LECTURE NOTES FOR INTRODUCTION TO NORMAL FLORA.pptx

There is high prevalence rate of hospital acquired infection worldwide and Uganda. Therefore this SlideShare will acquaint them with adequate knowledge

1. NORMAL FLORA VS OPPORTUNISTIC PATHOGEN BY ABURA GEOFFREY

2. NORMAL FLORA/COMMENSAL/MICROFLORA These are organisms that inhabit the body of a healthy person without causing disease under normal circumstances. Most normal flora are either bacteria or Fungi (yeasts). EXCEPT Viruses, helminths and protozoa Normal flora (commensals) may cause infection (opportunistic infection) when the immune system of the host is compromised.

3. ORIGIN OF NORMAL FLORA A foetus , is sterile when born, then newborn start having the normal flora when passing through mother’s vaginal tract and then to environment (air, food etc ) Within few hours, oral and nasopharyngeal flora of neonate established Within one day, resident flora of lower intestinal tract established Our internal organs are sterile like the spleen, liver, pancreas, bladder, CSF, and blood unless during infection Normal flora differ from one human to another depending on age, diet, and geographical habitat.

4. CLASSIFICATION/Types OF NORMAL FLORA Normal flora may be grouped into two: - Resident flora – These are microorganisms commonly found in a particular area of the body at a given age . When the number of resident flora is greatly reduced, opportunistic microbes can easily cause infection in these areas eg . Candida albicans that cause candidiasis. If distributed, it re-established itself. Transient flora – Transient flora are organisms that are present at a given time and disappear or die off in hours, days, weeks or months . These are either pathogenic or non-pathogenic. It inhabits the skin or mucus membrane for hours or days or weeks. It varies from time to time/environment. Doesn’t re-establishes by itself.

5. DISTRIBUTION OF NORMAL FLORA IN THE BODY We all should know about the types and distribution of normal flora in our bodies because: It gives us better understanding of the possible infections that result from injury to a specific body site As well as possible sources and significance of microorganisms isolated from the site of an infection.

6. Con’t Normal flora of the skin Normal flora of the eye or conjunctiva Normal flora of digestive tract Normal flora of respiratory tract Normal flora of urinary tract Normal flora of genital tract

7. DISTRIBUTION OF NORMAL FLORA IN THE BODY Usually, normal flora occupies body sites that are in contact or have a connection with the environment . Normal flora of the eye/conjunctiva Low numbers present due to: High moisture Blinking mechanically removes bacteria Lachrymal secretions include lysozyme Egs : Staphylococcus epidermidis , Streptococcus pneumoniae, Staphylococcus aureus , Corynebacterium diptheroids some skin normal flora are also present but at fewer amounts egs . Diptheroids (Corynebacterium xerosis ) , Moraxella spp , non-h aemolytic streptococci, staphylococci .

8. 2. Normal flora of the skin Primarily consist of bacteria and fungi, can be in any layer of the skin. Some bacteria can either get washed off or die because the skin is dry, has acidic pH and produce sweat and oil. Resident flora (S. epidermis, S. aureus, Streptococcus, Diptheroids, Yeast-candida). Transient flora (Micrococcus, Bacteroids) Skin normal are generally harmless But it might cause bloodstream, infections if skin was penetrated .

9. 3. Microflora of the oral cavity They have both aerobic and anaerobic bacteria. Most common ones are: C. Diptheroids, S. aureus, and S. epidermis. Also yeast, moulds, protozoa, and viruses can be living in the mouth. Mouth/oral cavity : Lactobacilli, staphylococcus, streptococci, Bacteroids, Corynebacterium, Nocardia. Teeth: streptococcus mutants, haemolytic streptococci, fusobacterium. Poor dental hygiene help bacteria to grow and cause dental caries, gingivitis After dental surgery, there might be a risk of blood stream infection that might cause endocarditis.

