Class Notes (839,119)
Canada (511,196)
Health Sciences (1,435)
HSS1100 (166)
Lecture 4

Lecture 4.docx

8 Pages
129 Views

Department
Health Sciences
Course Code
HSS1100
Professor
William Yan

This preview shows pages 1,2 and half of page 3. Sign up to view the full 8 pages of the document.
Description
Lecture 4 Slide 1: -organized by structural morphology Gram Positive Cocci -bacteria that stain gram positive and are round (cocci) Slide 2: Staphylococcus aureus (genus species name) -most important gram positive cocci pathogen we will cover -gram positive bacteria -the cellular arrangement of the round cells resemble a cluster of grapes ("staphule") -dairy products (creamy sauces) are most vulnerable to S.aureus -considered a 'prototype' for successful pathogens; one of the most successful pathogens -makes many toxic substances that allows it to overcome many barriers when it encounters the body -cytotoxin (cellular toxin) affects / kills certain cells in the body -hemolysins break down RBCs that release nutrients / iron that bacteria can use to thrive -enterotoxins (entero refers to the enteric system or the gut) causes troubles in the digestive system -are heat sensitive -exfoliative toxins affect skin and cause severe rashes -common in infants -toxic shock syndrome toxin 1 can lead to toxic shock syndrome -more rare than other toxins Slide 3: Enzymes -coagulase -coagulates blood and forms localized blood clots -blood clots helps protect the bacteria long enough so that it can survive and multiply -important virulence factor for S.aureus -among the many species of Staph, only S.aureus produces coagulase -coaguluse can be used as a test / screen to detect this bacteria -beta-lactamase (penicillinase) -is an inactivating enzyme that can break down the anti-biotic -destroys penicillin -allows for resistance against penicillin by S.aureus Slide 4: -S.aureus is a very common infectious agents due to its characteristics -treated by anti-biotic therapy -penicillin was the perfect drug for treating S.aureus infection -overuse has selected for a highly resistant population -95% of the time, the strain is resistant -penicillin is rarely used now -vancomycin was used for resistant strains; there are now vancomycin-resistant S.aureus -after using both penicillin and vancomycin together, there are strains that are resistant to both -methacilin was also used in combination; MRSA (multiple resistant / methacillin resistant S.aureus) -must rely on the body's immune system to kill of strains that are resistant to all these anti-biotics -hospitals cannot afford to let MRSA spread so patients are isolated immediately -causes localized infections (lesions, boils) -can infect the eye (conjunctivitis) -can progress into pneumonia, heart infections, etc. but these are rare -can cause food poisoning, toxic shock syndrome, scalded skin syndrome depending on the toxin that the strain produces Slide 5: -the hospital is the most likely place to get S.aureus infection because it is so widespread -cannot rely on anti-biotics -prevention is key to minimize infection -using proper aseptic techniques in the ER and OR where wound infections are common -education -handwashing -resistance may be decreasing now because of the minimized use of anti-biotics -there is no advantage for resistant strains if anti-biotics aren't used; the selective pressure for resistant strains is decreased Slide 6: Staphylococcus epidermidis -same genus as S.aureus -main difference between the 2 are that S.epidermidis is not considered a true pathogen; considered an opportunistic pathogen -most common bacteria in the normal flora of the skin Slide 7: Streptococci -gram positive cocci -same cellular structure as Staphylococcus (gram positive) -arranged in chains or pairs; "streptos" = twisted -there are many species of streptococci that are true pathogens to humans -there are 3 separate schemes to separate the large number of strains of Streptococci 1) Hemolytic Properties -some strains of streptococci can make hemolysins a) beta hemolytic strain (complete hemolysis) -produces a very large amount of hemolysins -beta hemolytic strains grown on a blood agar plate results in lysed RBCs by toxins -the colony has a distinct halo that is completely transparent -all the RBCs around the colony are lysed, producing the transparent halo b) alpha hemolytic strain (partial hemolysis) -only breaks down some of the RBCs -creates a faint halo around the colony; less distinct c) non-hemolytic strain (gamma hemolytic) -no halos can be seen -no hemolysins are present in strains; no hemolysis of RBCs 2) Carbohydrate C Antigen Typing (Lancefield Classification) -used frequently for many bacteria -system is based on antibody-antigen reaction -in the cell wall of Streptococci, there is a carbohydrate antigen which is used to differentiate it from different bacteria -the most common is carbohydrate A antigen and so on 3) M-Protein -involves antibody-antigen reactions -the antigen is an M-protein -M-protein is a specific pilli -used to separate the large number of beta hemolytic streptococci -used to divide group A classified streptococci Slide 8: Streptococcus pyogenes -most common streptococci pathogen -group A (most common) Lancefield typing -beta hemolytic -respiratory tract infection -causes acute tonsillitis (strep throat) which is probably the most common infection cause by S.pyogenes -persisting infection may cause rheumatic heart disease, but this is rare -can cause skin infections -i.e.: impetigo, cellulitis -if it enters the blood stream, it may cause fever and septicemia -S.pyogenes can make toxins -streptolysin (O and S) -functions to kill off neutrophils and macrophages -helps the bacteria overcome the immune system -Spes (streptococcal pyrogenic exotoxins) -causes scarlet fever rash -common in younger children Slide 9: Streptococcus pyogenes -certain strains can also make hyaluronidase (an enzyme that helps the spread of bacteria into tissues) -most strains are highly sensitive to penicillin G -is still the drug of choice to treat infection -prevention is important Slide 10: -the most serious consequence from an S.pyogenes infection is necrotizing fasciitis (flesh eatin
More Less
Unlock Document

Only pages 1,2 and half of page 3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit