In vitro activities of omadacycline, eravacycline, cefiderocol, apramycin, and comparator antibiotics against Acinetobacter baumannii causing bloodstream infections in Greece, 2020-2021: a multicenter study.

Resistance of Acinetobacter baumannii to multiple clinically important antimicrobials has increased to very high rates in Greece, rendering most of them obsolete. The aim of this study was to determine the molecular epidemiology and susceptibilities of A. baumannii isolates collected from different hospitals across Greece. Single-patient A. baumannii strains isolated from blood cultures (n = 271), from 19 hospitals, in a 6-month period (November 2020-April 2021) were subjected to minimum inhibitory concentration determination and molecular testing for carbapenemase, 16S rRNA methyltransferase and mcr gene detection and epidemiological evaluation. 98.9% of all isolates produced carbapenemase OXA-23. The vast majority (91.8%) of OXA-23 producers harbored the armA and were assigned mainly (94.3%) to sequence group G1, corresponding to IC II. Apramycin (EBL-1003) was the most active agent inhibiting 100% of the isolates at ≤16 mg/L, followed by cefiderocol which was active against at least 86% of them. Minocycline, colistin and ampicillin-sulbactam exhibited only sparse activity (S <19%), while eravacycline was 8- and 2-fold more active than minocycline and tigecycline respectively, by comparison of their MIC50/90 values. OXA-23-ArmA producing A. baumannii of international clone II appears to be the prevailing epidemiological type of this organism in Greece. Cefiderocol could provide a useful alternative for difficult to treat Gram-negative infections, while apramycin (EBL-1003), the structurally unique aminoglycoside currently in clinical development, may represent a highly promising agent against multi-drug resistant A. baumanni infections, due to its high susceptibility rates and low toxicity.

Characterization of 16S rRNA methylase genes in Enterobacterales and Pseudomonas aeruginosa in Athens Metropolitan area, 2015-2016.

The aim of this study was to characterize the 16S rRNA methylase (RMT) genes in aminoglycoside-resistant Enterobacterales and Pseudomonas aeruginosa isolates in 2015-2016 in hospitals in Athens, Greece. Single-patient, Gram-negative clinical isolates resistant to both amikacin and gentamicin (n = 292) were consecutively collected during a two-year period (2015-2016) in five tertiary care hospitals in Athens. RMT genes were detected by PCR. In all RMT-producing isolates, ESBL and carbapenemase production was confirmed by PCR, and the clonal relatedness and the plasmid contents were also characterized. None of the 138 P. aeruginosa isolates harbored any of the RMT genes surveyed although some were highly resistant to aminoglycosides (MICs > = 512 mg/L). Among 154 Enterobacterales, 31 Providencia stuartii (93.9%), 42 Klebsiella pneumoniae (37.8%), six Proteus mirabilis (75%), and two Escherichia coli (100%) isolates were confirmed as highly resistant to amikacin, gentamicin, and tobramycin with MICs ≥ 512 mg/L, harboring mainly the rmtB (98.8%). All were carbapenemase producers. P. stuartii, P. mirabilis, and E. coli produced VIM-type carbapenemases. K. pneumoniae produced KPC- (n = 34, 81.0%), OXA-48 (n = 4, 9.5%), KPC- and VIM- (n = 3, 7.1%), or only VIM-type (n = 1, 2.4%) enzymes. Two groups of similar IncC plasmids were detected one harboring rmtB1, blaVEB-1, blaOXA-10, and blaTEM-1, and the other additionally blaVIM-1 and blaSHV-5. Among RMT-producing Enterobacterales, rmtB1 predominated and was associated with carbapenemase-encoding gene(s). Similar IncC plasmids carrying a multiresistant region, including ESBL genes, and in the case of VIM-producing isolates, the blaVIM-1, were responsible for this dissemination. The co-dissemination of these genes poses a public health threat.

In vitro activity of ceftolozane/tazobactam alone and in combination with amikacin against MDR/XDR Pseudomonas aeruginosa isolates from Greece.

