Class notes

Advanced Topics in Infectious Disease

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Course
LISC483 (MICR483)

Institution
Queen’s University (QU )

Includes all course notes including the topics: - Intro to bacteria of the human body - Multidrug resistant bacteria -Medical parasitology -Parasites in Canada -Medical virology -Emerging viral infections -The World of Fun-guy -Dimorphic fungi

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Uploaded on July 1, 2024
Number of pages 113
Written in 2020/2021
Type Class notes
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Microorganisms
Friday, September 25, 2020 11:01 AM

BACTERIA Sterile :
• Streptococcus pneumonia • Bladder
○ Gram positive • Lower respiratory tra
○ Most common cause of community acquired pneumonia
○ Nasal cavity
○ Use efflux pumps and altered binding sites as methods of antibiotic resistance

• E. coli
○ Gram negative
○ Bacillus
○ Certain types can cause food poisoning
○ Resident of GI flora
○ Typically found in wounds of the lower part of the body
○ Possesses extended-Spectrum Beta-lactamases, enzyme that inactivates beta-lactams

• Enterococci species
○ Gram positive
○ Common cause of UTIs
○ Gut - resistant to bile

• Staphylococcus aureus
○ Gram positive
○ Most common cause of surgical site infections
○ Skin & upper respiratory tract (can cause infections here too)
▪ Can also be found on the axilla, hands, nose and perineum
○ Leading cause of cellulitis
○ Coagulase positive
○ Can release toxins
○ Leads to activation of Tregs and inactivation of helper T cells
○ Small colony variants able to evade immune mechanisms by being metabolically quiescent
○ MRSA- multidrug resistant organism that is responsible for skin and soft tissue infections,
bacteremia, and endocarditis
▪ Use efflux pumps and altered binding sites as methods of antibiotic resistance

• Pseudomonas aeruginosa
○ a gram + organism
○ Uses efflux pump
○ Most often found in environment and is often found forming biofilms in hospital sinks and other
water sources
○ Also normal flora of the GI tract
○ Aside from wound infections, is the leading cause of ventilator associated pneumonia (VAP)
▪ Forms a biofilm around the VAP and begins to seed the respiratory tract leading to infection

• Lactobacillus
○ Gram positive
○ Facultative aerobe
○ Produces lactic acid (maintaining acidity of vagina)

• C. difficile
○ Anaerobic
○ Spore forming
○ Gram + bacillus
○ Antibiotic resistant
○ Can produce toxins (can lead to colitis)
○ Leading cause of antibiotic-associated diarrhea

• Paenibacillus polymyxa
○ Produced cell wall synthesis inhibitor, colistin (antibiotic)
○ Gram + bacteria used for biofertilizer and biocontrol agent in agriculture

LISC 483 Page 1

, • Chromobacterium viola
○ Produced Aztreonam, a beta-lactam antibiotic
○ Bacteria that rarely infects humans, but when it does can cause skin lesions, sepsis, and liver
abscesses

• Klebsiella pneumoniae
○ Gram-negative enterobacterium that can cause severe pneumonia, enteritis (inflammation of
intestine), UTIs, and more
○ Possesses extended-Spectrum Beta-lactamases, enzyme that inactivates beta-lactams

• Proteus mirabilis
○ Gram-negative, rod-shaped bacteria that can cause UTIs
○ Possesses extended-Spectrum Beta-lactamases, enzyme that inactivates beta-lactams

PARASITES

• Plasmodium spp.
○ Endoparasite : protozoa
○ Single celled
○ Responsible for causing malaria in humans
○ Transmitted to humans via a vector- the mosquito

• Giardia spp.
○ Endoparasite : protozoa
○ Colonizes small intestine
○ Infection causes giardiasis, characterized by abdominal pain and diarrhea

• Toxoplasma spp.
○ Endoparasite : protozoa
○ Infection with Toxoplasma gondii causes the disease toxoplasmosis
○ Single-celled
○ Found in blood and tissues

