BIOL20342 Microbiology : Oral and Nasopharyngeal Flora Develops

Introduction

Microorganisms are found everywhere such as in the air, water, soil, plants and animals. Without microbes the life on the earth will become unbalanced, because the microbes play an important role in supporting the cycles of the earth. All of the human beings contains microorganism in their body, which are known as the normal flora of the body. The internal tissues, e.g. blood, brain, muscle, etc in a healthy human being are free from the microorganisms. But the surface tissues such as skin, mucous membrane and many more are in contact with the organisms present in the environment. The normal flora of a human being consists of a few fungi and protists but mainly contains a numerous bacteria. A foetus in a mother’s womb is free from microorganism but as soon as it takes birth and comes into the contact with the vaginal flora. After a few hours of birth the oral and nasopharyngeal flora develops. Then in a day or two the intestinal flora appears. This report will describe about the normal flora of human body and the infections caused by them (Murray et al. 2015)

Normal flora of human body

There are mainly two types of flora:

• The resident flora - It consist of moderately fixed sorts of microorganisms frequently found in a given zone at a given age; if irritated, it quickly restores itself.
• The transient flora - It consist of both pathogenic and non-pathogenic microorganisms which inhabits the skin or the mucous membranes for days and even weeks. It comes from the environment which doesn’t produce disease and don’t stay permanently on the skin.

Individuals from the transient vegetation are for the most part of little centrality inasmuch as the ordinary inhabitant verdure stays in place. In any case, if the inhabitant greenery is bothered, transient microorganisms may colonize, multiply, and create infection (Tille 2013).

The human body contains a broad arrangement of microorganisms, most of them performing endeavors that are useful or even fundamental to human survival. Those that are depended upon to be accessible, and under conventional conditions don't cause disease, are named 'normal flora'. It is assessed that 5,000 to 10,000 particular sorts of life forms live in the human body. Microbial cells are essentially humbler than human cells, and there are around 1000 trillion (1015) microorganisms, ten times the quantity of as human cells in the body (1014). Notwithstanding the way that run of the mill vegetation are found on all surfaces introduced to the earth most by a long shot of microorganisms live in the internal organ (Lieberman 2014).

Ordinary microorganisms effortlessly colonize at various anatomical regions of the body and grow in these regions unknowingly of the host. The examination of normal flora in human body helps in understanding the parts of colonization, commensalism, advantageous impacts and causation of ailment in specific conditions. The ordinary microorganisms observed to be related with various parts of human body are depicted here (Nash 2015).

Eyes 

Eyes are presented to outer condition, henceforth they interact with a few organisms. The conjunctival vegetation is ordinarily scanty most likely in view of lysozyme, discharged in tears. Lysozyme is known to hinder development of microscopic organisms. It has been watched that specific microorganisms, for example, Staphylococcus epidermidis and some more (as given in table 1), might be available on conjunctiva. In ordinary circumstances, these creatures don't make any damage eyes. Nonetheless, in specific conditions, for example, damage to the eyes, these life forms may cause crafty contaminations (Mahon et al. 2014).

Table 1: Normal microflora of eyes

• Coagulase negative Staphylococci
• Haemophilus spp.
• Staphylococcus aureus
• Streptococci (distinctive species)
• Corynebacterium spp.
• Neisseria spp.
• Moraxella spp.

Ear

Ear is additionally presented to the outer condition. Henceforth, there is typical small scale verdure show in the ear as well (Table 2). In extra, typical small scale vegetation show on the skin has been found in ear too. Microorganisms, for example, Pseudomonas may come about into pioneering contaminations in the ear (Klatt et al. 2013).

