Gram(+) Pyogenic Cocci

Question 1

Streptococcus Pyogenes (Group A)

Answer 1

-normal bacterial flora of skin and oropharynx
-pharyngitis (strep throat), cellulitis, myositis, pneumonia, puerperal sepsis.
-exotoxins plus cytotoxins.
-Rheumatic fever and glomerulonephritis–complications -
Scarlet Fever (red rash-erythrogenic toxin)
-erysipelas (erythematous swelling of skin)
-Impetigo (intraepidermal infection): spread direct contact in children

Question 2

Staphylococcus Aureus (coagulase positive)

Answer 2

• natural flora on skin–innoculation following injury
• leading cause of infective endocarditis -furuncles, carbuncles, scalded skin syndrome (desquamantion), osteomyelitis, bacterial arthritis
• Septicemia, TSS, food posioning,
• MRSA-antibiotic resistance plus virulence factors (toxins + proteolytic enzymes) encoded on plasmids.

Question 3

Coagulase negative Staphylococcus Epidermitis

Answer 3

• Gram(+) bacteria
• normal bacterial flora (skin, mucosal surfaces)
• not as serious as S. aureus infections
• low grade fever
• spread from contaminated medical and prosthetic devices. -nosocomial variants multidrug resistant. (use non-beta lactam antibiotics)

Question 4

Streptococcus Pneumoniae (pneumococcus)

Answer 4

• Gram(+) cocci
• pneumonia, sinusitis, otitis media, meningitis
• normal flora in oropharynx (opportunist)
• infection follows cold or influenza
• insults such as smoking and alcohol
• capsule blocks opsonization by complement C3b (inhibits macrophages, antibody needed to kill) -Self limiting, Not severe

Question 5

Group B Streptococci

Answer 5

• Gram(+) cocci
• Neonatal Pneumonia, meningitis, and sepsis
• 30% infected infants die (1000’s infected yearly)
• Normal vaginal flora in 10-30% women
• spread to infant through birth canal
• Risk factor is low level of maternal IgG antibodies