In general, Cancer is not contagious. But there are certain types of cancers discovered in animals that can be transmitted from animal to animal. Transmissible cancers are rare in humans. Devil Facial tumour disease (Tasmanian devil), Canine Transmissible venereal tumour (dogs), Contagious Reticulum Cell Sarcoma (Syrian hamster) and Soft Shell Clams (Mya arenaria) are contagious cancers discovered so far. Recently, reserachers have found another type of contagious cancer in Tasmanian devil. For more information check:
Skin is the outermost covering of the human body. It is the largest organ with an estimated area of 20 square feet. It forms the first line of defense, protecting the body against pathogens, regulates the body temperature and enables the sensation of heat, touch and cold. It is divided into three layers: epidermis– upermost waterproof protective layer, followed by dermis-consists of connective tissues, hair follicles and sweat glands, followed by subcutaneous layer– lowermost layer composed of connective tissues. The pH and temperature of the skin depends on the area of the body it covers. In general, the pH ranges from 5.6 to 6.4 and temperature from 25 to 35 degree Celsius.
The microbes residing on the skin constitute the skin microbiota. In general, the microbes are found all over the body but dermatologists have classified the three anatomical sites on the skin for their microbiological differences.These regions are distinguised based on the pH, temperature , moisture and concentration of skin lipids. The regions are:
- The Dry site: Includes forearm, legs, hands and feet.Since the area is exposed to the outer environment, it has most diverse microbial population.
- The Moist site: Includes axilla, toe webs, groins and beneath the breast areas.
- The Oily site: Includes head, neck and face. This area has sebaceous glands that secret an oily susbstance called sebum.
The oily site is more species rich than the dry and moist sites.The microflora inhabiting the skin include both bacteria and fungi e.g.Staphylococcus, Proprionibacteria, Cornybacterium, Malasezzia, Dermabacter and Micrococcus.
The Bacterial Inhabitants
According to a research the human skin is a home to 113 phylotypes that belong to six bacterial divisions. Some of the common species found are described below.
- Staphylococcus epidermidis : It is a Gram-positive bacterium, non-motile and facultative anaerobe found around sebaceous glands and moist areas. In general , it is not pathogenic but in immunosuppresed individuals it causes infections. The infections acquired are mostly nosocomial. It forms biofilms on catheters and other surgical implants implanted within the body. The biofilms formed are resistant to antibiotic treatments, therefore, taking the infection to an advanced level. Vancomycin have been , so far, the prefeered antibiotic that effectively helps fighting the infection.
- Staphylococcus aureus: It is Gram-positive, immobile and facultative anerobe found around sebaceous glands and moist areas. It is pathogenic in nature and is the most common cause of staph infections. It is also the causative agent of mild skin infections, invasive diseases like bacteremia, wound infection, etc. and toxin-mediated diseases like food poisioning, scaled skin syndrome, etc. It also forms biofilms and is resistant to antibiotics. The emergence of its antibiotic resistant strain Methicillin resistant Staphylococcus aurues has now come in the hit-list for the researcher s and doctors as it is increasly victimising the people.
- Propionibacteria: It is a Gram positive bacteria. They share a commensal relationship with humans and inhabit on the skin, majorily concentrated around sebaceous glands. In general they are non-pathogenic but often cause infections when come in contact with blood or any other body fluid. P. acnes is reponsible for acne vulgaris and is also associated with anaerobic arthritis and in some cases with osteomylitis and endocarditis.Antibiotics such as penicillin, carbapenems and clindamycin are generally used for the treatment.
- Cornybacteria: It is Gram-positive aerobic bacteria found in moist area of the human skin.Generally, they are non-pathogenic but some species are known to be infective. C.diptheriae is the causative agent of dipetheria, a respiratory disease mainly affecting the children.Its other pathogenic species in humans are C.amicolatum, C.striatum, C.xerosis that mostly affect the immunosuppressed patients. The bacteria is also responsible for skin infections and endocarditis. C.striatum causes axillary odor while C.minutissimum cause erythrasma.
