Healthcare Hygiene magazine December 2019

from the skin; however, the researchers say further studies are needed to understand the ability of these bacteria to co-aggregate, their influence in interpersonal transmission and shaping of microbial ecology of the host skin. Why does this matter? Kumar, et al. (2019) explain that the presence of more number of co-aggregating bacteria in individuals may facilitate the inter-personal transfer among individuals who are having hand contacts very often: “These bacteria are recently known to acquire multi-drug resistance and can be transferred rapidly, surviving desiccation and persisting in the environment for a long time. Thus, these bacteria could pose significant concern among the interacting population, especially the vulnerable human population. Co-aggregation is common among Pseudomonas species; Doring, et al. demonstrated the transfer of P. aeruginosa and Burkholderia cepacia by handshaking of in- dividuals, where these bacteria were detect- Hand hygiene, when ed up to 30 minutes to 180 minutes. Nu- performed correcly, merous studies have results in hands that documented that the are more than clean enough to subungual area of prevent cross-transmission from the the hand harbor high concentration of bac- hands of that person.” teria, most frequently coagulase-negative — Didier Pittet, MD, MS, CBE Staphylococci, Pseu- domonas spp., Corynebacteria, and yeasts.” Edmonds-Wilson, et al. (2015) connects the dots for us in their review of human hand microbiome research when they observe, “Human hands are a conduit for exchanging microorganisms between the environment and the body. Hands can harbor pathogenic species, including methi- cillin-resistant Staphylococcus aureus or Escherichia coli; particularly within high risk environments, such as healthcare and food-handling settings. Product use can impact the hand microbiome, with greater pathogen hand carriage on people using a high level of hand hygiene products, while other studies have demonstrated reduced pathogen carriage and/or infections with use of these products. Frequently washed hands of healthcare workers are colonized with more pathogenic bacteria than those who wash less frequently. … Many studies have demonstrated the beneficial impact of handwashing and/or use of alcohol-based hand rubs for reducing pathogenic bacteria on hands and/or reducing infection rates in various institutional settings. The occurrence of pathogens on hands is well-studied; in contrast, hands are rarely considered a source of beneficial bacteria contributing to our healthy microbiome.” In their review, Edmonds-Wilson, et al. (2015) found that overall, the data on hands is limited compared to other body sites, and most studies were conducted on young adults, often students or professionals, in the United States. Most studies contained a small sample size (≤10) and/or assessed microbial composition at a single time-point. Most studies reported between eight and 24 families of bacteria on hands. One study found that bacteria were the most prevalent 18 microorganism (>80 percent relative abundance), then viruses, and fungi being least prevalent on hands. However, as Edmonds-Wilson, et al. (2015) caution, this finding “may be somewhat biased for greater proportion of bacteria, since the relative size of viral genomes is small, and would therefore be expected to represent proportionally less of the sequence data, even if bacteria and viruses were equally abundant.” The researchers also note that skin biogeography significantly impacts the composition of the microbiome: “Hands have greater bacterial diversity; and the hand microbiome is more dynamic over time than other skin sites. Palm skin typically harbors more than three times more bacterial phylotypes per individual compared to forearm or elbow skin. Fungal species diversity was intermediate on hands, with feet having greater diversity and core body skin sites having the least diversity. Microbial communities on hands were generally enriched with different bacterial taxa compared with other body sites and acquired a larger pool of total bacterial species through time. The interpersonal variation of the hand microbiome was less than the variation between different body sites on the same individual. Temporal stability of the microbiome is dependent on physiological conditions of the skin; with moist, warm, and nutritionally rich skin sites harboring a more stable microbiome than hands which are dry and continually exposed to varying environments. Additionally, individuals with more variable hand bacterial communities have greater variability at other skin sites, indicating microorganisms may be transferring between skin sites.” Of note for patient hand hygiene, Edmonds-Wilson, et al. (2015) found that immune function and other health factors likely impact the bacterial composition of hand skin: “A study found different bacterial composition on the hands of healthy controls compared with those of immune-compro- mised individuals; with healthy populations having greater proportions of Staphylococcus spp., Fusobacterium spp. and Prevotella spp., and the immune-compromised having a greater proportion of Acinetobacter spp.” Extrinsic factors impacting hand microbiome composition was challenging to discern, as no studies in this review by Edmonds-Wilson, et al. (2015) directly evaluated the impact of hand hygiene or other product use on the hand microbiome. However via self-reported survey data, the researchers attempted to correlate hand hygiene practices, including the type of products used and the frequency of use, to changes in the hand microbiome. They observe, “Healthcare workers likely have greater exposure to hand hygiene products than the rest of the population; however the overall microbial diversity on hands was unchanged with alcohol-based handrub use or handwashing, with the exception that overall diversity was lower in those that reported more than 40 handwashing with soap and water events per shift. The length of time since the last handwashing event impacted bacterial composition, with Propionibacteria, Neisseriales, Burkholderiales and Pasteurellaceae more abun- dant with time since handwashing, and Staphylococcaceae, Streptococcaceae, and Lactobacillaceae more abundant on recently (more than two hours) washed hands. While there were changes in bacterial composition with time since last december 2019 • www.healthcarehygienemagazine.com

Healthcare Hygiene magazine December 2019 | Page 18