In vitro–in vivo sequence studies as a method of selecting the most efficacious alcohol-based solution for hygienic hand disinfection

Adaptation and validation of a method for evaluating the bactericidal activity of ethyl alcohol in gel format 70% (w/w)

Ethyl alcohol 70% (w/w) is a broad-spectrum bactericidal agent that is mandatorily marketed as a gel in Brazil since 2002. However, there is no method described for the microbiological quality control of surface disinfectants in the form of gel, which makes it impossible to monitor the effectiveness of these products by the Health Surveillance. Thus, the present study aimed to adapt an analytical method and validate it so that it is possible to evaluate the bactericidal activity of ethyl alcohol-based disinfectants at 70% (w/w) in gel form. The proposed analytical method is an adaptation of a method developed by the Association of Official Analytical Chemists (AOAC), which is currently used to evaluate the bacterial activity of disinfectants in the form of spray and aerosol. The method consisted of challenging the disinfectant by putting it in contact with 60 carriers - previously contaminated with the test microorganism - during the contact time established by the manufacturer. The bacteria used in this work were Staphylococcus aureus CBRVS 00039 ATCC 6538, Salmonella enterica CBRVS 00028 ATCC 10708, and Pseudomonas aeruginosa CBRVS 00025 ATCC 15442. The parameters chosen for the validation of the method were: matrix effect, robustness, and repeatability. The experiments performed with a disinfectant matrix showed that there is no interference of the gel on the effectiveness of alcohol. Satisfactory results regarding the evaluation of bactericidal activity were obtained for the three microorganisms tested when the volume of 100 μL of disinfectant was applied. The method also showed good repeatability, as it proved to be robust with modification of incubation times, equipment and analysts. The development and validation of this method were extremely important for the quality monitoring of these products, besides being the first method described for the evaluation of gel disinfectants.

Bla-OXA48 gene microorganisms outbreak, in a tertiary Children's Hospital, Over 3 years (2012-2014): Case Report

RATIONALE

Carbapenem-resistant Enterobacteriaceae are an emerging problem in children. Nosocomial spread remains the principal risk factor for acquisition of these microorganisms.

PATIENTS CONCERNS

We describe an outbreak of Klebsiella pneumoniae OXA48 (KOXA48) in a tertiary children's hospital during the years 2012 to 2014, as well as the preventive measures put in place in colonized and infected cases.

DIAGNOSES

We studied, "in vitro," the KOXA48 susceptibility to antiseptics and surface disinfectants. Moreover, an epidemiological surveillance of infection or colonization by these microorganisms, with molecular typing of the KOXA48, was performed, and carbapenemase genes were confirmed by polymerase chain reaction (PCR).

INTERVENTIONS

The bundles recommended (early detection, cohorting of children and health care workers [HCW], contact precautions, etc.) to control the KOXA48 outbreak were taken from those described in the centers for disease control (CDC) 2012 guide, and adapted according to our experience in controlling other outbreaks.

OUTCOMES

All the KOXA48 microorganisms isolated from children belonged to the same strain (ST11) and were susceptible to alcohol solutions but not the surface disinfectant previously employed in our hospital (tensoactive). We reinforced the surface disinfection using a double application (tensoactive + alcohol). The outbreak of KOXA48 begun in 2012 (16 cases in neonatal intensive care unit [NICU] and 1 in pediatric intensive care unit [PICU]) ended before the end of the same year and was not transmitted to new patients in 2013 to 2014, despite readmission of some colonized cases, in intensive care units (ICUs) and other units, of our children hospital.

LESSONS

Infected children are the tip of the iceberg (3/17) of KOXA48 prevalence making it necessary to identify the cases colonized by these bacteria. At the beginning of the outbreak, the susceptibility of the epidemic strain to antiseptics and surface disinfectants should be studied. Moreover, the measures taken (cohorts, contact precautions, etc.) must be thorough in both colonized and infected cases, immediately, after microbiological diagnosis.

