Microbiology and Immunology OPT 416 HS246 PDF

MICROBIOLOGY AND IMMUNOLOGY OPT 416 HS246 Dr MAIMUNAH MUSTAKIM  2 LEARNING OBJECTIVES AT THE END OF THE LESSON, STUDENTS ARE ABLE TO IDENTIFY AND EXPLAIN/DESCRIBE: I. How microorganisms interact with their h...

MICROBIOLOGY AND IMMUNOLOGY OPT 416 HS246 Dr MAIMUNAH MUSTAKIM  2 LEARNING OBJECTIVES AT THE END OF THE LESSON, STUDENTS ARE ABLE TO IDENTIFY AND EXPLAIN/DESCRIBE: I. How microorganisms interact with their hosts. II. Characteristics of normal flora vs. pathogen. III. Body sites of microbe-free. IV. Principles of infectious diseases. V. Reservoir of pathogens, portal of entry and exit of pathogens. VI. Methods of microbial transmission. 3  4 Natural relationship on man and microorganisms ’ Forms of symbiotic relationships ◦ Mutualism ‘ Association in which both partners benefit ‘ Bacteria and synthesis of vitamins K and B in large intestine ◦ Commensalism ‘ Association in which one partner benefits and other is unharmed ‘ Flora living on skin ◦ Parasitism ‘ Association in which the microbe benefits at expense of host ‘ Pathogenic infection  5 HOST-MICROBES INTERACTION  Microbes – pathogens / harmless.  Benefits – resides on body surfaces – normal microbiota / flora.  Body fluids and tissues as source of nutrients  Immunocompromised individuals – malnutrition, cancer, AIDS, diseases, surgery, wounds, genetic defects – exposed to opportunistic pathogens.  Normal Microbiota (Flora)  Normal microbiota defined as populations of microorganisms routinely found growing on the body of healthy individual  Resident flora typically inhabit body sites for extended periods (long term)  Transient flora are temporary They form associations for a short period and are replaced. 7 MAIMUNAH MUSTAKIM (SEPT 2011) 8  9 Normal human flora if  Normal Microbiota Protective role of normal microbiota Contributions include Protection against potentially harmful organisms Stimulate immune system If normal microbiota are killed or growth suppressed, pathogens may colonize and cause disease Example : Lactobacillus sp. (FGT) – suppress growth of yeast Candida albicans – however person on antibiotic treatment – normal bacterial population (Lactobacillus sp.) will be inhibited – therefore fungi will overgrow – cause disease - candidiasis  11 ’ Protection against potentially harmful organisms. ◦ Normal flora competitively exclude pathogens through: 1. Covering binding sites used for pathogenic attachment - prevents invading microorganisms from adhering to host cells 2. Consuming available nutrients – less nutrients available for pathogens. 3. Producing toxic compounds: i. Hair follicle - Propionibacterium sp – degrade lipids from skin glands and release fatty acids – inhibit growth of pathogens. ii. GIT – E.coli – synthesize colicins. femalegenitaltract iii. FGT – Lactobacillus sp – produce lactic acids – acidic pH – inhibit potential disease-causing organisms.  12 FGT MICROBIOTA (Streptococci) (Fusobacterium) digestbacteria'scellwall from the skin  15 ’ Stimulate immune system 1) Early and consistent exposure to certain microbes in the gut – stimulates T cells – preventing the immune system from overacting to harmless microbes and substances - prevent allergies. 2) Prime the adaptive immune system - response increased against normal flora that breaches body’s anatomical barriers ‘ May cross-react with pathogen encountered later  Anatomical Barriers as Ecosystem Skinand mucous membranes provide anatomical barriers to infection Also supply foundation for microbial ecosystem Microbialcommunity offers protection from disease-causing organisms Intimate interaction between microorganisms and human body is an example of symbiosis  17 ’ Dynamic nature of normal Microbiota Ifrom fetus ◦ Normal flora established during birth process ◦ Once established, composition of flora is dynamic ‘ Changes in response to physiological variation within the host ‘ Each member of flora ecosystem influenced by presence and condition of other members 18 19  Principles of Infectious Disease If colonized organisms have parasitic relationship with host, the term infection applies Infection does not always lead to noticeable adverse effects Termed subclinical or inapparent (unnoticed) Completely asymptomatic (no signs or symptoms) Infection that results in disease is termed infectious disease Disease causes characteristic signs and symptoms Signs are effects that can be observed through examination Rash, puss formation and swelling. Symptoms are effects experienced by patient Pain and nausea. Definitioninfectiousdisease thatiscausedbypathogenic microor disease  Principles of Infectious Disease One infectious disease may leave individual predisposed to developing new disease Initial disease is termed primary infection Additional infections resulting from primary infection are termed secondary infection 22  Principles of Infectious Disease Characteristics of infectious disease Disease that spreads from host to host termed communicable or contagious Ease of spread partly determined by infectious dose Infectious dose is number of organisms required to establish infection Diseases with small infectious dose more easily spread than those requiring large numbers MAIMUNAH MUSTAKIM (SEPT 2011) 24  25 MICROBIAL DISEASE INCUBATION INFECTIOUS DOSE (CAUSATIVE AGENT) - PERIOD symptoms Cholera (Vibrio cholerae) - 12 – 48 hrs Large numbers must be diarrhea ingested to effect disease due to sensitivity to stomach acid Salmonellosis (S. enterica) – 6 – 72 hrs Bacteria sensitive to stomach diarrhea, vomiting, fever acid – large number required for infection Campylobacteriosis 1 – 5 days Small infecting dose. (Campylobacter jejuni) – Only 500 organisms required fever, vomiting, diarrhea, to initiate disease. dysentry (bloody diarrhea)  Principles of