Nataša Beader

Postantibiotic and Post-Beta-Lactamase Inhibitor Effect of Carbapenems Combined with EDTA against Pseudomonas aeruginosa Strains Producing VIM-Metallo Beta-Lactamases

Background and Aim: Postantibiotic effect (PAE) is a delay of bacterial growth after short exposure to antibiotics. The phenomenon of continuing suppression of bacterial growth after removal of β-lactamase inhibitors is termed post-β-lactamase inhibitor effect (PLIE). Recently, Pseudomonas aeruginosa strains producing metallo-β-lactamases were described in many countries of the world. The aim of the study was to investigate the PLIE of carbapenems in combinations with EDTA against VIM-MBL-positive strains of P. aeruginosa. Methods: The experiments were performed on two Pseudomonas aeruginosa isolates, one producing VIM-1 and the other producing VIM-2 metallo-β-lactamase. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBC) of imipenem and meropenem alone and combined with EDTA, time-kill curves, PAE and PLIE were performed as described previously. Results: The duration of PAE with meropenem combined with EDTA at 8 × MIC was longer against both VIM-1 and VIM-2 producer than that of imipenem with EDTA on VIM-1- and VIM-2-positive strains. The duration of PLIE was similar on both strains of P. aeruginosa regardless of the sort of carbapenem. At lower concentrations, meropenem with EDTA induced slightly longer PAE and PLIE than imipenem with EDTA. Conclusions: This study has shown that EDTA combined with carbapenems produced a significant PLIE on VIM-MBL-positive P. aeruginosa strains. The results do not have any clinical relevance so far since metal chelators such as EDTA are not used as therapeutic agents due to their toxicity.

Nursing Home as a Reservoir of Carbapenem-Resistant Acinetobacter baumannii.

Acinetobacter baumannii is an increasingly common pathogen in healthcare settings globally. It is frequently resistant to multiple antimicrobial agents and there are recent reports on strains that are pandrug resistant. The aim of the study was to characterize the mechanisms of carbapenem resistance of A. baumannii strains from a nursing home in Zagreb and to genotype the strains. Antimicrobial susceptibility testing was performed by the broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). PCR was used to detect genes encoding carbapenemases of groups A, B, and D and extended-spectrum β-lactamases. Genotyping of the strains was performed by rep-PCR. All strains were found to be resistant to ceftazidime, cefotaxime, ceftriaxone, cefepime, piperacillin/tazobactam, imipenem, meropenem, and ciprofloxacin. All, but one strain, were resistant to gentamicin. PCR revealed blaOXA-23 genes in 14, blaOXA-24 in 5, and blaVIM in 11 strains. All strains positive for blaVIM genes coharbored blaOXA-23 genes. The 14 strains with OXA-23 belonged to ICL II, whereas the 5 strains positive for blaOXA-24 belonged to ICL I. In contrast to hospitals where OXA-24/40-like β-lactamases and OXA-58 were the most prevalent, OXA-23-like β-lactamases are the dominant group in the nursing home. OXA-58-like β-lactamase, which is the most widespread group, was not found. Acquisition of blaMBL genes in A. baumannii strains was observed. Rep-PCR identified two clones. Two strains A10 and A13 were alocated to a novel sequence type ST 637. Nursing homes can act as a source of dissemination of blaOXA and blaMBL genes in the environment and the possible influx to the hospital environment.