Table 2: Normal microflora of ear

• Coagulase negative Staphylococci
• Diphtheroids
• Pseudomonas spp.
• Occasionally enterobacteria

Nasopharynx 

The nasopharynx and trachea contain basically those bacterial genera found in the common oral cavity (for example, alpha-and ß-hemolytic streptococci), regardless, staphylococci, neisseriae, diphtheroids, and others are moreover present (Table 3). Possibly pathogenic living things, for instance, Haemophilus, mycoplasmas, and pneumococci may similarly be found in the pharynx. The upper respiratory tract is so much of the time the site of starting colonization by pathogens, for instance, Neisseriae meningitides, C. diphtheriae, Bordetella pertussis and could be seen as the fundamental locale of ambush for such living things. Strangely, the lower respiratory tract (little bronchi and alveoli) is typically sterile, in light of the way that particles of size of tiny life forms don't quickly reach there. In the event that microscopic organisms do achieve these locales, they experience have safeguard systems, for example, alveolar macrophages, that are absent in the pharynx (Khanna and Tosh 2014).

Table 3: Normal microflora of nose and Nasophyrynx

• Coagulase negative Staphylococci
• Viridans Streptococci
• Staphylococcus aureus
• Haemophillus spp.
• Streptococcus pneumoniae
• Neisseria spp.

Skin 

The sweat-soaked and sebaceous emissions of pre-adulthood make the skin exceptionally helpless to colonization by organisms. As per a gauge, whole skin (roughly 2 square meters) of a grown-up human body can bolster around 1010 microorganisms commensally. The life forms typically found are recorded in Table 4. The skin is an extremely solid mechanical boundary to microbial attack and just a couple of small scale life forms can enter the skin in light of the fact that the external layer is constituted of thick and firmly packed cells known as keratinocytes (Lloyd-Price et al.2016).

Table 4: List of usually discovered ordinary microorganisms on human skin

• Streptococcus (different species)
• Candida spp.
• Staphylococcus aureus
• Coagulase negative Staphylococci
• Bacillus spp
• Mycobacterium spp.
• Malassezia furfur
• Diphtheroids
• Propionibacterium acenes

Nails 

The microflora of the common nails is similar to that of the skin. Clean particles and different unnecessary materials may attach under the nail, dependent upon what the nail contacts. Despite the skin type, these invisible particles may pass on microorganism and bacteria. Aspergillus, Penicillium, Cladosporium, and Mucor are the genuine sorts of developments found under the nails (Parham 2014).

Gastrointestinal tract 

Huge numbers of the microbes in the stomach related tract, altogether alluded to as 'gut verdure', can separate certain supplements, for example, complex starches that people generally cannot process. The lion's shares of these commensal microscopic organisms are anaerobes, which means they make due in a situation with no oxygen. A large number of the microorganisms of the typical verdure can go about as entrepreneurial pathogens on occasion of brought down resistance (Blaser 2014).

Typical microbial vegetation of various organs of gastrointestinal tract is depicted here.

Oral cavity

The normal flora which are not effectively removed are connected to teeth and gums in the oral cavity. With the nearness of a youngster's first teeth come new open entryways for microbial colonization. The microscopic organisms that are removed from the mouth to stomach are devastated by hydrochloric acid (Sender et al. 2016). Different microorganisms found in oral hole are diphtheroids, Eikenella corrodense, S. aureus, beta-haemolytic streptococci, Haemophilus spp, Candida spp. also, Viridans Streptococci (Table 5).

Table 5: Normal microflora of oral depression

• Staphylococci
• Viridans Streptococci
• Staphylococcus aureus
• Haemophilus spp.
• Streptococcus pneumoniae
• Neisseria spp.
• Candida spp.

Stomach 

The stomach is a generally antagonistic condition for microscopic organisms due to its sharpness. Stomach however contains microorganisms gulped with the nourishment and those unstuck from the mouth. Stomach has high acidic pH (between2-3). Causticity brings down the bacterial number, which is most noteworthy (roughly 103 to 106 creatures/g of substance) after dinners and least (much of the time imperceptible) after assimilation (Kohler et al. 2015). The typical microscopic organisms in stomach are of Streptococcus spp, Staphylococcus spp and Lactobacillus (Table 6).

Table 6: Normal microflora of stomach

• Streptococci spp.
• Staphylococcus spp.
• Lactobacillus spp.
• Peptostreptococcus spp.
• Helicobacter pylori

Small digestive system 

It can be isolated into three sections duodenum, jejunum and ileum. The initial 25 cm zone of small digestive tract is duodenum.

