Human Microbes Interaction Flashcards
Colonization
-The PROCESS of growth of a microorganism after it has entered the host tissue
Host
-an organism that harbors a parasite
Parasite
-An organism that grows in or on a host AND causes damage (a negative outcome, some worse than others)
Infection
-the OUTCOME of growth of organisms in a host (not necessarily detrimental) colonization is the PROCESS, and Infection is the OUTCOME
Disease
-An injury or impaired function to the host
Pathogen
-A microbial parasite that causes disease
Obligate pathogen
-Always causes a disease and generally do not survive long outside the host
opportunistic pathogen
-Do not normally cause disease and do not cause disease in a host with normal resistance properties, but can in an impaired host
Pathogenicity
-The ability of an organism to cause disease (Some E. Coli strains never cause disease, some do)
Virulence
-The DEGREE of pathogenicity of an organism (Some E. Coli strains cause only mild disease, some cause life-threatening disease)
How is the normal human microflora beneficial?
-Competes with pathogens for space and nutrients (pathogen exclusion)
-produces products that inhibit pathogens (kills them)
-Synthesize vitamins for host
-Stimulate development of Immune system (germ free mice -> poorly developed immune systems)
What sites on the human body are colonized by normal microflora?
-Skin
-Oral Cavity
-Lower Respiratory Tract
-Urethra
What type of organisms are found on the skin?
-Gram + Cocci (staphylococcus) on skin, and Propionibacterium in follicles
-resistant to salts and oils
What type of organisms are found in the oral cavity?
-Gram positive cocci in mouth and throat
-Staph and Strep
-Streptococcus mutans (caries), anaerobes in gingival and plaque
What type of organisms are found in the lower respiratory tract?
-Bronchi and lungs are relatively sterile
What type of organisms are found in the urethra?
-Gram-facultative organisms such as E. Coli
-Upper urethra and bladder are relatively sterile.
-Vagina is staph and strep, except during fertile years, pH is lower and then lactobacilli predominate
What are some of the more important Genera of bacteria in the human gastrointestinal tract and why are they important?
-Helicobacter = ulcers
-Bacteroides = most abundant
-Escherichia = fecal contamination indicator
-Methanobrevibactor is rare archaea associated with humans
-clostridium difficile
What does C. difficile become a problem?
-Following antibiotics treatment that disrupts the normal flora and allows C. diff to become a predominant organism
-Some strains have a high antibiotic resistance and high levels of toxin production
Why do patients often get recurrences of C. difficile infections?
-Spores are resistant to antibiotics
-Spores are hard to remove from hospitals
-It takes time to regenerate flora that can exclude the C. diff from re-growing to dominant population.
Regions of the body in direct contact with exterior
-Nose
-mouth
-respiratory tract
-alimentary canal
-female genital tract
-urinary tract (male and female)
Where is normal flora found?
-almost all skin surfaces and mucus membrane surface are colonized by microflora
How many human and bacterial cells are in the body?
-Approximately 10^13 human cells in your body
-Approximately 10^14 bacteria cells in/on your body
-human: bacteria = 1:100
Microflora of the skin
-The first line of defense: dry, acidic, and salty
-Flors is dependent upon weather, age and, hygiene
-Anaerobes (Propionibacterium acnes) grow in hair follicles and sebaceous fluids
-Skin flora is dominated by gram-positive cocci
Layers of the skin with a hair follicle
-dead layer or epidermis = dead and sloughs off
-dermis with duct and sebaceous gland (makes oil)
-Subcutaneous = has apocrine sweat gland, live cell, if get here it will cause infection
Residents of the upper respiratory tract/oral cavaity
-Transient organisms trapped during breathing and expelled with nasal secretions
-Dental caries and acid (fermentation products) = sugar -> lactic acid
-Streptococcus mutans utilizes sucrose to produce a polysaccharide for adherence to tooth surface
In the upper respiratory tract/oral cavity do anaerobes outnumber aerobes?
-Yes, anaerobes outnumber aerobes due to gingival and plaque organisms
-Fusobacterium and Actinomyces
-Plaque = biofilm
Lower Respiratory Tract
-Trachea, bronchi, and lungs have few bacteria
-Airborne/inhaled organisms trapped in upper regions removed by ciliated colurma epithelium cells (line larynx)
-Other clearance mechanisms include cough reflex (physical) and alveolar macrophages (kill)
Physiological processes of the Gastrointestinal (GI) tract: Stomach
-stomach secretion of acid (HCL) digestion of macronutrients, pH 2 (kills most bacteria)
Physiological processes of the Gastrointestinal (GI) tract: Small Intestine
-continued digestion absorption of monosaccharides, amino acids, fatty acids, and water
-pH 4-5
-most nutrient uptake in duodenum and jejunum
Physiological processes of the Gastrointestinal (GI) tract: Large intestine
-absorption of bile acids, vitamin b12
-pH 7
-absorb water
-colon: packed full of bacteria
Resident Microflora of the Gastrointestinal (GI) tract
-O2
-changes in oxygen availability and pH
What is the number one cause of bacterial death in children?
-diarrhea
Disruption of the Gastrointestinal Microflora
-The use of antibiotics can disrupt the normal flora, allowing less desirable, and potentially pathogenic, species to become dominant
-A major problem in hospital is now Clostridium difficile- associated disease (CDAD)
What is C. difficile?
-is a normal gut inhabitant for most people
-post-surgical and chemotherapy patients heavily treated with antibiotics often develop CDAD
-hospital C. difficile strains tend to produce more toxins and to be more antibiotic resistant
What are treatments for C. difficile?
-Probiotics
-Better treatment is fecal transplant therapy
=90%-95% effective
Biochemical/metabolic contribution of intestinal microorganisms
-vitamin synthesis = vitamin K and B12 (most vitamin K is from bacteria)
-Amino acid synthesis = glutamate, lysine, tryptophan
-odor production=butyric acid
-Organic acid production = acetic, butyric acid (interact with immune system)
-Glycosidase reactions = B- and alpha-
Biochemical/metabolic contribution of intestinal microorganisms: gas production
-CO2
-H2
-CH4 (methane)
Biochemical/metabolic contribution of intestinal microorganisms: Steroid metabolism
-bile acids
- dehydroxylates, oxidized or reduced steroids (carcinogenic)
Why do beans cause gas?
-they have sugars we can not break down
-dumped into large intestine, fermented into gas
Genitourinary flora
-the flushing action of urine keeps bladder clean
-Anterior urethra and vagina can become colonized with gram-negative, facultative organisms (proteus mirabilis = UTI)
What does estrogen do in the Genitourinary flora
-estrogen production alters the pH and flora of vagina
-pre-puberty and post menopause has staphylococcus, streptococcus, and enterobacteria
Why are females more likely to get an UTI?
-Their urethra is closer to the anus
-this allows for bacteria from the colon to infect the urethra
-the bacteria that causes UTIs does not cause disease in the digestive system
