Medically Important Gram Negative Bacteria Flashcards
What kind of bacteria do not retain the crystal violet dye
Gram negative so they show red or pink color due to the safranin
This is based on their cell component
Gram negative cell wall is made up what
Outer membrane which is made up ofLPS) and peptidoglycan layer
The LPS is made up of
Oligopolysaccharides
Core polysaccharides
Lipid A layer
The main component of LPS is
Lipid A
What forms the backbone of the Gram negative cell wall
Lipoproteins which transport lipids and phospholipids which serve as a barrier for molecule movement
What is the surface layer and where is it attached to in Gram negative and positive bacteria
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
Gram positive can retain crystal violet dye and Geam
Negative can’t because
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
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
True
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
True
Example of gram negative
Enterobacteriacea
Salmonella
Where does enterob live
In the colon and are facultative anaerobes(can grow in the presence or absence of oxygen h
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
True
Example of opportunistic bacteria
Escherichia coli
Klebsiella pneumoniae
Enterobacter, Serratiaand Citrobacter (collectively called the coliform bacilli) and Proteus
Example of true pathogens
Some Ecoli strains
Salmonella species
Charact of enterob
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)
The true pathogens cause diarrheal diseases
True or false
True
Normal flora can take advantage of a weakened immune system. Which diseases do they cause when they do that
Meningitis
Sepsis
UTI
Pneumonia
Explain oxidase test and catalase test for enterobacteriace
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
Explain classification based on lactose to classify enterob and give examples
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
E. coli cause diarrhea. How is it transmitted
Contaminated food and water
Name virulence factors of Ecoli
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
Which E. coli cause diarrhea
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)
Pathogenesis of E. coli
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
Lab diagnosis of E. coli
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
Which salmonella species causes diseases
Salmonella typhi
Salmonella enteritidis
Salmonella can cause septicemia if found in the blood
True or false
True
It’s either salmonella causes typhoid,septicemia or gastro enteritis( inflammation of stomach and intestines) true or false
True
Pathogenesis of salmonella
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
Samples for diagnosis -
Enteric fever- blood, bone marrow, urine
Diarrhea- stool
Food poisoning- stool, vomitus
Septicemia- blood
Lab diagnosis of salmonella
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
Gram negative cocci example
Neisseria species( Neisseria gonorrhoeae and Neisseria meningitidis
Features of Neisseria species specifically
The one that causes gonorrhea and meningitis
Are non motile so no flagella
Shape is diplococcus
Are Oxidase and catalase positive
Both ferment glucose
NG causes which diseases
Conjunctivitis
Pharyngitis
Some anal infections
Gonorrhea
Virulence factors of NG
Pili
Have lipooligosaccharides(toxins)
It is sexually transmitted
Gono is more common in females than males why
Females sexual organ has large surface area to attract more secretions so the infection spreads faster
Pathogenesis of gono
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)
Lab diagnosis
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
Treatment and prevention
Azithromycin
Avoid many sexual partners
Ceftriaxone
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
True
Where does NM affect
Upper respiratory tract infection by airborne droplets
Virulence factors of NM
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
Maltose fermentation test is used to distinguish between NG and NM true or false
True
Pathogenesis of NM
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
Samples taken for NM and lab diagnosis
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
Treatment and control of NM
Penicillin
Example of facultative( it lives with or without a host) rods
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
V cholerae causes
Severe dysentery
V culnificus causes? And V para causes?
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
If it’s cholera what occurs
Person becomes very dehydrated
Pathogenesis for V cholerae
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
Lab diagnosis of V cholerae
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
Campylobacter character
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
Gram negative aerobic rods example and culture and disease it causes
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
Gram negative coccobacilli . Give four examples along w characteristics, virulence factors
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
Pathogenesis of syphillis
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.
Syphillis is congenital
True or false.
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
