Portage Microbiology Module 5

Define Pathogenicity

the ability of a microbe to cause disease (yes or no)

Define Virulence

Ease of pathogen to infect host and cause disease

Antigen masking

pathogen covered in host factors to avoid immune detection (hides its antigens)

Antigen mimicry

pathogen’s antigens resemble host molecule’s, helping it evade immune detection

Antigen variation

pathogen switches its antigens, thwarting the mounting immune response

Contact precautions

1) limit patient transport

2) special attention to hand washing

3) gloves at all times

4) gown at all times

5) single use patient equipment

wound/skin infection, resistant infection, infectious diarrhea

Droplet precautions

1) limit patient transport

2) procedural mask at all times

most respiratory infections, influenza, pertusis

Airborne precautions

1) limit patient transport

2) N95 or comparable respiratory

3) place patient in AIIR facility (airborne infection isolation room)

TB, Rubeola (measles), Varicella (chicken pox)

Streptococcus

1. Gram POSITIVE

2. Nonmotile

3. Cocci appearing in pairs or chains

4. Catalase NEGATIVE (facultative anaerobe)

   1. (cannot breakdown peroxides, does not produce bubbles on slide for catalase test)

5. Cultured on BLOOD AGAR

6. Broken down into Lancefield groups (beta hemolytic ones)

Lancefield Groupings

Grouping of beta hemolytic strep that is based on the carbohydrate composition of bacterial antigens located in the cell wall

On a BAP, the strep that grows in an alpha hemolytic way are likely….

S pneumoniae

Lancefield - Group A (what strand we talkin’ and what the clinical conditions are)

S. pyogenes

(strep)

• strep throat (streptococcal pharyngitis)

• cellulitis

• necrotizing fasciitis

Lancefield - Group B (what strand we talkin’ and what the clinical conditions are)

S. agalactiae

(strep)

• blood infections

• pneumonia

• meningitis in newborns

Strep throat (S. pyogenes)

The main characteristics?

• can be transmitted by asymptomatic carriers through resp droplets

• inflamed throat, fever, swollen lymph nodes, exudate (pus)

• primary cause of bacterial pharyngitis

• Treatment: Antibiotics

• Can have many complications such as otitis, sinusitis, pneumonia, and rheumatic fever

What is strep best cultured on?

Blood Agar Plate (BAP)

Explain the autoimmunity caused by S. pyogenes in rheumatic fever

1) S. pyogenes M proteins stimulate antibody production (to M proteins) in the host

2) Antibodies made are “cross-reactive,” meaning they bind to host tissues with proteins similar to M proteins.

3) This initiates an immune response to the host’s own cells

Can cause severe damage to heart valves and more! :0 rut roh

Sepsis or Streptococcal Septicemia or “Blood Poisoning”

Causes? What strains?

Causes: Group B Strep, E. coli, S. aureus, Pseudomonas, and Klebsiella

Sepsis or Streptococcal Septicemia or “Blood Poisoning”

What are the symptoms and treatment?

fever, chills, rapid breathing, increased HR, increased WBCs lymphangitis

Septic shock - tissue damage and organ failure due to decreased BP/perfusion

Treatment: antibiotics and support (IV fluids and oxygen)

Symptoms of Rheumatic fever

1. joint inflammation

2. involuntary jerking movements

3. development of pea-sized nodules beneath the skin

4. reddened areas with raised edges over the surface of the skin

5. heart valve damage (due to antibodies “crossreacting”)

Treatment: Penicillin

Staphylococcus

The main characteristics?

1. Shape: cocci appearing in clusters

2. Gram POSITIVE

3. Nonmotile

4. Catalase POSITIVE (facultative anaerobe)

5. Oxidase NEGATIVE

6. Coagulase POSITIVE

7. Culturing: Selective via bile salts

8. Hemolytic pattern: Beta hemolytic!

Commensal bacteria

Commensal bacteria

Doesn’t harm or hurt host usually/commonly found on humans

What sicknesses is staph associated with?

A lot, but for our purposes, mostly skin and eye infections.