Not every microscopic organism that is available in this region has strength to resist the impact of the acidic juices of stomach and inhibitory impact of bile and pancreatic emissions. Most regular microorganisms are Gram positive cocci and bars, for example, Enterobacter faecalis, diphtheroids, Lactobacilli that are available in the jejunum (center piece of the small digestive system). Among yeast, Candida albicans is once in a while found in this piece of digestive tract (Belkaid and Segre 2014). The 7 distal piece of digestive tract is ileum in which pH begins rising and is more towards soluble. Because of ascend in pH, anaerobic Gram negative microscopic organisms and numerous individuals from the family Enterobacteriacae begin colonizing this territory of digestive tract. In this manner the normal microbes living in small digestive system have a place with Enterococci, Enterobacteria, Mycobacterium spp, Clostridium spp., Bacteriodes and Lactobacillus spp. (Table 7).

Table 7: Normal microflora of small digestive system

• Individuals from Enterobacteriaceae
• Lactobacillus spp.
• Enterococci
• Bacteroides spp.
• Mycobacterium spp.
• Clostridium spp.

Internal organ 

It is otherwise called colon. It underpins differing qualities of microorganisms. Thus internal organ has high tallies of creatures (10 12 life forms/gm wet weight of stool). The digestive organ goes about as a vast fermentor of microorganisms comprising of Gram negative microscopic organisms and anaerobes. What's more, Gram positive spore framing and non spore shaping poles are additionally present in the colon (Table 8). Among the individuals from the family Enterobacteriacae, E. coli (Zhou et al.2014).

Table 8: Normal microflora of internal organ

• Lactobacillus spp.
• Enterococci
• Bacteroides spp.
• Mycobacterium spp.
• Staphylococcus aureus

Urogenital microflora 

An assortment of organisms is regularly present in urogenital framework (Table 9). The front urethra of people contains S. epidermidis, enterococci, and diphtheroids. E coli, Proteus, and Neisseria (nonpathogenic species) are accounted for every so often. In light of the ordinary greenery dwelling in the urethra, mind must be taken in clinically deciphering pee societies; pee tests may contain these creatures at a level of 104/ml (Nardone and Compare 2015).

The sort of bacterial flora found in the vagina relies on upon the age, pH, and hormonal levels of the host. Lactobacillus spp. prevail in female babies (vaginal pH, roughly 5) amid the principal month of life. At pubescence, glycogen emission continues, the pH drops, and ladies gain grown-up greenery in which L. acidophilus, corynebacteria, peptostreptococci, staphylococci, streptococci, and Bacteroides prevail. After menopause, pH again rises, less glycogen is discharged, and the verdure comes back to that found in prepubescent females. Yeasts (Torulopsis and Candida) are every so often found in the vagina (10 to 30 percent of ladies); these occasionally increment and cause vaginitis (Wang and Yang 2013).

Table 9: Urogenital microflora

• Coagulase negative Staphylococci
• Mycobacterium spp.
• Bacteroides spp.
• Peptostreptococcus spp.
• Streptococcus (different species)
• Lactobacillus spp.
• Peptostreptococcus spp.
• Candida spp.

Infections caused by normal flora

The types of infections caused by the microbes present in our body are:-

Nosocomial infections

The word Nosocomial alludes to the Greek word for healing facility. Nosocomial contamination is that kind of diseases for the most part struck the patients in healing facilities amid their stay in doctor's facility.

As indicated by a gauge 5-15 % of all clinic patients secure some kind of Nosocomial contamination and around 20, 000 individuals pass on of nosocomial diseases every year. Nosocomial diseases may likewise be gained by specialists, medical caretakers or guests. Since healing facilities get patients experiencing diverse infections caused by microbial pathogenic operators, the doctor's facility condition is sullied with an assortment of pathogenic living beings. Subsequently, there are chances that healing center staff and patients may get contaminated with life forms. The nosocomial contaminations are administered by various components incorporating microorganisms in the healing facility condition, immuno-traded off status of the host and the chain of transmission in the clinic (Sommer and Bäckhed 2013).

