Patho chapter ch 6

What is microbiology?

the study of microorganisms or microbes, very small living forms that are visible only with a microscope.

What are some microorganisms?

bacteria, fungi, protozoa, and viruses

Microorganisms with a cell wall:

Bacteria and Fungi

Microorganisms with obligate intracellular parasite:

Virus and some Protozoa

Microorganisms in DNA and RNA:

Bacteria, Fungi, Protozoa, Mycoplasma

Bacteria in reproduction:

Binary fission

Virus in reproduction:

Use host cell to replicate components and for assembly

Fungi in reproduction:

Budding and spores and extend hyphae

Protozoa in reproduction:

Varies

Mycoplasma in reproduction:

Binary fission

Drug used to treat bacteria:

Antibacterial

Drug used to treat virus:

Antiviral

Drug used to treat fungus:

Antifungal

Drug used to treat Protozoa:

Selective

Drug used to treat Mycoplasma:

Selective

Bacteria is classified as what type of cell?

prokaryotic cells because they are simple in structure—lacking even a nuclear membrane—but they function metabolically and reproduce.

Many microorganisms are classified as what because they do not cause disease

Non pathogenic

What are pathogens?

the disease-causing microbes often referred to as “germs.”

The organism causing tetanus is:

An anaerobic bacterium that thrives in the absence of oxygen, and therefore can easily cause infection deep in the tissue.

Bacteria are:

unicellular (single cell) organisms that do not require living tissue to survive. They vary in size, shape, and arrangement and are classified and named accordingly

Bacilli bacteria:

rod-shaped organisms, which include vibrio (curved rods) and pleomorphic (variable or indistinct shape).

Spirals bacteria:

include spirochetes and spirilla, displaying a coiled shape or “wavy line” appearance. These two classifications of bacterial shape differ in that the spirochete contains a structure called an axial filament, whereas the spirilla have flagella. Both of these structures facilitate cell movement.

Cocci bacteria:

Spherical forms

Diplo-bacteria

Indicating pairs

Strepto- bacteria

Indicating chains

Staphylo- bacteria

Prefix, indicating irregular grapelike clusters

Tetrads:

refers to cells grouped in a packet or square of four cells

Palisade:

refers to cells lying together with the long sides parallel

Components of the basic structure of a bacteria:

An outer rigid cell wall that is either gram positive or gram negative, a cell membrane, an external capsule or a slime layer on SOME, one or more rotating flagella, Pili and fimbriae, Cytoplasm, some bacteria secret toxins and enzymes, several species can form endospores

A bacterium has one of two types of cell walls, gram-positive or gram-negative, which differ primarily in

the thickness of the peptidoglycan in the wall

Peptidoglycan is

a mixed polymer of hexose sugars cross-linked by peptide fragments.

Gram positive and gram negative can be tested between the two by using a?

gram stain

A cell membrane is located inside the bacterial cell wall in gram-positive organisms and on how many sides of a gram negative?

Both sides

Where is the external capsule found in negative and positive?

outside the cell wall in gram-positive bacteria and outside the outer membrane in gram negatives

Flagella provide:

Motility for some species

Pili and fimbriae are

tiny hairlike projections found on some bacteria, usually the gram-negatives.

Bacteria contain cytoplasm, which contains the

chromosomes, ribosomes and RNA, and plasmids, which are circular DNA fragments that are important in the exchange of genetic information with other bacteria.

What in the cytoplasm commonly contain genetic information conveying drug resistance?

Plasmids

The cellular components provide for:

the metabolism, growth, reproduction, and unique characteristics of the bacterium.

Exotoxins

usually produced by gram-positive bacteria and diffuse through body fluids. They have a variety of effects, often interfering with nerve conduction, such as the neurotoxin from the tetanus bacillus. Other toxins termed enterotoxins may stimulate the vomiting center and cause gastrointestinal distress. Exotoxins stimulate antibody or antitoxin production, which, after being processed to reduce the toxic effect, can be used as toxoids to induce an immune response

Endotoxins

are present in the cell wall of gram-negative organisms and are released after the bacterium dies. Endotoxins may cause fever and general weakness, or they may have serious effects on the circulatory system, causing increasedcapillary permeability, loss of vascular fluid, and endotoxic shock.

Enzymes

are produced by some bacteria and can be a source of damage to the host tissues or cells. Other enzymes assist the bacteria to invade tissue by breaking down tissue components.

Endospores

a latent form of the bacterium with a coating that is highly resistant to heat and other adverse conditions

two examples of dangerous infections caused by spores in the soil entering the body, where they return to the vegetative state and reproduce.

Tetanus and botulism

Bacteria duplicate by a simple process called

Binary fission

What is binary fission

division of the cell that produces two daughter cells identical to the parent bacterium.

What is a virus?

a very small obligate intracellular parasite that requires a living host cell for replication.

Virus has a need for what, which makes it complicated to test it?

Living tissue

When a virus particle is extracellular it is called:

A virion

Virion consists of:

a protein coat, or capsid, and a core of either DNA or RNA

How are viruses classified?

By their nucleic acid content and its form

The human immunodeficiency virus (HIV) contains

RNA only, plus an enzyme to convert RNA into DNA, a process that is activated when the virus enters the host cell.

HIV contains RNA and is which type of virus?

Retrovirus

When a virus infects a person, it attaches to what?

A host cell, Viral DNA or RNA takes over control of the host cell, using the host’s capacity for cell metabolism to synthesize protein, producing many new viral components

Some viruses remain in latent stage:

they enter host cells and replicate slowly or not at all until sometime later.

