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753 - Micro > Quiz 3 > Flashcards

Quiz 3 Flashcards

1
Q

Which species of Neisseria are clinically significant?

A

N. meningitidis
N. gonorrhoeae

Gonorrhea is not confined to genitals it can be seen in blood cultures and other body sites

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2
Q

What are the general characteristics of Neisseria?

A

diplococci, non-motile, aerobic, capsules found on pathogenic species (virulence factor)

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3
Q

Medically significant Neisseria

A

It can cause infection in pharyngeal region and move through the nasal cavity into the meninges (lining around the brain/spinal cord)

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4
Q

Meningitis

A

Can cause vascular collapse, hemorrhage and petechiae (trunk/extremities), intravascular clotting and death

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5
Q

What is the most common non-pathogenic Neisseria?

A

N. lactamica

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6
Q

How are Neisseria and related organisms divided?

A

group 1 - traditional pathogens
group 2 - commensal Neisseria, that can grow on selective media like MTM
group 3 - commensal Neisseria that usually doesn’t grow on selective media

Group 2/3 further classified by carbohydrate profile (saccharolytic/asaccharolytic)

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7
Q

Non-pathogenic Neisseria and how they affect immunocompromised people

A

Opportunistic infections (endocarditis, meningitis, otitis media, neonatal conjunctivitis and pneumonia

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8
Q

How is N. lactamica differentiates from other species of Neisseria?

A

Glucose, maltose and lactose +

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9
Q

Characteristics of Moraxella

A

Hockey puck colonies (SBA/Choc), asaccharolytic and + butyrate esterase

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10
Q

How to R/O Acinetobacter w/ other GNC

A

Its oxidase -

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11
Q

Sample collection/transport Neisseria

A

JEMBEC (incubate ASAP) plates for transport, dacron/rayon swab used for genital swab w/charcoal in medium to inhibit fatty acids

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12
Q

Antigen detection of Neisseria

A

CSF, urine, serum (not blood it dilutes the organism) Ag detected by latex agglutination assays

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13
Q

N. meningitis serotype B

A

Most virulent, shares a lot of cell membrane lipids that mimics our cell membrane lipids (virulence factor) which help it to avoid detection

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14
Q

Neisseria (antibiotics/vaccine)

A

Penicillin G to treat N. meningitis, N. gonorrhea is resistant to penicillin

Vaccine available - serotypes A, C, Y, W135

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15
Q

Features of Bacillus

A

Widely distributed through nature

  • thermophiles
  • plant or insect pathogens
  • used in autoclave/disinfectants
  • producers of antibotics/vitamins
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16
Q

Features of Bacillus cont…

A

Aerobes/facultative anaerobes, form endospores, catalase + (unlike clostridia)

  • fast growers (SBA)
  • lab contaminants
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17
Q

Which Bacillus species are associated with human disease?

A

B. anthracis

B. cereus

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18
Q

Bacillus anthracis

A
  • large GPR
  • flat, ground-glass/powdery
  • non-hemolytic
  • non-motile
  • sticky/tenacious consistency (stands up like beaten egg whites)
  • Does not grow on MAC
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19
Q

B. anthracis microscopic morphology

A
  • as culture ages, vegetative cells are easily decolorized

- spores are not always present

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20
Q

What are the 3 recognized forms (anthrax) in humans?

A
  • Cutaneous (most common) - cuts contaminated w/spores, eschar (depressed black necrotic ulcer)
  • inhalation of spores
  • gastrointestinal ingested spores in food (fatality rate higher than cutaneous)
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21
Q

B. cereus morphology

A

silver, beta hemolytic

box car shape, gram variable

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22
Q

B. cereus

A

Destroyed by properly cooking food

-causes food poisoning and serious rapid eye infections

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23
Q

Corynebacterium

A

Palisades, V/L GPR

  • animal/plant/human pathogens
  • both lipophilic/non-lipophilic
  • opportunistic
  • isolated from blood cultures/normal sterile sites
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24
Q

C. diphtheriae

A
  • diphtheria toxin
  • lysogenic bacteriophage carries tox gene
  • 2 different forms (human disease) respiratory (w/pseudomembrane) and cutaneous

-conjunctivitis, bull neck, myocarditis

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25
Q

What media is used to culture C. diphtheriae?

A

Dacon, calicum alginate swab

  • cystine-tellurite (tinsdale) media – black colonies w/brown halos
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26
Q

Can C. diphtheriae be treated w/ antibiotics?

