Inanimate Surfaces and Air Contamination with Multidrug Resistant Species of Staphylococcus in the Neonatal Intensive Care Unit Environment

Antimicrobial properties of hindered amine light stabilizers in polymer coating materials and their mechanism of action

UV-stabilizers are a class of additives that provide extended polymer resistance to UV-degradation, but have also been suggested to have antimicrobial activity, potentially preventing the spread of pathogens, and inhibiting microbial-induced biodegradation. In this work, we incorporated different UV-stabilizers, a hindered amine light stabilizer (HALS), Tinuvin 770 DF and Tinuvin PA 123, or a hybrid HALS/UV-absorber, Tinuvin 5151, in polyurethane formulations to produce lacquer-films, and tested their antimicrobial activity against Staphylococcus aureus (methicillin-resistant and -sensitive strains), Escherichia coli and Candida albicans. Lacquer-films incorporated with Tinuvin 770 DF showed strong antimicrobial performance against bacteria and fungi, while maintaining cytocompatibility. The mechanism of action revealed a positive relationship between Tinuvin 770 DF concentration, microbial death, and reactive nitrogen species (RNS), suggesting that RNS produced during autoxidation of Tinuvin 770 DF is responsible for the antimicrobial properties of this UV-stabilizer. Conversely, lacquer-films incorporated with Tinuvin 5151 or Tinuvin PA 123 exhibited no antimicrobial properties. Collectively, these results highlight the commercial potential of Tinuvin 770 DF to prevent photo- and biodegradation of polymers, while also inhibiting the spread of potentially harmful pathogens. Furthermore, we provide a better understanding of the mechanism underlying the biocidal activity of HALS associated to autooxidation of the amine group.

Molecular distribution of biocide resistance genes and susceptibility to biocides among vancomycin resistant Staphylococcus aureus (VRSA) isolates from intensive care unit (ICU) of cardiac hospital- A first report from Pakistan

Background

The study was conducted with the aim to investigate the VRSA isolates in terms of their susceptibility to routinely used biocides influenced by the co-occurrence of biocide resistant gene (BRGs) and efflux pumps genes.

Methodology

Frequently touched surfaces within intensive care unit (ICU) of cardiac hospital were classified into three primary sites i.e., structure, machines and miscellaneous. Over a period of six months (January 2021 to July 2021) twenty three swabs samples were collected from these sites. Subsequently, these samples underwent both phenotypic and molecular methods for VRSA isolation and identification. Susceptibility and efficacy testing of biocides (benzalkonium chloride (BAC), cetrimide (CET) and chlorhexidine gluconate (CHG)) were evaluated using microdilution broth and suspension method. Furthermore, specific primers were used for singleplex PCR targeting BRGs (cepA, qacA, and qacE) and efflux pump (norA, norB, norC, sepA, mepA and mdeA) associated genes.

Results

We found that 72.2 % S. aureus demonstrate the presence of vanA or vanB genes with no significant difference among three sites (p > 0.05). cepA is the most dominant BRGs followed by qacA and qacE from structure site as compared to other sites (p < 0.05). BAC showed reduced biocide susceptibility and MIC50. There was no significant difference between presence or absence of BRGs and high MIC values of VRSA isolates from all three sites. However, efflux pump genes (EFPGs) particularly norA and norA + sepA had a significant association with BRGs and reduced biocide.

Conclusion

BAC is the most effective disinfectant against VRSA. Proper and controlled use of BAC is required to overcome the VRSA contamination. We recommend continuous monitoring of the BRGs prevalence for better prevention of microorganism dissemination and infection control in hospitals.