Bacterial, Viral, Fungal Infections II Flashcards
what is a furuncle
boils develop in hair follicles
-infections at base of eyelashes gives rise to styes
carbuncles are associated with what conditions
chronic granulomatous disease and diabetes
what is chronic granulomatous disease
genetic disorder where immune cells are unable to kill some types of bacteria/fungi
-disorder can lead to chronic/recurrent infections which is discovered in childhood
large fluid filled pustules
bulla
what is bullous impetigo caused by
staph aureus that produces exfolatin
in bullous impetigo, what does the large blisters on the superficial layer of the skin contain
many staph
common location of carbuncle
nape of the neck
what is chronic furunculosis and what causes it
chronic boils/furuncles
due to delayed hypersensitivity of staph products (reason for most of the inflammation and necrosis)
mode of transmission for rickettsii
insect bite
pathogenesis of ricketsii
infects vascular endothelium which causes RBC leakage from breaks in vessels –> rash and petechial lesion
insect in rickettsii ricketsiia aka rocky mountain fever and distribution of the rash
tick
centripetal: starts at wrist and goes to trunk then back out to palms and sole of feet
louse borne typhus fever is caused by what
rickettsia prowazeki
how is rickettsia prowazekii transmitted
body louse/lice
how does the louse get and transmit typhus fever
it gets it from an infected person then once it bites someone else and defecates at site, it will die
typhus fever is commonly seen when
disease of war and upheaval – epidemics in refugee
how long does it take the rash to show up in typhus fever and describe the rash
10 days
it spares the palms of the hand and the soles of the feet – centrifugal
complication of typhus fever
gangrene because of compromised circulation due to infection induced vascular injury
how does one diagnose rickettsial disease
- PCR is best (atypical bacteria)
- enzyme immuno assays for antibody production
- culture is difficult and hazardous (requires tissue culture or eggs)
transmission of primary classic lyme disease
tick bite - spirochete enters the skin
what happens at the bite site of lyme disease
3-30 days later:
• Erythema chronicum migrans (ECM). –Slowly expanding red ring.
–Biopsy of leading edge contains organism.
–Disappears within weeks.
• Constitutional symptoms for months.
–Fever, muscle and joint pains.
–Meningeal irritation
what is borrelia burgdorferi
spirochete shaped organism that is found in low amounts in tissues
how to diagnose borrelia burgodorferi seen in lyme disease
EIA for antibody screen plus western blot for confirmation
PCR of joint fluid or biopsy of leading edge of new ECM rash
culture and stain are rarely productive
inflammation of subcutaneous fat: cellulitis –> what are the organisms
– Streptococcus pyogenes
– Staphylococcus aureus
– Pasteurella multocida
inflammation of fascia - fascitis –> what are the organisms
– Streptococcus pyogenes
– Polymicrobial
myonecrosis/gangrene in muscles –> what is the organism
Clostridium perfringens
presentation and microbiology of cellulitis
deeper dermis, subcutaneous tissue, fever, chills, bacteremia
beta hemolytic strep, s. aureus
presentation and microbiology of erysipelas
upper dermis, superficial lymphatics, fever, pain, lymphadenopathy, rapidly advancing edges of infection, often on face
beta hemolytic strep, rarely s. aureus, group B strep
big difference between staph and strep cellulitis
strep spread really fast
staph alternates between walling off and rapid extension of infection (so slow then fast then slow)
what is erysipelothrix rhusiopathiae
gram positive diphtheroid like rod found in animals, meat, and sea food
disease associated with erysipelothrix rhusiopathiae
erysipeloid which is a painful slowly spreading skin infection
transmission of erysipelothrix rhusiopathiae and commonly seen in whom
traumatic inoculation of the skin
commonly seen in fishermen, butchers, veterinarians
treatment of erysipeloid
penicillin and erythromycin
major cause of wound infections
staph aureus
sources of wound infections
patient’s own strain
nosocomial strains spread by health care workers practicing poor hygiene (no hand washing)
amount of organism needed to initiate s. aureus infection in wound infection
10^5 - 10^6
amount of organism needed to initiate s. aureus infection in wound infection if at site of a suture
only 10^2 organisms
what do coagulase negative staph lack
virulence factors of staph aureus
non beta hemolytic
grouped with normal flora
how have coagulase negative staph become opportunistic pathogens
– Indwelling plastic and metal devices in seriously ill patients.
– Immunosuppressed patients.
– Major surgery involving large areas
number one bacteria in CNS
staph epidermidis
what does staph epidermidis produce
extracellular polysaccharide slime and biofilm
what does staph epidermidis provide
adhesion to indwelling devices such a catheters, artificial heart valves, CSF shunts, hip replacements (because of the slime and biofilm)
s. epidermidis provides provides biofilm for organisms hence protecting them from what?
phagocytosis and antibiotics
yet they can still obtain nutrients
coagulase negative staph that causes infection similar to that of staph aureus minus the toxic shock syndrome
s. lugdunensis
what does s. lugdunensis cause
serious infections which include abscess formation
clinical significance of coagulase neg staph
- difficult to determine significance (few colonies are normal in superficial specimen)
- hence have to collect deep invasive samples to avoid superficial contaminants
when is coagulase neg staph considered significant
– Present in multiple blood cultures.
– Intracellular Gram-positive cocci are seen in Gram stain.
– Culture shows moderate to heavy numbers on culture plates from wound specimens
when is coagulase neg staph considered less significant
• Negative plates with pos. broth culture only indicates very low #’s of CNS
necrotizing fascitis is due to what bacteria
beta hemolytic group A strep
