Bacitracin
Also known as: Bacitracin A, bacitracin zinc, bacitracin methylene disalicylate, BMD, BaciiM, zinc bacitracin
Cyclic polypeptide antibiotic; non-ribosomally synthesized peptide produced by Bacillus species (primarily Bacillus licheniformis and related organisms); target
What it is
Bacitracin is found in some of the most common over-the-counter antibiotic ointments used for wound care and skin infections. Healthcare providers also use it to help prevent surgical site infections. It is produced naturally by Bacillus species of bacteria and has been a staple of first-aid kits and hospital wound care for decades.
The scientific side
bacitracin is a cyclic peptide antibiotic that kills bacteria primarily by sequestering undecaprenyl pyrophosphate (C55PP), a critical lipid carrier molecule essential for bacterial cell wall biosynthesis. Undecaprenyl pyrophosphate must be recycled to undecaprenyl phosphate (Und-P) in order to sustain the continuous assembly of peptidoglycan, the structural backbone of the bacterial cell wall. When bacitracin binds tightly to C55PP, it prevents dephosphorylation and recycling of this carrier lipid, effectively halting peptidoglycan synthesis and causing lethal cell envelope damage in susceptible Gram-positive bacteria (PMIDs: 42709865, 42725977, 38323910). Studies in Streptococcus pneumoniae demonstrate that deleting the undecaprenyl pyrophosphate phosphatase UppP increases susceptibility to bacitracin, underscoring that the undecaprenol recycling pathway is the central point of action. Research using statin-induced lipid carrier depletion showed that this same mechanism can be pharmacologically mimicked and that it phenocopies bacitracin's disruption of peptidoglycan precursor balance, revealing a conserved vulnerability in Gram-positive pathogens including MRSA. A 2026 study on N-terminal modification of bacitracin A further confirmed that enhanced cell wall peptidoglycan biosynthesis inhibition remains the lead antibacterial mode, with hydrophobic modifications additionally inducing membrane depolarization and disruption of the purine metabolic pathway. Bacteria resist bacitracin through multiprotein membrane complexes called Bce modules, which include histidine kinase sensors (BceS) and ABC transporters (BceAB) that detect bacitracin and pump it away from the membrane. In Bacillus subtilis, a conserved threonine residue in BceS is critical for maintaining kinase-phosphatase balance and proper bacitracin resistance signaling. Research in Clostridioides difficile showed that its Bce module incorporates the undecaprenyl pyrophosphatase BacA2 and is essential for survival in the presence of bacitracin-producing commensal bacteria in the gut microbiome. In animal growth promotion contexts, bacitracin zinc modulates cecal microbiota and lipid metabolism, with multi-omics analyses showing distinct effects on gut microbial communities compared to natural plant extracts.
Class: Cyclic polypeptide antibiotic; non-ribosomally synthesized peptide produced by Bacillus species (primarily Bacillus licheniformis and related organisms); targets bacterial cell wall biosynthesis
Administration & storage
- Administration
- Intraoperative wound irrigation (neurosurgical and cardiac surgery contextshistorical use) (PMID: 36052633PMID: 33346346)No subcutaneous or intramuscular injection data found in the fetched abstracts for human use
- Storage
- Topical ointment formulations are stored at room temperature. Bacitracin-loaded collagen/bacterial cellulose dressings showed high water absorption capacity (48.7 g/g) and moisture permeability properties relevant to wound moisture management. Specific storage temperature data for bacitracin products was not detailed in the fetched abstracts.
Legal & regulatory status
Topical bacitracin ointment is available over the counter in the United States for minor wound care. Bacitracin zinc is also used in combination products (e.g., with neomycin and polymyxin B). Injectable bacitracin…
Bacitracin does not appear on the WADA Prohibited List based on its established topical and veterinary use profile; no WADA-related data was found in the fetched abstracts.