Virulence factors of staph:

(buckle up, this is a long one. There are 8 mentioned)

1) Coagulase - clots blood to help hide bacteria from immune system

2) Catalase - breaks down reactive oxygen species → (breaks down hydrogen peroxide which immune cells need to destroy microbes)

3) Enzymes to break down blood clots (ex: staphylokinase spreads wound bacteria)

4) Pyrogenic Toxin - stimulates fever, rash, and shock

5) Exfoliative toxin - separate upper epidermis from the rest of the skin

6) Hyaluronidase - breaks down connective tissue

7) Hemolysins - lyse RBCs (beta hemolytic activity)

8) Lipases - digest lipids in tissues

S. aureus - what are clinical conditions caused by it?

(staph aureus)

S. aureus

1) Folliculitis

• infected hair follicles that are red, swollen, and pus-filled (called sty if by eye)

• Progression = furuncle (boil) → carbuncle (many together, can cause fever and chills)

2) Scalded Skin Syndrome

• exfoliative toxin from the staph causes skin to redden, blister, and then peel off

• very common in infants

• skin loses its protective layer within 2 days

• treated with erythromycin

3) Impetigo

• reddened, itchy skin with pus-filled vesicles on the face or extremities

• common in 2-5 year olds

• highly contagious

• treated with Penicillin

What’s a big difference between scalded skin syndrome and impetigo?

And while we’re at it, what type of bacteria are they caused by?

STAPH

Lesions in scalded skin syndrome have endotoxin with no bacteria whereas impetigo lesions have bacteria, which can spread if ruptured.

Let’s talk Conjunctivitis.

what’s it caused by and what happens

Caused by STAPH, STREP, or can be VIRAL.

• infection of the conjunctiva, which is the transparent layer of tissue covering the white (sclera) of the eye

• Red/pink color in eye(s); pain; burning; itching; crusting; pus

Ophthalmia neonatorum (explainnnnn)

• Bacterial infection in newborns caused by chlamydia or gonorrhea type bacteria (newborns can be exposed while passing through birth canal)

• can cause permanent eye damage which is why it is common to put ppx antibiotic eyedrops in for newborns

Mycobacterium

The main characteristics?

1. Shape: Bacillus (rod)

2. Gram POSITIVE (though notoriously hard to gram stain)

3. Nonmotile

4. Catalase POSITIVE

5. High G + C (guanine and cytosine

Some more random fun facts about mycobacterium

• virulence = cord factors (tethers bacterial cells together and is toxic to human cells) and drug resistance

• However, NOT a highly virulent disease as 5% of those infected actually develop disease; however, those that develop disease have a 50% chance of death if untreated

• 4th leading cause of death from infection

• commonly used treatment drugs are no longer working

• spread through air mucosal emissions (cough, sneeze)

• must be inhaled to infect

Airborne precautions and standard precautions

Approximately 1/3 of the world’s population is infected with M. tuberculosis…

Say you Acid-Fast a mycobacterium, what will you see?

Bacteria stain RED, and the bacteria will be BLUE

Pathogenesis of Tuberculosis (a mycobacterium)

1. Transmission occurs from inhalation of infected respiratory droplets

2. Alveolar macrophages phagocytose (engulf) bacteria, but it is resistant to lysis

3. Bacteria survive and multiply within macrophages

4. Immune cells are alerted to the foreign antigen and produce a tubercle (a nodular lesion) around the infection

5. Collagen fibers form around tubercle (like scar tissue), and cells in the center die, releasing bacteria and causing caseous necrosis

6. Cells in the middle of the tubercle die; makes cheese-like substance (??)

What super ominous word is tuberculosis sometimes called?

The consumption

What does “latent tuberculosis” mean?

Considered latent TB if the infection stays but the bacteria is contained.

What does secondary or reactive TB mean?

This means the tubercle ruptures and bacteria spread

What does disseminated TB mean?

macrophages bring bacteria to distant organs or tissues

quite deadly

Explain how the Tuberculin skin test works?

**caveat - immunocompromised people can have a smaller enduration indicating a positive result

TB treatment

omg so long

multidrug resistant TB = MDR-TB

extensive drug resistant TB (XDR-TB)can have antibiotic treatment of 2 years

rifampin, osniazid, more.

BCG vaccine

Symptoms of TB

• minor cough

• fever

• difficulty breathing

• fatigue

• weight loss

• chest pain

• wheezing

• coughing up blood

What is the other name for Hansen’s Disease?

(remember it’s a mycobacterium)

What’s super clutch about Leprosy treatment?

All drug treatments for leprosy are provided for free by the WHO

Leprosy (Hansen’s Disease)

main characteristics?

1. Gram POSITIVE

2. Shape: Bacillus

3. Hard to culture, use acid-fast, 30 degrees C in lab

4. Transmission: direct contact via airborne droplets

5. can have a long incubation time and infected people can be asymptomatic for years

6. long term multi-drug therapy similar to TB

7. Two types: Tuberculoid Leprosy and Lepromatous Leprosy

Tuberculoid leprosy

• nonprogressive (immune system does eliminate bacteria)

• skin lesions

• loss of sensation (but can cause permanent nerve damage)

Lepromatous Leprosy

• facial disfigurement

• loss of digits

• skin lesions

Clostridium

main characteristics? What are the 4 main diseases of clostridium we learned about?

• use Endospores as a survival mechanism

1. Botulism - C. botulinum (psst 3 types of this)

2. Tetanus - C. tetani

3. Gas gangrene - C. perfringens

4. Severe diarrhea - C. difficile

What are endospores?

• dormant and metabolically inactive state triggered by environmental stressors

• vegetative cells are when the spore reverts to a growing cell

• difficult to remove from clinical areas

process of making endospores is called sporulation

What causes the symptoms associated with botulism?

caused by C. botulinum’s paralyzing botulinum neurotoxin, which causes flacid paralysis

Infant botulism

(C. botulinum)

• ingestion of endospores via air/dust or food (why infants shouldn’t eat honey

Symptoms: constipation, muscle weakness or paralysis, weak cry, drooping eyelids, tired, feeding difficulty

Foodborne botulism

(C. botulinum)

• toxin is typically consumed from canned foods (usually vegetables)

Symptoms: difficulty swallowing, speaking, or breathing, altered vision, drooping eyelids, nausea/vomiting, paralysis

Wound botulism

(C. botulinum)

• bacteria enter break in skin or from contaminated needle

• common for street drug users

Symptoms: similar to Foodborne botulism, so difficulty swallowing, speaking, or breathing, altered vision, drooping eyelids, nausea/vomiting, paralysis

Tetanus

symptoms caused by?

• C. tetani

• caused by C. tetani that releases the neurotoxin tetanospasmin; which leads to “spastic paralysis” (aka muscles struggle to relax)

What did tetanus used to be called?

Lockjaw

Lockjaw

causes, symptoms

• wounds contaminated by dirt, poop, or saliva or a contaminated object like a nail or needle

• symptoms: muscle spasms, drooling, sweating, irritability, respiratory failure (muscles controlling breathing are affected)

• preventable by vaccine !!

  • It’s a myth that rusty objects themselves cause tetanus

Explain how tetanospasmin works

• the tetanospasmin neurotoxin is taken up into peripheral motor neurons and moves to spinal cord

• this blocks inhibitory neurons from being able to release neurotransmitters that relax muscle cells

Gas Gangrene

(C. perfringens)

how does it work in the body and what are the symptoms

leads to tissue necrosis via the toxin perfringolysin

• perfringolysin perforates or forms pores in cell membranes causing uncontrolled ion fluxes and cell lysis

Symptoms: pain, swelling, fever, darkening skin, odor, drainage, gas bubbles under skin

Risks: shock, coma, death

Gas Gangrene

(C. perfringens)

Treatments?

• antibiotics, debridement or amputation, hyperbaric oxygen therapy

C. Difficile

Main characteristics?

1. Gram POSITIVE

2. Anaerobic

3. Spore-forming

4. Shape: Bacillus

5. Transmission: occurs via the fecal-oral route

6. difficult to remove as its spore form is resistant to antibiotic treatments and disinfecting measures

Standard Precautions and contact precautions

#1 healthcare-acquired infection (HAI)

• causes antibiotic-associated infectious diarrhea and deadly colitis

• opportunistic infection as antibiotic decreases normal flora

Treatment: rehydration, antibiotics, fecal transplants

Legionnaires’

main characteristics?

Legionella

• 90% of all Legionnaires’ infections are due to bacteria Legionella pneumophila

1. Gram NEGATIVE

2. Aerobic

3. Motile (single flagellum)

4. Shape: Coccobacilli

5. Treatment: antibiotics

• Normally found in freshwater lakes and steams, but sometimes manmade water systems

• can only be transmitted through droplets small enough to be breathed in (ex: hot tubs, AC cooling units, humidifiers)

  • Typically in warmer weather months

• Signs and symptoms:

  • fever

  • headache

  • muscle aches

  • coughs

  • SOB

  • atypical pneumonia

• If not treated, kills 20% of patients

What is unique about the legionella pneumophila bacteria?

It is a fastidious bacteria and needs iron salts and amino acid cystine; intracellular parasite; survives in places by living in a host like a protozoa or amoeba.

