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Pharmacology I · Exam 1 · Class of 2028

Gram Coverage by Drug Class

Every antibiotic class in Lecture 1, with whether it covers gram-positives, gram-negatives and anaerobes — taken from the traffic-light table on each class slide. 26 classes: 8 lean gram-positive, 4 lean gram-negative, 13 cover both equally.

Every verdict is read out of the lecture deck — each class slide carries a traffic-light table and the color under each heading is what is printed here. The slide number is on every row.
Where these judgments come from. They are not mine and they are not inferred from the prose. Most antibiotic class slides carry a small three-column table — Gram Positive, Gram Negative, Anaerobes — with a colored circle under each heading, and this page prints those colors. Nothing in the slide text states which color sits under which heading, so each circle is matched to its column by position.
Two shades of green, and one odd one. The deck uses two greens interchangeably and both are shown here as covers. A third, lighter green appears on exactly one class — the tetracyclines, on all three columns at once — and is shown separately as moderate, because using it once and only across the board reads as deliberate rather than as a color slip.
Color is never the only signal here. Each cell carries its word as well as its color, because a red-and-green table is unreadable to a red-green color-blind reader.
The generation ruleWhy this axisAll 26 classes

The rule the whole cephalosporin block turns on slide 31

Read the table below against that. First generation is the strong gram-positive agent; by third generation the gram-negative cover is better and the gram-positive has been given away; fourth generation is the one that breaks the trade-off, and fifth is where MRSA cover appears.

Why this is the axis to revise from the exam review

At the review session the evening before the paper, Dr. Wood said he is not asking which single drug treats one named organism. He is asking whether an agent covers gram-positives, gram-negatives, anaerobes or atypicals — and he described the question outright: “a patient has an infection, a skin infection. Do you think it’s a gram-positive bacteria? Which one of these would be most likely to treat it?”, built from three agents with strictly gram-negative coverage and one good gram-positive. The full review is here.

