Pages 1-11 Flashcards by Cal Schiller

Refrigerated samples?

Respiratory specimens
Urine
Stool
Sputum

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Room temp samples?

Body fluids
Blood culture
CSF

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Improper labeling 
Wrong specimen container
Leakage
Unsuitable specimen
Duplicate/repeat specimens
Sterile body fluids NOT sent STAT

Rejection criteria

exception to duplicate specimens would be blood cultures for endocarditis

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What skin rash can kids get from a pacifier…?

well lots of stuff really…

Maybe roseola? (high fever -> pink/rosey rash on trunk that then spreads to limbs,neck, face)

(consider herpes too maybe?)

(maybe OM?)

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MC acute endocarditis bacteria?

Staph

acute ABE occurs rapidly during a septicemic episode on healthy cardiac valves…very aggressive

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MC subacute endocarditis bacteria?

MC = Strep viridans

(can also be staph)

(subacute [gradual] infective endocarditis occurs in damaged cardiac valves, e.g., congenital defects, atherosclerosis, RF)

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PROSTHETIC valve endocarditits?

Staph epidermidis

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HACEK organisms for endocarditis?

Haemophilus
Aggregatibacter
Cardiobacterium
Eikenella
Kingella

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Significance of growth of the same organism in repeated cultures?

true positive

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Significance of growth of different organisms in different culture bottles?

Probable contamination, bowel spillage

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Significance of growth of normal skin flora?

likely contamination (staph, corynebacterium, bacillus, propionibacterium, etc)

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Significance of organismis such as strep viridans or enterococci?

Possible endocarditis (associated w/ low grade fevers)

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Blood culture protocol?

(for bacteremia, endocarditis, sepsis)

1 set = 1 aerobic/1 anaerobic bottle (10 mL/bottle)

Different sites/times, but no more than 4 total sets (so 8 bottles) within 24 hours

Peds get 1 bottle

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Antibiogram is an annual collection of C+S information collected in the institution. Provides a percentage of samples of a given organism that were sensitive to certain abx.

But… doesn’t provide?

Sensitivity based on site of infxn or location in hospital (ICU vs non-ICU)

Average MIC

Trend data

(also doesn’t provide concentration differences bw site of infxn and in vitro, inactivation/penetration at the site of infxn, levels of decline in vitro/in vivo)

Inaccurate due to small isolate number

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Aside from antibiogram, what are other considerations regarding abx for the patient?

Drug allergies, side effects, location of infxn (use least expensive, narrowest spectrum)

other susceptibility tests (disk diffusion, Broth/Agar dilution)

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In a primary immune response, which Ig binds first? Which is more specific?

IgM binds first, but IgG is more specific and lasts longer

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How does a secondary immune response differ from a a primary?

In a secondary response both IgM and IgG (memory) react simultaneously whereas in primary response the IgM arrives first.

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The titer corresponds to the highest dilution factor that still yields a positive reading. Comparing acute vs convalescent sera to one another, a ___ increase indicates an acute infection.

4-fold

However, when only an acute sample is submitted, a cutoff value is required and may vary by organism/geography

(example: primary: Day 5 - 1:4 titer, Day 12 - 1:64 titer, secondary - 1:256 titer or higher)

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What’s on an acute hepatitis panel?

IgM anti-HAV
IgM anti-HBc
HBsAg
anti-HCV

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Panel for acute Hep A would show?

anti-HAV IgM (+)

anti-HAV IgG (+)

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Panel for resolved Hep A would show?

anti-HAV IgM (-)

anti-HAV IgG (+)

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HBV panel displaying natural immunity?

HBsAg (-)
anti-HBc (+)
anti-HBs (+)

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HBV panel displaying vaccination?

HBsAg (-)
anti-HBc (-)
anti-HBs (+)

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HBV panel showing acute infxn?

HBsAg (+)
anti-HBc (+)
IgM anti-HBc (+)
anti-HBs (-)

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HBV panel showing chronic inxn?

HBsAg (+) anti-HBc (+) IgM anti-HBc (-) anti-HBs (-)

Lab criteria for Acute HBV?

Anti HBc IgM (+) or HBsAg (+) and HAV IgM (-)

IgM Anti HBc (-) AND HBsAg (+) or HBV DNA (+) or HBeAg (+) OR HBsAg (+) or HBV DNA (+) or HBeAg (+) twice at least 6 months apart

Either of those criteria would indicate chronic HBV infxn

Confirmed vs presumed case of HBV?

Confirmed case: meets lab criteria Presumed: Pt w/ single HBsAg (+) or HBV DNA (+) or HBeAg (+) and does not meet acute case definition

If HBeAg is (+), it is equivalent to a positive HBcAg marker and shows that the virus is replicating actively and the patient is infectious

However, presence of antiHBe means that replication activites have decreased and the patient is less infectious or not at all.