Plague

main characteristics?

(Yersinia pestis)

1. Gram NEGATIVE

2. Shape: bacillus

3. Facultative anaerobe

The black death por ejemplo.

Plague fun facts

• still here, especially in the Southwest USA

• Rodents, mice, and voles carry bacteria, and fleas act as vectors

• airborne transmission is possible

• all forms of plague have death rate of 50% if gone untreated

• Treatment: antibiotics like streptomycin, tetracycline, fluoroquinolone, gentamicin, and doxycycline

3 Types:

1. Bubonic plague

2. Pneumonic plague

3. Septicemic plague

Bubonic plague

• most common of 3 types

• swollen lymph nodes (called Bubos), high fever

Pneumonic plague

• affects resp system and is highly virulent (deadly; 100% death rate if untreated)

Septicemic plague

• rarest of 3 types

• can cause DIC (disseminated intravascular coagulation)

Explain DIC

DIC - disseminated intravascular coagulation

tiny clots form → they use up clotting factor → hemorrhaging can occur → then susceptible to Clostridium → can lead to gangrene → black death

Anthrax

main characteristics?

(Bacillus anthracis)

1. Gram POSITIVE

2. Aerobic

3. Shape: Bacillus rod-shaped

4. Endospore forming

5. Found in soil or can be zoonotic disease (grazing animals)

3 Types:

1. Cutaneous Anthrax

2. Gastrointestinal Anthrax

3. Pulmonary (inhalation) Anthrax

Cutaneous anthrax

• blister or ulcer with black center (solid nodule of necrotic tissue which can be deadly from exotoxins produced by bacteria)

Gastrointestinal Anthrax

• diarrhea, vomiting, acute inflammation, intestinal hemorrhage

Pulmonary (inhalation) anthrax

• deadly resp infection from toxemia

• fatigue, fevers, cough as early symptoms → progresses to high fever, resp distress because of swelling of resp tract, shock

• mortality rate close to 100% because it is caught too late

  • antibiotics can eliminate the bacteria, but not the toxins released in the bloodstream

• spores highly resistant to disinfectants

• has been used as bioweapon

Lyme Disease

main characteristics?

(Borrelia burgdorferi)

1. Motile

2. Anaerobic

3. Spirochete (corkscrew shaped)

4. negative stain required

• Deer tick is vector (white-footed mouse is reservoir)

• symptoms: fever, chills, headache, muscle/joint pain, erythema migrans (bullseye)

Complications of lyme disease?

• irregular heartbeat

• myocarditis

• facial palsy

• balance issues

• mood disturbances

• schizophrenia-like illness

• bullseye

What percentage of Americans are infected with an STI right now?

1/5

Gonorrhea

main characteristics?

(Neisseria gonorrhoeae)

1. Gram NEGATIVE

2. Shape: diplococcic

3. fastidious bacteria (grows best on chocolate agar)

4. Virulence: pili (protein filament appendages) for adhesion, ciliated, intracellular (live in host cells to avoid immune system attack), and bacterial capsules to evade immune system

5. Treatment: antibioticsssssssssss per ushe

Female Symptoms:

• asymptomatic, painful urination, increased vaginal discharge, bleeding/spotting between periods or after sex, complication of pelvic inflammatory disease (bacteria hitchhike on semen and go to the fallopian tubes)

Male Symptoms:

• asymptomatic, painful urination, urethral discharge

Neonate Symptoms:

• eye infections (ophthalmia neonatorum), sepsis

Syphilis

main characteristics?

(Treponema pallidium)

1. Gram NEGATIVE

2. Spirochete (corkscrew shape)

3. best visualized by dark field microscope

4. 4 distinct stages

5. Treatment: Penicillin

What are the 4 stages of Syphilis?

1) Primary - sore (chancres) develop at initial infection site

2) Secondary - disseminated red/brown rash which may be accompanied by fever, rash, headache, swollen lymph nodes

3) Latent - symptoms disappear, and the patient is still asymptomatic

4) Late (Tertiary) - gumma lesions on skin and bones, organ damage, neurological symptoms

Chlamydia

main characteristics?

(C. trachomatis)

1. Gram NEGATIVE

2. Nonmotile

3. Shape: Bacillus rod

4. Obligate parasite! aka replicates inside the host cell

5. cannot grow in agar^^

6. Treatment: antibiotics

What percentage of people is staph found in and asymptomatic?

30%

Is there a cure for tetanus?

No, but there is a vaccine