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Diagnostic Studies > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Specimen Transport Materials (5 c what is transported in each, 1 medium c 3 subtypes)

A
  1. Sterile container
    • Urine
    • Body fluids
    • Tissue
  2. Transport media (keeps microbe alive for specific time)
    1. Amines, Stuarts
      • Routine cultures
      • Anaerobes
    2. Boric Acid
      • Urine
    3. Carey-Blair
      • Bacterial stool cultures
  3. Blood culture bottles
    • Aerobes
    • Anaerobes
    • Pediatric
  4. JEMBEC plate (isolates CO2)
    • N. gonorrhoeae
  5. NAAT transport kits (supplied by manufacturer for specific assays)
    • N. gonorrhoeae
    • C. trachomatis
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2
Q

Gram Stain (general procedure, 5 clinical uses)

A

“Procedure”: Direct staining of clinical samples. Only really reliable c associated culture

Applications:

  • **Determine presence of white cells **(specifically neutrophils)
  • Detrmine presence of “other diagnostic cells”
  • Determine presence of invading organisms
  • Identify predominating organism
  • Evaluate normal flora
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3
Q

Info included in Gram stain results

A
  1. +/- bacterial presence
  2. morphology (cocci, rod, diplococci) if bacteria present
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4
Q

Gram Stain Clinical Uses (4 tissues, purpose of eval of each)

A
  1. Sterile body fluids/wounds
    • Presence of WBC
    • Predominating bacteria/fungi
  2. Sputum (this is the best fluid for Gram staining)
    • Presence of WBC
    • Predominating organism
  3. Vaginal fluid
    • Bacterial vaginosis
  4. Stool
    • Presence of WBC
    • Campylobacter bacteria

Note: Skin and stool should contain normal flora. Bacteria in other samples is concerning

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5
Q

Blood and Sterile Body Fluid Gram Stain/Culture Indications; Provide microbe for the following initial reports and general significance of this information

  1. ​Gram + cocci in cluster
  2. Gram + cocci in pairs and chains
  3. Gram + rods
  4. Gram - rods
  5. Gram - diplococci
A
  1. Staphylococci
  2. Streptococci/Enterococci
  3. Bacillus/Clostridium/Cornebacterium
  4. None stated
  5. Neisseria

Significance: The preliminary reports will tell you this, so no real need to memorize. This preliminary information can guide your initial treatment before culture returns

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6
Q

Respiratory Infections (2 categories, 4/6 distribution)

A
  • Lower Respiratory
    1. Bronchitis
    2. Bronchiolitis
    3. Pneumonia
    4. Chronic
  • Upper Respiratory
    1. Pharyngitis
    2. Tonsilitis
    3. Laryngitis
    4. Rhinitis
    5. Misc.
    6. Oral cavity
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7
Q

Pharyngitis (3 causative microbes, collection media)

A
  1. Streptococcus pyogenes (Group A strep)
    • Rapid antigen test (in office)
    • Culture (only send if rapid antigen is -)
  2. ​Arcanobacterium haemolyticum
    • ​​Culture only
  3. ​Corynebacterium diptheriae
    • Must request
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8
Q

Tonsilitis (2 causative microbes)

A
  1. Streptococcus pyogenes
  2. Anaerobic bacteria
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9
Q

Pertussis/whooping cough (1 causative bacteria, collection material)

A

Bordetella pertussis

  • molecular detection assay

(May last up to 6 weeks)

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10
Q

Rhinitis and Laryngitis causative agent

A

Many viruses

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11
Q

Oral Cavity Infections (2 specific conditions, each c 1 causative agent)

A
  1. Stomatitis, caused by HSV
  2. Thrush, caused by Candida spp. (yeast)

These infections are primarily limited to immunocompromised individuals

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12
Q

Group A Strep Pharyngitis (causative microbe, general s/sx, 2 sequelae)

A

Bacteria: Strep. pyogenes

  • Gram + cocci in chains. NEVER FIND THIS OUT THRU GRAM STAIN. IT IS NEVER APPROPRIATE TO GRAM STAIN A THROAT CULTURE

S/Sx: Dysphagia, sometimes white exudate

Sequelae (if untreated):

  • Rheumatic fever
  • Acute glomerulonephritis
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13
Q

Scarlet fever (1 causative microbe, general s/sx)

