OAR@UM Community:

Prevalence of legionella pneumophila from water sources in the Maltese Islands

2025-12-24T09:20:49Z

Title: Prevalence of legionella pneumophila from water sources in the Maltese Islands Abstract: This project has dealt with the prevalence of Legionella pneumophila and other indicator organisms from water sources used in educational, industrial, health institution and recreational environment in Malta and Gozo. A previous study related to the detection of Legionella species in Health Institutional facilities had been performed in 2005 but it did not include the current General Acute Teaching Hospital (GATH) included in this study which accepted patients in late 2007. Another study involving testing of water samples for Legionella was carried out in 2013 and it involved testing of 27 samples from the Maltese Islands which included five water samples from water fountains (Blundell, 2014) . Other studies on Legionella recorded did not involve laboratory-based tests. According to the Annual Epidemiological Report published by the European Centre for Disease Prevention and Control (ECDC) for 2019, there were 5 cases of Legionnaires’ disease recorded in Malta but none resulting in death (ECDC, 2021) [...] Description: M.Phil.(Melit.)

Evaluating the effect of plasma activated water on keratinocytes

2025-02-25T09:25:44Z

Title: Evaluating the effect of plasma activated water on keratinocytes Abstract: Rising antimicrobial resistance has highlighted the need for alternative and novel disinfection technologies. Cold atmospheric plasma and its application to solutions such as plasmaactivated water (PAW) fulfil the requirement of a novel technique with antimicrobial characteristics. The suitability of such a product for use as a hand sanitiser would require a balance between antimicrobial efficacy and safety for dermal application. To this end, immortalised keratinocyte cell lines N/TERT1 and N/TERT2G were exposed to PAW for 5 minutes, and cytotoxic markers were evaluated. Specifically, post-exposure cellular viability was assessed using a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay, and the secretion of immune-response-related cytokines IL-1α, IL4, IL-6, and IL-8 was measured using ELISA. Membrane integrity was evaluated for lipid peroxidation via a TBARS assay, and potential mitochondrial dysregulation was assessed using JC-1 fluorescence. Cleaved caspase-3 was assessed as an apoptotic marker, and potential oxidative stress was evaluated by measuring Glutathione (GSH) concentrations and Superoxide Dismutase (SOD) activity. Exposure to PAW decreased viability similarly to water, to 90% in N/TERT1 and 80% in N/TERT2G; however, this was not statistically significant. No apoptotic induction or cellular dysregulation was indicated as a result of PAW exposure. The GSH concentration increased fivefold upon challenge with PAW in N/TERT2G (p < 0.05), but no such effect was observed in N/TERT1 keratinocytes. The SOD activity remained unaffected following exposure to PAW in both cell lines, indicating that the GSH pathway is sufficient to mitigate oxidative stress. No lipid peroxidation occurred in either N/TERT1 or N/TERT2G keratinocytes following exposure to PAW. Similarly, the mitochondrial membrane potential was also comparable to that of the untreated control cells. Together, these findings demonstrate that transient application of PAW is safe for dermal use. Slight variations in the responses from both cell lines highlight the potential biological variation that can be found in a non-clonal population, emphasising the need for further studies to account for such variation. Moreover, testing must also be carried out on in vitro models to further ensure the safe use of PAW as a topical disinfectant. Description: M.Sc.(Melit.)

Microbiological analysis of Maltese dry sausages : isolation of lactic acid bacteria and assessment of their survival to low pH, as a basic in vitro probiotic attribute

