Microbiological assessment of microphones used in churches in Calabar, Nigeria

Background: Bacteria can survive on the surface of the microscopic grooves and cracks and will go unnoticed, hence the presence of pathogenic microorganisms on the user interface of handheld microphone poses a potential public health risk. Aim: The aim of this study was to isolate and identify potential pathogenic micro-organisms associated with used microphones, between April to August, 2021 in Calabar, Nigeria. Methodology: One hundred and fifty samples were collected (75 each) from the mouthpiece (head) and handles of the various microphones from different churches in Calabar using sterile cotton wool swab moistened with sterile peptone water. Samples were inoculated on Blood agar, Cysteine Lactose Electrolyte Deficient agar and incubated at 37oC for 24 - 48 hours and also on Sabouraud’s Dextrose agar at room temperature for 2 - 7 days. Isolates were characterized macroscopically, microscopically and biochemically. Results: Overall, 96(64.0%) of the 150 samples from microphones studied yielded growth of microbes with the mouthpiece being more significantly contaminated 57(76.0%) than the handles 39(52.0%) (X2=9.375, p=0.0022). The number of microphones colonized with bacteria were significantly more 62(41.3%) than those carrying fungi 34(22.7%) (X2=7.45, p=0.0063). Staphylococcus aureus ranked highest (53.2%) among the bacterial isolates followed by Bacillus species (29.0%) and Escherichia coli (17.7%) while in the case of those colonized by fungi, Candida species ranked higher (91.2%) than Aspergillus flavus (8.8%). The distribution of microbes by church group was statistically insignificant (X2=0.508, p=0.1969). Conclusion: This study has shown that used microphones carry various microbes including potential bacterial and fungal pathogens, hence can play reservoir role in microbial infection transmission. Frequent cleaning and creation of awareness on the health hazards associated with improper use and maintenance of microphones is recommended

Blast wave mitigation by dry aqueous foams

International audienceThis paper presents results of experiments and numerical modeling on the mitigation of blast waves using dry aqueous foams. The multiphase formalism is used to model the dry aqueous foam as a dense non-equilibrium two-phase medium as well as its interaction with the high explosion detonation products. New experiments have been performed to study the mass scaling effects. The experimental as well as the numerical results, which are in good agreement , show that more than an order of magnitude reduction in the peak overpressure ratio can be achieved. The positive impulse reduction is less marked than the overpressures. The Hopkinson scaling is also found to hold particularly at larger scales for these two blast parameters. Furthermore, momentum and heat transfers, which have the main dominant role in the mitigation process, are shown to modify significantly the classical blast wave profile and thereafter to disperse the energy from the peak overpressure due to the induced relaxation zone. In addition, the velocity of the fireball, which acts as a piston on its environment, is smaller than in air. Moreover , the greater inertia of the liquid phase tends to project the aqueous foam far from the fireball. The created gap tempers the amplitude of the transmitted shock wave to the aqueous foam. As a consequence, this results in a lowering of blast Communicated by O. Igra. wave parameters of the two-phase spherical decaying shock wave