Resistance Mechanisms to Antimicrobial Peptides in Gram-Positive Bacteria

Abstract

With the alarming increase of infections caused by pathogenic multidrug-resistant bacteria over the last decades, antimicrobial peptides (AMPs) have been investigated as a potential treatment for those infections, directly through their lytic effect or indirectly, due to their ability to modulate the immune system. There are still concerns regarding the use of such molecules in the treatment of infections, such as cell toxicity and host factors that lead to peptide inhibition. To overcome these limitations, different approaches like peptide modification to reduce toxicity and peptide combinations to improve therapeutic efficacy are being tested. Human defense peptides consist of an important part of the innate immune system, against a myriad of potential aggressors, which have in turn developed different ways to overcome the AMPs microbicidal activities. Since the antimicrobial activity of AMPs vary between Gram-positive and Gram-negative species, so do the bacterial resistance arsenal. This review discusses the mechanisms exploited by Gram-positive bacteria to circumvent killing by antimicrobial peptides. Specifically, the most clinically relevant genera, Streptococcus spp., Staphylococcus spp., Enterococcus spp. and Gram-positive bacilli, have been explored.

A Real-Time Thermal Sensor System for Quantifying the Inhibitory Effect of Antimicrobial Peptides on Bacterial Adhesion and Biofilm Formation

“…The effect of this AMP might be more efficient at these high concentrations against members of Gram-positive species, a hypothesis that needs to be verified in further studies. The differences between the cell walls of Gram-positive and -negative bacteria according the murein layer and the composition might be an explanation for the higher MIC values of the two S. aureus strains compared the tested E. coli [ 75 ]. Furthermore, Gram-positive bacteria are able to partially neutralize their cell wall to resist AMPs [ 76 , 77 ].…”

Effects of Propolis on Infectious Diseases of Medical Relevance

“…The genus Staphylococcus causes different infections in the human population like impetigo, scalded skin syndrome, toxic shock syndrome, pneumonia, endocarditis, and urinary tract infections, among others [ 23 ]. Some species of this genus are resistant to antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA) [ 24 ].…”

Virulence and Antimicrobial Resistance in Canine Staphylococcus spp. Isolates

“…Regardless of the ways of and reasons for infection development, a frequent issue is antibiotic treatment. Indeed, staphylococci are not outsiders to the antimicrobial resistance and multidrug resistance (MDR) problem [ 17 ]. Different authors have reported a decreased susceptibility to β-lactams, clindamycin, tetracyclines, and (less frequently) fluoroquinolones and trimethoprim-sulfamethoxazole [ 10 , 11 , 12 , 18 , 19 , 20 ].…”