Micro-TEST #1-Lecture 4 – Flashcards
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| Infection |
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| a condition in which pathogenic microbes penetrate host defenses, enter tissues and multiply. |
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| Disease |
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| disruption of a tissue or organ caused by microbes or their products such as toxins and enzymes Disease occurs when pathogenic cells enter the body through a specific route, grow and damage or disrupt normal tissue functions |
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| True pathogens |
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| capable of causing disease in healthy persons with normal immune defenses Influenza virus, plague bacillus, malarial protozoan |
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| Opportunistic pathogens |
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| cause disease when the host’s defenses are compromised or when they grow in part of the body that is not natural to them ie. Pseudomonas sp & Candida albicans |
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| Normal Flora |
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| -of humans includes bacteria, fungi, and protozoa that live on the body without causing disease. Occasionally viruses and arthropods also. |
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| Where is normal flora found and how does it function? |
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| Found in the GI tract, skin, respiratory tract and other areas exposed to the environment. Generally beneficial to humans. Bacterial flora benefit host by preventing overgrowth of harmful microbes |
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| What part of the body has the most bacteria? |
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| The large intestine has the most bacteria, with 30% of fecal volume being bacteria |
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| What parts of the body are microbe free and considered sterile? |
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| Internal organs, tissues and fluids are microbe free and considered sterile. |
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| How do endogenous infections occur? |
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| cEndogenous infections occur when normal flora is introduced to a site that is normally sterile – i.e. E coli enters the urinary tract causing a urinary tract infection |
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| Sites w/ normal flora |
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| -Skin & its contiguous mucous membranes -upper resp. tract -GI tract -outer opening of urethra -external genitalia -vagina -Ext. ear canal -Ext. eye (lids,lash follicles) |
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| Colonization of the Newborn |
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| Starts with the rupture of the membranes during delivery and flora of the birth canal. Continues with contact with family members, the environment, food and health care personnel. Breast fed babies have different normal flora than bottle fed babies |
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| Normal flora on skin |
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| Staphylococcus, Micrococcus, others |
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| Normal flora of oral cavity & upper resp. tract |
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| Streptococcus, Staphylococcus, Neisseria, Veillonella, Lactobacillus and Bacteroides |
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| Flora of the colon |
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| Bacteroides, Clostridium, E Coli, Enterobacter, Citrobacter |
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| Flora of genital tract |
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| Lactobacillus, Streptococcus, Corynebacterium, Escherichia |
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| Flora of urinary tract |
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| Staphylococcus, Streptococcus in only the very distal portions |
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| Most of the intestinal bacteria are |
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| -anaerobic -bacteroides, clostridium, fusobacterium, bidifobacterium |
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| Coliforms |
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| E. coli, Enterobacter, Citrobacter |
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| Flora in nasal area |
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| Staph aureus |
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| Flora in nasopharynx distal to soft palate |
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| Neisseria spp |
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| Flora in lower pharynx |
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| Streptoccocus & Haemophilus |
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| Flora in lower pharynx |
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| Streptoccocus & Haemophilus |
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| Flora in vagina |
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| lactobacillus |
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| Flora of the ext. genitalia |
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| -staph & strepOverview of in |
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| Overview of infection |
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| Portal of entry->Adhesion->infecfion ->multiplication->infect target ->disease->portal of exit |
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| Exogenous portal of entry |
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| originating from a source outside of the body; environment, other person, etc |
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| Endogenous portal of entry |
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| already existing on or in the body; normal flora or latent infection |
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| Portals of entry via the skin |
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| broken skin; abrasions, scrapes, punctures |
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| Portals of entry of GI tract |
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| food, drinks, ingested |
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| Portals of entry of resp. tract |
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| inhaled into upper respiratory |
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| Portals of entry in urogenital tract |
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| sexually transmitted diseases |
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| Pathogens in Pregnancy & Birth |
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| The placenta is an effective barrier against many pathogens but not against all. |
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| STORCH is an acronym for some pathogens that may cross the placenta. |
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| S – syphilis T – toxoplasmosis O – other (hep B, HIV, chlamydia) R – rubella C – cytomegalovirus H – herpesvirus |
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| Infectious Dose(ID) |
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| -Minimum number of microbes required for infection to proceed -Microbes with small IDs have greater virulence -Inoculum of less than the infectious dose will usually not result in infection |
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| Microbes with small IDs |
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| 1 rickettsial cell in Q fever 10 bacteria in tularemia 1,000 in gonorrhea 100,000,000 bacteria in cholera |