A

Microbe: Special type of group A strep that produces pyrogenic exotoxins that cause characteristic s/sx

S/Sx: Red sandpaper rash + “straberry” tongue

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14
Q

Diptheria (1 causative microbe, transmission, s/sx)

A

Microbe: Corynebacterium diptheria

  • Gram + bacillus
  • Variable toxin production depending on strain. This will dictate s/sx

Transmission:

  • Sneezing
  • Respiratory secretions

S/Sx:

  • Pharyngeal only, organism accum + fibrin + inflamm cells form classic pseudomembrane over tonsils, larynx, pharynx, posterior nasal passages after 2-7 day incubation period
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15
Q

Pertussis (1 causative microbe, ID methodology, 3 stage disease progression)

A

Microbe: Bordetella pertussis

  • Gram - bacillus

ID: PCR

Pathogenesis:

  1. Catarrhal - most infectious
  2. Paroxysmal - “whooping” cough
  3. Convalescent
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16
Q

Rapid strep test sensitivity

A

80%

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17
Q

Name the causative microbe(s) of the following lower respiratory infections

  1. Bronchitis
  2. Bronchiolitis
  3. Chronic
A
  1. Usually viral, but consider B. pertussis (esp in young children)
  2. Viral
  3. Mycobacteria
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18
Q

Community-acquired Pneumonia (3 age groups, each c 1 causative agent)

A
  1. Children - viral (80% of the time. Viral panels offered)
  2. Young adults - Mycoplasma pneumoniae
  3. Adults - Streptococcus pneumoniae (usually. almost always bacteria)
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19
Q

Nosocomial Pneumonia (5 causative agents)

A

Leading cause of hospital deaths

  1. Gram - rods
    • E. coli
    • Klebsiella pneumonia
    • Pseudomonas aeruginosa
  2. Staphylococcus aureus (MRSA)
  3. Streptococcus pneumoniae
  4. Haemophilus influenzae
  5. Legionella pneumophila
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20
Q

Typical persistent CF infections (6)

A
  1. Pseudomonas aeruginosa
  2. Staphylococcus aureus
  3. Haemophilus influenzae
  4. Burkholderia cepacia complex
  5. Aspergillus spp. (not bacterial)
  6. RSV (not bacterial)
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21
Q

RSV (full name, pt pop, diagnostic eval)

A

Name: Respiratory Syncytial Virus

Pt Pop: very young children, almost exclusively in winter months

Dx: molecular viral panel

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22
Q

Ebstein Barr Virus (disease, 2 diagnostic tests)

A

Disease: Infectious mononucleosis (Pharyngitis/tonsilitis)

Diagnostics:

  1. Hetrophile antibodies
  2. Monospot, ELISA
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23
Q

Influenza Virus (3 strains, those who should receive vaccination, tx)

A

Strains:

  1. A (most pathogenic, H1N1)
  2. B
  3. C

Vaccination:

  1. >65 yo
  2. children/adol. on chronic asprin therapy
  3. nursing home residents
  4. lung/heart disease sufferers
  5. healthcare workers

Tx: Neuramidase inhibitors for those at high risk

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24
Q

Laboratory criteria for sputum and trachial aspirate culture rejection (and explianation)

A

Rejection criteria: >10 squamous cells/low power field sample

Explaination: these body fluids should be void of normal flora. This number of squamous cells represents a contaminated sample.

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25
Q

% of pneumococcal pneumonia pt blood/sputum cultures + for S. pneumoniae

A

Less than 16% of cases test positively, due to low sensitivity of cultures

26
Q

Eye Infections. Name causitive agents for the following:

  1. Blepharitis
  2. Conjunctivitis
  3. Keratitis
A
  1. S. Aureus, HSV
  2. H. influenzae, C. trachomatis, N. gonorrhoeae, viruses
  3. More dependent on trauma than microbe
27
Q

Ear Infections. Name causative agents of the following (2 each):

  1. Otitis Externa
  2. Otitis Media
A
  1. S. aureus, P. aerugiosa
    • P. aeruginosa smells like grapes
  2. H. influenzae, S. pyogenes (group A strep)
28
Q

Skin/Soft Tissue Wound Infections. Name microbes that can effect the following wounds:

