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Microbiology Prelim > Diagnostic Microbiology > Flashcards

Diagnostic Microbiology Flashcards

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1
Q

What are the objectives of Diagnostic microbio-

A

Confirm the diagnosis, Guide in treatment management

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2
Q

What are the points to consider for collecting a sample- Collection time period-

A

3rd week after infection in thyphoid, Handling and transport medium

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3
Q

What are the most common specimen types-

A

Blood, CSF, urine, Respiratory secretions, NP swab (COVID), feces, Genital secretions, Exudates and biopsy

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4
Q

What are the certain cases when blood is collected as a sample-

A

Hyperacute infection, G -ve sepsis and Subacute endocarditis- 3 samples in 24 hours

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5
Q

What are the steps to collect blood- Sterile syringe, tourniquet to expose veins, prepare the site-

A

2% iodine, 70% alc. And draw 20ml.

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6
Q

How long should the sample be incubated for Brucella infection-

A

37 deg, for 5-7 days

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7
Q

What are the criteria for diagnosing Bacteremia-

A

Growth of the same organism at different sites of sample

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8
Q

Criteria for diagnosing contamination-

A

Different bottles and different cultures at different times

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9
Q

What types of samples are etiologically significant?

A
  • S. viridans in endocarditis, G +ve; E. coli- sepsis, G -ve
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10
Q

How to collect samples for CNS infections?-

A

LP and CSF culture, Cell count, Protein

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11
Q

For a patient presenting with COVID-19 like symptoms, how to collect a sample?-

A

Throat swab/throat washing and Nasopharynx swab in charcoal for COVID-19 and Pertussis

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12
Q

If a patient presents with symptoms of LTRI, how to collect the sample?-

A

Wide mouth plastic sterile cont, before therapy, in the morning, Good sputum with WBC, saliva, >25 cells, bad sample.

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13
Q

What are the other ways to\collect LTRI samples-

A

Transtracheal aspirates, Bronchoscopy, Lung biopsy, and Bronchoalveolar lavage.

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14
Q

How are samples collected for an Eye infection?-

A

Sterile platinum loop, smooth, thin plastic/glass rod, Stuart medium swab, amd infection around eyes.

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15
Q

For a patient with an earache, what are the ways to collect a sample for diagnosis?-

A

Swabs

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16
Q

What are the various ways to collect samples for GIT infections?-

A

Feces- into a sterile bedpan, 1-2 ml, add 6ml glycerol to help transporting and rectal swab.

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17
Q

In the presence of an exudate- wounds, and abscess, how are samples collected?-

A

Pus from an abscess and open wounds, In closed spaces, Pleural or peritoneal or synovial surfaces aspiration.

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18
Q

What is the term for the wide open wounds?-

A

Carbuncle and cellulitis can still be aspirated.

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19
Q

What diseases constitute Upper UTI?

A

Kidneys- Leptospirosis, typhoid, and AGN

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20
Q

When to “catch” urine specimen for men?-

A

Clean meatus, midstream

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21
Q

Urine sample collection for a female-

A

Spread the labia and vulva, wash it thoroughly and collect midstream.

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22
Q

If suffering from urinating issues what method should be implemented?-

A

Suprapubic.

23
Q

How is vaginal infection confirmed?

A

often purulent,

putrid or fishy-smelling

24
Q

In cases of vaginosis, candidiasis, and trichomoniasis

A

Swab on the
cervical surface and not on the
vaginal wall.

25
Q

Syphilis:

A

Try to irritate the surface of the wound,
the Chancre, with acetone or ether. Then,
observe the development of some fluid coming
out, which is the one collected and used for examining Treponema pallidum. Organisms will
be inside the lesion.

26
Q

ANAEROBIC INFECTIONS

A

The large majority of human normal flora are
anaerobes, and when they are displaced from
their normal sites, they produce disease.

27
Q

CHARACTERISTICS / CONDITIONS WHICH

SUGGEST ANAEROBIC INFECTIONS

A 
SUGGEST ANAEROBIC INFECTIONS
1. Often contiguous with the mucosal surface
2. Tend to involve many organisms, which
these organisms are the anaerobes plus
the aerobes; a multi-etiology.
3. Tend to form closed-space infections
either as discrete abscess (e.g. Lungs,
brain, pleura, peritoneum, pelvis) or by
burrowing through tissue layers
4. Pus with a foul odor
5. Favored by the reduced blood supply
28
Q

Collection of specimens for anaerobic

A 
○ Swabs are not used
○ For closed abscesses, aspirate
aseptically, avoid entry of air by sealing
the needle after the procedure
○ Use appropriate transport media when
the specimen has to be brought to a
distant laboratory.
29
Q

THE 5 I’S OF CULTURING MICROBES

A

Inoculation, incubation, isolation, Inspection, and Identification

30
Q

Media -

A

providing nutrients in the laboratory

31
Q

Most commonly used media

A

○ Nutrient broth - liquid medium
containing beef extract & peptone
○ Nutrient agar - solid media containing
beef extract, peptone & sugar