All 26 classes read from the deck’s own traffic lights

Class & drugsGram +Gram −AnaerobesLeansWhat that meansSlide
Natural penicillinspenicillin G, penicillin VcoversnopartialMainly gram-positiveGood against gram-positive cocci, but no staph coverage. Drug of choice for syphilis, gas gangrene and meningococcus. No activity against aerobic gram-negatives.17
Aminopenicillinsampicillin, amoxicillincoversnopartialMainly gram-positiveAs the natural penicillins, plus some gram-negative aerobes. Drug of choice for Enterococcus, Listeria and endocarditis prophylaxis. Still no staph coverage.19
Aminopenicillin + beta-lactamase inhibitoramoxicillin/clavulanate, ampicillin/sulbactamcoverspartialcoversMainly gram-positiveAdding the inhibitor buys anaerobes (including Bacteroides) and MSSA. Drug of choice for skin and soft tissue, diabetic foot, and animal or human bites.25
Penicillinase-resistant penicillinsnafcillin, oxacillin, dicloxacillincoversnonoMainly gram-positiveDesigned solely to cover S. aureus (MSSA), with decreased activity against everything else. Not for MRSA — vancomycin is the choice there.26
Antipseudomonal penicillinspiperacillin, piperacillin/tazobactamcoverscoverscoversBoth equallyBroad spectrum. Keeps gram-positive coverage (MSSA only), adds gram-negative and antipseudomonal activity. Drug of choice for polymicrobial, nosocomial and intra-abdominal infection.27
Cephalosporins — 1st generationcefazolin, cephalexincoverspartialnoMainly gram-positiveGreat gram-positive activity (but no Enterococcus). Some gram-negatives — E. coli, Proteus, Klebsiella. Surgical prophylaxis, cellulitis, urinary infection.32
Cephalosporins — 2nd generationcefotetan, cefoxitin, cefuroxime, cefprozilcoverscoverspartialBoth equallyMore gram-negative activity than first generation — H. influenzae, Enterobacter, Neisseria, Proteus, E. coli, Klebsiella.33
Cephalosporins — 3rd generationceftriaxone, ceftazidime, cefotaxime, cefdinir, cefiximecoverscoversnoBoth equallyBetter gram-negative coverage than second generation, and loses more gram-positive. Adds Serratia and Moraxella catarrhalis. Ceftriaxone needs no renal adjustment but is avoided in the first 30 days of life.34
Cephalosporins — 4th generationcefepimecoverscoversnoBoth equallyThe exception to the trade-off: gram-negative activity WITHOUT sacrificing gram-positive. Antipseudomonal. No MRSA, no Enterococcus.36
Cephalosporins — 5th generationceftarolinecoverscoversnoBoth equallyThe cephalosporin with MRSA coverage. Gram-negative and gram-positive, no Enterococcus, no anaerobes.37
Cephalosporins — 5th generationceftolozane/tazobactamcoverscoverspartialBoth equallyAntipseudomonal, with some anaerobic activity including Bacteroides. No MRSA, no Enterococcus.38
MonobactamaztreonamnocoversnoMainly gram-negativeGram-negative ONLY. Spectrum resembles the aminoglycosides, with activity against P. aeruginosa.40
Carbapenemsimipenem, meropenem, ertapenemcoverscoverscoversBoth equallyVery broad — gram-positive (not MRSA), gram-negative, anaerobes, and P. aeruginosa except ertapenem.43
VancomycinvancomycincoversnonoMainly gram-positiveGram-positive ONLY. Drug of choice for MRSA and for penicillin-allergic infections.47
Macrolidesazithromycin, clarithromycin, erythromycincoverscoversnoBoth equallyGram-positive and gram-negative aerobes, and the atypicals. Does not cover enterococci.55
Tetracyclinestetracycline, doxycycline, minocyclinemoderatemoderatemoderateBoth equallyModerate across all three rather than strong anywhere — the only class the deck marks that way. Watch the calcium and iron binding, and photosensitivity.62
TigecyclinetigecyclinecoverscoverscoversBoth equallyBroad across all three. Bacteriostatic, for complicated skin infection.65
Aminoglycosidesgentamicin, tobramycin, amikacinnocoversnoMainly gram-negativeGram-negatives, including Pseudomonas and Enterobacter. No gram-positive coverage. The trough is checked to confirm it is undetectable.68
OxazolidinonelinezolidcoversnonoMainly gram-positiveFor vancomycin-resistant Enterococcus. Gram-positive only.72
Fluoroquinolones — 2nd generationciprofloxacinpartialcoversnoMainly gram-negativeGram-negative and atypical coverage, with variable Pseudomonas activity. Gram-positive cover is limited.76
Fluoroquinolones — 3rd generationlevofloxacincoverscoversnoBoth equallySecond-generation coverage with improved gram-positive activity, and it keeps Pseudomonas. Community-acquired pneumonia.77
Fluoroquinolones — 3rd generationmoxifloxacincoverscoversnoBoth equallySecond-generation coverage with improved gram-positive activity, but loses Pseudomonas. Community-acquired pneumonia.78
ClindamycinclindamycincoversnocoversMainly gram-positiveGram-positive aerobes including MRSA, and gram-positive anaerobes. It binds toxin, which is why it appears in toxic shock.80
Sulfamethoxazole and trimethoprimsulfamethoxazole/trimethoprimcoverscoversnoBoth equallyGram-positive aerobes including MRSA, and gram-negative aerobes. Does not cover enterococci.83
MetronidazolemetronidazolenonocoversNeither — anaerobesAnaerobes only — gram-positive and gram-negative anaerobes. The alcohol interaction is its signature.86
Polymyxinspolymyxin B, colistin (polymyxin E)nocoversnoMainly gram-negativeGram-negative only. A detergent-like mechanism against the lipopolysaccharide of the gram-negative outer membrane.87