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Micro Exam 3 2


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most common cause of ascending UTI
E. Coli
enterobacteria associated w/ urinary stones
proteus mirabelis (produces potent urease to produce ammonia and make urine alkaline)
gram + causes of UTI
staph saprophyticus, staph epidermis, and enterococcus
causes UTI in young sexually active women
staph saprophyticus
causes UTI in hospitalized pts
Staph. epidermis and Enterococcus
viral UTI common?
viral UTI causes?
human polyomavirus, adenovirus, hantavirus
How does humanpolyoma infect?
enters via respiratory tract and spreads to tubular epithel cells in kidneys and ureters. establishes latency
35% of healthy individs have infx with ____________ but it remains latent
fungal causes of UTI
candida and histoplasma capsulatum
parasitic causes of UTI
Trichomonas vaginalis, Schistosoma haematobium
which causes urethitis in males/vaginitis in females
T. vaginalis
which causes allergic response to worm’s egg leading to scarring in area where bladder/ureters meet and ureters get blocked- results in bladder inflammation
S. haematobium
mechanical factors that predispose to UTI
1. shorter female urethra
2. sexual intercourse
3. uncircumcised boys
obstructions to complete bladder emptying
1.residual urine
2. loss of neurologic control
3. vesicoureteral reflux
4. diabetes mellitus
5. catheterization
causes of loss of neurological control:
spina bifida, paraplegia, multiple sclerosis
who is vesicoureteral reflux common with
children w/ anatomic abnormalities of the urinary tract
diabetes mellitus may lead to...
where do most urinary tract pathogens originate
fecal flora
which can colonize/infect the urinary tract
aerobic and facultative species such as E. coli
what structural feature helps E. coli adhere to epithelium
what does E. coli produce that causes kidney damage
is healthy urinary tract resistant to bacterial colonization?
yes- eliminates microorganisms rapidly/efficiently
via pH, chemical content, and flushing mechanism
3 clinical features of acute lower UTIs (bladder infxs)
dysuria, urgency, frequency
urine sample shows:
cloudiness due to pyuria and bacteriuria, hematuria
what may result from an ascending infx?
acute bacterial prostatis
upper UTI spreads to
what is pyelonephritis
kidney infx
ranges from moderate diarrhea to severe lasting 20 days in immunocompromised
common cause of upper UTIs
what can repeated episodes lead to
loss of fx of renal tissue, and HTN
how is infx distinguished
quantitative culture methods
definition of bacteriuria
over 10^5 organisms/mL
T/F usually are several bacterial species
F- only one
do a significant proportion of lower UTI pt's have recurrent infxs?
yes- either by same organism or by different one
does upper or lower cause renal abcesses
methods of urine collection
1. sterile container by pt
2. "bag urine" for babies/infants
3. catheter- collected from tube with syringe and needle
Tx of UTI
antibiotics- ie augmentin
prevention of UTI
empty bladder often (esp after intercourse), prophylactic anti-biotic use, good catheter care
host factors that influence risk of acquiring an STD
genital lesions or ulcers, uncircumcised men, multiple infx
What causes syphilis
the spirochete Treponema pallidum
how does it enter body
minute abrasions on skin or mucous m'branes
why does transmission require close contact
b/c doesn't survive well out side body, sensitive to drying, heating, disinfectants
poor sanitation and personal hygiene
5 stages of syphilis pathogenesis?
1. initial contact 2. primary syphilis 3. secondary 4. latent 5. tertiary
what occurs w/ initial contact
2-10 wks: treponemes multiply at infx site, develop a primary painless chancre
1-3 months; treponemes proliferate, enlarged inguinal nodes and spontaneous healing
2-6 weeks: treponeme multiplication,flu-like illness, headache, fever, mucocutaneous rash and spontaneous healing, lesions in lymph nodes, liver, joints, muscles, skin and mucous m'branes
3-30 years: treponemes are dormant in liver or spleen, no sign of illness
re-awakening, multiplication, dissemination, and invasion of trepes; neurosyphilis (general paralysis), and cardiosyphilis (aortic lesions, heart failure; progressive and destructive
does T. pallidum respond to vigorous immune response
how does it evade recognition and elimination by the host
maintains a cell surface rich in lipid that is antigenically unreactive
when is congenital syphilis acquired
first 3 mos of pregnancy
results in:
1. serious infx--> intrauterine death
2. congenital abnormalities
3. silent infx (at 2 y.o)
antibacterial agents not helpful; polyvalent antitoxin recommmended
what causes gonorrhea
gram pos diplococcus Neisseria gonorrheae
eating sewage contaminated shellfish or mussels
does it survive outside the body?
no- sensitive to drying
men or women more?
