normal flora of an organism are permanent residents that do not cause infection. An example of these would be the organisms that normally live on your skin. They actually keep harmful organisms from being able to establish residence
When and infection results in any change from a state of health. When all or part of the body is incapable of performing its normal functions
One species is harmed and it is difficult to see how other is benefited.
Example: S. aureus and Penicillium mold. Mold releases Penicillin to kill S. aureus. Benefit to mold hard to see.
One organism benefits and the other is not harmed.
Ex: Streptococcus viridans lives in your mouth. It does no harm but living here is beneficial to the bacterium because it grows well in this area.
Two species live together and both benefit.
Ex. The large intestine contains E. coli that synthesizes vitamin K and B. They are then absorbed in by the blood stream for cells. In exchange, the intestine provides nutrients for E. coli's survival
The organism lives in the host. Parasite benefits but host may be harmed. A successful parasite will not kill its host.
Ordinarily don't cause disease in their normal habitat but may do so in a abnormal environment. Ex. Cut
This series of steps is used by microbiologists to determine the etiology or causative agent of a disease.
1. The same pathogen must be present in every case of the disease
2. The pathogen must be isolated from the diseased host and grown in pure culture
3. The pathogen from the pure culture must cause the disease when it is inoculated
4. The pathogens must be isolated from the inoculated animal and must be shown to be
Koch's Postulates Procedure
1. Microorganisms are isolated from a diseased or dead animal
2. Microorganisms are grown in a culture and identified
3. Microorganisms are injected into a healthy animal
4. Disease is reproduced in a laboratory animal
5. Microorganisms are isolated from this animal and grown in a culture then identified.
A change in a body that can be measured or observed as a result of disease. Ex. Swelling, fever
Any disease that spreads from one host to another directly or indirectly. Ex. Chickenpox, measles, genital herpes, typhoid fever
Diseases that are spread easily spread from one person to another (type of communicable disease)
A disease not spread from one person to another. Ex. Tetanus, Clostridium tetani produces disease only when it is introduced into the body via wounds
Incidence of a Disease
The proportion of the population affected by a disease at a specific point in time. Indicator of spread.
Prevalence of a Disease
The number of people in a population who develop a disease at a specific time, regardless of when it first appeared. Both old and new cases. Indicator of how seriously and how long a disease affects a population.
Many people in a given area acquiring a a certain disease in a relatively short period of time. Ex. Influenza
The causative remains inactive for a long time and reappears. Ex: Varicella zoster virus causes shingles which is a reactivated chicken pox infection.
A disease the is intermediate between acute and chronic. Ex. Sclerosing panencephalitis, rare brain disease
A toxic inflammatory condition arising from the spread of microbes, especially bacteria, from a focus infection.
Ex. Septicemia, also called blood poisoning is a systemic infection arising from the multiplication of pathogens in the blood.
Human resevoirs-people with disease Ex. aiDS, diphtheria, typhoid fever, hepatitis, gonorrhea, amebic dysentery, and streptococcal infections
Transmission of Disease
1. Direct Contact
2. Indirect contact - fomites (inanimate objects)
3. Droplet Transmission
4. Vehicle transmission
6. Arthropod vectors
Make one more susceptible or resistant. For example, the genetic disease sickle cell anemia gives resistance to malaria.
The development of a disease follows a definite pattern:
-period of illness
>ends in death or life<
-period of decline
>can get a secondary infection<
-period of convalescence
Are acquired as a result of a hospital stay. Patients on antimicrobial therapy or immunosuppressants are most susceptible. Five to fifteen percent of all hospital patients acquire them.
Interaction of three factors leads to nosocomial infections:
(1.)Presence of microorganisms in the hospital environment.
(2.) A weakened or compromised host.
(3.) A chain of transmission in the hospital. One of the three is usually not enough to pose a significant risk.
Emerging Infectious Diseases
Emerging diseases are diseases that are new, increasing in incidence, or showing a potential to increase in the near future.
Contributing factors include:
-Evolution of new strains
-Inappropriate use of antibiotics and pesticides.
Emerging diseases may result from
-Changes in weather patterns: Hantavirus
-Modern Transportation: West Nile virus
-Ecological disaster, war, and expanding human settlement: Coccidioidomycosis
-Animal control measures: Lyme disease
-Public Health failure: Diphtheria
All members of the seven families for whom Mary Mallon prepared meals developed typhoid fever. Mary did not get sick. This is an example of __________.
What is the difference between normal and transient microbiota?
Normal microbiota are permanently present.
