Human Diseases Caused by Bacteria Flashcards
Airborne Bacterial Pathogens
T/F: Of the bacterial species, most are pathogenic to humans.
FALSE – only few are pathogenic to humans
Airborne Bacterial Pathogens
What system do most bacterial diseases involve?
respiratory system
- some can disseminate into the bloodstream, particularly in elderly and immunocompromised
Diptheria-Exotoxin Mechanism
What is it caused by?
caused by Corynebacterium bacteria
Diptheria-Exotoxin Mechanism
Describe diptheria-exotoxins mechanism.
- gram-positive
- very resistant to drying
- lysogenized strains produce an exotoxin that inhibits protein synthesis and is responsible for pathogenesis
Diptheria-Exotoxin Mechanism
How is it transmitted?
airborne transmission by nasopharyngeal secretions
Diptheria-Exotoxin Mechanism
What increases likelihood of transmission?
crowding
Diptheria
Who is diptheria typically seen in?
usually observed in individuals >30 years old with weakend immunity to diptheria toxin and living in tropical areas
Diptheria
How is diptheria diagnoses?
- pseudomembrane in throat
- bacterial culture
Diptheria
How is diptheria treated, prevented, and controlled?
- antibiotic therapy
- toxoid vaccine
Mycobacterium Infection
Where does these microorganisms live?
in soil, water, and house dust
Mycobacterium Infection
Mycobacterium causes a number of human infections that are hard to treat. Why is this true?
- mycolic acid in cell wall is protective waxy material that is acid fast
- resistant to penetration of some antibiotics
Mycobacterium Infection
MAC
M. avium complex
Mycobacterium Infection
Describe MAC.
- normal inhabitatns of soil and water
- infect variety of insects, birds, and other animals
Mycobacterium Infection
What are common allowances of mycobacterial infection in the US?
respiratory and gastrointestinal tracts have been proposed as portals of entry
Tuberculosis (TB)
What causes TB?
mycobacterium tuberculosis (Mtb), M. bovis, M africanum
Tuberculosis (TB)
Why is Tb considered a global health problem?
about 1/3 of world’s population is infected
Tuberculosis (TB)
What are some of the commonly infected groups?
- US homeless
- elderly
- malnourished
- alcoholic males
- minorities
- immigrants
- prison populations
- native americans
Tuberculosis (TB)
Does bacteria produce typical virulence factors?
no
Tuberculosis (TB)
What survival tactics do bacteria use?
unique lipids in the cell envelope are toxic to eukaryotic cells and create a barrier that protects the bacteria
Tuberculosis (TB)
How is it transmitted?
- majority is person to person spread of droplet nuclei in respiratory tract
- also transmitted from infected animals and their products
- reactivation of old, dormant infection
Tuberculosis (TB)
What is the rate of progression?
disease develops slowly
TB Course of Disease
Lung macrophages that have phagocytosed Mtb often die in the attempt to kill bacteria. What is the result of this?
tubercles formation
TB Course of Disease
What are tubercles?
composed of bacteria, macrophages, T cells, and human proteins
TB Course of Disease
What are changes over time in tubercles?
- caseous lesion
- Ghon complexes
- tuberculous cavities
TB Course of Disease
describe the appearance of caseous lesions.
cheese-like
TB Course of Disease
Ghon complexes
calcified caseous lesion
TB Course of Disease
tuberculous cavities
- tubercle liquefies, forms air-filled cavity from which bacteria can spread
- spreading is called miliary tb; also called reactivation tb because bacteria reactivated at intial infection site
Infection with Mtb
What is the basis tuberculin skin test?
development of cell-mediated immunity (sensitized T cells)
Infection with Mtb
How long is the incubation period?
4 to 12 weeks
Infection with Mtb
What are the symptoms?
- fever, fatigue, night sweats, and weight loss
- cough: characteristic of pulmonary involvement; may result in epectoration of bloody sputum
Infection with Mtb
How is it diagnosed?
- observation of acid-fast bacteria
- chest X-ray, Mantoux, or tuberculin skin test
- DNA-based tests
Streptococcal Diseases
What is it caused by?
strep, group of gram-positive bacteria
Streptococcal Diseases
sterptococcus pyogenes
one of the most important pathogens;
- group A streptoccoci (GAS)
- beta-hemolytic streptococci
Streptococcal Diseases
What are the virulence factors?
- extracellular enzymes that break down host molecules
- streptokinases: dissolve clots
- streptolysin O and S: kill host leukocytes
- capsules and M protein, which limit phagocytosis
Streptococcal Pharyngitis
What is the common name of this infection?
strep throat
Streptococcal Pharyngitis
How is it transmitted?
droplets of saliva or nasal secretions