HBcAg is totally degraded in the serum and is not detectable, but a portion survives as HBeAg. Regarding HBcAg, what's measurable?

Anti-HBc are produced against HBcAg and are measurable

FIRST immune response against HBV infection, indicates active infection or flare against natural exposure. As immune response matures, this is replaced by IgG anti-HBc

IgM anti-HBc | note that anti-HBc is absent in those who have been vaccinated

Made in response to HBcAg, refers to presence of either IgG or IgM and does not discriminate. Presence indicates prior or current Hep B infection

total anti-HBc

indicates active infection (acute or chronic). Used as a quantitative test to monitor response to therapy, mainly in chronically infected patients. “Viral load”

HBV DNA

Most people who are infected develop chronic disease

HCV (rarely detected acutely)

Hep C has 6 genotypes. Most Americans have genotype 1. 2 and 3 respond better to therapy.

check

EIA assay (screening) to detect HC-Ab, confirmed by?

RIBA (recombinant immunoblot assay) or HCV RNA

CSF fluid (meningitis)... 1. Mostly PMNs (low glucose)? 2. Mostly lymphocytes (but normal glucose)? 3. Mostly lymphocytes (but low glucose)? 4. Mostly eosinophils?

1. bacterial 2. viral 3. fungal 4. parasitic

Spirochetes?

1. Treponema/syphilis (non-treponemal [titer] screening -> treponemal confirmation) 2. Borrelia burgdorferi/Lyme dz (serology IgM/IgG -> Western Blot confirmation)

Traveler's diarrhea?

E. coli (ETEC) -> cramps/watery diarrhea from food/water (culture usually not performed unless special patient) -------- Other traveler's diarrheas listed: Shigella, EIEC/EHEC/EPEC, Salmonella, Campy, Cholera

Urethritis... Frequently asymptomatic in females, but can present with dysuria, discharge or pelvic inflammatory disease.

Chlamydia trachomatis Send UA, Urine culture (if pyuria seen, but no bacteria, suspect Chlamydia) Chlamydia screening is now recommended for all females ≤ 25 years You should always also treat for chlamydia when treating for gonnorhea!

Most common cause of UTI in women?

E. coli most common cause (85%) | S. saprophyticus – young sexually active females

Frequent cause of UTI in men?

Enterobacteriaceae Ssx: urethritis (sterile culture: discharge, dysuria, frequency) Ssx: prostatitis (obstructed urine flow: “complicated UTI”)

Healthy adult women (>12), non-pregnant, no fever/N/G/flank pain Diagnosis: dipstick UA (no culture or lab test needed)

Uncomplicated UTI

Females w/ comorbid medical conditions, ALL males, indwelling foley catheters, urosepsis/hospitalization Diagnosis: UA, urine culture, further labs if appropriate

Complicated UTI

For neisseria gonorrhea labs, send?

Send UA, urine culture. Pelvic exam – send discharge samples for gram stain culture, culture, PCR