Koch's postulates are a set of guidelines to follow if you want to __________.
prove that a specific infectious disease is caused by a specific microorganism
On October 29, Barbara participated in a study group for her microbiology class. On November 1, Barbara had a "scratchy throat" when she swallowed. On November 2, Barbara had a headache, runny nose, and watery eyes. She was fully recovered on November 7. During which time was Barbara in the prodromal period?
John Snow analyzed information about cholera victims, including where the victims lived and where they got water. This is an example of __________.
Florence Nightingale compared disease rates and other statistics for soldiers versus civilian populations. This is an example of __________.
he fungus Coccidioides immitis is found in the soil. Humans contract coccidioidomycosis by inhaling fungal spores. Which of these descriptions applies to the role of soil in transmission of coccidioidomycosis?
Soil is the reservoir.
Alfalfa sprouts were responsible for transmitting Salmonella to 32 people in four states. This is an example of __________.
Two patients developed endophthalmitis within 24 hours after corneal transplant surgery. Streptococcus pneumoniae was isolated from conjunctival swabs of the affected eyes of both patients and from the supply of packing that was used to cover the eyes after surgery. This is an example of __________.
a nosocomial infection
On October 29, Barbara participated in a study group for her microbiology class; one of her classmates had a cold. On November 1, Barbara had a "scratchy throat" when she swallowed. On November 2, Barbara had a headache, runny nose, and watery eyes. She was fully recovered on November 7. Identify the incubation period for this infection
October 29 to November 1
One that is caused by an opportunistic pathogen after the primary infection has weakened the body's defenses. Seconadary infection of the skin and respiratory tract sometimes more dangerous than primary infection.
EX. Pneumocystis pneumonia as consequence of AIDS
EX. Streptococcal bronchopneumonia following influenza
Makes the body more susceptible to a disease and may alter the course of the disease.
ex. Gender, genetic background, climate and weather, inadequate nutrition, fatigue, age, environment, habits, lifestyle, occupation, preexisting illness, chemotherapy, and emotional disturbances.
First stage in the development of a disease. The interval between the initial infection and the first appearance of any signs or symptoms. an be the same or variable depending on the specific microorganism.
Second stage in the development of a disease. A relatively short period that follows the period of incubation in some diseases. Early mild symptoms
Period of Illness
Third stage in the development of a disease. When the disease is most severe. Overt signs and symptoms of disease. Dies in this stage if disease is not successfully overcome.
Period of Decline
Third stage in the development of a disease. The signs and symptoms subside. Lasts less than 24 hours to a few days. Patient is vulnerableto secondary infections at this time.
Period of Convalescense
Fourth stage in the development of a disease. Regains strength and returns to normal state. Can spread infection in all four stages.
Health Care-associated infection (HAI)
CDC estimates 5-15% of all hospital patients acquire some type of nosocomial infection. Result from
1. Microorganisms in the hospital environment
2. weakened status of the host (nosocomial infections do not cause disease in healthy people)
3. chain of transmission in the hospital
Some microorganisms in the hospital become resistant to antimicrobial drugs
A host whose resistance to infection is impaired by disease, therapy, or burns. Two principal conditions can compromise the host: broken skin or mucouse membranes, and a suppressed immune system.
Ex. urns, surgical wounds, injections, ventilators, intravenous therapy, urinary catheters
A type of White Blood Cell (T lymphocytes) that provide resistance to disease by killing pathogens directly, mobilizing phagocytes and other lymphocytes, and secretin chemicals that kill pathogens
White blood cells (B lymphocytes) that develop into antibody-producing cells, also protect against infection
Chain of transmission
The principal routs of transmission of nosocomial infections are
1. direct contact transmission hospital staff to patient and from patient to patient
2. indirect contact transmission through fomites and the hospital's ventilation system (humidifiers and respirators also give way to airborne transmission)
Control of Nosocomial Infections
CDC says hanwashing is the single most important means of preventing the spread of infection
emerging Infectious diseases (EIDs)
Ones that are new or changing, showing an increase in incidence in the recent past, or a potential to increase in the near future.
e. coli O157:H7 and avian influenza (H5N1)
These new strains may result from genetic recombination between organisms
widespread and unwarranted use of antibiotics and pesticides
encourages the growth of more resistant populations of microbes and the insects and ticks that carry them
global warming and changes in weather patterns
may increase the distribution and survival of reservoirs and vectors resulting in the introduction and dissemination of diseases such as malaria and hantavirus pulmonary syndrome
Causes Puerperal sepsis (chilbirth fever), a nosocomial infection that starts in the uterus as a result of childbirth or abortion
entails the collecting all the data that describe the occurrence of the disease under study. Includes information about the infected individuals and the place and period in which the disease occurred. Retrospective, looking back and backtracking to find the cuase and source of the disease.
