Microbiology Flashcards
What are the 5 main groups of human pathogens?`
Bacteria, fungi, protozoa, prions, viruses
What are pathogens which are eukaryotic, single celled animals which are generally hard to treat?
Protozoa
What are fungi?
Higher, plant like organisms, eukaryotes
What are bacteria?
Generally small, single celled organisms, prokaryotes
What are very small, obligate parasites which are non-living?
Viruses
What are non-living proteins that cause infection?
Prions
Which are bigger, eukaryotes or prokaryotes?
Eukaryotes
Which are usually multicellular, eukaryotes or prokaryotes?
Eukaryotes
What is the chromosome organisation in eukaryotes?
Linear chromosomes and histones
What is the chromosome organisation in prokaryotes?
Single circular chromosomes
What, with regards to gene structure, do eukaryotes possess that prokaryotes don’t?
Introns
What is of importance about the cell membrane in prokaryotes?
It is the only membrane a prokaryote contains
What do some, but not all, prokaryotes possess to aid movement?
Flagellum
Apart from a flagellum, what else do some prokaryotes have and others don’t?
External capsule
What is contained in the nucleoid of prokaryotes?
DNA and proteins
What does the prokaryotic nucleoid not have?
A membrane
What does DNA replication occur via in prokaryotes?
DNA dependent RNA polymerase
What are transcription and translation in prokaryotes?
Co-ordinated
What is an example of an extra chromosomal replicon which can also exist in prokaryotes?
Plasmid
What is released in the cytoplasmic membrane of prokaryotes?
Electrons
What is found across the membrane of prokaryotes?
+ charge and a proton gradient
Where do processes which would normally occur elsewhere (such as the mitochondria) occur in prokaryotes?
Cytoplasmic membrane
What is the structure of the prokaryotic cell wall?
Rigid, repeated polysaccharide structure
What is the gram + cell wall?
Thick, multi layer of peptidoglycan
What is the gram - cell wall?
Formed of an outer membrane, periplasm and thin single layer of peptidoglycan
What is the main component of the outer layer of the gram - cell wall?
Lipopolysaccharide
What are the fimbriae/pilus which are found on the outer surface of bacteria sometimes?
Hair like appendages, similar to cilia
Where does protein synthesis occur in prokaryotes?
Plasma membrane
Describe the run of prokaryotic protein synthesis?
Gene, mRNA, tRNA, protein, 2nd, 3rd, 4th structure, export, assembly, processing
Where occurs between the gene and mRNA stages of protein synthesis in prokaryotes?
Transcription
What occurs between the tRNA and protein stages of protein synthesis in prokaryotes?
Translation
What factors are required for prokaryotic growth?
Food, temperature, pH, osmotic protection, oxygen
What are food sources for prokaryotes?
C, H, O, N, vitamins, trace elements
What are mesophiles?
Body temperature orientated bacteria
What is the optimum pH range for bacteria which infect humans?
6.8-7.2
What is the optimum osmotic protection for bacteria which infect humans?
0.85% NaCl
What are microaerophiles?
Need oxygen for respiration but are killed at high concentrations
What are facultative anaerobes?
Can go with or without oxygen
What are obligate anaerobes?
Get killed at even low oxygen concentrations
What can microorganisms be classified depending on?
Appearance/structure, growth requirements, enzyme/molecular/metabolic tests
What is an example of a cocci that can divide in 1 plane to produce 2 cocci?
Diplococcus
What is an example of a cocci that can divide in 1 plane to form a chain of 4-20 cocci?
Streptococcus
What is an example of a cocci that can divide in 3 planes to produce a clump of cocci?
Staphylococcus
What are examples of different types of bacilli?
Generally rod shaped, can be chains, spirals (rigid or flexible) or curved
What gram are curved bacilli?
Negative
What media is used for gram staining?
Eosin and methylene blue
What colour is gram negative bacteria on a gram stain?
Pink
What colour is gram positive bacteria on a gram stain?
Purple
What are examples of diseases which have bacteria that do not gram stain well?
TB and syphilis
What is aerobic bacteria?
Grow in oxygen
What are obligate anaerobes?
Killed by oxygen
What are obligate aerobes?
Require oxygen
What are facultative anaerobes?
Tolerate oxygen
What bacteria is identified by haemolysis?
Streptococcus
What does alpha haemolysis show?
A green colour, partial haemolysis
What are examples of alpha haemolytic strep?
Strep pneumoniae and viridans
What does beta haemolytic strep show?
A clear colour, complete haemolysis
What is an example of group A beta haemolytic strep?
Strep. pyogenes
What is an example of group B beta haemolytic strep?
Strep. agalactiae
What does gamma haemolysis show?
No haemolysis
What is an example of gamma haemolytic strep?
Enterococcus
What is MALDI-TOF?
A powerful, rapid, precise and cost effective test for bacteria
What is MALDI-TOF not so good for?
Strep and staph
What is virulence?
The capacity of a microbe to damage a host
What is an endogenous microorganism?
Bacterial flora within a closed space
What is an exogenous microorganism?
Not normal flora
What is commensal bacteria?
An endogenous organism with a mutualistic effect
What is an opportunistic pathogen?
One which causes infection when opportunity or a change in natural immunity arises
What is aspergillus.spp?
A fungal infection which occurs in immunocompromised
What is candida.spp?
A fungus from a skin infection
What are some examples of protozoan infections in man?
Malaria/toxoplasma/some GI infections
What are some common gram -‘s?
Klebsiella, enterobacter.spp, salmonella.spp, haemophilus. spp, bacteroides
What are some common gram +’s?
Streptococcus.spp, staphylococcus.spp, enterococcus.spp, clostridium
What are E.coli, Klebsiella, Enterobacter, Proteus?
