Section 2: Gram positive cocci (clinical bacteriology) Flashcards
Where is Staphylococci found?
normal flora of skin, upper respiratory tract, and GI
What is the morphology of staphylococci?
spherical-cocci grapelike clusters G+ non motile non spore forming
What are the metabolic characteristics of staphylococci?
faculative anaerobes
catalase positive
ferment sugars
What is the morphology of Streptococci?
spherical-cocci in chains G+ non-motile non-endospore forming
What are the metabolic characteristics of streptococci?
require rich media for growth
blood provides necessary enzymes
aerotolerant, no need for catalase enzyme
What are the two ways to classify streptococci?
hemolysins and lancefield groups and the 4 groupings
What defines alpha-hemolysis streptococci?
partial hemolysis with greenish cast around colonies
What defines beta-hemolysis streptococci?
complete hemolysis of blood cells, creates clear area around colonies
What defines gamma-hemolysis streptococci?
no lysis of blood cells
What is are the four groupings of streptococci that includes all streptococci?
- lactic streptococci
- endterococci
- non-beta hemolytic streptococci
- beta hemolytic streptococci
What are the features of lactic streptococci?
non pathogenic
no hemolysis (gamma)
found in milk products
What are the features of enterococci?
lancefield group D normal flora of GI different hemolysis patterns commonly cause UTIs opportunistic pathogens
What are the features of non-beta hemolytic streptococci?
viridans streptococci
large heterogenous gourp, no lancefield antigen, alpha hemolysis
formal flora of mouth and respiratory tract
may cause tooth decay
may cause bacterial endocarditis
What are the features of beta hemolytic streptococci?
lancefield group A-streptococcus pyogenes
lancefield group B-streptococcus agalactiae
What are the characteristics of the family neisseriaceae?
contains both pathogenic and non-pathogenic genera and species
pathogenic species=fastidious
oxidase positive
Which of the staphylococci are coagulase negative?
staphylococcus epidermis
staphylococcus saprolyticus
(staph. aureus is coagulase positive)
What can staph. aureus cause (pathogenesis) ?
furuncles and carbuncles impetigo folliculitis scalded skin syndrome TSS pneumonia osteomyelitis catheter and shunt infections wound infections enteritis MRSA
What situations are likely to cause staph. epidermis infections?
catheters, prosthetic joints, artificial heart valves
and blood draws are frequently contaminated, so re-test to confirm infection
What is a leading cause of UTIs in sexually active females?
staphylococcus saprolyticus (second only to E. coli)
What can streptococci pyogenes cause (pathogenesis)?
strep. pharyngitis
strep. impetigo
cellulitis
erysipelase (St.Anthony’s fire)
scarlet fever
post strep diseases: rheumatic fever, glomerulonephritis
What bacteria can cause neonatal meningitis, pneumonia, and sepsis?
streptococci agalactiae
What can streptococcus pneumoniae cause?
pneumonia
ottis media and sinusitis
meningitis
osteomyelitis