OBJECTIVES: We evaluated the in vitro activity of ceftolozane/tazobactam and comparator agents against MDR non-MBL Pseudomonas aeruginosa isolates collected from nine Greek hospitals and we assessed the potential synergistic interaction between ceftolozane/tazobactam and amikacin. METHODS: A total of 160 non-MBL P. aeruginosa isolates collected in 2016 were tested for susceptibility to ceftolozane/tazobactam and seven comparator agents including ceftazidime/avibactam. Time-kill assays were performed for synergy testing using ceftolozane/tazobactam 60 or 7.5 mg/L, corresponding to the peak and trough concentrations of a 1.5 g q8h dose, respectively, in combination with 69 mg/L amikacin, corresponding to the free peak plasma concentration. Synergy was defined as a ≥2 log10 cfu/mL reduction compared with the most active agent. RESULTS: Overall, ceftolozane/tazobactam inhibited 64.4% of the P. aeruginosa strains at ≤4 mg/L. Colistin was the most active agent (MIC50/90, 0.5/2 mg/L; 96.3% susceptible) followed by ceftazidime/avibactam (MIC50/90, 4/16 mg/L; 80.6% susceptible). GES-type enzymes were predominantly responsible for ceftolozane/tazobactam resistance; 81.6% of the non-producers were susceptible. MICs for the P. aeruginosa isolates selected for synergy testing were 2-32 mg/L ceftolozane/tazobactam and 2-128 mg/L amikacin. The combination of ceftolozane/tazobactam with amikacin was synergistic against 85.0% of all the isolates tested and against 75.0% of the GES producers. No antagonistic interactions were observed. CONCLUSIONS: Ceftolozane/tazobactam demonstrated good in vitro activity against MDR/XDR P. aeruginosa clinical isolates, including strains with co-resistance to other antipseudomonal drugs. In combination with amikacin, a synergistic interaction at 24 h was observed against 85.0% of P. aeruginosa strains tested, including isolates with ceftolozane/tazobactam MICs of 32 mg/L or GES producers.

Dissemination of International Clone II Acinetobacter baumannii Strains Coproducing OXA-23 Carbapenemase and 16S rRNA Methylase ArmA in Athens, Greece.

The aim of this study was to study the molecular epidemiology of 16S rRNA-methylase (RMT)-producing clinical Acinetobacter baumannii isolates from hospitals in Athens, Greece. Single-patient A. baumannii clinical isolates, coresistant to amikacin and gentamicin (n = 347), from five tertiary care hospitals, were submitted to minimum inhibitory concentration determination and molecular testing for carbapenemase and RMT genes. A. baumannii, resistant to amikacin and gentamicin, was isolated at participating institutions at a mean rate of 67.8%. Among them 93.7% harbored the armA. The vast majority (98.5%) of armA positive isolates were OXA-23 producers, assigned mainly (99.4%) to sequence group G1, corresponding to international clone (IC) II. Four isolates (all from the same hospital) were OXA-24 producers (1.2%), assigned to G6 corresponding to CC78 and only one isolate was OXA-58-producer, assigned to G2 (IC I). Apramycin was the most active agent inhibiting 99.7% of the isolates at ≤64 mg/L, whereas colistin, trimethoprim/sulfamethoxazole, minocycline, and tigecycline exhibited only sparse activity (S, <18%). RMT production is an emerging mechanism of resistance, capable of compromising the clinical efficacy of aminoglycosides. High prevalence of armA was observed among A. baumannii strains isolated in participating hospitals in Athens, which were mainly OXA-23 producers and belonged to IC II. Apramycin is a structurally unique aminoglycoside, currently used as a veterinary agent. Although it has not been evaluated for clinical use, apramycin appears worthy of further investigation for repurposing as a human therapeutic against difficult-to-treat pathogens.

An improved flow cytometric assay for detection and discrimination between malignant cells and atypical mesothelial cells, in serous cavity effusions.

BACKGROUND: The aim of this study was to evaluate a flow cytometric assay for the detection of malignant effusions. METHODS: During the last 4-year period, 125 effusions suspicious for malignancy were prospectively analyzed by flow cytometry and conventional cytology. A three-step flow cytometric assay was performed, beginning with an initial informative panel of two protocols, containing SYTO-16, 7-AAD, CD71-PE, CD45-ECD, and CD66abce-FITC, CD64-PE, CD45-ECD, CD16-PECy5, CD14-PECy7, respectively. This was followed by a basic immunophenotypic panel of seven three-color combinations, containing in the first position, EMA, Ber-EP4, CD66abce, CD56, and intracellular desmin-33, combined with CD71-PE and CD45-PeCy5 in each tube. Finally, a cytokeratin-FITC/propidium iodide DNA panel was conducted, for the detection of aneuploidy in cytokeratin positive cells. RESULTS: The sensitivity and specificity of flow cytometry were 85.1 and 97.8%, and of cytology 93.2 and 95.6%, respectively. A significant association was observed between the results of the two techniques (P < 0.001). Among eight atypical cases detected by cytology, five had been precisely characterized as malignant by flow cytometry. EMA and Ber-EP4 proved the most sensitive markers for malignancy diagnosis, while the detection of desmin-33 negative/cytokeratin positive cells had the simultaneous highest positive and negative predictive values. CD66abce was very specific, although nonsensitive, while DNA ploidy analysis was nonspecific, as hyperploidy was observed in reactive mesothelial cells. CONCLUSIONS: A flow cytometric assay of high sensitivity and specificity is proposed for the routine identification of carcinoma cells in effusions and their distinction from atypical mesothelial cells, as an ancillary to conventional cytology.