Molecular mechanisms of azole resistance in Candida bloodstream isolates.

BACKGROUND: Antifungal resistance rates are increasing. We investigated the mechanisms of azole resistance of Candida spp. bloodstream isolates obtained from a surveillance study conducted between 2012 and 2015. METHODS: Twenty-six azole non-susceptible Candida spp. clinical isolates were investigated. Antifungal susceptibilities were determined using the Sensititre YeastOne® YO10 panel. The ERG11 gene was amplified and sequenced to identify amino acid polymorphisms, while real-time PCR was utilised to investigate the expression levels of ERG11, CDR1, CDR2 and MDR1. RESULTS: Azole cross-resistance was detected in all except two isolates. Amino acid substitutions (A114S, Y257H, E266D, and V488I) were observed in all four C. albicans tested. Of the 17 C. tropicalis isolates, eight (47%) had ERG11 substitutions, of which concurrent observation of Y132F and S154F was the most common. A novel substitution (I166S) was detected in two of the five C. glabrata isolates. Expression levels of the various genes differed between the species but CDR1 and CDR2 overexpression appeared to be more prominent in C. glabrata. CONCLUSIONS: There was interplay of various different mechanisms, including mechanisms which were not studied here, responsible for azole resistance in Candida spp in our study.

From Bench-Top to Bedside: A Prospective In Vitro Antibiotic Combination Testing (iACT) Service to Guide the Selection of Rationally Optimized Antimicrobial Combinations against Extensively Drug Resistant (XDR) Gram Negative Bacteria (GNB).

INTRODUCTION: Combination therapy is increasingly utilized against extensively-drug resistant (XDR) Gram negative bacteria (GNB). However, choosing a combination can be problematic as effective combinations are often strain-specific. An in vitro antibiotic combination testing (iACT) service, aimed to guide the selection of individualized and rationally optimized combination regimens within 48 hours, was developed. We described the role and feasibility of the iACT service in guiding individualized antibiotic combination selection in patients with XDR-GNB infections. METHODS: A retrospective case review was performed in two Singapore hospitals from April 2009-June 2014. All patients with XDR-GNB and antibiotic regimen guided by iACT for clinical management were included. The feasibility and role of the prospective iACT service was evaluated. The following patient outcomes were described: (i) 30-day in-hospital all-cause and infection-related mortality, (ii) clinical response, and (iii) microbiological eradication in patients with bloodstream infections. RESULTS: From 2009-2014, the iACT service was requested by Infectious Disease physicians for 39 cases (20 P. aeruginosa, 13 A. baumannii and 6 K. pneumoniae). Bloodstream infection was the predominant infection (36%), followed by pneumonia (31%). All iACT recommendations were provided within 48h from request for the service. Prior to iACT-guided therapy, most cases were prescribed combination antibiotics empirically (90%). Changes in the empiric antibiotic regimens were recommended in 21 (54%) cases; in 14 (36%) cases, changes were recommended as the empiric regimens were found to be non-bactericidal in vitro. In 7 (18%) cases, the number of antibiotics used in combination empirically was reduced by the iACT service. Overall, low 30-day infection-related mortality (15%) and high clinical response (82%) were observed. Microbiological eradication was observed in 79% of all bloodstream infections. CONCLUSIONS: The iACT service can be feasibly employed to guide the timely selection of rationally optimized combination regimens, and played a role in reducing indiscreet antibiotic use.

Clinical Efficacy of Polymyxin Monotherapy versus Nonvalidated Polymyxin Combination Therapy versus Validated Polymyxin Combination Therapy in Extensively Drug-Resistant Gram-Negative Bacillus Infections.

Polymyxins have emerged as a last-resort treatment of extensively drug-resistant (XDR) Gram-negative Bacillus (GNB) infections, which present a growing threat. Individualized polymyxin-based antibiotic combinations selected on the basis of the results of in vitro combination testing may be required to optimize therapy. A retrospective cohort study of hospitalized patients receiving polymyxins for XDR GNB infections from 2009 to 2014 was conducted to compare the treatment outcomes between patients receiving polymyxin monotherapy (MT), nonvalidated polymyxin combination therapy (NVCT), and in vitro combination testing-validated polymyxin combination therapy (VCT). The primary and secondary outcomes were infection-related mortality and microbiological eradication, respectively. Adverse drug reactions (ADRs) between treatment groups were assessed. A total of 291 patients (patients receiving MT, n = 58; patients receiving NVCT, n = 203; patients receiving VCT, n = 30) were included. The overall infection-related mortality rate was 23.0% (67 patients). In the multivariable analysis, treatment of XDR GNB infections with MT (adjusted odds ratio [aOR], 8.49; 95% confidence interval [CI], 1.56 to 46.05) and NVCT (aOR, 5.75; 95% CI, 1.25 to 25.73) was associated with an increased risk of infection-related mortality compared to that with treatment with VCT. A higher Acute Physiological and Chronic Health Evaluation II (APACHE II) score (aOR, 1.14; 95% CI 1.07 to 1.21) and a higher Charlson comorbidity index (aOR, 1.28; 95% CI, 1.11 to 1.47) were also independently associated with an increased risk of infection-related mortality. No increase in the incidence of ADRs was observed in the VCT group. The use of an individualized antibiotic combination which was selected on the basis of the results of in vitro combination testing was associated with significantly lower rates of infection-related mortality in patients with XDR GNB infections. Future prospective randomized studies will be required to validate these findings.