Staphylococcal and Streptococcal infections For Fourth- Year Medical Students Dr: Hussein Mohammed Jumaah CABM Mosul College of Medicine 1/12/2014 catalyzing2 H2O2 2 H2O + O2 Most infections of the skin, soft tissues and bone are caused by either staphylococci (mainly Aureus). or streptococci (mainly Pyogenes(. Staphylococcal infections Gram-positive form grapelike clusters Catalase-positive nonmotile, aerobic, and facultatively anaerobic. Colonising the anterior nares and skin. Divided into two groups according to their ability to produce coagulase, an enzyme that converts fibrinogen to fibrin in rabbit plasma, causing it to clot. Infections caused by Staphylococcus aureus folliculitis, furuncles, carbuncles, impetigo and the scalded skin syndrome Mid-facial cellulitis, which can result in cavernous sinus thrombophlebitis. Wound infections prolong hospital stays Treatment drainage of abscesses plus antistaphylococcal antibiotics. Prevention hand hygiene, aspetic technique, topical and systemic antibiotic prophylaxis. carbuncle folliculitis Skin infections Cannula-related infection Extremely common. Visual Infusion Phlebitis (VIP) score is a useful way of monitoring cannulae. Treatment Cannula removal and antibiotic treatment with flucloxacillin or a glycopeptide if MRSA* is suspected. * MRSA= Meticillin-resistant Staph. Aureus Staphylococci are particularly dangerous if they gain access to the blood stream. In any patient with staphylococcal bacteraemia, especially injection drug users, the possibility of endocarditis must be considered. Endocarditis Due to a penicillin-binding protein mutation. MRSA is now accounting for up to 40% of staphylococcal bacteraemia in developed countries. Also acquired other virulence factors such as Panton-Valentine leukocidin (PVL), cytolytic to PMNs *, macrophages, and monocytes. * Polymorphonucleocytes Meticillin-resistant Staph. Aureus based on the results of susceptibility testing. Milder infections,treated with clindamycin, tetracyclines or co-trimoxazole. Severe infections. Glycopeptides, linezolid and daptomycin PVL-producing Staph. infections should be treated with protein-inhibiting antibiotics (clindamycin, linezolid( Meticillin-resistant Staph. Aureus Treatment Toxin-Mediated Illnesses 1.Toxic shock syndrome 2.Food poisoning 3.Staphylococcal scalded-skin syndrome Food poisoning Inoculation of toxin-producing S. aureus into food by colonized food handlers. Even if the bacteria are killed by warming, the heat-stable toxin is not destroyed. The onset is explosive, within 1 to 6 h of ingestion,nausea and vomiting, although diarrhea, hypotension, and dehydration may also occur. Symptoms generally resolve within 8 to 10 h. The diagnosis can be established by the demonstration of bacteria or the documentation of enterotoxin in the implicated food. Treatment is entirely supportive. life-threatening disease is associated with infection by Staph. Aureus which produces a specific toxin (toxic shock syndrome toxin 1 (TSST1). It was commonly seen in young women associated with the use of highly absorbent intravaginal tampons. The toxin acts as a 'super-antigen', triggering significant T-helper cell activation and massive cytokine release. Staphylococcal toxic shock syndrome Abrupt onset with high fever, myalgia, headache, sore throat and vomiting, a generalised erythematous blanching rash resembling scarlet fever, and hypotension. progresses over a matter of hours to multisystem involvement with cardiac, renal and hepatic compromise, leading to death in %. Recovery is accompanied at days by desquamation. Staphylococcal toxic shock syndrome Is clinical and may be confirmed in menstrual cases by vaginal examination, the finding of a retained tampon and microbiological examination by Gram stain demonstrating typical staphylococci. culture and demonstration of toxin production are confirmatory. The diagnosis Immediate and aggressive fluid resuscitation and an intravenous antistaphylococcal antibiotic (flucloxacillin or vancomycin), with the addition of a protein synthesis inhibitor (e.g. clindamycin) to inhibit toxin production. Intravenous immunoglobulin is occasionally added in the most severe cases. Women who recover should be advised not to use tampons for at least 1 year and should also be warned that, due to an inadequate antibody response to TSST1, the condition can recur. Treatment Are nasopharyngeal and gut commensals, Gram-positive spherical to ovoid form chains when grown. Most are facultative anaerobes. Classified by the haemolysis they produce on blood agar and by their serotypes. In the medical setting, the most important groups are the : 1. alpha-hemolytic :S. pneumoniae and Streptococcus Viridans. 2. beta-hemolytic streptococci of Lancefield groups A and B. Streptococcal infections Group A (or occasionally C and G) causing pharyngitis, tonsillitis may lead to scarlet fever, if the infecting strain produces a streptococcal pyrogenic exotoxin A, B, and C. Common in school-age children,diffuse erythematous rash occurs, blanches on pressure with circumoral pallor. The tongue becomes red and swollen ('strawberry tongue). The rash disappea in 7-10 days. Treatment : benzylpenicillin or oral penicillin plus symptomatic measures. Scarlet fever Associated with severe group A (occasionally C or G) streptococcal skin infections, producing one of a variety of toxins such as pyogenic exotoxin A. Like staphylococcal toxic shock syndrome toxin, these act as superantigens, stimulating T-helper cells and a dramatic cytokine response. Streptococcal toxic shock syndrome Initially, an influenza-like illness occurs signs of localised infection, most often involving the skin and soft tissues. A faint erythematous rash, mainly on the chest, rapidly progresses to circulatory shock. Without aggressive management, multi-organ failure will develop. Streptococcal toxic shock syndrome Fluid resuscitation, with parenteral antistreptococcal antibiotic, usually with benzylpenicillin and a protein inhibitor such as clindamycin to inhibit toxin production. Intravenous immunoglobulin. If necrotising fasciitis is present, it should be treated as with urgent dbridement. Treatment 1.Rheumatic fever 2.Acute post-streptococcal glomerulonephritis These occur 2-3 weeks after strept.sore throat, and they are immunological reaction to strept. Antigens. Remote complications of streptococcal sore throat