Viruses tend to mutate meaning:

Change slightly during replication

Certain intracellular viruses may also alter host cell chromosomes, thus leading to

the development of malignant cells or cancer

Fungi are found

everywhere, on animals, plants, humans, and foods. Growth of various types of fungi can be observed easily on cheese, fruit, or bread. They are often found on dead organic material such as plants.

Fungal or mycotic infection results from

single-celled yeasts or multicellular molds

Eukaryotic cells

consist of single cells or chains of cells, which can form a variety of structures

Hyphae

long filaments or strands of a fungus

Hyphae intertwine to form a mass called the

Mycelium

Fungi reproduce by

budding, extending the hyphae, or producing various types of spores.

Only a few fungi are pathogenic, causing infection. Infections such as tinea pedis result from

the fungus invading the superficial layers of the skin.

Candida is normally a harmless fungus present on the skin. However, when there are imbalances in

the normal flora, it may cause infection in the oral cavity. called thrush in infants, and is a common cause of vaginal infections

Histoplasma is a fungus causing

a lung infection that may become disseminated through the body in immunosuppressed patients. Histoplasmosis is transmitted by inhaling contaminated dust or soil particles.

Protozoa are:

more complex eukaryotic organisms. They are unicellular, usually motile, and lack a cell wall, but they occur in a number of shapes, sometimes within the life cycle of a single type.

The pathogens of protozoa are

usually parasites

Some diseases caused by protozoan infection include

trichomoniasis, malaria, and amebic dysentery.

How is Trichomonas vaginalis distinguished?

By its flagella

What does Trichomonas vaginalis cause?

a sexually transmitted infection of the reproductive tracts of men and women, attaching to the mucous membranes and causing inflammation

The causative agents for malaria are what?

the Plasmodium species, belong to a group of nonmotile protozoa called sporozoa.

How does malaria work?

Plasmodium vivax gets into the red blood cells and they eventually rupture, and release new microbes and toxins into the blood which causes acute illness. The microbe is transmitted by a blood sucking insect, the female Anopheles mosquito

The amemb’s are:

a motile group of protozoa, moving by extending part of their cytoplasm and flowing forward (ameboid movement).

What is the Entamoeba histolytica parasite?

in the large intestine that causes amebic dysentery, a severe form of diarrhea, and liver abscesses if it penetrates into the portal circulation

Trophozoites

secrete proteolytic enzymes, which break down the intestinal mucosa, causing flask-shaped ulcers. Trophozoites may invade blood vessels and spread to other organs, such as the liver. The organism also forms cysts, which are resistant to environmental conditions and are excreted in the feces.

Entamoeba histolytica infection is spread by

fecal-oral route.

Naegleria fowleri, a particularly deadly ameba, has been found to be responsible

For fatal brain infections

Giardia

a cyst-forming organism that is excreted in the feces and can survive in the environment for a considerable period of time before it is ingested by a new host. a genus of flagellated protozoans that are responsible for gastrointestinal infections in humans.

Most giardiasis cases are caused by

the consumption of contaminated food or water and, in some cases, person-to-person contact.

Helminths

multicellular, eukaryotic organisms that are divided into many subgroups based on their physical characteristics. They may be very small, barely visible, or up to 1 meter in length.

Helminths or worms, are not

microorganisms, but are often included with microbes because they are parasites and cause infections in humans throughout the world.

Life cycle of helminths:

Consists of at least three stages: ovum (egg), larva, and adult.

The ova or larvae of a helminth may be

ingested in contaminated food or water, enter through the skin, or be transmitted by infected insects. They are often found in the intestine but can inhabit the lung or blood vessels during parts of their life cycle.

How are helminths usually diagnosed?

observation of ova or eggs in stool specimens

Helminths are normally found in children and include

pinworms, hookworms, tapeworms, and Ascaris or giant roundworms. When large numbers of worms are present in the body, systemic effects may develop, such as severe anemia.

Prions are protein like agents transmitted by

consumption of contaminated tissues such as muscle and brain or the use of donor tissues contaminated with the protein.

A prion is

an abnormal molecule that is transmissible from the tissues or blood of animals or humans. It induces proteins within the brain of the recipient to undergo abnormal folding and change of shape.

Creutzfeldt-Jakob disease is caused by

the consumption of meat that has been contaminated with nervous tissue from an infected animal such as beef cattle

bovine spongiform encephalopathy is

prevalent, consumption of ground meats, sausages, or offal should be avoided.

Algae

eukaryotic microorganisms that are widespread in fresh and marine waters; they are a main component of plankton and are usually not a concern for human disease.

Some fish kills have been attributed to the algae

Pfiesteria piscicida.

What is resident flora?

refers to the microorganisms that normally live on or in a specific body site

Some areas of the body, such as the lungs, brain, blood, bladder, and kidneys, lack

resident flora or are sterile under normal circumstances, and properly obtained specimens from these areas should not contain microorganisms.

Resident flora present table:

Skin, Nose, Pharynx, Mouth, Colon, Rectum, Vagina, Distal urethra and perineum

Sterile areas from table:

Blood, Cerebrospinal fluid, lungs, uterus, fallopian tubes, ovary, bladder and kidney

Certain microbes in the intestinal tract are of great benefit to the host in the synthesis of which vitamin?

K

What is a resident flora helpful for?

preventing other organisms from establishing a colony.

An infection occurs when:

a microbe or parasite is able to reproduce in or on the body’s tissues.

Endemic

Certain infections consistently occurring in a population