4 special mechanisms of N. gonorrhea to allow mucosal attachment:
1. fimbriae (attachment and antigenic diversity
2. LPS (endotoxin activity)
3. IgA protease (destroys IgA1)
4. capsule (resists phagocytosis)
how do they infect?
invade non-ciliated epithelial cells that internalize the bacteria, allowing them to multiply in intracellular vacuoles protected from phagos and Abs
how does it damage host
by inflammatory response elicited by organism
sn/sx in males
-complications rare
sn/sx in females
discharge- no pain, assymptomatic therefore don't seek treatment
female complications of gonor:
PID, chronic pelvic pain, infertility
ophthalmia neonatorum:
gon in infants, characterized by sticky discharge
other parts infected by gon:
throat, rectum (purulent discharge)
Cause of chlamydial infxs:
Chlamydia trachomatis serotypes D-K
2 forms:
elementary body (EB):extracellular survival

reticulate body (RB): intracellular multiplication
how does it invade/infect?
-enter host thru small mucosal abrasions
-bind specific receptors on host and enter by endocytosis
-lysosome fusion is inhibited and EB begins development
-after 9-10 hrs become active RBs
-new EBs produced
pathogenesis in men:
urethritis, epidymitis, proctitis, conjunctivitis
pathogenesis in women:
urethritis, cervicitis, salpingitis, conjunctivitis
causes of inguinal lymphadenopathy:
genital infxs, LGV, chancroid, donovanosis
cause of LGV:
C. trachomatis serotypes L1, L2, and L3
pathogenesis of LGV:
-after 1-4 wks primary lesion develops at site of inoculation
-fever/headache accompany
-lesion heals rapidly and draining lymph nodes are infected causing inguinal buboes
proctitis, fever, hepatitis, pneumonitis, meningo-encephalitis
spiramycin (immunocompromised only)
cause of chancroid (soft chancre):
H. ducreyi
-assymptomatic infxs (mild)
-self-limiting diarrhea 7-10 days
-immunocompromised may develop chronic infx
cause of donovanosis:
Calymmatobacterium granulomatis
which is most common form of genital ulcers in africa and asia
which is common in caribbean, new guinea, india, and central australia
What causes mycoplasmas and non-gonococcal urethritis?
mycoplasma hominis and ureaplasma urealyticum
where do they colonize?
genital tracts of healthy sexually active people
what are they also associated with
PID, postabortal and postpartum fevers
what are other causes of vaginitis and urethritis
candida albicans, trichomonas vaginalis, gardnerella vaginalis
characteristics of candida
-irritant vaginitis
-cheesy discharge
-UTI with it maybe
chars of trichomonas infx
-protozoan parasite inhabits vagina/urethra
-transmit during sex
-women: copious foul-smelling discharge, increased pH with actively motile trophozoites
-men: assymptomatic
what causes bacterial vaginosis
gardnerella vaginalis plus anaerobic infx of bacteroides that disrupt normal acidity of vagina
sx in women:
-excessive fish-odored discharge
-pH >4.5
-clue cells (vaginal epithelial cells coated w/ bacteria)
cause of genital herpes
when is primary lesion seen
3-7 days after infx
healing up to 2 weeks, but virus travels up sensory nerve and establishes latent infx in dorsal root ganglion neurons where it can reactivate and cause a recurrent lesion
spread from mom to infant?
