microbiology Flashcards
polyarticular septic arthritis suggests which pathogen?
GBS
what location of septic arthritis suggests IVDU?
sternoclavicular joint
what bug is most responsible by far for septic arthritis? in which conditions is it seen even more?
staph aureus
RA and IVDU
what is the second most common cause of septic arthritis? what conditions are risk factors?
GBS
neonates, DM, malignancies
pseudomonas suggests what etiology of septic arthritis?
iatrogenic or IVDU
what bug is a cause of septic arthritis in young adults and those with complement deficiency, also SLE?
Neisseria
what bugs can cause septic arthritis in SLE? sickle cell?
salmonella: SLE and sickle cell
neisseria: SLE
what bug causes septic arthritis following dog or cat bite?
Pasteurella multocida
what is the etiology of septic arthritis due to brucella?
unpasteurized milk
what manifests with the clinical triad of 1. dermatitis 2. tenosynovitis 3. migratory polyarthritis
disseminated gonococcal infection: causes gonococcal arthritis
what groups does gonococcal arthritis occur in?
4x more in women
young and sexually active or IVDU
what does blood culture show in gonococcal arthritis?
occult bacteremia: won’t be able to culture
what is the most common cause of osteomyelitis? 2nd most common
- staph. aureus
2. staph. epidermidis
what bug causes osteomyelitis in someone who stepped on a nail?
pseudomonas
what are 2 most common and 2 other causes of vertebral osteomyelitis and spondyodiskitis?
staph aureus and staph epidermidis
MTB and brucella
what are 2 most common bugs responsible for osteomyelitis in children? what can also cause it in neonates?
- staph aureus
- strep pneumo
neonates: GBS, E. coli
what bug, besides staph aureus, causes osteomyelitis in sickle cell? how?
salmonella
-gut infarcts release salmonella and auto-splenectomy so can’t clear it
what unusual locations of osteomyelitis suggest IVDU? what two bugs are responsible beside staph aureus?
sternoclavicular, sternochondral joint, pubic symphysis
pseudomonas and candida
what bug causes needle-licker OM?
eikenella corrodens
what are the two most common causes of pyomyositis?
- staph aureus by far (60-70%)
2. GAS (1-5%)
what bug causes gas gangrene? how is it cultured? appearance?
Clostridia perfringens
anaerobic culture with sugar fermentation and acid production
large box-car gram-positive rods
what is the pathogenesis of gas gangrene?
alpha toxin is liecithinase that damages cell membranes, causes hemolysis, produces gas in tissues
describe the genome of: alphaherpesviruses HPV poxviridae parvovirus B19 measles mumps rubella coxsackievirus/enterovirus HHV-6
alphaherpesviruses: linear, dsDNA HPV: circular dsDNA, very small poxviridae: linear, dsDNA parvo: -ssDNA, tiniest genome measles/mumps: (paramxyo) -ssRNA rubella: (toga) +ssRNA coxsackie/entero: +ssRNA HHV-6: dsDNA
what are the three stages of lytic cycle in herpes viruses?
immediate early: proteins contained in virus on infection lead to expression of other herpes genes by redirecting use of host RNA polymerase
early: replication of virus genome in nucleus of host cell
late: structural proteins synthesized in cytoplasm of host cell
what is the neurotropism of HSV-1, HSV-2 and VZV?
HSV1: trigeminal nerve
HSV2: lumbar and sacral nerves
VZV: dorsal root ganglia
what does LAT gene do in HSV-1?
produces microRNAs in latency to prevent apoptosis, repress viral gene expression, may inhibit CD8s
what test can be used to diagnose alphaherpesviruses? what does it show?
Tzanck smear: shows multinucleated cells
how do HPV warts turn into malignant tumors?
occasionally, viral genome is integrated into host genome
-if E2 is split, high level expression of E6/7
E6: causes degradation of p53
E7: inhibits Rb
what does the Gardasil vaccine contain?
L1 capsid protein from each carcinogenic strain of HPV
what is unique about the replication of pox viruses?
encode all of own proteins so replicate in cytoplasm
-unique for DNA viruses
how is molluscum contagiosum diagnosed in lab?
presence of cytoplasmic inclusions in keratinocytes
how did the smallpox vaccine work?
live vaccinia viruses (lab strain of pox virus)
what disease does parvovirus B19 cause in children? describe it
fifth disease of erythema infectiosum
slapped cheek and erythematous reticular rash
what does parvovirus B19 cause in adults?
less rash and more polyarthritis, flu-like syndrome
what cells do parvovirus B19 replicated in? what are two possible consequences?
precursor RBCs
aplastic crisis in sickle cell
chronic anemia in immunocompromised
what two viral exanthems can cause neonatal infection? what do they do to the fetus?
parvovirus: fatal anemia or hydrops fatalis
rubella: congenital defects, blueberry rash
what causes the symptoms of parvovirus infection?
immune response: cell-mediated causes rash, cytokines cause fever prodrome
what is the clinical diagnosis definition of measles?
