bacteria Flashcards
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staphylococcus
G+,non-motile,non spore forming.facultative anaerobes.S.aureus is coagulase positive.non capsulated.
virulence factors
toxins and enzymes
toxins
hemolysins ,exfoliative toxins A and B,Toxic shock syndrome toxin-1 and enterotoxins
enzymes
Beta lactamase,catalase,coagulase,DNase,hyaluronidase ,lipases,nucleases,fibrinolysin.
other virulence factors
slime layer production ,capsule formation and cell wall formation.
clinical manifestations
staphylococcal scalded skin syndrome,Toxic shock syndrome,staphylococcal food poisoning and cutaneous infection.
SSSS
characterized byperioral erythema and conjuctivitis,cutaneous blisters form and disquamation of the epithelium occurs .The blisters contain clear fluid with no organism.It is mediated by exfoliative toxin .The organism remains localized.Seen commonly in children and infants under 4.
Toxic shock syndrome
caused by toxix shock syndromr toxin -1.mostly affects menstruating women.characteristics are;low pressure,fever,extensive skin rash ,desquamation including soles and palms.
staphylococcal food poisoning
mediated by enterotoxins that acts as neurotoxins which stimulate vomiting.The enterotoxin is heat stable.symptoms;abdominal pain,cramps,diarrhea,vomiting and nausea.
cutenous infection
impetigo,folliculitis,furuncles,carbuncles,bacterimea,endocarditis,osteomyelitis,septic arthritis
impetigo
A superficial infection that affects kids on the face and limbs.charactrized by the presence of pustules.This pustules can break and peel away like a localized form of sss.contagious and occurs in areas with pooe hygiene.
folliculitis
superficial inflammation of hair follicles. raised domed pustules around hair follicles.
furuncles/boils
results when inflammation of a single hair follicle progresses into large red extremly tender abscess.very painful nodules with underlying collection of dead and necrotic tissue.often occur in clusters on parts of the body such as buttocks,back of neck where skin rubs against other skin or clothing
carbuncles
furuncles extending to the deeper subcutaneous tissue.created by aggregation and interconnection of a cluster of furuncles.associated with fever and chills .Found in areas of thick tough skin.They can give rise to systemic disease
Bacterimia
presence of viable bactetia in blood.
endocarditis
caused by bacteremia and affects the right side of the heart.Associated with colonization of the hearts linings ,cardiac abnormalities and rapid destruction of the valves.
osteomyelitis
infection of the bone
lab diagnosis
examination of abscess material under a microscope.Gram stsining .Culturing on sheep or rabbit blood agar.it will form white golden colonies on blood
STREPTOCOCCUS
G+ cocci ,non motile , non sporing and capsulated .capsules contain hyaluronic acid.Form part of normal flora.
streptococcus pyogenes
inhabits the throat,pharynx and skin
virulene factors-cellular components
C-carbohydrates -protect against lysozymes.Teichoic acid -adherence .M-protein-resistance to phagocytosis and adherence to epithelial cells in the pharynx.Hyaluronic acid -antiphagocytic
Extracellular enzymes
streptokinase-prevents formation of fibrin barrier,by activating a host blood factor that dissolves clots.DNase -hydrolyze nucleic acids.Hyaluronidase-spreading factor.Breaks down hyaluronic acid located between tissues allowing for penetration and spread of bacteria into tissues.
extracellular toxins
erythrogenic toxin-responsible for immunosupression cytotoxicity.Streptolysin O&S-destroy membranes of erythrocytes .
pathogenesis
streptococcal sore throat-pharyngitis.Skin infections-impetigo,erysipelas.Systemic infection-scarlet fever,rheumatic fever and glomerulonephritis
pharyngitis
spreads by saliva droplets and nasal secretions .It multiplies in the tonsils causing redness,edema and painful swallowing.Strep stimulates an inflammatory response and lysis of RBCs and WBCs.exudate containing cells and fluids is released ftom blood vessels and deposited in the sorrounding tissue.
cellulitis/impetigo
burning itching papules that break and form a highly contageous yellow crust. Impetigo occurs in epidemics among school going children.also caused by s.aureus.
Erysipelas
invasive form of skin infection. The pathogen enters through a small wound or incision on the face or extremities and spreads to the dermis and subcutaneous tissues. early symptoms are edema amd redness of the skin near portal of entry.fever and chills . The lesion begins to spread outward producing a slightly elavated edge that is noticeably red ,hot and vescular.
post streptococcal diseases
rheumatic fever ,glomerulonephritis.
pathogenesis
mechanism of infection and mechanism by which disease develops.
infection
invasion of the host by microorganisms,which then multiply in close association with the host tissues.
disease
morbid process that does not necessarily involve infection
two types of pathogens
primary and secondary pathogens
virulence
degree of pathogenicity.Determined by 3 xtics;invasiveness,infectivity and pathogenic potential
gram positive cocci
staph,strep,pneumococci,enterococci.
gramp positive rods
bacilli,clostridia,corynebacteria,listeria and actinomyces.
gram negative
enterobactericeae-E.coli,klebsiella,salmonella,shigella. pseudomonas,bacteroids,legionella,vibrios,campylobacter,neisseria and hemophilus
miscelleneous
helicobacter,mycobacteria,treponemes,mycoplasma,rickettsia and chlamydia
pathogenesis of staph
Depending on the level of invasion,disease can range from localized to systemic. A local staphylococcal infection presents as an abscess-an inflamed fibrous lesion enclosing a core of pus. Toxigenic disease can present as toxemia due to production of toxins in the body or food intoxication or ingestion of preformed toxin in food. s.aureus produces disease by either production of toxins or direct invasion.It is an opportunistic pathogen causing infection on skin and mucous membrane.
scarlet fever
Results from a throat infection with a strain of S.pyogenes carrying a prophage that codes for pyrogenic or erythrogenic toxin or a rash inducing toxin that causes shedding of skin. It is spread by inhalation on infective respiratory droplets. systemic spread of this toxic gives rise to high fever and a bright red diffuse rash over the face ,trunk and tongue. The rash and fever disappears accompanied by desquamation of the epidermis.
rheumatic fever
caused by group A streptococci. Caused by inflammatory changes of the heart valves ,joints,vessels,subcutaneous tissues and CNS. symptoms;painful athritis,nodukes under the skin and fever.
glomerulonephritis
an inflammatory disease of the renal glomeruli . Damage results from the deposition of antigen antibody complexes in involving the streptococcal M protein . Arises from type III hypersensitivity reactions. They cause destruction of glomerular membrane allowing proteins and blood to leak into urine.
