micro exam 4 Flashcards
Streptococcus:
- Gram Stain
- Catalase Test
-Hemolysis
- grow on 5% sheep blood agar
- Gram positive
- Catalase (-)
What are the three types of hemolysis produced from Streptococcus ?
- Alpha: Partial lysis of RBC: clear zone
- Beta: Complete Lysis: Green zone
- Gamma: No lysis: No Zone
Species can be differentiated based on differences in the C carbohydrate in the cell wall, How?
Group A, B….
2 potential pathogens
- Streptococcus Pyogenes
- Streptococcus pneumonia
Streptococcus pyogenes are…?
- beta hemolytic
- Group A strep
- > 80 types based on difference in the M
What are the virulence factors of this streptococcus pyogenes?
M protein- attachment/ anti-phagocytic
Capsule- hyaluronic acid
Special surface polysaccharides-
protection from host lysozyme
production of many enzymes and toxins
What are the important sequellae for streptococcus pyogenes?
- rheumatic fever
- glomerulonephritis
Streptococcus pneumonia are…?
- Alpha Hemolytic
- 100 types based on differences in the capsule
- vaccine: capsular material of the most prevalent types
What are the virulence factors of streptococcus pneumonia?
- capsule
- secretion of pneumolysin (toxin)
- impairs immune function
-cytotoxic to pulmonary endothelial cells
Meningitis
- inflammation of the meninges
- 3 layers of connective tissues surrounding the brain and spinal column
Disease process of meningitis…?
- penetrates the respiratory mucosa
- enters blood stream
- crosses the blood- barrier into meninges
three leading cause of bacterial meningitis?
- Haemophilus Influenze
- Streptococcus Pneumonia
- Neisseria Meningitides
Haemophilus influenza ?
- gram (-) coccobacilli
- humans are the only known reservoir
- type b most pathogenic
- Vaccine: capsular material
What are the virulence factors of Haemophilus influenza?
- capsule
- endotoxins
describe the disease process of Haemophilus influenza
- organism infects nasopharynx
- small % cases, enter blood
- cross blood brain barrier into CNS
- in CNS bacterial endotoxins cause release of IL-1 and TNF-alpha; endotoxins weaken blood brain barrier
Neisseria meningitis
- Causes epidemic meningitis
- Gram (-) dipplococcic
- humans are the only known host
- Spread primarily oral secretion/droplets from asymptomatic carriers
- vaccine: capsular materia
what is the virulence factors of Neisseria meningitides?
- polysaccharide capsule
- fimbriae
- invades host cells and grown intracellularly
- release of large amounts of endotoxins
What is the diesease process of Neisseria meningitides ?
- infection begins as nasophayngeal infection
- organism attaches to epithelial cells
- organism invades and grows intracellularly
- small % cases organism enters blood
- infects meninges
Bordetella Pertussis (whooping cough)
- Gram (-) coccobacilli (highly infectious)
- transmission rate of 90%
Virulence factors of Bordetella Pertussis (whooping cough)
- adheres to epithelial cell (trachea)
- exotoxins
1. pertussis toxin
2. tracheal cytotoxin - endotoxins
4 stages of the disease process
- incubation: (7-10 days)
- catarrhal: (sneezing, mild irritating 1-2 weeks)
- spasmodic: (violent cough 1-6 weeks)
- convalescence: (recovery 2 weeks-months)
Vaccine of bordetella pertussis
- DTaP contains “acellular pertussis” fragments of killed bordetella pertussis cells
- after age of 11
- booster shot
Corynebacterium diphtheria?
Stain and shape?
- Gram (+) rods ; line up in parallel (picket fence/Chinese letters)
Virulence factors of Corynebacterium diphtheria
- excretes powerful exotoxin
Results: Kill cells
organism remains localized
but toxin can become systematic
how does exotoxin work in corynebacterium diphtheria?
- B: binding to host cells
- A: Stop proteins synthesis
- stops movement of ribosomes along mRNA
corynebacterium diphtheria vaccine ?
Vaccine: part of the DTaP (‘D’ indicates diphtheria toxoid (inactivated diphtheria toxin)
For treatment anti-toxin can be given. What is an ‘anti-toxin’ ?
Before exotoxin enters vital organs
Mycobacterium, what does myco mean?
filamentous
Acid-fast organism have mycolic acid (waxy lipid) in the cell wall
- How does mycolic acid influence the properties of Mycobacterium?
- Acid-fast
- increases generation time (15-20 hours)
- enables organism to be more resistant to chemicals/drying
- enables organism to resist destruction in macrophages
Diseases caused by acid-fast bacteria are slow chronic diseases: true or false?
true
what are the 2 pathogens of mycobacterium?