  1. Postoperative infections (2)
  2. Bites (4, 2 categories)
  3. Burns (5)
A
  1. Indigenous microflora, nosocomial
  2. Two categories
    • Human: Group A strep, alpha hemolytic (virdans) streptococci, Eikenella corrodens
    • Dog: Pasturella spp.
  3. S. aureus, S. epidermidis, P. aeruginosa, various strep species, Candida spp.
29
Q

Shallow epidermal infectious agents (4, reference associated diseases)

A

Erysipelas, impetigo, folliculitis, furuncles, carbuncles

  • S. aureus
  • S. pyogenes (group A strep)
  • P. aeruginosa
  • Fungal infections in keratinized layer*
  • Dermatophytes
30
Q

Deep epidermal infectious agents (2 causative agents)

A
  1. S. aureus - most common for SQ tissue infections
  2. S. pyogenes (group A strep) - *most common for cellulitis *

Cellulitis, “subcutaneous tissue infections” (abscesses, ulcers, boils)

31
Q

Necrotizing Fasciitis (causative agent, s/sx)

A

Agent: S. pyogenes (most common) “flesh eating bacteria”

S/Sx:

  • Deep subcutaneous infection, destroying fascia and fat
  • Darkened skin
  • Blisters c bullae
  • Gangrene
  • Necrosis
  • High mortality rate
32
Q

Anthrax Toxicity (causative agent, transmission, s/sx)

A

Agent: Bacillus anthracis bacteria

Transmission: through breaks in skin. sources include

  • Farm animals: sheep, cattle, goats, swine
  • Bioterrorism (therefore all cases must be reported to CDC)

S/Sx:

  • Dermatologic - necrotic lesion
  • Systemic - adenopathy, fever, malaise
  • Pulmonary - dyspnea, cough, pneumonia
33
Q

Tetanus (causative agent and its infection patterns, pathogenesis, pt pop)

A

Agent and pattern: Clostridium tetani, anaerobic spore-forming bacteria whose spores will germinate in deep wounds

Pathogenesis: germinated spores will release neurotoxin that causes uncontrolled spasm and exaggerated reflexes

Pt pop:

  • Elderly
  • Migrant workers
  • IV drug users
34
Q

Skin infections caused by Human Papillomavirus (2)

A
  1. Various warts: skin, laryngeal, anogenital, cervical
  2. Direct cause of cervical cancer

Some vaccinations exist

35
Q

Skin infections caused by Varicella zoster (2, characteristics)

A
  1. Chicken pox, single infection = lifelong immunity
  2. Shingles (post herpetic neuralgia) = reactivation of dormant virus in ganglia
    • Zostavax will reduce incidence
36
Q

What type of Gram bacteria (+ or -) grow on MacConkey’s agar?

A

Gram - (usually)

37
Q

Cat Bites (causative agent, “3” diagnostic tests)

A

Agent: Pasteurella spp., Gram - rods

Diagnostics:

  1. Gram stain
  2. MacConkey’s agar (It won’t grow here! Usually Gram - rods will)
  3. Culture
38
Q

Bloodstream Infection Types (List and describe three)

A
  1. Continuous: Organisms released ito bloodstream at constant rate
    • Septic shock, bacterial endocarditis, infected intravascular catheter
  2. ​Intermittent: Demonstrated in patient’s c infections at a distal rate
    • Urinary tract, lungs, soft tissue
    • Note: appearance of clinical symptoms does not always correlate c presence of microorganisms in the bloodstream. Reccomended procedure is 2-3 sets drawn over a 24 hour period
  3. Transient: Organisms present in bloodstream for a short period of time as a result of manipulation
    • Dental work, surgery @ non-sterile site
39
Q

Factors affecting blood culture results (2 c associated good practices)

A
  1. Sterility: Follow disinfecting procedure exactly and allow area to dry prior to venipuncture. Also, draw from two sites to reduce skin contaminants
  2. Volume: Most blood culture bottles require 10 ml of sample for optimal results (3 ml in peds)
40
Q

Types of Bloodstream Infections (2, explain)

A
  1. Intravascular: originates within cardiovascular system
  2. Extravascular: infectious agent enters blood circulation thorugh lympatic system from another site of infection
    • Causes more clinically significant bacteremia
    • Occurs when a local is not completely cleared by reticulo-endothelial system and phagocytic cells
41
Q

Infective Endocarditis (pathogenesis, 11 causative agents - 1 important one)

