Principles of Disease and Epidemiology Ch 14

Diseases and US P athogen : 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?

Normal Microbiota In some cases it is normal for microbes to be growing.

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.

Normal Microbiota on the Human Body Table 14.1

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.

Nose and throat S. aureus S. epidermides Streptoccoccus pneumoniae Haemophilus Neisseria

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.

Some diseases can only occur in one organism so we cannot run the full Koch’s postulates. Why?

Disease classification and codification Vocab Measurements Recognition and patterns

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 diseaseSymptoms develop rapidly Chronic diseaseDisease develops slowly Subacute diseaseSymptoms between acute and chronic Latent diseaseDisease 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

The Stages of a Disease Figure 14.5

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

Figure 14.6a & 8

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

Nosocomial Infections Table 14.5 ANIMATION Nosocomial Infections: Overview

Percentage of Total Infections Percentage Resistant to Antibiotics Coagulase- negative staphylococci 25%89% S. aureus16%80% Enterococcus10%29% Gram-negative rods 23%5-32% C. difficile13%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

Control of Nosocomial Aseptic techniques –Hand washing (40% compliance) Infection control staff

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) 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)

The study of where and when diseases occur Epidemiology Figure 14.11

New fields of Biological study Biological crimes? ASM paper

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

How do you prevent this from happening?