10. 4. Normal flora of GIT Stomach: eg . Acid tolerant streptococci, staphylococci lactobacilli, candida albicans, helicobacter pylori. Small intestine: Duodenum: gram positive cocci and rods are more Jejunum: both gram positive and gram negative bacteria, lactobacilli Diptheroids, enterococcus faecalis, yeast-candida albicans Ileum: pH-alkaline, anaerobic gram negative bacteria such as entero bacterial, shigellosis, typhoid. Large intestine: Anaerobic gram negative, non- sporing bacteria Bacteroids, bifidobacteria, lactobacillus, E. coli, protease, yeast, candida and protozoans, Entamoeba histolytica, Trichomonas .

11. 5. Normal Flora of the Respiratory Tract Upper respiratory tract: nasal passage, pharynx, esophagus Egs : Staphylococcus, Streptococcus, Diptheroids, Bactetroids , Micrococci, Haemophilus The pharynx (throat) : Streptococcus pneumoniae , Streptococcus pyogenes, Haemophilus influenza , Neisseria meningitidis Upper intestine : Streptobacilli, Lactobacilli, Enterobacteria , Bacteroides Lower respiratory tract: Trachea, Bronchi, and lungs Its mostly sterile because the mucus membrane removes any microbes

12. 6. Normal flora of the genitourinary tract Normal flora of urinary tract: urethra and bladder are sterile Non-pathogenic gram positive cocci and gram negative enterobacteriaceace may be extremely found as normal flora Norma flora of genital tract: mycobacterium smegmatis is commonly present in both male and female genital tract. Male genital tract: Lactobacillus, Bacteroids, staphylococci and Corynebacterium. Female genital tract: vagina of newborn is colonized by lactobacilli The adult female genital tract has complex normal flora from puberty to menopause The pH is acidic 4.2-4.6. A cidophilic colonizing bacteria eg . Lactobacilli known as Doderlines bacilli, Stap epidermis, streptococci, peptostreptococci , Clostridium species, diptheroides , candida

13. CON’T Urogenital (in different age groups) Lactobacillus spp, D iphtheroid, S. epidermidis, S treptococci, E. Coli , Proteus, Neisseria, Clostridium. In the anterior urethra S. epidermidis Enterococci Diphtheroid E. coli, (nonpathogenic species)

14. FACTORS INFLUENCING THE NORMAL FLORA Local environment Diet Age Sex Immune condition Use of antibiotics

15. ADVANTAGES OF NORMAL FLORA TO THE HOST Normal flora prevents colonization of body areas by pathogens. They do by: Competing for nutrients with pathogens Competing for receptor sites with pathogens Creation of unfavorable environment for the pathogens 2. Normal flora of the gut synthesize vitamin K and vitamin B complex which supplement food sources to the host. 3. They stimulate antibody mediated immune responses that may react with future pathogens thus preventing infection. 4. Lactobacilli in the vagina produces acid which maintains a low PH, and this inhabits the growth of microbes such as Candida albicans. 5. Normal floras such as those in the gut produce antimicrobial substances eg . Fatty acid, peroxidase Bacterocin which kill or inhibit growth of pathogens

16. DISADVANTAGES/ HARMFUL EFFECTS OF NORMAL FLORA They act as opportunistic pathogens in case of immune suppression. May not sufficiently outcompete with pathogens for nutrients thereby giving them a chance to cause disease. Normal flora may be source of infection to other persons Some may cause diagnose confusion Some penicillinase producing microorganisms can aggregate and develop antibiotic resistance (Drug resistant)

17. MECHANISMS THAT CAN DISRUPT NORMAL FLORA Suppression of normal flora by prolonged use of antibiotics Changes in the general health of an individual such as immune suppression. Hormonal changes especially during menstruation and pregnancy. Trauma such as skin breakage and surgery Introduction to new sites e.g. migration of E. coli from anus to urethra leads to UTI. Note: When they are disrupted, normal flora become pathogenic thus causing disease.