A

No, the toxins will become activated and interact w/heart muscle can lead to cardiac failure

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27
Q

Erysipilothrix rhusipathiae

A

Grows on TSI slant even though its for GN organisms

  • H2S production
  • BRUSH LIKE PATTERN (test tube)
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28
Q

What infection does E. rhusipathiae cause?

A

skin infections (associated w/animals) farmers, vets, fish handlers

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29
Q

What does Lactobacillus resemble?

A

tiny alpha-hemolyic streptococci

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30
Q

What are the clinical settings of lactobacillus?

A

Normal vaginal, GIT flora and may cause meningitis and septicemia in immunocompromised

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31
Q

What are the normal genital flora?

A

Staph, corynebacteria, lactobacillus (women/reproductive age) enterobacteria, strepococcus

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32
Q

What happens when normal flora of the vagina go away?

A

pH levels increase

normal flora (g. vaginalis, prevotella, peptostreptococci, mobiluncus and mycoplasma

33
Q

How is bacterial vaginosis diagnosed?

A

Gram stain of vaginal discharge (use Nugent scoring system)

  • clue cell presence
  • almost absence or complete absence of lactobacilli
34
Q

Diagnosis of Bacterial vaginosis cont…

A

milky discharge, pH more than 4.5, presence of clue cells, whiff test (fishy odor), lack of lactobacilli

need at least 3 conditions for diagnosis

Complications - chorioamniontis, preterm labor, still birth

35
Q

Listeria monocytogenes

A

Single/short chains, beta hemolytic, tumbling motility, zoonotic
UMBRELLA MOTILITY - test tube

36
Q

What are the clinical settings of L. monocytogenes?

A

meningitis, septicemia of immunocompromised, stillbirth, gastroenteritis in immunocompentent hosts

37
Q

Genus Mycobacterium

A

Obligate anerobes, intracellular, waxy coating on cell surface (mycolic acid), impervious to gram staining

38
Q

2 pathogenic mycobacterium species

A

M. tuberculosis

M. leprae

39
Q

What are some general characteristics of mycobacterium?

A

acid fast, aerobic, non-spore forming, non-motile, high lipid content cell wall, slow growing

acid alcohol does not decolorize them

40
Q

Stats of TB

A

1.6 million deaths 2017, 10 million new cases and 1.8 billion still have TB

41
Q

Drug resistant TB

A

XDR-TB

42
Q

Symptoms of TB

A

weakness, weight loss, chills, fever, child failure to thrive, coughing of blood, difficulty breathing

43
Q

Out of the multiple members of M. tuberculosis complex, which ones infect humans?

A

M. tuberculosis, M. africanum, M. canetti

44
Q

Runyon’s classification - 4 groups

A

Gp I Photochromogens (yellow-orange pigment w/exposure to light, take 7 + days to grow) - M. kansasii

Gp II Scotochromogens (yellow orange culture whether grown in dark or light, take 7 + days to grow) tap water M. gordonae

GP III Nonchromogens - never produce pigments, take 7 + days to grow

GP IV - rapid growers (grow < 7 days, they may or may not be pigmented)

45
Q

Overview TB

A

TB is an aerosol transmissible disease (1-10 organisms = infectious)

46
Q

What are normal flora of the lower respiratory tract?

A
  • nonhemolytic streptococci
  • corynebacteria
  • coag (-) staph
  • stomatococcus mucilaginosa

& nonpathogenic Neisseria spp.

47
Q

Host resistance (lower respiratory infection)

A

Mucous, cilia, alveolar macrophages, secretory IgA, natural antibacterial substances in secretions (lysozyme)

48
Q

What are the mechanisms of infection?

A

adherence, toxin production, host tissue damage, capsules, growth intracellularly

49
Q

Examples of adherence factors

A

Lipoteichoic acids and M proteins (s. pyogenes)

fimbriae (pili) of enterobacteria and other GNRs

50
Q

Examples of toxin production

A
  • Extracellular toxins of C. diphtheria, B. pertussis and P. aeruginosa
  • harmful enzymes produced by S. aureus and S. pyogenes (group A strep)
51
Q

Examples of host damage by microbial growth

A
  • the growth interferes w/normal host function

- growth triggers immune response

52
Q

CHUM and its features

A

M. chelonae, M. haemophilum, M. ulcerans and M. marinum

Isolated from skin and require lower primary recovery temps of 30-32*C

53
Q

Safety rules for working with TB

A

Sterile, leak-proof, non breakable container
- workers must be trained
- meet level of competency
Training (use of equipment, decontamination, spill clean-up, use of autoclave, waste disposal)

