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PHENOTYPIC PROFILE OF VIRULENCE FACTORS IN MULTIRESISTANT BACTERIAL STRAINS ISOLATED FROM HOSPITALIZED PATIENTS

Daniela-Cristina Mihai

Abstract

Nosocomial infections have an important place in human pathology, becoming a major public health problem due to the high frequency of multiresistant strains, with afferent consequences. In the Intensive Care Units (ICU), nosocomial infections represent a constant risk due to a cumulus of factors that increase susceptibility to infections, respectively: decreased immunity due to underlying pathology, patient exposure to a series of invasive manoeuvres, poor nutritional status etc. The purpose of this study was to establish the virulence profiles of nosocomial bacterial strains isolated from localized and systemic infections in immunocompromised patients. In our study, we investigated a total of 108 samples (throat swabs, wound secretions, tracheal secretions, urine and blood), collected from patients hospitalized in 2017, both in the ICU and in other clinical departments of the Emergency Institute of Cardiovascular Diseases "Prof. CC. Iliescu". After isolation on selective culture media, the bacterial strains were identified using the VITEK II system and the antibiotic susceptibility spectrum were established according to CLSI 2017/EUCAST 2017 recommendations. The production of extracellular hydrolytic enzymes was determined by using specific growth media. The results were recorded semi-quantitatively and expressed as the ratio of the colony diameter to the diameter of the colony plus the precipitation/haemolysis zone. The bacterial invasiveness ability and adherence to HeLa cells were assessed by Cravioto?s adapted qualitative and quantitative methods. Adherence indexes and patterns were established by microscopic evaluation. The invasive capacity was evaluated using a quantitative assay of the colony forming units- CFU/ml. Our results indicate that the most common etiological agents of nosocomial infections are multiple drug-resistant (MDR) opportunistic bacteria identified as Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumanii. The MDR+ and MDR- strains were identified by conventional biochemical assays and analysed for their ability to produce soluble virulence factors (enzymes) and cell associated that are involved in bacterial cell adhesion. Our research revealed that source of isolation of the total 108 analysed strains expressed an aggregative diffusion pattern. Also, the mean values of adhesion and invasion in the MDR group were significantly higher than those observed in the non-MDR group.

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DOI resolver: doi.org/10.5593/sgem2018/6.2/s25.055

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