Bacteria Flashcards
What are bacteria and how are they categorized?
Bacteria are single-celled organisms that can be classified into:
* Aerobic (require oxygen)
* Anaerobic (do not require oxygen)
* Gram-positive (thick peptidoglycan wall)
* Gram-negative (thin peptidoglycan wall)
* Atypical bacteria (cannot be stained or cultured in the usual way)
What are the different shapes of bacteria?
Bacteria can have the following shapes:
* Bacilli – rod-shaped bacteria
* Cocci – circle-shaped bacteria
Shape identification is crucial for bacterial classification and diagnosis.
How do antibiotics work on the bacterial cell wall?
Antibiotics that target the bacterial cell wall can either have a beta-lactam ring (e.g., penicillins, cephalosporins) or no beta-lactam ring (e.g., vancomycin). These antibiotics inhibit the synthesis of the cell wall, which is crucial for bacterial survival.
The effectiveness of antibiotics often depends on the structural differences in bacterial cell walls.
How does Metronidazole work as an antibiotic?
Metronidazole works by inhibiting nucleic acid synthesis in bacteria, disrupting their ability to replicate.
This mechanism makes it effective against anaerobic bacteria and certain protozoa.
Which antibiotics target bacterial ribosomes to prevent protein synthesis?
Antibiotics targeting the bacterial ribosomes include:
* Macrolides (e.g., clarithromycin)
* Tetracyclines (e.g., doxycycline)
* Aminoglycosides (e.g., gentamicin)
These antibiotics interfere with the translation process, essential for protein production in bacteria.
What is the role of folic acid in bacterial DNA synthesis and which antibiotics interfere with it?
Folic acid is necessary for bacterial DNA synthesis. Antibiotics can disrupt this process:
* Sulfamethoxazole blocks the conversion of PABA to DHFA
* Trimethoprim blocks the conversion of DHFA to THFA
Targeting folic acid synthesis is a common strategy in antibiotic therapy.
How does the Gram stain differentiate between bacteria?
Gram-positive bacteria retain the crystal violet stain and appear violet due to their thick peptidoglycan cell wall.
Gram-negative bacteria do not retain the crystal violet stain but take up a safranin counterstain, appearing red/pink due to their thinner cell wall.
The Gram stain is a fundamental laboratory technique for classifying bacteria.
Name examples of gram-positive cocci.
Gram-positive cocci include:
* Staphylococcus
* Streptococcus
* Enterococcus
These bacteria are significant in clinical settings due to their role in infections.
How can you remember gram-positive rods?
Use the mnemonic:
* Corny – Corynebacteria
* Mike’s – Mycobacteria
* List of – Listeria
* Basic – Bacillus
* Cars – Nocardia
Mnemonics help in memorizing complex information efficiently.
Name examples of gram-negative bacteria.
Examples include:
* Neisseria meningitidis
* Neisseria gonorrhoea
* Haemophilus influenza
* Escherichia coli (E. coli)
* Klebsiella
* Pseudomonas aeruginosa
* Moraxella catarrhalis
Gram-negative bacteria are often associated with more severe infections due to their resistant nature.
What is an example of atypical bacteria?
Atypical bacteria include:
* Legionella pneumophila
* Chlamydia psittaci
* Mycoplasma pneumoniae
* Chlamydophila pneumoniae
* Coxiella burnetii (Q fever)
Atypical bacteria often require specific diagnostic techniques for identification.
What is Methicillin-Resistant Staphylococcus aureus (MRSA) and how is it managed?
MRSA is a strain of Staphylococcus aureus that is resistant to beta-lactam antibiotics. Management includes:
* Screening patients for MRSA (e.g., nasal and groin swabs)
* Eradication via chlorhexidine washes and antibacterial nasal creams
* Treatment options: Doxycycline, Clindamycin, Vancomycin, Teicoplanin, Linezolid
MRSA is a significant public health concern due to its resistance to many antibiotics.
What are Extended-Spectrum Beta-Lactamase (ESBL) bacteria?
ESBL bacteria, typically E. coli or Klebsiella, produce beta-lactamase enzymes that break down beta-lactam antibiotics. They cause infections such as urinary tract infections, pneumonia, and sepsis. Treatment options include:
* Nitrofurantoin
* Fosfomycin
* Carbapenems (e.g., Meropenem, Imipenem)
The presence of ESBL-producing bacteria complicates treatment options and requires careful antibiotic management.
