Microbiology and Parasitology Lecture (L7-9) Flashcards
is the study of the vital life
processes of organisms
Physiology
concerns the vital life
processes of microorganisms.
Microbial physiology
- ideally suited- inexpensive to maintain, take up little space and
reproduce quickly (E. coli)
Bacteria
All living protoplasm contains six major
chemical elements:
carbon, hydrogen,
oxygen, nitrogen, phosphorus, and sulfur.
Other elements, usually required in lesser
amounts, include :
sodium, potassium,
chlorine, magnesium, calcium, iron, iodine,
and some trace elements.
All microbes have a need for three things:
carbon, energy, and electrons
(other nutrients).
refers to all the
biochemical reactions that
occur in a cell or organism.
Metabolism
a protein that either causes a particular chemical reaction to occur or
accelerates it.
Biologic catalyst
- Remain within the cell that
produced them - Digestive enzymes of
Phagocytes
Endoenzymes
- Leave the cell to catalyze rxns
outside the cell - Cellulase and pectinase, which
are secreted by saprophytic
fungi to digest cellulose and pectin.
Exoenzymes
-cannot, on their
own, catalyze a chemical reaction.
- must link up with a cofactor to catalyze a chemical reaction.
Apoenzymes
reactions that “break down”
molecules requiring the breaking of bonds. Major E source
Catabolic
reactions that build new
molecules requiring the formation of
bonds.
Anabolic
is a series of linked
biochemical reactions that occur in a stepwise
manner, leading from a starting material to an
end product
biochemical pathway
produced during glycolysis are converted into acetyl-CoA molecules which
then enter The CAC.
Pyruvic acid
the study of
heredity
Genetics
-the study of the mechanisms of heritable information in bacteria, their chromosomes, plasmids, transposons and
phages.
-The entire genetic content of a cell is its genome.
Bacterial Genetics
- Complete collection of genes
- The genetic material passed between generations.
Genotype
- All its physical traits, attributes
or characteristics - Manifestation of genotype
Phenotype
- Actively expressed all the time
- ribosomes are constantly
needed for protein synthesis
Constitutive Genes
- Expressed only when needed
- the glucose transporter proteins that muscle cells produce in response to insulin
Inducible Genes
beneficial, harmful, silent
A change in the characteristics of a cell caused by a change in the DNA molecule that is transmissible to the
offspring
Mutations
- Are of benefit to the organism
- lead to new versions of proteins that help
organisms adapt to changes in their environment. - lead to antibiotic-resistant strains of bacteria.
Beneficial mutation
-leads to the production of a nonfunctional enzyme.
-Lethal mutation
Harmful mutation
- They have no effect on the cell
Silent Mutations
- Involves bacteriophages and
the acquisition of new viral genes - Lysogenic conversion –>
lysogeny - prophage
- The bacterial cell containing
the prophage: lysogenic cell - imparts genes with special functions to bacterial cells
without such functions. - Corynebacterium diphtheriae
Lysogenic Conversion
- transfer of a DNA fragment from one
bacterium to another by a bacteriophage.
Transduction
is a form of genetic recombination in which a DNA fragment from a dead, degraded bacterium enters a competent recipient bacterium and is
exchanged for a piece of DNA of the recipient.
Transformation
- Cell-to-cell contact
- Sex pilus
- encoded by plasmids or transposons.
- a. General mechanism of transfer of conjugative
plasmids by conjugation in Gram-negative bacteria - This is the mechanism by which resistance
plasmids (R-plasmids), coding for multiple
antibiotic resistance and conjugation pilus
formation, are transferred from a donor
bacterium to a recipient. - F+ conjugation
- the donor bacterium carries a DNA sequence
called the fertility factor, or F-factor. - c. Hfr (high frequency recombinant) conjugation.
Conjugation
grow only in the presence of oxygen.
Obligate aerobes
require a low concentration of oxygen (2% to 10%) for growth, but higher
concentrations are inhibitory.
Microaerophiles
grow only in the absence
of oxygen and, in fact, are often inhibited or killed
by its presence.
Obligate anaerobes
grow only in the absence
of oxygen and, in fact, are often inhibited or killed
by its presence.
Obligate anaerobes
cannot use oxygen to
transform energy but can grow in its presence.
Aerotolerant anaerobes
grow with or without
oxygen, but generally better with oxygen.
Facultative anaerobes
best at a pH 7.0–7.4
Neutrophiles grow
prefer pH of 2 to 5
Acidophiles
grow
best at a pH above 8.5.
Alkaliphiles
- the diffusion of water across a membrane from an area of higher water concentration (lower solute concentration) to lower water concentration (higher solute concentration).
- Solution: consists of a solute dissolved in a solvent
- Solute refers to all the molecules or ions dissolved in the water (the solvent).
Osmosis
- the diffusion of water across a membrane from an area of higher water concentration (lower solute concentration) to lower water concentration (higher solute concentration).
- Solution: consists of a solute dissolved in a solvent
- Solute refers to all the molecules or ions dissolved in the water (the solvent).
use radiant energy (light)
as their primary energy source.
Phototrophs
use the oxidation and
reduction of chemical compounds as their primary energy source.
Chemotrophs
require only carbon dioxide as a
carbon source.can synthesize
organic molecules from inorganic nutrients.
Autotrophs
require organic forms of carbon. A
heterotroph cannot synthesize organic molecules from inorganic nutrients.
Heterotrophs
thrive deep in the ocean and in oil wells, where the atmospheric pressure is very high.
Piezophiles
involves the destruction or elimination of all
microbes, including cells, spores, and viruses.
Sterilization
Elimination of most or all pathogens (except bacterial spores)
Disinfection
An agent that is cidal in action will kill
* General terms like germicidal agents (germicides), biocidal agents (biocides), and microbicidal agents (microbicides) are disinfectants or antiseptics that kill microbes.