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| Mechanisms of Adhesion |
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| -pathogen enters the body it must bind to the host, penetrate it barriers and become established in the tissues. -limited to only those cells to which it can bind. Examples Fimbrae Flagella Adhesive slimes or capsules Cilia Suckers, hooks & barbs |
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| Virulence Factors |
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| Exoenzymes Toxigenicity Antiphagocytic factors |
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| Exoenzymes |
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| the pathogen secretes enzymes to digest epithelial tissues & permit invasion of the pathogen |
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| Toxigenicity |
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| capacity to produce toxins at the site of multiplication |
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| endotoxins |
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| – toxin is released only after the host cell is lysed |
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| exotoxins |
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| – proteins secreted by gram-positive and gram-negative bacteria |
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| Antiphagocytic factors |
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| help them to kill or avoid phagocytes, include leukocidins and capsules |
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| Stages of Infection |
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| Incubation period Prodromal stage Period of invasion Convalescent period |
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| Incubation period |
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| time from initial contact to the appearance of initial symptoms |
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| Prodromal stage |
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| early vague symptoms |
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| Period of invasion |
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| high rate of multiplication with greatest toxicity – fevers and specific symptoms |
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| Convalescent period |
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| symptoms decline |
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| Patterns of Infection |
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| Localized,Systemic, Focal |
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| Localized pattern of infection |
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| Microbes enter body and remain confined to a specific tissue |
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| Systemic pattern of infection |
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| infection spreads to several sites and tissue flouids usually in the bloodstream |
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| Focal pattern of infection |
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| when infectious agent give off toxins from a local infection and the toxin is carried to other tissues (strep group A causes infection in the throat + gives off a toxin that causes a rash) |
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| Mixed infection |
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| – several microbes grow simultaneously at the infection site |
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| Primary infection |
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| – initial infection |
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| Secondary infection |
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| – another infection by a different microbe – may be in a different area |
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| Signs of disease |
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| objective evidence of disease as noted by an observer |
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| Symptons of disease |
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| subjective evidence of disease as sensed by the patient |
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| Sequelae |
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| – long-term or permanent damage to tissues or organs |
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| Portals of Exit |
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| Respiratory droplets and saliva Skin scales Fecal exit Urogenital tract Removal of blood and blood products |
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| Reservoirs of Infection |
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| Primary habitat in the natural world from which a pathogen originates |
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| Living reservoirs of infection |
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| -may or may not have symptoms -Asymptomatic carriers -Passive carriers -Vectors – live animal that transmits infectious disease |
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| Nonliving reservoirs of infection |
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| soil, and water |
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| Direct contact patterns of transmission |
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| from one person to another by skin to skin contact, sneezing, coughing, sexual activity or bites of infected vectors |
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| Indirect contact |
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| Vehicle – inanimate material, food, water, biological products, fomites (doorknob, telephone etc) Airborne – droplet nuclei or aerosols in the air not directly from person to person (closed in space) |
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| Nosocomial Infections |
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| -Diseases that are acquired during a hospital stay – incidence can be as high as 20% of all admitted patients. Avg. is 5% -Most commonly involve urinary tract, respiratory tract, & surgical incisions |
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| Most common organisms involved in nocosomal infections |
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| gram-negative intestinal flora, E. coli, Klebsiella, Pseudomonas, Staphylococcus |
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| Prevalence |
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| – total number of existing cases with respect to the entire population usually represented by a percentage of the population |
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| Incidence |
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| measures the number of new cases over a certain time period, as compared with the general healthy population – (usually reported per 100,000 persons) |
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| Mortality rate |
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| the total number of deaths in a population due to a certain disease |
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| Morbidity rate |
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| number of people afflicted with a certain disease |
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| Endemic |
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| disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale |
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| Sporadic |
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| when occasional cases are reported at irregular intervals |
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| Epidemic |
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| when prevalence of a disease is increasing beyond what is expected |
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| Pandemic |
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| epidemic across continents |
