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Objectives: With the rise in antimicrobial resistance, there is a growing demand for rapid antimicrobial susceptibility testing (RAST). In this study, we applied the EUCAST RAST method to ESBL/carbapenemase-producing Escherichia coli and Klebsiella pneumoniae isolates without using advanced identification systems and analysed the effect of this method on mortality rates Also the clinical impact of this method on patients infected with these bacteria and its effect on mortality rates were investigated., Methods: RAST was used for clinical blood cultures containing carbapenemase/ESBL-producing E. coli and K. pneumoniae without advanced identification systems (e.g. MALDI TOF), with preliminary identification by simple diagnostic tests (predicted RAST, or p-RAST), and its categorical agreement was investigated. The impact of the method on mortality was analysed by comparing the clinical data of patients whose blood cultures were subject to p-RAST (p-RAST group, n = 49) and those who were not subject to p-RAST (non-RAST group, n = 145)., Results: p-RAST results were analysed based on 539 antibiotic-bacteria combinations. Total error rates at 4, 6 and 8 h of incubation were 2.9%, 3.9% and 3.8%, respectively. In the p-RAST group, patients who did not receive appropriate antibiotics (29/45, 59.1%) were switched to appropriate treatment within 8 h at the latest. In contrast, in the non-RAST group, treatment of patients who received inappropriate antibiotics (79/145, 54.5%) could be changed after at least 24 h. Mortality rates were lower in the p-RAST group than in the non-RAST group (28.6% versus 51.7%, P = 0.005)., Conclusions: p-RAST can be used safely in hospital laboratories with high rates of antimicrobial resistance and can reduce mortality rates by shortening the transition time to appropriate treatment., (© The Author(s) 2024. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the serious forms of health care-associated infection. Pan-drug resistant (PDR) CRKP infections can cause severe infections. Mortality and treatment costs in the pediatric intensive care unit (PICU) are high. This study aims to share our experience regarding the treatment of oxacillinase (OXA)-48-positive PDR-CRKP infection in our 20-bed tertiary PICU with isolated rooms and 1 nurse for every 2-3 patients. Methods: Patient demographic characteristics, underlying diseases, previous infections, source of infection PDR-CRKP, treatment modalities, measures used, and outcomes were recorded. Findings: Eleven patients (eight men and three women) were found to have PDR OXA-48-positive CRKP. Because of the simultaneous detection of PDR-CRKP in three patients and the rapid spread of the disease, it was classified as a clinical outbreak, and strict infection control measures were taken. Combination therapy with double carbapenemase (meropenem and imipenem), amikacin, colistin, and tigecycline was used for treatment. The mean duration of treatment and isolation was 15.7 and 65.4 days, respectively. No treatment-related complication was observed, only one patient died, and the mortality rate was 9%. Conclusions: This severe clinical outbreak can be successfully treated with effective treatment with combined antibiotics and strict adherence to infection control measures. ClinicalTrial.gov ID: 28/01/2022 - 1/5.

Coagulase-negative staphylococci (CNS) are one of the primer agents of blood stream infections (BSI) and catheter-related bloodstream infections (CR-BSI) which are associated mostly with the usage of central venous catheters and, important causes of morbidity and mortality despite the usage of antibacterial and supportive treatment. It is important to determine the properties of these causative microorganisms in order to make appropriate treatment of such infections. The aims of our study were to evaluate the biofilm formation of coagulase negative staphylococci (CNS) which were causative agents of bloodstream (BSI) and catheter related bloodstream infections (CR-BSI), to determine the minimum inhibitory concentration (MIC) of planktonic forms and minimal biofilm eradication concentration (MBEC) of sessile forms for vancomycin and daptomycin and to evaluate the efficacy of these antibiotics in infections with biofilm-forming isolates in vitro. A total of 65 CoNS (n= 26 catheter colonizers, n= 28 CR-BSI, n= 11 BSI agents) were identified by conventional methods and also with BD Phoenix (Becton Dickinson, USA) and Bruker Microflex MS (Bruker Daltonics, Germany) systems. Methicillin resistance was determined by the presence of mecA gene with PCR. MIC values of vancomycin and daptomycin were investigated by broth microdilution, for daptomycin medium containing 25 and 50 μg/ml Ca++ were used. Assessment of biofilm formation and detection of MBEC were determined by microplate method. The clonal relationship was investigated by the PFGE method. A total of 65 isolates; 26 catheter colonizers, 28 CR-BSI agents and 11 BSI agents were evaluated and identified as Staphylococcus epidermidis (n= 33), Staphylococcus haemolyticus (n= 16), Staphylococcus hominis (n= 15), and Staphylococcus capitis (n= 1). 