Table 10: Commonly occurring nosocomial infections

Opportunities infections

The microbial flora typically present in various anatomical areas of the body is ordinarily safe and commonly shields body from attacking pathogens. However in specific situations these inhabitant microbial specialists may create illnesses in the host. Such specialists are known as astute pathogens and diseases caused by these microorganisms are called 'artful contaminations'. These incorporate contamination with viral operators, for example, human immunodeficiency infection (HIV), unhealthiness of host, liquor addiction, tumor, diabetes, leukemia, surgical wounds and invulnerable concealment prompted by sedate treatment, hereditary illnesses and so forth (Alonso and Guarner 2013).

AIDS patients have regularly been discovered related with artful contamination, for example, Pneumocystis carinii. Also other viral ailment might be trailed by contamination with astute life forms. Some infections, for example, echoviruses and adenovirus are typically present in people. Be that as it may, in traded off host, these infections may cause artful diseases. So also, Neisseria menegitidis (ordinary inhabitant of respiratory tract) and Streptococcus pneumoniae (typical occupant of nose and throat) may likewise cause pioneering contaminations prompting genuine illnesses in specific conditions (Wade 2013).

Candida albicans is available as should be expected micro-flora of oral cavity, skin and vagina in the wellbeing people. Be that as it may, when the host is immuno-bargained because of an assortment of reasons, a similar Candida can cause 'oral thrush', disease of nails and 'vaginal thrush' which are pioneering contaminations (Olsen 2016).

Method of transmission of infections 

The infection or contaminated diseases might be transmitted starting with one individual then onto the next by coordinate contact or the sickness causing operator may spread starting with one place then onto the next by an assortment of ways. The pathogen might be transmitted by individual to individual contact, water, nourishment, air, creepy crawly vector, blood and blood items transfusion, from mother to hatchling, and so on. Diverse methods of transmission of sicknesses are quickly depicted with appropriate illustrations (Dewhirst et al. 2012).

Person to Person contact 

Various bacterial, viral and parasitic sicknesses have been recognized that are effectively transmitted from individual to individual by contact. Little pox (caused by human pox infection) and tuberculosis (caused by Mycobacterium tuberculosis) are two great cases of transmission of ailments by coordinate contact with the contaminated individual. At the point when the host and source or supply of pathogens interacted with each other the exchange of disease happens in the powerless host (Tannock 2015).

Air-borne transmission

An extensive number of viral and bacterial pathogens which cause respiratory sicknesses while hacking, wheezing and talking. The pathogens are accessible recognizable all around as meager "vaporizers" called 'bead cores'. These pressurized canned items can wander out couple of meters to numerous kilometers through the air back and forth movement and reach to powerless host and cause pollution/sickness. These 'bead cores' are huge wellspring of airborne maladies in individuals and furthermore animals (Grice and Segre 2011).

Water-borne transmission 

An assortment of human and creature irresistible operators are transmitted through water especially in creating nations where across the board chlorination offices are not accessible. The drinking water is regularly debased with fecal substance of creatures, winged animals and a few times people. It is currently outstanding that numerous pathogens are available in dung of winged creatures and creatures which may taint the drinking water. At the point when the general population expends such tainted water, they get tainted. Giardiasis, amoebiasis, cholera, salmonellosis, hepatitis E and viral gastroenteritis are a portion of the regular illnesses transmitted through water (Murray et al. 2014).

Host - parasite relationship 

When an organism either damages or lives on the dependence of host, the life form is called "parasite" and this relationship is alluded to as parasitism. An assortment of parasitic specialists including microscopic organisms, infections, protozoa, helminths, and so on has been recognized. In the event that the living being lives on the surface of the host, it is called "ectoparasite" where as though it lives inside it is alluded to as 'endoparasite'. If this relationship is disturbed it causes harmful effects to the host. It has been seen that lactobacillus which is present in the genital tract and maintain low pH, when it is disturbed it causes vaginal infections caused by bacteria Gardenerella or Candida albicans (Nami et al. 2015).

