Staphylococcus aureus on hand surface and nasal carriage in patients with atopic dermatitis

Staphylococcus aureus from Atopic Dermatitis Patients: Its Genetic Structure and Susceptibility to Phototreatment

We characterized the population of Staphylococcus aureus from patients with atopic dermatitis (AD) in terms of (i) genetic diversity, (ii) presence and functionality of genes encoding important virulence factors: staphylococcal enterotoxins (sea, seb, sec, sed), toxic shock syndrome 1 toxin (tsst-1), and Panton-Valentine leukocidin (lukS/lukF-PV) by spa typing, PCR, drug resistance profile determination, and Western blot. We then subjected the studied population of S. aureus to photoinactivation based on a light-activated compound called rose bengal (RB) to verify photoinactivation as an approach to effectively kill toxin-producing S. aureus. We have obtained 43 different spa types that can be grouped into 12 clusters, indicating for the first-time clonal complex (CC) 7 as the most widespread. A total of 65% of the tested isolates had at least one gene encoding the tested virulence factor, but their distribution differed between the group of children and adults, and between patients with AD and the control group without atopy. We detected a 3.5% frequency of methicillin-resistant strains (MRSA) and no other multidrug resistance. Despite genetic diversity and production of various toxins, all isolates tested were effectively photoinactivated (bacterial cell viability reduction ≥ 3 log10 units) under safe conditions for the human keratinocyte cell line, which indicates that photoinactivation can be a good option in skin decolonization. IMPORTANCE Staphylococcus aureus massively colonizes the skin of patients with atopic dermatitis (AD). It is worth noting that the frequency of detection of multidrug-resistant S. aureus (MRSA) in AD patients is higher than the healthy population, which makes treatment much more difficult. Information about the specific genetic background of S. aureus accompanying and/or causing exacerbations of AD is of great importance from the point of view of epidemiological investigations and the development of possible treatment options.

Quantification and risks associated with bacterial aerosols near domestic greywater-treatment systems

Greywater (GW) reuse can alleviate water stress by lowering freshwater consumption. However, GW contains pathogens that may compromise public health. During the GW-treatment process, bioaerosols can be produced and may be hazardous to human health if inhaled, ingested, or come in contact with skin. Using air-particle monitoring, BioSampler®, and settle plates we sampled bioaerosols emitted from recirculating vertical flow constructed wetlands (RVFCW) - a domestic GW-treatment system. An array of pathogens and indicators were monitored using settle plates and by culturing the BioSampler® liquid. Further enumeration of viable pathogens in the BioSampler® liquid utilized a newer method combining the benefits of enrichment with molecular detection (MPN-qPCR). Additionally, quantitative microbial risk assessment (QMRA) was applied to assess risks of infection from a representative skin pathogen, Staphylococcus aureus. According to the settle-plate technique, low amounts (0-9.7×10(4)CFUm(-2)h(-1)) of heterotrophic bacteria, Staphylococcus spp., Pseudomonas spp., Klebsiella pneumoniae, Enterococcus spp., and Escherichia coli were found to aerosolize up to 1m away from the GW systems. At the 5m distance amounts of these bacteria were not statistically different (p>0.05) from background concentrations tested over 50m away from the systems. Using the BioSampler®, no bacteria were detected before enrichment of the GW-aerosols. However, after enrichment, using an MPN-qPCR technique, viable indicators and pathogens were occasionally detected. Consequently, the QMRA results were below the critical disability-adjusted life year (DALY) safety limits, a measure of overall disease burden, for S. aureus under the tested exposure scenarios. Our study suggests that health risks from aerosolizing pathogens near RVFCW GW-treatment systems are likely low. This study also emphasizes the growing need for standardization of bioaerosol-evaluation techniques to provide more accurate quantification of small amounts of viable, aerosolized bacterial pathogens.

Toll-like receptors: role in dermatological disease

Toll-like receptors (TLRs) are a class of conserved receptors that recognize pathogen-associated molecular patterns (PAMPs) present in microbes. In humans, at least ten TLRs have been identified, and their recognition targets range from bacterial endotoxins to lipopeptides, DNA, dsRNA, ssRNA, fungal products, and several host factors. Of dermatological interest, these receptors are expressed on several skin cells including keratinocytes, melanocytes, and Langerhans cells. TLRs are essential in identifying microbial products and are known to link the innate and adaptive immune systems. Over the years, there have been significant advances in our understanding of TLRs in skin inflammation, cutaneous malignancies, and defence mechanisms. In this paper, we will describe the association between TLRs and various skin pathologies and discuss proposed TLR therapeutics.

