AMT MLS Exam Complete Study

Bacteria

single-celled organisms that lack a nucleus; prokaryotes

Autotrophic

Organisms that make their own food

Heterotrophic

Organisms that obtain their nutrients or food from consuming other organisms.

pathogenic

causing disease

Flagella

whiplike tails found in one-celled organisms to aid in movement

Phagocytosis

Cell eating

Bacteriophage

A virus that infects bacteria

Mesophilic

thriving in a moderate environment

Osmosis

Diffusion of water through a selectively permeable membrane

Semipermeable

some substances can pass directly through the cell membrane by passive or active transport

Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended

cell wall/ membrane

forms the outer layer of the cell

Microaerophilic

requires only a small amount of oxygen

facultative anaerobes

can live with or without oxygen

Facultative areobe

an organism that can live with or without oxygen

Thermophilic

heat loving

capsule

A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.

ambient

(adj.) completely surrounding, encompassing

Nucleus

Control center of the cell

spore

A reproductive cell with a hard, protective coating

Aerobic

Process that requires oxygen

Anaerobic

Process that does not require oxygen

Pili

Appendages that allow bacteria to attach to each other and to transfer DNA

Shapes and arrangements of bacteria

Spherical: cocci

Rod: bacilli

Spiral: Spirilla

Comma: Vibrios

Corkscrew: Spirochaetes

acid fast stain

a differential stain used to identify bacteria that are not decolorized by acid-alcohol

TB

Fluorescent stains

Antibodies are attached to a fluorochrome (such as fluorescein). Antibody-antigen binding is detected by the fluorescence.

Escherichia coli

Staphylococcus

Gram's stain

a process used to classify bacteria based on amount of peptidoglycan in the bacterial cell wall.

purple= gram positive

turn pink or red= gram negative

Gram positive indicates: staphylococcus, streptococcus, corynebacterium, clostridium, and listeria

Giemsa-Wright stain

Borrelia, Plasmodium, Rickettsia, Trypanosomes, and Chlamydia

purple

Certain Bugs Really Try my Patience

India ink stain

Cryptococcus neoformans

Inhibitor Additive in media preparation

An inhibitor additive is placed in media to inhibit eukaryotic growth and fungal growth.

Salt and buffer additives in media

salts are used to affect the selectivity of targets

buffers are used to maintain pH level and energy source

Indicator additive in media

a substance that lead colonies of certain organisms to take a distinctive appearance.

enrichment media

Usually liquid media contains chemicals that enhance the growth of the desired bacteria. Other bacteria will grow but increases the growth of desired bacteria.

bacteria smear

a thin layer of bacteria placed on a slide for staining

selective and differential media

Allows only certain bacteria to grow, with a component that also differentiates among the species that survive.

enrichment procedure

- expose mixed sample to unusual treatments

--endospore isolation- boil sample; only endospores survive

Anaerobic media

Obligate anaerobes must be cultured in the absence of free oxygen

Reducing media contain compounds that combine with free oxygen and remove it from the medium

Petri plates are incubated in anaerobic culture vessels

Sealable containers that contain reducing chemicals

living host cells

Used to grow certain types of bacteria that can only grow in living host cells. Ex: leprosy, rickettsias, and viruses

candle jar

A small, sealed container which uses a chemical reaction to remove the oxygen so anaerobic bacteria may be cultured within

Specimen Preparation

the process of altering the sample to be fit for examination

focused ion beam

transmission electron microscopy

atom probe tomography

electron microscope

Specimen rejection criteria

labeling, collection/preservation, request form/order, hemolyzed sample

blood culture

test to determine if infection is present in the bloodstream by isolating a specimen of blood in an environment that encourages the growth of microorganisms; the specimen is observed, and the organisms that grow in the culture are identified

urine culture

a procedure used to cultivate the growth of bacteria present in a urine specimen for proper microscopic identification of the specific pathogen

stool culture

test to identify microorganisms or parasites present in feces that are causing a gastrointestinal infection

sputum culture

microbial test used to identify disease-causing organisms of the lower respiratory tract, especially those that cause pneumonias

throat culture

A laboratory diagnostic test to find a bacterial or fungal infection in the throat. Sampling is performed by throat swab, and the sample is put in a special cup (culture) that allows infections to grow. If an infection grows, the culture is positive. The type of infection is found using a microscope, chemical tests, or both. If no infection grows, the culture is negative.