A

Pathogenesis: Vegetation forms on cardiac endothelial surface. This provides environment for transient microorganisms to colonize, resulting in continuous bacteremia

Causative Agents:

  1. Virdans strep (most common, will probably won’t be reported as this, though. It will be reported as a the group of strep that it is)
  2. Abiotrophia
  3. Ganulicatella
  4. S. bovis
  5. S. aureus (usually in IV drug users)
  6. Coagulase negative straphylococci (CNS)
  7. Enterobacteriaceae
  8. Pseudomonas spp.
  9. Haemophilus spp.
  10. Fastidius GNRs
  11. Yeast
42
Q

IV and catheter-associated infections (6 causative agents, infiltration methods)

A

Organism Entry:

  1. Skin entry site
  2. Migration down lumen to catheter tip

Causative Agents:

  1. S. epidermidis, other coagulase negative staphyloccocci (CNS)
  2. S. aureus
  3. Enterobacteriaceae
  4. P. aeruginosa
  5. Candida spp.
  6. corynebacterium spp.
43
Q

Entry Methods, Extravascular Infections (6)

A
  1. “Unknown” Route
  2. Genitourinary tract
  3. Respiratory tract
  4. Abscesses
  5. Misc. sites
  6. Surgical wound infections

Listed from most to least common

44
Q

Sterile Body Fluids (List 6)

A
  1. CSF
  2. Pleural fluid
  3. Peritoneal fluid
  4. Peritoneal dialylsis fluid
  5. Pericardial fluid
  6. Synovial fluid
45
Q

CSF Collection and Transport (6 rules)

A
  1. Use sterile (aseptic) needle into lumbar space
  2. Collect 3-4 tubes
  3. Separate tubes: first two cannot go to micro (to elim chance of skin flora contamination)
  4. Hand deliver specimens to lab, if possible
  5. Do not refrigerate if indended for bacterial study
  6. Do refrigerate if intended for viral study (freeze if test will occur in >24 hours)
46
Q

CSF Result Interpretation. List the following qualities that appy to normal, bacterial infection, viral infection, TB/fungal infection:

  1. WBC/mm3
  2. WBC type
  3. Protein mg/dL
  4. Glucose mg/dL
A

For our purposes,

PMN = neutrophils

Mononuclear = probably lymphocytesUsually won’t have the cell type unless in a cell count

47
Q

Quickest CSF diagnostic tool

A

CSF Gram stain will yield results in minutes.

Cytospin specimen for optimal results

Agents revealed via CSF Gram:

  1. S. pneumonia
  2. N. meningitidis
48
Q

Encephalitis (causative agents, presentation, common time of year)

A

Agents:

  1. HSV-1
  2. Arboviruses
    • West Nile
    • St. Louis
    • EEE
    • Western equine
  3. HHV-6 (human herpes virus)
    • same as measles, mumps, varicella-zoster

Presentation: Only in HSV-1 encephalitis

  • Bloody CSF
  • very high protein (more than typical CSF viruses)
  • low glucose (less than typical CSF viruses)

Common Time: Warmer months

49
Q

Pleural Fluid Collection Techniques (3)

A
  1. Thoracentesis (needle aspiration) collection
  2. If blood culture bottles are inoculated at bedside, additional specimen is required for gram stain
    • This is true for all sterile body fluids except for CSF, which cannot be collected in blood culture bottles
  3. Ideally, submit greater than 5mL for Mycobacterium tuberculosis (MTB) cultures
    • You order acid fast culture
50
Q

Pericardial Fluid Collection Method

A

Collect via electrocardiograph assisted needle aspiration -or- as surgical procedure

Most commonly viral infections

51
Q

Complicated vs. Uncomplicated Urinary Tract Infections

A

Complicated

  • Occurs in either sex
  • Pts almost always predisposed
    • structural abnormality
    • kidney infection or predisposition
    • indwelling catheters
  • More than 105 cfu/mL

**Uncomplicated **

  • Occurs in healthy females
  • Usualy respond well to tx
  • More than 105 cfu/mL

CFU = colony forming unit

52
Q

Types of Urinary Tract Infections (5)

A
  1. Urethritis
  2. Asymptomatic bacteriuria
  3. Cystitis
  4. Urethral syndrome
    • Young, sexually active females c dysuria/frequency/urgency
  5. Pyelonephritis
    • Bacterial kidney inflamation
53
Q

