Micropara

• Ecology


  Systematic study of the interrelationships that exist between organisms and their environment
• Microbial Ecology


  Study of the numerous interrelationships between microbes and the world around them – how microbes interact with other microbes, how microbes interact with organisms other than microbes, and how microbes interact with the nonliving world around them
• Symbiotic relationship or symbiosis


  Living together or close association of two dissimilar organisms (usually two different species)
• Symbionts


  Organisms that live together in such a relationship
• Neutralism


  • A symbiotic relationship in which neither symbiont is affected by the relationship
  • Reflects a situation in which different microorganisms occupy the same ecologic niche, but have absolutely no effect on each other
• Mutualism


  • A symbiotic relationship that is beneficial to both symbionts (the relationship is mutually beneficial)
  • Humans have a mutualistic relationship with many of the microorganisms of their indigenous microbiota
  • Example: E. coli which obtains nutrients from food materials ingested by the host and produces vitamins (such as vitamin K) that are used by the host; protozoa that live in the intestine of termites
• Microbiota


  Microorganisms that make up our indigenous microflora, the microbiome consists of not only the microorganisms but also the genes they possess and their effect on the local environment within the body
• It is now known that microbes contribute more genes responsible for human survival than our own genes
• It is estimated that bacterial protein genes are 360 times more abundant than human genes
• Positive Effects of the Interactions between the Host and Its Microbiome

  • Provides metabolic potential and supplies many vitamins and other nutritional factors
  • Helps to train the immune system and supports host defense functions
  • Affects neurodevelopment
  • Has anti-inflammatory properties
  • Has antioxidant activity
  • Resists colonization by pathogenic microorganisms
  • Maintains a healthy digestive system
• Conditions for proper growth vary throughout the body; thus, the types of resident microbiota differ from one anatomic site to another
• Blood, lymph, spinal fluid, and most internal tissues and organs are normally free of microorganisms
• Transient microbes


  Microbes that take up temporary residence on and within humans since the body is exposed to microorganisms from the external environment; attracted to moist, and warm body areas
• Reasons Why Transient Microbes Live Only Temporarily

  • They may be washed from external areas by bathing
  • They may not be able to compete with the resident microbiota
  • They may fail to survive in the acidic or alkaline environment of the site
  • They may be killed by the substances produced by the resident microbiota
  • They may be flushed away by bodily excretions and secretions (urine, feces, tears, and sweat)
• Dysbiosis


  Destruction of the resident microbiota disturbs the delicate balance established between the host and its microorganisms
• Diarrhea


  • Usually the result of such an imbalance due to prolonged therapy with certain antibiotics which often destroys many of the intestinal microbiota
• Anatomic Locations of Bacteria and Yeasts Found as Indigenous Microbiota of Humans

  • Anaerobic Gram-negative Cocci
  • Anaerobic Gram-positive Cocci
  • Bacteroides spp.
  • Clostridium spp.
  • Candida spp.
  • Diphtheroids
  • Enterobacteriaceae
  • Fusobacterium spp.
  • Enterococcus spp.
  • Haemophilus spp.
  • Lactobacillus spp.
  • Neisseria meningitidis
  • Micrococcus spp.
  • Prevotella/Porphyromonas spp.
  • Staphylococcus spp.
  • Streptococcus spp.
• Microbiota of the Skin


  • Relatively inhospitable environment for microorganisms
  • It varies in temperature, generally low pH, high levels of salt, and lack of nutrients
  • Resident microbiota of the skin consists primarily of bacteria and fungi – as many as 300 different species, depending on the anatomic location
• Factors that affect the number and variety of microorganisms on the skin

  • Anatomic location
  • Amount of moisture present
  • pH
  • Temperature
  • Salinity
  • Presence of chemical wastes, such as urea and fatty acids
  • Presence of other microbes, which may be producing toxic substances
• Three most common bacteria on the skin