Spinal fluid cultures

Performed when meningitis is suspected; gram stain of centrifuged CSF and swab onto blood and chocolate agar

upper respiratory culture

isolate and identify pathogenic organisms from sinus.

evaluate pharyngitis or nares for staph.

wound culture

performed on wound exudate to determine the presence of microorganisms and to identify the specific type

Abscess culture

swab the area and perform AFB or fungal culture.

tissue culture

examine cells for foreign states or pathogens

urethral culture

usually done on men, to identify germs that may cause urethritis

cervical cultures

Sampling done to diagnose STD's, vaginitis

catheter tip culture

to examine if a patient has a catheter related bloodstream infection

intrauterine device culture

to examine if the patient with an IUD has staph or other infection.

Types of Microorganisms

Bacteria

Archaea

Fungi

Protozoa

Algae

Viruses

Multicellular animal parasites

Processing specimens

- most tissues are placed in a 10% formalin solution to preserve them before they are sent to the laboratory

- if the container is not prefilled half-fill the specimen container with the formalin solution ahead of time

SPECIMEN CONTANIERS

- the container should be labeled with the following:

The patients name and the doctor's name

The date and time of collection

The body site from which the specimen was obtained

Your initials

- specimen containers should be placed in a special transport bag labeled with the biohazard symbol

normal flora

Microorganisms that reside in or on the body without causing disease. Be able to recognize them.

pathogens in culture

Be able to recognize

acid fast bacilli

Mycobacterium tuberculosis

Using flem or sputum sample onto culture media and reported when growth and identification is made.

AFB smears are report within 24 hours

# AFB observed x 100

Multi-drug resistant TB

is resistant to isoniazid and rifampin.

-primarily d/t inadequate tmt and ppl not following medication regimen correctly

Using Drug sensitivity test (culture)

Quality control of media

growth supporting characteristics

physical characteristics

gel strength

batch contamination

Methods of Bacterial Identification

morphological and biochemical tests

serotyping

antibiotic inhibtion

stained smears

Allows looking at bacteria in blood abscess and bacteria

Not many stains are species specific

Analytical Profile Index (API)

For identification of pathogens by what conditions they will grow in

Strips that contain 20 test mini chambers to identify enterobacteriaceae

automated bacterial identification

automatically identifies the bacteria in a very short time.

Involves staining, motilità test, cultural characteristics and a series of biochemical tests.

Biochemical bacteria identification

catalase testing

oxidase testing

substrate utilization tests

Carbohydrate bacterial identification

Convetional carbohydrate or glycan microarrays

whole mucin microarrays

microarrays constructed from bacterial polysaccharides

Oxidase test

identifies bacteria that have cytochrome oxidase

Catalase Test

used to identify organisms that produce the enzyme catalase

Coagulase test

a test in which organisms are mixed with plasma on a slide. if the cells clump together, the culture is coagulase positive

Bile solubility test

(Another way to ID S. pneumoniae)

Broth method

-Saline suspension

-Add 10% Na deoxycholate

-Incubate 37°C for 15 min

-Positive = clear solution

Colony Method

-Add 2% Na deoxycholate

-Incubate 37°C for 30 min

-Positive = dissolved colony

Principle: Cells of S. pneumoniae lyse when treated w/ a 10% solution of sodium deoxycholate, while other streptococci and gram pos cocci are not bile soluble. Lysis occurs b/c bile soluble organisms contain an autolytic amidase that when activated by bile salts cleave the bond b/w alanine and muramic acid in the cell wall.

beta lactam disk (Cefinase disk)

chromogenic cephalosporin which is used as substrate

Organisms with B-lactamses open the B-lactam ring of the substrate that results in a colored product allowing detection.

Optochin disk (P disk)

Differentiates microorganisms based on susceptibility to ethyl hydrocupreine hydrochloride., * S. pneumoniae

* Zone of inhibition >/ 14mm w/a 6mm disk

* Differentiate S. pneumoniae from viridans strep

Bile Esculin Test

undefined, selective, and differential medium used to isolate for organisms that tolerate bile and hydrolyze esculin (Group D. streptococcus or enterococcus)

positive= blackened stain

Bacitracin disk (A disk) test

small amount of bacitracin is placed on agar plate and incubated for growth 18-24 hrs at 35C, then examined for zones of inhibition surrounding the disk.

greater than 10mm =positive

Indole test

Tests organisms ability to breakdown Tryptophan to indole. Utilized Kovac's reagent.

