Extensively-drug-resistant Klebsiella pneumoniae ST307 outbreak strain from north-eastern Germany does not show increased tolerance to quaternary ammonium compounds and chlorhexidine.

BACKGROUND: An outbreak of extensively-drug-resistant Klebsiella pneumoniae strain ST307 in a cluster of hospitals in north-east Germany gave rise to the assumption that the epidemiological success of the strain could be based on increased tolerance to biocides. METHODS: The tolerance of the outbreak strain was compared with epidemiologically unrelated clinical isolates of K. pneumoniae, and reference strains of Pseudomonas aeruginosa (ATCC 15442) and Escherichia coli K12 (NCTC 10538). Tests were performed in a miniaturized assay based on European Standard EN 1040. The widely used biocides benzalkonium chloride (BAC) and didecyl dimethyl ammonium chloride (DDAC), their commercial formulation Descosept spezial (DS), and the antiseptic agent chlorhexidine digluconate (CHG) were selected as test substances. These biocides are used regularly in the hospitals involved in the outbreak. FINDINGS: All biocides had a bactericidal effect against all tested strains in the quantitative suspension test within 5 min at typically used concentrations and dilutions. The effectiveness of BAC and DDAC alone and in combination, and CHG antisepsis were not impaired under tested conditions. CONCLUSION: The outbreak strain did not show significantly increased tolerance towards biocides regarding the antiseptic. Thus, the epidemiological success of the strain has to be ascribed to other causes, such as inadequate hand hygiene of visitors.

Impact of antibiotic administration on blood culture positivity at the beginning of sepsis: a prospective clinical cohort study.

OBJECTIVES: Sepsis guidelines recommend obtaining blood cultures before starting anti-infective therapy in patients with sepsis. However, little is known of how antibiotic treatment before sampling affects bacterial growth. The aim of this study was to compare the results of blood cultures drawn before and during antibiotic therapy. METHODS: Prospective clinical cohort study of septic patients. Adult intensive care unit patients with two or three blood culture sets at the beginning of sepsis between 2010 and 2017 were included. Patients with blood culture samples obtained before antibiotic therapy were compared with patients with samples taken during antibiotic therapy. Blood culture positivity, defined as presence of a microbiological pathogen, was compared between the groups. Logistic regression was performed to adjust the impact of different factors with respect to blood culture positivity. RESULTS: In total, 559 patients with 1364 blood culture sets at the beginning of sepsis were analysed. Blood culture positivity was 50.6% (78/154) among patients with sepsis who did not receive antibiotics and only 27.7% (112/405) in those who were already receiving antibiotics (p <0.001). Logistic regression revealed antibiotic therapy as an independent factor for less pathogen identification (odds ratio 0.4; 95% CI 0.3-0.6). Gram-positive pathogens (28.3% (111/392) versus 11.9% (116/972); p <0.001) and also Gram-negative pathogens (16.3% (64/392) versus 9.3% (90/972); p <0.001) were more frequent in blood culture sets drawn before antibiotic therapy compared with sets obtained during antibiotic therapy. CONCLUSIONS: Obtaining blood cultures during antibiotic therapy is associated with a significant loss of pathogen detection. This strongly emphasizes the current recommendation to obtain blood cultures before antibiotic administration in patients with sepsis.

Evaluation of loop-mediated isothermal amplification for the rapid identification of bacteria and resistance determinants in positive blood cultures.

The use of molecular assays to rapidly identify pathogens and resistance genes directly from positive blood cultures (BCs) contribute to shortening the time required for the diagnosis of bloodstream infections. In this work, loop-mediated isothermal amplification (LAMP) assays have been examined for their potential use in BC diagnosis. Three different assays were applied. The commercially available eazyplex® MRSA test detects Staphylococcus aureus, S. epidermidis, mecA, and mecC. Two in-house assays [Gram-positive (GP) and Gram-negative (GN)] have been developed for the detection of streptococci, enterococci, vanA, vanB, Pseudomonas spp., Enterobacteriaceae, and the bla CTX-M family. A total of 370 positive BCs were analyzed. LAMP test results were obtained within 30 min, including sample preparation. Amplification was measured by real-time fluorescence detection. The threshold time for fluorescence intensity values ranged from 6.25 to 13.75 min. The specificity and sensitivity of the assays varied depending on the target. Overall, from 87.7% of BCs, true-positive results were obtained, compared to routine standard diagnosis. Twenty-one tests were true-negative because of the lack of an appropriate target (5.7%). The concordance of positive test results for resistance genes with subsequent antibiotic susceptibility testing was 100%. From 15 BC bottles with mixed cultures, eazyplex® assays produced correct results in 73% of the cases. This study shows that LAMP assays are fast and cost-saving tools for rapid BC testing in order to expedite the diagnostic report and improve the antibiotic stewardship for sepsis patients.