MMI133 Lecture Notes - Lecture 21: Bioterrorism, Penicillin, Arthropod
5 Jul 2018
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Normal Flora = Normal Microbacterium
● animals and humans free of microbes in-utero
● bacteria acquired after birth through mother’s vagina
● organisms colonize through exposure to environment, food, people etc.
Respiratory - Streptococcus sp. (mainly alpha hemolytic)
G.I. - bacteroides fragilis (sensitive to oxygen)
Vagina - lactobacilli
Skin - Staphylococcus epidermidis
Transient Microbiota
● microorganism present on body surfaces temporarily and then disappear
● removed by handwashing
● can be pathogenic or nonpathogenic
● only cause disease in specific conditions
*the human body contains equal or greater amount of bacterial cells to somatic cells
How Infections Get Started
● pathogen finds suitable host
● adheres to host cells and tissues
● penetrates host defenses
● sometimes produce disease without penetrating the body’s defenses (release of toxins)
What Does Normal Flora Do?
Microbial Antagonism
● normal flora prevent overgrowth of harmful microorganisms
● competition for nutrients, cell receptors, pH and available oxygen
● if the balance is upset, then disease can occur
Examples
● normal flora in women (lactobacilli) metabolizes glycogen and lowers pH so that the yeast
Candida albicans cannot grow
● E. coli in intestine produce bacteriocins (inhibit bacteria growth)
●C. difficile growth in large intestine is usually inhibited by normal flora, but broad spectrum
antibiotics can lead to C. difficile takeover and produce toxins
Primary Pathogen - never a part of normal flora
Opportunistic Pathogen - can be a part of the normal flora
Anthrax (Caused by Bacillus Anthracis)
● primary pathogen
● large aerobic gram + bacilli with spores
● disease of herbivores
● found in soil and vegetation
● hardy spores (last more than 50 years)
● no human to human transmission
3 Routes of Infection
1. Inoculation - contact with animal hides (most common)
2. Inhalation - no longer common in the present, but caused woolsorters disease
3. Ingestion - common in carnivores, caused disease in Africa due to the consumption of
contaminated meat
Pathogenesis
● plasmids responsible to acquiring virulence factors (px01 for toxins, px02 for capsule)
● polypeptide capsule (glutamic acid) - anti phagocyte
●inert non metabolizing spores germinate to growing vegetative bacteria when conditions are
right
● growth of bacteria leads to the production of a toxin
3 Components of Toxins
1. PA - Protective Antigen
2. LF - Lethal Factor
3. EF - Edema Factor
Must have PA and either LF or EF for toxicity
Treatment
● must have started early
● penicillin is the drug of choice, but ciprofloxacin used if resistance is detected
● susceptible to many antibiotics (pen, cipro, macrolide, clinda, chloro)
Immunity and Vaccines
● some animals are naturally immune to anthrax
● vaccines based on attenuated organisms, or toxins from culture filtrates
●human vaccine is based on capsule, poor antigenicity/vaccine
● animal vaccines are good for controlling the disease in animals
Smallpox (Poxviridae)
● eradicated in the 1970’s (first eradication of infectious disease)
● DNA virus
● 2 viral strains exist
Orthopoxvirus, Variola Virus = Smallpox
● other orthopox family (vaccinia, monkeypox, cowpox)
● enveloped DNA virus
● vaccinia and variola virus differ only in one antigen and cross react
● immunity to smallpox = immunity to monkeypox
●vaccinia used in smallpox vaccine (safe)
Smallpox Transmission
●mucous membranes in upper respiratory tract
● droplet transmission
Document Summary
Animals and humans free of microbes in-utero. Bacteria acquired after birth through mother"s vagina. Organisms colonize through exposure to environment, food, people etc. Microorganism present on body surfaces temporarily and then disappear. *the human body contains equal or greater amount of bacterial cells to somatic cells. Sometimes produce disease without penetrating the body"s defenses (release of toxins) Normal flora prevent overgrowth of harmful microorganisms. Competition for nutrients, cell receptors, ph and available oxygen. If the balance is upset, then disease can occur. Normal flora in women (lactobacilli) metabolizes glycogen and lowers ph so that the yeast. E. coli in intestine produce bacteriocins (inhibit bacteria growth) C. difficile growth in large intestine is usually inhibited by normal flora, but broad spectrum antibiotics can lead to c. difficile takeover and produce toxins. Primary pathogen - never a part of normal flora. Opportunistic pathogen - can be a part of the normal flora. Large aerobic gram + bacilli with spores.