• Cestodes
○ Endoparasite: helminth
○ Flatworm parasites (most are tapeworms)
○ Can infect humans in live in intestines
▪ Infections can usually remain asymptomatic, but some common symptoms include diarrhea,
vomiting, weight loss and abdominal discomfort
○ Transmitted by eating undercooked meat from infected animals

• Trematodes
○ Endoparasite: helminth
○ Flatworm
○ Commonly infect blood vessels, lungs, GI tract and liver

• Nematodes
○ Endoparasite: Helminth
○ Roundworm
○ Transmitted through contaminated water or food

• Sarcoptes scabiei
○ Ectoparasite: Arthropods
○ Responsible for scabies, a contagious skin infestation that is also known as the seven -year itch
○ Most common clinical manifestations is severe itchiness and a rash. Occasionally, tiny burrows may
be seen in the skin

• Pediculus humanus
○ Ectoparasite: Arthropods
○ Organism responsible for lice in humans
○ Can infect the body or head and feed on human blood

LISC 483 Page 2

,LISC 483 Page 3

, Antibiotic classification
Monday, October 12, 2020 10:14 PM

➢ Cell wall synthesis inhibitors
1. Beta-lactams
○ MOA
▪ Exert their bactericidal effects by binding to the transpeptidase enzyme complex
▪ Prevents the enzyme from forming cross-links between NAM and NAG
▪ This weakens the structural integrity of the bacterial cell wall and along with the high osmotic pressure, causes the cell wa
to rupture ultimately leading to cell death
2. Glycopeptides
○ MOA: stop the extension of the PG unit of the bacterial cell wall by binding to the D-Ala-D-Ala peptide of the NAM subunit and
prevent cross-linking from occurring which destabilizes the cell wall

➢ Protein synthesis inhibitors - inhibit translation by targeting different sites on the 30S and 50S subunits of cell's ribosomes
3. Tetracyclines: bind to 50S to block attachment of tRNA to the ribosome, thus amino acid cannot be added to growing polypeptide cha
4. Macrolides: bind to 50S subunit to inhibit peptidyl transferase, preventing enzyme from adding new amino acids to the growing
polypeptide chain
5. Aminoglycosides : bind to the 30S subunit which disrupts the proofreading process, thus incorrect proteins are produced

➢ Nucleic acid inhibitors - inhibit DNA replication ,
6. Fluoroquinolones
○ Inhibition of 2 key enzymes :
1. Topoisomerase IV (unlink newly replicated DNA strands)
▪ Fluoroquinolones bind to topoisomerase IV and prevent the separation of newly formed daughter strands
▪ Causes the DNA to break and ultimately leads to cell death
2. DNA gyrase (introduce negative supercoils into DNA to combat supercoiling)
▪ Fluoroquinolones bind to the DNA-DNA gyrase complex causing the DNA to break, resulting in cell death

➢ Metabolic inhibitors - interfere w/ formation of key bacterial metabolic substrates, primarily by inhibiting translation
7. Folate inhibitors
○ Inhibit formation of tetrahydrofolic acid (THF), which is essential for bacteria to synthesize DNA and protein
○ Contains sulfamethoxazole (competitively inhibits the synthesis of dihydropteroic acid) and trimethoprim (competitive inhibitor
dihydrofolate reductase)

B-lactams Bind to transpeptidase enzyme complex and prevent the formation of cross-links between PG
Glycopeptides Bind to the sidechain of PG to prevent cross-linking between chains
Fluoroquinolones Bind to and inhibitor DNA gyrase and topoisomerase IV, to inhibit DNA replication
Folate inhibitors Inhibit formation of tetrahydrofolic acid, which is essential for bacterial growth
Aminoglycosides Bind to the 30S subunit of the ribosome to disrupt the proofreading process
Tetracyclines Bind to the 50S subunit to block the attachment of tRNA to the ribosome
Macrolides Bind to the 50S subunit to inhibit peptidyl transferase, preventing the addition of new amino acids to the polypeptide chain

LISC 483 Page 4

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