No Health Canada regulatory status data was found in the fetched abstracts. Standard OTC topical antibiotic status is presumed based on the broader literature context but cannot be confirmed from retrieved abstracts…
What it's studied for
- Topical wound care and prevention of minor skin infections Established clinical use (observational and comparative studies)
- Prevention of surgical site infections (SSI) Low-to-moderate certainty (observational evidence; used in surgical prophylaxis protocols)
- Treatment of infected wounds and burn wounds (combination with other topical agents) Preclinical and early clinical evidence
- Combination antibiotic therapy for drug-resistant Gram-positive infections (investigational) Preclinical / in vitro research
- Antimicrobial growth promotion in livestock (veterinary / agricultural) Established veterinary use (comparative trials in poultry and swine)
- Antimycobacterial activity (investigational) Preclinical / in vitro
Safety signals
- Risk of contact allergy and allergic sensitization with topical use
- Promotion of resistance gene selection and antimicrobial resistance pressure in environmental microbiomes
- Sub-inhibitory bacitracin concentrations may enhance virulence of Streptococcus pyogenes
- Intrinsic bacitracin resistance in gut-colonizing pathogens may limit efficacy and complicate infection treatment
- Postoperative candida superinfection in the setting of bacitracin/polymyxin topical prophylaxis
- Gut microbiome disruption with systemic/in-feed bacitracin use
- Systemic nephrotoxicity with parenteral bacitracin (historical, injectable formulations)
All studies (16)
Frequently asked
Is bacitracin safe to use on open wounds every day?
Bacitracin ointment is widely used for minor wound care and has been studied in clinical settings including pediatric burn care, where single-application bacitracin-containing dressings produced outcomes equivalent to daily silver sulfadiazine with fewer dressing changes. However, a 2026 review highlighted that topical antibiotics including bacitracin carry high rates of allergic sensitization and that contemporary antimicrobial stewardship increasingly favors non-antibiotic antiseptics for wound care, particularly in chronic or complex wound environments. For routine minor wound care, topical bacitracin is generally considered appropriate short-term. For ongoing or chronic use, please consult a healthcare provider.
Can bacitracin be used to treat MRSA infections?
Standard topical bacitracin alone has limited established evidence for MRSA eradication in clinical settings. Preclinical research has explored bacitracin-loaded nanocomposite hydrogels that showed a 4-log reduction in MRSA biofilm burden and accelerated wound closure in murine models (PMID 42646203, PMID 41846420). N-terminal modified bacitracin A derivatives and a lead analogue (Bac-51) have shown up to 256-fold improved potency against MRSA in laboratory settings (PMIDs: 42720474, 40746262), but these are investigational compounds not available for clinical use. Over-the-counter bacitracin ointment is not indicated as a standalone treatment for established MRSA infections.
Why is bacitracin in so many over-the-counter antibiotic products?
Bacitracin targets a bacterial process — recycling of the lipid carrier undecaprenyl pyrophosphate — that is essential for building bacterial cell walls (PMIDs: 42709865, 42725977). This mechanism is distinct from beta-lactams and other common antibiotics, making it useful in combination products. Its combination with neomycin and polymyxin B (as in triple antibiotic ointments) provides broad-spectrum coverage: in vitro burn wound studies found compounded bacitracin-containing preparations effective against 100% of bacterial isolates tested.
Is bacitracin used in livestock feed, and does this affect antibiotic resistance?
Yes — bacitracin methylene disalicylate (BMD) and bacitracin zinc have been widely used as antimicrobial growth promoters in poultry and swine (PMIDs: 42553710, 42736216, 42797933). Environmental monitoring studies have found bacitracin resistance genes (bacA and related genes) in wastewater, irrigated produce, and soil environments, raising public health concerns about AMR selection pressure (PMIDs: 42650720, 42562511). Multi-omics research in broilers found that in-feed bacitracin zinc altered cecal microbiota composition and enriched potentially pathogenic bacterial phyla compared to natural alternatives.
Can bacitracin be combined with ceftriaxone or other antibiotics to fight drug-resistant infections?
This is an active area of preclinical research. A 2023 study showed that bacitracin displays synergistic in vitro activity with ceftriaxone against Neisseria gonorrhoeae, including the high-level ceftriaxone-resistant FC428 clone, because their mechanisms separately target bacterial cell wall synthesis. Statin-induced lipid carrier stress has been shown to synergize with bacitracin's mechanism against MRSA and Streptococcus pneumoniae in preclinical models. These findings are not yet translated to clinical recommendations.