Antimicrobial peptides, skin infections, and atopic dermatitis

The innate immune system evolved more than 2 billion years ago to first recognize pathogens then eradicate them. Several distinct defects in this ancient but rapidly responsive element of human immune defense account for the increased incidence of skin infections in atopics. These defects include abnormalities in the physical barrier of the epidermis, alterations in microbial pattern recognition receptors such as toll receptors and nucleotide binding oligomerization domains, and a diminished capacity to increase the expression of antimicrobial peptides during inflammation. Several antimicrobial peptides are affected including; cathelicidin, HBD-2, and HBD-3, which are lower in lesional skin of atopics compared with other inflammatory skin diseases, and dermcidin, which is decreased in sweat. Other defects in the immune defense barrier of atopics include a relative deficiency in plasmacytoid dendritic cells. In the future, understanding the cause of these defects may allow therapeutic intervention to reduce the incidence of infection in atopic individuals and potentially decrease the severity of this disorder.

Role of bacterial pathogens in atopic dermatitis

The skin of atopic dermatitis (AD) patients exhibits a striking susceptibility to colonization and infection with Staphylococcus aureus. This review summarizes our understanding about the role of S. aureus in AD. Indeed, S. aureus colonization is both a cause and a consequence of allergic skin inflammation. The mechanisms that allergic skin inflammation of AD promotes the increase of S. aureus colonization include skin barrier dysfunction, increased synthesis of the extracellular matrix adhesins for S. aureus, and defective innate immune responses due to decreased production of endogenous antimicrobial peptides. On the other hand, the exotoxins secreted by S. aureus are superantigens. Staphylococcal superantigens (SsAgs) may penetrate the skin barrier and contribute to the persistence and exacerbation of allergic skin inflammation in AD through the stimulation of massive T cells, the role of allergens, direct stimulation of antigen-presenting cells and keratinocytes, the expansion of skin-homing cutaneous lymphocyte-associated antigen-positive T cells, and the augmentation of allergen-induced skin inflammation. SsAgs also induce corticosteroid resistance. In therapeutic interventions, anti-inflammatory therapy alone is very effective in reducing S. aureus colonization on the skin, but antibiotic treatment alone is unable to improve the allergic skin inflammation of AD. Therefore, we recommend the combination therapy of anti-inflammatory drugs and antibiotics in the AD patients with secondary bacterial infection, exacerbated AD, or poorly controlled AD. However, when AD is well controlled by anti-inflammatory drugs alone, we do not recommend the antibiotic therapy.

Secondary infections in patients with atopic dermatitis

Clinicians have long since been aware that bacteria and other microorganisms play a role in the etiology of atopic dermatitis. Indeed, the immunological profile of atopy favors colonization by Staphylococcus aureus, and the bacteria are present in most patients with atopic dermatitis, even in the absence of skin lesions. Clinical signs of impetiginization, such as weeping and crusting, periauricular fissuration, or small superficial pustules are a sensitive indicator that the numbers of S. aureus may have increased and a clinical indication of secondary infected dermatitis. However, recent research that has focussed on the role of S. aureus in atopic dermatitis, offers a reversed perspective, by presenting evidence that the underlying pathology of atopic dermatitis, i.e. an alteration of the skin barrier and inflammation of the upper dermis, depends itself on the presence of an infectious process. In other words, secondary infection with S. aureus emerges as a cause of atopic dermatitis. Secondary infections due to fungi have, comparatively, received less attention, but there is evidence for a role for Malassezia spp. as a factor in dermatitis with a head and neck distribution pattern. Viral infections, such as herpes simplex virus, and mixed infections of intertriginous spaces, may complicate an underlying atopic dermatitis, but are not perceived as etiologic factors. Recent research has greatly contributed to our understanding of the pathophysiological potential of S.aureus superantigens in atopic dermatitis, suggesting that antibiotic therapy might be an important element in the therapeutic management of atopic dermatitis. At present, however, the clinical evidence is scarce with regards to demonstrating a clear advantage of combined anti-inflammatory and antibiotic treatment, compared with anti-inflammatory treatment alone. If there is a consensus that the presence of clinically infected lesions in atopic dermatitis warrants a course of specific antibiotic topical therapy, the clinical benefit of antibiotic agents in apparently uninfected atopic dermatitis, as present in the majority of patients, remains an open question.Moreover, the impact of adjuvant skin care on the cutaneous microflora needs to be quantified in order to properly assess the role of specific antibiotic therapy in clinically uninfected atopic dermatitis. In the meantime, secondary infections in atopic dermatitis remain a secondary problem in clinical atopic dermatitis management, and specific anti-infective therapy remains a method of fine-tuning for optimizing individual atopic dermatitis treatment.