Common gut commensals
What are salmonella, shigella, verotoxin?
Significant gut pathogens
What are coliforms?
A species of gram - bacilli which look like E-coli
How do coliforms grow best?
Aerobically
What happens when a coliform gets into a usually sterile site?
It will cause serious infection
What are examples of infections caused by coliforms?
UTI, peritonitis, biliary tract infection
How are coliform infections best treated?
Gentamicin
What does the outer membrane of gram - bacteria bind to?
Macrophages, B cells and more
What does gram - bacteria binding to inflammatory cells do?
Stimulates release of acute phase cytokines
What does the release of acute phase cytokines cause?
Endotoxin shock, systemic inflammatory response syndrome
What molecule increases the body’s thermal set point to cause fever?
Prostaglandin E
What is fever defined as?
Greater than 38 degrees
What are examples of strict aerobic gram - bacilli?
pseudomonas aurigunosa, legionella pneumophilia
What are vibrio cholerae, campylobacter. spp, helicobacter. pylori?
Spiral/curved gram - bacilli
What is a small gram - cocco bacillus?
Haemophilus influenzae
What is strep. pneumoniae?
Gram + alpha haemolytic cocci
What gram stain is staph aureus?
Positive
What gram stain is staph epidermis?
Negative
What is staph epidermis associated with?
Foreign devices e.g. catheter
What is clostridium spp?
Gram + anaerobic bacilli
What does clostridium produce and what does this cause?
Endotoxins which cause severe tissue damage
What in terms of nucleic acid do viruses possess?
DNA or RNA but never both
What surrounds the protein coat in some viruses and where does this come from?
Envelope- derived from the host cell
What does icosahedral symmetry mean?
A virus is made up of repeated subunits- they are full of lots of information but few genes
What does helical symmetry mean?
Made up of a single repeated unit so it only has to code for 1 protein
What are the 6 steps of virus infection?
Attachment, entry, uncoating, protein synthesis, assembly, release
How can viruses enter cells?
Through the envelope fusing with the cell membrane or endocytosis in viruses without an envelope
The action of what aids uncoating of viruses?
Viral ion pumps
What are antimicrobials?
Drugs used to treat all types of infection, not just bacteria
What will recognise proteins on the viral cell surface and signal the infected cell to commit suicide to prevent spread of the virus?
Cytotoxic T cells
What prevents viruses binding to more cellular receptors?
Neutralising antibodies
What are examples of viruses which can reactivate?
Varicella Zoster or Herpes simplex virus
What are examples of chronic viral infections which remain inactive for years?
HIV/Hepatitis C
What will previous viral infections show that new ones won’t?
IgG antibodies from immunological memory
What are current viral detection agents?
PCR, antigen detection
What are the 3 main ways that viruses exert pathogenesis?
Lysis or hijacking of cell material, cell proliferation or through cytotoxic T cells
What do bacteriostatic antibiotics do?
Inhibit growth of bacteria
What do bacteriocidal antibiotics do?
Kill bacteria
How can antibiotics be excreted?
Either in the urine or through the liver, biliary tract and faeces
What is the advantage of using IV antibiotics over oral?
They will reach peak serum levels quicker
What are some targets of antibiotics?
Cell wall, ribosomes, DNA replication, DNA gyrases, metabolic pathways, cell membrane function
What type of antibiotics target the cell wall?
Beta-lactams and glycopeptide antibiotics
What are examples of beta-lactam antibiotics?
Penicillin, amoxicillin, flucloxacillin, co-amoxiclav, ceftriaxone, carbapenems
What is an example of a glycopeptide antibiotic?
Vancomycin
What does vancomycin have no activity against?
Gram -
What is a penicillin targeting gram +?
Flucloxacillin
What are penicillins targeting gram + and -?
Amoxicillin, co-amoxiclav, tazocin
What is a penicillin targeting gram -?
Temocillin
How are penicillins excreted?
Via kidneys
Are penicillins safe in pregnancy?
Yes
What is flucloxacillin used for?
Staph and strep only
Why is the use of cephalosporins limited?
They kill normal gut flora and can cause gastroenteritis
What are examples of antibiotics which target protein synthesis?
Aminoglycosides e.g. gentamicin and tetracyclines e.g. doxycyline
When should you not use doxycycline?
Infants, children and pregnancy
What are examples of macrolide antibiotics?
Erythromycin, clarithromycin
How are macrolides excreted?
In the liver
Where do antibiotics such as metronidazole, fluoroquinones and rifampicin target?
Nucleic acid synthesis
What are common side effects of all antibiotics?
Nausea, vomiting, diarrhoea- may also affect absorption of oral contraceptives
What are side effects of gentamycin?
Renal and CNVIII damage
What is an effect of metronidazole?
Interacts with alcohol
What do broad spectrum antibiotics increase the risk of?
C. diff infections, especially in the elderly
What are 3 reasons for antibiotics being given in combination?
- Cover a wide range of organisms
- Prevent development of resistance
- Create a synergistic effect
What antibiotics should never be given in combination?
A bacteriostatic and bacteriocidal antibiotic
What are the ‘4C’ antibiotics which should be avoided?
Cephalosporins, co-amoxiclav, ciprofloxacin, clindamycin
What are some examples of natural resistance?
Target not present or accessible, developmental structure, metabolism
What are biofilms?
Organisms behaving as part of a multi-cellular community
What is resistance?
Drug is no longer active against an entire population of cells
What can resistance occur because of?
Mutation, selection pressure and evolution, horizontal gene transfer
What is the difference between cross resistance and multiple resistance?
Cross resistance means that resistance came about through a single mechanism and multiple resistance means it took many
