Bacterial Infection pptx - D. Kadhim

Bacterial Infection

Staphylococcal infections

Staphylococci, gram-positive cocci in the family Micrococcaceae, form grapelike clusters on Gram's stain are usually found colonising the anterior nares and skin
Traditionally, staphylococci were divided into two groups according to their ability to produce coagulase enzyme
1)coagulase-positive _ Staph. Aureus
_Staph. Intermedius
2) coagulase-negative _ Staph. Epidermidis
_Staph. Saprophyticus
_Staph. lugdunensis
_ Staph. Haemolyticus

• Infections caused by Staphylococcus aureus

• 1-Skin and Soft Tissue Infections
• Folliculitis, Furuncle, carbuncle, Cellulitis , Impetigo and Surgical wound infections.
• 2-Musculoskeletal Infections
• Septic arthritis, Osteomyelitis, Pyomyositis and Psoas abscess.
• 3-Respiratory Tract Infections
• Ventilator-associated or nosocomial pneumonia, Septic pulmonary emboli, Postviral pneumonia (e.g., influenza) and Empyema.
• 4-Bacteremia and Its Complications
• Sepsis, septic shock, Metastatic foci of infection (kidney, joints, bone, lung) and Infective endocarditis
•
• 5-Toxin-Mediated Illnesses
• Toxic shock syndrome, Food poisoning ,Staphylococcal scalded-skin syndrome .

• Staphylococcal scalded skin syndrome

Staphylococcal scalded skin syndrome (SSSS) is staphylococcal epidermal necrolysis, cause a spectrum of superficial blistering skin disorders caused by the exfoliative toxins of some strains of Staphylococcus aureus.
• It is a syndrome of acute exfoliation of the skin typically following an erythematous cellulitis.
• Severity of staphylococcal scalded skin syndrome varies from a few blisters localized to the site of infection to a severe exfoliation affecting almost the entire body. A mild form of the illness involving desquamation of just the skin folds following impetigo.it is a relatively benign condition, and responds to treatment with flucloxacillin

• Staphylococcal toxic shock syndrome (TSS)

• This serious and 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 intra-vaginal tampons but can occur with any Staph. aureus infection involving a relevant toxin-producing strain. The toxin acts as a 'super-antigen', triggering significant T-helper cell activation and massive cytokine release.

• Clinical features

• TSS has an abrupt onset with high fever, generalized systemic upset (myalgia, headache, sore throat and vomiting), a generalized erythematous blanching rash resembling scarlet fever, and hypotension.
• It rapidly progresses over a matter of hours to multisystem involvement with cardiac, renal and hepatic compromise, leading to death in 10-20%. Recovery is accompanied at 7-10 days by desquamation .

• Diagnosis

• The diagnosis 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. Subsequent culture and demonstration of toxin production are confirmatory.
• Management
• Treatment is with immediate and aggressive fluid resuscitation and an intravenous ant-staphylococcal antibiotic (flucloxacillin or vancomycin), usually 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.

The selection of antibiotic thearpy for staph. Infection.

The selection of ant-staph. Depended on sensitivity test

• Streptococcal infections

Streptococci are nasopharyngeal and gut commensals, which appear as Gram-positive cocci in chains .They are classified by the haemolysis they produce on blood agar in to:-
1)B-heamolytic streptococcai ((A,B,C andG).
2)α-heamolytic streptococcai ((s. pneumonae ,s. viridance))
3) enterococcai ((E-faecalis, E. faecillium)).

• The commom disease caused by strep.groupA

Skin and soft tissue infection (including erysipelas, impetigo, necrotising fasciitis)
Streptococcal toxic shock syndrome
Puerperal sepsis
Scarlet fever
Glomerulonephritis
Rheumatic fever
Bone and joint infection
Tonsillitis

• Streptococcal toxic shock syndrome

• This is associated with severe group A (or occasionally group C or G) streptococcal skin infections producing one of a variety of toxins such as pyogenic exotoxin A. Like staphylococcal toxic shock syndrome toxin (see above), these act as super-antigens, stimulating T-helper cells and a dramatic cytokine response.
• Initially, an influenza-like illness occurs within 50% of cases, signs of localized 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.

• Treatment
• Fluid resuscitation, with parenteral antistreptococcal antibiotic therapy, usually with benzylpenicillin and a protein inhibitor such as clindamycin to inhibit toxin production.
• Intravenous immunoglobulin is usually administered in addition. If necrotizing fasciitis is present, it should be treated with urgent debridement.

Scarlet fever

• Scarlet fever is caused by(a group A streptococcus) produces erythrogenic toxin in an individual who does not possess neutralizing antitoxin antibodies.
• Clinical features
• A mild disease, which mainly affects children, incubation is 2-4 days following a streptococcal infection, usually in the pharynx. Regional lymphadenopathy, fever, rigors, headache and vomiting are present. The rash, which blanches on pressure, usually appears on the second day of illness; it initially occurs on the neck but rapidly becomes punctate, erythematous and generalized.
• It is typically absent from the face, palms and soles, and is prominent in the flexures. The rash usually lasts about 5 days and is followed by extensive desquamation of the skin .The face is flushed, with characteristic circumoral pallor .
• The patient is infective for 10-21 days after the onset of the rash, unless treated with penicillin. Scarlet fever may be complicated by peritonsillar or retropharyngeal abscesses and otitis media.

Diagnosis

• The diagnosis is established by the typical clinical features and culture of a throat swab. Elevated antistreptolysin O and anti-DNase B levels in convalescent serum are indicative of streptococcal infection.
• Treatment
• Penicillin is the drug of choice and is given orally as phenoxymethylpenicillin 500 mg four times daily for 10 days. Individuals allergic to penicillin can be treated effectively with erythromycin 250 mg four times daily for 10 days. Treatment is usually effective in preventing rheumatic fever and acute glomerulonephritis which are non-supportive complications of streptococcal pharyngitis. Unlike acute rheumatic fever, streptococcal nephritis may also complicate streptococcal skin infection.

Staphylococcal scalded-skin syndrome