Bacteria present in the human body are innocuous, providing beneficial functions, some of which are necessary for correct body function. However, other bacteria are able to colonize, invade, and cause damage to different tissues, and these are categorised as pathogens. These pathogenic bacteria possess several factors that enable them to be more virulent and cause infection. Bacteria have a great capacity to adapt to different niches and environmental conditions (presence of antibiotics, iron depletion, etc.). Antibiotic pressure has favoured the emergence and spread of antibiotic-resistant bacteria worldwide. Several studies have reported the presence of a relationship (both positive and negative, and both direct and indirect) between antimicrobial resistance and virulence among bacterial pathogens. This review studies the relationship among the most important Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) taking into account two points of view: (i) the effect the acquisition of resistance has on virulence, and (ii) co-selection of resistance and virulence. The relationship between resistance and virulence among bacteria depends on the bacterial species, the specific mechanisms of resistance and virulence, the ecological niche, and the host.

中文翻译：

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革兰氏阴性菌毒力与耐药性的关系

人体中存在的细菌是无害的，可提供有益的功能，其中某些功能对于正确的身体功能是必需的。但是，其他细菌也能够在不同组织中定植，侵入并造成损害，这些细菌被归类为病原体。这些病原细菌具有多种因素，使其更具毒性并引起感染。细菌具有适应不同生态位和环境条件（存在抗生素，铁耗竭等）的强大能力。抗生素压力促进了耐药性细菌在全球范围内的出现和传播。几项研究报告了细菌病原体之间的耐药性和毒力之间存在正相关和负相关，以及直接和间接相关。大肠埃希氏菌和铜绿假单胞菌考虑了两种观点：（i）获得抗药性对毒力的影响，以及（ii）抗药性和毒力的共同选择。细菌之间的抵抗力和毒力之间的关系取决于细菌种类，抵抗力和毒力的具体机制，生态位和宿主。