2024-11-14T12:38:15Z

Title: Microbiological analysis of Maltese dry sausages : isolation of lactic acid bacteria and assessment of their survival to low pH, as a basic in vitro probiotic attribute Abstract: Background: Fermented dry sausages are traditional food products, commonly consumed in the Mediterranean region. These products rely on natural fermentation processes driven by indigenous microbiota and have unique attributes influenced by local microbiota, ingredients, and processing methods. Traditional Maltese dry sausages have yet to be comprehensively studied for their microbial composition and probiotic potential. This dissertation aims to explore the microbial population dynamics of Maltese dry sausages and evaluate the acid tolerance of lactic acid bacteria (LAB) strains isolated from these products to assess their probiotic potential. Methodology: Five samples of traditional Maltese dry sausages, with no added starter cultures were collected, from different local butchers. Microbiological analysis was conducted to enumerate various bacterial groups, including Escherichia coli, Enterobacteriaceae, Total mesophilic count, Salmonella, Yeasts, and moulds, lactococci, and LAB. LAB strains were isolated using de Man, Rogosa, and Sharpe agar (MRS). Their resistance to low pH (pH 2.5) was tested to assess their acid tolerance. Resistance was assessed through viable colony counts at 0, 0.5, 1, 2, and 3 hours. Statistical analysis used the test of analysis of variance (ANOVA) to identify significant differences in survival rates (p < 0.05). Results: Microbial analysis revealed variations in microbial populations across different sausage samples, with LAB strains dominating on MRS and M17 media. This indicates the potential responsibility of LAB for fermentation processes. The acid tolerance test on isolates obtained from MRS showed a marked decrease in survival rates over a 3-hour incubation period, with none of the strains having a final population exceeding 103 CFU/mL at the 3-hour time point. This finding suggests potential limitations in the probiotic potential of the specific LAB isolates, since microorganisms classified as probiotics typically demonstrate robust acid tolerance. Conclusion: The study sheds light on the microbial composition of traditional Maltese dry sausages and underscores the importance of further research to elucidate the probiotic potential of LAB strains in these food products. Future research should address limitations such as small sample sizes and resource constraints, while also conducting comprehensive probiotic assessments to better understand the health benefits associated with LAB strains in traditional Maltese cuisine. Description: B.Sc. (Hons)(Melit.)

Microbiological analysis of traditional Maltese cheeselets : isolation of lactic acid bacteria and assessment of their survival to low pH, as a basic in vitro probiotic attribute

2024-11-14T12:36:53Z

Title: Microbiological analysis of traditional Maltese cheeselets : isolation of lactic acid bacteria and assessment of their survival to low pH, as a basic in vitro probiotic attribute Abstract: Background: Maltese traditional fermented foods such as the cheeselets have not been extensively evaluated in terms of their microbial composition and probiotic attributes. This study aimed to provide a preliminary insight into the microbial characteristics of the cheeselets whilst investigating the resistance of selected lactic acid bacteria (LAB) isolated from these products, to low pH conditions, which is a key probiotic trait. Method: Cheeselet samples were collected, homogenised, and plated on various media, including those specific for LAB isolation. The pH measurements of the cheeselets were also recorded. The resistance of the LAB isolates to low pH (pH 2.5 at 37°C) was assessed, and the data was analysed. Results: Regarding the microbial analysis, varying levels of bacterial populations were observed, with the main populations being LAB, likely belonging to the genera of Lactobacillus and Lactococci. Salmonella spp. was not detected whilst E. coli was present in one sample. Upon exposure to low pH, a decrease in population was observed in all 18 isolates, which was determined to be statistically significant via a repeated measures ANOVA test with an observed p-value of <0.001 and an F-statistic of 2.534. Five isolates were attributed with moderate tolerance to low pH with a population count exceeding 3 log CFU/mL following three hours of exposure, whilst one isolate (GB8), was considered to have good tolerance as it remained above 6 log CFU/mL throughout exposure. GB8 had the highest survival rate (67%) and the lowest log reduction (3.08 Log CFU/mL) amongst all isolates. Conclusion: This study provides a preliminary insight into the microbial characteristics of artisanal produced traditional Maltese cheeselets. Furthermore, the tolerance of LAB isolates to low pH conditions was successfully examined with several isolates exhibiting moderate to good tolerance. Further research is necessary to expand upon these conclusions and obtain a more comprehensive understanding of the probiotic attributes inherent to Maltese cheeselets. Description: B.Sc. (Hons)(Melit.)