- Mycobacterium tuberculosis
- Mycobacterium leprae
Characteristics of Mycobacterium tuberculosis?
- Resistant to chemicals and drying; killed by heat
- Review the disease process of Tb
- Treatment: multiple drugs over an extended period of time because the organism is intracellular
Characteristics of Mycobacterium Leprae?
- Optimal temperature 30°C
- 2 forms of leprosy
a. Tuberculoid (neural); loss of sensation
b. Lepromatous (progressive); disfigurement - Treatment: multiple drugs over an extended period of time
- ‘atypical’ Mycobacterium species: relatively non-pathogenic species
Characteristics of Legionella pneumophila?
a. Gram (-) type cell wall
b. First described in 1976: epidemic in Philadelphia
c. Transmitted by the inhalation of contaminated water
- No evidence of person-person transmission
d. Resistant to normal chlorine levels
e. Review the virulence factors
Mycoplasma Pneumonia
- Smallest organism that can grow and reproduce outside living host cells
- Transmitted by airborne droplets
- Disease affects the upper respiratory tract; mild symptoms
unusual factors of Mycoplasma Pneumonia
- Lack peptidoglycan cell wall
- plasma membrane contains
- highly pleomophic: size 0.1-0.25 um
- Colonies have “fried egg” appearance
The developmental cycle of chlamydia
- elementary features
- reticulate body
- elementary body
how is chlamydia cultured?
- cell culture
- lab animals
- yolk sacs of chick embryos
Three species of culture
- Chlamydia psittaci: birds (respiratory)
-Chlamydia pneumonia: person-person (respiratory)
-Chlamydia trachomatis: (sexually transmitted)
Fungi: Blastomyces dermatitidis
- Endemic in the eastern region of the USA
- Source: moist soil, especially if exposed to animal wastes
Fungi: Histoplasma capsulatum
- Endemic in the central/mid-western area of the USA
- Source: moist soil; bird and bat feces
Fungi: Coccidioides immitis
- Endemic in hot, arid regions; southwest USA
- Source: soil in hot, arid regions
Cryptococcus neoformans
- World-wide distribution
- Yeast cells have a large capsule
- Source: pigeons; moist soil
- In the immunosuppressed, a chronic meningitis can result
Fungi: Pneumocystis jirovreci (carinii)
- World-wide distribution
- Very common
- In the immunosuppressed, a life-threatening pneumonia can result
Common Cold Viruses are DNA or RNA?
RNA
What are the major types of common cold viruses?
- rhinovirus
- parainfluenza
- RSV
- Coronavirus
- Reovirus
rhinovirus
- leading cause of the common cold
- about 160 types; immunity is “type-specific”
- remains viable for hours; single virus can induce cold
Parainfluenza virus
- 4 types
- in children: can cause severe pneumonia and croup
Respiratory Syncytial Virus (RSV)
- Can be very serious in infants
- Vaccine: contains purified viral surface proteins
Coronavirus
- Cause 15-20% common colds
- There have been 3 major pandemics of more virulent strains
Reovirus: what does reo stand for?
respiratory, enteric, orphan
(Coronavirus) What are the three major pandemics of more virulent strains ?
- SARS (2003)
-MERS (2012)
-COVID 19 (2019)
reovirus: viruses be isolated from ___ people and people with disease
Asymptomatic
Influenza Virus: RNA or DNA?
RNA
What is the shape of influenza virus?
8 helical segments of RNA per capsid
What are the three types of influenza?
A, B, C
Is epidemics most frequently caused by major changes in influenza A,B, or C ?
A
What does Influenza A infect?
- humans
- animals
- birds
What are the frequent mutations in Influenza Virus?
- Antigenic Shift
- Antigenic Drift
What is Antigenic Shift?
Major change in spike proteins
What is Antigenic Drift?
Minor change in spike proteins
What are the two viral spikes of Influenza Virus?
- Hemagglutinin
- Neuraminidase
What is Hemagglutinin?
recognition/attachment to host cells
What is Neuraminidase?
breaks down mucous lining; aids budding and release of virus form the host cell
Adenovirus
a. DNA virus
b. First isolated from the adenoids
c. Leading cause of viral conjunctivitis
d. Highly contagious
Mumps Virus: DNA or RNA
RNA; only 1 type
Mumps virus: disease process
- virus becomes systemic and infects the parotid glands
- spread through saliva/nasal secretions
- enters respiratory and lymph nodes (neck)
-virus multiplies - may infect brain, pancreas, ovaries
What is the immunization for mumps ?