- generalized rash lasting >3 days
- high fever >38..3C (101F)
- three C’s: cough, coryza, conjunctivitis
what is pathognomonic for measles? what causes the rash in measles?
Koplik spots
cell-mediated immune response
what type of vaccine is the measles one?
live attenuated
what are two potentially serious complications of measles?
immune suppression for about a month
encephalitis/encephalomyelitis
what is the first sign of mumps?
parotid gland swelling and inflammation
what are two potentially serious complications of mumps?
aseptic meningitis
gonadal involvement in post-pubertal men can cause sterility if bilateral
which morbilliform viral rash begins on face and spreads and is accompanied by low fever, LAD, conjunctivitis, sore throat?
rubella
what exanthem disease do coxsackievirus and enterovirus cause?
hand, foot and mouth disease
- oral ulcerative lesions on tonsils, uvula
- vascular lesions on hands and feet
what does HHV-6 cause and who does it infect?
infants, children
what causes Rocky Mountain Spotted Fever? how does the rash present? How can you diagnose it?
Rickettsia rickettsii
petechial rash starts on ankles/wrists and spreads
Weil-Felix test: antibody cross-reacts with Proteus antigens
what causes Epidemic Typhus? how does the rash present? how is it transmitted?
Rickettsia prowazekii
petechial rash spreads from trunk to extremities (inverse of RMSF)
fleas/lice: virus in feces infects the bites
what causes Endemic Typhus? How does it present? reservoir and transmission?
Rickettsia typhus
milder version of epidemic typhus
small mammals, fleas
what can be diagnosed by morulae in monocytes/granuloctyes? what type of disease does it cause?
Ehrlichia chaffeensis and Anaplasma phagocytophilia
southern tick-borne diseases
what is Anaplasmosis sometimes called? what are possible presentations?
Rocky Mountain Spotless Fever
- CNS involvement
- difficulty breathing, renal failure, hemorrhage
Coxiella: most common location in US, reservoir, modes of transmission, possible complications
- western agricultural states
- sheep, cattle, goats
- contaminated dairy of animal viscera, ticks, aerosolized spore-like form
- pneumonic disease, liver or heart involvement causes chronic infection
which spirochete may be visualized on blood smear?
Borrelia of relapsing fever: hermsii and recurrentis
what causes Lyme disease? how can it be visualized? how is it diagnosed?
Borrelia burgdorferi
darkfield microscopy, Giemsa or silver stain
ELISA confirmed with Western Blot
describe the 3 stages of Lyme disease
- erythema migrans, maybe flu/arthralgias
- heart block/myocarditis, meningitis, facial/Bell’s palsies
- progressive CNS disease, arthritis
what species cause relapsing fever? where is it endemic to? reservoir and transmission? describe the rash
Borrelia hermsii and recurrentis
western US
rodents/small animals; ticks and body lice
rash is usually not present
how can relapsing fever be diagnosed?
visualization on blood smear of spirochetes
convalescent serum during active symptoms
what sort of bacteria is Leptospira interrogans? primary reservoir and transmission?
spirochete
dogs (also rodents, livestock)
water or soil contaminated from animal urine
what is the clinical presentation of Leptospira infection? what is a characteristic finding?
two stages separated by quiescence:
- flu-like, conjunctivitis
- organ damage: liver, kidney, lung hemorrhage, meningitis
- very high bilirubin is characteristic
what causes Cat Scratch Fever? how does it present? in immunocompromised? how can it be diagnosed?
Batonella heneslae
fever with LAD, papule at site of infection, long course
immunocompromised: bacillary angiomas
Warthin-Starry silver stain
what is the reservoir for anthrax? how does cutaneous infection present?
cattle, sheep
painless lesion that becomes blistered with necrotic center
-can have dizziness, palpitations, sepsis
what is the reservoir for Burkholderia? what strange way may it be diagnosed?
soil, water and livestock
resistant to gentamicin and colistin
where is francisella found? how is it transmitted? what does the cutaneous infection look like? what is the virulence factor? how can it be diagnosed?
Arkansas, Missouri, Martha’s Vineyard
fleas, lice, ticks; contaminated animals, blood or water
ulceroglandular with bubo-like LAD and flu symptoms
agglutination testing
where does plague occur in US and why? what causes “black death”? how can the safety pin be visualized?
west: reservoir is prairie dogs
endotoxin-related effects cause DIC and cutaneous hemorrhages
Giemsa or Wayson stains
what are three virulence factors of plague?
- anti-phagocytic capsule
- LPS endotoxin
- Yops: injected into host cells, inhibit phagocytosis and cytokine production
