Antimicrobial resistance rates of Streptococcus pyogenes in a Greek tertiary care hospital: 6-year data and literature review.

Streptococcus pyogenes is responsible for various clinical manifestations in patients of all ages worldwide. Worryingly, an increase in antibiotic resistance rates of S. pyogenes has been observed in many countries. In the present study, 6-year data are presented regarding the antibiotic resistance rates of S. pyogenes in our hospital. During this period, a total of 52 S. pyogenes isolates were recovered from 52 patients and antimicrobial susceptibility testing was performed for 49 isolates. All were susceptible to penicillin, ampicillin, cefotaxime, ceftriaxone, linezolid, moxifloxacin, rifampicin, vancomycin, teicoplanin, and tigecycline. Erythromycin and clindamycin resistance rates were 20.4% and 18.8% respectively. Resistance rates to tetracycline were 40.8%, to chloramphenicol 6.9%, and to levofloxacin 2%. Since macrolides are recommended as an alternative treatment in case of allergy to ß-lactams, the high macrolide resistance rates are causing concern. Because different phenotypic antimicrobial patterns for S. pyogenes have been observed in different geographic areas, epidemiological data is of considerable value for the appropriate treatment choices.

In Vitro Synergistic Activity of Antimicrobial Combinations against Carbapenem- and Colistin-Resistant Acinetobacter baumannii and Klebsiella pneumoniae.

Polymyxins are commonly used as the last resort for the treatment of MDR Acinetobacter baumannii and Klebsiella pneumoniae nosocomial infections; however, apart from the already known toxicity issues, resistance to these agents is emerging. In the present study, we assessed the in vitro synergistic activity of antimicrobial combinations against carbapenem-resistant and colistin-resistant A. baumannii and K. pneumoniae in an effort to provide more options for their treatment. Two hundred A. baumannii and one hundred and six K. pneumoniae single clinical isolates with resistance to carbapenems and colistin, recovered between 1 January 2021 and 31 July 2022,were included. A. baumannii were tested by the MIC test strip fixed-ratio method for combinations of colistin with either meropenem or rifampicin or daptomycin. K. pneumoniae were tested for the combinations of colistin with meropenem and ceftazidime/avibactam with aztreonam. Synergy was observed at: 98.99% for colistin and meropenem against A. baumannii; 91.52% for colistin and rifampicin; and 100% for colistin and daptomycin. Synergy was also observed at: 73.56% for colistin and meropenem against K. pneumoniae and; and 93% for ceftazidime/avibactam with aztreonam. The tested antimicrobial combinations presented high synergy rates, rendering them valuable options against A. baumannii and K. pneumoniae infections.

Phenotypic and molecular characterization of blaCTX-M-3 and blaCTX-M-55-producing monophasic Salmonella enterica serovar Typhimurium in Greece.

OBJECTIVES: To characterize three Salmonella enterica serovar Typhimurium strains using whole genome sequencing (WGS) and conventional methods. The isolates were recovered from three pediatric patients in Greece as part of the hospital's epidemiological surveillance system during 2016 to 2018. METHODS: Bacterial identification and antimicrobial susceptibility testing was performed using the VITEK 2 automated system, disc diffusion test, and MIC gradient test while serotyping by the slide agglutination method. Detection of resistance genes, eBurst groups (eBG), assignment to sequence types, single nucleotide polymorphism (SNP) typing, location and characterization of drug resistance regions, and in silico plasmid detection were carried out using WGS. RESULTS: All strains were identified as S. Typhimurium-monophasic, ST34, eBG1 with antigenic formula 1,4, [5], 12:i:-. They were phenotypically resistant to most antibiotics tested except piperacillin/tazobactam, imipenem, and co-trimoxazole. WGS revealed the chromosomally located genes encoding the ASSuT (ampicillin, streptomycin, sulfonamides, and tetracycline) resistant pattern in all three strains. WGS revealed extended spectrum ß-lactamase (ESBL) production in all three strains, the presence of blaCTX-M-3 on an IncI1 plasmid in two strains isolated in 2018, and the chromosomally encoded blaCTX-M-55 plus qnrS1 (resistance to ciprofloxacin) in the strain isolated in 2016. The two strains from 2018 were isolated from the same hospital ward and were genetically related. CONCLUSIONS: The emergence of ESBL among S. 1,4,[5], 12:i:- is worrisome due to its increasing antimicrobial resistance phenotype, making clinical treatment difficult. WGS provides an alternative to traditional methods of identification and genomic characterisation of strains, and serves to better understand their epidemiological dynamics and bacterial pathogenesis.