Virulence factors

The term harmfulness alludes to the level of pathogenicity of a pathogen. It can likewise be characterized as the relative capacity of a creature to cause ailment. The word harmfulness has been gotten from the Latin word, virulentus, which implies brimming with harm'. A wide assortment of components created by pathogenic creatures including growths, parasites, microorganisms and infections has been related with harmfulness. The destructiveness components of pathogenic creatures are for the most part proteins or other atoms that are blended by proteins. These proteins are encoded by qualities introduce in pathogenic life form's chromosomal DNA or viral nucleic acids or plasmids. The pathogens cause sicknesses by a wide assortment of instruments including bond, colonization, intrusion, invulnerable reaction restraint, poisons, and so forth (Stru?ycka, 2014).

Adhesins

It has been discovered that specific microorganisms tie to the host cell surface in the wake of accessing the host. The atoms/structures of the living beings which help in authoritative with corresponding have cell receptors are alluded to as 'adhesins'. The adherence of specific pathogens has been observed to be fundamental for pathogenesis. This can be shown by the case of Streptococcus mutans, a gram positive bacterium related with tooth decay. It connects to the surface of teeth by glycocalyx glucosyl transferase, a catalyst delivered by S. mutans, changes over glucose into sticky polysaccharide called "dextran" which shapes glycocalyx. Actinomyces have fimbriae which append to glycocalyx of S. mutans adding to the arrangement of plaques. Also entero-pathogenic microbes, for example, E. coli and Shigella likewise have adhesins in their fimbrae to append to the host cells in the small digestive system (Zarco, Vess and Ginsburg 2012).

Glycocalyx

The meaning of glycocalyx is 'sugar coat'. It is made out of either polysaccharide alone or in blend with polypeptides. A sticky and thick polymeric material present on the outside surface of bacterial cell divider is known as 'glycocalyx'. Arrangement of glycocalyx varies in various types of microorganisms. Glycocalyx is discharged by bacterial cell. On the off chance that the glycocalyx is appended on the bacterial cell surface, it is known as 'container' (He et al. 2015).

Capsule 

Capsule is formed by glycocalyx around the bacterial cell. In certain bacterial pathogens, it is related with upgraded destructiveness. The nearness of container on microscopic organisms has been connected to diminished phagocytosis in contaminated host. Concoction piece of case averts connection of phagocytes to bacterial cells. Streptococcus pneumoniae (causative operator of pneumococcal pneumonia) is great case of harmfulness because of container.

Fimbreae

A type of Gram negative microbes has hair like structures on their surface. These are called "fimbria" (particular). The quantity of fimbriae show in each bacterial cell surface is distinctive. The number may fluctuate from a couple to hundreds/cell. This assistance in connection of microscopic organisms in has cells.

Haemolysin

These are created by some pathogenic microbes. Haemolysins are proteins and are prepared to do lysing red platelets (RBCs). Some bacterial species which deliver haemolysins are Clostridium perfringence (causes gas gangrene) and a few types of Streptococcus. Haemolysin goes about as destructiveness figure pathogenesis of haemolysin delivering pathogenic living beings (Weinstein and Swartz 2014).

Toxins

Toxins are toxic substance created by some pathogenic microorganisms. These are regularly fundamental destructiveness components adding to pathogenesis. Either toxins are delivered in have many diseases or created outside. The poisons delivered in human nourishment by debasing microorganisms may cause sustenance harming if polluted nourishments are devoured. Some of these can stay in "ruined" sustenance even in the wake of cooking and cause disease when the debased nourishment is devoured.

Contamination 

The attack on host done by a microorganism is followed by consequent foundation and duplication of the specialist. A contamination could conceivably prompt obvious ailment. Be that as it may, the tainted person may transmit the disease to different people. The disease might be either fleeting or it might hold on for long time. The disease might be transmitted by any mode as portrayed before (Maddi and Scannapieco 2013).

Invasion 

The demonstration of section and ensuing spread of pathogen in the host body tissues is known as invasion. The capacity of pathogenic life forms to enter have, increase/imitate and spread in the have body is called "obtrusiveness."

Pathogenicity 

Pathogenicity can be depicted as the condition or nature of being pathogenic or the capacity to cause illness. Pathogenicity can be characterized as the property of any pathogenic operator to cause illness. The seriousness of the sickness relies on upon the level of pathogenicity (Dewhirst et al. 2012).

