Increased susceptibility to Staphylococcus aureus colonization of the skin of the NOA mouse: a potentially useful animal model for evaluating antiseptic effects

The contribution of mouse models to understanding atopic dermatitis

Atopic dermatitis (AD) is a dermatological disease accompanied by dry and cracked skin with severe pruritus. Although various therapeutic strategies have been introduced to alleviate AD, it remains challenging to cure the disorder. To achieve such a goal, understanding the pathophysiological mechanisms of AD is a prerequisite, requiring mouse models that properly reflect the AD phenotypes. Currently, numerous AD mouse models have been established, but each model has its own advantages and weaknesses. In this review, we categorized and summarized mouse models of AD and described their characteristics from a researcher's perspective.

Beta-hemolysin promotes skin colonization by Staphylococcus aureus

Colonization by Staphylococcus aureus is a characteristic feature of several inflammatory skin diseases and is often followed by epidermal damage and invasive infection. In this study, we investigated the mechanism of skin colonization by a virulent community-acquired methicillin-resistant S. aureus (CA-MRSA) strain, MW2, using a murine ear colonization model. MW2 does not produce a hemolytic toxin, beta-hemolysin (Hlb), due to integration of a prophage, Sa3mw, inside the toxin gene (hlb). However, we found that strain MW2 bacteria that had successfully colonized murine ears included derivatives that produced Hlb. Genome sequencing of the Hlb-producing colonies revealed that precise excision of prophage Sa3mw occurred, leading to reconstruction of the intact hlb gene in their chromosomes. To address the question of whether Hlb is involved in skin colonization, we constructed MW2-derivative strains with and without the Hlb gene and then subjected them to colonization tests. The colonization efficiency of the Hlb-producing mutant on murine ears was more than 50-fold greater than that of the mutant without hlb. Furthermore, we also showed that Hlb toxin had elevated cytotoxicity for human primary keratinocytes. Our results indicate that S. aureus Hlb plays an important role in skin colonization by damaging keratinocytes, in addition to its well-known hemolytic activity for erythrocytes.