The role of Staphylococcus aureus quorum sensing in cutaneous and systemic infections.

BACKGROUND: Staphylococcus aureus is a leading cause of human bacterial infections worldwide. It is the most common causative agent of skin and soft tissue infections, and can also cause various other infections, including pneumonia, osteomyelitis, as well as life-threatening infections, such as sepsis and infective endocarditis. The pathogen can also asymptomatically colonize human skin, nasal cavity, and the intestine. S. aureus colonizes approximately 20-30% of human nostrils, being an opportunistic pathogen for subsequent infection. Its strong ability to silently spread via human contact makes it difficult to eradicate S. aureus. A major concern with S. aureus is its capacity to develop antibiotic resistance and adapt to diverse environmental conditions. The variability in the accessory gene regulator (Agr) region of the genome contributes to a spectrum of phenotypes within the bacterial population, enhancing the likelihood of survival in different environments. Agr functions as a central quorum sensing (QS) system in S. aureus, allowing bacteria to adjust gene expression in response to population density. Depending on Agr expression, S. aureus secretes various toxins, contributing to virulence in infectious diseases. Paradoxically, expressing Agr may be disadvantageous in certain situations, such as in hospitals, causing S. aureus to generate Agr mutants responsible for infections in healthcare settings. MAIN BODY: This review aims to demonstrate the molecular mechanisms governing the diverse phenotypes of S. aureus, ranging from a harmless colonizer to an organism capable of infecting various human organs. Emphasis will be placed on QS and its role in orchestrating S. aureus behavior across different contexts. SHORT CONCLUSION: The pathophysiology of S. aureus infection is substantially influenced by phenotypic changes resulting from factors beyond Agr. Future studies are expected to give the comprehensive understanding of S. aureus overall profile in various settings.

Pathogenic role of the staphylococcal accessory gene regulator quorum sensing system in atopic dermatitis.

The skin is home to various bacteria, archaea, fungi, and viruses, collectively referred to as the skin microbiota. Patients with certain skin diseases reportedly have unique skin "dysbiosis," a condition involving imbalanced microbiota, suggesting that dysbiosis in the skin may be either causal or a consequence of specific skin diseases. Atopic dermatitis (AD) is the most common allergic skin disease that affects 15-20% of children and 2-10% of adults worldwide. Both intrinsic genetic factors, such as susceptibility to type 2 inflammation or skin barrier dysfunction, and extrinsic environmental factors, such as air pollen and skin microbiota, contribute to AD. Staphylococcus aureus, which does not often colonize the skin of healthy individuals, is commonly identified in the lesional skin of patients with AD and is correlated with the disease flare. However, the role of S. aureus in the pathogenesis of AD has not been elucidated. Here, we discuss the pathological behavior of S. aureus, focusing on accessory gene regulator (Agr) quorum sensing, which is a fundamental bacterial cell-to-cell interaction mechanism that affects the behavior of S. aureus and other members of the microbial community. Importantly, beyond bacteria-bacteria interactions, the Agr quorum sensing system also regulates various virulence factors, which induce type 2 and IL-17-dependent skin inflammation in the host. Furthermore, the colonization of Agr-positive S. aureus in early life accelerates the development of pediatric AD. Finally, we aim to highlight the current efforts to establish novel therapeutic methods to ameliorate or prevent AD through Agr-targeted intervention.

Cutaneous manifestations of coronavirus disease 2019 patients in Japan.

Some patients with coronavirus disease 2019 (COVID-19) develop skin manifestations. There may be regional and racial differences in the frequency and type of COVID-19-associated skin manifestations. There are, however, few reports on skin manifestations in COVID-19 patients in Asia, including Japan. We retrospectively investigated the frequency, type, and clinical course of skin manifestations in Japanese patients with COVID-19. From 22 February 2020 to 16 August 2021, 738 Japanese patients (median age 59 years, 55% male) with laboratory-confirmed COVID-19 on polymerase chain reaction or antigen tests were admitted to our hospital. We mainly admitted patients with mild to moderate severity who had symptoms such as cough, fever, and oxygen demand but did not require mechanical ventilation. A total of 2.8% (21/738) of the COVID-19 patients treated at our hospital were diagnosed with viral eruptions caused by COVID-19. Of the 21 patients, 19 developed erythematous papules, and two developed urticaria. There were no cases of pernio-like lesions, known as COVID toes. The median duration from the onset of other COVID-19 symptoms to the development of skin manifestations was 9 days. This study revealed that approximately 2-3% of Japanese patients with COVID-19 developed COVID-19-associated viral eruptions, most of which were erythematous papules.

Three cases of COVID-19 patients presenting with erythema.

Individuals infected with the novel coronavirus (Severe Acute Respiratory Syndrome Coronavirus 2 [SARS-CoV-2]) who develop coronavirus disease 2019 (COVID-19) experience many symptoms; however, cutaneous manifestations are relatively rare. The authors encountered three patients with COVID-19 who presented with erythema and suspected viral rash. In all cases, erythema appeared after the onset of the initial symptoms of COVID-19. Erythema was considered to be caused by COVID-19 and not a drug-induced eruption because, in all cases, erythema was relieved merely by external medicine and oral antihistamines, without discontinuing the original medication. The authors' hospital accepted 69 COVID-19 patients between 22 February 2020 and 31 May 2020 and, of these, three (4.3%) exhibited eruptions, and all cases presented erythema. Except for seven patients who exhibited positive nasopharyngeal swab tests for SARS-CoV-2 RNA but no symptoms, three (4.8%) of the remaining 62 patients exhibited erythema. Although various types of eruptions have been reported in patients with COVID-19, erythema was the only type in our patients. Erythema in the three patients exhibited many similarities to that previously reported in COVID-19 patients, particularly in the manner it appeared and disappeared. For these reasons, these three cases were considered typical examples of erythema in patients with COVID-19. Considering previous studies and the three cases reported here, there is a high probability that SARS-CoV-2 can cause erythema.