Towels proved to be excellent conditions for each bacteria to survive, however chemical composition of the textiles affected differently the survival of Gram-positive and Gram-negative bacteria. These findings could be useful in searching for the source of outbreaks. Organic contamination of the textiles can increase the survival of desiccation-sensitive bacteria, therefore nutrient-rich inoculating medium is recommended in survival studies.
Healthcare-associated infections are of global concern, and textiles can contribute to the transmission of pathogens. In this study, we examined quantitatively the survival capability of 60 multidrug-resistant bacterial strains from four species ( Klebsiella pneumoniae, Acinetobacter baumannii, Staphylococcus aureus and Enterococcus faecium) on untreated cotton textile in clinically relevant incubation periods. We determined the antibacterial efficiency of textiles treated either with quaternary ammonium compound (QAC)-containing Sanitized T99-19 liquid (50 m/m% Dimethyltetradecyl (3-(trimethoxysilyl)propyl) ammonium-chloride) or with silver salt-containing Sanitized T27-22 Silver liquid (2 m/m% AgCl and 8 m/m% TiO2) as well. Finally, we compared the results of the healthcare-associated, multidrug-resistant strains and antibiotic-sensitive, quality control standard strains (ATCC 25922, ATCC 11105 Escherichia coli, and ATCC 25923, ATCC 6538 Staphylococcus aureus) often used in antimicrobial efficiency tests. The results revealed that all investigated multidrug-resistant bacteria are able to survive on untreated cotton textile and pose health risk in hospitals. During one day the T27-22-Silver-treated textile was able to eliminate most of the Gram-positive pathogens, reducing the risk of cross-contamination, but none of the examined agents destroyed the multidrug-resistant, Gram-negative isolates. The antibiotic-susceptible and the multidrug-resistant Staphylococcus aureus strains had similar survival capability and biocide-tolerance, while the risk of infections caused by multidrug-resistant, Gram-negative pathogens could be extremely underestimated using only ATCC Escherichia coli standard strains. Our results also draw attention to the careful evaluation of antimicrobial efficiency tests and indicate that a significant reduction of bacterial count does not necessarily mean significant antibacterial efficiency that would be suitable to avoid infections.
Silver is used extensively in both hospitals and outpatient clinics as a disinfectant coating agent on various devices. Resistance to silver was recently reported as an emerging problem in Enterobacteriaceae. Multidrug-resistant high-risk clones of Klebsiella pneumoniae are common causes of serious healthcare-associated infections worldwide posing a serious threat to patients. In this study, we investigated the capacity of both high-risk (CG14/15 and CG258) and minor clone strains of K. pneumoniae to develop resistance to silver. Resistance was induced in vitro in silver-susceptible but otherwise multidrug-resistant clinical isolates. Genetic alterations in the silver-resistant derivative strains with regard to the silver-susceptible isolates were investigated by whole-genome sequencing. The transferability of high-level resistance to silver was also tested. We demonstrated that the high-level resistance to silver can quickly evolve as a consequence of a single-point mutation either in the cusS gene of the chromosomally encoded CusCFBARS efflux system and/or in the silS gene of the plasmid-encoded Copper Homeostasis and Silver Resistance Island (CHASRI) coding also for a metallic efflux. The minimal inhibitory concentrations (MICs) of the strains increased from 4 mg/L (23.5 μM) AgNO to >8,500 mg/L (>50,000 μM) AgNO during induction. Harboring the CHASRI proved an important selective asset for K. pneumoniae when exposed to silver. Successful conjugation experiments using Escherichia coli K12 J5-3 as recipient showed that high-level silver resistance can transmit between strains of high-risk clones of K. pneumoniae (ST15 and ST11) and isolates from additional species of Enterobacteriaceae. The lack of fitness cost associated with the carriage of the CHASRI in a silver-free environment and the presence of the RelEB toxin-antitoxin system on the conjugative plasmids could advance the dissemination of silver resistance. Our results show that multidrug-resistant high-risk clones of K. pneumoniae are capable of evolving and transmitting high-level resistance to silver. This observation should warrant a more judicious use of silver coated-devices to prevent the extensive dissemination of silver resistance.
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