HOST PATHOGENS INTERACTION…….

Origen of microbial flora  The fetus is in a sterile environment during first few days of life  New born……. Many micro organisms

 Once established onto or into a particular body site……..  Symbiosis, commensalism, parasitism.

Characteristics of indigenous flora Indigenous flora Body sites …same or different flora Resident microbial flora Transient flora

Carriers Carrier state Carrier state may be acute or chronic Colonizing….host resistance….microbial flora provide protection

Factors that determine the composition of the usual microbial flora Presence of organisms …. Influenced by nutritional and environmental fectors.

Composition of the microbial flora at different body sites Human host…colonized by….app. 100 microbs Effectiveness of host…..low incidence of infection Clinical microbiologist must be able to recognize and identify the types of microbs …at diff body sites

Usual flora of the skin Skin has numbr of mechanisms...prevent infections Skin…..vide veriety of microbs Reduce but not eliminated by scrubbing and washing

Composition of flora….depends… Concentrate….. Moist areas Aerobic diptheroids…moist areas staphylococcus …hair follicles Inhibit pathogenic bacteria P.acnes colonize deep sebaceous glands

Usual flora of the mouth Contain larg number of bacteria Many bind… buccal mucosa & tooth surface Bacterial plaques streptococci Plaque…..low oxidation potential at tooth surface…growth of anarobes

Usual flora of the Respiratory tract Upper….lower tracts Upper….mouth,nasopharynx,oropharynx,larynx Lower….tracea,bronchi,lungs…protected by cilia Usual flora of the mouth….streptocococci Upper….mouth,nasopharynx,oropharynx… microbs show some diff Staphylococcus….30% of normal individuals colonize anterior nares

Individuals ….hospitalized…upper r.t…..by gram negative bacteria. Orophyarynx….streptococci A number of species…...s.mutans, s.milleri, s.sanguis, Hospitalizwd patients…..gram negative rods

Usual flora of the gastrointestinal tract Comprisis….esophagus,stomach,s.intestine,col on Equiped…defenses & antimicrobial fectors Ingesting organisms Don’t multiply ….esophagus, stomach In ingested food…as transient flora. Most mirobs susceptible...acid ph…destroy…. Exception sper forming becteria,cysts

Stomach acidty….reduce Smal intestine….few microbs In the colon… Anarobs…90% large intestine Gram positive cocci, yeasts, pseudomonas Population….antibiotics In some cases …microbs supressed….othr able to proliferate…enterocolititis

Role of the microbial flora in the pathogenesis of infectious disease Microbial flora….provide some benefits… symbiotic relationship Some opportunists….when damage..disturbed or change…or immune system Trauma….accidentalor surgical….not part of microbial flora…

Host immune response….reduces…due to ….drugs… Lymphoma, leukemia….reduce immune response Microbial flora…initiat an infection….in patients with chronic illnesses

Role of the microbial flora in the host defense against infectious disease Beneficial effects Immunological competence Immune system developed or undeveloped Newborn….not developed

Micobial flora…block colonization by extragenious pathogens Indigenous flora altered gastroenteritis Pathogenic species C. albcans

Microbial flora… Important role in health and diseases Eradication….negative effects Knowledge in…clinical samples

Microbial factors contributing to pathogenesis and virulence

Pathogenesis Ability to produce disease True pathogens… health immuno competent Yersinia pestis &bacillus anthracis

Pt population changed Long life…more susceptible to …… Normal flora….increase frequency in infections Haemophilus influenzae…sometime life threating infection Staphylococcus epidermidis….somtimes infectious Both are called upertunistics

So…the definition of a pathogen must be expended to apply ….when conditions for infection are met. Healthy 20 year old student……short pathogen than healthy 90 year old person, a transplant patient Iatrogenic infection……result of medical treatment

Virulence Ability of a micro organism to cause disease or is the degree of pathogenicity Measured by number of micro organisms to cause infection in the host Low infective dose….more virulent

1 st lab Diagnostics of infectious diseases Urine specimen collection 1.Urine specimens will obtained from patients by clean-catch midstream collection; samples will transported without delay to the microbiology laboratory 2.Urine samples for culture will collected into a container the specimen will stored at 4°C (in a fridge). Low temperature serves to inhibit bacterial replication in the specimen, until the specimen is processed in the laboratory. This is important because the number of bacteria in the urine specimen is important in determining if there is clinically significant bacteriuria. If the specimen is not properly stored small numbers of contaminating bacteria may multiply to large numbers and create a false impression of significant bacteriuria. The urine sample will routinely processed for culture. MacConkey agar and nutrient agar will used for culturing E.coli.

Categories of Patients Catheterized Patients Patients with Kidney Problem Pyelonephritis Cystitis Bacteriuria Patient with other Illness Septcaemia Stroke Immunocompromised Patients

Sample Processing in Laboratory Growth on MacConkey agar Laboratory procedure that will carried out includes growth on MacConkey agar plates. These MacConkey agar plates will prepared by dissolving 5.1 gram of MacConkey agar in 100ml of distilled water. This mixture will autoclaved at 121ºC for 45 minute. After cooling the media, it will poured in petri dishes.

These plates will kept at room temperature till the media in these plates get solidify. When media will solidified, it will kept in incubator for 24 hrs at 37ºC. Now the plates will ready for culture growth and collected urine samples will spread on MacConkey agar plates with the help of sterile loop. The procedure will carried out near flame under aseptic conditions. These MacConkey plates will again kept in incubator at 37 ºC for 24 hours. After 24 hours when the plates will examined for bacterial growth, a mixed culture will seen with different colours and types of colonies.