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Diseases and US
• Pathogen : a disease causing microbial growth or toxin.
• Disease: an abnormality in which the body or part is not properly adjusted. The body part is overcome by the microbe– Change in the state of health
• Infection: is the invasion and growth of a pathogen in the body
More words
• Host: Is an organism that shelters and supports the growth of pathogens.
• Pathology: scientific study of disease
• Etiology: cause of a disease
• Pathogenesis: development of disease
• Is this a type of symbiosis?
• Most mammals germ free in utero, are colonized after birth.
• Microbes that establish permanent colonies inside or on outside of the body without causing disease are called normal microbiota.
• Transient microbiota are microbes that are stable for a time then disappear.
Symbiosis
• With normal microbiota, usually both species benefit from this arrangement.
• Normal microbiota can prevent infections, may make necessary vitamins in return for nutrients form the host. (is called…..
• Opportunistic microbes may cause disease under certain instances.
• Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect.
Skin
• Propionibacterium acnes
• Staphylococcus epidermidis
• Staphylococcus aureus
• Candida spp
• Most microbes are transient on skin.
• Why?
Eyes
• Basically the same as that found on the skin.
• Eyes have lysozyme, few nutrients, washing by tears.
Mouth
• Streptoccoccus• Lactobacillus• Actinomyces• Bacteroides• Fusobacterium• Treponema• Cornebacterium• Candida• Over 200 species
• Idea environment• Is a diverse
environment.
• How do we know what lives in the mouth?
Large intestine• Bacteroides• Fusobacterium• Lactobacillus• Enterococcus• Escherichia• Enterobacter• Proteus• Klebsiella• Shigella• Candida
• Is essentially a chemostat
• Has a large resident microbiota
Urogenital system
• Staphylococcus epidermidis
• Enterococcus• Lactobacillus• Pseudomonas• Klebsiella• Proteius• In urethra
• Lactobacilli• Streptococcus• Staphylococcus• Bacteroides• Clostridium• Candida albicans• Trichomonas
vaginalis• in vagina is acidic
Koch’s postulates
• Same pathogen must be present in every case of the disease
• Pathogen must be isolated in pure culture
• Pathogen isolated from pure culture must cause the same disease in a healthy, susceptible laboratory animal.
• Pathogen must be isolated from this animal
Exceptions to Koch’s postulates
• Are modified to establish etiologies of diseases caused by viruses and fastidious bacteria, which cannot be grown on defined media.
• Some diseases are caused by a variety of microbes.
• Some diseases such as S. pyogenes can cause several different diseases.
• Symptoms- change in body function• Diagnosis- identification• Sign- a measurable change• Syndrome- a specific group of symptoms
or signs that always accompanies a specific disease.
• Communicable diseases- transmitted directly or indirectly from one host to another.
• Contagious disease- is easily spread from one person to another
• No communicable diseases- are caused by microbes that normally grow outside the body and are not transmitted from one host to another– Clostridium tetani
Where, how bad and how much. Words to describe ID
• Incidence- number of people contracting the disease
• Prevalence- number of cases at a particular time
• Frequency- is in terms of sporadic, endemic, epidemic and pandemic
• Acute, chronic, subacute and latent• Herd immunity- is the presence of
immunity in most of the population
• Local infection- affects a small area of the body
• Systemic infection- spread throughout the body– Bacteremia- bacteria in the blood– Septicemia- bacteria multiply in blood
• Secondary infections- occur after a host is weakened from a primary infection
• Subclinical- cannot be measured
• Acute disease Symptoms develop rapidly• Chronic disease Disease develops
slowly• Subacute disease Symptoms between acute
and chronic• Latent disease Disease with a period of no
symptoms when the patient is inactive
Severity or Duration of a Disease
Recognition and patterns of disease
• Predisposing factors make the body more susceptible to disease they include– Gender– Climate– Age– Fatigue– Nutrition– Lifestyle– Drug treatments
What happens when a disease does occur?
• Incubation period- is the time between the initial infection and the first appearance of signs and symptoms
• Prodromal- period is the first mild signs and symptoms
• Illness- is when the disease is at its height
• Decline- signs and symptoms decline
• Convalescence- time until the body returns to predisease state
Spreading of Infection
• Reservoir of infection – provides pathogen with conditions for survival– Human – carriers, asymptomatic or latent– Animal- zoonoses various routes– Nonliving Reservoirs – water, fertilizer ect
Transmission of Disease
• Contact transmission– Direct person to person transmission
• Indirect contact transmission– Fomite a nonliving transfer (1 meter, soiled
goods)
• Droplet transmission over short distances
• Vehicle transmission (water, food, air)
• Vectors (mechanical or biological)
Transmission of Disease
Portals of entry and Exit
• Pathogens have preferred portals of entry and exit.
• Most common portals– Respiratory tract– Gastrointestinal tract– Urogenital tract– Blood to blood
• Vehicle Transmission by an inanimate reservoir (food, water)
• Vectors Arthropods, especially fleas, ticks, and mosquitoes
• Mechanical Arthropod carries pathogen on feet
• Biological Pathogen reproduces in vector
Transmission of Disease
Nosocomial (Hospital-acquired) infections
• 5-15% get infections while in the hospital.
• Microbes in hospital
• Chain of transmission
• Compromised host
• Is a hospital the best place to be if you are sick?
Figure 14.7, 9
• Are acquired as a result of a hospital stay
• 5-15% of all hospital patients acquire nosocomial infections
Nosocomial (Hospital-Acquired) Infections
Percentage of Total
Infections
Percentage Resistant to Antibiotics
Coagulase-negative staphylococci
25% 89%
S. aureus 16% 80%
Enterococcus 10% 29%
Gram-negative rods
23% 5-32%
C. difficile 13% None
Common Causes of Nosocomial Infections
MRSA
• USA100: 92% of health care strains
• USA300: 89% of community-acquired strains
Clinical Focus, p. 422
Which Procedure Increases the Likelihood of Infection Most?
Clinical Focus, p. 422
ANIMATION Nosocomial Infections: Prevention
Emerging Infectious diseases
• Ones that are new or changing• Global warming• Global transportation• Antibiotics• Breakdown in social order• Governance problems• Pesticides• Lack of vaccination• Lack of reporting
Epidemiology
• Study of transmission incidence and frequency of disease.
• Data are collected and analyzed in descriptive epidemiology
• Analytical epidemiology- infected comp to uninfected
• Controlled experiments• Case reporting• CDC reporting
• CDC (Centers for Disease Control and Prevention) main source of epidemiologic info in US
• Publishes Morbidity and Mortality Weekly Report, reports incidence and deaths.
• Collects and analyzes epidemiological information in the U.S.
• Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov
Morbidity: incidence of a specific notifiable disease
Mortality: deaths from notifiable diseases
Morbidity rate = number of people affected/total population in a given time period
Mortality rate - number of deaths from a disease/total population in a given time
Centers for Disease Control and Prevention (CDC)
Nosocomial outbreak (page 445)
• 7 year period 361 patients developed bacteremia
• Burkholderia cepacia identified (same strain)
• Infection within 36hr of IV
• Disappears hrs after IV removed
• Cleaning insertion site
• Iodine is negative
Continued
• Not found in povidone-iodine
• In alcohol
• Alcohol purchase as 90% and diluted in pharmacy.
• Used the same 100l container
• Used the same tap water
• Tap water contaminated