Medically Important Gram Negative Bacteria

Question 1

What kind of bacteria do not retain the crystal violet dye

Answer 1

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

Question 2

Gram negative cell wall is made up what

Answer 2

Outer membrane which is made up ofLPS) and peptidoglycan layer

Question 3

The LPS is made up of

Answer 3

Oligopolysaccharides
Core polysaccharides
Lipid A layer

Question 4

The main component of LPS is

Answer 4

Lipid A

Question 5

What forms the backbone of the Gram negative cell wall

Answer 5

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

Question 6

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

Answer 6

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

Question 7

Gram positive can retain crystal violet dye and Geam

Negative can’t because

Answer 7

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

Question 8

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

Answer 8

True

Question 9

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

Answer 9

True

Question 10

Example of gram negative

Answer 10

Enterobacteriacea

Salmonella

Question 11

Where does enterob live

Answer 11

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

Question 12

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

Answer 12

True

Question 13

Example of opportunistic bacteria

Answer 13

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

Question 14

Example of true pathogens

Answer 14

Some Ecoli strains

Salmonella species

Question 15

Charact of enterob

Answer 15

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)

Question 16

The true pathogens cause diarrheal diseases

True or false

Answer 16

True

Question 17

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

Answer 17

Meningitis
Sepsis
UTI
Pneumonia

Question 18

Explain oxidase test and catalase test for enterobacteriace

Answer 18

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

Question 19

Explain classification based on lactose to classify enterob and give examples

Answer 19

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

Question 20

E. coli cause diarrhea. How is it transmitted

Answer 20

Contaminated food and water

Question 21

Name virulence factors of Ecoli

Answer 21

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

Question 22

Which E. coli cause diarrhea

Answer 22

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)

Question 23

Pathogenesis of E. coli

Answer 23

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

Question 24

Lab diagnosis of E. coli

Answer 24

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

Question 25

Which salmonella species causes diseases

Answer 25

Salmonella typhi | Salmonella enteritidis

Question 26

Salmonella can cause septicemia if found in the blood | True or false

Answer 26

True

Question 27

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

Answer 27

True

Question 28

Pathogenesis of salmonella

Answer 28

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

Question 29

Samples for diagnosis -

Answer 29

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

Question 30

Lab diagnosis of salmonella

Answer 30

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

Question 31

Gram negative cocci example

Answer 31

Neisseria species( Neisseria gonorrhoeae and Neisseria meningitidis

Question 32

Features of Neisseria species specifically | The one that causes gonorrhea and meningitis

Answer 32

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

Question 33

NG causes which diseases

Answer 33

Conjunctivitis Pharyngitis Some anal infections Gonorrhea

Question 34

Virulence factors of NG

Answer 34

Pili Have lipooligosaccharides(toxins) It is sexually transmitted

Question 35

Gono is more common in females than males why

Answer 35

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

Question 36

Pathogenesis of gono

Answer 36

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)

Question 37

Lab diagnosis

Answer 37

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

Question 38

Treatment and prevention

Answer 38

Azithromycin Avoid many sexual partners Ceftriaxone

Question 39

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

Answer 39

True

Question 40

Where does NM affect

Answer 40

Upper respiratory tract infection by airborne droplets

Question 41

Virulence factors of NM

Answer 41

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

Question 42

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

Answer 42

True

Question 43

Pathogenesis of NM

Answer 43

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

Question 44

Samples taken for NM and lab diagnosis

Answer 44

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

Question 45

Treatment and control of NM

Answer 45

Penicillin

Question 46

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

Answer 46

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

Question 47

V cholerae causes

Answer 47

Severe dysentery

Question 48

V culnificus causes? And V para causes?

Answer 48

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

Question 49

If it’s cholera what occurs

Answer 49

Person becomes very dehydrated

Question 50

Pathogenesis for V cholerae

Answer 50

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

Question 51

Lab diagnosis of V cholerae

Answer 51

``` 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 ```

Question 52

Campylobacter character

Answer 52

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

Question 53

Gram negative aerobic rods example and culture and disease it causes

Answer 53

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

Question 54

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

Answer 54

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

Question 55

Pathogenesis of syphillis

Answer 55

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.

Question 56

Syphillis is congenital | True or false.

Answer 56

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