinolone resistance (TMQR) or macrolide resistance (TMMR) [7], [8].
TMQR, which are widespread worldwide, usually decrease levels of quinolone susceptibility, facilitating both therapeutic failures as well as the acquisition of new mechanisms of quinolone resistance leading to full resistance to these agents, acting in an additive manner either among them or with other quinolone resistance mechanisms [12].
Previous macrolide exposure has been reported as risk factor for the development of ESBL-producing Klebsiella pneumoniae BSI [13], although macrolides are only used in specific BSIs such as those related to Salmonella spp. [14]. Moreover, the role of E. coli as a TMMR reservoir has been highlighted [14].
This study aimed to characterise the β-lactam, quinolone and macrolide resistance mechanisms among clinical E. coli isolates causing bacteraemia in Peruvian children.
Section snippets
Micro-organisms
A total of 62 non-duplicate E. coli BSI isolates (Supplementary Table S1) previously characterised at virulence, phylogenetic and clonal levels [15] from children aged <5 years from 12 hospitals in Lima (Peru) were analysed.
Antimicrobial susceptibility testing
Minimum inhibitory concentrations (MICs) to azithromycin (AZM), nalidixic acid (NAL) and ciprofloxacin (CIP) were determined in the absence (MICI) and presence (MICPAβN) of 20 mg/L of the efflux pump inhibitor Phe-Arg-β-naphthylamide (PAβN) [16]. An effect of PAβN on the MIC
Antimicrobial resistance
Antimicrobial resistance is emerging worldwide, requiring integral surveillance to better understand its dynamics and evolution. In the present study, high levels of resistance to almost all tested antimicrobial agents were observed. Resistance to ampicillin was observed in 58 isolates (93.5%), followed by NAL and SXT (41 isolates each; 66.1%) and AZM (25 isolates; 40.3%). On the other hand, no resistance to imipenem or meropenem was detected, and only two nitrofurantoin-intermediate isolates
Conclusions
The present results show the variety of ESBLs and the widespread of blaCTX-M-15 in Peruvian bacteraemic isolates. Moreover, the association between quinolone resistance and ESBLs highlights the need to implement control in the use of antimicrobial agents. Further evaluations of the relevance of efflux pumps in the development of macrolide resistance as well as surveillance of the molecular mechanisms of resistance present in the area need to be developed.
Funding
JR has a fellowship from the program I3SNS of the ISCIII [grant no. CES11/012]; MJP has a postdoctoral fellowship from CONCYTEC/FONDECYT [grant no. CG05-2013-FONDECYT]; CG had a predoctoral grant from the ISCIII [FI12/00561]. This work was supported by: Agencia Española de Cooperación Internacional para el Desarrollo (AECID), Spain, Programa de Cooperación Interuniversitaria e Investigación Científica con Iberoamérica [D/019499/08, D/024648/09, D/030509/10 and A1/035720/11]; Spanish Network for
Competing interests
None declared.
Ethical approval
This study was reviewed and approved by the Ethics Committee of the Universidad Peruana Cayetano Heredia (Lima, Peru) and by those of the participating hospitals.
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