yes, during delivery and can give rise to disseminated herpes or encephalitis
cause of genital warts
HPV- papillomavirus 6,11,12,16,18,and 31
where/when do warts appear
on penis, vulva, and perianal regions after 1-6 mos incubation
cervical lesion description:
a flat area of dysplasia visible by colposcopy as a white plaque after local application of 5% acetic acid
which are associated with cervical cancer
16 and 18
HIV infects which cells
TH, monocytes and dendritics
-clings tight to hairs, takes up to 10 blood feedings/day causing itching
-eggs attached to hairs, lice are visible at base of hair
-infestation is common
mechanisms of immunosuppression:
1. Th cells are directly killed by virus
2. Th cells undergo apoptosis
3. Th cells are attacked by Tc cells
4. T cell replenishment is impaired by thymus/lymph node damage and stem cell infx
5. defects in antigen presentation (infx of dendritics)
6. antigenic variation in hypervariable region of gp120
how does viral invasion of CNS occur
independently of AIDS
which are the infected cells in CNS
microglia or infiltrating macrophages which express CD4
this is seen in about 21% of homosexual/bisexual males and is associated with human herpes virus 8 (HHV8)
kaposis sarcoma
what is a major source of transmitted virus
peripheral blood mononuclear cells
what are sn of initial infx
mild mononucleosis type illness including fever and malaise
are antibodies detectable right away
no- may take many months; also many mos for t-cells to form
what happens to viral replication after initial infx
it's reduced and individual remains well
sn/sx in later years
weight loss, fever, persistent lymphadenopathy, oral candidiasis, diarrhea, ARC-AIDS related complex
what occurs with ARC
-less than 10% may be well
-may develop AIDS (opportunistic infxs_
-may develop subacute encephalitis and dementia
AIDS dementia=
opportunistic CNS infxs like HSV, CMV, and toxoplasmosis
lab tests for HIV
-western blot, radioimmunoassay, or immunofluorescence testing to confirm
odds of getting HIV after needle stick
what types of HIV vaccinations are being developed
various subunit envelope glycoproteins and a whole virus vaccine
whats the problem?
a vaccine that will induce abs against gp120 may combine w/ the virus w/o neutralizing then attaches to the Fc receptors on monocytes and the whole complex is ingested and monocyte is now infected
cause of pubic or crab lice
phthirus pubis
cause of genital scabies
Sarcoptes scabei
whats the most common outcome of GI tract infxs
nausea, vomiting, diarrhea, abdominal discomfort
abnormal fecal discharge- frequent fluid stool; disease of sm intestine
inflammatory disorder of GI tract associated w/ blood and pus in feces; accompanied by fever, pain, abdominal cramps; disease of lg intestine
inflammation involving mucosa of both small and large intestine
Bacterial causes of diarrhea:
E. coli, Salmonella, campylobacter jejuni, helicobacter pylori, vibrio cholerae, shigella dysenteriae, shigella sonei, vibrio parahemolyticus, yersinia enterolytica, c. perfringens, b. cereus, staph aureus, c. botulism
What are the 4 types of E. coli:
1. Enterotoxigenic (ETEC)
2. Enteroinvasive (EIEC)
3. Enterohemoerrhagic (EHEC)
4. Enteropathogenic (EPEC)
which is the most imp bacterial cause of diarrhea in children in developing countries and the most common cause of travelers diarrhea
most important in developed countries but outbreaks an sporadic cases occur worldwide:
important cause of diarrhea in areas of poor hygiene, usually food borne infxs:
spread via water contaminated by human or animal sewage:
causes sporadic cases of infx in babies and young children:
caused by verotoxin-producing serotype 0157 that has direct affect on intestinal epithelium:
produces powerful enterotoxins (LT and ST):
which of these toxins is heat labile
heat stable
has a mechanism of adhesion to enterocytes that appears to destroy microvilli
caused by food and unpasteurized milk:
chlorination and water filtration
what is the most common case of food-associated diarrhea in developed countries
salmonella and e. coli are both:
salmonella transmission:
animal resevoir- transmitted via contaminated poultry and dairy
frequent waterborne transmission?
where do they invade?
epithelial cells of terminal portion of small intestine
which species are responsible
s. enteritidis, s. cholera suis
which bacteria are S-shaped curved rods
how acquired?
via contaminated milk, poultry, H20
which bacteria is associated with over 90% of duodenal ulcers and 70-80% of gastric ulcers
helicobacter pylori
what does it produce that helps it survive acid environments
acute infx of GI tract caused by comma-shaped gram-negative bacteria
vibrio cholerae
reservoir and spread?