  • Staphylococcus
  • Corynebacterium
  • Propionibacterium
• Microbiota of the Ears and Eyes

  • Middle ear and inner ear are usually sterile, whereas the outer ear and the auditory canal contain the same types of microbes as are found on the skin
  • The external surface of the eye is lubricated, cleansed, and protected by tears, mucus, and sebum
  • Nasal passages and throat have an abundant and varied population of microorganisms
  • Many microorganisms found in healthy nose and throat are harmless while others are opportunistic pathogens which cause disease under certain circumstances
  • Healthy carriers – they harbor virulent pathogens in their nasal passages or throat, but do not have the diseases associated with them like diphtheria, pneumonia, meningitis, and whooping cough; they were able to transmit the disease to susceptible person
• Microbiota of the Oral Cavity


  • Shelter for numerous anaerobic and aerobic bacteria
  • Anaerobic microbes are usually found in gum margins, crevices between the teeth, and deep folds on the surface of the tonsils
  • Bacteria thrive especially in particles of food and in the debris of epithelial cells around the teeth
  • Food remaining on and between teeth provides a rich nutrient medium for bacterial growth which develops into tooth decay, gingivitis, and more severe periodontal diseases
  • Microbes that have been isolated from healthy human mouth: Gram-positive and Gram-negative (cocci and bacilli), Spirochetes, Bacteria (Actinomyces, Bacteroides, Fusobacterium, Lactobacillus, Porphyromonas, Streptococcus, Neisseria, and Veillonella), Yeast (sometimes), Mold-like organisms, Protozoa, Viruses, Various sp. of alpha hemolytic streptococci – most common microorganisms in the indigenous microbiota of the mouth
• Reservoirs


  The environment, or place of origin of an infecting agent
• Reservoirs


  • Humans
  • Animals
  • Environment
• Direct transmission


  Host direct contact to microbial reservoir
• Indirect transmission


  Host encounters the microorganism by an intervening agent (vector or vehicle)
• Colonization


  Persistent survival of microorganisms on the surface of human body
• Colonization sites


  • Skin
  • Mucous Membrane
• Mucus production


  • Provision of antibacterial substances to mucosal surface: Lysozyme, Lactoferrin, Lactoperoxidase
• Mucosal linings


  • Nasopharynx (secretions)
  • Mouth (saliva)
  • Lungs (macrophages)
  • Stomach (Low pH)
  • Small Intestine (Mucus, Bile)
  • Colon (Bile)
  • Vagina (Low pH)
  • Bladder (Low pH)
  • Urethra (Urine)
• Microorganism's perspective on colonization

  Mutually beneficial, first step of developing infection and disease, sterile body sites (blood, CSF and urinary bladder)
• Microorganisms colonizing different body sites

  • Skin: P. acnes, S. epidermidis, viridans streptococci, Enterococcus
  • Mouth and Oral Cavity: Viridans streptococci, S. epidermidis, Neisseria species
  • Colon: Bacteroides, Lactobacillus, Clostridium, Eubacterium, E. coli
  • Urethra: Diptheroids, alpha and gamma hemolytic streptococci, S. epidermidis
• Factors contributing to disruption of skin and mucosal surfaces

  • Trauma (abrasions, surgical wounds, needlesticks)
  • Inhalation
  • Implantation of Medical Devices
  • Overuse of antibiotics
• Nonspecific responses


  • Cellular: Phagocytes (neutrophil and macrophages)
  • Biochemical: Complement, Coagulation System, Cytokines
• Phagocytes


  Neutrophils and macrophages
• Complement system


  Enhances the activities of different cells in nonspecific and specific defensive responses
• Coagulation system


  Attracts phagocytes to the site of infection, walls off site of infection
• Cytokines


  Enhance the activities of different cells in nonspecific and specific defensive responses
• Inflammation


  • Swelling, Redness, Heat, Pain
• Diapedesis


  Migration of phagocytes through blood vessel walls to site of infection