Microbiology Flashcards
Ribosomes in eukaryotic cells
80s
What is bacterial cell wall made up of
Peptidoglycan
Gram +vs vs -ve cell wall
Gram positive have thick cell wall, retain crystal violet
What are lipopolysacchardies
Endotoxins. Present in outer membrane of gram negative bacteria
What makes up bacterial flagella
Flagellin, a globular protein
What is a biofilm
Biofilm is a group of organisms in which cells stick to one another and to the surface
Prokaryotes that can survive body temperature
Mesophils - Body temperature
Psycrophiles - Low temperature
Thermophiles - High temperature
Aerobes, Microaerophiles, Facultative anaerobes, Obligate anaerobes
Aerobe - Survive and grow in oxygen
Microaerophils - Poisoned by high oxygen levels
Facultative anaerobes - Survive with/without Oxygen
Obligate anaerobes - Poisoned by Oxygen
What does the bacterial growth curve consist of
Lag phase, Exponential phase, Stationary phase, Decline phase
Streptococci vs Staphylococci
Streptococci - Division to produce chains
Staphylococci - Division to produce clumps
What are vibrio bacteria
Gram negative, slightly curved rod shaped
Ex: Vibrio cholerae
Spirillium vs Spirochaete
Spirillium are aerobes, with a rigid cell wall. They move by means of a flagella. Spirochaete are flexible spiral bacteria, move in a corkscrew motion
Gram stain colours
Gram positive - Purple due to think cell wall
Gram negative - Pink
What is selective media
Presence of specific substance permits the growth of one organism over the other
What is differential media
Incorporation of chemicals produces visible change colonies that facilitate identification
What are serological tests
Serological tests use antibodies released in response to antigens. Detects IgM antibody
Polyclonal vs monoclonal
Antibody specific to microbe/virus = Polyclonal
Antibody specific to one component = Monoclonal
What is MALDI-TOF not very effective against
Streptococci and Staphylococci
What is virulence
Capacity of a microbe to cause damage to the host
What is opportunistic pathogen
A pathogen that causes infection when the opportunity arise, eg: immunocompromised individuals
Major protozoan disease
Malaria
Common gram positive pathogens
Streptococcus Staphylococcus Enterococcus Clostridium Fusobacterium
Infectious gram negative cocci
Neisseria meningitidis - Bacterial meningitis
Neisseria gonorrhoea - STI
What are coliforms
Gram negative facultative aerobes that look like Escherichia coli on gram film
First line antibiotic for coliforms
Gentamicin
What are O and H antigens
O antigens are from bacterial cell walls, H from flagella
What are endotoxins?
Outer membrane of gram negative bacteria, elicit an immune response form host body by binding to macrophage and B cells and stimulating release of acute phase cytokines, SIRS or endotoxin shock
How do endotoxins produce fever
Lipopolysaccharides interact with macrophages. This releases cytokines into the bloodstream, travelling to the anterior hypothalamus. Prostaglandin E is released which increases the bodys thermal set point. Body perceives its cold and starts to shiver, inducing a fever
What gram positive bacteria is nosocomial and community acquired
Staphylococcus
How can Streptococcus be differentiated
Haemolysis
Alpha - Partial, green colonies, S.pneumoniae
Beta - Complete, yellow colonies, S.milleri
Gamma - No haemolysis, Enterococci
Associated diseases with group A streptococci
Scarlet fever
Severe sore throat
Necrotising fasciitis
Called GAS - Harbour Lancefield group A antigen
First line treatment for infections by anaerobes
Metronidazol
Commonest cause of urinary tract infections
Enterococci - Gamma haemolysis
When can S.epidermis cause infections
Nosocomial infection - foreign devices like catheter
Immunocompromised
When does Clostridium sp. cause infections
Elderly
Antibiotic abuse
Changes in gut flora
What can cause Pseudomembranous collitis
Clostridium difficile, can lead to diarrhoea
Steps of a viral infection
Attachment, Entry, Uncoating, Nuclei acid and protein synthesis, Assembly, Release
How are enveloped viruses released
Released by budding, unenveloped by lysis
What structure does Erythromycin target
Bacterial ribosome
What is rational drug design
Use of detailed molecular analysis of viral targets to design a molecule that might inhibit its function. Better than blind testing.
How can antiviral resistance be checked for
Analysed genotypically rather than phenotypically
Example of viral infection causing malignancy
Human Papilloma Virus - Cervical cancer
Hepatitis B and C - Hepatocellular cancer
Cytotoxic T lymphocytes and virus infection
Can recognise proteins on cell surface as foreign and signal infected cell to undergo apoptosis
Antibodies in viral infection
Neutralising antibodies (IgM, IgG) can prevent virus binding to cellular receptors
Detecting antibody or virus itself?
Detecting the virus itself is faster than waiting for antibody levels to rise
Bacteriostatic vs Bacteriocidal
Inhibit growth of bacteria vs Kill bacteria
Peak serum levels oral vs IV
Oral = 1 hour, IV = 15 mins
What are persister cells
Persister cellsare bacterialcellsthat survive killing by antibiotics that block synthesis of peptidoglycan or DNA, but remain sensitive to that antibiotic upon being regrown and give rise to the same small fraction ofpersisters.
How can resistant bacteria transfer their gene with one another
Natural competence, bacteriophage or sex pili
Cross resistance vs multiple resistance
Cross resistance - Closely related antibiotics
Multiple - Unrelated antibiotics
Beta-lactamases
Penicillinase - Resistant to early penicillin such as amoxicillin
Extended Spectrum Beta-Lactamase (ESBL) - Resistant to all penicillins and upto 3rd generation Cephalosporins
Carbapenamase (CPE) - All penicillins, Cephalosporins, Carbapenems
Last line treatment for New Delhi Metallo B-Lactamase 1 (NDM-1)
Colistin, same side effects as Vancomycin, kidney damage (nephrotoxic) and deafness
What drug replaced Methicillin
Flucloxacillin
How does genetic resistance come about in a bacterial population
Genetic variation results in bacteria becoming resistant to antibiotics. This genetic material that confers resistance is exchanged due to bacteria living in close proximity via sexual pili
Microorganisms with threat levels of urgent
Clostridium difficile
Enterobacteriaceae
Neisseria gonorrhoea
How can chain of infection be broken
Sterilisation/disinfection
Isolation/PPE
Decontamination
Vaccination
How can infection spread
Inhalation Ingestion Inoculation Mother to Infant Intercourse
What colour bag is for clinical waste
Orange, black for domestic waste
Are small or large respiratory droplet harmful
Small as they evaporate to droplet nuclei which stay suspended in air currents for hours
What kind of rooms are effective airborne precaution
Negative pressure room
What is disinfectant
Process by which number of microorganisms are reduced to a safe level, some spores, viruses remain
What chemicals are used for living tissue
Antiseptic and not disinfectant
What is sterilisation
Process by which all microorganisms are removed to render object incapable of causing infection
What is autoclave
High pressure, high temperature for 3 mins to sterilise