Cidal
kill bacteria, but not necessarily bacterial endospores. Sporicidal agents are required to kill spores
Bacterial agents
kill fungi, including fungal spores.
Fungicidal agents
kill algae in swimming pools and hot tubs.
Algicidal agents
agents destroy viruses.
Viricidal
agents kill Pseudomonas species, and tuberculocidal agents kill M. tuberculosis
Pseudomonicidal
agent is a drug or chemical that
inhibits reproduction of microorganism
* s, but does not necessarily kill them.
microbistatic
agent is one that specifically
inhibits the metabolism and reproduction of bacteria.
* Freeze-drying (lyophilization) and rapid freezing
(using liquid nitrogen) are microbistatic techniques that are used to preserve microbes for future use or study.
* Sepsis refers to the presence of pathogens in blood or tissues, whereas asepsis means the absence of pathogens.
bacteriostatic
used to eliminate and exclude pathogens.
Aseptic techniques
the prevention of infection.
Antisepsis
use of any chemical ( drug) to treat any disease or condition.
Chemotherapy
chemotherapeutic agents used to treat infectious diseases
Antimicrobial agents
Effective in treating malaria
Cinchona Bark
a substance produced by a microorganism that is effective in killing or inhibiting the growth of other microorganisms.
Antibiotic
- interferes with the synthesis and cross-linking of
peptidoglycan» inhibiting cell wall synthesis
**β -lactam drugs - kills bacteria through binding of the beta-lactam ring to DD
-transpeptidase, inhibiting its cross -linking activity and preventing new cell wall formation.
Penicillin
- β-lactam drugs; produced by molds; interfere
with cell wall synthesis and are bactericidal - They have no activity against LAME: Listeria,
Atypical (Mycoplasma/Chlamydia), MRSA,
Enterococci (except MRSA in Ceftobiprole and
other 5th Gen) - 1st gen: against Gram-positive bacteria.
- 2nd gen: increased activity against Gram (-);
- 3rd gen: even greater activity against Gram (-)
(including Pseudomonas aeruginosa). - 4th gen: Gram (-) and (+), including P.
aeruginosa)
Cephalsporin
- Broad-spectrum; bacteriostatic
- inhibit the 30Sribosomal subunit, hindering the binding
of the aminoacyl-tRNA to the acceptor site on
the mRNA-ribosome complex.
Tetracyclines
-Broad spectrum: bactericidal drugs that inhibit protein synthesis
- effective against a wide variety of aerobic gram,-negative bacteria, but are ineffective against anaerobes
Aminoglycosides
- Bacteriostatic at
lower doses but bactericidal at higher doses - Inhibit protein synthesis
- erythromycin, clarithromycin, and Azithromycin.
Macrolides
- bactericidal drugs thatinhibit DNA synthesis
- ciprofloxacin, is effective against members of the family Enterobacteriaceae and P. aeruginosa.
Fluoroquinolones.
-a single antimicrobial agent is not sufficient to destroy all the pathogens
-two or more drugs may be used
simultaneously to kill all the
pathogens
Multi-drug therapy
- When the use of two drugs produces an extent of pathogen killing that is less than that achieved by either drug alone, the phenomenon is known as
antagonism
Synergism
- When the use of two antimicrobial agents to treat an
infectious disease produces a degree of pathogen killing that is far greater than that achieved by
either drug alone, the phenomenon is known as
Synergism.
Antagonism
-By binding with cell membrane sterols (e.g., nystatin and amphotericin B)
-By interfering with sterol synthesis (e.g., clotrimazole and miconazole)
-By blocking mitosis or nucleic acid synthesis (e.g., griseofulvin and 5- Flucytosine
Antifungal Agents
- usually quite toxic to the host
- (a) interfering with DNA and RNA
synthesis (e.g., chloroquine, pentamidine, and quinacrine), or - (b) interfering with protozoal
metabolism (e.g., metronidazole; brand name Flagyl).
ANTIPROTOZOAL AGENTS
- are particularly difficult to develop and use because viruses are produced within host cells.
- Work by inhibiting viral replication within cells.
- The first antiviral agent effective against human immunodeficiency virus (HIV) —zidovudine (also known as azidothymidine [AZT])—was introduced in 1987.
ANTIVIRAL AGENTS
Superbugs strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics and other medications commonly used to treat the infections they cause.
DRUG RESISTANCE
- resistant to all anti- staphylococcal drugsexcept vancomycin and one or two more recently developed drugs (e.g., Synercid and Zyvox).
MRSA and MRSE
- These strains are resistant to
most anti-enterococcal drugs, including vancomycin. - Enterococcus spp. are common causes of healthcare-associated infections, especially urinary tract infection
- May be intrinsic or acquired resistance.
Vancomycin-resistant
Enterococcus spp.
(VRE)
- These strains are resistant to the two most effective first- line therapeutic drugs— isoniazid and rifampin
- Extensively drug-resistant strains, called XDR-TB are
also resistant to the most effective second-line therapeutic drugs— fluoroquinolones and at
least one of the following: amikacin, kanamycin,
capreomycin.
Multidrug-resistant M. tuberculosis
(MDR-TB)
- The patient may become allergic to the agent. For example, penicillin G in low doses often sensitizes those who are prone to allergies; when these
persons receive a second dose of penicillin at some later date, they may have a severe reaction known as
anaphylactic shock, or they may break out in hives.
Allergy
- Prolonged antibiotic use can lead to
population explosions of microorganisms
that are resistant to the antibiotic(s) being
used. Such overgrowths are known as
“superinfections.” - A superinfection can be thought of as a
“population explosion” of organisms that
are usually present only in small numbers. - Yeast vaginitis
Superinfections
