From the Guidelines
Mupirocin is not effective against most gram-negative bacteria due to their outer membrane limiting its penetration, and alternative antibiotics should be used for infections caused by these organisms. The provided evidence does not directly address the effectiveness of mupirocin against gram-negative bacteria, but it does discuss the management of various infections, including those caused by gram-negative bacteria 1. Mupirocin works by inhibiting bacterial protein synthesis by binding to bacterial isoleucyl-tRNA synthetase, which prevents the incorporation of isoleucine into bacterial proteins. It is most effective against Staphylococcus aureus (including MRSA), Streptococcus species, and some gram-positive anaerobes. While it may show some activity against certain gram-negative organisms like Haemophilus influenzae and Neisseria species, most gram-negative bacteria are inherently resistant to mupirocin due to differences in their cell wall structure and permeability. For example, the evidence discusses the use of various antibiotics, including beta-lactams, fluoroquinolones, and carbapenems, for the treatment of infections caused by gram-negative bacteria 1.
- Key points to consider:
- Mupirocin is primarily effective against gram-positive bacteria
- Gram-negative bacteria are inherently resistant to mupirocin due to their outer membrane
- Alternative antibiotics should be used for infections caused by gram-negative bacteria
- Mupirocin is commonly used for topical treatment of impetigo, folliculitis, and eradication of nasal Staphylococcus aureus colonization
- The evidence provided does not support the use of mupirocin as a primary treatment for infections caused by gram-negative bacteria, and instead recommends the use of other antibiotics, such as beta-lactams, fluoroquinolones, and carbapenems 1.
From the FDA Drug Label
Microbiology: Mupirocin is an antibacterial agent produced by fermentation using the organism Pseudomonas fluorescens. It is active against a wide range of gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). It is also active against certain gram-negative bacteria Mupirocin is active against certain gram-negative bacteria. However, the specific types of gram-negative bacteria that mupirocin is effective against are not specified in the label.
- The clinical significance of the in vitro data is unknown 2. Therefore, while mupirocin may have some activity against gram-negative bacteria, the extent and clinical significance of this activity are not clear.
From the Research
Mupirocin's Effectiveness Against Gram-Negative Bacteria
- Mupirocin is active against a wide range of Gram-positive bacteria, but its effectiveness against Gram-negative bacteria is limited 3, 4.
- According to a study published in 1985, mupirocin showed a high level of activity against certain Gram-negative bacteria, including Haemophilus influenzae and Neisseria gonorrhoeae, but was much less active against most Gram-negative bacilli and anaerobes 5.
- Another study published in 1991 stated that mupirocin is moderately active against Gram-negative bacteria 3.
- However, a review of mupirocin's antibacterial activity published in 1986 noted that it has less activity against most Gram-negative bacteria 4.
- A more recent study published in 2024 focused on the mechanisms of mupirocin resistance and hyper-resistance, but did not provide new information on its effectiveness against Gram-negative bacteria 6.
- It is worth noting that mupirocin is not effective against all Gram-negative organisms, as stated in a study published in 1990 7.