Bacteria Flashcards
(24 cards)
How can bacteria be categorised?
aerobic and anaerobic, gram positive and gram negative and atypical bacteria.
Different characteristics of the bacteria.
Aerobic bacteria require oxygen whereas anaerobic bacteria do not. 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. Atypical bacteria cannot be stained or cultured in the normal way.
What is a bacilli?
Rod shaped bacteria
What are cocci?
Circular shaped cocci
Cell wall function in bacteria?
The cell wall is a structure that surrounds the outer cell membrane and is found on gram positive bacteria.
Nucleic acid function in bacteria?
Nucleic acid is essential component of bacterial DNA.
Ribosome function in bacteria?
Ribosomes are where bacteria proteins are synthesised within the bacterial cell.
Folic acid function in bacteria?
Folic acid is essential for synthesis and regulation of DNA within the bacteria. Folic acid cannot be created or directly imported into the cell and requires a chain of intermediates to get in to the cell. This chain starts with PABA, which is directly absorbed in to the cell across the cell membrane. PABA is then converted to DHFA which is converted inside the cell to THFA then folic acid.
What is a gram stain?
A gram stain is used as a quick way to check a sample under the microscope to look for bacteria.
What are the 2 steps of a gram stain?
- Add a crystal violet stain - 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.
Gram positive cocci
- Staphylococcus
- Streptococcus
- Enterococcus
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
Gram positive anaerobes
Use the mnemonic “CLAP”:
C – Clostridium
L – Lactobacillus
A – Actinomyces
P – Propionibacterium
Gram negative bacteria
Common gram negative organisms are:
Neisseria meningitis Neisseria gonorrhoea Haemophilia influenza E. coli Klebsiella Pseudomonas aeruginosa Moraxella catarrhalis
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)
Atypical bacteria definition?
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.
MRSA
MRSA refers to staphylococcus aureus bacteria that have become resistant to beta-lactam antibiotics such as penicillins, cephalosporins and carbapenems.
Where is MRSA normally a problem?
They are a problem in healthcare settings where antibiotics are commonly used. Think about MRSA in patients that have had hospital admissions or come from a nursing home or other healthcare institution.
How can you eradicate MRSA
Eradication usually involves a combination of chlorhexidine body washes and antibacterial nasal creams.
What is the importance of MRSA in relation to surgery?
People are often colonised with MRSA bacteria and have them living harmlessly on their skin and respiratory tract. If these bacteria become part of an infection they can be difficult to treat. Patients being admitted for surgery or treatment are screened for MRSA infection by taking nasal and groin swabs so that extra measures can be taken to try to eradicate them and stop their spread.
MRSA treatment options
Antibiotic treatment options for MRSA are:
Doxycycline Clindamycin Vancomycin Teicoplanin Linezolid
ESBLs
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.
ESBLs examples
ESBLs tend to be e. coli or klebsiella and typically cause urinary tract infections but can also cause other infections such as pneumonia.
How to treat ESBLs
They are usually sensitive to carbapenems such as meropenem or imipenem.