32
Q

Agar -

A
  • a complex polysaccharide isolated from
    red algae.
  • Solid at room temperature, liquifies at
    boiling (100℃), does not resolidify until it
    cools to 42℃)
  • Provides a framework to hold moisture &
    nutrients
  • Not digestible for most microbes
33
Q

Forms of physical Media

A

liquid, semisolid and solid

34
Q

Types of media

A

Synthetic- pure inorganic or organic
Complex/non-syn- non chemically defineable ingredient
General-purpose media - grows a broad range
of microbes, usually nonsynthetic

Enriched media - contains complex organic
substances such as blood, serum, hemoglobin or
special growth factors required by fastidious
microbes

35
Q

ENRICHED MEDIA

A

● The most common enriched media is blood agar.
● The organism in plate A produces hemolysis
● Chocolate agar is a variation of blood agar plate.
It is blood agar which is heated, it turns to a brown
color.

36
Q

Selective Media

A

● Contains one or more agents that inhibit growth
of some microbes and encourage growth of the
desired microbes
● Example: Salmonella/Shigella agar medium- will
only allow the growth of Salmonella species and
Shigella species

37
Q

Differential media

A

● Allows growth of several types of microbes and
displays visible differences among desired and
undesired microbes
● A good example of this is the MacConkey agar. It
will allow the growth of organisms that can
ferment lactose and organisms that do not
ferment lactose

38
Q

misc. media

A

Reducing medium - contains a substance that
absorbs oxygen or slows penetration of oxygen
into medium; used for growing anaerobic bacteria

Carbohydrate fermentation medium - contains
sugars that can be fermented, converted to acids,
and a pH indicator to show the reac

39
Q

Magnification

A

ability to enlarge objects

40
Q

Resolving power -

A

ability to show detail; the
higher the resolving power, the higher the ability
to see the details of the particular object being
examined

41
Q

Oil immersion lens

A

● The oil makes it possible for the organism being
examined to be seen more clearly in the
microscope.
● The rays of light are concentrated to the point of
examination and bounce back to the eyes.
Without oil, you lose some of the light waves.

42
Q

Bright- field -

A

The most widely used, the specimen is

darker than the surrounding field

43
Q

Dark Field-

A

brightly illuminated specimens
surrounded by darkfield; a special type of light
microscope whereas instead of seeing the field to
be brightly illuminated, what you will see is a
background of black and only the ones that you
want to see are illuminated. So they will stand out.
This is the one used for Treponema pallidum and
also for Leptospirosis

44
Q

Phase-contrast -

A

transforms subtle changes in
light waves passing through the specimen into
differences in light intensity, best for observing
intracellular structures

45
Q

FLUORESCENCE MICROSCOPY

A

Modified compound microscope with an
the ultraviolet radiation source and a filter that
protects the viewer’s eye

Useful in diagnosing infections-For example, Treponema pallidum (Syphilis), you
can tag the antibodies against the T. pallidum
with special dye

46
Q

ELECTRON MICROSCOPY

A

Forms an image with a beam of electrons that can
be made to travel in wavelike patterns when
accelerated to high speeds.
● Electron waves are 100,000X shorter than the
waves of visible light.

47
Q

Two types of electron microscopy

A 
○ Transmission electron microscope
(TEM) - transmits electrons through the
specimen; darker areas represent
thicker, denser parts and lighter areas
indicate more transparent, less dense
parts
○ Scanning electron microscope (SEM)
- provides detailed three- dimensional
view. SEM bombards the surface of a
whole, metal- coated specimen with
electrons while scanning back and forth
over it.
48
Q

STAINING PROCEDURES

A

● In bacteriology, staining procedures are very
important because one staining procedure gave
us a very big classification of the bacteria. The
Gram staining classified the bacteria into two
types of microorganism– the gram positive
organism and the gram negative organism. Their
cell walls are responsible for their classification.

49
Q

Wet mounts & hanging drop mounts -

A

allow examination of characteristics of live cells:
motility, shape, & arrangement; you examine the
specimen as is

50
Q

Fixed mounts

A

are made by drying & heating a
film of specimen. This smear is stained using
dyes to permit visualization of cells or cell parts.

51
Q

Dyes

A

○ Cationic dyes - basic, with positive
charges on the chromophore
○ Anionic dyes - acidic, with negative
charges on the chromophore
○ Positive staining - surfaces of microbes
are negatively charged and attract basic
dyes; the cell wall will be stained
○ Negative staining - microbe repels dye
& it stains the background; an example of
this is when you want to see the
capsulated microorganism,

52
Q

Simple stains -

A

one dye is used

53
Q

Differential stains

A

use a primary stain and a

counterstain to distinguish cell types or parts. Gram stain Acid- fast stain

54
Q

Special Stain

A 
- India ink capsule stain of Cryptococcus neoformans. You use the India ink so 
what you see is the Cryptococcus’ very 
thick capsule.
- Flagellar stain. The red ones are the 
flagellar stains

Microbiology Prelim (7 decks)

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