Microbiology and immunology midterm 2

What type of gram Bacilli is the spore forming rods

gram postive

What are the two types of spore forming rods

Bacillus and Clostridium

What type of toxins do they release

potent exotoxins that cause disease

What is Bacillus anthracis the causative agent of

Anthrax

What is unique about Bacillus anthracis

it has a unique protein capsule that gives it extra protection from complement proteins

What condition does it grow in 

in aerobic growth conditions and the spores are very stable, resistant to heat 

what do the spores do

they germinate and can cause clinical manifestation

how do humans come in contact with it

they are exposed to spores usually through contact with animals or soil and inhaling those spores

How many plasmids does it have

2( PxO1 and pXO2)

Where is the conditions found for them to grow

in the respiratory system

What are the three seperate proteins the exotoxin is composed of

edema factor(EE)

Protective antigen

Lethal Factor

separately proteins are not toxic, but combined they are lethal

which encoded plasmid encodes for capsule genes 

pXO2 but both plasmids required for virulence 

Is there a treatment and vaccine for this virus

yes for both and rapid treatment is essential

Which Bacci causes food poisoning when spores enter food product when not heated properly

Bacillus cereus

What type of exotoxin is responsible for illness

Enterotoxin

What are the two types of enterotoxins it can produce 

Heat labile: nausea, abdominal pain, diarrhea Heat stable: severe nausea and vomiting, short incubation 

Is there a treatment and vaccine and are they useful?

Yes there is a treatment but it is useless against preformed toxins

and there is no vaccine

What differentiates Clostridium Bacilli from other spore forming bacilli

it is an Anaerobic spore- forming bacilli

What illnesses does it cause 

Botulism, tetanus, gas gangrene and pseudomembranous colitis 

What are the different types of Clostridium

• Clostridium botulinum

• Clostridium tetani

• Clostridium perfringens

• Clostridium difficile

what causes Clostridium botulinum

rapidly fatal food poisoning from lethal neurotoxin

what does this neurotoxin do

it blocks ach release in autonomic system and causes bilateral cranial nerve palsies, double vision, Afebrils, trouble swallowing

What else does it do

causes respiratory paralysis which leads to death 

is there a treatment

yes and properly cooking destroys spores

Infant botulism

honey contamination with spores

they germinate and bacteria colonizes intestine leads to floppy baby syndrome 

What causes Clostridium tetani

stepping in anything with spores punctures skin and wound would provide anaerobic environment(ex rusty nail)

What type of toxin does it release

exotoxin: tetanospasmin

What are the clinical manifestations

➢Sustained contraction of skeletal muscles

➢Severe muscle spasms (lock jaw); high

mortality at this stage

tetanus 

is there a vaccine/ treatment 

yes ➢ Booster (inactivated toxoid) given every 10 years

What does Clostridium perfringens cause

Gas gangrene

What are the two classes of infection 

➢ 2 classes of infection:

(i) Wound infection/cellulitis

-necrotic skin exposed to bacteria, damage to local

tissues; skin feels moist, spongy, with ‘crackly’ pockets

(ii) Clostridial myonecrosis

-bacteria inoculated from trauma into muscles; exotoxin

secretion destroys adjacent muscles; as muscles degrade get black fluid excreted from skin

is there a treatment 

yes but FATAL unless treated with oxygen, antibiotics (penicillin) and removal of damaged tissue

what can cause Clostridium difficile

Causes antibiotic-associated pseudomembranous colitis

➢ Overuse of broad-spectrum antibiotics destroys normal intestinal flora

➢ Infects colon and releases exotoxins

➢ Toxin A: diarrhea

➢ Toxin B: cytotoxic to colon cells

what are some symptoms

Symptoms: severe diarrhea, abdominal cramping, fever

➢ Possible cause of diarrhea in patients on antibiotics

what are some treatments 

treatment

➢discontinue antibiotic treatment

What are the two non spore forming gram positive rods

• Listeria monocytogenes

• Corynebacterium diptheriae

What is Listeria monocytogenes the causative agent of

Causative agent of listeriosis; immunocompromised are at high risk

Where is it found

➢ Found in foods such as soft cheeses, unpasteurized milk, cold cuts, pâté

What type of temperature does it survive in? 

