The Optimum Duration of Flushing Dental Unit Waterlines for Microbial Removal

ABSTRACT@#This study aims to evaluate the optimum duration of flushing dental unit waterlines (DUWLs) in Universiti Sains Islam Malaysia (USIM) dental polyclinics for removal of heterotrophic bacteria. Water samples were obtained from triple air syringes at each dental chair from oral surgery clinic, outpatient clinic and polyclinic 17 at Faculty of Dentistry, USIM after 16 and 64 hours of not operating the dental units as baseline samples. This is followed by sampling after continuous flushing at 30 seconds, 1 minute, 2 minutes and 3 minutes of flushing duration. The levels of heterotrophic plate count (HPC) for each flushing duration were determined by quantification of colony forming units (CFUs) after cultivation of samples on plate count agar (PCA), R2A agar and 5% sheep blood agar (SBA). Statistically, there was no significant reduction in CFUs of HPC for all flushing duration compared to baseline (P > 0.05) with the most notable HPC reducing level after 1 minute and 3 minutes of flushing DUWLs. However, HPC level at USIM dental clinics is still exceeding the recommendation by Centers for Disease Control and Prevention (CDC) which should be less than 500 CFU/mL. The existing method of controlling DUWLs contamination in USIM dental clinics is only by flushing DUWLs 1 minute every morning prior to dental treatment as recommended by Malaysian Dental Council (MDC) without the use of chemical germicides. Thus, the flushing method alone is not reliable to reduce the number of microorganisms in the DUWLs.

This study demonstrated that the isolated LAB from E. conferta has antibacterial effects against several foodborne pathogens. These LAB strains may have potential as a natural food preservative

Aims@#The aim of the study was to isolate and characterise bacteriophages specific to Pseudomonas aeruginosa carrying virulence genes. @*Methodology and results@#Four clinical strains of P. aeruginosa CL1, CL2, CL3 and CL4 were obtained from Queen Elizabeth Hospital, Kota Kinabalu, Sabah. The bacterial strains were screened for virulence genes exoS, toxA and oprI and biofilm production. Six P. aeruginosa specific bacteriophages, namely PAtk1, PAtk2, PAtk3, PAtk4, PAtk5 and PAtk6, were isolated from Tasik Kejuruteraan, Universiti Kebangsaan Malaysia. These bacteriophages were screened for lytic spectrum against P. aeruginosa and two species of Enterobacteriaceae (Escherechia coli and Salmonella Typhi). PCR results showed that all strains possessed exoS, toxA and oprI genes except CL2 that lacked exoS. Nevertheless, it was CL2 that produced the highest biofilm density. Further, based on Transmission Electron Microscopy, PAtk15 and PAtk6 were classified into the family Myoviridae and Siphoviridae, respectively. Among all six isolated phages, only PAtk4 and PAtk6 showed the broadest lytic spectrum in which lytic activity was observed against all clinical P. aeruginosa strains. @*Conclusion, significance and impact of study@#In this study we reported the isolation of six bacteriophages from Myoviridae and Siphoviridae that are specific to P. aeruginosa possessing exoS, toxA and oprI genes. Bacteriophages Patk4 and PAtk6 were able to infect all four strains of P. aeruginosa, making these phages potential agents in combating infections by the bacterium.

Molecular detection of Salmonella enterica serovar Typhi by Vi-qPCR

Aims@#To develop a real-time polymerase chain reaction system Vi-qPCR in the detection of Salmonella enterica serovar Typhi (S. Typhi), targeting the vexC gene encoding for Vi antigen (capsular polysaccharide antigen) and to evaluate its sensitivity and specificity performance using pure cultures of S. Typhi and other enteric pathogens. @*Methodology and results@#Microbiological, biochemical and serotyping tests were conducted to determine the phenotypic characteristics of S. Typhi and other enteric pathogens in our collection. Primers were designed using Primer3 software and their in-silico specificity were analysed using Basic Local Alignment System Tool (BLAST). Optimisation of PCR annealing temperature was done prior to assessment of sensitivity and specificity performance against artificial serially diluted seeded stools. The primers were found to be 100% specific in the detection of S. Typhi towards 32 tested clinical strains. Verification of gene amplification by comparing the nucleotide sequences against reference genes in the GenBank database revealed high specificity to S. Typhi. Statistical analysis indicates that this method results in 100% sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Moreover, Vi-qPCR allows the detection of S. Typhi as low as 131.4 CFU/g of stool sample. @*Conclusion, significance and impact of study@#A rapid and sensitive method for detection of Salmonella enterica serovar Typhi (S. Typhi) is desired as a diagnostic tool to improve typhoid management. The Vi-qPCR represent a promising non-invasive diagnostic tool for medical microbiology laboratories as a method for the detection of S. Typhi in both pure culture and stool specimens especially in chronic asymptomatic carriers where shedding of S. Typhi is intermittent and sometimes occurs in low level.