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Clinical Diagnostics Lab Exam


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- bacterial colonies embedded in fibrin on heart valves

- SBE prophylaxis prior to dental procedures: amoxicillin 500mg, 4 po 1hr before
- Risk Factors
- immunosuppressed pt.
- invasive or surgical procedure
- intravascular devices
- widespread use of broad spectrum antibiotics that suppress NL flora
Bacteria that commonly cause Endocarditis
1. Viridans streptococci
2. enterococcus
3. Strep. bovis (Group D, non-enterococcus)
4. Cardiobacterium
5. Eikenella
6. Coagulase (-) staph.
Endocarditis: In IV drug abusers, the most common isolate is ______.
Staph aureus
Blood culture specimen collection
- 3 sets of aer/ana bottles
- 1/2 hr prior to expected onset of fever spike
- separate sites
- prior to admin. of antibiotics
- 5-10mls per bottle
- continuous monitoring
CSF Infections
1. Meningitis
2. Encephalitis
3. Meningoencephalitis
- infx. w/in subarachnoid space
- inflammation of brain parenchyma (usually viral etiology)
- inflammation of meninges
CSF analysis
- lumbar puncture: tube #2 goes to micro, spun specimen and sediment plated
CSF analysis

a) bacterial etiology
b) viral etiology
c) mycobacterial or fungal etiology
a) PMNs, low glucose, high protein

b) lymphocytes, NL glucose, NL to mod. elevated protein

c) eosinophilia, low glucose, high protein
Additional CSF testing
- latex agglutination testing for antigen
- gram stain
- VDRL for Abs
CSF testing: VDRL for Abs against what organisms?
- Treponema pallidum (syphilis)
- Cryptococcal antigen
Prozone effect
- false negative due to a lot of organisms preset
NL flora of genital tract of females
- varies w/age depending on pH and estrogen concentration

