Normal flora Normal flora 1 Definition Normal flora

Normal flora

Normal flora 1 Definition • Normal flora is the mixture of microorganisms (bacteria and fungi) that are regularly found at certain anatomical site of human body without causing disease. • Called Microbiota, Microflora, Microbial flora, Indigenous microbial population • There are more bacteria (1014) living in or on our bodies, than we have cells (1013) of our own.

Normal Flora 2

Normal Flora 3 • • Skin Eyes (i. e. Conjunctiva) Nose (i. e. Respiratory tract) Mouth (i. e. Human Oral Cavity) Ears Urogenital tract Elementry tract

Estimation of Normal flora • Estimated human normal flora; – 1012 bacteria on the skin, – 1010 in the mouth, and – 1014 in the GIT.

Normal Flora 3 • Resident flora – Acquired rapidly during & after birth – Changes continuously through out life Reflects a person’s - Environment (90% is S. epidermidis; S. aureus, may be in moist areas) -Culture -Sex -Age -Nutrition -Genetics -Use of antibiotics

Normal flora 4 Sterile tissues In a healthy human, the internal tissues such as: • Blood • Brain • Muscle • Cerebrospinal fluid (csf) are normally free of microorganisms.

Normal Flora of the Conjunctiva - Staphylococcus epidermidis - Corynebacterium sp. - Propoinibacterium acnes - Staphylococcus aureus - Viridans streptococci - Neisseria sp. - Haemophilus influenzae Pathogens of the conjunctiva • Neisseria gonorrhoeae • Chlamydia trachomatis

Normal flora of the skin 1 • The most important sites are: – Axilla – Groin – Areas between the toes • The majority of skin microorganisms are found in the most superficial layers of the epidermis and the upper parts of the hair follicles.

Normal flora of the skin 2 • Important bacteria: 1. Staphylococcus epidermidis 2. Micrococcus sp. 3. Corynebacteria sp. 4. Mycobacterium smegmatis

Normal Flora of the Respiratory Tract 1 Nostrils - Staphylococcus epidermidis - Corynebacteria - Staphylococcus aureus - Neisseria sp. - Haemophilus sp - Streptococcus pneumoniae

Normal Flora of the Respiratory Tract 2 The upper respiratory tract (nasopharynx). - Non-hemolytic streptococci - Alpha-hemolytic streptococci - Neisseria sp. - Streptococcus pneumoniae - Streptococcus pyogenes - Haemophilus influenzae - Neisseria meningitidis

Normal Flora of the Respiratory Tract 2 The lower respiratory tract (trachea, bronchi, and pulmonary tissues): • Usually sterile. • The individual may become susceptible to infection by pathogens descending from the nasopharynx e. g. – H. influenzae • S. pneumoniae).

Normal Flora of the Respiratory Tract 3 The lower respiratory tract (trachea, bronchi, and pulmonary tissues): • Usually sterile • The individual may become susceptible to infection by pathogens descending from the nasopharynx e. g. – H. influenzae – S. pneumoniae.

Normal Flora of the Human Oral Cavity 1 Oral bacteria include: Viridans streptococci Lactobacilli Staphylococci (S. aureus and S. epidermidis) - Corynebacterium sp. - Bacteroides sp. - Streptococcus sanguis (dental plaque) - Streptococcus mutans (dental plaque) - Actinomyces sp. • -

The Normal Flora of The External Ear • The external ears contains a variety of microorganisms. These include: - Staphylococcus epidermidis. - Staphylococcus aureus - Corynebacterium sp

Normal flora of the Urogenital Tract 1 The anterior urethra - Staphylococcus epidermidis - Enterococcus faecalis - Alpha-hemolytic streptococci. - Some enteric bacteria (e. g. E. coli, Proteus sp. ) - Corynebacteria sp. - Acinetobacter sp. - Mycoplasma sp. - Candida sp. - Mycobacterium smegmatis

Normal flora of the Urogenital Tract 2 The vagina - Corynebacterium sp. - Staphylococci - Nonpyogenic streptococci - Escherichia coli - Lactobacillus acidophilus - Flavobacterium sp. - Clostridium sp. - Viridans streptococci - Other Enterobacteria

Normal flora of the Human Gastrointestinal Tract 1 • At birth - The entire intestinal tract is sterile, but bacteria enter with the first feed. - The initial colonizing bacteria vary with the food source of the infant.