Positive - Red,

Negative- No color change

CAMP test

Confirmatory test for group B Strep. (Strep. agalactiae), unknown beta Strep. is streaked perpendicular to Staph. aureus on blood agar

TSB with 6% NaCl test

A tolerance test, looking for the ability for an organism to survive the salt-rich environment.

color change=positive

mannitol salt test

MSA - selective for Staphylococcus genus - detects mannitol fermentation

Gram positive cocci

Staphylococcus- round balls in clusters

Streptococcus- round balls strung together long strands

Enterococcus- round balls in strands 2-6

Gram positive bacilli

Clostridium- small stick shaped bodies

Corynebacterium- small rod shaped usually clomped together

Bacillus- multiple small rods strung together

Listeria- very small robs that make larger spider web like structures

Mycobacterium (acid fast)- very string lightning strike like structures

Gram negative cocci

Neisseria- small rounded shapes that form cheetah like structures together.

Moraxella- small round balls very spread out with little to no clumps.

gram negative coccobacilli

Haemophilus influenzae- small rods singular or connected to one other rod.

gram negative enterobacteriaceae

-Enterobacteriaceae are a family of gram-negative bacteria that include both harmless and pathogenic bacteria

-Pathogenic: Enterobacteriaceae include Salmonella, Shigella, Enterobacter, E. Coli, Klebsiella, Proteus vulgaris

-Enterobacteriaceae are commonly found as normal flora of the gastrointestinal tract (termed "enterics") but are also common causes of urogenital infections (E. Coli, Proteus vulgaris, Enterobacter)

gram negative bacilli

Brucella

Bordetella

HACEK family:

-Haemophilus

-actinomyetemcomitans

-cardiobacterium Hominis

-Eikenella corrodans

-kingella kingae

Pseudomonas

Campylobacter

Anerobic Bacteria:

-Fusobacterium

-Bacteroides group

-actinomyces

-clostridium difficile

MRSA (methicillin-resistant Staphylococcus aureus)

a mutated strain of the bacterium Staphylococcus aureus that is resistant to the antibiotic, methicillin.

MDRO (multi drug resistant organisms)

Examples: C-diff, MRSA. Frequent hospitalizations, invasive procedures, previous exposure to antibiotics make someone more susceptible to infection.

Vancomycin Resistant Enterococcus (VRE)

a strain of enterococcus that cannot be controlled with antibiotics; it is spread through direct and indirect contact

Rapid enzyme immunoassay (EIA) from throat swabs

With a throat swab, a rapid test can detect group A streptococcus bacteria.

This can be from tree throat, scarlet fever, assesses and pneumonia.

Culture for beta hemolysis screening

??

clostridium difficile test

detect toxin in stool

usually green

3 or more liquid stools in 24 hours

Test for glutamate dehydrogenase (GDH), if positive follow up with EIA or NAAT testing.

campylobacter urease test

rapid diagnostic for Helicobacter pylori

- ability of H. Pylori to secrete the urease enzyme, which catalyzes the conversion of urea to ammonia and CO2.

- mucosa is taken from antrum of stomach and placed into urea medium and indicator (phenol red)

negative=yellow

positive= red

campylobacter antigen/antibody test

blood test to look for antibodies of bacteria of campylobacter

Helicobacter pylori (H. pylori)

a spiral-shaped gram-negative bacterium that colonizes the gastric mucosa; is involved in most cases of peptic ulcer disease

Test: urea breath test, drink urea and breath is then checked or stool sample tested.

Shiga Toxin Test

Tests for the shiga toxin directly using EIA.

detects the presence of E. coli which produces shiva toxin.

Kirby-Bauer Test

disk diffusion test essential for groups of bacteria commonly showing resistance. (drug susceptibility)

minimal inhibitory concentration (MIC)

the lowest concentration of the drug that will prevent the growth of an organism

Automated Antimicrobial Susceptibility Testing

AST - used to quantify antimicrobial resistance.

DNA probe test

able to detect the presence of the genes of chlamydia bacteria and gonorrhea, Another form of Nucleic Acid Testing involving Southern Blotting . DNA is lysed and released into a single strand from an unknown specimen and added to cloned strand of DNA, Flourescence will indicated presence of bacteria you are looking at