MMR vaccine contains live attenuated mumps virus
Rubella Virus (german measles): RNA or DNA
RNA; only 1 type
What is the disease process of rubella?
- spread to respiratory
- enters nasopharynx and inflames throat
- virus replicates in lymph nodes
- Enters blood causes red skin rash
- recovery
True or False: Infection is not devastating to a developing fetus
What is this called ?
False
Congenital Rubella Syndrome
Immunization
MMR vaccine contains live attenuated virus
7) Varicella-Zoster Virus (Chickenpox/Shingles): DNA or RNA?
DNA; in the Herpes family of viruses (HHV-3)
Varicella-Zoster Virus (Chickenpox/Shingles)
- Disease process results in fluid-filled blisters
- Virus remains latent in the host (nerves)
- Recurrence of the virus is called Shingles (painful)
- Vaccine: contains live, attenuated virus
Variola Virus (smallpox): DNA or RNA? Shape?
DNA virus; brick-shaped morphology
Variola Virus (smallpox)
b. Lesions; often left disfiguring scars
c. Worldwide immunization programs eradicated the disease
i. Vaccine contained live, attenuated virus
1. Highly effective
2. No animal reservoirs
ii. Last case 1977
History
- Edward Jenner injected scrapings of cowpox lesions into healthy people in order to build up immune protection to smallpox
- Louis Pasteur coined the term ‘vaccination’ (‘vacca’ means ‘cow’) in honor of Edward Jenner’s work
Oral tract: bacteria
- Alpha-hemolytic Streptococcus
o Gram (+) cocci
what is the disease process of bacteria entering the bloodstream?
- primary portal: mouth
- bacteria can enter bloodstream
-people having dental work
-people having periodontal disease - implicated in subacute bacterial endocarditis
Oral tract: Dental carries
what are the steps of dental carry formations?
- glycoproteins in saliva stick to teeth
- dietary sucrose split into glucose and fructose
- glucose polymerized into dextran
- dental plaque
- sugars are fermented in plaques producing organic acids
- acids dissolve tooth enamel: dental carries
most important species in dental caries ?
streptococcus mutans
What defenses do we have against dental caries?
- flushing action of saliva
- lysozyme
- IgA
How can dental carries be prevented?
- decrease intake of sucrose
- Fluoride
- clean teeth (removal of plaque)
what is a periodontal disease?
inflammation and degeneration of the structures that support the teeth
Define the difference between ‘gingivitis’ and ‘periodontitis’.
gingivitis: infection restricted to gums
periodontitis:
- infection in gums, supporting tissues between teeth
- bone destroyed
Outline the steps involved in periodontitis which can lead to tooth loss.
- healthy gingivae
- gingivitis (toxins in plaque irritate gums)
- periodontal pockets (tooth seperates from gingiva)
- periodontitis
oral tract: Fungi: candida albicans
List the morphology of this organism.
- attaches to epithelial cells as yeast
- produces pseudohyphae
Define the term ‘opportunistic pathogen’.
An opportunistic pathogen is a germ (like bacteria or fungi) that usually doesn’t make healthy people sick, but can cause disease when the body’s defenses are weak, like during illness or injury.
Describe the conditions under which fungi can cause oral thrush.
- major change in normal flora
- disturbance of immune system
- physiological defects
- poor oral hygiene
oral tract: viruses
- These viruses are ds DNA viruses in the Herpes virus family.
- They remain latent in the host.
- These viruses enter the body through the mucous membranes of the mouth
what are the oral tract viruses ?
Herpes simplex (Type 1), Cytomegalovirus (CMV), Epstein-Barr Virus
Herpes Simplex Virus (HHV-1)
- infects
-disease - latency
-recurrence
-treatment
Cytomegalovirus (HHV-5)
- Virus causes nuclear inclusions and swelling - Virus remains latent in T cells and macrophages (white blood cells)
- This virus is more dangerous for immunosuppressed patients and pregnant
women. It can cause congenital defects
Epstein-Barr virus
- This virus causes infectious mononucleosis.
- This virus remains latent in B lymphocytes (white blood cells)
Epstein-Barr virus disease process
- infects oropharynx and paratoid glands
- virus enter blood
- infects b cells
- latency
Explain how infection with the Epstein-Barr virus can lead to transformation and possibly cancer.
- EBV enters cell
- Increase in protooncogene expression
- Uncontrolled proliferation of cells
- Increased chance of chromosomal damage
- Transformation of infected cells
