A Case of Hospital-Acquired Mrsa
Meera Chand, John Holton in Case Studies in Infection Control, 2018
TSST-1 is a superantigen that stimulates a broad range of T-cells to release TNF and IL-1, leading to a generalized acute inflammatory reaction and shock. This leads to the toxic shock syndrome. S. aureus enterotoxins (SEA-SE/U2) are superantigens and have a similar mechanistic effect to TSST-1, but induce food poisoning with rapid onset of nausea, vomiting, and sometimes diarrhoea. Alpha toxin is a pore-forming toxin, which induces cell necrosis by allowing intracellular contents to leak out of the affected cells, causing local host cell death. PVL is associated with necrotizing pneumonia and severe invasive skin or bone infections. It induces cytolysis of cells, particularly neutrophils, thus abrogating the host innate immune response. Exfoliatin A and B produced by S. aureus affects cadherin intercellular adhesion proteins and their loss leads to separation of the upper skin layers, with desquamation of the epidermal layer. This illness is called scalded skin syndrome.
Principles of Clinical Diagnosis
Susan Bayliss Mallory, Alanna Bree, Peggy Chern in Illustrated Manual of Pediatric Dermatology, 2005
PathogenesisNonbullous impetigoStaphylococcus aureus causes in up to 85% of casesGroup A streptococcus causes in up to 30% of cases with groups B, C, G and F rarely presentEpidemics are caused by Streptococcus pyogenes M-serotypes (i.e. 2, 49, 53, 55–57, 60)Bullous impetigoStaphylococcus aureus is the causative organism with 80% from phage group 2S. aureus produces epidermolytic toxins A or B (exfoliatin) which interacts with desmoglein-1 to form bullaeCausative organisms enter through breaks in the skin such as abrasions or insect bitesCarriage of the organism in the nares can be a source of infection
Infections and infestations affecting the nail
Eckart Haneke in Histopathology of the NailOnychopathology, 2017
Impetigo contagiosa is the most frequent superficial skin infection and mainly seen in children between 2 and 5 years although, in principle, any age may be affected. Heat and humidity favor its outbreak.62 Approximately 30% of impetigo cases are bullous, which is due to staphylococcal exfoliatin toxins. Staphylococcus aureus and, more rarely, β-hemolytic streptococci, are the most common causes of putrid infections of the nail. Around the nail, they give rise to bulla repens (bulla rodens), also called runaround. This starts as a clear blister of the proximal to lateral nail fold, which soon becomes cloudy and yellow. Removal of the blister roof and disinfective baths are usually sufficient for treatment; systemic antibiotics are rarely needed for this superficial infection. The clinical differential diagnoses are burns and congelations as well as other blistering dermatoses.
Echtyma gangrenosum caused by coinfection with group A Streptococcus and Staphylococcus aureus: an emerging etiology? Case reports and literature review
Published in Acta Clinica Belgica, 2021
Antonio Ulpiano Trillig, Véronique Y. Miendje Deyi, Pierre Youatou, Deborah Konopnicki
The Gram staining of several lesion swabs showed white blood cells and gram-positive cocci both in chains and in clusters; cultures grew both GAS (abundant or confluent) and SA (moderate quantity) later found to be sensitive, respectively, to methicillin and penicillin. Resistance to clindamycin was found in the SA but not in the GAS strain. Typing showed an emm81 Streptococcus and the absence of gene coding for toxin production by the SA (Panton-Valentin TSST-1, exfoliatin toxins a and b, spa type t359). Blood cultures were negatives as well as serology tests for HIV, Rickettsia, Syphilis, Hepatitis B and C and Bartonella.
Related Knowledge Centers
- Cadherin
- Cell Adhesion
- Desmosome
- Exotoxin
- Glutamic Acid
- Keratinocyte
- Serine Protease
- Staphylococcal Scalded Skin Syndrome
- Stratum Granulosum
- Staphylococcus Aureus