lesson seven Flashcards
fungi
- nosocomial (hospital acquired) infections and opportunistic infections of immunocompromised
ergosterol
- cell walls of fungi:
1. chitin: stains with calcium-binding agents
2. ergosterol: in cell membrane
amphotericin B
most widely used antifungal drug
3 types of fungi
- molds
- yeasts
- thermally dimorphic
molds
- body of fungus called thallus
- most molds are aerobic only
yeasts
- oval or spherical
- reproduces by budding
- capable of facultative anaerobic growth
yeasts: candida albicans
- attach to epithelial cells as a yeast, but invades deeper tissues by means of pseudohyphae
yeasts: saccharomyces
- yeast ethanol for wine
\carbon dioxide for leavening bread dough- nonpathogenic
yeasts: cryptococcus neoformans
- produces a polysaccharide capsule
thermally dimorphic fungi
- can grow as mold or yeast
- dimorphism: temperature-dependent
- molds: lower temp
yeasts: body temp - not infectious from person to person (the mold form is spread by spores in the air)
sporothrix
- subcutaneous infection
- dimorphic
- fungal spores introduced into wound after trauma
- lymphangitis (inflammation of the walls of lymphatic vessels) common, causes more ulcers as disease progresses
fungal reproduction
- formation of spores
- very different from bacterial endospores
fungal nutrition
- less nutritionally demanding than bacteria
- grow better than bacteria in extreme conditions
- most are aerobic and grow best at 25-30 C
fungal diseases
- mycoses
1. superficial
2. cutaneous
3. systemic
superficial mycoses
- fungal infection along surface of hair shafts and outer layer of skin
m - mild infections: black and white piedra, malassezia furfur
cutaneous mycoses
- fungal infection of deeper layers of the epidermis (athletes foot or ringworm)
- caused by dermatophytes (degrade and use keratin as carbon source)
- clinical diseases are calles tineas
systemic mycoses
- infections in deep tissues
- caused by primary pathogens such as the dimorphic fungi ot opportunistic pathogens such as candida albicans
opportunistic fungal pathogens
- fungi are common cause of infections in immunocompromised individuals
candidiasis
- causes vulvo-vaginal candidiasis and thrush
occurs in newborns, immunocompromised, and people who have been treated with broad spectrum antibiotivs - c.albicans is normal flora in the gut and mouth
antiseptic
disinfectant used on the skin
aseptic technique
use of methods to exclude microorganisms
bactericidal
kills bacteria
bacteriostatic
inhibits growth of bacteria, doesn’t kill
disinfectant
chemical used to destroy many micro-organisms and viruses
fungicide
kills fungi
pasteurization
brief heat treatment used to reduce the number of organisms and to kill pathogenic organisms
sanitization
reduction of the # of organisms to a level that meets public health standards
sterilization
killing of all forms or microorganisms, including inactivating viruses and spores
viricide
inactivates viruses
ventilation
- ultra clean air
- high efficiency particulate air filters
- building standards for correct air flows
- isolation rooms with air locks
positive pressure
air from corridor cannot get into room (immunocompromised)
negative pressure
air from room cannot get into corridor (infectious)
sterilization may be achieved by
a. heat :hot air for 1-2 hours
- autoclaving
- test for effective sterilization using bacillus stearothermophilus spores
b. irradiation (gamma or UV)
c. filtration
d. chemicals
most important consideration that determines efficiency of sterilization
whether or not the object to be sterilized is free of organic matter
spore test
- -based on testing the ability of the autoclaving procedure to totally inactivate bacterial spores
-ampule containing nutrient media and spores of a nonpathogenic bacteria are autoclaved with the object to be sterilized. The ampule is then incubated to test for growth.
-growth (lack of sterilization) is indicated by a change in the pH of the ampule growth media seen as a colour change as the spore has germinated and the growing or vegetative bacteria is using nutrients in the medium and producing acid or alkali compounds
chemical: halogens
- chlorine, iodine
- sterilizes
chemical: aldehydes
- sterilizes
- cidex
chemical: ethylene oxide
- gas that sterilizes
chemical: peroxygens
- strong oxidizer
- sterilizes
most used disinfectants in health care
- halogens: iodine and chlorine
- halogens can sterilize if appropriate amount of active chemical is sued and prolonged time of exposure
alcohols
- kill bacteria and fungi but not endospores and nonenveloped viruses
- mechanism is protein denaturation and disruption of the lipid membranes
- used for skin “degerming”
- not good for treating wounds, as they cause a coagulation
of proteins, creating an environment where the bacteria can grow inside the “scab” - optimal conc. ethanol = 70% (denaturation needs water to
work) - Isopropanol = rubbing alcohol - is better than ethanol: does
not evaporate as fast
antisepsis
for skin
disinfection
for surfaces