1. Recurring UTIs means? | 2. Relapse vs reinfection

1. Minimum 2 UTIs in 6 months or ≥ 3 in 1 year | 2. Relapse (same organism); reinfection (previous or second organism)

Most common pathogen for cystitis, prostatitis, | pyelonephritis?

``` – Escherichia coli –Staphylococcus saprophyticus –Proteus mirabilis –Klebsiella –Enterococcus ```

Most common pathogen for urethritis?

* Chlamydia trachomatis | * Neisseria Gonorrhea

Polymorphonuclear leukocytes without intracellular pathogens are characteristic of the mucopurulent discharge seen in men with?

nongonococcal urtheritis

Polymorphonuclear leukocytes with intracellular | pathogens are characteristic of the mucopurulent discharge seen in men with

* Intense perivaginal itching or burning * Thick white cottage cheese texture, odorless and adherent to the vaginal walls * Dysuria, normal vaginal pH (4.0-4.5

Candidiasis “yeast infection” (fungal)

* Slightly malodorous gray white discharge * Often asymptomatic, possible UTI * Increased vaginal pH > 4.5, positive amine test

Gardnerella vaginalis (bacterial vaginosis)

* Copious amounts of this frothy green/yellow/gray discharge, requires motile organism * Vaginal and exocervical epithelium are edematous and erythematous “strawberry cervix” * Vaginal soreness and dyspareunia, often asymptomatic * Increased vaginal pH (5.0-6.0)

Trichomoniasis vaginalis (parasitic)

increased vaginal pH suggests?

bacterial vaginosis or trichomoniasis

increased vaginal pH suggests?

bacterial vaginosis or trichomoniasis

Detects “jerky” motility of Trichomonas clue cells indicative of bacterial vaginosis fungal elements/budding yeast

saline wet prep

For vaginosis, a Gram stain identifies?

“clue cells” – epithelial cells covered by bacteria

Definitive diagnosis for treponema/syphilis?

Direct testing (skin lesions, placenta, umbilicus) Darkfield microscopy

Non-treponemal screening tests...

RPR VDRL(CSF) sensitive but not specific

Confirmatory treponema tests

FTA-ABS MHA-TP TP-PA (positive results for life)

screening test that looks for non-specific antibodies (cardiolipin) in that many indicate syphilis

RPR

Syphilis... Follow up positive screen with confirmation tests

MHA-TP (microhemagglutination T. pallidum) or FTA-ABS (fluorescent treponemal antibody) Pos RPR (1:16) + Neg confirm = False positive RPR Pos RPR (1:16) + Pos confirm = Active disease

Serologic monitoring is critically important during follow-up of treated syphilis

Suggested 3, 6, and 12-month intervals after treatment, compared with the pretreatment baseline. Important safety tip! Use the same testing assay (eg, RPR or VDRL) from the same lab for all follow-up examinations

Detection w/in 25 days (average) Within 3 months positive status 4th generation assays can detect within 12 days

HIV

Rapid antigen tests Home or POL ELISA based assay from patient's blood (military screening)

HIV screening

Western blot for confirmation of HIV status. Original specimen pos? Individual is notified of initial HIV+ status. Then?

Second specimen positive? -> individual notified of confirmed HIV + status Second specimen negative? request a 3rd specimen... 3rd specimen neg? Pt is neg. 3rd specimen pos? Pt notified of confirmed pos (all notifications are face to face)

HIV Positive result requires antibodies against ?

1 envelope protein (gp41, gp 120/gp 160) AND 1 core protein (p17, p24, p55) or 1 enzyme protein (p31, p51, p66

Follow up for HIV indeterminate status... Repeat WB + HIV viral load and repeat serology after?

Repeat serology after 3 months (EIA → WB) (if an at risk patient, they might still be seroconverting. If they're low-risk patient, they probbaly don't have the disease)

Bacterial agents of pharyngitis?

``` GAS M pneumoniae C pneumoniae N gonorrhea C diptheria A haemolyticum ``` (GAS, Gonorrhea definitely get throat swabs... assuming the rest would as well) (bacterial pharyngitis... look for furry tongue, whitish spots, swollen uvula)

Viral agents are more common causes of pharyngitis

Adenovirus (suspect this esp. with conjunctivitis) Coxsackie EBV (*can look like GAS and have exudate... look for atypical lymphocytes on blood smear) Herpes simplex CMV HIV

Age -younger kids Sudden onset Headache Vomiting High fever

Bacterial pharyngitis

Age – young adults Slow progression Coughing Rhinorrhea Low Grade fever Conjunctivitis

Viral pharyngitis

With what disease would you associate these with? History of congenital heart disease, IV drug use, recent dental work, or rheumatic fever Heart murmur Splinter hemorrhages, Roth spots, Osler’s nodes, clubbing, Janeway lesions.

infectious endocarditis

Blood culture with viridans strep or enterococci with low grade fever, think

endocarditis

Small bowel, secretoy diarrhea, usually self-limiting... what agents you think?

viral, Giardia, vibrio, E coli (ETEC)

Inflammatory, large bowel, positive fecal leukocyte, with mucus and PMNs Longer duration what agents you think?

Salmonella Shigella Campy

Bloody diarrhea, fecal leukocyte positive, Large bowel invovlement Longer duration w/ potentai complications what agents you think?

E coli O157:H7

Pediatric patients presents w/ non-bloody diarrhea, febrile or afebrile, think?

viral infection

Pediatric patient presents w/ bloody diarrhea (febrile or afebrile), think?

Bacterial infection | afebrile, think complication like intussusception, HUS, pseudomembranous colitis

Monocytes in fecal leukocytes?

typhoid fever

Released by neutrophils, indicator of intestinal inflammation (e.g., IBD, bacterial infections)

lactoferrin

Preferred test for suspected bacteria diarrhea... bloody or diarrhea > 3 days , hx of travel IDs specific pathogen

Stool culture

Big three for regular stool culture?

