Normal Flora Dr Mohsina Haq The term flora

Normal Flora Dr. Mohsina Haq

• The term flora is used for collective bacteria and other microorganisms in an ecosystem such as the human host

• Also called as – Human microbiome – Human microbiota • It includes: – Bacteria – Fungi • It is acquired rapidly and shortly after birth and changes continuously through out our lives

Types of Microbiota • Indigenous microbiota – Establishes a permanent relationship with various parts of the body • Transient microbiota – More temporary and found only for limited periods

Present on • • • Skin External eyes and ears Upper respiratory tract Gastro intestinal tract Urogenital orifices (males and females)

Areas that are sterile • • Blood Cerebrospinal fluid Join fluids Internal organs • Sterile: devoid of living organisms, viruses and spores

• Mutualism • Mutualistic relationships provide reciprocal benefits for the two organisms involved • Commensalism • In commensalism, one species of organism lives harmlessly in or on the body of a larger specie • Parasitism • The symbiotic relationship benefits only the parasite • Symbiosis • Close and long term biological interaction between different biological organisms

Factors influencing Normal Flora • Local environment • p. H, temperature, nutrient level • Diet • Age • Young age, old age • Immune status • Immunocompetent, immunocompromised • Antibiotics

Humans as Habitats

Flora of Skin • Predominant organism • Staphylococcus epidermidis (non pathogenic on skin) • Location • Superficial layer(stratum corneum), hair follicles • It initiates a disease process when they are disseminated to other sites • Artificial heart valves • Prosthetic joints

• Yeast: Candida Albicans • non pathogenic in skin • If it enters blood streams it leads to infection • Can cause systemic infection

Other microorganisms present on skin • Staphylococcus epidermidis • Staphylococcus aureus • Alpha-hemolytic and non hemolytic streptococcus • Micrococcus species • Peptostreptococcus species • Diphtheroids • Acinetobacter species

Normal Flora of Respiratory Tract • Normally colonizes – Nose – Throat – mouth • Very rarely found in – bronchi – alveoli

• Nose: – Mostly aerobic bacteria • • Staphylococcus species (aureus) Streptococci (pmeumoniae, pyogenes) Diphtheroids (corynebacterium) Neisseria meningitidis

Normal Flora of Mouth • Mouth is also a site that are heavily colonized by bacteria • Teeth and gingiva carry a large number of anaerobic bacteria • Streptococcus mutans if present in plaque and leads to dental decay (carries) • Acid ferments to carbohydrates that attack enamel • Plaque is a film of bacterial cells anchored in the polysaccharide matrix that the organism secrets

Normal flora of oral cavity

Normal Flora of Respiratory System Flora of Pharynx and Trachea – They carry there own flora that includes α and β hemolytic streptococci – staphylococcus aureus, Neisseria and diphtheroids are also present – Some healthy individuals may carry Pneumocystis jirovecii (fungus) in there lungs

Normal flora of Gastrointestinal Tract • Harbors only transient organisms • p. H of the stomach provides an acidic environment • Some organisms that are acid-tolerant colonizes the mucosa • E. g. lactobacillus and streptococci • Commonest is H. pylori

• Ileum is lightly colonized, but population increases markedly in ileum • Streptococci, lactobacilli, Enterobacteriaceae and bacteroides , E. coli • Harmless protozoan (entamoeba coli) • Densely colonized is the large bowel

Frequency of occurrence and densities of the bacteria making up the GIT flora

Flora of the Urogenital Tract • Urethra is colonized lightly in both genders • Staph. epidermidis, strep. faecalis and diphtheroids • other organisims that are present • Lactobacillus aerophilus • Candida (fungal) causes thrush • Trichomonas vaginalis

Advantages and Disadvantages of Normal Flora • Skin bacteria • prevents invasion by producing fatty acids • Gut bacteria • • • Antibacterial activity (bacteriocins, colins) Helps in metabolism Helps in digestion Produces vitamin B and K Antigenic stimulation improves immune system • Urogenital flora • Lactobacillius maintains an acidic environment that discourages the growth of other bacteria

Disadvantages • The disadvantages of normal flora lie in the potential for spread into previously sterile parts of the body. This happens when • • Intestine is perforated Extraction of teeth Organism ascends into the urethra from perianal skin Unsterile environment during venipuncture • Over growth of bacteria occurs when • Local environment changes the p. H • Immune system becomes ineffective