18. Opportunistic infections These occur in immunocompromised host; Immunocompromised host includes Damage to epithelia Disruption of normal flora e.g. by antibiotics Impairment of immune system by infection Introduction of bacteria to new sites e.g device-associated infection

19. Very few organisms are always pathogenic Many organisms are potentially pathogenic Most microbes are never pathogenic Microbes and human disease

20. Important definitions to note Colonisation : The presence of viable bacteria on body surfaces without causing infection Infection : The presence of microorganisms causing damage to tissues, usually in the presence of acute inflammation (pain, redness, heat and loss of function) Carrier state: it’s a situation when an individual harbors a potential pathogen and can be a source of infection to others. This can occur after recovery from a disease.

21. Some bacteria are adapted to the pathogenic way of life in humans. They are never part of the normal flora but may cause subclinical infection, e.g. M . Tuberculosis. Some bacteria which are part of the normal flora acquire extra virulence factors making them pathogenic, e.g. E. coli. Some bacteria from the normal flora can cause disease if they gain access to deep tissues by trauma, surgery, especially if associated with a foreign body, e.g. S. epidermidis In immunocompromised patients many free-living bacteria and components of the normal flora can cause disease, especially if introduced into deep tissues, e.g. Acinetobacter Microbes and human disease

22. Microorganisms gain entry into the host by several routes Via the respiratory , gastrointestinal or urogenital tract Through cuts, burns or punctures in the skin

23. Pathogens must overcome various host defenses before they can establish themselves. These include; Physical barriers e.g. the skin Recognition by components of the innate immune system and phagocytosis The acidic environments of the stomach and urogenital tract Various hydrolytic and proteolytic enzymes found in saliva, the stomach, and small intestine.

24. Opportunistic pathogen Disease caused Remarks Escherichia coli (E. coli) Urinary tract infection E. coli is normal flora in the colon but causes UTI when it enters the urethra Staphylococcus aureas (S.aureas) Skin and soft tissue infections s.aureas is normal on the skin, it causes disease when the skin breaks as in trauma, burns or scratching. Candida albicans Oral candidiasis Vaginal candiasis It is normal flora in the vagina & GIT. It take chance of immunosuppression in the host. Clostridium difficile Pseudomembranous colitis Clostridium difficile is normal flora in the gut. It causes diarrhea due to use of antibiotics such as clindamycin Pneumocystis carinii (pneumocystis jiroveci) Pneumonia (PCP) Pneumocystis jiroveci commonly causes pneumonia in immune compromises pts e.g. those with HIV/AIDS. Cryptococcuss neoformans Cryptococcal meningitis a fungus that lives in the environment. People can become infected with C. neoformans after breathing in the microscopic fungus EXAMPLES OF OPPORTUNISTIC PATHOGENS AND INFECTION CAUSED.

25. SYMBIOTIC RELATIONSHIP Symbiosis refers to a close relationship between 2 different organisms i.e. host and symbiont living together. The host is usually larger than the symbiont in this relationship. Symbionts: organisms that usually benefit the person infected eg. Normal flora of the intestine help in the synthesis of vitamin . Symbiotic relationships are classified into 3 i.e.: - Mutualism, Commensalism, Parasitism Mutualism - This is an association or relationship in which both organisms (host & symbiont), benefit from the relationship. E.coli in the colon synthesize vitamin K that is important for the human body (host), and the host provides nutrients and habitat for E.coli

26. Con’t Commensalism – A ssociation in which one member of the association benefits from the relationship and the other member does not benefit. Most normal flora on the body (skin surface) are examples of commensal relationship. Parasitism - A ssociation an association in which one organism benefits whereas the other is harmed. Egs: Helminthes such as ascaris lumbricoides are examples of a parasitism association, Most worms live in the human intestine, obtain nutrients and also cause diseases.

27. Revision questions Define a normal flora Give three examples of normal flora found in the colon Define parasitism, symbiosis, opportunistic infection, commensal Outline 3 ways how normal flora protect the host from infection Name 2 examples of normal flora from the following body sites Skin Nose Throat Vagina 7. State the different between a normal flora and a carrier state