Spinelli Elisa, Requena Teresa, Caruso Marta, Parisi Antonio, Capozzi Loredana, Difato Laura, Normanno Giovanni
Department of Science of Agriculture, Food and the Environment (SAFE) University of Foggia Foggia Italy.
Research Institute of Food Science CIAL (CSIC-UAM) Madrid Spain.
Food Sci Nutr. 2020 Jul 31;8(9):4739-4745. doi: 10.1002/fsn3.1698. eCollection 2020 Sep.
A known amount (10 cfu/ml) of animal origin Methicillin-resistant (MRSA) ST398/t011/V and of human origin MRSA ST1/t127/IVa strains were individually inoculated into cheese and hamburger samples. The pH of each food matrix was gradually decreased from 6.0 down to 2.0 during a period of about 2 hr, under conditions simulating the mechanical digestion of the human stomach. Afterward, the MRSA strains were recovered by using a MRSA-specific plating medium. Although both strains showed a certain acidic resistance, they showed different responses at low pH values during the experiment: ST398 survived unharmed during the course of the experiments to the last stage at pH 2 where counts of 6.4 cfu/g for the hamburger and 7.5 log cfu/g for cheese assays were obtained. In contrast, the ST1 population was no longer detectable at pH 3 in the hamburger and at pH 2 in the cheese assays. To the best of our knowledge, this is the first study that investigates the ability of MRSA to overcome the acidic conditions of the human stomach and that adds new evidence that might contribute to expand the scientific knowledge on the significance of MRSA in the food safety debate.
将已知数量（10 cfu/ml）的动物源耐甲氧西林金黄色葡萄球菌（MRSA）ST398/t011/V和人源MRSA ST1/t127/IVa菌株分别接种到奶酪和汉堡样品中。在模拟人类胃部机械消化的条件下，每种食物基质的pH值在约2小时内从6.0逐渐降至2.0。之后，使用MRSA特异性平板培养基回收MRSA菌株。尽管两种菌株都表现出一定的耐酸性，但在实验过程中它们在低pH值下表现出不同的反应：ST398在实验过程中安然存活至最后阶段，在pH 2时，汉堡中的计数为6.4 cfu/g，奶酪检测中的计数为7.5 log cfu/g。相比之下，在汉堡中pH 3时以及奶酪检测中pH 2时，ST1群体不再可检测到。据我们所知，这是第一项研究MRSA克服人类胃部酸性条件能力的研究，并且提供了新的证据，可能有助于扩展关于MRSA在食品安全辩论中的重要性的科学知识。