81.5% of the isolates were found to be methicillin resistant and all of them were found to be sensitive to vancomycin (MIC= 0.125-4 μg/ml) and daptomycin (MIC= 0.062-0.25 μg/ml in 25 μg/ml Ca++ and MIC= 0.031-0.50 μg/ml in 50 μg/ml Ca++ containing medium). MIC values were lower in medium containing 50 μg/ml Ca++ for daptomycin. As it is known that the efficacy of daptomycin depends on the physiological levels of Ca++, which causes conformational changes in the structure of these antibacterials. Our findings also suggested that high levels of Ca++ are needed to ensure the efficacy of daptomycin. All of the isolates produced biofilm at different strengths of positivity (n= 12/18.5% weak, n= 35/%53.8 moderate, n= 18/%27.7 strong). MBEC and MBEC/MIC values for vancomycin were found to be higher than daptomycin (p< 0.001). Strong biofilm producers had higher MBEC and MBEC/MIC, MBEC50/MIC50 ve MBEC90/MIC90 values (p< 0.05). Especially in infections with biofilm forming isolates, the detection of only MIC values are not always sufficient in the treatment of biofilm-related infections as they reflect the sensitivity of planktonic bacteria. The inconsistency between the MIC and MBEC values and the high rates of MBEC/MIC found in our study supported this prediction.The lower detection of MBEC and MBEC/MIC values of daptomycin compared to the same values of vancomycin suggested that daptomycin might be effective at lower doses than vancomycin in the treatment of biofilm infections.

Acinetobacter baumannii is an important cause of nosocomial infections that particularly increase the mortality and the morbidity at the intensive care units of the hospitals. The aims of this study were to evaluate the resistance genes, antibiotic susceptibility and the clonal relations among Acinetobacter strains isolated from clinical samples and to determine the resistance mechanisms related to these bacteria in our hospital. A total of 201 A.baumannii strains isolated from different clinical samples (35.3% from tracheal aspirate, 27.3% from blood, 18.4% from abscess material, 19% from other samples) of 160 inpatients evaluated at the Ibni Sina Hospital Central Bacteriology Laboratory, Ankara University School of Medicine, Turkey from April 2010 to December 2011, were included in the study. Identification of the isolates and their susceptibility testing against amikacin, ciprofloxacin, tetracycline, sulbactam/ampicillin, trimethoprim/sulfametoxazole (SXT), ceftazidime, gentamicin, imipenem, levofloxacin, meropenem, piperacillin/tazobactam, cefoperazone/sulbactam, cefepime and colistin were performed by the automated systems, namely Vitek 2 (bioMérieux, France) and BD Phoenix (Becton Dickinson, USA). The molecular mechanisms of beta-lactamase resistance and the presence of integrons were analyzed by polymerase chain reaction (PCR). Moreover, since blaPER-1 gene is of high frequency in Turkey, it was also investigated in the isolates. Pulsed-field gel electrophoresis (PFGE) was performed to examine the clonal relations between isolates. Our results indicated that multidrug resistance rate of A.baumannii was 94.5% (190/201), while 94% (189/201) of the isolates were susceptible to colistin thus making it the most potent antimicrobial agent, followed by amikacin and SXT with a susceptibility rate of 32%. Twelve colistin-resistant isolates were further investigated with the E-test method (AB Biodisk, Sweden) and found to be colistin-resistant. While the results were negative for the genes responsible from metallo-beta-lactamase production, positive results were obtained for blaOXA genes at various rates (OXA-51 100%; OXA-23 91.5%; OXA-58 7%; OXA-24 2%). PFGE results revealed four different main clones (29 isolates in genotype A, 23 in genotype B, 18 in genotype C and 7 in genotype D) in the study population. No common epidemic isolate was detected. Class 1 integrons which take part in the transfer of resistance genes were detected in 112 (55.7%) isolates. There was no statistically significant difference between the genotype distributions of class 1 integron positive strains (p> 0.05). The relationship between the presence of integron in multidrug resistant isolates and resistance to tetracyclin, SXT, imipenem, meropenem, cefoperazone/sulbactam and cefepime were found to be statistically significant (p< 0.05). Of the isolates 42 (21%) were positive for blaPER- 1 gene and all were resistant to ceftazidime. This study indicated that blaOXA genes found together with blaOXA-51 genes play an important role in carbapenem resistance of A.baumannii strains. Moreover, multidrug resistance is still an important problem in infections caused by A.baumannii and integrons play a role in the transfer of the resistance genes. In conclusion, multidrug resistant A.baumannii strains were common in our hospital and our epidemiologic data would be helpful for further investigations and in therapeutical approaches.