Host-Pathogen Interactions & Flora (26.09.2023) - PDF

HOST-MICROORGANISM INTERACTIONS & FLORA Assist. Prof. Dr. Güner EKİZ DİNÇMAN Faculty of Pharmacy Department of Pharmaceutical Microbiology 26.09.2023 1 90% of our body is made up of microorganisms!!! 2 3 4  Normal microflor...

HOST-MICROORGANISM INTERACTIONS & FLORA Assist. Prof. Dr. Güner EKİZ DİNÇMAN Faculty of Pharmacy Department of Pharmaceutical Microbiology 26.09.2023 1 90% of our body is made up of microorganisms!!! 2 3 4  Normal microflora do not colonize the internal organs, blood, lymph, or the nervous systems. The growth of microorganisms in these normally microbially sterile environments indicates serious infectious disease. 5 Human, animal and plants are constantly in a close interaction with microorganisms found in nature. In human body; - skin - organs with outside opening - organs associated with external environment, are in a constant interaction with microorganisms This interaction rarely represents as disease! 6 HOST-MICROORGANISM INTERACTIONS Mutualism Association in which both partners benefit Commensalism Association in which one partner benefits and other is unharmed Parasitism Association in which the microbe benefits at expense of host 7 PRINCIPLES OF INFECTIOUS DISEASE 8 PRINCIPLES OF INFECTIOUS DISEASE 9  PRINCIPLES OF INFECTIOUS DISEASE § Characteristics of Infectious Disease Communicable or contagious diseases easily spread Infectious dose is number of microbes necessary to establish infection - ID50 is number of cells that infects 50% of population - Shigellosis results from ~10–100 ingested Shigella - Salmonellosis results from as many as 106 ingested Salmonella enterica serotype Enteritidis 10  PRINCIPLES OF INFECTIOUS DISEASE § Course of Infectious Disease Incubation period: time between infection and onset - Varies considerably: few days for common cold to even years for leprosy - Depends on growth rate, host’s condition, infectious dose Illness: signs and symptoms of disease - May be preceded by prodromal phase (vague symptoms) Convalescence: recuperation, recovery from disease Carriers may harbor and spread infectious agent for long periods of time in absence of signs or symptoms 11 PRINCIPLES OF INFECTIOUS DISEASE 12 PRINCIPLES OF INFECTIOUS DISEASE 13 ESTABLISHING THE CAUSE OF INFECTIOUS DISEASE 14 ESTABLISHING THE CAUSE OF INFECTIOUS DISEASE 1.Isolation: The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms. 2.Cultivation: The microorganism must be isolated from a diseased organism and grown in pure culture. 3.Causation: The cultured microorganism should cause the disease when introduced into a healthy organism. 4.Re-Isolation: The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent 15 ESTABLISHING THE CAUSE OF INFECTIOUS DISEASE Modern Adaptations and Limitations 1.Asymptomatic Carriers: Some pathogens can be found in healthy individuals, contradicting the first postulate. 2.Non-Culturable Organisms: Some pathogens cannot be cultured in a lab, making the second postulate difficult to satisfy. 3.Ethical Concerns: The third postulate may not be ethical to satisfy for certain diseases, especially in humans. 4.Complex Diseases: Some diseases, like many chronic diseases, may have multiple contributing factors, including more than one causative agent, making them not easily explained by Koch's Postulates. 5.Molecular Koch's Postulates: With the advent of molecular biology, a set of "Molecular Koch's Postulates" has been proposed to establish causality at the genetic and molecular levels. 