Basic Microbiology - Introductory Information

Prions, viruses, bacteria, fungi, protozoa, helminths, ectoparasites, bacteriophages, plasmids, and transposons

What are some different infectious agents?

Obligate intracellular pathogen

Term used to refer to an infectious agent that needs a host cell for survival

Viruses, chlamydiae, and rickettsiae

What are some different obligate intracellular pathogens?

No; either the body cell is killed or infection persists

Are intracellular mechanisms always effective in killing intracellular pathogens? What occurs if they are not?

Infection of hepatocytes by the hepatitis virus followed by a strong immune response in which infected hepatocytes are killed

What causes acute hepatitis?

Proteinaceous infectious particles that lack nucleic acids (DNA/RNA)

What are prions?

host protein PrP

Prions are abnormal forms of...

resistant to proteases

Normally in neurons, PrP undergoes a change to make it...

Conversion of more normal PrP into the abnormal infectious form

What occurs when abnormal PrP is present?

Spongiform encephalopathies

What do prions cause?

Creutzfeldt-Jakob disease (CJD), scrapie (PrPSc), kuru, and bovine spongiform encephalopathy (mad cow disease)

What are some different spongiform encephalopathies?

Cannibalism (eating infected brains)

What practice in particular allowed for the transmission of kuru?

Obligate intracellular parasites

What type of pathogen are viruses?

Nucleic acid genome surrounded by protein coat called a capsid and sometimes a lipid coat

What is the general structure of viruses?

As RNA or DNA, and if RNA, as single-stranded (ssDNA) or double-stranded (dsDNA)

How are viruses classified?

Electron microscopy (EM)

What type of microscopy is typically used to visualize viruses?

When found as cytoplasmic inclusion bodies

Under what circumstances can viruses be seen by a normal microscope?

Infections (including latent ones) and cancer

What do viruses cause?

A virus can go back to a ganglion and live until an event causes it to reappear and become virulent again

What typically occurs with latent infections with a virus?

Human papilloma virus (HPV)

What virus is known to cause cervical cancer and increase the likelihood of developing head and neck cancer?

Hepatic carcinoma

What type of cancer does hepatitis B and C cause?

prokaryotes

Bacteria are eukaryotes/prokaryotes

do

Bacteria do/do not have cell membranes

do not

Bacteria do/do not have membrane bound nuclei and membrane bound organelles

Gram stain, shape, and metabolism

What are bacteria classified by?

Gram positive and gram negative

What are the two different types of gram stain results that can be obtained?

thick cell wall surrounding the membrane

Gram positive bacteria typically have a...

do

Gram positive bacteria do/do not retain crystal-violet stain

thin wall between 2 phospholipid membranes

Gram negative bacteria typically have a...

do not

Gram negative bacteria do/do not retain crystal-violent stain

Coccus and bacillus

What are the two most common bacterial shapes?

spherical

Cocci are _______________ in shape

rod

Bacilli are ____________ shaped

Aerobic and anaerobic

What are the two types of metabolism common to bacteria?

rapid

A gram stain is a rapid/long test used to identify bacteria

Specific

Is a gram stain specific or nonspecific?

purple; red

Gram positive bacteria appear ____________ and gram negative bacteria appear _______________

flagella; cilia

Bacteria can have ___________ or ______________ (extensions from the cell membrane that aid in motility)

DNA, RNA, and proteins

Bacteria produce their own...

Favorable growth conditions

What do bacteria rely on a host for?

Colonization

Stage where bacteria are present but not causing disease because tissue invasion and a subsequent tissue response has not occurred

Skin and mucous membranes

What type of tissue do bacteria typically colonize?

>99%

What percentage of bacteria that colonize the colon are anaerobic?

Chlamydiae, rickettsiae, and mycoplasmas

Types of "bacteria" that are not considered bacteria but have slight differences

Divide by binary fission

How are chlamydiae, rickettsiae, and mycoplasmas similar to bacteria?

Lack certain structures or metabolic capabilities

How are chlamydiae, rickettsiae, and mycoplasmas different that bacteria?

obligate intracellular

Chlamydiae and rickettsiae are ___________________ organisms

Arthropods (ticks)

What serve as the vector for rickettsiae?