Infectious Disease Development of infectious disease: Disease progression follows several stages Incubation Time between introduction of organism to onset of symptoms Incubation period depends on numerous factors Illness Follows incubation Individual experiences signs and symptoms of disease Convalescence Period of recuperation (healing) and recovery Infectious agents may still be spread 27  28 ’ Duration of symptoms ◦ Acute ‘ Symptoms have rapid onset and last only short time ◦ Chronic ‘ Symptoms develop slowly and persist ◦ Latent ‘ Infection never completely eliminated ‘ Infection becomes reactive  Principles of Infectious Disease Distribution of pathogen Infections often described according to distribution within the body Localized Infection limited to small area Example = boil (bisul) Systemic or generalized Agent has spread or disseminated throughout the body Example = measles Toxemia Toxins circulating in blood Viremia Viruses circulating in blood Septicemia Acute life-threatening illness causes by infectious agent or its products circulating in blood  30 Microbial Reservoirs (Sources) Reservoirs can be: 1. Human 2. Animal 3. Environment  31 ’ Human reservoirs ◦ Infected humans most significant reservoirs ‘ Primarily of communicable diseases ‘ In some cases humans are only reservoir ‘ In this case disease is easier to control ◦ Human reservoirs as ‘ Symptomatic infections ‘ Obvious source of infectious agents ‘ Ideally infected individuals understand the importance of precautions such as hand washing to inhibit transmission ‘ Asymptomatic carriers ‘ Individual harbors pathogen with no ill effects ‘ They may shed organisms intermittently for long periods of time ‘ Some have asymptomatic infection ‘ More likely to move about spreading pathogen  32 ’ Animal reservoirs ◦ Source of some pathogens ◦ Disease transmitted by non-human animal reservoirs are termed zoonotic ‘ Disease often more severe in humans than in normal animal ‘Infection in humans is accidental Eg Rabies Lyme disease Dengue  33 ’ Environmental reservoirs ◦ Some pathogens have environmental reservoirs, which can include ‘ Water ‘ Soil ◦ These pathogens difficult or nearly impossible to eliminate  34 ’ Portals of entry ◦ Pathogen must enter and colonize new host ‘ Colonization is prerequisite for causing disease ◦ Route by which pathogen enters body is termed portal of entry ◦ Major portals of entry include ‘ Eyes ‘ Ears ‘ Respiratory tract ‘ Broken skin ‘ Digestive tract ‘ Genitourinary tract  35 ’ Portals of exit ◦ Microbes must leave one host in order to be transmitted to another ‘ Organisms inhabiting intestinal tract are shed in feces ‘ Organisms inhabiting respiratory tract are expelled in respiratory droplets of saliva ‘ Organisms of the skin are shed with skin cells as they slough off  36 MICROBIAL TRANSMISSION ’ Transmission ◦ Successful pathogen must be passed from reservoir to next susceptible host ◦ Transmission of pathogen via contact with food, water or living agent is termed horizontal transmission ◦ Transmission via transfer of pathogen from mother to fetus or child through breast feeding is termed vertical transmission  37 (Food, water)  38 ’ Contact ◦ Direct contact ‘ Occurs when one person physically touches another ‘ Can range from simple contact to intimate contact ‘ In some cases direct contact is primary route of transmission ‘ Hands are main vehicle of contact transmission ‘ Hand washing physically removes organisms ‘ Important in preventing direct contact transmission ‘ Pathogens that do not survive for extended periods in the environment usually spread by direct contact  39 ’ Contact ◦ Indirect contact ‘ Involves transmission of pathogens via inanimate objects or fomites ‘ Usually clothing, tabletops, doorknobs and drinking glasses ‘ Organisms on hands or fingers of carrier can be transferred to objects and picked up by another individual ‘ Handwashing important control measure  40 ’ Contact ◦ Droplet transmission ‘ Microbe-laden (heavily loaded) respiratory droplets generally fall to the ground within three feet of release ‘ People in close proximity can inhale infected droplets, spreading disease via droplet transmission ‘ Droplet transmission considered direct transmission because of the close range required for transmission 41  42 ’ Food and water ◦ Pathogens can be transmitted through contaminated food and water ◦ Food can become contaminated in number of different ways ‘ Organisms can originate with animal ‘ Organisms can be inadvertently added during food preparation ‘ Cross-contamination occurs when organisms from one food are transferred to another from an improperly cleaned work surface ‘ Cutting boards and knives ‘ Sound food handling practices can prevent foodborne transmission and disease 43  44 ’ Food and water ◦ Waterborne disease outbreaks can involve large numbers of people ‘ Due to the fact that municipal water is distributed to large areas ◦ Prevention of waterborne diseases requires chlorination and filtration of public water sources and proper disposal of sewage  45 ’ Air ◦ Respiratory droplets can be transmitted through the air ‘ Smaller droplets dry in the air leaving one or two organisms attached to dry material ‘ Creates droplet nuclei ‘ Droplet nuclei can remain suspended indefinitely in presence of light air currents ◦ Airborne transmission is difficult to control ‘ Ventilation systems aimed at circulating air in buildings ‘ HEPA (High-efficiency particulate air) filters effective at removing airborne organisms 46  47 Aerosol = liquid droplets dispersed in air  48 ’ Vectors ◦ Any living organism that can carry a disease- causing microbe ‘ Most common are arthropods ‘ Vector may carry organism internally or externally ◦ Control of vector-borne disease directed at controlling arthropod population 49