- Proteobacteria: It is a Gram-negative , facultative or obligatory anaerobic. They are concentrated in the dry areas of the skin. They are mostly pathogenic and includes species like Escheresia, Salmonella, Vibrio, Helicobacter and Yersenia.
The Fungal Inhabitants
According to a study around 14 genera of fungi have been found to colonise human skin. Majority of the species are concentrated around heels, toenails and beween the toes. Other areas include palm, forearm and elbows. Some of the common species are Candida albicans, Torulopsis, Trichopytom rubrum, Alternaria alternata, Fusarium, Rhizopus stolonifer, Penicillum etc. Some of the common fungal infections are:
- Athelete’s Foot: It is caused by a microscopic fungi Trichopytom rubrum that lives on dead skin, hair , toenails and outer skin layers. The disease may be interdigital, mocassin (entire sole of the foot and may extend to the sides of foot) and Vesicular (between toes, on the heel and top of the foot). It is treated with antifungal medication.
- Jock Itch: It is a skin infection caused by a fungus Tinea. Since the fungus resides in warm moist area, therefore, the infection majorily occurs in genital area, inner thigh regions and buttocks. It is treated with antifungal sprays and creams.
- Ringworm: It is a skin inection caused by fungus Tinea. It can occur anywhere on the body and is contagious. Treatment generally includes antifungal creams like Lmicil, Mycelex, etc.
- Yeast Infections: It is caused by yeast Candida albicans. Yeast infections are not contagious. They mostly occur in warm, moist, oily area, like armpits and groin.It is alo responsible for diaper rashes in infants and vaginal yeast infections. They are treated with anti-yeast medications.
As described above the skin is inhabited by both bacterial and fungal species, of which some are pathogenic. In defensive mode, the skin protects itself by secreting some antimicrobial peptides like cathelicidins that keep a check on the proliferation of skin microbes. These peptides reduce the microbes and also help release cytokines which induces inflammation, angiogenesis and reepitheliazation. The acidic pH of the skin due to lactic acid found in the sweat also helps to control on the microbe number.
Image source: MIT gallery
The Twenty First century has witnessed the so-called ‘Technology Revolution’ and that too at an enormous scale. The revolution still continues. From smart phones to smart computers to smart television sets we have now the Smart Band-Aid. The stretchy hydrogel band aid designed by the MIT engineers are the band-aids of the future.These tiny stretch can incorporate temperature sensors, LED lights, other electronics along with drug delivery channels. For more details click below.
We, Homo sapiens sapiens, are the superorganisms that consist of many other organisms. We share our body and its internal environment with millions of microbial species. A vast numnber of microbes have put down their roots in our body, collectively referred to as human microbiota. As per the estimates of National Institute of Health 90% of the cells in a human body are bacterial, fungal or otherwise non-human. The microbes outnumber the human cells with a ratio of ten to one.
The microbiome, the genetic material of all the microbes that reside on or inside the human body, forms an indispensable part our genetic landscape-referred to as human metagenome. According to researchers the number of genes in microbiome is 200 times the number of genes in human genome. The microbial population mainly include species of bacteria, fungi, viruses and protozoa. It is estimated that atleast 205 different genera of microbes are found in human body.The population majorily inhabit on the surface and in the deeper layers of dermis, oral mucosa, saliva,conjunctiva, the gut region, forearms, nostrils, ears and inguinal parts.
An individual inherits his/her microbiome from mother; when a child makes it way from microbial free womb through microbe rich vaginal area.There is a considerable difference of microbial array in newborns depending on their type of delivery. Those delivered normally have more diverse population of bacterial species as compared to those who are delivered through C-section, the latter having picked up some Staphylococcus species from the hospital environment. The microbiome is dynamic in nature with environmental exposures and diet being the most prominent determinents in shaping the microbial ecology.
With millions and trillions of microbes populating the human body only a fraction of the community has been characterised and identified. These species have been known to have both benefecial and harmful effects on their host. The National Institute of Health’s initiative-THE HUMAN MICROBIOME project aims to generate research resources for extensive annotation of the microbial populace and analysis of their role in human health and disease.
It is hoped that the preface have given the readers an overview of the subject matter, the details of which would be covered in subsequent parts of the series.
Happy reading, Witty thinking!!