Microbiology Flashcards
What five categories can bacteria fall into
They can be categorised into aerobic and anaerobic, gram positive and gram negative and atypical bacteria.
Difference between Gram negative and Gram positive bacteria
Gram positive bacteria have a thick peptidoglycan cell wall that stains with crystal violet stain. Gram negative bacteria don’t have this thick peptidoglycan cell wall and don’t stain with crystal violet stain but will stain with other stains
What are the two shapes of bacteria
Cocci (circular) or Bacilli (rods)
Pathway to create folic acid inside the bacterial cell
PABA is absorbed across the cell membrane and is then converted to DHFA which is then converted to THFA and then to folic acid
Explain gram staining
Add a crystal violet stain which binds to molecules in the thick peptidoglycan cell wall in gram positive bacteria turning them violet.
Then add a counterstain (such as safranin) which binds to the cell membrane in bacteria that don’t have a cell wall (gram negative bacteria) turning them red/pink.
Name three Gram positive Cocci
Staphylococcus, Streptococcus and Enterococcus
Name the Gram-Positive Rods
Use the mnemonic “corney Mike’s list of basic cars”:
Corney – Corneybacteria
Mike’s – Mycobacteria
List of – Listeria
Basic – Bacillus
Cars – Nocardia
Name the four Gram positive Anaerobes
Use the mnemonic “CLAP”:
C – Clostridium
L – Lactobacillus
A – Actinomyces
P – Propionibacterium
Name 5 Gram negative bacteria
Neisseria meningitis
Neisseria gonorrhoea
Haemophilia influenza
E. coli
Klebsiella
Pseudomonas aeruginosa
Moraxella catarrhalis
Define atypical bacteria
The definition of atypical bacteria is that they cannot be cultured in the normal way or detected using a gram stain. Atypical bacteria are most often implicated in pneumonia.
Name the atypical bacteria
The atypical bacteria that cause atypical pneumonia can be remembered using the mnemonic “legions of psittaci MCQs”:
Legions – Legionella pneumophila
Psittaci – Chlamydia psittaci
M – Mycoplasma pneumoniae
C – Chlamydydophila pneumoniae
Qs – Q fever (coxiella burneti)
What does MRSA stand for
Methicillin-Resistant Staphylococcus Aureus
What has MRSA become resistant to
resistant to beta-lactam antibiotics such as penicillins, cephalosporins and carbapenems
What can be used to eradicate MRSA in hospital to stop its spread
Chlorhexidine body washes and antibacterial nasal creams
Name 3 antibiotic options for MRSA
Doxycycline
Clindamycin
Vancomycin
Teicoplanin
Linezolid
What are ESBL’s
Extended Spectrum Beta Lactamase bacteria
ESBLs are bacteria that have developed resistance to beta-lactam antibiotics. They produce beta lactamase enzymes that destroy the beta-lactam ring on the antibiotic. They can be resistant to a very broad range of antibiotics
What bacteria tend to be ESBL’s
E.coli and Klebsiella - tend to cause UTI’s but can also cause other infections such as pneumonia
What would you use to treat ESBL’s
They are usually sensitive to carbapenems such as meropenem or imipenem.
What are the two ways Antibiotics can work?
They work in various ways to either stop the reproduction and growth of bacteria (bacteriostatic) or kill the bacteria directly (bactericidal)
What antibiotics attack the bacteria cell wall
Penicillin, Carbapenems (e.g. imipenem), vancomycin, Teicoplanin and Cephalosporins (e.g. cephalexin, cefuroxime or ceftriaxone)
What antibiotic inhibits the conversion of DHFA to THFA
Trimethoprim
What antibiotic inhibits the conversion of PABA to DHFA
Sulfamethoxazole
What antibiotics inhibit protein synthesis by targeting ribosomes
Macrolides such as erythromycin, clarithromycin and azithromycin
Clindamycin
Tetracyclines such as doxycycline
Gentamicin
Chloramphenicol
What type of bacteria can metronidazole treat and why?
The reduction of metronidazole into its active form only occurs in anaerobic cells. When partially reduced metronidazole inhibits nucleic acid synthesis. This is why metronidazole is effective against anaerobes and not aerobes.