Bacteria Flashcards
What color stain does gram - bacteria appear?
Pink or red
Colorless until stained with safranin
Gram stain + organisms appear what color under the microscopic
Dark violet, purple or blue.
Gram + bacteria
What is the purpose of gram staining?
To determine type of media to used for culture
Gram stain reaction, cell shape and arrangement
What color does acid fast organisms stain?
Retain carbolfuchsin
Turn red
Used for mycobacterium
What is the zone of inhibition?
Disks are impregnates with antibiotics and put on the plate which has bacteria on it. If the bacteria grows up to the disk the antibiotic is resistant. If growth is inhibited, the abx is sensitive.
What bacteria could be resistant to b Lactamase?
Hemophilia influenza, news seeks gonorrhoeae, staph coccyx, Pseudomonas.
What is wet mount diagnostic test used for?
Fresh clinical specimens Sputum for fungus Stool for larvae CSF a for cryptococcosis Vaginal - trichomonas
Aerobic bacteria
Must have oxygen
Obligate anaerobes
Grow without oxygen
Killed or inhibited in presence of oxygen
Facultative anaerobes
Can grown with or without presence of oxygen
Microserophilic bacteria
Require 2-10 % oxygen and may require increased carbon dioxide.
Lab testing disk diffusion
Kirby of our paper disks impregnated with antimicrobial them placed on Ager plate with growth of organisms measures the zone of inhibition around the disk
Used to Measure as susceptible and intermediate or resistant
What is the e test
And impregnated plastic strip is placed on agar plate.
Used for VRE confirmation
What is disk approximation test
The disc approximation to shows inducible Clindamycin resistance
What is broth dilution
Herman’s the minimum inhibitory concentration MIC
3 methods for detecting viruses
Direct detection methods (hep b, RSV, HIV)
Antibody assay checks for immunoglobinsqqq
Viral culture
Fungi determination
Skin scrapping - identified directly from the specimen Some yeasts Grow on routine agar Germ tube and sugar assimilation tests Incubated for weeks at room temperature Direct antigen detection methods
How to identify viruses
Direct detection method ELISA, PCR, microscopy
Antibody assay for serum- immunoglobin presence or absence
Viral culture- special media
Mycobacterium
Special culture techniques
Must kill bacteria first
Incubated for 4-6 weeks
PCR, DNA probes
How are parasites detected
Microscopy - morphological appearance
Serological methods by reference labs
How is mycoplasma tested for?
Culture rarely attempted, fastidious growth requirements
Serological testing used to diagnose infection
Identification of Chlamydiae
Requires tissue culture - not done in most labs
Direct direction method fluorescent staining and ELISA technique
What type of cell wall does gram + bacteria have
Peptidoglycans cell wall doesn’t allow the crystal violet to wash away
Gram neg cells have a thin peptidoglycans layer and stain red to pink
gram positivity have a thick peptidoglycan layer and stain blue or purple
Gram - bacterial cell wall is composed of?
Lipopolysaccharide
Gram negative are colorless when going a gram stain until counter stained with safranin.
Specimens not appropriate for anaerobic cultures include
Sputum Rectal swab Nasal or throat swab Urethral swab Voided urine
