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Microbiology > Medically Important Gram Negative Bacteria > Flashcards

Medically Important Gram Negative Bacteria Flashcards

1
Q

What kind of bacteria do not retain the crystal violet dye

A

Gram negative so they show red or pink color due to the safranin
This is based on their cell component

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2
Q

Gram negative cell wall is made up what

A

Outer membrane which is made up ofLPS) and peptidoglycan layer

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3
Q

The LPS is made up of

A

Oligopolysaccharides
Core polysaccharides
Lipid A layer

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4
Q

The main component of LPS is

A

Lipid A

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5
Q

What forms the backbone of the Gram negative cell wall

A

Lipoproteins which transport lipids and phospholipids which serve as a barrier for molecule movement

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6
Q

What is the surface layer and where is it attached to in Gram negative and positive bacteria

A

Surface layer is an adhesive structure and makes the bacteria more virulent
It is attached to the LPS layer in Geam negative and the peptidoglycan layer in Geam positive

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7
Q

Gram positive can retain crystal violet dye and Geam

Negative can’t because

A

It’s layer is thick and the stain can penetrate the plasma membrane so it stains it so the layer retains the stain
Decolorizer cannot penetrate the peptidoglycan layer cuz the layer is thick

It is easier for gram negative cuz the outer membrane can be dissolved by the ethanol or decolorizer so the decolorizer removes the crystal violet stain so they can’t retain the crystal violet

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8
Q

Both Gram positive and negative have flagella.
If flagella is present in Gram negative it’ll have four supporting rings while in Gram positive it’ll have two supporting rings. True or false

A

True

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9
Q

In Gram negative, there is periplasmic space between the peptidoglycan and the Outermembrane. And S layer is attached to the outer membrane but in Gram positive Teichoic acids make it flexible but these acids are not found in Gram negative
True or false

A

True

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10
Q

Example of gram negative

A

Enterobacteriacea

Salmonella

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11
Q

Where does enterob live

A

In the colon and are facultative anaerobes(can grow in the presence or absence of oxygen h

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12
Q

Some enterob are normal flora which can take advantage of a weakened immune system to cause diseases( opportunistic pathogens)and some are true or obligate pathogens true or false

A

True

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13
Q

Example of opportunistic bacteria

A

Escherichia coli
Klebsiella pneumoniae
Enterobacter, Serratiaand Citrobacter (collectively called the coliform bacilli) and Proteus

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14
Q

Example of true pathogens

A

Some Ecoli strains

Salmonella species

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15
Q

Charact of enterob

A

non-spore-forming rods. Characteristics of this family include being motile except klebsiella, catalase positive, and oxidase negative; reduction of nitrate to nitrite; and ferment glucose, facultative anaerobes
They are non fastidious ( they can eat anything to survive)

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16
Q

The true pathogens cause diarrheal diseases

True or false

A

True

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17
Q

Normal flora can take advantage of a weakened immune system. Which diseases do they cause when they do that

A

Meningitis
Sepsis
UTI
Pneumonia

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18
Q

Explain oxidase test and catalase test for enterobacteriace

A

Filter paper is put in oxidase solution
Bacteria is cultured and put on the paper
If it turns purple it’s positive
If not purple it is negative

Catalase test
They break down hydrogen peroxide into water and oxygen causing bubbles to form and color is white
Therefore they catalase positive

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19
Q

Explain classification based on lactose to classify enterob and give examples

A

If you ferment lactose it means you can change the color of the media you grow on. Example- E. coli, enterobacter, klebsiella
If you can’t, then you’re a non lactose fermenter- salmonella

Some ferment lactose but it takes a longer time and those are late lactose fermenters

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20
Q

E. coli cause diarrhea. How is it transmitted

A

Contaminated food and water

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21
Q

Name virulence factors of Ecoli

A

It has Adhesins - help facilitate attachment to wherever they are found

Has O antigen which comes from the outer membrane and the capsule
Both Gram positive and negative are capsulated
Colonization factor antigens example pili
Has toxins- haemolysins, endo and exotoxins

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22
Q

Which E. coli cause diarrhea

A 
Enteric E. coli
Example, enterotoxigenic (a major cause of travelers' diarrhea and infant diarrhea in less-developed countries), enteroinvasive (a cause of dysentery), enteropathogenic (an important cause of infant diarrhea), and enterohemorrhagic (a cause of hemorrhagic ...
Enteroaggregative E. coli (EAEC)
Enteroinvasive E. coli (EIEC)
Diffusely adherent E. coli (DAEC)
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23
Q

