OAR@UM Community:

Comparison of microbroth dilution with phoenix automated system and minimum inhibitory concentration (MIC) strips for meropenem sensitivity testing for carbapenem resistant enterobacterales (CRE)

2026-11-12T14:14:32Z

Title: Comparison of microbroth dilution with phoenix automated system and minimum inhibitory concentration (MIC) strips for meropenem sensitivity testing for carbapenem resistant enterobacterales (CRE) Abstract: Antibiotic resistance is a growing concern leading to the emergence of multidrug resistant bacterial strains that are difficult to treat. One such group comprises the carbapenem resistant Enterobacterales (CREs) which are resistant to the carbapenems such as Meropenem. Since Meropenem is used in high doses to treat CRE infections, susceptibility testing of this antibiotic is routinely conducted at Mater Dei Hospital. The broth microdilution (BMD) method is regarded as the gold standard method to carry out such tests, however, other systems more suited for diagnostic laboratories are employed at the hospital, namely BD Phoenix M50TM and minimum inhibitory concentration (MIC) strips. The ability to obtain reliable and accurate results from these systems is yet to be established and was thus the aim of this study. Their efficacy was assessed by performing Meropenem BMD on a total of 221 stored bacterial isolates. The BMD MIC results for these organisms were then compared to retrospective results obtained from the systems employed at Mater Dei Hospital for these same organisms to determine their comparability. Statistical analysis showed high categorical agreement for BD Phoenix M50™ (94.57%) and MIC strips (92.31%) with BMD, with substantial agreement (κ = 0.830 and 0.739; p < 0.001), although essential agreement was low (60.63% and 28.96%) and very major error rates were elevated (15.56% and 31.1%) respectively. In conclusion, despite the presence of notable error rates, sufficient agreement in susceptibility categorisation supports the continued use of these systems in routine diagnostics, with BMD recommended as a confirmatory method in cases of discrepant results rather than as a primary testing method. Description: B.Sc. (Hons)(Melit.)

Assessing the accuracy of MALDITOF ms for identifying microorganisms after short-term incubation in positive blood cultures

2026-11-12T14:12:54Z

Title: Assessing the accuracy of MALDITOF ms for identifying microorganisms after short-term incubation in positive blood cultures Abstract: Bacteraemia refers to the presence of bacteria in the blood. Left untreated, it can progress into sepsis, which can lead to severe organ dysfunction and septic shock if not treated promptly. Therefore, rapid identification of the causative organism is essential to guide antimicrobial treatment. Currently, positive blood cultures are subcultured onto various solid media and incubated for 24 hours before identification by Matrix-Assisted Laser Desorption/Ionisation Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Although accurate, the prolonged incubation delays treatment, which can compromise the patient’s health. This study aimed to evaluate the accuracy of MALDI-TOF MS identification following short-term incubation of subcultures from positive blood cultures and to determine whether it yields results comparable to those obtained after the 24-hour incubation period. Positive blood cultures were subcultured onto Blood agar, Chocolate agar, and MacConkey agar, and incubated for 2, 4, and 5 hours. Identification results obtained were then compared with those obtained from the conventional method using the McNemar test. Exclusion criteria were (i) Yeasts, (ii) only identified with the conventional method, and (iii) no bacteria cultivated. A total of 152 blood cultures with Gram-negatives (n=73) and Gram-positives (n=79) were included in the final analysis. MacConkey agar yielded the highest identification percentage for Gram-negative organisms after 2 hours of incubation (85%), whilst Blood agar was the best for Grampositive organisms after 4 hours of incubation (82.6%). Chocolate agar produced comparable results, and the differences were not clinically significant. Therefore, the results support the hypothesis that MALDI-TOF MS can produce accurate identification after short incubation. Description: B.Sc. (Hons)(Melit.)

The expression of HER-2 in colorectal cancer

2026-11-12T14:11:08Z

Title: The expression of HER-2 in colorectal cancer Abstract: Human Epidermal Growth Factor Receptor 2 (HER-2) is a transmembrane growth factor receptor which has an important role in cell proliferation and survival in several solid organ cancers. Its overexpression in breast and gastric malignancies is well-established. However, its expression in colorectal cancer (CRC) is currently being explored in several studies. CRC ranks as the third most common cancer worldwide and the second most common cause of cancer deaths. Although several therapy regimens associated with molecular biomarkers exist for the management of CRC patients, further therapeutic alternatives are necessary, particularly for those with metastatic disease. Recent studies, suggest the HER-2 is overexpressed in around 2 to 5% of CRC cases. However, a validated immunohistochemistry (IHC) staining method and a standardized scoring system for the expression of HER-2 in CRC has not been yet established. This study aims to assess the expression of HER-2 in locally diagnosed CRC cases. In this study, a retrospective cohort of 151 formalin-fixed, paraffin-embedded (FFPE) CRC samples were analysed by IHC using the HercepTest on PT Link and Link 48 staining platform and SP3 antibody optimised on Dako Omnis autostainer. Tumour membrane staining intensity as well as percentage positivity were assessed and compared by using five different scoring systems. Thirteen equivocal cases were further tested using fluorescence in situ hybridization (FISH) analysis for HER-2 gene amplification. A total of 4 (2.6%) cases were identified as HER-2 positive. This study demonstrated that the SP3 antibody outperformed the HercepTest by producing stronger staining intensity and identifying additional HER-2 positive cases. Out of the 5 scoring systems, the Heracles and IRS-p scoring criteria showed the best agreement. The IRS-p scoring system was essential for identifying one of the positive cases. In conclusion, this study supports the potential clinical value of HER-2 testing in CRC, however further research is required to establish a standardised scoring system to improve the accurate identification of HER-2 positive CRC patients who may benefit from anti-HER-2 targeted therapy. Description: B.Sc. (Hons)(Melit.)

Decoding human monocyte responses to damage-associated molecular patterns (DAMPs)

2026-11-11T14:34:30Z

Title: Decoding human monocyte responses to damage-associated molecular patterns (DAMPs) Abstract: Sepsis is defined as life-threatening organ dysfunction as a result of infection. Numerous studies have attempted to understand the mechanisms underlying this aggressive inflammatory state; however, no specific treatments have yet been approved. Several clinical trials to mitigate overwhelming mortality rates due to sepsis have been unsuccessful. These failures have been ascribed to several gaps in our understanding of sepsis pathophysiology, particularly those pertaining to immune paralysis or maladaptive tolerance. Despite those failures, the current paradigm of sepsis that predominantly centres on pathogen-associated molecular patterns and their recognition have not been revised. Damage- associated molecular patterns are known to be elevated during sepsis, particularly Adenosine Triphosphate (ATP). The project hypothesises that extracellular ATP contributes to innate immune activation and tolerance. In order to test this hypothesis, the response of human primary monocytes (white blood cells that play a major role in innate immunity) against ATP was studied. Approximately 9 whole blood samples from young Maltese donors between the ages of 18 - 30 years old were obtained in heparinised (green-top) BD Vacutainer® tubes. Monocytes from each sample were purified and exposed to LPS as a positive control or ATP for 6 hours in vitro. Enzyme-linked immunosorbent assays (ELISA) targeting the prototypical cytokine Interleukin-1β (IL-1β) found in the supernatant were measured. Altogether, the results will contribute to a growing body of evidence on DAMPs establishing a maladaptive immune response. Description: B.Sc. (Hons)(Melit.)