Salmonella, shigella, campy | extended stool culture - "little 3" - vibrio, yersinia, E coli

Fecal leukocyte Fecal fat Macroscopic pH

Fresh specimen (less than an hour)

Cary Blair medium (for culture/EIA) Formalin/PVA (for O+P)

delayed transport

* Investigate the cause of chronic diarrhea and loose, fatty, foul-smelling stools (steatorrhea). Indicator of impaired digestion and/or malabsorption * Excess fat is present in the stool and the person may experience prolonged diarrhea with stomach pain, cramps, bloating, gas and weight loss * Qualitative – suspension of stool onto a glass slide, adding a fat stain, and observing the number and size of fat globules that are present. Quantitative (if necessary) 24, 48, 72 hour collection – more precise

Fecal fat•

* To screen for leukocytes (WBCs) in the stool. Indicator of intestinal inflammation, suggestive of infection by stool pathogens such as Salmonella, Shigella, or Campylobacter which are able to invade tissues or produce toxins to cause damage. * Distinguish between inflammatory and non-inflammatory conditions. Typically reported in a semiquantitative manner (few, moderate, many)

Leukocytes (Lactoferrin)

• Large number of ___ in the stool may be seen in chronic bacillar dysentery, chronic ulcerative colitis, colonic abscess

WBCs

• _____ are seen in ulcerative colitis, invasive E coli diarrhea, Salmonella, Shigellosis

Neutrophils

• Some stool pathogens produce toxins which provide greater virulence to the invading organism and worsen symptoms for the patient. Rapid identification of toxin producing strains. Provision of optimal therapy for rapid recovery. Various methods depending on target pathogen: enzyme immunoassay, rapid antigen, cell culture (cytotoxin assay), bioassay

 Toxin assays

 Recommended for inpatients > 3 days or patients on continual antimicrobial therapy

o Toxin assay for C diff - toxin A and B, identifies toxigenic strains, determines therapy

 Recommended for ALL cases of bloody diarrhea

o Toxin assay Shiga toxin - found in Shigella species and shiga toxin producing E. coli serotypes (STEC) e.g. O157:H7

* 0-1 hour suggests ingestion of a chemical | * 1 to 6 hours suggests ingestion of a preformed toxin, such as?

Staphylococcus aureus or Bacillus cereus

• 8 to 16 hours, such as? • >16 hours various bacteria and viruses o May overlap with diarrhea

Clostridium perfringens and enterotoxin-producing strains of Bacillus cereus

Top 2 parasites causing waterborne diseases in the US?

Giardia, cryptosporidium parvum

fever/sore throat: chills, vomiting, abdominal pain, fine “sandpaper” rash, diffuse, blanching desquamation afterward. Strawberry tongue

scarlet fever (strep pyogenes)

 Impetigo: S aureus, MRSA, S pyogenes. Bullous (____) and non-bullous (_____). Nonfollicular. Most common among pre-school children. Progression: macule to honey colored crusty vesicle or pustule, pruritis, fragile vesicles rupture and can spread through scratching, poorly healing wound. More serious form found in Pts w/ pre-existing skin dz (eczema or superinfected chickenpox lesions)

BUllous = S aureus non-bullous = S pyogenes

bright red, sharply demarcated rash that is caused by S pyogenes. Sx: perianal rash, itching, rectal pain, blood streaked stools (1/3 of Pts). Primarily occurs in children b/w 6 months and 10 years of age

 Perianal streptococcal dermatitis

fever and an itchy rash, skin rash of blister-like lesions, covering the body but usually more concentrated on the face, scalp, and trunk

 Varicella zoster (chicken pox)

backache, delirium, diarrhea, excessive bleeding, fatigue, high fever, malaise, headache, vomiting, raised pink rash progressing simultaneously from macules to papules to pustules then scabs

 Variola (small pox)

 Varicella vs Variola(SP)

VZV – trunk, SP - extremities VZV – combination scabs, vesicles, pustules, SP – synchronous lesions VZV – contagious before pox appear, SP – contagious after pox appear

rash, Koplik spots (mouth), red eyes/photophobia, coughing, fever, runny nose, sore throat

• Measles (Rubeola):

fever, headache, general discomfort (malaise), and runny nose before rash appears, mild Sx associated w/ a rash, fever, headache, runny nose. Severe congenital infection.

• German measles (Rubella

pain, tingling, then blisters on the dermatome. Fever, headache, chills, upset stomach

• Shingles (varicella zoster):

): rash, fever, headache, slapped cheek appearance on face, then a “lacy” rash on extremities. Severe congenital infection

• Fifth disease (erythema infectiosum, parvovirus

High fever followed by a rash that appears on trunk, limbs, neck and face. Pink or rose colored, has fairly small sores that are slightly raised

• Roseola (erythema subitem, human herpes virus 6

fever, sore throat, swollen lymph glands; swollen spleen or liver involvement. Can look like strep throat

• Epstein Barr virus