Aerosol transmissible disease standard
Testing must be done in a BSC level 3
Work 4-6” from grill, clean with tuberculocidal disinfectant
Wear PPE

54
Q

Sputum processing

A

Expectorated (deep, productive cough) and induced (w/ 5-10% hypertonic saline)

3-5 morning sputum specimens
NaOH decontamination & NALC digestion

55
Q

Acid-Fast Stains

A

Auramine-rhodamine (higher sensitivity, recommended by CDC, fluorescence microscope)
Ziehl-Neelsen = carbolfuchsin (light microscope)

56
Q

Media used to culture TB

A

Solid - egg based: LJ, agar based: Middlebrook 7H10, 7H11

Liquid - MGIT (BD), BacT/Alert (bioMerieux), Myco (VersaTrek)

57
Q

Is sputum a valuable diagnostic specimen?

A

Yes, it is a non-invasive specimen, the etiologic agent of disease can sometimes be isolated

It can also be No, sputum samples are contaminated with upper respiratory flora, its time consuming, collection is demanding of the patient and lab worker and delivery must be quick

58
Q

What options are available for expectorated sputum?

A
  • Induced sputum
  • gastric aspirate
  • bronchoscopy (bronchial wash is better than sputum but contaminated with URT flora, bronchoalveolar lavage)
  • lung biposy
59
Q

What are 2 ways to detect streptococcal pharyngitis?

A

culture

direct Ag testing of the throat specimen

60
Q

Culture for S. pyogenes

A

sheep blood agar w/SXT disc

stab culture or incubate anaerobically, capnophilic

61
Q

Culturing for B. pertussis

A

Nasopharygeal swab, inoculate at bedside

Bordet Gengou and charcoal based Regan-Lowe

DFA/PCR to ID

62
Q

Endogenous vs Iatrogenic Infections

A

Overgrowth of normally present organisms

Introduced by medical procedures

63
Q

Curable STDs

A 
syphilis
chancroid
gonorrhea
chlaymydial infection
trichomoniasis
64
Q

Syphilis vs Chancroid

A

Chancre: painless, uniform margin, firm/hard on touch GNR (train tracks) More common in US

painful, oozing/irregular margins, softer to touch
haemophilus ducreyi (X+V)
school of fish

65
Q

Curable STD’s: Non-Ulcerative

A

Gonorrhea/chlamydia
women usually asymptomatic

Men - urethral discarge

Trichomoniasis
Women - vaginal discharge, Men - asymptomatic

66
Q

Most common STD in US

A

Chlamydia - GN obligate intracellular bacteria

C. psittaci - agent of bioterrorism

Gonorrhea

67
Q

Major life cycles of Chlamydia

A

Elementary bodies - reticulate body - inclusion

68
Q

Elementary vs Reticulate body

A

Ele.
infectious, metabolically inactive, smaller

Ret.
non-infectious, active, bigger

69
Q

What disease does chlamydia cause

A

pelvic inflammatory disease, including endometritis

70
Q

Detection/culture of chlamydia

A

Specimen added to McCoy cell layer in shell vial

+ results (c. trachomatis)

DFA is more accurate and sensitive
EIA/nucleic acid amp assay

There is 1 assay that will detect (chlamydia, gonorrhea and trichomonas)

71
Q

What diseases does N. gonorrhea cause

A 
urethritis
cervicitis
conjunctivitis in newborns
Pelvic inflammatory disease
arthritis
bacteremia
72
Q

Gonorrhea cultures

A

Use stuart’s and amies charcoal medium (culture w/in 12 hours)
Selective Media - modified Thayer-Martin
NYC medium
JEMBEC plates

Oxidase +

73
Q

Antibiotics Used for media

A

Vancomycin for GP
Colistin for GNR
Trimethoprim for Proteis
Nystatin for yeast

74
Q

What is always performed w/gonorrhea

A

AST

75
Q

Trichomoniasis

A

Urine samples
wet mount (jerky movement)
Rapid test - target trichomonas antigen

76
Q

Syphilis

A

spirochete
can’t be gram stained - t. pallidum

-once in macrocytes they can be spread to any part of body

77
Q

Stages of syphilis

A

Primary - darkfield microscopy/DFA
secondary - serological testing
Latent - serological testing
Tertiary - serological testing

78
Q

Serological Testing of Syphilis

A

Non-treponemal tests - screening tests (VFRL/RPR)

Treponemal tests - detects Ab specific to T. pallidum (FTA-ABS and MHA-TP)

753 - Micro (5 decks)

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