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Micro-TEST #1-Lecture 4
Lecture 4
73
Microbiology
Graduate
09/14/2009

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Term
Infection
Definition
a condition in which pathogenic microbes penetrate host defenses, enter tissues and multiply.
Term
Disease
Definition
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
Term
True pathogens
Definition
capable of causing disease in healthy persons with normal immune defenses
Influenza virus, plague bacillus, malarial protozoan
Term
Opportunistic pathogens
Definition
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
Term
Normal Flora
Definition
-of humans includes bacteria, fungi, and protozoa that live on the body without causing disease. Occasionally viruses and arthropods also.
Term
Where is normal flora found and how does it function?
Definition
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
Term
What part of the body has the most bacteria?
Definition
The large intestine has the most bacteria, with 30% of fecal volume being bacteria
Term
What parts of the body are microbe free and considered sterile?
Definition
Internal organs, tissues and fluids are microbe free and considered sterile.
Term
How do endogenous infections occur?
Definition
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
Term
Sites w/ normal flora
Definition
-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)
Term
Colonization of the Newborn
Definition
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
Term
Normal flora on skin
Definition
Staphylococcus, Micrococcus, others
Term
Normal flora of oral cavity & upper resp. tract
Definition
Streptococcus, Staphylococcus, Neisseria, Veillonella, Lactobacillus and Bacteroides
Term
Flora of the colon
Definition
Bacteroides, Clostridium, E Coli, Enterobacter, Citrobacter
Term
Flora of genital tract
Definition
Lactobacillus, Streptococcus, Corynebacterium, Escherichia
Term
Flora of urinary tract
Definition
Staphylococcus, Streptococcus in only the very distal portions
Term
Most of the intestinal bacteria are
Definition
-anaerobic
-bacteroides, clostridium, fusobacterium, bidifobacterium
Term
Coliforms
Definition
E. coli, Enterobacter, Citrobacter
Term
Flora in nasal area
Definition
Staph aureus
Term
Flora in nasopharynx distal to soft palate
Definition
Neisseria spp
Term
Flora in lower pharynx
Definition
Streptoccocus & Haemophilus
Term
Flora in lower pharynx
Definition
Streptoccocus & Haemophilus
Term
Flora in vagina
Definition
lactobacillus
Term
Flora of the ext. genitalia
Definition
-staph & strepOverview of in
Term
Overview of infection
Definition
Portal of entry->Adhesion->infecfion
->multiplication->infect target
->disease->portal of exit
Term
Exogenous portal of entry
Definition
originating from a source outside of the body; environment, other person, etc
Term
Endogenous portal of entry
Definition
already existing on or in the body; normal flora or latent infection
Term
Portals of entry via the skin
Definition
broken skin; abrasions, scrapes, punctures
Term
Portals of entry of GI tract
Definition
food, drinks, ingested
Term
Portals of entry of resp. tract
Definition
inhaled into upper respiratory
Term
Portals of entry in urogenital tract
Definition
sexually transmitted diseases
Term
Pathogens in Pregnancy & Birth
Definition
The placenta is an effective barrier against many pathogens but not against all.
Term
STORCH is an acronym for some pathogens that may cross the placenta.
Definition
S – syphilis
T – toxoplasmosis
O – other (hep B, HIV, chlamydia)
R – rubella
C – cytomegalovirus
H – herpesvirus
Term
Infectious Dose(ID)
Definition
-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
Term
Microbes with small IDs
Definition
1 rickettsial cell in Q fever
10 bacteria in tularemia
1,000 in gonorrhea
100,000,000 bacteria in cholera
Term
Mechanisms of Adhesion
Definition
-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
Term
Virulence Factors
Definition
Exoenzymes
Toxigenicity
Antiphagocytic factors
Term
Exoenzymes
Definition
the pathogen secretes enzymes to digest epithelial tissues & permit invasion of the pathogen
Term
Toxigenicity
Definition
capacity to produce toxins at the site of multiplication
Term
endotoxins
Definition
– toxin is released only after the host cell is lysed
Term
exotoxins
Definition
– proteins secreted by gram-positive and gram-negative bacteria
Term
Antiphagocytic factors
Definition
help them to kill or avoid phagocytes, include leukocidins and capsules
Term
Stages of Infection
Definition
Incubation period
Prodromal stage
Period of invasion
Convalescent period
Term
Incubation period
Definition
time from initial contact to the appearance of initial symptoms
Term
Prodromal stage
Definition
early vague symptoms
Term
Period of invasion
Definition
high rate of multiplication with greatest toxicity – fevers and specific symptoms
Term
Convalescent period
Definition
symptoms decline
Term
Patterns of Infection
Definition
Localized,Systemic, Focal
Term
Localized pattern of infection
Definition
Microbes enter body and remain confined to a specific tissue
Term
Systemic pattern of infection
Definition
infection spreads to several sites and tissue flouids usually in the bloodstream
Term
Focal pattern of infection
Definition
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)
Term
Mixed infection
Definition
– several microbes grow simultaneously at the infection site
Term
Primary infection
Definition
– initial infection
Term
Secondary infection
Definition
– another infection by a different microbe – may be in a different area
Term
Signs of disease
Definition
objective evidence of disease as noted by an observer
Term
Symptons of disease
Definition
subjective evidence of disease as sensed by the patient
Term
Sequelae
Definition
– long-term or permanent damage to tissues or organs
Term
Portals of Exit
Definition
Respiratory droplets and saliva
Skin scales
Fecal exit
Urogenital tract
Removal of blood and blood products
Term
Reservoirs of Infection
Definition
Primary habitat in the natural world from which a pathogen originates
Term
Living reservoirs of infection
Definition
-may or may not have symptoms
-Asymptomatic carriers
-Passive carriers
-Vectors – live animal that transmits infectious disease
Term
Nonliving reservoirs of infection
Definition
soil, and water
Term
Direct contact patterns of transmission
Definition
from one person to another by skin to skin contact, sneezing, coughing, sexual activity or bites of infected vectors
Term
Indirect contact
Definition
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)
Term
Nosocomial Infections
Definition
-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
Term
Most common organisms involved in nocosomal infections
Definition
gram-negative intestinal flora, E. coli, Klebsiella, Pseudomonas, Staphylococcus
Term
Prevalence
Definition
– total number of existing cases with respect to the entire population usually represented by a percentage of the population
Term
Incidence
Definition
measures the number of new cases over a certain time period, as compared with the general healthy population – (usually reported per 100,000 persons)
Term
Mortality rate
Definition
the total number of deaths in a population due to a certain disease
Term
Morbidity rate
Definition
number of people afflicted with a certain disease
Term
Endemic
Definition
disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale
Term
Sporadic
Definition
when occasional cases are reported at irregular intervals
Term
Epidemic
Definition
when prevalence of a disease is increasing beyond what is expected
Term
Pandemic
Definition
epidemic across continents
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