Microbes Flashcards
Bacteria average size
• 0.2 - 10 micrometer
Bacteria structure
• Cell walls – No nuclear membrane – Circular DNA
Bacteria types by shape/examples
- Cocci: Staph. aureus, Strep. faecalis, Neis. gonnorhea
- Rods: E. coli, Clostridum difficile, Bacillus anthracis
- Spirals: Treponema pallidum, Vibrio cholera, Borrelia burgdorferi
• Gram stain
– Gram positive bacteria retain crystal violet; gram negative take on safranin counterstain.
Chlamydiae
Average size: 0.3 - 1.0 micrometers • Structure: Tiny, obligate pathogens Chlamydia pneumoniae intracellular pathogens, similar to gram-negative bacteria, however, lack ability to produce metabolic energy / synthesize ATP • Types/examples: Chlamydia trachomatis, Chl di i Chlamydia trachomatis Chlamydia pneumonia, Chlamydia psittaci
Rickettsiae size
• Size: 0.3 micrometers - 0.6 micrometers
Rickettsiae structure
• Structure: Pleomorphic coccobacilli that have gram neg. cell wall structure, but don’t stain well. Usually transmitted by arthropods.
Rickettsiae types/examples
• Types/examples: R. rickettsii (Rocky Mtn. spotted fever), Coxiella burnetti (Q fever), Ehrlichia ewingii
Mycoplasma
- Size: 0.05 m - 0.5 m
- Structure: lack cell wall, but can be cultured on cell free media. Pass through 0.45 um filters.
- Types/examples: Mycoplasm pneumonia, major cause of upper and lower respiratory infections; Mycoplasm hominis.
Fungi – Mycelial (Molds) size
• Variable
Fungi – Mycelial (Molds) structure
• Have nuclear membranes containing chromosomes; cell walls contain chitin; produce multicellular filamentous colonies
Fungi – Mycelial (Molds) types/examples
• Mushrooms, Coccidioides imitis, Histoplasma capsulatum, Aspergillus, Penicillium,
protozoa size
• 2 - 60 micrometers
protozoa structure
• Unicellular eukaryotes; some are motile; have organelles that function like organs in higher animals
protozoa types/examples
Plasmodium vivax/malariae, Toxoplasma gondii, Trypanosoma spp., Entamoeba Leishmania spp., Giardia lamblia, Entamoeba histolytica, Cryptosporidium spp.
Viruses size
• 20 nm - 400 nm
Viruses structure
• Small, infectious obligate intracellular parasites whose genome consists of DNA or RNA.
Viruses lipid enveloped
• Enveloped: Herpes simplex, CMV, RSV, hantavirus, Hepatitis B&C, HIV, Influenza, Ebola, SARs, Rubella, Smallpox
Virus Classification Criteria Classic and modern
- Classic: – Nature of nucleic acid – Symmetry of capsid – Enveloped vs. non-enveloped – Dimension of virion and capsid (size) – What they infect
- Modern: Uses genomics to determine the relatedness of nucleic acid sequences, gene products, and organization of genes
Prions
- Proteinaceous “infectious” particles
- Abnormal isoform of normal cellular protein
- PRPC ————-> PRPSc
- No attributes of a microrganism, i.e., no nucleic acids, capsids, etc.
- Causes transmissible spongiform encephalopathies (TSEs), e.g, Creutzfeld Jakob Disease (CJD), BSE (Mad Cow Disease), scrapies, chronic wasting disease, etc.
- Extremely difficult to inactivate
Mycoplasm pose a major contamination issue in cell culture. How are they different from other bacteria?
lack cell walls
Fungi - Yeast size
3 - 15 micrometers
Fungi - Yeast structure
Same as molds, but don’t form true multicellular hyphae; reproduce by budding or binary fission
Fungi - Yeast types/examples
Candida albicans, Cryptococcus neoformans, Saccharomyces cerivisiae
Trichophyton sp.
Flaviviruses
size, shape. nucleic acid
40-60nm
enveloped, icosahedral nucleocapsid
positive-sense, single stranded RNA approximately 10,000-11,000 bases
The Chain of Infection
- A susceptible host
- A pathogen
- Virulence
- Sufficient quantity (or infectious dose)
- Portal of entry
Virulence
agent’s degree of pathogenicit
Prion Diseases
• Scrapie in sheep and goats • Bovine spongiform encephalopathy (BSE) in cattle • Kuru in humans • Creutzfeldt-Jakobdisease (CJD) in humans
Prions are believed to infect
and propagate by
refolding abnormally into a structure which is able to convert normal molecules of the protein into the abnormally structured form
Prion Diagnostics
• CSF-detection of the mutated protein
• Blood, brain, or other tissues-detection of
mutation in the prion protein gene
• Brain tissue
– Detection of the prion protein
– Microscopic examination and immunohistochemical
detection of the prion protein
Prions highest concentrations
• The highest concentrations of prions are in the central
nervous system and its coverings
Prions main precaution
• The main precaution to be taken when working with
prion-infected or contaminated material is to avoid
puncture of the skin
Prions communicable
• Human prion diseases are not communicable or
contagious
• There is no evidence of contact or aerosol transmission
of prions from one human to another
Fungal Infection Treatment
• Antifungal medications are widely used – Nystatin – Amphotericin B – Miconazole – Fluconazole
Anti-parasitic medication
– Flagyl
– Chloroquine
– Fansidar
Endoparasites (hookworms)
Those that live inside the host
Ectoparasites (mites)
those that live on its surface
Classic examples of parasitism
tapeworms,
flukes, Plasmodium species and fleas
Bacterial growth has three phases:
– First is a period of slow growth as cells are
adapting to high nutrients and fast growth
– Second is marked by rapid, exponential
growth as nutrients are metabolized at
maximum speed until the they are depleted
– Third the cells reduce their metabolic activity
and consume non-essential cellular proteins
Viruses non-lipid enveloped or small viruses
polio virus, coxsackievirus, rhinovirus, Hepatitis A, Parvo, Rhinovirus, Norwalk virus, Rotavirus
• Acid-Fast stain G+ G-
– Acid-fast bacteria stay pink retaining carbol fuchsin; methylene blue does not affect, e.g. M. tuberculosis
What is mold?
The term “mold” is a colloquial term for a group of filamentous fungi that are common on
food or wet materials.
Most of these are Ascomycetes that produce a lot of spores.
How can I prevent mold growth?
Relative Humidity:
Temperature: Warm air holds more moisture than cold air.
Poor Ventilation:
People who may be affected more severely and quickly to mold than others include:
Infants and children Elderly people Pregnant women Individuals with respiratory conditions or allergies and asthma Persons with weakened immune systems
