Lecture 8. Microbes and Disease Flashcards
What parts of the respiratory tract are usually sterile?
Trachea, bronchus and alveoli
How many bacteria are there in the stomach?
10³ - 10⁵/g
How many bacteria are there in the duodenum?
10⁵ - 10⁸/g
How many bacteria are there in the ileum?
10⁸ - 10¹⁰/g
How many bacteria are there in the colon?
> 10¹⁰/g
What is the mircobiome?
The ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space
What are the suggested health benefits of the human microbiome?
Shield body tissues against invasion of ‘bad bugs’
Production of vitamins by bacteria (e.g. vitamin K in gut)
What conditions is the microbiome implicated in (not proven)?
Obesity
Type 1 Diabetes
Crohn’s disease
Irritable bowel syndrome
Colon cancer
What determines virulence?
Factors that aid in adhesion to and entry into cells,
antiphagocytic activity, immune system evasion and production of toxins
What are examples of conventional virulence factors?
Bacterial toxins, adhesins, cell surface carbohydrates and capsules, secreted hydrolytic enzymes, LPS
What can virulence factors be?
Plasmid or phage encoded
What does the α-toxin of S. aureus do?
Creates pores
What are ‘new’ bacterial pathogens?
Pathogens not previously been known as pathogens
Includes bacteria with a wide environmental distribution, that can cause infections in the immuno-compromised
Such opportunistic pathogens are increasingly important in causing outbreaks in hospitals
What is an example of a ‘new’ pathogen species?
Burkholderia cepacia, highly versatile bacteria mainly associated with plants and soil
What was the first modern antibiotic?
Arsphenamine (Salvarasan) in 1909 which was an arsenic-based treatment for syphilis
What was the first antibiotic derived from a natural source?
Penicillin 1928
What are the five major types of antibiotic?
β-lactams
Macrolides
Fluoroquinolones
Tetracyclines
Aminoglycosides
What mechanisms cause resistance in penicillins?
Reduced permeability and inactivation
What mechanism causes resistance in aminoglycosides?
Inactivation
What mechanism causes resistance in macrolides?
Target alteration
What mechanism causes resistance in sulfonamides?
New resistance pathway
What mechanism causes resistance in tetracyclines and erythromycin?
Efflux
What are the solutions to antibiotic and antimicrobial resistance?
New drugs derived from old drugs
New targets (the cell wall, new target proteins)
Drug combinations and augmentative compounds
When was the first vaccination?
1796 Edward Jenner vaccine against smallpox
What was the first proof that attenuated (weakened) vaccination worked?
1879 Louis Pasteur with Pasteurella multocida (chicken cholera)
What does Clostridium tetani neurotoxin cause?
Tetanus
What are the symptoms of tetanus?
Over-activity of motor neurons causing muscle spasms ‘lockjaw’
How is tetanus prevented?
Because even a lethal dose of toxin is too small to raise immunity, formalin (an inactivated toxin) is used
3-4 doses provide ~100% protection that lasts ~10 years
What is meningitis?
Inflammation of the protective membranes that cover the brain and spinal cord
What causes 75% of acute bacterial meningitis cases?
Haemophilus influenzae
Streptococcus pneumoniae (pneumococcus)
Neisseria meningitidis (meningococcus)
What is Haemophilus influenzae?
Gram-negative coccobacillus
Non-encapsulated strains carried asymptomatically in urinary tract
How many serotypes of Heamophilus influenzae are there?
Six serotypes (a-f)
What serotype is responsible for 90% of invasive infections of Haemophilus influenzae?
Serotype b (Hib)
How is Hib treated?
There are three conjugated Hib vaccines, all exhibit >90% efficacy
