As multidrug resistance gains momentum, the last two decades have seen an ever-growing interest in the antimicrobial properties of plant extracts and plant-derived compounds. Most of the focus is on polyphenols – a large and diverse group of phytochemicals with strong antibacterial activity. Testing methods provide reliable results as long as they follow standard procedures. However, methods and procedures used in antimicrobial susceptibility testing (AST) are often too diverse to allow comparison of results. The lack of uniformity and comparability is much owed to the absence of guidelines. The focus of this review is to give a critical overview of different methods used in the assessment of polyphenols antimicrobial efficacy and to highlight the importance of their standardisation.

Pseudomonas aeruginosa is an opportunistic pathogen, one of the leading causes of nosocomial infections such as pneumonia, urinary tract infections, and bacteraemia. The bacterial resistance to structurally unrelated antibiotics and its spread within hospitals limits the efficient antimicrobial options and patients' outcome. Carbapenems are important agents for the therapy of infections due to multidrug-resistant (MDR) P. aeruginosa ; hence, the development of carbapenem resistance severely hampers effective therapeutic options. The aim of this investigation was to examine mechanisms of carbapenem resistance and genomic diversity in carbapenem-resistant MDR strains of P. aeruginosa , which caused an outbreak among patients in Clinical Hospital Rijeka. Most of the isolates showed decreased expression of porin that is important for the entry of carbapenems ( oprD ). Overexpression of MexAB-OprM, MexCD-OprJ, and MexEF-OprN efflux systems was observed in many of the isolates. Production of metallo-β-lactamases was not detected. Typing by pulsed-field gel electrophoresis discriminated the isolates into five clusters. The clonal distribution of the strains was related to the location of hospital departments where the isolates were collected, which implies that most of the infections were caused by spread of the epidemic strains within the hospital.

Purpose. A dramatic increase in OXA-48 β-lactamase was observed recently not only in large hospital centres, but also in smaller suburban hospital centres in geographic areas bordering Croatia. The aim of the study was to analyse the epidemiology, the mechanisms of antibiotic resistance and the routes of spread of OXA-48 carbapenemase in Croatia. Methods. Carbapenemase and other β-lactamase and fluoroquinolone resistance genes were detected by PCR and sequencing. Whole-genome sequencing (WGS) was performed on five representative isolates. The isolates were genotyped by PFGE. Results. Forty-eight isolates positive for OXA-48, collected from seven hospital centres in Croatia from May 2016 to May 2017, were analysed (40 Klebsiella pneumoniae, 5 Enterobacter cloacae, 2 Escherichia coli and one Citrobacter freundii). Thirty-three isolates were ESBL positive and harboured group 1 CTX-M 1 β-lactamases. In addition to the β-lactam resistance genes detected by PCR (bla SHV-1, bla OXA-48 and bla OXA-1), WGS of five representative isolates revealed the presence of genes encoding aminoglycoside resistance, aadA2 and aph3-Ia, fluoroquinolone resistance determinants aac(6)Ib-c, oqxA and oqxB, the sulfonamide resistance gene sul1, and fosA (fosfomycin resistance). IncL plasmid was found in all isolates. Two K. pneumoniae isolates belonged to ST16, two E. cloacae to ST66 and E. coli to ST354. K. pneumoniae isolates were allocated to five clusters by PFGE which occured in different hospitals, indicating epidemic spread. Conclusions. The OXA-48-positive organisms found in this study showed wide variability in antibiotic susceptibility, β-lactamase content and PFGE banding patterns. This study revealed a switch from the predominance of VIM-1 in 2012–2013 to that of OXA-48 in the 2015 to 2017.