Endothelial cells

What cells does rickettsiae invade?

Rocky Mountain Spotted Fever

What does rickettsiae cause?

Aerosols

How are mycoplasmas spread by?

Atypical peribronchial pneumonia

What does mycoplasma cause?

tiniest

Mycoplasma are considered one of the tiniest/largest free-living organisms

hyphae; spores

Fungi have structures called _____________ and _____________

chitin; ergosterol

Fungi are prokaryotes/eukaryotes with cell walls made of _______________ and cell membranes containing ____________

Budding yeast or hyphae

How do fungi typically grow?

septated; aseptated

Hypahe can be _____________ or _______________

asexual; sexual spores

Fungi are typically sexual/asexual, but can occasionally have...

Skin, air, nails, and mucous membranes

What do fungi cause superficial infections of?

systemic; immunocompromised

Deep infections of fungi typically are systemic/localized and occur in __________________ individuals

Candida, aspergillus, mucor, cryptococcus, and pneumocystis

What are some opportunistic fungi that cause deep systemic infections?

unicellular eukaryotes

Protozoa are unicelleular/multicellular prokaryotes/eukaryotes

both

Protozoa replicate intracellularly/extracellulary/both

Plasmodium

What protozoan is known for replicating intracellularly?

Red blood cells

Where does plasmodium replicate?

Trichomonas vaginalis

Protozoan that has flagella, causes a genitourinary infection, and is sexually transmitted?

Entamoeba histolytica and Giardia lamblia

Protozoans that cause GI infections and have two forms

Motile trophozoites and immobile cysts

What are the two forms of entamoeba histolytica and giardia lamblia?

Intestinal epithelial wall

What do motile trophozoites attach to?

Gastric acid

What are immobile cysts resistant to?

Insect vectors

What are blood-borne protozoans transmitted by?

Plasmodium, trypanosoma, and leishmania

What are some blood-borne protozoans?

Toxoplasma gondii

Protozoan transmitted by kitten feces or undercooked infected meat

parasitic worms

Helminths are...

differentiated; multicellular

Helminths are highly ________________ and are unicellular/multicellular

life cycle

Helminths have complex ____________

definitive host

Sexual reproduction of helminths occur in a...

intermediate host or vectors

Asexual multiplication of helminths occurs in...

Ascaris

What are some types of helminths?

Strongyloides

Helminths that are unique in that their larvae can be infectious

Schistosomiasis

Disease caused by inflammatory response to helminth eggs or larvae

number of worms present

With diseases caused by helminths, the disease is often proportionate to the...

Insects or arachnids that attach to and live on/in skin

What are ectoparasites?

direct effect or by serving as a vector

Ectoparasites produce disease by...

Inhalation, ingestion, sexual transmission, insect or animal bites, injection, and direct contact

What are the routes of entry of microbes?

Fecal-oral and saliva

How are microbes ingested?

Blood

Injection of what allows for the transmission of microbes?

Mucous membranes and skin

Direct contact with what causes the transmission of microbes?

Innate and adaptive mechanisms

What are two mechanisms of the body to prevent microbes from entering the body?

Innate mechanisms

Defenses of the body that are always present and respond quickly to infection

Physical barriers, phagocytes, natural killer cells, and plasma proteins

What are some innate mechanisms of defense against pathogens?

Adaptive mechanisms

Mechanism of defense against microbes that are stimulated by exposure to microbes and increased with repeated exposures

T and B lymphocytes

What cells make up the adaptive arm of the immune system?

Low pH, fatty acids, and keratinized outer lower

How does the skin protect the body from infection?

abnormal skin or a vector

Skin infection often occurs do to...

fecal-oral route

Most GI pathogens are transmitted by...

Gastric acid

Important defense against pathogens in the stomach

Shigella and Giardia

What types of microorganisms are somewhat resistant to gastric acid?

Viscous mucous layer, pancreatic enzymes and bile, defensins, normal microbiota flora, and IgA antibodies

What are GI defenses against microbes?

Mucosal antimicrobial peptides

What are defensins?