Nursing home as reservoir of carbapenem-resistant Acinetobacter baumannii

Acinetobacter baumannii is an increasingly common pathogen in healthcare settings globally. It is frequently resistant to multiple antimicrobial agents and there are recent reports on strains that are pandrug resistant. The aim of the study was to characterize the mechanisms of carbapenem resistance of A. baumannii strains from a nursing home in Zagreb and to genotype the strains. Antimicrobial susceptibility testing was performed by the broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). PCR was used to detect genes encoding carbapenemases of groups A, B, and D and extended-spectrum β-lactamases. Genotyping of the strains was performed by rep-PCR. All strains were found to be resistant to ceftazidime, cefotaxime, ceftriaxone, cefepime, piperacillin/tazobactam, imipenem, meropenem, and ciprofloxacin. All, but one strain, were resistant to gentamicin. PCR revealed blaOXA-23 genes in 14, blaOXA-24 in 5, and blaVIM in 11 strains. All strains positive for blaVIM genes coharbored blaOXA-23 genes. The 14 strains with OXA-23 belonged to ICL II, whereas the 5 strains positive for blaOXA-24 belonged to ICL I. In contrast to hospitals where OXA-24/40-like β-lactamases and OXA-58 were the most prevalent, OXA-23-like β-lactamases are the dominant group in the nursing home. OXA-58-like β-lactamase, which is the most widespread group, was not found. Acquisition of blaMBL genes in A. baumannii strains was observed. Rep-PCR identified two clones. Two strains A10 and A13 were alocated to a novel sequence type ST 637. Nursing homes can act as a source of dissemination of blaOXA and blaMBL genes in the environment and the possible influx to the hospital environment.

Postantibiotic effect of colistin alone and combined with vancomycin or meropenem against Acinetobacter spp. with well defined resistance mechanisms

Previous studies found short postantibiotic effect of colistin on Acinetobacter baumannii. Many studies have evaluated the potential for synergy between colistin and other antibiotics against A. baumannii. The aim of this study was to determine in vitro synergy and postantibiotic effect (PAE) of colistin alone and combined with other antibiotics (vancomycin or meropenem) against eight carbapenem-non-susceptible Acinetobacter spp. strains with defined resistance mechanisms. It was hypothesised that vancomycin or meropenem would prologue the PAE of colistin since it was previously found that they exert synergism with colistin in time-kill kinetics and chequerboard analysis. After exposure of 1 hour colistin alone exhibited the negative ( − 0.07 hour) (OXA-143), short (0.2–1.82 hours) (OXA-24, OXA-58, OXA-72, VIM-1+OXA-23, OXA-58+NDM-1, ISAba1/OXA-69) or moderate PAE (3.2 hours) for OXA-23 positive strain. When combined with vancomycin, the PAE was moderate (1.7–4 hours) with OXA-23, OXA-23+VIM-1, OXA-72 and OXA-24 positive strains while with OXA-58, OXA-143, OXA-58/NDM-1 and ISAba1/OXA-69 positive strains, it was not possible to calculate mean duration of PAE because there was no regrowth after exposure to antibiotics or it was longer than 5 hours. The combination with meropenem resulted in short (0.2 hours) (OXA-143), moderate (2.4–3.73 hours) (OXA-24, OXA-58, OXA-23, OXA-23+VIM-1), long PAE of 5 hours (OXA-23) or longer than 5 hours (OXA-58+VIM-1, ISAba1/OXA-69). From the clinical point of view, the prolongation of colistin PAE when combined with other antibiotics could provide a rationale for the modification of the dosing interval and could be important for the optimization of the treatment regimen and the minimization of drug-induced side effects.

NDM-1-producing Enterobacter aerogenes isolated from a patient with a JJ ureteric stent in situ

Urinary tract infections after JJ stent insertion are among the most common complications, and the associated microorganisms carry more antibiotic resistance determinants than those found in urine prior to stent insertion. In line with the trends in healthcare epidemiology which implicate multi-resistant microorganisms in a plethora of healthcare-associated infections, prosthetic stent material also represents an ideal milieu for biofilm formation and subsequent infection development with resistant bacterial agents. Here we describe a case of a 73-year-old Caucasian woman presenting with urinary tract infection after JJ ureteric stent insertion due to ureteric obstruction and hydronephrosis of her left kidney. Extensive microbiological work-up and comprehensive molecular analysis identified the putative microorganism as carbapenem-resistant Enterobacter aerogenes carrying New Delhi metallo-beta-lactamase 1 (NDM-1). This is a first literature report implicating such extensively resistant strain of this species in early indwelling ureteric stent complications, and also the first report of NDM-1 in Enterobacter aerogenes in Croatia and Europe.