PSYCHROPHILE survives in refrigerator and it is a ➢ Facultative intracellular aerobe

what are some of its symptoms and is there a treatment

➢General malaise, diarrhea, meningitis, septicaemia,still-birth/abortions

➢ Crosses 3 protective barriers (blood-brain, GI and feto-placental)

➢ Treatment: ampicillin or trimethoprim-sulfamethoxazole

What is Corynebacterium diptheriae the causative agent of 

Causative agent of diphtheria

where does it colonize 

Colonization of pharynx and release of exotoxins into bloodstream

➢ Exotoxin damages heart and neural cells

is there a treatment and vaccine 

yes and the vaccine is (DPT vaccine

What are the classes of gram negative bacilli

Enterics- all have endotoxins 

where are they found 

Found as part of normal intestinal flora BUT can also cause disease

Organisms are divided into groups based on biochemical and antigenic properties

what are the three types of surface antigens that call gram negative bacilli will always have

Variable O-antigen: outermost layer of LPS

• Changes between enterics

• K-antigen: covers the O-antigen- protein capsule

• H-antigen: flagellar sub-unit

• Only in motile bacteria

what are some diseases caused by enterics

1) Cause diarrhoea with various complications and other infections

• EXOTOXIN release causes diarrhoea; ENTEROTOXIN causes fluid/electrolyte loss

• Watery diarrhoea, NO FEVER

• Vibrio cholera

 2) Diarrhea with intestinal cell invasion

• Bacterial virulence factors allow binding and invasion of cells bloody stools

• Toxin release destroys cells

• Fever response

• Shigella,

3) Diarrhea with invasion of lymph nodes and bloodstream

• Abdominal pain with diarrhoea containing white and red cells

• Fever, headache, increased white cell counts

what are the two types of Salmonellae

➢ Enterocolitis (tummy problems):

➢ S. enterica serovar Enteritidis

➢ S. enterica serovar Typhimurium

➢ Typhoid (enteric) fever:

➢ S. enterica serovar Typhi

➢ S. enterica serovar Paratyphi

Enterocolitis

• Pathogenesis depends on:

• Dose of ingested organism (min 105)

• Immune status of host

• Virulence of strain

what are the symptoms of Entercolitis and how do you get it

Symptoms

• Nausea, vomiting, profuse diarrhoea, abdominal pain

• Fever, chills, headache, myalgia

• Septicaemia Rare

S. enterica serovar Enteritidis

Enterocolitis

• Ingestion of contaminated food →

• Poultry, eggs, meat and milk

• Person to person spread

• Most cases occur at home

• Antibiotics NOT RECOMMENDED WHY?- some strains grow better with antibiotics 

Enteric Fever (AKA typhoid and paratyphoid)

Enteric fever: generalized infection; bacterial

multiplication in lymphoid tissue

ulceration,

• Necrosis of intestinal lymphoid tissue

haemorrhage, perforation

• Convalescent carriers: excrete bacteria for 3 months

• Chronic carriers (1-2%): excrete bacteria for at least 6

months, sometimes life long

Is there treatment for enteric fever

yes and there is a vaccine but only effective for small bacterial load

what is the nomenclature for exam purposes

Stomach problems:

- Salmonella enteritidis or Salmonella typhimurium

Typhoid fever (or enteric fever):

- Salmonella typhi or Salmonella paratyphi

Escherichia coli

Most numerous aerobic bacteria of normal gut flora

• Lactose fermenting

• Pathogenic to other parts of the body

• responsible for 85% of bacteriuria

What are some symptoms of E. coli to Gastroenteritis

Enterotoxigenic E. coli

• Infant diarrhoea (developing countries)