Toxigenicity 

The limit of a living being to create poison, synthetic substances that will harm the host tissue and deliver infections.

Virulence 

The degree of pathogenicity of a life form is shown by the fatality rates of the cases and capacity to attack has tissue and cause sickness.

Carrier

An infected person who is a potential source of contamination for others assumes a vital part in the study of disease transmission of an infection. It has been watched that many individuals harbor pathogenic living beings and transmit them straightforwardly or in a roundabout way to other individuals. A few people may harbor the pathogens without showing signs or disease. These are called transporters. They are essential living repositories of disease. Human transporters assume essential parts in transmission of such sicknesses as hepatitis, diphtheria, typhoid, gonorrhea, AIDS, amoebic looseness of the bowels, and so forth (Coates Moran and Horsburgh 2014).

Types of carriers

Four distinct types of carriers have been distinguished.

(1) Active carrier - A person who has a plain case or indication of clinical infection.

(2) Convalescent carrier - A person who has recuperated from malady yet conveys extensive number of pathogenic life form.

(3) Healthy carrier - A person who conveys the pathogenic life form without showing obvious clinical signs and side effects.

(4) Incubatory carrier - A person who is hatching expansive number of a pathogenic creature however not appearing manifestations of sickness at this stage, however in the end builds up a honest clinical infection. The incubatory transporters can possibly transmit the pathogenic life forms to different people.

Conclusion

Thus it can be concluded that, If the normal flora escape from their typical area, they can cause malady. For instance, Escherichia coli, regularly found in the digestive tract, can cause urinary tract diseases if brought into the bladder. Typical greenery exists on and in the body. In any case, certain ordinary vegetation lives just in certain body zones. For instance, we have E-Coli microorganisms in the digestive organs, rectum, and on the skin around the rear end. In the event that that vegetation is "moved" to an alternate body region, say in the mouth (from not washing hands subsequent to wiping without end a defecation) or in the vagina (from wiping back to front), at that point contamination can happen.

A few illnesses make ordinary verdure duplicate. For instance, yeast is found on the skin, mouth, and in the vagina. Individuals with diabetes can have visit yeast contaminations in the mouth, vagina, and in skin folds.

Typical body vegetation is by and large supportive to the creature. Actually having typical body verdure involves space and assets that could somehow or another be used by pathogens. In any case, some typical body verdure can be destructive if the microorganism enters a zone of the body that it would not ordinarily be found and can cause disease. These microscopic organisms are known as sharp pathogens.

References 

Murray, P.R., Rosenthal, K.S. and Pfaller, M.A., 2015. Medical microbiology. Elsevier Health Sciences.

Tille, P. (2013). Bailey & Scott's Diagnostic Microbiology-E-Book. Elsevier Health Sciences.

Lieberman, D. (2014). The story of the human body: evolution, health, and disease. Vintage Books.

Nash, A.A., Dalziel, R.G. and Fitzgerald, J.R., 2015. Mims' pathogenesis of infectious disease. Academic Press.

Mahon, C. R., Lehman, D. C., & Manuselis, G. (2014). Textbook of Diagnostic Microbiology-E-Book. Elsevier Health Sciences.

Klatt, N.R., Funderburg, N.T. and Brenchley, J.M., 2013. Microbial translocation, immune activation, and HIV disease. Trends in microbiology, 21(1), pp.6-13.

Khanna, S. and Tosh, P.K., 2014, January. A clinician's primer on the role of the microbiome in human health and disease. In Mayo Clinic Proceedings (Vol. 89, No. 1, pp. 107-114). Elsevier.

Lloyd-Price, J., Abu-Ali, G. and Huttenhower, C., 2016. The healthy human microbiome. Genome medicine, 8(1), p.51.

Parham, P., 2014. The immune system. Garland Science.

Blaser, M.J., 2014. The microbiome revolution. The Journal of clinical investigation, 124(10), p.4162.

