Microbiology Flashcards
Define nucleocapsid
The capsid most closely associated with the viral nucleic acid.
Nucleic acid + capsid
What is the size of a virus?
0.02 - 0.04 um
= 20 - 40 nm
Define virion
The virus particle
What does a high lymphocyte count indicate?
Viral infection
Define the viral envelope
Lipid membrane surrounding either the capsid or nucleocapsid that is formed by the host cells’ membrane (not present in all viruses)
What do naked viruses lack?
An envelope
Define capsid
The protective protein coat shell around the viral genome and forming the core of the virus particle
What are the 2 main differences between the gram positive and the gram negative bacterial cell wall?
Gram negative bacteria have a smaller/thinner peptidoglycan layer and they have an additional outer/superficial plasma membrane.
What type of bacteria is this?
Spirochete
What is the funciton of the bacterial flagella?
Locomotion
What type of bacteria is this?
Diplococci
What are the 3 main components of the bacterial peptidoglycan cell wall?
N-acetyl-glucosamine, N-acetyl-muramic acid and a short peptide chain
What shape is a bacillus bacteria?
Rod
What are 3 functions of the bacterial capsule?
increases virulence
protects against phagocytosis
prevents dehydration..
What type of bacteria is this?
Streptococci
What is the size of a bacterium?
1-2 um
What type of bacteria is this?
Diplobacillus
What type of bacteria is this?
Streptobacilli
What shape is a coccus bacteria?
Spherical
In the peptidoglycan wall of the bacterium, how are the peptide chains connected?
Pentapeptide bridges
What are the 3 most common sites of microbe entry?
The GI tract, skin and respiratory tracts
Define cellulitis
An infection of the deep layers of the skin and subcutaneous tissues by bacteria
An offensive smelling wound suggests what?
Infection by anaerobic bacteria
What type of bacteria release endotoxin?
Gram-negative bacteria
What does the catalse test assess?
Tests whether microbe can break down hydrogen peroxide: 2H2O2 → 2H2O + O2
What does the coagulase test assess?
Tests whether the microbe can clot plasma by converting fibrinogen to fibrin
What is CHA medium?
Chocolate horse blood agar: same as HBA but heated to lyse RBCs and release nutrients
What type of haemolysis is clear haemolysis?
Beta haemolysis
What type of haemolysis is greening haemolysis?
Alpha haemolysis
What colour will beta haemolysis create?
Clear
What colour will alpha haemolysis create?
Green
What is MacConkey agar enriched with?
Bile salts
Bright pink appearance on a MAC plate indicates what?
Lactose fermenter
Pale appearance on a MAC plate indicates what?
Non-lactose fermenter
Where do RNA viruses generally replicate?
in the cytosol
When are non-enveloped viruses released from a host cell?
When the host cell lyses
What do we call the period between a virus infecting a cell and the intracellular number of viruses rising?
Eclipse period
What must a negative strand viruses bring preformed with it when it infects a cell?
RNA-dependent RNA polymerase
What are the 2 ways a virus may penetrate a cell?
1 Fuse with the plasma membrane
2 Use receptor mediated endocytosis
What do we call the period between a virus infecting a cell and extracellular viruses appearing?
Latent period
What do all viruses need to replicate?
plus sense RNA
What type of infection is it called when a virus infects a cell, but does not harm the cell and only emerges at a later time as a lytic infeciton
Latent infection (eg herpesvirus)
Varicella-zoster, Epstein-Barr and cytomegalovirus are all examples of what ‘family’ of viruses?
Herpesvirus
What is the most important/common route of entry for viruses intot he human body?
Respiratory system
What type of symetry does the capsid of all non-enveloped viruses have?
An icosahedral structure.
What type of infection is it where a virus infects a cell and slowly releases virus particles without killing the host cell?
Chronic infection
What do virus-infected cells release to prevent neighbours from replicating thus protecting them from infection?
Interferons
Where are structural virus-encoded proteins translated?
Ribosomes in the cytoplasm of the host cell
Which protein does a virus needs to replicate, which humans don’t have?
RNA-dependent RNA polymerase
Name 2 ways an enveloped virus can leave the host cell
1 Budding off from cell plasma membrane
2 Golgi-formed vesicles are exocytosed
Where do DNA viruses generally replicate?
In the nucleus
Which helminth can grow up to 30-40 cm?
Ascaris lumbricoides
What symptoms do scabies cause?
Intense itchiness and dermatitis
What is the only helminth that can complete its life cycle in a human host?
Strongyloides
What is a roundworm known as?
Nematode
Where may Giardia lamblia live in humans?
Duodenum
What are helminths known as?
Worms
Which organ does entamoeba histolytica typically invade?
Colon
Name two helminths that can infect humans directly though the skin
Schistosoma mansoni
Strongyoides stercoralis
What is the pathogen in head lice?
Pediculis capitis
What is the pathogen in scabies?
Sarcoptes scabiei
What is the pathogen in pubic lice?
Phthirus pubis
Which parts of the body do scabies like to infect?
Fingerwebs, elbows, axillae, genitals
Which is the most comon disease-causing amoeba in humans?
Entamoeba histolytica
Host in which development occurs but the parasite does not reach sexual maturity. How is this descibed?
Intermediate host.
What is a very common non-human host of toxoplasma gondii in Australia?
Cats
What is enterobius vermicularis better known as?
Pin worm
Whihc tick is the pathogenic agent in rapid ascending paralysis?
Ixodes holocyclus
What is lice infection generically known as?
Pediculosis
Name two type of adhesins used by bacteria
Fimbriae and intimin
How do helminths respire?