UTI Testing (modality, 2 tests)

A

Modality: Urine dipstick screening

  • Aim for midstream sample

Tests:

  1. Nitrate Reductase
    • detects urinary nitrate present in UTI
    • detects nitrate reducing enzymes
  2. Leukocyte esterase
    • detects enzyme products of inflammatory cells
    • not sensitive enough to detect WBC’s themselves
    • for acute urethral syndrome
54
Q

Common Community Aquired UTI (6 causative agents)

A
  1. E. coli
  2. Klebsiella spp.
  3. Staphylococcus saprophyticus
  4. Enterobacter spp.
  5. Proteus spp.
  6. Pseudomas aeruginosa
55
Q

STD - Gonorrhea (causative agent, structure, s/sx, dx)

A

Agent: Neisseria gonorrhoeae

Structure: **Gram - diplococci **

S/Sx:

  • *Males - *milky discharge
  • *Females - *dysuria, urgency, vaginitis/cervicitis

Diagnosis:

  1. Intracellular organisms on Gram stain (male only)
  2. NAAT (hopefully required one day for sexual abuse cases)
  3. Culture (required for sexual abuse cases)
56
Q

STD - Chlamydia (causative agent, S/Sx, diagnosis)

A

Agent: Chlamydia trachomatis

S/Sx:

  • *Males - *most common cause of non-gonococcal urethritis
  • *Females - *asymptomatic, but can lead to PID and infertility

Diagnosis: Nucleic Acid Amplification Testing (NAAT)

Note: gram stain will show no organisms

57
Q

Botulism (causative agent, etiology, transmission method, dx test)

A

Causative Agent: Clostridium botulinum, a spore-forming anaerobe

Etiology: Ingestion of neurotoxin results inflaccid paralysis which eventually invades respiratory system

Transmission: Food that contains the neurotoxin-producing microbe

  • Home-canned/cured foods
  • Honey (most common agent for infant infection)

Diagnostic Test: molecular assay of stool sample (takes less than 1 hour to process)

58
Q

Pseudomembranous Colitis - Nosocomial (causative agent, etiology, dx test)

A

Agent: Clostridium difficile

Etiology: Reduction of normal bowel flora allows for neurotoxin production. This reduction is usualy due to long term/immunocompromised antibiotic adminstration

Dx: Demonstration of neurotoxin, probably by molecular assay of stool sample

59
Q

Salmonella spp. vs. Salmonella typhi

A

Salmonella spp.

  • Fecal-oral route, followed by ingestion of contaminated foods. Poultry, reptiles, and turtles can also be the initial vector
  • Requires large dose to be infectious
  • Causes **Gastroenteritis **after 6-48 hr incubation
  • Self-limiting

Salmonella typhi

  • Fecal-oral route, followed by organism entry into intestinal mucosa where they replicate, get engulfed by macrophages, and use them to transport through the body
    • May shed intermittently, if colonized in GB
  • Frequently isolated from blood and stool
  • Causes Typhoid Mary (Typhoid/enteric fever)
60
Q

Bacterial Gastroenteritis (most common causitive agent, structure, tranmission, s/sx, dx test, tx)

A

Agent: Campylobacter

Structure: Small curved rods, characteristic shape

Transmission: Fecal-oral, animals (99% chicken carcasses test positive)

S/Sx: bloody diarrhea, among others

Dx tests: Gram stain requiring special media and incubation above body temperature (42 degrees)

61
Q

Viral Gastroenteritis (2 causative agents, transmission, dx test for one, pt populations)

A

Agents:

  1. Rotavirus
  2. Norwalk Virus

Transmission: Generally, fecal-oral

  1. RV survives well on inanimate objects
  2. NV may have aerosolized vomitis transmission

Dx: Rotavirus present via ELISA or EIA

Pt Pop:

  1. RV in peds, <5yo
  2. NV on cruise ships
62
Q

List type (B/V/P), +/- fever, clinical presentation, and presence of fecal WBC for the following pathogens:

  1. Salmonella
  2. Shigella
  3. Campylobacter
  4. E. Coli O157:H7
  5. Yersinia
  6. C. difficle
  7. Rotavirus
  8. Norwalk Virus
  9. Giardia
  10. Cryptosporidium
  11. E. hystolytica

Diagnostic Studies (11 decks)

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