A Study List For Pharmacy Students: Antibiotics That Can Cover Pseudomonas and/or MRSA

What drugs cover Pseudomonas aeruginosa? What drugs cover MRSA? These are two of the most important bacterial pathogens to cause healthcare-associated infections today. To help answer these questions, here is a study list of antibiotics that can cover Pseudomonas and/or MRSA.

Authored by: Timothy P. Gauthier, Pharm.D., BCPS, BCIDP

Last Updated: 17 November 2025

Many pharmacy students are introduced to antimicrobial spectrum of activity basics through microbiology coursework. During this time it is common for the student to receive a somewhat overwhelming amount of information and little guidance on the relative clinical importance of the material. In my experience this is partly driven by non-clinician instructors being responsible for many university-level microbiology courses.

As students move into higher-level classes, if they cannot adequately identify and define previously covered content, they are likely to find it difficult applying pharmacotherapy concepts to clinical cases. Not all students will struggle with this, but many do and simple study lists can be a great way to refresh or highlight some of the important points. Repetition and using study strategies that work for you are key.

In an effort to provide an additional resource for learning antimicrobial spectrum basics, I have composed this article, which focuses on two of the most important pathogens in healthcare today: methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa.

MRSA Snapshot

MRSA is a catalase-positive Gram positive cocci and facultative anaerobe. The U.S. Center for Disease Control and Prevention (CDC) tracks antibiotic resistance threats in the United States, providing information here. CDC estimates MRSA causes over 70,000 severe infections and 9,000 deaths annually in the united states. It has been identified MRSA as a “serious” threat to public health.

MRSA is such an important organism that the Infectious Diseases Society of America (IDSA) developed a clinical practice guideline (available here, although could use an update!) to assist in managing MRSA infections. Whether working in the community or in the hospital, MRSA is an important pathogen.

Pseudomonas Snapshot

Pseudomonas aeruginosa is a non-fermenting Gram negative rod. Similar to MRSA, it also is a key pathogen as per CDC, which has flagged multidrug-resistant (MDR) Pseudomonas aeruginosa as a “serious” threat to public health. Unfortunately, Pseudomonas aeruginosa is notorious for being drug-resistant all too often. Data from CDC show that in 2017, MDR Pseudomonas caused over 30,000 infections amongst hospitalized people and nearly 3,000 deaths.

Pseudomonas aeruginosa does not have it’s own clinical practice guideline, but it is an organism covered extensively in the organ system-focused IDSA guidelines, such as the one focused on Gram negative resistance available here. It is an incredibly important pathogen for healthcare personnel to be aware of and pharmacists should have a general awareness of which drugs can have activity against it.

List of Antibiotics that can Cover Pseudomonas and/or MRSA

The table below is sectioned into drug classes. One thing that can help when trying to list all the drugs that cover these organisms is to attempt to recall them using a structured approach, one class at a time.

Antibiotics without activity versus either of the pathogens have not been included.

NOTE: This general table is provided for study purposes only. Depending on factors such as infection type, patient-specific variables, and the presence of antibiotic resistance, some of the labeled options below may or may not be valid in clinical practice. For example, tigecycline can cover MRSA, but it distributes rapidly into the tissues upon IV administration, so tigecycline is a poor choice for MRSA bacteremia. In addition aminoglycosides and fluoroquinolones are indicated as a “no” for MRSA, but they may be an option as part of combination therapy.

A few notes on nuances:

While lefamulin does cover MRSA, there is a lack of clinical data using it for this bacteria
Ceftobiprole does has some Pseudomonas activity but is not expected to be used routinely for this purpose in clinical practice
Adding vaborbactam to meropenem will cover Pseudomonas, but the vaborbactam does almost nothing for this and it is the meropenem doing all of the work in that case. Adding a beta-lactamase inhibitor does not always expand coverage in a clinically meaningful way for Pseudomonas.
Amikacin is only considered useful for Pseudomonas when the infection is a UTI
Gentamicin is left on here as a “no” for both. It used to be considered useful for Pseudomonas but no longer is.
Aminoglycosides are not routinely used for MRSA so are listed as a “no” here, but may have a role for Gram positive synergy versus MRSA. Note that combining various antibiotics may produce antimicrobial effects not seen alone.

Hopefully this visual will be helpful for learning about which antibiotics can cover Pseudomonas aeruginosa and/or MRSA.

	Class	Pseudomonas	MRSA
Piperacilin-tazobactam	Uriedopenicillin/ BLI	+	–
Ceftazidime	3^rd Gen Ceph	+	–
Ceftazidime-avibactam	3^rd Gen Ceph / BLI	+	–
Cefepime, Cefepime-Enmetazobactam	4^th Gen Ceph, w/ BLI	+	–
Ceftaroline	5^th Gen Ceph	–	+
Ceftobiprole	5^th Gen Ceph	–	+
Ceftolozane-tazobactam	Ceph/ BLI	+	–
Cefiderocol	Siderophore Ceph	+	–
Imipenem-cilastatin	Carbapenem	+	–
Imipenem-cilastatin-relebactam	Carbapenem/ BLI	+	–
Meropenem	Carbapenem	+	–
Meropenem-vaborbactam	Carbapenem/ BLI	+	–
Aztreonam	Monobactam	+	–
Aztreonam-avibactam	Monbactam/ BLI	+	–
Ciprofloxacin	Fluoroquinolone	+	–
Levofloxacin	Fluoroquinolone	+	–
Delafloxacin	Fluoroquinolone	+	+
Tetracycline	Tetracycline	–	+
Doxycycline	Tetracycline	–	+
Minocycline	Tetracycline	–	+
Tigecycline	Glycylcycline	–	+
Omadacycline	Aminomethylcycline	–	+
Eravacycline	Fluorocycline	–	+
Sulfamethoxazole-trimethoprim	Folic Acid Inhibitor	–	+
Clindamycin	Lincosamide	–	+
Vancomycin	Glycopeptide	–	+
Daptomycin	Lipoglycopeptide	–	+
Telavancin	Lipoglycopeptide	–	+
Oritavancin	Lipoglycopeptide	–	+
Dalbavancin	Lipoglycopeptide	–	+
Linezolid	Oxazolidinone	–	+
Tedizolid	Oxazolidinone	–	+
Dalfopristin-quinupristin	Streptogramins	–	+
Polymyxin B	Polymyxin	+	–
Polymyxin E (colistin)	Polymyxin	+	–
Gentamicin	Aminoglycoside	–	–
Tobramycin	Aminoglycoside	+	–
Amikacin	Aminoglycoside	+	–
Fosfomycin	Epoxide	–	+
Rifampin	Rifamycin	+	+
Nitrofurantoin	Nitrofuran	–	+
Methenamine	Urinary Antiseptic	+	+