Pathogenesis of E. coli

A

Enterotoxigenic E. coli
Causes diarrhea to children under five years and travelers and mostly occurs in developing countries

It produces exotoxins and these can be heat labile or heat stable . After ingestion of contaminated food, it is able to stick to the intestine by the presence of the pili. Once it sticks to the pili, those with heat labile toxins release those toxins
Have two components- A subunit and B subunit
B subunit is a pentagon and A is a single subunit
The toxins stick w the B subunit and the A subunit moves thru the B subunit and activates the adenylate Cyclase or the toxins activate the adenylate cyclase
It causes an increase in CAMP(cyclic adenosine monophosphate) which causes secretion of electrolytes causing diarrhea

If it is a heat stable toxin producing E. coli, it produces heat stable toxins and activates guanylate cyclase and the same process goes on

24
Q

Lab diagnosis of E. coli

A

Stool is cultured on MacConkey agar and incubate at 5 percent carbon dioxide at 37 degrees Celsius for 18-24hours

When the bacteria grows to check if it’s E. coli you do a further test which is a biochemical test and you can do a lactose fermenter test. E. coli ferments lactose
IMVIC test-
I- positive 
M-positive
VI-negative
C-negative
25
Q

Which salmonella species causes diseases

A

Salmonella typhi

Salmonella enteritidis

26
Q

Salmonella can cause septicemia if found in the blood

True or false

A

True

27
Q

It’s either salmonella causes typhoid,septicemia or gastro enteritis( inflammation of stomach and intestines) true or false

A

True

28
Q

Pathogenesis of salmonella

A

When In the body
Salmonella invaded the
Mucosal epithelial cells in the intestines and enters the lymphatic then moves into the bloodstream where it multiplies and moves to other organs. They keep multiplying in these organs
Some multiply in the lymphoid tissues which ate associated w Peyers patches they cause necrosis in the peyers patches as they multiply and can be excreted in stools

Complication of salmonella typhi- perforation of intestines

29
Q

Samples for diagnosis -

A

Enteric fever- blood, bone marrow, urine
Diarrhea- stool
Food poisoning- stool, vomitus
Septicemia- blood

30
Q

Lab diagnosis of salmonella

A

Sample is cultured on salmonella shigella agar under 5 percent carbon dioxide, 37degrees Celsius for 18-24hours
These are non lactose fermenters
Further test to identify if it’s salmonella or not
TSI( triple sugar iron)
Are glucose fermenters
Butt is acidic and slant is alkaline
They produce hydrogen sulphide gas

31
Q

Gram negative cocci example

A

Neisseria species( Neisseria gonorrhoeae and Neisseria meningitidis

32
Q

Features of Neisseria species specifically

The one that causes gonorrhea and meningitis

A

Are non motile so no flagella
Shape is diplococcus
Are Oxidase and catalase positive
Both ferment glucose

33
Q

NG causes which diseases

A

Conjunctivitis
Pharyngitis
Some anal infections
Gonorrhea

34
Q

Virulence factors of NG

A

Pili
Have lipooligosaccharides(toxins)
It is sexually transmitted

35
Q

Gono is more common in females than males why

A

Females sexual organ has large surface area to attract more secretions so the infection spreads faster

36
Q

Pathogenesis of gono

A

When infected thru sex Gonococci attaches to the mucus membranes . Then it produces pus then the pus helps it invades the tissues then it causes chronic inflammation of the tissues and leads to thickening of the connective tissues

In men it causes urethritis with yellow creamy pus . It results in dysuria
In women it affects the endocervix and spreads to the urethra leading to mucopurulent discharge( mucus and pus mixture)
Can cause sapringitis (inflammation of Fallopian tube and can cause infertility)

37
Q

Lab diagnosis

A

Gram staining then you culture using the pus or mucus
Culture on chocolate agar or modified Thayer Martin agar
Under the same conditions
Oxidase test
ELISA to check for Gonococci antigen

38
Q

Treatment and prevention

A

Azithromycin
Avoid many sexual partners
Ceftriaxone

39
Q

Meningitis usually happens as an outbreak or epidemic but there are some isolated cases and mostly occurs in groups
Those who go on religious pilgrimages and is common in sub Sahara Africa
True or false