- Staph., Cornyebacterium, Lactobacillus, Streptococci, Enterobacteriaceae, anaerobes
NL flora of genital tract of males
- Staph, Cornyebacterium, Mycobacterium smegmatis in uncircumcised males
Pathogens of GU tract
- vaginal Candiasis
- protozoan, Trichomonas vaginalis
- N.gonorrheae
- C.trachomatis
- M. hominis
- Peptococcus species
- Ureaplasma urealyticum
- Bacteroids
- H.influenzae
- Gardnerella vaginalis
- Strep. species
- viruses: HSV1 & 2
- Haemophilus ducreyi
Vaginal Candiasis is assoc. with:
- antibiotic therapy
- DM
- pregnancy
- immunosuppressed pt.
- corticosteroid use
Vaginal Candiasis presents:
- cottage cheese discharge, adheres to vaginal mucosa
- vulvar pruritis (may be exacerbated w/onset of menses and somewhat relieved at onset of menstrual flow)
Most common sx. of vaginal candiasis:
- vulvar pruritis
Vaginal candiasis: STD?
- usually NOT sexually transmitted
Vaginal candiasis: swab
- swab lateral and posterior fornices while avoiding cervical mucus with a pH of 7
Vaginal candiasis: lab
- wet mount or saline prep
- 10% KOH prep
- if inconclusive consider vaginal culture
-(+) culture does not mean Candida is responsible for vaginal sxs.
Vaginal candiasis: TX
- oral or topical azole prep (Diflucan 150mg, single dosing, Gyne-Lotrimin, Monistat, Terazole)
Caution about vaginal preps
- oil based and may weaken latex condoms/diaphragms
Most common cause of inc'd malodorous (fishy) discharge
- Bacterial vaginitis
Bacterial vaginitis
- fishy smelling discharge
- pH >4.5
- vaginal irritation and pain are UNCOMMON
Bacterial vaginitis: pathogen
- no single pathogen is responsible
- usually due to overgrowth of anaerobes replacing NL lactobacillus
- Garderella vaginalis, Mycoplasma hominis, Bacteriodes
Bacterial vaginitis: labs
- positive whiff test with 10% KOH
- clues cells on wet mount
- culture not useful as Gardnerella vaginalis can be isoloted from 1/2 of NL women
Bacterial vaginitis: Tx
- metroniazole (Flagyl) 500mg PO BID x 7 days
- contraindicated in pregnancy
- avoid alcohol during tx and for 24 hours after tx due to disulfiram-like antabuse effect
- alternate tx: metroniazole gel (Metrogel vaginal) 0.75% one applicator (5g) intravaginially BID x 5 days
- Clindimycin
Clues cells
- epithelial cells with inclusive bacteria
Disulfiram-like antabuse effect
- nausea, flushing, metallic taste
Trichomonas vaginitis
- protozoan Trichomonas vaginalis
Trichomonas vaginitis: sxs
- some are asymptomatic
- copious amts. of malodorous FROTHY YELLOW-GREEN DISCHARGE
- dyspareunia
- worsening following menses
- STRAWBERRY CERVIX due to petechiae
- majority of men are asymptomatic
Trichomonas vaginitis: dx
- observing motile trichomonads and PMNs on wet mount
Trichomonas vaginitis: Tx
- metroniazole (Flagyl) 2gm single dosing or 500mg BID x 7 days
- contraindicated in first trimester of pregnancy but may be considered after w/2gm single dose
- Polymicrobial: N.gonorrheae, C.trachomatis, M.hominis, Peptococcus species, U.urealyticum, Bacteroids,H.influenzae, Gardnerella vaginalis, Strep species, viruses
PID: risk factors
- age <25
- multiple sex partners
- IUDs
- recent invasive gyn procedure
- smoking
- vaginal douches
- parturition
PID: clinical dx
- BL lower abd. pain
- change in discharges
- irreg. bleeding
- dysuria, fever
- adnexal tenderness/swelling
- cervical motion tenderness aka "CHANDELIER SIGN"
PID: Labs
- gram stain
- urine pregnancy (ectopic)
- CBC (appendicitis)
- syphilis serology
- HIV testing
PID: gold standard for confirming dx
- laparoscopy (invasive)
Most prevalent STD in U.S.
- gonorrhea
Neisseria gonorrheae
- gram (-) diplococci
- incubation: 2-5 days
Gonorrhea is characterized by:
- acute urethritis in men
- cervicitis in women
- Skene’s & Bartholin glands commonly infected
Gonorrhea: sequellae
- salpingitis
- scarring of fallopian tubes
- (PID)
- can lead to sterility
Gonorrhea: Dx
- gram stain PMNs & intracellular gram (-) diplococci
- presumptive dx in men, not women-have NL Neisseria in vaginal area
Gonorrhea: culture required growth on _____
- Thayer-Martin Plate
Gonorrhea: Tx
- all sexual partners w/in past 30 days
- no intercourse until cured
- treat newborns w/anbx drops to prevent gonococcal ophthalmia
- Rochephin 125 mg IM single dose or Cipro 500 mg orally
Syphilis: pathogen
- Treponema pallidum
("great masquerader")
a) hosts
b) higher incidence
a) humans are the only host
b) southern U.S., blacks, hispanics
Syphilis: modes of transmission
- skin
- mucus membranes
- body fluids & secretions
- transplacentally
Stages of Syphilis
- primary
- secondary
- latent
- tertiary
Syphilis: primary stage
- painless chancre
- appears 2-6 wks after exposure
- at site of exposure, genital area, lip, tongue, buccal mucosa
Syphilis: secondary stage
- 2-6 months later
