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Methicillin-resistant Staphylococcus aureus (MRSA) emerged as one of the most important causes of hospital-acquired bloodstream infections (BSIs), especially the multidrug resistant clones. The aim of the present study was to compare prevalence and resistance patterns of MRSA bacteremia in the major tertiary-care academic and referral center in Serbia before and after implementing an active antimicrobial resistance (AMR) surveillance. Laboratory-based before-after study was conducted during a two-year period (January 2012 to December 2013) in Clinical Centre of Serbia. Isolation and identification of bacterial strains were done following standard microbiological procedures. During the AMR surveillance, nearly twice more bloodstream samples were collected compared to the year without surveillance (1,528 vs. 855). In total, 43 isolates of MRSA were identified. MRSA was significantly more prevalent during the AMR surveillance compared to the previous year [14 (66.7%) to 29 (76.3%); P = 0.046]. During the AMR surveillance, MRSA more frequently originated from medical departments compared to intensive care unit, surgical department, and internal medicine (P = 0.027) indicating increasing MRSA infections in patients with less severe clinical condition and no apparent risk factors. Higher prevalence of MRSA and its lower susceptibility to erythromycin were revealed by implementation of active AMR surveillance, which may reflect more thoughtful collection of bloodstream samples from patients with suspected BSI.

Clostridium (Clostridioides) difficile infections (CDIs) are among the most frequent healthcare-associated infections in Serbia. In 2013, Serbia participated in the European Clostridium difficile Infection Surveillance Network (ECDIS-Net) who launched a pilot study to enhance laboratory capacity and standardize surveillance for CDI. Two clinics of Clinical Center of Serbia [Clinic for Infectious and Tropical Diseases (CITD) and Clinic of Orthopedic Surgery and Traumatology (COT)] from Belgrade and one general hospital from another metropolitan area of Serbia, Užice, participated. During a period of 3 months in 2013, all patients with diagnosed CDI were included. The CDI incidence rates in CITD, COT, and General Hospital Užice were 19.0, 12.2, and 3.9 per 10,000 patient-days, respectively. In total, 49 patients were enrolled in the study with average age of 72 years. A complicated course of CDI was found in 14.3% of all patients. Six (12.2%) of 49 patients died, but not attributable to CDI. Of 39 C. difficile isolates, available for ribotyping, 78.9% belonged to ribotype 027; other PCR ribotypes were 001, 015, 002, 005, 010, 014, and 276. Antimicrobial susceptibility testing revealed low levels of MIC₅₀ and MIC₉₀ for metronidazole (0.5 μg/ml both) and vancomycin (0.25 and 0.5 μg/ml), while 28 strains of ribotype 027 were resistant to moxifloxacin with MIC ≥4 μg/ml. National surveillance is important to obtain more insight in the epidemiology of CDI and to compare the results with other European countries. This study by ECDIS-Net gives bases for a national surveillance of CDI in Serbia.

Abstract

Tigecycline can be effective to treat infections of carbapenem-resistant Acinetobacter baumannii (CRAB) however, no interpretive criteria have been approved so far. The objectives of this study were to evaluate the proportion of CRAB isolates and to compare gradient test with a broth microdilution (BMD) method for tigecycline susceptibility testing of A. baumannii.

This study included 349 multidrug-resistant (MDR) Acinetobacter spp. collected from Serbia, Montenegro, Bosnia and Herzegovina in 2016 and 2017. Antibiotic susceptibility testing was performed by disk diffusion, VITEK2, gradient, ComASP Colistin. Tigecycline susceptibilities were interpreted according to breakpoints of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Food and Drug Administration (FDA).

Majority of the tested isolates were CRAB (92.8%). Tigecycline MIC₅₀/MIC₉₀ values were 4/8 μg/mL by BMD and 0.5/4 μg/mL by gradient test. Essential agreement for BMD and gradient test amounted to 65.1%. With EUCAST breakpoints, categorical agreement (CA) was achieved in 38% isolates. Major discordance (MD-false susceptibility/resistance) and minor discordance (mD-false categorization involving intermediate results) were observed in 10% and 57% A. baumannii, respectively. With FDA breakpoints, CA, MD and mD were observed in 44%, 16% and 47% isolates, respectively. Colistin resistance was 2.1%.

The study highlights a high proportion of CRAB and several discordances between BMD and gradient test which may lead to inappropriate therapy.