Gram-negative bacteria as causative agents of ventilator-associated pneumonia and their respective resistance mechanisms.

Ventilator-associated pneumonia (VAP) is a serious and common complication in patients admitted to intensive care unit (ICU) and contributes to mortality. Multidrug Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae are frequently associated with VAP in ICU. A prospective study was set up in three ICUs of the University Hospital Center Zagreb and one ICU in General Hospital Pula from September 2017 to March 2018. Antibiotic susceptibility was determined by broth microdilution method. Production of extended-spectrum ß-lactamases (ESBLs) was determined by double-disk synergy test and carbapenemases by Hodge and carbapenem inactivation method (CIM). The genes encoding ESBLs, carbapenemases of class A, B and D and qnr genes were determined by PCR. In total 97 Gram-negative bacteria isolates were analyzed. P. aeruginosa demonstrated high resistance rates for imipenem and meropenem with 74% and 68% of resistant strains, respectively. Moderate resistance rates were observed for ceftazidime andpiperacillin/tazobactam, ciprofloxacin and gentamicin (44%). All except three A. baumannii isolates, were resistant to carbapenems and to all other antibiotics apart from colistin and amikacin. Eight A. baumannii isolates were positive for blaOXA-23 and 12 for blaOXA-24 genes. Four K. pneumoniae and two E. cloacae strains were ESBL positive and harboured group 1 of CTX-M ß-lactamases. Three P. mirabilis strains were positive for plasmid-mediated ampC ß-lactamase of CMY family. Two carbapenem-resistant K. pneumoniae harboured OXA-48 and one carbapenem-resistant E. cloacae VIM-1. A high proportion of multidrug-resistant P. aeruginosa, K. pneumoniae and extensively resistant A. baumannii was reported. Acquired resistance mechanisms, mainly production of carbapenemases and ESBLs were dominant in A. baumannii and K. pneumoniae, respectively. Resistance of P. aeruginosa isolates was more likely due to upregulation of efflux pumps or porin loss. A marked diversity of ß-lactamases was identified in Enterobacteriaceae.

In vitro synergy and postantibiotic effect of colistin combinations with meropenem and vancomycin against Enterobacteriaceae with multiple carbapenem resistance mechanisms.

AIM: The aim of the study was to determine in vitro synergy and postantibiotic effect of colistin alone and combined with meropenem or vancomycin against Enterobacteriaceae producing multiple carbapenemases; combinations of two metallo-ß-lactamases (MBL) or MBL with OXA-48. Colistin-resistant strain positive for OXA-48 was also included in the study. METHODS: The antibiotic susceptibility was tested by broth microdilution method. Synergy was tested by chequerboard, time-kill and 2-well method. PAE was determined by viable counting. RESULTS: The chequerboard analysis revealed synergy for colistin combination with meropenem in all isolates with FICI values ranging from 0.12 to 0.24. FICI values for combinations with vancomycin were below 0.5 indicating synergy in two out of four isolates. K. pneumoniae 609815 positive for OXA-48 and colistin resistant showed the most pronounced and consistent synergy effect with meropenem in both chequerboard and time-kill method. Synergy effect in time-kill curves, was observed for K pneumoniae 145846 with two MBLs and colistin resistant K. pneumoniae 609815 positive for OXA-48, with both combinations including meropenem and vancomycin. Colistin alone exhibited short postantibiotic effect (PAE) against all tested isolates. Meropenem markedly prolonged the PAE in two isolates in contrast to vancomycin which did not demonstrate significant effect on the duration of PAE. CONCLUSIONS: The synergy effect and the duration of PAE was strain and antibiotic dependent but not related to the resistance gene content.

Seroepidemiological Study of Epstein-Barr Virus in Different Population Groups in Croatia.

BACKGROUND: The Epstein-Barr virus (EBV) is one of the most common viruses found in humans, causing lifelong infection in up to 95% of the world population. OBJECTIVES: To analyze the seroprevalence of EBV infection in different population groups in Croatia. METHODS: During a 2 year period (2015-2016), a total of 2022 consecutive serum samples collected from Croatian residents were tested for the presence of EBV-specific viral capsid antigen (VCA) immunoglobulin M (IgM) and IgG antibodies using an enzyme-linked immunoassay. IgM/IgG-positive samples were further tested for IgG avidity. RESULTS: The overall prevalence of EBV IgG antibodies was 91.4%. Females had significantly higher IgG seroprevalence than males (93.1% vs. 89.9%, P = 0.008). According to age, IgG seropositivity increased progressively from 59.6% in children age < 9 years to 98.3% in 30-39 year olds, and remained stable thereafter (P < 0.001). The IgG seroprevalence differed significantly among groups: 68.1% in children/adolescents and 95.9% in adults; multiple sclerosis (100%), hemodialysis patients (97.7%), heart transplant recipients (93.8%), hematological malignancies (91.2%), and Crohn's disease (88.5%), P < 0.001. IgM antibodies were detected in 9% of participants. Using IgG avidity, recent primary EBV infection was documented in 83.8% of IgM-positive subjects < 9 years old, 69.2% age 10-19, 33.3% age 20-29, and 3.6-4.2% > 40. All IgM positive participants > 40 years showed high IgG avidity. Logistic regression showed that age is associated with EBV IgG seropositivity. CONCLUSIONS: EBV is widespread in the Croatian population. Older age appears to be the main risk factor for EBV seropositivity.