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Overview of Antibiotics

Bacteriostatic vs. Bactericidal Action

Bactericidal antibiotics actually kill the microbe. Generally, these agents inhibit cell wall synthesis and function (AG inhibit protein synthesis and FQ inhibit DNA replication, but they are bactericidal). Bactericidal agents may be time specific (beta-lactam antibiotics and vancomycin) requiring the microbial cell to be in a specific phase to exert its action OR they may be concentration dependent (AG and FQ), able to kill the cell in any phase.

Generally, bactericidal agents and bacteriostatic agents should not be co-administered. This is especially true with the beta-lactams, which require the cell to be dividing to exert their effect. Since the bacteriostatic agents inhibit cell growth, the two classes are antagonistic and the efficacy of both would be diminished. Bacteriostatic agents may also decrease the efficacy of the AG by inhibiting their transport into the cell.

The bacteriostatic/bactericidal classifaction is somewhat dose dependent. A bacteriostatic agent, given in sufficient doses to increase the concentration, may exhibit bactericidal activity. Similar, extremely low doses of a bactericidal drug may merely exhibit bacteriostatic activity.

Always in the treatment of bacterial infections, cultures should be taken to determine the specific antibiotic that is going to be effective against the particular strain causing the infection. Following is a table of GENERAL drugs of choice for the treatment of specific infectious diseases. NOTE that these choices are always predicated by the susceptibility of the causative organism.

Gram Positive Cocci	Staphylococcus aureas	Endocarditis, Bacteremia, Pneumonia, Cellulitis	Nafcillin/Oxacillin Vancomycin (methicillin-resistant)
	Streptococcus spp.	Scarlet Fever, Otitis Media, Erisypelas	Penicillin V, Amoxicillin
Gram Negative Cocci	Neisseria gonorrhoea	Gonorrhoea	Ampicillin, Amoxicillin, Penicllin G + Probenicid Ceftriaxone, Cefixime
Gram Positive Bacilli	Bacillus anthracis	Anthrax	Penicillin G
	Corynebacterium diphtheria	Diphtheria	Erythromycin
	Clostridium perfringens	Gangrene	Penicillin G
	Clostridium tetani	Tetanus	Penicillin G, Vancomycin
	Clostridium difficile	Pseudomembranous colitis	Metronidazole, Vancomycin
Gram Negative Bacilli	Escherichia coli	Urinary Tract Infection	Sulphamethoxizole + Trimethoprim
	Salmonella typhi	Typhoid Fever	Ciprofloxacin
	Brucella abortus	Brucellosis, Undulant Fever	Doxycycline + Gentamicin
	Yersinia pestis	Plague	Streptomycin + Tetracycline
	Francisella tularensis	Tularemia	Streptomycin, Gentamicin
	Vibrio cholerae	Cholera	Doxycycline, Ciprofloxacin
	Legionella pneumophila	Legionnaire's Disease	Erythromycin
Spirochetes	Treponema pallidum	Syphilis	Penicillin G
	Borellia burgdorferri	Lyme Disease	Skin -- Doxycycline Cardiac/CNS/Arthritis -- Ceftriaxone
Miscellaneous	Rickettsia	Rocky Mountain Spotted Fever	Doxycycline
	Chlamydia	Psittacosis	Doxycycline
	Pneumocystis carnii		Sulphamethoxazole + Trimethoprim

END MATERIAL FOR TEST 5