- skin lesions
- palms and soles
- highly contagious as lesion borders are loaded w/ spirochetes
- sore throat,fever,chills, H/A,anorexia,weight loss, generalized alopecia, lymphadenopathy
Syphilis: latent stage
- pt. is asymptomatic but diagnostic testing is (+)
- early latent: up to 1 year
- late latent: after 1 year w/o sxs
Syphilis: tertiary stage
- chronic inflammatory dz, can affect any organ
- gummas (thought to result from delayed hypersensitivity rxx)
Granuloma Inguinale
- aka Donovanosis
- Calyminatobacterium granulomatis (gnr)
- “Donovan Body” in cytoplasm of mononuclear cells.
Granuloma Inguinale: sns/sxs
- painless granulomatous ulcer at inoculation site
- lymphadenopathy is uncommon
Granuloma Inguinale: labs
- punch bx
- Wright/Giemsa stain
Granuloma Inguinale: Tx
- doxycycline 100mg BID
- or Bactrim
Lymphogranuloma Venereum
- Chlamydia trachomatis
Chlamydia trachomatis
- uncommon in US
- prevalent in tropical areas
- 2 stages
2 stages of C.trachomatis
1. painless papule that ulcerates
2. tender, U/L inguinal adenopathy, BUBO formation
BUBO formation
- accumulation of tender lypmh nodes
- may rupture
- fistula may form
C.trachomatis: labs
- Ab/complement fixation test: >1:32 indicative of active dz
- culture of BUBO aspirate
C.trachomatis: Tx
- doxycycline for 21 days
- treat any sexual partners w/in past 30 days
Chancroid (Haemophilus ducreyi)
- painful genital ulcer
- 1-14 days of incubation
- tropics, subtropics
Chancroid (H.ducreyi): labs
- gram stain
- culture ulcer edge or inguinal node aspirates
Chancroid (H.ducreyi): Tx
- azithromycin
- erythromycin
- ceftriaxone
HSV 1 and HSV 2
- ds DNA virus
- direct contact w/mucus membrane
- 2-20 day incubation
HSV: what happens to virus after acute episode?
- virus migrates to sensory or autonomic ganglia
- becomes dormant
- may reactivate
HSV: sxs
- painful eruption of localized grouped vesicles on an erythematous base
- fever, malaise, H/A
HSV: initial eruption
- more severe and lasts longer than subsequent recurrences
Herpes Genitalis
- can occur anywhere on genitals
- on labia in females
HSV: definitive test
- viral culture
HSV: labs
- viral culture
- special transport media
- cross reactivity
- STD testing
- Tzanck smear
HSV: why are serological tests of limited value?
- >85% adults have Ab to HSV1
Tzanck smear
- scrape base of lesion with blade
- place on slide
- stain with Wright/Giemsa/toluidine blue
HSV: what is seen on Tzanck smear?
- multinucleated giant cells
- negative test does not disprove dx.
- specific only to herpes virus
- Acyclovir (Zovirax)
- Valtrex
- Famvir
HSV: cold sores
- treated for 3 days
- Abreva OTC: prevents virus from infecting new cells
HSV: suppressive therapy
- Zovirax for up to a year reduces frequency and severity of infxs.
- does not reduce viral shedding.
HSV: prevention
- HSV2 vaccines under clinical trial
- condom use
Chlamydia trachomatis invades only ____.
- columnar epithelium
GI: S.aureus
- S.aureus
- rapid onset
- 2-8hrs of N/V/D, H/A, cramps
GI: Clostridium botulinum
- anaerobic, spore-forming
- gram (+) bacillus
- one of most powerful toxins known
GI: C.botulinum
a) incubation
b) symptoms
- incubation: 12-36 hours
- sxs: N/V/D, dizzy, difficulty swallowing, double vision, nerve paralysis
GI: C.botulinum
a) dx
b) tx
a) toxin ID in serum or food source
b) antitoxin and airway maintenance
rice water stools
- cholera
Vibrio parahaemolyticus
- gram (-) bacillus
- contaminated shellfish, sushi, improperly cooked seafood
- incubation: 2-24 hours
- N/V/D, abd. pain
- tx: self-limiting
GI: Preformed Toxin
- S. aureus
- C. botulinum
GI: Enterotoxin
- Vibrio cholerae
- Vibrio parahaemolyticus
- Bacillus cereus
- Clostridium difficile
GI: spores may not be killed during cooking, rice/grain dishes
- Bacillus cereus
GI: B.cereus
- watery diarrhea, abd. pain, rectal spasm, nausea
- lasts about 24-48 hours
- tx: supportive
pseudomembranous colitis
- Clostridum difficile
causative agent of antibiotic-associated diarrhea
- Clostridium difficile
GI: C.difficile
- anaerobic, gpb
- spore forming
- part of NL flora
Antibiotics involved in C.difficile infx.
- any antibiotic can cause it
- ampicillin, clindamycin, cephalosporins are the most common causes
C.diff: sxs
- may be mild or...
- bloody diarrhea, abd. cramping, fever
- Latex agglutination
C.diff: tx
- discontinue antibiotics
- treat with Flagyl or vancomycin
- >2000 serotypes
- gnb (Enterobacteriaceae)
Most common species of Salmonella in the U.S.
- S. enteridis
- incubation 6-48 hours but may be delayed for 7-12 days
Salmonella reservoirs
- livestock, turtles, iguanas, snakes
- food sources: raw eggs, undercooked beef or poultry, cutting boards or contaminated utensils, food handler

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