Analyzes a particular disease to determine its probable cause. two ways:
1. case control method-studying two populations: one that has contracted the disease and one that has not
2. Cohort method- studying two populations: one that has had contact the disease and another that has not.
Begins with a hypothesis about a particular disease. ex. effectiveness of a drug. One group of people with a condition are split: one gets drug, other gets a placebo
a procedure that requires health care workers to report specific diseases to local, state, and national health officials
the rate of people affected by a disease in a given period of time in relation to the total population
the number of deaths resulting from a disease in a population in a given period of time in relation to the total population
Notifiable infectious diseases
diseases for which physicians are required by law to report cases to the us public Health service. 2011 total was 62 infectious diseases
microbial Antagagonism or competitive exclusion
the normal microbiota can benefit the host by preventing the overgrowth of harmful microorganisms. competition among microbes
Germ-free (gnotobiotic) animals often are more susceptible to infections and serious disease than are animals with a typical complement of normal microbiota. Based on this observation, which of the following would be an appropriate conclusion?
Normal microbiota stimulate the development of the immune system.
In a healthy human, resident microorganisms would be found in all of these areas except ________.
Health care professionals who fail to use aseptic techniques can cause ________.
In the human intestinal tract, E. coli produces vitamins beneficial to the host and can inhibit pathogen growth. In turn, the bacterium is supplied with nutrients and an environment for growth. This symbiotic relationship between E. coli and its host is an example of ________.
Which of the following is not an example of microbial antagonism (also known as competitive exclusion)?
microbes producing vitamins and growth factors that can be utilized by the host
Which of the following is not necessary to satisfy Koch's postulates?
The organism must cause disease through toxin production.
Following coronary artery bypass surgery, seven patients develop Rhodococcus bronchialis infections. Cultures of the operating rooms, Nurse A, and Nurse B are taken. R. bronchialis grows from the hand and nasal swabs of Nurse A. The patients' infections are an example of a/an ________.
Women who have a healthy population of Lactobacillus spp. as part of the normal vaginal microbiota are less likely to get yeast infections. Which of the following terms is used to explain this observation?
The occurrence of streptococcal bronchopneumonia in an individual recovering from influenza is an example of a/an ________.
Infections in which the pathogen is distributed throughout the body are referred to as "generalized infections" or ________.
Which of these events is an example of contact transmission?
A person drinks from a cup used by another individual
Which of these disease stages is most likely to be altered in length if the number of infecting organisms at the start of the infection is very high?
Any of these events may occur in diseases transmitted by vectors except ________.
In biological transmission, the vector multiplies in the human host
The morbidity rate is best defined as ________.
the number of individuals, relative to the population, affected by a particular disease in a period of time
Ingesting lactic acid bacteria to prevent colonization by intestinal pathogens such as Salmonella enterica during antibiotic therapy is an example of ________.
An example of descriptive epidemiology is ________.
John Snow's study of the London cholera outbreak in 1848-1849
an active process. the arthropod bites and infected person or animal and ingests some of the infected blood. the pathogens then reproduce in the vector.
Tetanus, which humans acquire from wounds that become infected with the soil microbe Clostridium tetani, is considered noncommunicable
Transmission of Plasmodium spp. (malaria) through a mosquito bite is an example of vehicle transmission.
Depending on the disease, individuals can be contagious during the incubation and prodromal periods as well as the periods of illness, decline, and convalescence.
Microorganisms that typically colonize a host without causing disease are referred to as the __________.
During the __________, a person recovers from a disease and the body returns to its pre-disease state
period of convalescence
__________ pathogens are those that do not cause disease in their normal habitat but may do so in a different environment
The protection from infection received when individuals susceptible to a particular disease live in a population where many individuals are immune is referred to as __________.
Live cultures of bacteria that can be ingested and are intended to produce a beneficial effect in humans are known as __________.
The fungus Coccidioides immitis is found in the soil. Humans contract coccidioidomycosis by inhaling fungal spores. Which of these terms applies to the role of soil in transmission of coccidioidomycosis?
Soil is the reservoir.
Which one of these diseases is noncommunicable?
botulism is not spread from person to person, and is thus considered a noncommunicable disease.
Consider these five infectious diseases: Ebola hemorrhagic fever avian influenza SARS West Nile encephalitis mad cow disease Which of these features is shared by this group of diseases?
These diseases are considered to be emerging infectious diseases.