Antimicrobial mechanisms of ortho-phthalaldehyde action

• Type: Article in International Scientific Journal
• Date: 2007

Authors

Manuel Simoes (Author) Other; Lucia C Simoes (Author) Other; Sara Cleto (Author) Other; Idalina Machado (Author) Other; Maria O Pereira (Author) Other; Maria J Vieira (Author) Other

Journal

Title: Journal of Basic Microbiology

Vol. 47

Pages: 230-242

ISSN: 0233-111X

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 21 Citations

Scopus - 31 Citations

Scientific classification

FOS: Natural sciences > Biological sciences

Other information

Authenticus ID: P-004-9S2

DOI: 10.1002/jobm.200610280

Abstract (EN): Biocides generally have multiple biochemical targets. Such a feature easily entangles the analysis of the mechanisms of antimicrobial action. In this study, the action of the dialdehyde biocide ortho-phtalaldehyde (OPA), on bacteria, was investigated using the Gram-negative Pseudomonas fluorescens. The targets of the biocide action were studied using different bacterial physiological indices. The respiratory activity, membrane permeabilization, physico-chemical characterization of the bacterial surfaces, outer membrane proteins (OMP) expression, concomitant influence of pH, contact time and presence of bovine serum albumin (BSA) on respiratory activity, morphological changes and OPA-DNA interactions were assessed for different OPA concentrations. With the process conditions used, the minimum inhibitory concentration was 1500 mg/l, the concentration to promote total loss of bacterial culturability was 65 mg/l and the concentration needed to inactivate respiratory activity was 80 mg/l. These data are evidence that culturability and respiratory activity were markedly affected by the biocide. OPA lead, moreover, to a significant change in cell surface hydrophobicity and induced propidium iodide uptake. Such results suggest cytoplasmic membrane damage, although no release of ATP was detected. At pH 5, the bactericidal action of OPA was stronger, though not influenced by BSA presence. Nevertheless, at pH 9, BSA noticeably (p < 0.05) impaired biocide action. A time-dependent effect in OPA action was evident when contemplating respiratory activity variation, mainly for the lower exposure times. Scanning electron microscopy allowed to detect bacterial morphological changes, translated on cellular elongation, for OPA concentrations higher than 100 mg/l. Interferences at DNA level were, however, restricted to extreme biocide concentrations. The overall bactericidal events occurred without detectable OMP expression changes. In conclusion, the results indicated a sequence of events responsible for the antimicrobial action of OPA: it binds to membrane receptors due to cross-linkage; impairs the membrane functions allowing the biocide to enter through the permeabilized membrane; it interacts with intracellular reactive molecules, such as RNA, compromising the growth cycle of the cells and, at last, with DNA.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13