Bacteriology

Some Basics

Here's a good link to some flashcards with some good, basic information. This includes normal flora for different sites, bacterial enzymes, some groupings of bacteria, etc. If the link doesn't work, here's a copy of the flashcards as a PDF: Basic Flashcards
If you prefer charts, I found this one is a pretty good overview. It's from a site called "medfools" but the infomation looks good (except for the random Homer Simpson). Here's a link to the chart, or the PDF of the Chart if that doesn't work.
If you have the Jarreau review book, check out pages 164-165 for a chart on sites and possible pathogens

General Terms | Stains | Biochemical Reactions | Media | Antibiotics

Gram Pos Cocci | Gram Neg Cocci | Gram Neg Rods | Gram Pos Rods

Temperature

Oxygen

Aerobe: organism requires oxygen
Facultative Anaerobe: can grow with oxygen present or absent
Obligate anaerobes: cannot grow in the presence of oxygen (harmed or hindered by oxygen)

Biochems

Beta-Lactams

Method of Action: inhibits cell wall synthesis.
- The beta lactam binds and inhibits the bacterial enzyme that assists with cell wall construction. This bacterial enzyme is called Penicillin Binding Protein (PBP).
- Cell wall contstruction WITHOUT antibiotic present
- Cell wall sythesis inhibited by a beta lactam
Target: Gram positive bacteria
Examples: Penicillins, Cephalosporins, Carbapenams, Monobactams
Resistance:
- Expression of MecA gene (seen in methicillin resistant Staph. aureus) changes the conformation of the PBP, so the beta-lactam cannot bind and inhibit it.
- Production of beta-lactamase, an enzyme which breaks the beta-lactam ring and inhibits the antibiotic.
  - Clavulanic acid can be used to counter this resistance. Clavulanic acid acts to inhibit the beta-lactamase produced by the bacteria, which allows the beta-lactam antibiotic to function. Examples of these combiniations include Augmentin (Clavulanic acid + amoxicillin) and Timentin (Clavulanic acid + ticarcillin).
  - Methicillin's structure allows it to be insensitive to beta-lactamase.

Glycopeptides

Method of Action: Inhibits cell wall sythesis
- Binds NAM and NAG polymers of the cell wall and prevents cosslinking
Target: Gram positive bacteria. Drug of choice for Clostridium difficile and MRSA.
Example: Vancomycin

Aminoglycosides

Method of Action: Inhibits protein synthesis
- Binds to the 30S ribosomal subunit and interferes with the proofreading process and ribosomal translocation (moving the growing peptide chain from the A site to the P site).
Target: Aerobic, gram negative bacteria. (Pseudomonas, Acinetobacter and Enterobacter)
Example: Gentamicin, Tobramycin, Amikacin

Tetracyclines

Method of Action: Inhibits protein synthesis (30S ribosomal subunit)
- Binds to the 30S ribosomal subunit and prevents the attachment of new amino acids to the peptide chain.
- Bacteria actively pump tetracyclines into their cytoplasm
Target: Broad spectrum. Specifically used for spirochetes (syphilis) and obligate intracellular bacterial pathogens (Chlamydia, Mycoplasma, Rickettsia).
Example: Tetracycline, Doxycycline
Resistance: Efflux pumps actively transport tetracycline (or other specific toxins) out of the bacteria. The gene for the efflux pump may be located on plasmids or transposons, which can be spread by horizontal transfer.

Chloramphenicol

Macrolides

Quinolines

Sulfonomides (Sulfa Drugs)

Staph. aureus is the most common pathogen for this genus. It can cause bullous impetigo, scalded skin syndrome, toxic shock syndrome, food poisoning, and more.