A general term for drugs, chemicals, or other 

substances that either kill or slow the growth of microbes. 

A drug used to treat infections caused by bacteria and 

other microorganisms. Includes synthetically produced drugs

a compound that inhibits growth or reproduction of a 

microorganism, but does not directly kill the organism.

a drug that is administered in an inactive form. Activation 

occurs in vivo upon it being metabolized. (e.g. Isoniazid is activated by 

Mycobacterium’s catalase enzyme)

 capable of targeting both Gram-

negative and Gram-positive bacteria.

Commercially available strips. 

Serial dilution of antibiotic 

across strip. Placed on agar 

plate containing bacteria. View 

edge of clearing at lowest 

concentration of antibiotic.

Inoculate from MIC cultures 

into fresh growth medium 

lacking antibiotics

MBC will always be greater-

than or equal-to MIC.

Fosfomycin, Ramoplanin, Mersacidin, Moenomycin, Chlorobiphenylvancomycin, Vancomycin, Penicillin, Cephalosporin, Bacitracin, Carbapenems

Cycloserine, vancomycin, bacitracin, fosfomycin, penicillins, cephaolosporin, carbapenems

Macrolides, Lincosamides, Streptogramins, Everninomycins, Oxazolidones (50s)

Aminoglycosides, Tetracyclines (30s)

50s - erythromycin, chloramphenicol, clindamycin

30s - tetracycline, spectinomycin, streptomycin, gentamicin, tobramycin, amikacin

Rifampin, Ciprofloxacin, Novobiocins

nalidixic acid, quinolines (DNA gyrase)

rifampin (DNA dependent RNA polymerase)

Sulfamethoxazole, Trimethoprim

Structural analogs and competitive antagonists to PABA and dihydrofolate

TMP+SMX = bactrim

work synergistically to block different steps in same pathway that is used for folate metabolism/thymine biosynthesis

 Lipopolysacharide (LPS), polymyxin B, E

cyclic peptide binds LPS and hydrophobic tail interacts with membrane to form pore

Beta Lactams

(penicillin, cephalosporin)

Ampicillin

(amino penicillin)

A beta lactam - penicillin with altered R group that allows it to target a wider range of bacterial species

Broad gram negative coverage, enterococci

Nafcillin, Oxacillin

use penicillinase resistant antibiotics for staphylococcal skin infections when suspect that staph produces Beta-lactamase

Ticarcillin, Piperacillin

anaerobic coverage

IV or IM (cannot survive stomach acid)

Group A strep, syphilis, listeria, neisseria meningitidis, streptococcus pneumoniae

Oral administration (acid resistant)

Strep throat

Augmentin (amoxicillin + clavulanate)

Timentin (ticarcillin + clavulanate), Unasyn, Zosyn

Augmentin is oral, others are IV

Very broad coverage, anaerobic coverage

1. Can cause allergenic reactions and lead to superinfections

2. Not all are resistant to stomach acid, some given IV.

3. Non-MRSA and GAS infections can be treated with Nafcillin and 

Dicloxacillin

4. Anti-pseudomonal drug of choice is Ticarcillin (contains β-lactamase

inhibitor).

5. Augmentin is another combinatorial drug (Amoxacillin + clavulanic

acid)

Benefits over penicillin: more resistant to lactamases, R2 group offers more manipulation for changing specificity (2 R groups on penicillin ring)

Best for gram positives (strep and staph)

Cefazolin

 broader Gram-negative spectrum; respiratory tract infections, sinusitis 

and otitis media; urinary tract infections from E. coli, Klebsiella and Proteus

Cefprozil, cefuroxime, cefaclor, cefaxitin

 further increased effectiveness against Gram-negatives, but decreased 

against many Gram-positives (exception Streptococcus pneumoniae - Ceftriaxone)

Best for gram-negatives

 Broadest coverage against Gram-negatives and positives; best 

resistance to β-lactamases; some can cross blood-brain barrier (treat meningitis)

Cefquinome, Cefpirome, Cefozopran, Cefluprenam

Many not effective against most hospital acquired infections:

•     Clostridium difficile (C.dif)

•     Methicillin Resistant Staphylococcus aureus (MRSA)

•     Vancomycin Resistant Enterococcus (VRE)

•     β-lactam resistant Streptococcus pneumoniae

(Imipenem)

 Very small β-lactam.  Broadest antibacterial 

coverage.  Often given with cilastin (inhibitor of liver enzyme that breaks down this 

drug)

Making it small allows to get into smaller pores at the cell wall in gram-negatives

Great against Gram-negatives. Broad spectrum 

when given with vancomycin or clindomycin.

cell wall inhibitor

Glycopeptide

MRSA, C diff, VRE

Cell wall inhibitor

used against mycobacterium tuberculosis (MTB)

inhibits synthesis of mycolic acid in cell wall

Used against mycobacterium tuberculosis as a second line drug 

cell wall inhibitor

Aminoglycosides: (Streptomycin, Gentamycin, Tobramycin, Amikacin). Renal 

and cochlear toxicity at high rates.

Targets cell membrane, topical treatment only

treats skin, ear, and eye infections

high toxicity if ingested

Combination anti-microbial therapy

Synergistic

Combination use of 2 antibiotics reduces the MIC of either alone

Penicillin and aminoglycosides

Combination anti-microbial therapy

Additive

decreasing concentration of drugs (due to toxicity) may be applied 

if two different drugs are administered.

Combination antimicrobial therapy

Antagonistic 

 (reduction of activity of one or both)

Penicillin and Erythromycin or tetracycline (if you inhibit protein 

synthesis (i.e. erythromycin) cell wall synthesis stops. Penicillin only 

works on growing bacteria.