Implication of acinetobacter spp. in foodborne illnesses

Abstract

The genus Acinetobacter includes a large variety of Gram-negative species that have been widely studied for a long time. They had been isolated from soil, sewage, water, fruits, vegetables, animals and humans (especially mucous areas); however, not all species are considered as pathogenic. Nevertheless, Acinetobacter spp. are known as nosocomial pathogens responsible for causing a high number of infections in immunocompromised individuals or patients in intensive care units. Recently, there has been a hypothesizis whether these microorganisms could also be responsible for foodborne diseases if contaminated food matrices are ingested. In order to test this hypothesizis, a total of 264 isolates of Acinetobacter spp. collected from patients were genotyped by Pulsed-Field Gel Electrophoresis (PFGE), and 115 different profiles were obtained. One isolate from each cluster was selected (n=115) for subsequent assays. Antibiotic susceptibility characterization was further performed, and 68 isolates out of 115 were classified as multi-drug resistant (MDR). An acidic stress resistance assay (pH 2.5), simulating the stomach environment, was performed and demonstrated that most of the isolates were resistant. So, 14 isolates were selected for further exposure to simulated gastrointestinal conditions. Eleven isolates were more sensitive (4 log cycles reduction) to the simulated digestion process. However, for three isolates, a high recovery rate was observed at the end of 4 hours’ assay. Two of the most resistant isolates were further studied in a cell culture assay with CaCo-2 cells: one isolate exhibited a 50% higher invasion rate than the control, even though the adherence rate was not that high (15%), whereas the other isolate exhibited a 0.2% invasion efficiency. According to this study, it can be concluded that Acinetobacter spp. have the ability to withstand gastrointestinal conditions. While further tests are required to confirm this, they could potentially be considered as foodborne pathogens.

Date of Award	8 Jan 2024
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Joana Barbosa (Supervisor) & Paula Teixeira (Co-Supervisor)