Selection of AmpC ß-Lactamase Variants and Metallo-ß-Lactamases Leading to Ceftolozane/Tazobactam and Ceftazidime/Avibactam Resistance during Treatment of MDR/XDR Pseudomonas aeruginosa Infections.

Infections caused by ceftolozane-tazobactam and ceftazidime-avibactam-resistant P. aeruginosa infections are an emerging concern. We aimed to analyze the underlying ceftolozane-tazobactam and ceftazidime-avibactam resistance mechanisms in all multidrug-resistant or extensively drug-resistant (MDR/XDR) P. aeruginosa isolates recovered during 1 year (2020) from patients with a documented P. aeruginosa infection. Fifteen isolates showing ceftolozane-tazobactam and ceftazidime-avibactam resistance were evaluated. Clinical conditions, previous positive cultures, and ß-lactams received in the previous month were reviewed for each patient. MICs were determined by broth microdilution. Multilocus sequence types (MLSTs) and resistance mechanisms were determined using short- and long-read whole-genome sequencing (WGS). The impact of Pseudomonas-derived cephalosporinases (PDCs) on ß-lactam resistance was demonstrated by cloning into an ampC-deficient PAO1 derivative (PAOΔC) and construction of 3D models. Genetic support of acquired ß-lactamases was determined in silico from high-quality hybrid assemblies. In most cases, the isolates were recovered after treatment with ceftolozane-tazobactam or ceftazidime-avibactam. Seven isolates from different sequence types (STs) owed their ß-lactam resistance to chromosomal mutations and all displayed specific substitutions in PDC: Phe121Leu and Gly222Ser, Pro154Leu, Ala201Thr, Gly214Arg, ΔGly203-Glu219, and Glu219Lys. In the other eight isolates, the ST175 clone was overrepresented (6 isolates) and associated with IMP-28 and IMP-13, whereas two ST1284 isolates produced VIM-2. The cloned PDCs conferred enhanced cephalosporin resistance. The 3D PDC models revealed rearrangements affecting residues involved in cephalosporin hydrolysis. Carbapenemases were chromosomal (VIM-2) or plasmid-borne (IMP-28, IMP-13) and associated with class-1 integrons located in Tn402-like transposition modules. Our findings highlighted that cephalosporin/ß-lactamase inhibitors are potential selectors of MDR/XDR P. aeruginosa strains producing PDC variants or metallo-ß-lactamases. Judicious use of these agents is encouraged.

[Antimicrobial susceptibility of Escherichia coli producers of community urinary tract infections in Galicia (Spain). Period: 2016-2017]. / Estudio de sensibilidad de Escherichia coli productores de infecciones del tracto urinario comunitarias en Galicia. Período: 2016-2017.

OBJECTIVE: Escherichia coli (E. coli) is responsible for the majority of community urinary tract infections. The objective of the study is to know the sensitivity spectrum of E. coli in urinary tract infections to be able to recommend the appropriate empirical antibiotic treatment. DESIGN: Cross-sectional, multicentric, retrospective study. LOCATION: Galician 8 public hospitals, practically the entire population of Galicia (Spain). PARTICIPANTS: 43,137 outpatients with urinary tract infection due to E. coli isolated in urine in 2016/2017. MAIN MEASUREMENTS: Analyzed variables: demographic, minimum inhibitory concentration and interpretation of sensitivity according to CLSI criteria and resistance mechanisms. The antibiotics studied were: ampicillin, amoxicillin-clavulanic acid, ciprofloxacin, cefotaxime, cefepime, gentamicin, nitrofurantoin, fosfomycin, cotrimoxazole, imipenem and ertapenem. The identification and sensitivity were made mainly by automated methods. RESULTS: The percentages of non-sensitivity of E. coli isolates were: ampicillin 49.2%, amoxicillin-clavulanic acid 17.8%, cefotaxime 6.7%, cefepime 5.7%, ertapenem 0.04%, imipenem 0.05%, gentamicin 9,1%, ciprofloxacin 26.2%, fosfomycin 3.3%, nitrofurantoin 2.4% and cotrimoxazole 23.9%. The non-sensitivities were higher in men and as age increases. Six percent of E. coli were producers of extended-spectrum beta-lactamases. CONCLUSIONS: The empirical treatment in Galicia for uncomplicated cystitis produced by E. coli in women continues to be nitrofurantoin and fosfomycin. In men under 15 years of age, fosfomycin is indicated and in men older than 15 years, treatment in our environment should include culture and administer a 3rd generation oral cephalosporin empirically. Cotrimoxazole and ciprofloxacin are not recommended as empirical treatment because of their high resistance rates.

Adsorption of Heavy Metals Ions from Mining Metallurgical Tailings Leachate Using a Shell-Based Adsorbent: Characterization, Kinetics and Isotherm Studies.

This study defines the optimal parameters that allow the use of waste mollusk shells (WS) to remove heavy metals from three mining and metallurgical leachates. First, the influence of parameters such as pH, contact time, initial metal concentration, adsorbent dose and the presence of co-ions in Cu2+, Cd2+, Zn2+ and Ni2+ adsorption was investigated in synthetic solutions. Metal uptake was found to be dependent on the initial pH of the solution, the removal rate increasing with the increase in pH, showing the highest affinity at pH 5-6. The removal efficiency at lower concentrations was greater than at higher values. The competitive adsorption results on bimetallic solutions showed that the adsorption capacity of the sorbent was restricted by the presence of other ions and suppressed the uptake of heavy metals compared to the single adsorption. Cu2+ was the metal that most inhibited the removal of Cd2+, Zn2+ and Ni2+. The Langmuir isotherm provided the best fit to the experimental data for Cu2+, Cd2+ and Zn2+ and the Freundlich isotherm, for Ni2+. The data showed that the maximum adsorption capacity amax for Zn2+, Cd2+ and Cu2+, was 526.32 mg g-1, 555.56 mg g-1 and 769.23 mg g-1, respectively. Sorption kinetics data best fit the pseudo-second-order kinetic model. The results obtained in the tests with three mining and metallurgical leachates showed that WS were effective in simultaneously removing several heavy metals ions such as Cu, Ni, Zn, Cd, Ni, As and Se.

[Surveillance of antimicrobial susceptibility of Escherichia coli producing urinary tract infections in Galicia (Spain)]. / Vigilancia de la sensibilidad a antimicrobianos de Escherichia coli productor de infecciones del tracto urinario comunitarias en Galicia.

OBJECTIVE: Escherichia coli is the microorganism responsible for most of the community-acquired urinary tract infections (UTI). Our purpose was to determine the susceptibility of E. coli associated with UTI in Galicia and consider the most appropriate antibiotics for empirical treatment. METHODS: Retrospective study during the period 2011- 2012 of the isolation of E. coli in urine samples from almost all the Galician population. Demographic variables, minimum inhibitory concentration, and reading data were collected: amoxicillin-clavulanate, cefotaxime, gentamicin, amikacin, ciprofloxacin, cotrimoxazole, nitrofurantoin and fosfomycin. The identification and susceptibility studies were mainly conducted by automated systems. The interpretation of the results was performed according to CLSI criteria. RESULTS: During the study period 55,046 E. coli were isolated in UTI. The percentages of resistance were: cotrimoxazole, 30%; ciprofloxacin, 33%; amoxicillin-clavulanate, 23% and 10% for 3rd generation cephalosporins. Fosfomycin and nitrofurantoin showed the highest activity with more than 96% of susceptibility in our study. The linear trend of resistance regarding age was statistically significant (p <0.0001) as it was regarding males (p <0.00001) for all antibiotics. CONCLUSIONS: In Galicia, the most active antibiotics against E. coli associated with UTI are fosfomycin and nitrofurantoin so they should be considered as empirical treatment of choice by the community-acquired UTI not complicated by E. coli.

[Surveillance of resistance of Staphylococcus aureus to antibiotics in Galicia: 2007-2012]. / Vigilancia de la resistencia a los antibióticos en Staphylococcus aureus en Galicia: 2007-2012.

INTRODUCTION: Since 2007 the Galician Surveillance Program on Antimicrobial Resistance has been collected data of Staphylococcus aureus susceptibility patterns. The data from 2007 to 2012 have been analyzed and are reported. METHODS: A total of 4,577 different isolates of S. aureus from cerebrospinal fluid and blood cultures were included. The Institutions involved provided the information about the susceptibility patterns, the assay methods used and the interpretative guidelines followed, and demographic data of patients. RESULTS: The rate of methicillin-resistance S. aureus (MRSA) was 22% in 2007-2010 and 26% in 2011-2012, although in some areas the percentage reached 57% (2007- 2010) or 66% (2011-2012). The higher rates of resistance were found in patients older than 75 years. Gentamycin resistance was less than 9% and for quinolones were about 25%. A strong association between methicillin and quinolone-resistance were observed (91%). The resistance against linezolid and glycopeptides were exceptional. CONCLUSIONS: The percentage of MRSA has evolved slightly along the period of this study reaching no significant differences between Galicia and the global data in Spain in 2012. Nevertheless, there are significant differences among the geographic areas studied. Most MRSA isolates were recovered from hospitalized patients, but an increase in the number of MRSA among outpatients was observed, while old patients from nursing homes are included in the outpatient group, so the MRSA rate in this group could be overestimated.