Need to study infectious diseases pharmacotherapy? This study table is a simple tool to help as you learn about “bugs & drugs.” I hope it helps you!
Authored By: Timothy Gauthier, Pharm.D., BCPS-AQ ID
In June 2015 I did a post for MedEd101 termed “Bugs and Drugs Chart, Lessons Learned From the Front Lines.” About a year later I revisited the topic and since then the below information has been updated periodically. Here is the latest and greatest simple bugs and drugs study table…
[Last updated: November 2023]
An important step towards learning about antimicrobial chemotherapy is to gain an understanding of when certain drugs should be considered or avoided. There are many ways to do this. Identifying potential toxicities (e.g., rifampin and liver toxicity) is one approach. Another approach is to learn what infections a specific drug is not good for (e.g., daptomycin should not be used for pneumonia because it is inactivated by surfactant in the lung).
Possibly the most common way to learn the basics of antimicrobials however, is to identify which drugs are commonly used for which bugs. As a pharmacy student and pharmacy resident I found the Sanford Guide’s section termed “antimicrobial spectra” to be very helpful in this regard, but it is likely a bit too much content to try to memorize for things like a pharmacy school exam.
To provide a simple study guide that can be useful for identifying what drugs are commonly considered for a given bug, I have developed the following. Additionally, I have included what drugs not to think about for a given bug. Identifying the gaps in coverage can be very helpful. A primary example for this is tigecycline, which has activity versus a broad array of microbes including vancomycin-resistant Enterococci, methicillin-resistant Staphylococci, Acinetobacter species, Mycobacterium species, Bacteroides fragilis and more — but not Pseudomonas aeruginosa!
I would like to emphasize this is meant to be a quick reference and study tool for students. Selecting an antimicrobial regimen for a patient case goes well beyond just whether a drug may or may not have activity versus a given bug. Additional, please note that this is not an exhaustive list and depending on the infection type, this chart may not be applicable (eg, daptomycin has no role in the treatment of pneumonia, but does cover MRSA).
| SEE | THINK | DO NOT THINK |
| Methicillin-sensitive Staphylococcus aureus (MSSA) | Oxacillin, nafcillin, dicloxacillin, cloxacillin, amoxicillin-clavulanic acid, cefazolin or cephalexin | Amoxicillin, ampicillin, ceftriaxone or vancomycin |
| Methicillin-resistant Staphylococcus aureus (MRSA) | Sulfamethoxazole-trimethoprim, doxycycline, delafloxacin, tigecycline, omadacycline, eravacycline, clindamycin, vancomycin, daptomycin, telavancin, dalbavancin, oritavancin, ceftaroline, linezolid, tedizolid or quinupristin/dalfopristin, lefamulin | Ceftriaxone, piperacillin-tazobactam, cefepime, carbapenems or fluoroquinolones |
| Pan-sensitive Enterococci | Ampicillin or amoxicillin | Vancomycin |
| Ampicillin-resistant Enterococci | Vancomycin | – |
| Vancomycin-resistant Enterococci (VRE) | Daptomycin, linezolid, tedizolid, tigecycline, omadacycline, eravacycline | Vancomycin |
| Beta-haemolytic Streptococi
(Streptococcus pyogenes [aka group A Strep] & Streptococcus agalactiae [aka group B strep]) |
Penicillin, clindamycin | – |
| Alpha-haemolytic Streptococci
(e.g., Streptococcus pneumoniae & Viridans group Streptococci) |
Ceftriaxone, levofloxacin, amoxicillin-clavulanic acid [beware penicillin & azithromycin resistance] | – |
| Pseudomonas aeruginosa | Piperacillin-tazobactam, ceftazidime, cefepime, ceftazidime-avibactam, ceftolozane-tazobactam, cefiderocol, imipenem-cilastatin, imipenem-cilastatin-relebactam, meropenem, doripenem, aztreonam, ciprofloxacin, levofloxacin, delafloxacin, tobramicin, plazomycin, polymyxin E (colistin), polymyxin B | Tigecycline, eravacycline, omadacycline, ertapenem gentamicin, or moxifloxacin |
| Stenotrophomonas maltophilia | Sulfamethoxazole-trimethoprim or levofloxacin | Carbapenems |
| Anaerobes | Metronidazole, clindamycin, ampicillin-sulbactam, amoxicillin-clavulanic acid, piperacillin-tazobactam, cefoxitin, cefotetan, ertapenem, moxifloxacin or tigecycline | Cefazolin, ceftriaxone or cefepime |
| Clostridium difficile | Oral or rectal vancomycin or fidaxomicin, then metronidazole (less preferred) | Intravenous vancomycin |
| Atypical organisms | Macrolides, fluoroquinolones, tetracyclines | – |
| Candida albicans | Fluconazole | – |
| Candida krusei | Echinocandin | Fluconazole |
| Cryptococcus neoformans | Amphotericin B or fluconazole | – |
| Aspergillus sp. | Voriconazole or isavuconazole | – |
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