Exploring a link between pathogens structure's and resistance to disinfectant

João, Inês; Reis, Lúcia; Carvalho, Patrícia; Duarte, Aida; Jordão, Luísa

http://hdl.handle.net/10400.18/1822

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In recent years healthcare-associated infections (HAIs) infections have gained growing importance. Among their etiological agents are classical (e.g. K. pneumoniae, S. aureus) and emergent pathogens, previously neglected, such as nontuberculous mycobacteria (NTM). The ability to resist to antibacterial agents, such as antibiotics and disinfectants, is shared by all of them. Here we aim to establish a link between bacterial virulence, disinfectant resistance and structure. Bacterial reference strains and clinical isolates were grown in adequate medium. NTM susceptibility test to antibiotics was evaluated by broth microdilution method and interpreted according to NCCLS guidelines in a previous work. The susceptibility to disinfectants (hydrogen peroxide, ammonium quaternary salts [AQS] and glutaraldehyde [GA]) was performed by two different methods: broth microdilution and diffusion in solid medium. In order to evaluate the effect of these agents in bacteria a scanning electron microscopy (SEM) study was performed. Hydrogen peroxide was the less effective disinfectant. The efficiencies of QAS and GA were similar. Nevertheless, among NTM we identified one isolate resistant to all disinfectants tested (Table 1). The SEM analysis showed that different disinfectants caused different effects on bacteria suggesting different action mechanisms (Figure 1). Bacterial resistance to antibiotics and disinfectants vary in the same manner. The mechanisms involved in the resistance are not fully elucidated and more studies are needed to provide effective conclusions. Biofilm formation can be part of the mechanism involved both in antibiotic/disinfectant resistance development and infection propagation.