A risk assessment framework for the evaluation of skin infections and the potential impact of antibacterial soap washing

Antibacterial soaps may have an important role in the control of skin infection. However, quantitative estimation of their benefit is difficult because of the problems associated with conducting epidemiologic studies. An alternative benefit estimation approach, quantitative microbial risk assessment, has application to this problem. This article sets forth the quantitative microbial risk assessment method and applies it specifically to the estimation of the reduction in risk of dermal infection from Staphylococcus aureus resulting from use of antibacterial soaps. A dose-response model was formulated by using available information on growth kinetics of the organism on the skin and dose data based on the inoculation of the forearm skin in volunteers. A predictive relationship for microbial growth on the skin was developed. These data were limited, and clearly more studies are needed on inoculation at more than one site and growth leading to infection on the skin with and without the use of germicidal soaps.However, by using relationships based on extant data sets, it was estimated that the use of germicidal soap could result in a substantial reduction in the risk of infection by S aureus. The estimated risk reduction was in general concordance with published results from epidemiologic studies conducted on military cadets. The methodology of quantitative microbial risk assessment has thus been shown to be applicable to this problem and may have broader applicability in other personal hygiene contexts.

Staphylococcus aureus isolation from the lesions, the hands, and anterior nares of patients with atopic dermatitis

Staphylococcus aureus colonization is common in atopic dermatitis (AD) and can exacerbate the disease. Some patients with atopic dermatitis may act as a reservoir for S. aureus transmission to others. This study compared S. aureus colonization in atopic dermatitis patients and their caregivers with control patients and their caregivers. Quantitative cultures were obtained from the lesions, clinically normal skin, hands, and anterior nares of 100 patients with atopic dermatitis, 100 controls with other cutaneous disorders, and 200 caregivers. The AD patients had significantly greater presence of S. aureus from lesional and clinically normal skin, as well as the hand. Significantly increased carriage of S. aureus was found in the anterior nares of caretakers of AD patients compared with control caretakers. Topical corticosteroid use did not affect recovery of S. aureus. There was a significant correlation between recovery of S. aureus from lesional skin and recovery from the anterior nares and hands. The nares and hands may be important reservoirs and vectors for autotransmission of S. aureus to lesional skin and for transmission to patients with AD.

Staphylococcus aureus in the anterior nares and subungual spaces of the hands in atopic dermatitis

We examined the prevalence of Staphylococcus aureus in the anterior nares and the subungual spaces of the hands of patients with atopic dermatitis to determine whether the presence of S. aureus at these sites may contribute to the aggravation of the dermatitic skin lesions. The prevalence of S. aureus in the anterior nares of patients with atopic dermatitis was over five times higher than that in the anterior nares of patients with other skin diseases or in healthy adult controls, and the prevalence of S. aureus in the subungual spaces was 10 times higher in patients with atopic dermatitis than in those with other skin diseases or in controls. Both the anterior nares and the subungual spaces of the hands are important reservoirs of S. aureus in atopic dermatitis. The phage type of S. aureus strains isolated from the anterior nares is similar to that of the strains isolated from the subungual spaces.

Atopic dermatitis. Current concepts support old therapies and spur new ones

With diligent care, most patients with atopic dermatitis markedly improve within a very short period. Avoidance of exacerbating factors and use of a mild topical corticosteroid preparation generally bring relief in all but the most extreme cases. Most of the newer, more intrusive therapies remain too expensive, too toxic, or too burdensome to warrant general support. Resistant cases often relate more to failure to pay appropriate attention to simple details (eg, avoidance of excessive contact with water and irritants) than to lack of sufficient potency in the medications chosen. Practitioners serve their patients best by taking adequate time to educate them and their families on the fundamental aspects of the disease, the importance of using common sense in caring for themselves and thus avoiding problems, and the need to relinquish the hope for a miracle cure, since none exists.