In vitro activity of ceftaroline against methicillin-resistant and methicillin-susceptible Staphylococcus aureus clinical isolates from a tertiary hospital in Greece.

Ceftaroline is a novel cephalosporin able to bind to and inhibit PBP2a, and thus active against methicillin-resistant Staphylococcus aureus. In the present study we assessed the in vitro activity of ceftaroline and comparators against a large sample of methicillin-resistant and methicillin-susceptible S. aureus isolates collected at our hospital. Overall, both MRSA and MSSA isolates in our study were sensitive to ceftaroline, even though the MIC range was higher for MRSAs (0.12-2 mg/L against ≤0.06-0.5 mg/L for MSSAs). Our results indicate that ceftaroline may be considered a reliable alternative for the treatment of MRSA.

Performance evaluation of Alfred60AST rapid susceptibility testing directly from positive blood cultures in the routine laboratory workflow.

The aim of this study was to evaluate the performance of the new automated system Alfred60AST which is based on light scattering technology for rapid susceptibility testing directly from positive blood cultures as well as its applicability in the routine laboratory workflow. We evaluated 176 significant episodes of bacteremia due to 92 Gram-negative and 84 Gram-positive bacteria. The antimicrobial agents tested were ceftriaxone, ciprofloxacin, gentamicin, meropenem, piperacillin-tazobactam, and colistin for Gram negatives and cefoxitin, vancomycin, linezolid, and daptomycin for Gram positives. Concordance assessment was performed in comparison with our routine method, Vitek2 (bioMérieux). Discrepancies were resolved with MICRONAUT-S (Merlin) or E-test (bioMérieux). Out of 690 susceptibility determinations, 94.05% showed categorical agreement (CA) with the routine method and this percentage increased to 94.49 after discrepancy analysis. There were 1.45% very major errors, 3.33% major errors, and 1.16% minor errors (decreased to 1.45, 3.04, and 1.01 after discrepancy analysis). The CA for most of the antibiotics was above 90% except for daptomycin for Gram positives (87.30%) and ceftriaxone for Gram negatives (88.23%). The concordance was slightly better for Gram negative than for Gram-positive bacteria (94.30 versus 93.70%, respectively). The total turnaround time for a complete Alfred60AST result was 6-6.5h. The evaluated method gave rapid and reliable results in a few hours, versus 48h for the conventional one. Implementing this technology in routine workflow allows clinicians to optimize the treatment on the same day of blood culture positivity with potential positive clinical benefits and impact on antibiotic stewardship.

Microbiological characteristics of bacteremias among COVID-19 hospitalized patients in a tertiary referral hospital in Northern Greece during the second epidemic wave.

Northern Greece was struck by an intense second COVID-19 (coronavirus disease 2019) epidemic wave during the fall of 2020. Because of the coinciding silent epidemic of multidrug-resistant organisms, the handling of COVID-19 patients became even more challenging. In the present study, the microbiological characteristics of bacteremias in confirmed cases of hospitalized COVID-19 patients were determined. Data from 1165 patients hospitalized between September and December 2020 were reviewed regarding the frequency of bloodstream infections, the epidemiology and the antibiotic susceptibility profiles of the causative bacteria. The hospital's antibiotic susceptibility data for all major nosocomial pathogens isolated from bacteremias of COVID-19 patients between September and December 2020 versus those between September and December 2019 were also compared. Overall, 122 patients developed bacteremia (10.47%). The average of time interval between hospitalization date and development of bacteremia was 13.98 days. Admission to ICU occurred in 98 out of 122 patients with an average stay time of 15.85 days and 90.81% in-hospital mortality. In total, 166 pathogens were recovered including 114 Gram-negative bacteria and 52 Gram-positive cocci. Acinetobacter baumannii was the most frequent (n = 51) followed by Klebsiella pneumoniae (n = 45) and Enterococcus faecium (n = 31). Bacteremias in hospitalized COVID-19 patients were related with prolonged time of hospitalization and higher in-hospital mortality, and the isolated microorganisms represented the bacterial species that were present in our hospital before the COVID-19 pandemic. Worryingly, the antibiotic resistance rates were increased compared with the pre-pandemic era for all major opportunistic bacterial pathogens. The pandemic highlighted the need for continuous surveillance of patients with prolonged hospitalization.