A

True

40
Q

Where does NM affect

A

Upper respiratory tract infection by airborne droplets

41
Q

Virulence factors of NM

A

Capsule
LPS
IgA protease - when body encounters microorg it responds by producing igA
When produced it prevents the microrg from establishing itself
NM also has IgA and releases it to breakdown the body’s IgA which helps it attach to the body surface and still cause harm
They ferment maltose

42
Q

Maltose fermentation test is used to distinguish between NG and NM true or false

A

True

43
Q

Pathogenesis of NM

A

They attach to the nasopharynx and enter the bloodstream and spread to the meninges and joints which result in stiff neck and headache and fever

44
Q

Samples taken for NM and lab diagnosis

A

CSF or blood
Culture on Thayer Martin or chocolate agar under same conditions
Then do Maltose test to see if it is NM and not NG
Cuz NM ferments maltose

45
Q

Treatment and control of NM

A

Penicillin

46
Q

Example of facultative( it lives with or without a host) rods

A

Vibrio species
Genus- Vibrio Cholerae
Vibrio parahaemolyticus, and V. vulnificus.
They are comma shaped
They have one flagella.
These species are grouped into two
Those that love salt-halophilic and. Non halophilic
V cholerae- non halophilic and the other two are halophilic

47
Q

V cholerae causes

A

Severe dysentery

48
Q

V culnificus causes? And V para causes?

A

Wound infection

Diarrhea infections which are self limited

Are usually gotten when you eat under cooked shell dishes such as shrimps and contaminated food and drinks

49
Q

If it’s cholera what occurs

A

Person becomes very dehydrated

50
Q

Pathogenesis for V cholerae

A

Same pathogenesis for E. coli
It adheres to the small intestine it
Multiplies and spread and produces a toxin that activates the adenylate cyclase which causes increases in CAMP and diarrhea produced by V cholerae is called rice water stool

51
Q

Lab diagnosis of V cholerae

A 
Slimy mucus flecks are taken from the stool and they are cultured on TCBs selective thiosulfate–citrate–bile salts agar (TCBS) 
Under same conditions 
If there’s yellow colonies- V cholerae
Green- V para 
Blue green- V volnificus
52
Q

Campylobacter character

A

S shaped and a facultative rod shaped
Are transmitted by contaminated food and drink
Cause gastroenteritis and diarrhea
Campylobacter jejuni causes the gastroenteritis and diarrhea

53
Q

Gram negative aerobic rods example and culture and disease it causes

A

Pseudomonas aeruginosa which is peculiar by the presence of the pigment it secreted which is green blue when cultured
It requires moisture to survive
It causes nosocomial infections and UTI and skin infections

54
Q

Gram negative coccobacilli . Give four examples along w characteristics, virulence factors

A

They have a coccus and bacilli shape
Haemophilus influenza
Affects mucus membranes of upper resp tract. Has capsule as virulent factor
Causes meningitis in children and pneumonia in adults

Haemophilus ducreyi
Sexually transmitted disease called chancroid. It affects the genitals and it results in swollen and soft genitalia which causes enlarged lymph nodes unlike syphillis which is hard

Bordetella pertussis
Aerobic coccobacilli
Causes whooping cough(pertussis)
It can be prevented by vaccination

Spirochetes
They’re spiral shaped, long, coiled, motile,spiral
Treponema pallidum which causes syphillis

55
Q

Pathogenesis of syphillis

A

Sexually transmitted disease. Multiply at the site of infection and get into the lymph nodes and enter the plasma . They cause :
Primary lesions- in the form of ulcers
After 2-10 weeks the sore vanishes then after another 2-10weeks the Secondary lesions comes by producing rashes
After 2-10 weeks the rashes go
Tertiary stage- granulomatous lesions( masses of immune cells which gather at the site of infection) this makes the individual so weak to the extent that a disease that a normal healthy person can fight the person won’t be able to fight.
There are some people who never shows any of these signs but when they do they go straight to the tertiary stage. There are others who get only the primary or secondary lesion but when they go they never progress so the disease goes dormant
People infected can remain infectious for a period of 5 years.

56
Q

Syphillis is congenital

True or false.

A

True
It can be passed on from mother to child and can cause the death of the child and stillborn issues
Can cause premature birth and the baby will have nervous system abnormalities

Microbiology (9 decks)

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