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resident flora microorganisms that live on or within the body in non sterile areas without causing harm as long as skin and mucosa are intact examples of sites where normal flora are found eyes, nose and throat, skin, large intestine urinary and reproductive systems What do resident flora do? physically block the attachemetn of pathogens or secrete molecules that inhibit pathogen growth = can cause opportunistic infections if they enter body through wound, surgical incision, after dental work, or a catheter, or enter bosy of immunocomprimised person How do resident flora cause infection? When misplaced ... fecal flora (e cloi normal flora of rectum) to UI or abdominal cavity or skin flora to catheter communicable diseases person to person, infected blood or body fluids, caused by microorganisms that live and reproduce in a human host ... all communicable diseases are infectious but not all infectious diseases are communicable pathogens disease producing microorganisms = cause disease by binding to specific receptors on human host cell 3 ways pathogens cause disease in human host cell 1 - direct destruction of host cell 2 - interference with the host's metabolic function 3 - exposing the host cell to toxins produced by pathogen pathogenicity qualities of pathogens that promote infection and disease What factors affect pathogenicity? virulence inefectivity toxigenicity antigenicity antigenic variability pathogenic defense mechanisms confection superinfection reservoirs people, equipment, water, animal BREAK CHAIIN = SANITIZING ENVIRONMENT OR ANTIMICRROBBIAL DRUGS TO CARRIER portals of exit excretions, secretions, skin, droplets BREAK CHAIN = HANDWASHING, COVERING AREAS OR TRASH DISPOSAL means of transmission direct contact, droplet, vectors, airborne BREAK CHAIN = ISOLATION, FOOD HANDLINGG, AIRFLOW CONTROL, UNIVERSSAL PPRECUATIONS, STERILAZATION, HAND WASHING portal of entry mucous membranes, gi tract, gu tract, respiratory tract, broken skin susceptible host immunosupression, diabetes, surgery, burns, elderly infectious agents bacteria, fungi, viruses, protozoa, rickettsiae bacteria single celled microorganism without membrane organelles, can live indepently aerobic = need oxygen anaerobic = no oxygen endotoxins contained in structural part of bacterial wall and cause inflammatory resonse in host cell exotoxins some bacteria produce toxins and results in host cell lysis or dysfunction .. potent proteins released in surrounding tissues = cause local or systemic injury to the host EX. = neurotoxin = target tissue can be brain and spinal cord enterotoxic (GI), hemotoxic (blood), virus obligate intracellular parasites that need host for metabolism and reproduction causes cells to proliferate rapidly and randomly insert their genome into host cell http://farm6.staticflickr.com/5058/5539701673_f6359c379d.jpg latency chronic viral infection of dormancy = causes minimal damage but when immunocomprimised or stress triggers replication fungi common resident microbes that inhabit skin surface or mucous membranes ... kept in line by intact skin, inflammatory and immune cells EX = yeast infection yeasts unicellular form of fungi molds multicellular forms of fungi pseudohyphae yeast that reproduce and form an elongated chain http://farm6.staticflickr.com/5253/5494227622_62be2c98f3.jpg hyphae mold colonies that have tubules that branch http://farm4.staticflickr.com/3562/3338133989_bd54ccc9ba.jpg mycelium clusters of hyphae http://farm5.staticflickr.com/4113/5212591022_d2686e036b.jpg obligate parasites need host to live facultative parasites can live independently protozoa somw are parasites ... transmitted through sexual contact, foood , water, or vector = deprive host cells of nutrition causing tissue destruction EX = MALARIA, TRICHOMONAS VAGINALIS direct contact passsed to susceptible pperson when contacted with infected skin, mucus membranes, orr body fluid ... touching surface that iis contaminated with pathogen droplet spread spread in respiratory secretions of infected person = cough, sneeze, or breath person becomes infected if droplet enters eyes, nose or mouth directly or via contaminated hands indirect transmission occurs when organism is spread from infected person to suusceptible person via intermediary or go between via the air = airborne via an insect = vector phases of acute infection exposure incubation prodrome clinical illness covalescense exposure pathogen enters host through contact incubation extends from exposure to onset of symptoms and signs ... doessn't know their sick transmission to others is greatest prodrome onset of vague, nonspecific signs ex = fatigue, weakness clinical illness full signs and symptoms of specific disease septicemia occurs when micrrooorganisms gain acccess to the blood and circulate throughout the body chronic infection infections lasting from several weeks to years ... important to tell patiennts to complete courses of antibiotics ... local manifestations of infection heat, pain,, edema, rednesss, lymph nodee enlargemennt and pain, purulent exudate systemic manifestations of infection feever, weakness, heaadacche, malaise, anorexia, nausea treatments of infection antibiotics, antiifungals, antivirals, symptom reduction antibiotics inhibit bacterial cell wall synthesis and disable protein synthesis antivirals limited success b/c virus employs the host thus destroying the host cell antifungals bind to fungal wall cell increasingg permeability herpes diagnosis from vesicles or ulcers or serological tests: treatment = antivirals (orallly, IV, topicaally) can shorten course and reduce severity but not eradicate; cold compress and pain relievers Complications = spread from mother to infant viaa lesions on mother's genital tract - should deliver cesarean chlamydia most common STD ... 3-4 mill new cases yr. ... simillar to gonorrrhea Women: cervicitis and urethritis - can cause steriltiy Men: non gonoococcal urethritis - uretheral inflammation with frequency and burning on urination - can cause epididymitis condylomas anal or genital warts influenza patho=viral infection of the epithelial ceells of airway; transmmitteed via droplet; infected epithelial cell necrosis impairs cillia, mucous and antibodies leading to bacterial pneumonia. clinical manifestations=cough, sore throat, nasal congestion oor drainage, chills, fever, body aches, headache treatment=symptom related, hydraation, nutrition, vacciinations