Quesmed Microbiology Qs Flashcards
What is Group B Strep?
Streptococcus agalactaei
Gram positive cocci which is the most common cause of neonatal meningitis and sepsis.
What is streptococcus pneumoniae?
Alpha haemolytic + diplococcus
Causes: pneumonia, meningitis, ear/eye/sinus infection
It is facultative aerobe, which can grow with or without o2 and appears in a PAIR
What are the group A strep?
Streptococcus pyogenes
They are typically found in the nose and throat and are beta haemolytic,.
How do alpha haemolytic organisms appear on agar?
Partial RBC breakdown so there is a ring of partial clearness around them on agar. Streptococcus pneumonia is a beta haemolytic;
How do beta haemolytic organisms appear on agar?
Completely break down RBCSs and have a clear ring surrounding them. Group A strep is a beta haemolytic organism.
Which infections are caused by Group A Strep?
Streptococcus pyogenes causes:
Tonsillitis
Otitis Media
Cellulitis
Toxic Shcok syndrome
Impetigo
Which bacteria causes delayed infection?
Streptococcus pyogenes. Post streptococcal complications include:
Post-streptococcal glomerulonephritis
Rheumatic fever
Scarlet Fever
Why do complications occur with streptococcus?
Post-streptococcal complications are a result of antigenic cross-reactivity to streptococcal M protein, which resembles proteins present in the bodies connective tissue.
What is rheumatic fever?
Occurs after throat infection with Strep A, that causes red and swollen tender joints.
What is the herd immunity level required for diphtheria?
75%
What are the features of helicobacter pylori?
Spiral-shaped gram-negative bacilli which requires faeco-oral transmission. It is associated with peptic ulcer disease, gastric cancer and lymphoma of the MALT.
NO ASSOCIATION TO GERD.
How does vibrio cholerae work?
Reverses concentration gradient of ions on the channel. promoting adenylate cyclase activity and causing increased intracellular [cAMP]
What is osmolality?
Concnetration of solutes, measured in KILOGRAMS.
How does oral rehydration therapy work?
Increases action of Na+/glucose transporter to cause the drawing in of water passively into the lumen, due to a increase in osmolality.
Gram positive
Thick peptidoglycan cell wall and produce only exotoxins. Turns blue/violet on gram stain.
Gram negative bacteria
Outer LPO cell wall, inner thin peptidoglycan. Produces exotoxins and endotoxins. Turns pink on gram stain.
WHat is the most common cause of meningitis in babies and elderly?
Neisseria meningitis is the most common cause of meningitis in babies, children and elderly. It is a gram negative cocci which produces ENDOtoxins.
What is the most common cause of meningitis in newborns?
Group B strep, a beta-haemolytic organism carried in the vaginal canal of 1/4 of women,.
What is the most commmon cause of meningitis in neonates?
Neisseria
What is the most common cause of meningitis in young adults?
Gram positive species, such as Streptococcus.
What is the difference between Streptococci and Staphylcocci?
Streptococci tend to be in chains, Staphylococci tend to be in clusters.
Catalase positive in Staphylococci vs catalase-negative in Streptococci
What is the most common cause of tonsillitis?
Streptococcus pyogenes, which will typically lead to rheumatic fever with swollen and red joints.
What infections does Staph Aureus cause?
Osteomyelitis
Septic arthritis
Toxic Shock syndrome through exotoxins
Pneumonia
Which antibiotic treats MRSA?
Vancomycin
What is the effect of shiga toxin from E.Coli?
Inhibits the 60s ribosome to allow infiltration of intestinal epithelia.
What does nystatin target?
Cell membrane, via ergosterol pore formation
What type of virus is smallpox?
Ds DNA virus
What is the role of the spikes on influenza?
H spike and N spike are important for adsorption to the host cell.
Influenza also has an M2 ion channel for causing uncoating.
What is the role of the H spike?
Binding to sialic acid.
What is the role of the N spike?
Cleavage of sialic acid for release of virus.
How does herpes affect cells?
Causes cells to fuse together and form a giant multinucleated cell
What is conjugation?
Cell-cell contract between bacteria, with a sex pillus.
What is transposons?
Insertion of bacterial DNA into another bacteria
What is transduction?
Use of bacteriophage virus to transfer DNA to bacteria cells to use as a host.
What is transfection?
Virus and bacteria transfer information between each other using a virus.
Enterohaemorhhagic E.Coli
Produces Shiga toxin that causes bloody diarrhoea
What is the test for HIV diagnosis?
ELISA test for antibodies in response to HIV infection, which are present after 4 weeks, to allow time for adaptive immune response.
Which form of malaria causes hepatocytes infection?
Sporozoite. They form schizonts and mature into merozoites.
Which form of malaria reproduces asexually?
Trophozoites, which come from merozoites that infect erythrocytes. Trophozoites differentiate into female or male gametophytes.
What is benign malaria?
Caused by vivax, ovale or malaria
Treated with Chloroquinine.
What are endotoxins?
Produced by Gram -ve and are a PAMP which causes innate immune response activation. Leads to sepsis
What causes mutation of influenza virus?
Antigenic DRIFT, the accumulation of minor mutations for cell surface proteins.
What is antigenic shift?
Mixing of genes of viruses from different species.
What is the role of integrase?
Facilitate insertion of the viral DNA into the DNA of the host cell
Which antibiotic affects liver enzymes?
Macrolide antibiotics like Erythromycin which inhibits cytochrome p450
Which type of E.Coli causes intestinal perforation?
Salmonella enterica typhoid fever, can progress to intestinal perforation
Which drugs can be removed via efflux pumps?
Tetracyclines and fluoroquinolones
What are the side effects of gentamycin?
Nephrotoxicity and ototoxicity
What are the features of clostridium tetani?
Gram positive bacilli which produces the exotoxin to inhibit renshaw cells in the spinal cord.
What is clarithromycin?
Macrolide antibiotic which inhibits 50s ribosomes and has a bacteriostatic effect.
Resistant antibiotics will have ribosome splicing.
What is ciprofloxacin?
Inhibits DNA gyrase
What is clinamycin?
50s ribosomal subunit inhibitor.
How does mRSA works?
Altered drug binding site.
How does clostridium botulinum work?
It is a gram positive bacilli.
Produces the botulinum toxin which causes paralysis of motor and autonomic nerves from the head down. It begins with paralysis of the cranial nerves.
What is clostridium perfingens?
Gram positive bacilli which causes acute diarrhoea and stomach cramps. This starts 6-24 hours after eating contaminated food and lasts less than 24 hours.
What is Scabies?
Infection by mite which releases proteolytic enzymes and burrows into the epidermal layer of the skin.
Cause a delayed type 4 hypersensitivity reaction of pruiritis which is worse at night.
Where does herpes virus lie dormant?
Dorsal root ganglion
Cranial nerve ganglion
Reactivated during times of stress or immunosuppression
What is proteus miribalis?
Gram negative bacilli found in SOIL AND WATER which causes UTI and pyelonephritis
What is staphylococcus saprophyticus?
UTI in sexually active young women
Cauase of recurrent UTI?
Structural abnormality of urinary traf
