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Microbiology

Terms in this set (52)

Gram positive and gram neg stain what colors?
Pos- Blue
Neg- Red
Gram pos contain how many layers?
Two - Inner cytoplasmic membrane and Outer, thick peptidoglycan layer
Gram neg have how many layers?
Three - Inner cytoplasmic membrane, thin peptidoglycan layer, and outer membrane with lipopolysaccharide layer
Name the 4 morphologies of bacteria
1. Cocci (spherical)
2. Bacilli (rods) Short bacilli are also called coccobacilli
3. Spiral forms (comma-shaped, S-shaped, or spiral shaped)
4. Pleomorphic (lacking a distinct shape)

Organization of bacteria include pairs, clusters, strips, and single bacteria with flagellae
How many classic gram pos bacteria are there that cause disease in humans?
7
How many of those gram pos are cocci?
3
Streptococcus is gram neg or gram pos?
pos
Enterococcis is gram neg or gram pos?
pos
Staphylococcus is gram neg or gram pos?
pos
How many gram pos are bacilli?
4
How many gram pos bacilli form spores? How many do not?
2 and 2
Bacilli is gram neg or gram pos? spore or no spore?
pos; spore
Clostridium is gram neg or gram pos? spore or no spore?
pos; spore
Corynebacterium is gram neg or gram pos? spore or no spore?
pos; no spore
Listeria is gram neg or gram pos? spore or no spore?
pos; no spore
There is only one group of gram neg diplococci. What is it?
Neisseria
There is only one group of spiral-shaped organisms. What are they and are they gram neg or gram pos?
The spirochetes. Treponema pallidum is in this group. Gram neg
Besides the spirochetes and the diplococci, the rest of the gram neg organisms are...
pleomorphic or rods
What is a weak gram pos bacteria and requires acid fast staining?
Mycobacteria (think TB and leprosy)
This group of bacteria are gram neg but are too small to be seen with light microscope. They must be visualized by darkfield miscroscope instead. What group are they?
Spirochetes
Which are vulnerable to lysozyme and penicillins - gram pos or gram neg?
gram pos
Which contain the endotozin lipid A - gram pos or neg?
gram neg
how is the endotoxin from gram neg bacteria released in the body to cause destruction?
through immune system chewing up bacteria and therefore releasing endotoxin
Why are spirochetes thought to be considered as "stealth" organisms?
BEcause they have an additional phospholipid rich outer membrane in addition to their regular three layers of gram neg organism....this additional layer has few exposed proteins. They also have periplasmic flagella that helps spin the spirochete to thrust them forward
What group of bacteria do not have a cell wall but instead a simple membrane and therefore not considered gram neg or gram pos?
Mycoplasma
Which ribosome do bacteria have vs animals?
70S (bacteria) vs 80S (animals)
The bacteria ribosome consists of what two parts?
50S subunit and 30S subunit
Which two antibiotics are like magic bullets and attack the 50S subunit and 30S subunit, respectively
erythromycin and tetracyclin, respectively
What are two very important metabolic properties of bacteria?
1. how organisms deal with oxygen
2. what the organism uses as a carbon and energy source
Why are some bacteria able to thrive with oxygen but others cannot?
Molecular oxygen is very reactive and when it snatches up electrons it can form H2O2, superoxide radicals (O2-) and hydroxyl radicals. All of these are toxic unless broken down. Bacteria that thrive on oxygen are those that have catalase, peroxidase, and superoxide dismutase on board to protect them from free radicals. On the other end of the spectrum, some bacteria have no protective enzymes and die when O2 is on board.
Obligate aerobes
Use O2 just like us and have all of the protective enzymes
Facultative anaerobes
These bacteria are aerobic. But they CAN grow in the absence of O2 using fermentation for energy. Thus they have the faculty to be anaerobic but prefer aerobic conditions
What are microaerophilic bacteria?
Also called aerotolerant. They use fermentation and have no electron transport system. They can tolerate low amounts of O2 because they have superoxide dismutase but no catalase.
What are obligate anaerobes
They hate O2 and have no enzymes to defend against it. Often there are two bottles for blood cultures - one has no oxygen for the growth of obligate anaerobes
In terms of energy source, all medically important bacteria are...
chempheterotrophs as they use chemical and organic compounds for energy sources
Name some features that make bacteria virulent
Flagella, Pili, biofims, endospores (bacillus and clostridium), facultative intracellular organisms, exotoxins, endotoxins
Name the 7 facultative intracellular organisms
Listeria, Salmonella, Yersinia, Francisella, Brucella, Mycobacterium, Legionella (Listen Sally, Your Friend Bruce Must Leave)
All penicillin-family antibiotics contain what?
A beta-lactam ring
PCNs are bacteriostatic or bactericidal?
bactericidal
Which enzyme does PCN destroy in the bacteria?
The transpeptidase, which helps to synthesize the peptidoglycan cell wall
In gram neg bugs, the PCNS must pass through ____ to reach transpeptidase to arrest cell wall synthesis and cause bacterial death
Porins
To be effective in killing bacteria, the beta lactam pcn must do three things:
Penetrate the cell layers
Keep the beta lactam ring intact
Bind to the transpeptidase
In what 4 ways do bacteria defend themselves from beta lactam abx?
1. Altering porins (gram neg)
2. Beta lactamase enzyme to cleave beta lactam ring (gram neg and pos). ex: penicillinase from gram pos bacteria
3. Alter molecular structure of transpeptidase. MRSA defends itself this way, making it invulnerable to ALL PCN family drugs
4. Develop efflux pumps to pump out abx before they bind (gram pos and neg)
All PCNs can cause what adverse effects?
Anaphylaxis reactions and diarrhea (which can allow C diff to take over)
What are the five types of pcns?
1. Penicillin G: original PCN
2. Aminopenicillin: offer better coverage of gram neg bacteria
3. Penicillinase-resistant penicillins (useful against beta-lactamase producing staph aureus
4. Anti-pseudomonal pcns (include carboxypenicillins, ureidopenicillins, monobactams): even wider coverage against gram neg bacteria
5. Cephalosporins: resistant to beta-lactamase, cover a broad spectrum of gram pos and gram neg bacteria
What are the drugs in aminopenicillin class? Which is more effectively absorbed orally?
ampicillin and amoxicillin
Amox absorbed orally better
What is the drug of choice for listeria infections?
amoxicillin
What are the penicillinase resistant penicillins? How are they usually administered? What can they kill?
Methicillin, nafcillin, oxacillin
-IV, kill staph aureus
What is no longer used in the US due to interstitial nephritis?
methicillin. (although you will still hear it in reference to sensitivity testing such as MRSA)
What is the drug of choice for serious staph aurea infections such as cellulitis, endocarditis, and sepsis?
nafcillin
What are the oral beta-lactamase resistant pcns?
cloxacillin and dicloxacillin
What are the anti-pseudomonal penicillins?
Carboxypenicillins (Ticarcillin) and ureidopenicillins (piperacillin)
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