Sender, R., Fuchs, S. and Milo, R., 2016. Revised estimates for the number of human and bacteria cells in the body. PLoS biology, 14(8), p.e1002533.

Köhler, J.R., Casadevall, A. and Perfect, J., 2015. The spectrum of fungi that infects humans. Cold Spring Harbor perspectives in medicine, 5(1), p.a019273.

Belkaid, Y. and Segre, J.A., 2014. Dialogue between skin microbiota and immunity. Science, 346(6212), pp.954-959.

Zhou, Y., Holland, M.J., Makalo, P., Joof, H., h Roberts, C., Mabey, D.C., Bailey, R.L., Burton, M.J., Weinstock, G.M. and Burr, S.E., 2014. The conjunctival microbiome in health and trachomatous disease: a case control study. Genome medicine, 6(11), p.99.

Nardone, G. and Compare, D., 2015. The human gastric microbiota: Is it time to rethink the pathogenesis of stomach diseases?. United European gastroenterology journal, 3(3), pp.255-260.

Wang, Z.K. and Yang, Y.S., 2013. Upper gastrointestinal microbiota and digestive diseases. World journal of gastroenterology: WJG, 19(10), p.1541.

Sommer, F. and Bäckhed, F., 2013. The gut microbiota—masters of host development and physiology. Nature Reviews Microbiology, 11(4), pp.227-238.

Alonso, V.R. and Guarner, F., 2013. Linking the gut microbiota to human health. British Journal of Nutrition, 109(S2), pp.S21-S26.

Wade, W.G., 2013. The oral microbiome in health and disease. Pharmacological research, 69(1), pp.137-143.

Zarco, M.F., Vess, T.J. and Ginsburg, G.S., 2012. The oral microbiome in health and disease and the potential impact on personalized dental medicine. Oral diseases, 18(2), pp.109-120.

Olsen, I. (2016). The Oral Microbiome in Health and Disease. In Oral Infections and General Health (pp. 97-114). Springer International Publishing.

Dewhirst, F.E., Chen, T., Izard, J., Paster, B.J., Tanner, A.C., Yu, W.H., Lakshmanan, A. and Wade, W.G., 2010. The human oral microbiome. Journal of bacteriology, 192(19), pp.5002-5017.

Coates, R., Moran, J. and Horsburgh, M.J., 2014. Staphylococci: colonizers and pathogens of human skin. Future microbiology, 9(1), pp.75-91.

Tannock, G.W., 2015. Normal microflora: an introduction to microbes inhabiting the human body. Springer Science & Business Media.

Grice, E.A. and Segre, J.A., 2011. The skin microbiome. Nature Reviews Microbiology, 9(4), pp.244-253.

Weinstein, L.O.U.I.S. and Swartz, M.N., 2014. Pathogenic properties of invading micro-organisms (pp. 745-772). M]. In: WA Sodeman Jr. and WA Sodeman. Pathologic physiology: mechanisms of disease. Philadelphia: Saunders.

Miller, C.H. and Palenik, C.J., 2014. Infection Control and Management of Hazardous Materials for the Dental Team5: Infection Control and Management of Hazardous Materials for the Dental Team. Elsevier Health Sciences.

Murray, J.L., Connell, J.L., Stacy, A., Turner, K.H. and Whiteley, M., 2014. Mechanisms of synergy in polymicrobial infections. The Journal of Microbiology, 52(3), p.188.

Nami, Y., Haghshenas, B., Abdullah, N., Barzegari, A., Radiah, D., Rosli, R. and Khosroushahi, A.Y., 2015. Probiotics or antibiotics: future challenges in medicine. Journal of medical microbiology, 64(2), pp.137-146.

Stru?ycka, I.Z.A.B.E.L.A., 2014. The oral microbiome in dental caries. Pol J Microbiol, 63(2), pp.127-135.

He, J., Li, Y., Cao, Y., Xue, J. and Zhou, X., 2015. The oral microbiome diversity and its relation to human diseases. Folia microbiologica, 60(1), p.69.

Maddi, A. and Scannapieco, F.A., 2013. Oral biofilms, oral and periodontal infections, and systemic disease. Am J Dent, 26(5), pp.249-54.