6.Viral Diseases: Koch's Postulates were formulated before the discovery of viruses, which cannot be cultured in the same way as bacteria and often require living cells to replicate 16  NORMAL FLORA OF THE HUMAN BODY Normal flora is defined as populations of microorganisms routinely found growing on the body of healthy individuals Inhabit 17 NORMAL FLORA OF THE HUMAN BODY 18 NORMAL FLORA OF THE HUMAN BODY 19 NORMAL FLORA OF THE HUMAN BODY 20 NORMAL FLORA OF THE HUMAN BODY Microorganisms choose a body site suitable for their growth and survive there. Survival depends on physiologic factors such as: - pH in different parts of the body - Moisture - Temperature - Nutrients - Natural inhibitory substances 21 PERMANENT (RESIDENT) FLORA Resident flora consists of relatively fixed type of microorganisms regularly found in a given area at a given age; if disturbed, it promptly reestablished itself. Members of the normal flora may become pathogenic if: - Removed from the restrictions of that environment and introduced into the bloodstream or tissues - The balance between the microorganisms is lost - The host immune systems is weakened 22 PERMANENT (RESIDENT) FLORA Opportunism: happens when some members of the normal flora cause disease taking advantage of an opportunity such as disrupted barriers or weakend immune response. These microbes are called opportunistic pathogens Many infectious diseases are caused by opportunistic pathogens. eg. Staphylococcus aureus, Candida albicans Strict pathogens are true pathogens – are always associated with disease 23 TRANSIENT FLORA Transient flora consists of microorganisms that inhabit the body surface or mucous membranes for a limited period (temporarily living on/within humans) They establish themselved briefly for colonization without disease. 24 TRANSIENT FLORA - If the transient flora is removed by various factors, it does not reform. A new flora is replenished. - The type of microorganisms in a certain body site depends on the conditions of that body site. - Transient flora usually exists together with the permanent flora. - If the permanent flora is removed, transient flora may cause disease. - Most members of the transient flora are nonpathogenic or opportunistic pathogens. 25 ROLE OF FLORA IN THE ORGANISMS - Most of the microorganisms of the flora are commensals § They benefit from the body temperature, moisture and debris material, and survive with no harm to human body - Some of the microorganisms are found as mutualistic: § Some bacteria in the digestive tract help in the synthesis of vitamins § Some bacteria prevent colonization by pathogenic bacteria via competition eg. Lactobacilli in adult female vagina change the pH of the vagina. By making it more acidic prevents colonization by gonococci. 26 FLORA OF OUTER ENVIRONMENT - Microorganisms found temporarily or permanently in certain environments Air, soil, water 27  FLORA OF OUTER ENVIRONMENT Air is not suitable for the growth and survival of the microorganisms Microorganisms diffuse into the environment via air flow - The survival of the microorganisms on dust particles or water droplets depends on: - Resistance to dryness - Existance of organic material - Moisture levels - Temperature of the environment 28 Microorganisms that cause diease via the respiratory tract: - Mycobacterium tuberculosis 29 SOIL MICROBIAL FLORA Soil is an environment where organic material and water constantly exist There are numerous microorganisms in the soil These organisms play an important role in biotransformation Nitrogen, sulphur, carbon transformation happens via soil microorganisms. 30 Pathogenic microorganisms transmitted via soil: Clostridia (C. tetani, C. botulinum) Bacillus anthracis Coccidioides immitis Histoplasma capsulatum Cryptococcus neoformans 31 WATER MICROBIAL FLORA Microorganisms may even exist in water from purified sources The most important organisms are the ones which pass from human or animal faeces into the water 32 Pathogenic microorganisms transmitted via water: Bacteria Salmonella typhi Vibrio cholera Shigella Escherichiae Enterobacteriaceae and Leptospirae Viruses Salmonella Polio virus Hepatitis A virus Other enteroviruses Protozooa Entomoeba histolytica Shigella 33  Normal Microflora of the Skin ü As the largest organ of the human body, skin is colonized by beneficial microorganisms and serves as a physical barrier to prevent the invasion of pathogens. ü If the barrier is broken or when the balance between commensals and pathogens is disturbed, skin disease or even systemic disease can result. ü The composition of microbial communities: primarily dependent on the physiology of the skin site, with changes in the relative abundance of bacterial taxa associated with moist, dry and