Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE Chapter 14 Principles of Disease and Epidemiology

PathologyStudy of disease Diseasein a state of not being healthy, change from health Pathogensdisease causing organisms EtiologyStudy of the cause of a disease PathogenesisDevelopment of disease InfectionColonization or invasion of pathogens, may be microbes in the wrong place (E. coli in the urinary tract)

Normal Flora - the normal bacteria in you and on you –You have eucaryotic cells and prokaryotic cells –Within hours of life you are colonized by normal flora (microbiota). Breast feeding versus bottle - different organisms Transient microbiota may be present for days, weeks, or months Microbial antagonism –Normal microbiota overwhelm pathogens - no place for them to colonize Intestines and vagina - excessive antibiotics disrupts balance –Vagina normally pH ~ 4 with Lactobacillus spp without can lead to Candida infections Symbiosis is the relationship between normal microbiota and the host Normal Microbiota (Flora) and the Host

In commensalism, one organism is benefited and the other is unaffected. In mutualism, both organisms benefit. Be able to give a few examples of mutualistic bacteria In parasitism, one organism is benefited at the expense of the other. Some normal microbiota are opportunistic pathogens. –E. coli and urinary tract –Pneumocystis carinii and respiratory system –Streptococcus pneumoniae and pneumonia Normal Microbiota and the Host:

Figure 14.2 Locations of normal microbiota on and in the human body Normal Microbiota and the Host:

Microbial antagonism is competition between microbes. Normal microbiota protect the host by: –occupying niches that pathogens might occupy –producing acids –producing bacteriocins Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect. –Lactobacillus spp Normal Microbiota and the Host:

Koch's Postulates are used to prove the cause of an infectious disease. Koch’s Postulates Figure

Koch's Postulates are used to prove the cause of an infectious disease. Problems with Koch’s Postulates: Not all diseases have bacterial etiologies –Genetic –Degenerative –Congenital Exceptions –Not culturable Treponema / Rickettsia / Chlamydia / viruses –Some pathogens cause many different diseases Koch’s Postulates Figure

Classifying Infectious Diseases SymptomA change in body function that is felt by a patient as a result of disease SignA change in a body that can be measured or observed as a result of disease. SyndromeA specific group of signs and symptoms that accompany a disease.

Classifying Infectious Diseases Diseases may be grouped by how spread Communicable diseaseA disease that is spread from one host to another. Contagious diseaseA disease that is easily spread from one host to another. Noncommunicable diseaseA disease that is not transmitted from one host to another. Example: Clostridium tetani

IncidenceFraction of a population that contracts a disease during a specific time. PrevalenceFraction of a population having a specific disease at a given time. Sporadic diseaseDisease that occurs occasionally in a population. Endemic diseaseDisease constantly present in a population. Epidemic diseaseDisease acquired by many hosts in a given area in a short time. Pandemic diseaseWorldwide epidemic. Herd immunityImmunity in most of a population. By occurrence of Disease

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 Shingles By Severity or Duration of a Disease

Local infectionPathogens limited to a small area of the body Systemic infectionAn infection throughout the body Focal infectionSystemic infection that began as a local infection BacteremiaBacteria in the blood SepticemiaGrowth of bacteria in the blood By Extent of Host Involvement

ToxemiaToxins in the blood ViremiaViruses in the blood Primary infectionAcute infection that causes the initial illness Secondary infectionOpportunistic infection after a primary (predisposing) infection Pneumocystis pneumonia and AIDS Subclinical diseaseNo noticeable signs or symptoms (inapparent infection) Hepatitis / Typhoid mary / Polio Extent of Host Involvement

Make the body more susceptible to disease –Short urethra in females –Inherited traits such as the sickle-cell gene –Climate and weather –Fatigue and Stress –Age –Lifestyle –Chemotherapy –Gender Predisposing Factors

Development of Disease Stages of Disease Incubation infection up to first symptoms may or may not be variable Prodromalshort period of early mild symptoms -- malaise Period of Illness overt signs -- fever and chills, swollen lymph nodes, GI disturbance increase in WBC’s Period of Decline signs and symptoms subside - susceptible to 2˚ infections Period of Convalescence regain strength and recovery BUT maybe reservoir

The Stages of a Disease Figure 14.5

Reservoirs of infection are continual sources of infection. –Human — AIDS, gonorrhea Carriers may have inapparent infections or latent diseases. Carriers may be in pre-symptom stage or recovery of a disease - no symptoms –Animal — Rabies, Lyme disease Some zoonoses may be transmitted to humans –Plague / psittacosis / swine flu / bird flu –Nonliving — Botulism, tetanus Soil Water - rivers, lakes, snow, oceans and laundry water Reservoirs of Infection

Three main routes –Contact - Direct or indirect –Vehicles - inanimate objects - e.g. food or drugs –Vectors - arthropods Contact –DirectRequires close association between infected and susceptible host –IndirectSpread by fomites (inanimate objects) glass, toothbrush or clothing –DropletTransmission via airborne droplets Transmission of Disease

Figure 14.6a & 8

Vehicle Transmission by an inanimate reservoir (food, water) Shigella, cholera, airborne on dust aerosol >3’, tapeworm Staphylococci, Streptococci, tuberculosis, fungal spores --histoplasmosis, coccidiodomycosis VectorsArthropods, especially fleas, ticks, and mosquitoes –MechanicalArthropod carries pathogen on feet –Biological Pathogen reproduces in vector and bites host. Dengue fever, Yellow fever, Malaria, encephalitis, plague, Lyme disease RMSF Transmission of Disease

Figure 14.6b, c

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 Hospital acquired % acquire >20,000 per year die why? a) microbes in environment -- (lots of sick people) b) already sick or wounded -- compromised host c) close to people - chain of transmission Also resistant strains - E. coli, Pseudomonas, enterics like Serratia Control by aseptic techniques Antibiotic abuse

Figure Relative frequency of nosocomial infections

Common Causes of Nosocomial Infections Percentage of nosocomial infections Percentage resistant to antibiotics Gram + cocci Streptoccous and Staphylococcus 34%28%-87% Gram – rods Enterics and Pseduomonas 32%3-34% Clostridium difficile17% Fungi10%

Diseases that are new, increasing in incidence, or showing a potential to increase in the near future. Contributing factors: –Evolution of new strains V. cholerae O139 –Inappropriate use of antibiotics and pesticides Antibiotic resistant strains –Changes in weather patterns Hantavirus –Spread of human populations and travel Emerging Infectious Diseases

Contributing factors: –Modern transportation West Nile virus –Ecological disaster, war, expanding human settlement Coccidioidomycosis –Animal control measures Lyme disease –Public Health failure Diphtheria Emerging Infectious Diseases

The study of where and when diseases occur Epidemiology Figure 14.11

Epidemiology John Snow Mapped the occurrence of cholera in London Ignaz Semmelweis Showed the hand washing decreased the incidence of puerperal fever Florence Nightingale1858Showed that improved sanitation decreased the incidence of epidemic typhus

DescriptiveCollection and analysis of data regarding occurrence of disease Snow AnalyticalComparison of a diseased group and a healthy group Nightingale ExperimentalStudy of a disease using controlled experiments Semmelweis Case reportingHealth care workers report specified disease to local, state, and national offices Nationally Notifiable Diseases Physicians are required to report occurrence

Table 14.7

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)