• Traveller’s diarrhoea

• Enterotoxins

• Enteroinvasive E. coli

• Symptoms similar to shigellosis

Enteropathogenic E. coli

why do people get Traveller’s diarrhoea

because it is a different serotype of E.coli of the O antigen

What can cause it 

• E. coli O157:H7

• Haemorrhagic colitis- flagella antigen can kill or shut down kidneys 

• Hamburger disease

• Proper handling of food, safe preparation and

proper cooking practices are essential to prevent

illness

• E. coli is also implicated in neonatal meningitis and

nosocomial urinary and wound infection

what can • E. coli O157:H7 cause 

hemolytic uremic symdrome 

what are some symptoms of Shigellae

Cause acute diarrhoea with mucus, pus and blood

• S. dysenteriae:

• SEVERE illness: watery diarrhoea, cramps, fever

• Infection from SMALL numbers of organism

• Most commonly seen in children; poor sanitation and

crowding

what are some treatments

Prevention by safe handling of food, treatment of water, safe

disposal of sewage

• NO VACCINE

what are some symptoms of Vibrio cholerae

Causes cholera: acute gastrointestinal illness

• Profuse watery diarrhoea, cramps and vomiting

• Can lead to severe dehydration and death if

untreated

• Lack of clean drinking water!

• Mainly water-borne

• Massive (10-15 litres per day) loss

what does the toxin do

Enterotoxin binds cells in small intestine

• Cells secrete chlorides,

Na+ absorption decreases

• Water accumulates in gut

watery diarrhoea

Campylobacter

• Major cause of human enteritis

• Normal flora in birds and domestic animals

• Symptoms: fever, abdominal pain, bloody diarrhoea

• Maybe one cause of traveller’s diarrhoea

it is also microaerophilc meaning it needs a specific amount of oxygen to live 

is Pseudomonas considered an enteric

no but it is still gram negative

what is it considered

Opportunistic pathogen

• Found in many moist habitats and water

• Source of infection can be humidifiers etc.

is there treatment?

Treatment is difficult because all Pseudomonas

sp. are resistant to many antibiotics!!!!

Pseudomonas aeruginosa

Respiratory pathogen in cystic fibrosis

patients

• Infections in lesions of burn patients

Pseudomonas cepacia

Common contaminant of saline solutions and water

• Able to multiply in low nutrient environment

• Respiratory pathogen of cystic fibrosis patients

also if you see purple or smell grape its there

Haemophilus influenzae

Part of normal nasopharyngeal flora in many adults and

children

• Causes invasive infections of young children

• Meningitis, pneumonia, joint infections

• Development of vaccine, now used

routinely, decreased the number of cases in Canada

• Can cause increased bronchial inflammation in patients already having chronic bronchitis

Cronobacter spp.

• Can cause nosocomial infections

• Wound infections, pneumonia, bacteremia

linked to infant illness from powdered infant formula

low birth weight infants

Helicobacter pylori

Microaerophillic, spiral bacilli

• Most common cause of stomach ulcers

• Urease: protection form low pH

• Triple therapy treatment: antibiotics and H+ pump inhibitors

Bordetella pertussis( gram negative also not enteric) 

Whooping cough VIOLENT COUGH

• 4 Virulence Factors

• Pertussis toxin (A-B)

• Extra cytoplasmic adenylate cyclase (weakens host defense)

• Filamentous hemagglutinin (bronchial attachment and exotoxoin

release)

• Tracheal cytotoxin (destroys ciliated cells poor clearance of

mucous and bacteria)

is there a vaccine

yes Prevention: vaccination with heat-killed organism

Legionella pneumophila

Causes Legionnaires disease

• Opportunistic pathogen

• May cause severe pneumonia

• Grows in water and is found in shower

heads, water tanks, air cooling/heating

tanks

• Exposure is by aerosol and there is NO

person-to-person transmission