sebaceous microenvironments 34 Normal Microflora of the Skin 35  Normal Microflora of the Oral Cavity The oral cavity is a complex, heterogeneous microbial habitat Saliva contains antimicrobial enzymes - But high concentrations of nutrients near surfaces in the mouth promote localized microbial growth The tooth consists of a mineral matrix (enamel) surrounding living tissue (dentin Day 1 1436 mm2 and pulp) Extensive growth of oral microorganisms, especially streptococci, results in a thick bacterial layer (dental plaque) Day 10 22,522 mm2 As plaque continues to develop, anaerobic bacterial species begin to grow 36  Normal Microflora of the Oral Cavity As dental plaque accumulates, the microorganisms produce high concentrations of acid that results in decalcification of the tooth enamel (dental caries) The lactic acid bacteria Streptococcus sobrinus and Streptococcus mutans are common agents in dental caries. Lactobacillus and Actinomyces are also associated with caries. Actinomyces odontolyticus colonizes infants before eruption of teeth. ORAL FLORA IMPORTANT!! Half of the microorganisms in saliva and 2/3 of microorganisms in gum pockets are anaerobes 90-94% of microorganisms that cause root canal inflammation are anaerobes Total number of microorganisms in saliva is 43 million-5.5 billion/ml 750 million bacteria in 1 ml of saliva 200 billion bacteria/gr in gingival sulcus and teeth plaque 38 RESPIRATORY TRACT FLORA Pharynx Contains a rich flora similar to oral flora Nonhemolytic and alpha hemolytic streptococci Neisseria, Haemophilus Staphylococci, Corynebacteria Peptostreptococci!!! Esophagus Low levels of normal flora Microorganism in food and saliva (transient flora) 39 RESPIRATORY TRACT FLORA Nose and Upper Resp. Tract Streptococci (alpha hemolytic and non hemolytic) Staphylococci (S. epidermidis and S. aureus) Corynebacteria Neisseriae Lower Resp. Tract From larynx to trachea the number of bacteria decrease Lower resp. tract is sterile, no bacteria exist 40 Haemolysis of Streptococci and its types: Hemolysis The breakdown of red blood cells (RBC). A substance that causes hemolysis is a hemolysin. Alpha, beta and gamma: - indicate three types of streptococci based on haemolytic reactions observed on blood agar plates. 41 Normal Microflora of the Gastrointestinal Tract The human gastrointestinal (GI) tract Consists of stomach, small intestine, and large intestine Responsible for digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora Contains 1013 to 1014 microbial cells 42 43 Normal Microflora of the Gastrointestinal Tract ØFunctions and Products of Intestinal Flora Intestinal microorganisms carry out a variety of essential metabolic reactions that produce various compounds The type and amount produced is influenced by the composition of the intestinal flora and the diet Compounds produced include: - Vitamins - Gas, organic acids, and odor - Enzymes  Normal Microflora of Other Body Regions § Urogenital Tract The microbiota in urine is less abundant and less diverse than the microbiota in other sites of the body, such as the gut. - For instance, the female urinary microbiota is estimated to contain 104 – 105 colony-forming unit (CFU)/ml in comparison with 1012 CFU/g in feces. ü Most genera are shared in the urinary microbiome of healthy men and women. Common genera: Prevotella, Escherichia, Enterococcus, Streptococcus or Citrobacter Genus Pseudomonas has only been described in men Corynebacterium and Streptococcus, more abundant Lactobacillus, more abundant in women Comparison between urinary, vaginal and gut bacterial communities: Most of the urobiome studies have been focused on bacteria although the presence of fungi, viruses and archaea in urobiome has also been described.  Normal Microflora of Other Body Regions ØThe vaginal microbiome is an intricate and dynamic microecosystem that constantly undergoes fluctuations during the female menstrual cycle and the woman’s entire life ØLactobacillus is the most frequently isolated microorganism from the healthy human vagina, this includes Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus iners, and Lactobacillus jensenii