Normal flora of the Human Gastrointestinal Tract 2 • In breast-fed - Bifidobacteria account for more than 90% of the total intestinal bacteria. - Enterobacteriaceae - Enterococci - Bacteroides - Staphylococci - Lactobacilli - Clostridia

Normal flora of the Human Gastrointestinal Tract 3 • In bottle-fed infants - Bifidobacteria are not predominant. When breast-fed infants are switched to a diet of cow's milk or solid food, bifidobacteria are progressively joined by: - Enterics Bacteroides Enterococci Lactobacilli Clostridia

Normal flora of the Human Gastrointestinal Tract 2 • In the upper GIT of adult humans – mainly acid-tolerant lactobacilli e. g. Helicobacter pylori • The proximal small intestine – – Lactobacilli Enterococcus faecalis Coliforms Bacteroides

Normal flora of the Human Gastrointestinal Tract 2 The flora of the large intestine (Colon) - Enterococci - Clostridia - Lactobacilli - Bacteroides - Bifidobacterium (Bifidobacterium bifidum) - Escherichia coli - Methanogenic bacteria - Viridans streptococci - Staphylococcus sp. - Proteus sp. - Candida albicans (Yeast) - Mycoplama sp.

Normal flora (Advantages) • Protective host defense mechanism by occupying ecological niches. • Contribute to immunity by inducing low levels of circulating and secretory antibodies that may cross react with pathogens • Produce vitamin B and vitamin K in intestine. • Exert microbial antagonism against non-indigenous species by production of inhibitory fatty acids, peroxides, bacteriocin, etc.

Normal flora (Disadvantages) Cause disease/harm in: - Immunocompromised or debilitated individuals. - When they change their usual anatomic location. - Since some of these bacteria are pathogens or opportunistic pathogens Clinical conditions that may be caused by normal flora

Normal flora and Mood • Normal flora influence human physiology • Micro-organisms in our gut secrete a profound number of chemicals used by our neurons to communicate and regulate mood, like dopamine, serotonin and gamma-aminobutyric acid (GABA). • These, in turn, appear to play a function in intestinal disorders, which coincide with high levels of major depression and anxiety.

Opportunistic flora

Opportunistic flora 1 • Some normal flora become opportunistic pathogens • (Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, Streptococcus pneumoniae, Pseudomonas aeruginosa, etc. ) • Breach of skin/mucosal barrier: trauma, surgery, burns • Bacterium at one site may be commensal, but pathogenic at another site

• Other risks: Opportunistic flora 2 – Dental plaque – Dental caries: destruction of enamel, dentin or cementum of teeth – Periodontal disease – Inflammatory bowel disease – Obesity

Opportunistic flora 3 • Other risk factors include – Broad-spectrum antibiotic therapy decreases total number of bacterial in gut • During repopulation, fastergrowing aerobic Enterobacteriaceae over slower-replicating anaerobes increases probability of gram -negative bacteremia – Cross-reactive responses to host tissue: Superantigen – Chronic, low-grade inflammation • Perturbation of cytokine network

Probiotics/Prebiotics

Probiotics/Prebiotics • Probiotic – Oral administration of living organisms to promote health – Mechanism speculative: competition with other bacteria; stimulation of nonspecific immunity – Species specific: adherence and growth (tropism) – E. g. S. boulardii, lactobacillus acidophilus • Prebiotic – Non-digestible food that stimulates growth or activity of GI microbiota, especially bifidobacteria and lactobacillus bacteria (both of which are non-inflammatory) – Typically a carbohydrate: soluble fiber

Advantages of Probiotics

Disadvantages of Probiotics • Could cause – Infections in immunosuppressed individuals – Digestive issues such as gas and bloating which may be temporary, – Complication of certain ill health condition such as pancreatitis.

Gnotobiology 1 • Refers to – A microbiologically monitored environment or animal that is germfree (axenic) – animal in which the identities of all normal flora are known – Helps to investigate the interactions of animals and specific microorganism

Gnotobiology 2 Fetus is sterile • Cesarean sections to obtain fetus • Fetus growing in sterile isolator • Not anatomically or physiologically normal – Poorly developed lymphoid system, thin intestinal wall, enlarged cecum, low antibody titers – Die of intestinal atonia (motility problem) – Require vitamin K and B complexes • More susceptible to infection • Almost completely resistant to the intestinal protozoan Entamoeba histolytica (amebic dysentery) • No dental caries or plaque (except if inoculated with cariogenic streptococci of the Streptococcus mutans. Streptococcus gordonii)