Through their skin
In which countries are schistosoma mansoni likely to be acquired?
Africa, South America, Carribean
How many people in the world are infected with a helminth?
>1 billion
What effect does vancomycin have on microbiota?
Vancomycin decreases diversity of microbiota, which may be enduring
How does strongyloides stercoralis infect a human?
Through skin
How does scabies spread?
Direct skin to skin contact
Which helminth causes hydatid cysts?
Echinococcus granulosus
What do we call the host in which the parasite reaches sexual maturity?
Definitive host
What is the pathogen in body hair lice?
Pediculus humanis
How is infection with schistosoma mansonii acquired?
Exposure to infected fresh water
Which helminths are known to sit in the gut, consume energy and cause weight loss?
Tapeworms
What is a very severe complication of tick infection?
Generalised rapid ascending paralysis
Where do ectoparasites live?
On or near dermal surface
Which type of helminths cause neurocystercercosis?
Taeniae
Define parasite
A plant or animal…
that lives on or in another living organism….
on which it is metabolically dependent
Where do body louse lay their eggs?
Clothing
What is the classical pathology caused by taenia solium?
Neurocystercercosis
Which two bacteria predominate in the gut microbiota?
Fimicutes and bateroidetes
Which generations of cephalosporin are better for gram negative bacteria?
Later generations
How long must a mosquito have malaria before it can transmit it to a human?
2 weeks
What are 4 disadvantages of killed vaccines?
Weaker immune response
High dose
Need adjuvants
Expensive
What is pyocyanin?
Turquoise pus produced by eg pseudomonas aeruginosa
What is the significance of Ps. aeruginosa being non-fermenting and non-sporing?
It has low nutritional requirements
What is the form of malaria that a mosquito may infect a human with?
Sporozoite
What stage of the malaria lifecycle is released from hepatocytes?
Merozoite
What is the antibiotic of choice for MRSA?
Vancomycin
Which type of malaria causes the majority of severe malaria and death?
Plasmodium falciparum
What does nosocomial epidemic mean?
Institutional epidemic (eg hospital, nursing home, school)
What type of bacteria is pseudomonas aeruginosa? Gram pos/neg, coccus/rod
Gram negative rod
What is the main weapon of the immune system in targeting the blood stage of malaria?
Antibodies
With diurnal variation, when is temperature lowest?
Morning
What are the clinical features of cerebral malaria?
Impaired consciousness, coma, convulsions and long term neurological sequelae
What is the single most important preventative technique for opportunistic infections?
Hand hygiene
What is the optimum temperatture for immune, endocrine and phsyiological mechanisms?
39.5 C
What is group A strep also known as?
Strep pyogenes
What oral temperature defines a fever in the morning?
37.2
What is the difference between oral temperature and core body temperature?
Oral less than core temp by 0.5C
What oral temperature defines a fever at any time of day?
37.8
Malaria is most common in people who are travelling for what reason?
Visiting friends or family
How long does malaria incubate in the liver for?
7-10 days
What is the difference between axillary temperature and core body temperature?
Axillary temp < core body temp by 1C
What does saprophytic mean?
An organism can obtain nutrients from dead organic matter
What stage of the malaria lifecycle will infect RBCs?
Merozoite
What are the two main types of malaria?
Plasmodium falciparum and plasmodium vivax
At what stage of the life cycle is the malaria protozoa when it infects hepatocytes?
Sporozoite
Which bacteria will often infect a burn in hospital?
Staph aureus
What is a fomite?
An inanimate object capable of carrying microorganisms eg stethoscope
If someone presents with an acute fever, what are some warning signs of a more serious underlying illnes?
Rigors, rapid evolution, severe muscle pains, impaired conscious state, vomiting, severe headache, rash, jaundice, hypotension, cyanosis, tachypnoea
By what process does pseudomonas aeruginosa turn on/off many genes when in a biofilm?
Quorum sensing
What are the symptoms of mild malaria?
Flu like illness with fever, headache and malaise
Travelling to what part of the world will give you the highest chance of developing traveller’s diarrhoea?
South Asia
With diurnal variation, when is temperature highest?
Afternoon
Which types of malaria can be transmitted from human to human?
NONE
What is the most common mode of disease transmission in a traveller?
Vector borne
What are the 3 criteria for pyrexia of unknown origin?
Prlonged illness (2-3 weeks duration)
Fever > 38.3 on several occasions
No Dx after intelligent Ix
Where does pseudomonas aeruginosa love to grow?
In moist environments
What is the normal oral temperature range?
35.8-37.8
What are 3 disadvantages of living vaccines that can cause disease?
Back mutation
Spread
Contamination
What symptoms are evident during the liver stage of malaria?
None
What is the most common preventable medical condition in travellers?
Influenza
Which is closer to core body temperature: oral, axillary or ear?
Ear
What is the main weapon of the immune system in targeting the liver stage of malaria
Cytotoxic T cells
Which type of malaria is most common in sub-Saharan Africa?
Plasmodium falciparum
What are 4 advantages of killed vaccines?
Stable
Contamination unlikely
Can’t spread
Safe for immunodeficient
Which nucleus of the hypothalamus controls temperature set point?
Pre-optic
What are 3 advantages of living vaccines?
Broader immune response
Local immunity
Ease of administration
Which type of malaria is most common in central/South America and south east Asia?
Plasmodium vivax
Which generations of cephalosporin are better for gram positive bacteria?
Earlier generations (and 4th generation)
What is the antibiotic of choice for staph aureus?
Flucloxacillin
