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T he growing prevalence of nosocomial infections produced by multidrug-resistant (MDR) and extensively multidrug-resistant (XDR) Pseudomonas aeruginosa strains is associated with significantly increased morbidity and mortality (1). This increasing threat results from the extraordinary capacity of P. aeruginosa for developing resistance to nearly all available antibiotics by the selection of mutations in chromosomal genes, the growing prevalence of transferable resistance determinants (such as carbapenemases or extended-spectrum ␤-lactamases [ESBLs]), and the global dissemination of MDR/XDR strains, the so-called high-risk clones (2, 3). The recent introduction of novel ␤-lactam-␤-lactamase inhibitor combinations, such as ceftolozane-tazobactam or ceftazidime-avibactam, has substantially improved our arsenal for combating infections by MDR/XDR P. aeruginosa (1, 4, 5). However, ceftolozanetazobactam or ceftazidime-avibactam are not effective against horizontally acquired class B carbapenemases (metallo-␤-lactamases), which are a growing threat in hospitals worldwide (2). Moreover, while ceftolozane-tazobactam or ceftazidime-avibactam are stable against hydrolysis by the intrinsic chromosomal cephalosporinase AmpC from P. aeruginosa, resistance may emerge during treatment due to the selection of mutations in the ⍀-loop of the ␤-lactamase (6, 7). Here, we describe a case of ceftolozanetazobactam and ceftazidime-avibactam resistance caused by the production of a horizontally acquired AmpC ␤-lactamase, adding further complexity and concern to the current scenario of P. aeruginosa resistance mechanisms. In 2017, an XDR P. aeruginosa strain (HUIGC-PA1) was isolated from a urine sample obtained from a urinary catheter of a female spine trauma patient transferred for rehabilitation to Hospital Universitario Insular de Gran Canaria (Gran Canaria, Spain) 1 week previously. During the prior 2 months, the patient had received several broadspectrum antibiotics, including cefotaxime and cefepime, for hospital-acquired pneumonia (Escherichia coli) and wound infections (Staphylococcus epidermidis). The isolation of XDR P. aeruginosa from the urine was considered colonization, and the patient was discharged 2 months later without antibiotic treatment. The susceptibility profile of HUIGC-PA1 is shown in Table 1. The strain was resistant or showed borderline susceptibility to all ␤-lactams tested (including ceftolozanetazobactam and ceftazidime-avibactam), tobramycin, and ciprofloxacin, remaining only susceptible to amikacin and colistin. Phenotypic and molecular assays for horizontally acquired carbapenemases and ESBLs (8) yielded negative results. Therefore, the strain was subjected to whole-genome sequencing (WGS) using previously described approaches (9) to determine the potential mechanisms involved. The presence of hori-Citation Fraile-Ribot PA, del Rosario-Quintana C, López-Causapé C, Gomis-Font MA, Ojeda-Vargas M, Oliver A. 2020. Emergence of resistance to novel β-lactam-β-lactamase inhibitor combinations due to horizontally ...

Microbial contamination in shopping trolleys (eighty five) by considering different supermarkets (seven) from three major food companies in Las Palmas de Gran Canaria (Spain) was determined. The two sampled areas were trolley handles and food trolley baskets-child seats. Samples were analyzed by selective and differential microbiological culture media. E. coli four (2.4%) indicative of faecal contamination, Klebsiella pneumoniae twelve (6.5%) and Citrobacter freundii, six (5.1%), which have been isolated from human faecal samples, were isolated from trolleys; Pseudomonas rhodesiae, five (4.25%), and Pseudomonas fluorescens, three (2.55%), which both evidenced environmental contamination. Significant differences among the companies were found for the Enterobacteriaceae and coliforms. Regarding location, these differences (p < 0.003) were observed only for the coliform rates, which were higher in trolleys located outside. The results of this study suggest the implementation of cleaning and disinfection programmes to improve trolley sanitation, and to reduce exposure to both potential pathogenic and transmitting bacterial infections.

New cases of blue cheese discoloration has led to recent research to identify the causal agent and factors that favor blue pigment appearing. Nonetheless, very few reports have described the source of contamination and the measurements to eradicate the microbiological source on cheese farms by determining the relation between blue discoloration on fresh cheese and the Pseudomonas fluorescens group. Thus, 60 samples from a cheese farm (cheese, equipment surfaces, tap water, and raw and pasteurized milk) were analyzed by phenotypical, MALDI-TOF, 16S rRNA sequencing and pulsed-field gel electrophoresis tests to determine the causal agent. The results obtained by pulsed-field gel electrophoresis with restriction enzymes XbaI and SpeI confirmed tap water as the initial contaminated source. The above-mentioned result was essential to avoid Pseudomonas contamination due to the most residual microorganisms being inactivated through a new disinfection program.