Anaerobic Bacteria in Implants and Homologous Teeth 2-14 Years after Implantation

Objective The objective of the study was to establish whether there is a difference in the presence of potentially pathogenic anaerobic microorganisms around the implant and the homologous tooth in implant-prosthetic patients who received individual information about maintaining their oral hygiene. Material and methods The study included 30 subjects with dental implants and metal-ceramic crowns. A periodontal probe was used to record the approximal plaque index (API), the papilla bleeding index (PBI), the periodontal pocket probing depth (PD) and the gingival recession. The fluid around the implant and the gingival sulcus fluid around the homologous tooth on the opposite lateral side were sampled. Results The results have shown a positive API and PBI on 30% of the implants and a negative one on 70% of the implants. The average mucosal retraction measured around the implants was 0.15 mm, and the average probing depth was 2.25 mm. The API and PBI were positive on 78.3% of the homologous teeth. The average gingival retraction measured was 1.06 mm, and the average probing depth was 1.85 mm. Anaerobic bacteria were found in 12 out of 30 subjects (40%). Anaerobic bacteria were isolated only on the implant in 7 subjects, only on the homologous tooth in 3 subjects and both on the implant and the homologous tooth in 2 subjects. Conclusions Anaerobic bacteria were more abundantly present on implants than on homologous teeth.

Herpes Group Viruses: a Seroprevalence Study in Hemodialysis Patients

Herpes group viruses (herpes simplex virus, HSV; varicella-zoster virus, VZV; cytomegalovirus, CMV; and Epstein-Barr virus, EBV) remain an important cause of morbidity in immunocompromised persons. The aim of the study was to analyze the prevalence of HSV-1, HSV-2, VZV, CMV and EBV in patients undergoing hemodialysis. During a three-year period (2013-2015), 152 consecutive serum samples from hemodialysis patients and 150 healthy subjects (control group) were tested for the presence of IgM/IgG antibodies to herpes group viruses. Serologic tests were performed using a commercial enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunofluorescent assay (ELFA). Hemodialysis patients showed significantly higher CMV IgG seropositivity compared to controls (88.2% vs. 78.7%, p=0.011). In addition, seroprevalence rates of HSV-1 and VZV were higher in hemodialysis patients; however, these differences did not reach statistical significance (85.5% vs. 80.0%, p=0.054 and 99.3% vs. 96.0%, p=0.051, respectively). The prevalence of HSV-2 and EBV was similar in both groups (12.5% vs. 12.7%, p=0.137 and 98.0% vs. 95.3%, p=0.113, respectively). There was no difference in IgG seropositivity according to gender and place of residence. Logistic regression showed that older age was a significant predictor for CMV and EBV IgG seropositivity (increase in age by one year: CMV OR=1.055; 95%CI=1.030-1.080 and EBV OR=1.075, 95%CI=1.023-1.130).

Abdominal Wall Defect Reconstructed by Breast Flaps Using a Mercedes Closure Pattern.

AbstractBackgroundSurgery of the abdominal cavity may lead to postoperative defects to the ventricular segment of the abdominal wall. The reconstruction of these defects, especially in the area of the median line, represents an issue during the course of healing due to the role of the abdominal cavity in respiratory processes.MethodsReconstructive surgical procedure was performed on an infected vast defect to the ventral segment of the abdominal wall in a 77-year-old woman by a modified “Mercedes closure pattern,” i.e., by combining three fasciocutaneous flaps: bipedicle flap of the upper segment of the abdominal wall and two sliding breast flaps.ResultsApplication of a modified complex Mercedes closure pattern was successful and positively affected the redistribution of pressure forces at the places where the edges of the wound were in contact.ConclusionsThe applied and described technique of closing the abdominal cavity decreased the possibility of infection to the prosthetic material, because direct contact between the sutures and the prosthetic no longer existed.Level of Evidence IVThis journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.