Evaluation of antimicrobial persistent activity of alcohol-based hand antiseptics against bacterial contamination

The purpose of this study was to evaluate persistent activity of three alcohol-based antiseptics widely used in the clinical routine containing chlorhexidine, triclosan or mecetronium after hand disinfection. Four tests were used to evaluate the antimicrobial activity of antiseptics on: (i) resident microbiota; (ii) nutrient agar plates (NAP) subsequently inoculated with a test organism; and transient microbiota acquired by contact with dry hands (iii), or (iv) a wet inert surface that had been artificially contaminated. Four reference strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis) and an Acinetobacter baumannii strain responsible for a hospital outbreak were used as transient microbiota. Antimicrobial activity was calculated according to the CFUs reduction by reference to non-disinfected control hands. The antiseptics were applied according to European Standard EN1500. Solutions containing chlorhexidine or triclosan showed some persistent effects on transient microbiota on inert humid surfaces and NAP, but not on contaminated dry hands. Solutions containing mecetronium showed no persistent effect on transient flora in any of the trials. All alcohol-based antiseptics tested were more effective against resident flora than soap. No persistent activity was observed for A. baumannii in any of the trials. Chlorhexidine and triclosan are preferred when an antiseptic with persistent activity is desired, but a moist environment appears to be necessary for that antibacterial activity. Accordingly, relevant conclusions regarding the persistent activity of antiseptics for clinical practice and protection against bacterial contamination cannot be derived from this study for the alcoholic solutions tested.

Fluorescence assay for evaluating microbicidal activity of hand antiseptics

We developed a fluorescent β-d-glucuronidase activity (BGA)-based assay for detecting and quantifying Escherichia coli in samples to assess the biocide efficacy of hand antiseptics. The fluorescence level is proportional to the number of viable E. coli organisms present. We compared our assay results to those of the E. coli plate count method specified by the European standard for testing hygienic hand rub disinfectant products (EN1500). The plate count method requires excessive handling and materials and is not valid if the number of organisms per plate is too low or high for counting in many of the samples. We optimized the fluorescent assay based on the cleavage of 4-methylumbelliferyl-β-d-glucuronide by adding 4-nitrophenyl-β-d-glucuronide, a nonfluorogenic BGA substrate, to induce glucuronidase activity and reduce assay time. Furthermore, our method can be automated and eliminates the need for multiple dilutions. Fluorescence was temporally monitored, and the time required to reach a specific value of fluorescence was correlated with the initial number of viable E. coli organisms on the samples. There was a positive correlation (P < 0.05) with a high correlation coefficient (R(2) = 0.82) between the E. coli counts by plate count and fluorescence methods. Reported effects in fluorescent BGA were compared to the EN1500 plate count method with five hand disinfectants. We found our method more advantageous, because it was as sensitive as the EN1500 method, requires less time to complete, and is less expensive and less laborious than conventional plating techniques.

Lasting hand self-disinfection: A backup for hospital hand hygiene?

BACKGROUND

Hand disinfection should be performed on the occasion of 5 separate moments during patient care, but some occasions are skipped. Can using hand antiseptics with residual effect reduce the problem of infection spread? We evaluated a 30-minute residual effect by different antiseptic products on endogenous and acquired microbiota.

METHODS

The products tested were 2% and 5% chlorhexidine, 1% and 10% iodine povidone, 60° n-propanol, 0.2% mecetronium + isopropanol, and 0.6% chlorhexidine + isopropanol + 0.1% benzalconium chloride. The microorganisms identified were 3 ATCC and 9 multiresistant strains isolated from intensive care unit patients (used as acquired microbiota). Logarithmic (log10) reductions of the colony forming units obtained with each antiseptic product and for each microorganism were calculated via in vivo (6 volunteers) and in vitro tests.

RESULTS

The better in vivo and in vitro products with a residual effect > 2 log10 after 30 minutes on hands were 2%-5% chlorhexidine and 0.6% chlorhexidine + isopropanol + 0.1% benzalconium chloride. This reduction was significantly different (P < .01) from the other 4 antiseptics. This residual effect (> 2 log10) can be considered a self-disinfecting hand status in daily practice.

CONCLUSIONS

Hand antiseptics used in hospitals must pass tests of residual efficacy (after 30 minutes on acquired microbiota) showing a reduction > 2 log10 in vivo and in vitro. A good product can be the mixture of chlorhexidine + alcohol + benzalconium chloride.

Skin microbiota: overview and role in the skin diseases acne vulgaris and rosacea

As the first barrier to environmental exposures, human skin has developed an integrated immune system to protect the inner body from chemical, physical or microbial insults. Microorganisms inhabiting superficial skin layers are known as skin microbiota and include bacteria, viruses, archaea and fungi. The microbiota composition is crucial in the instruction and support of the skin's immune system. Changes in microbiota can be due to individual, environmental or behavioral factors, such as age, climate, hygiene or antibiotic consumption, which can cause dysbiosis. The contribution of skin microbiota to disease development is known in atopic dermatitis, where there is an increase in Staphylococcus aureus. Culture-independent studies have enabled more accurate descriptions of this complex interplay. Microbial imbalance is associated with the development of various diseases. This review focuses on microbial imbalances in acne vulgaris and rosacea.