-a free living inhabitant of fresh water
-assymptomatic humans major resevoir
-spread via contaminated food (fresh water shellfish)
which condition is also known as bacillary dissentery?
its most severe form is characterized by:
-invasion of the mucosa of lg intestine
-inflammation of intestines
-blood/pus in diarrhea
-lower abdomen cramps
which species causes mild infxs?
shigella sonnei
shigella dysenteriae
a halophilic organism that contaminates seafood and fish; causes diarrhea if eaten uncooked:
Vibrio parahemolyticus
primarily a pediatric disease:
rice water stool:
causes infx in colder parts of the world:
Yersinia enterolytica
Tx includes omeprazole with amoxicillin and metronidazole:
H. pylori
enterotoxin producing type A strain and beta-toxin producing type C strains:
C. perfringens
which are more common and caused by spores that contaminate food?
A strains
characteristics of type c strains:
-acute necrotizing disease of sm. intestine
-more rare
-abdominal pain/diarrhea
thoroughly re-heating food
which disease has a long standing history of epidemics and pandemics
most common cause of diarrhea:
Campylobacter jejuni
clinically, which other bacteria is indistinguishable from c. jejuni?
caused by eating contaminated meat in people who are unaccustomed to high protein diets:
C. perfringens
lack sufficient intestinal trypsin to destroy the toxin
a heat stable enterotoxin thats resistant to degradation by enzymes in stomach/ sm. intestine:
staph aureus
spores and vegetative cells contaminate food:
B. cereus
2 forms of B. cereus:
1. ingestion of enterotoxin in food (rice and potatoes)
2. production of enterotoxin in gut
which causes rapid onset vomiting and which causes diarrhea?
vomiting= ingestion
diarrhea= production in gut
found in rabbits, pigs, sheep, cattle, horses, domestic pets:
yersinia enterolytica
an acute but self-limiting diarrhea that's resolved without tx:
diarrhea not a feature, vomiting occurs 3-6 hrs after consumption and recovery w/in 24 hrs:
staph aureus
spores are found widespread in the environment and can be isolated from soil samples, animals, and fish:
clostridium botulinum
is botulin an exotoxin or endotoxin?
how does it invade?
toxins are ingested in food (canned or reheated) or are produced in the gut after ingesting the organisms
produces 2 exotoxins that produce diarrhea and lead to colitis
3 types:
1. foodborne (toxin released in food, then ingested)
2. infant (organism ingested)
3. woulnd (organism implanted in wound)
Causes antibiotic associated diarrhea- broad spectrum antibios that inhibit normal flora:
Clostridium difficile
how is viral diarrhea distinguised from bacterial?
clinically indistinguishable
Rotavirus and Calcivirus
which includes the Norwalk virus?
Who does rotavirus mostly infect
children under 2
incubation period:
1-4 days
where does viral replication occur?
intestinal epithelial cells
Protozoa that cause diarrhea:
Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum
how does infx occur with E. histolytica
food/drink is contaminated with cysts that pass thru the stomach and excyst in the sm. intestine where they multiply
chars. of amebic dysentery:
mucus, pus and blood in stool
difference between amebic dysentery and bacillary dysentery:
amebic can perforate small intestine (peritonitis) and invade extra-intestinally when trophozoites spread via blood to the liver and form an abcess
Which protozoa causes infx when cysts are swallowed in contaminated drinking water from rivers/streams?
Giardia lamblia
animal host?
Pathogenesis of Cryptosporidium parvum:
-fecally contaminated material is ingested
-cysts release infective trophozoites which invade epithelial cells in sm. intestine
-parasite found in many animals
common infx in AIDS; diarrhea can be irreversible and life threatening
which protozoa is common in subtropical and tropical countries
Entamoeba histolytica
What are the most important intestinal worms?
soil transmitted nematodes
2 groups of them:
1. Ascaris lumbricoides/Trichuris trichiura
2. Anchylostoma duodenale/Necator americanus/Strongyloides stercoralis
large roundworm:
ascaris lumbridcoides
Trichuris trichiura
Necator americanus
which occur by swallowing infective eggs which hatch in intestine and release larvae
Ascaris and Trichuris
which can cause abdominal pain and nausea
what happens if there's large numbers of ascaris
can cause intestinal blockage and perforations of wall
What can Tricuris infx lead to?
chronic diarrhea and impaired nutrition/retarded growth (since children mostly affected)

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