Staphylococcal Disease

Staphylococcal Disease

General Considerations 

• Staphylococci are a common cause of pyogenic infections in infants and children. Two common strains are:
• Staphylococcus aureus, which are coagulase positive and pathogenic.
• S. albus which are coagulase negative and generally nonpathogenic.

Disease due to staph, aureus may be due to tissue invasion or may result from a variety of toxins and enzymes elaborated by these organisms. Among enzymes penicillinase or beta-lactamase inactivates penicillin and make these strains resistant to this antibiotic.

Epidemiology

• 20-30% of normal individuals carry staph aureus in their anterior nares.
• Organisms may be transmitted from nose to skin by direct contact.
• Spread by fomites is very rare.
• New born infants are extremely prone to staph infection. Nasopharynx, umbilical stump and skin are common sites of colonization.

Pathogenesis 

• The intact skin and mucouc membranes serve as barriers to invasion by staph.
• Development of staphylococcal disease is related to resistance of host and to virulence of the organism.
• Suppuration is the hallmark of staphylococcal disease.

Clinical Manifestations 

A). Skin: Pyogenic skin infection is the commonest manifestation. It includes impetigo, folliculitis, furunculosis, carbuncles, cellulitis, bullous impetigo and toxic epidermo necrolysis - the last two are characteristically seen in the new born period.

B). Respiratory Tract 

Upper respiratory infection due to staph, aureus is rare, but sinusitis and otitis media may occur.
Recently staphylococcal pharyngitis has become common.

Lower respiratory infection: Pneumonia: It is usually associated with marked systemic symptoms e.g. high fever, abdominal pain, tachypnoea and localized or diffuse bronchopneumonia. Staph as a rule causes necrotizing pneumonia and appearance of cavities in chest x-ray. Empyema, pneumothorax and broncho-pulmonary fistulae develop frequently. Generally infants are affected.

C). Septicemia: Onset is acute and marked by fever, chills, nausea and vomiting. Organisms may subsequently lodge at distant sites leading to meningitis, osteomyelities, septic arthritis, acute bacterial endocarditis, and renal and perinephric abscesses.

D). Intestinal Tract:

• Staph enterocolitis: This results from prolonged use of antibiotics which alters normal intestinal flora leading to overgrowth by S. aureus.
• Food poising: It results from ingestion of staph enterotoxin in contaminated food. Two to six hours after taking infected food, sudden severe vomiting followed by diarrhoea and low grade fever develops. Rarely shock and death may occur.