In Vitro Study of the Effect of Cationic Biocides on Bacterial Population Dynamics and Susceptibility

Abstract

Cationic biocides (CBs) are widely used in domestic and public hygiene and to control biofouling and microbial contamination in industry. The increased use of biocides has led to concern regarding possible reductions in biocide effectiveness. Domestic drain microcosms were stabilized for 5 months and then exposed to polyhexamethylene biguanide (PHMB) at 0.1, 0.2, and 0.4g liter ؊1 over 6 months and characterized throughout by differential culture, together with eubacterial-specific PCR-denaturing gradient gel electrophoresis. Additionally, MICs and minimal bactericidal concentrations (MBCs) for bacteria previously isolated from a domestic drain (n ‫؍‬ 18) and the human skin (n ‫؍‬ 13) were determined before, during, and after escalating, sublethal exposure (14 passages) to two quaternary ammonium compounds (QAC1 and QAC2), the bisbiguanide chlorhexidine (CHX), and PHMB. Exposure of the drain microcosm to PHMB did not decrease the total viable count although significant (P < 0.01) decreases in recovery were observed for the gram-positive cocci with associated clonal expansion of pseudomonads (from ca. 0.1% of the population to ca. 10%). This clonal expansion was also manifested as elevations in bacteria that could grow in the presence of PHMB, CHX, and QAC1. Decreases in susceptibility (greater than twofold) occurred for 10/31 of the test bacteria for QAC1, 14/31 for QAC2, 10/31 for CHX, and 7/31 for PHMB. Exposure of microcosms to PHMB targeted gram-positive species and caused the clonal expansion of pseudomonads. In terms of prolonged-sublethal passage on CBs, exposure to all the biocides tested resulted in susceptibility decreases for a proportion of test bacteria, but refractory clones were not generated.Cationic biocides (CBs) have been in use since the 1930s for surface disinfection and topical antisepsis (for a review, see reference 15). Broad-spectrum activity and relatively low toxicity have led to increased deployment of these compounds in medicated dressings (37), in contact lens cleaning solutions (5), in swimming pools to control microbial growth (16), and in domestic cleaning products (29). While CBs are a chemically diverse group of compounds, their mode of action normally involves interaction with the cell envelope, displacing divalent cations. Subsequent interactions with membrane proteins and the lipid bilayer depend upon the specific nature of the biocide, but generally CB exposure results in membrane disruption and lethal leakage of cytoplasmic materials (22).CBs have a range of structures that can be categorized according to the number of cationic groupings per molecule. The quaternary ammonium compounds ([QACs] e.g., cetrimide) are often monocationic surfactants generally containing one quaternary nitrogen associated with at least one major hydrophobic component. The bisbiguanides (e.g., chlorhexidine [CHX]) have two cationic groups separated by a hydrophobic bridging structure (hexamethylene) while the polymeric biguanides (e.g., polyhexamethylene biguanide [PHMB]) are polycationic linear p...

Variable Effects of Exposure to Formulated Microbicides on Antibiotic Susceptibility in Firmicutes and Proteobacteria

“…A system previously validated to be highly selective for changes in antimicrobial susceptibility (26,27) was used. Reproducible ca.…”

Usage of Fumarate by Sulphate-Reducing Bacteria Desulfomicrobium sp. CrR3 and Desulfotomaculum sp.

“…Стійкість мікроорганізмів до нього також практично не формується. Якщо в окремих випадках адаптація до суббактеріостатичних концентрацій ПГМГ і можлива, то не виникає перехресна резистентність [1,14]. Зростання стійкості мікроорганізмів до ПГМГ супрово джується збільшенням чутливості до інших катіонактивних препаратів.…”

Skin bacteria after chlorhexidine exposure—is there a difference in response to human β-Defensin-3?

“…We found a significant decrease in hBD-3 susceptibility for both exposure times 261 only for S. capitis 19/2 and after 3h exposure to hBD-3 for S. warneri 16/1.In three cases 262 more CHG-exposed bacteria were killed by hBD-3 compared to non-exposed bacteria, al-263 though in one case the difference was less than 0.4 log-scales (Figures 1-5). Exposure to CH has been reported to result in adaptation, e.g., in skin bacteria [23], and 274 thus, changes susceptibility to different antibiotics and biocides [15][16][17][18][19][20][21][22]. Therefore an influ-275 ence of previous exposure to CHG on susceptibility to hBD-3 is possible due to the structural 276 properties of both substances and their comparable mode of action.…”

“…48 49 It has been reported that different bacterial species are able to adapt to sub-lethal concentra-50 tions of CH [15][16][17][18][19][20] and that this adaptation affects the susceptibility to different biocides [21] 51 and antibiotics in Pseudomonas stutzeri [16,21,22]. Moore et al showed that different skin 52 bacteria were able to adapt to CH after repeated exposure [23]. 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Reichel et al Bacterial response to human β-Defensin-3 after chlorhexidine exposure 5 To the best of our knowledge, there are no studies on whether CHG exposure changes the 55 response of Gram-positive bacteria to antimicrobial peptides, such as hBD-3.…”