Clinical Microbiology Flashcards
What organisms are Prokaryotes and which are Eukaryotes?
Prokaryotes: Bacteria
Eukaryotes: Fungi, Parasites, Animals, Plants
What are the key characteristics of Eukaryotes?
True Nucleus
Membrane bound organelles
Mitotic apparatus
linear DNA
What is unique to the eukaryotic cell membrane?
Sterols
Peptidoglycans
Repeating disaccharides with four amino acid side chains. Unique to Prokaryotic cell wall.
What are the various shapes of bacteria?
Cocci- Round
Bacilli- Rod
Spirochetes- Spiralled
What are the arrangements of bacteria?
Diplo- in pairs
Strepto- chain like
Staphylo- grapelike clusters
What is the smallest bacteria?
Mycoplasma
Gram + cell walls contain:
- Thick peptidoglycan layer
- Teichoic acid
Gram - cell walls consists of 4 layers:
- Inner cytoplasmic membrane
- Periplasmic space
- thin peptidoglycan layer
- Lipopolysaccharide
What is in the Periplasmic space?
beta-lactamase that degrades beta-lactam drugs (penicillin)
What is the structure of LPS?
- O-antigen (1-50 oligosaccharide different for each bacteria)
- polysaccharide core
- Lipid A (endotoxin)
Mycobacteria
acid fast bacteria. Resist decolorization from Acid alcohol. Stained with Carbolfuchsin. High concentration of Mycolic acids.
Mycolic acid
Resists phagocytosis. Found in TB, MAI, and Leprosy. Acid fast organisms.
What are the specialized structures outside the cell wall?
- Capsule
- Flagella
- Pili (Fimbriae)
- Glycocalyx (slime layer)
- Endospore
How do you stain bacteria capsules?
- India Ink Stain
2. Quelling reaction: causes swelling of capsule
Capsule
Enables bacteria virulence. Prevents phagocytosis. Sugars from capsule are used as antigens in vaccines.
Flagella
Whip-like appendages for motility.
Vibrio cholera- 1 flagellum
E. coli- multiple flagella
Shigella- no flagella
Most common cause of UTI’s
E.coli and P. mirabilis. Use flagella to propel bacteria up urethra.
Pili (fimbriae)
hairlike filaments used for adherence. N. gonorrhea use pili to cause Gonorrhea.
Adhesins
adherence factors associated with pili. Bacteria using adhesins include:
E.coli- diarrhea
Bordetella pertussis- Whooping Cough
Glycocalyx
Slime layer allows for bacteria adherence.
-Strep mutans
Endospore
dormant until proper nutrients. Examples:
Bacillis anthracis
Clostridium botulina
Exotoxins
Protein secreted by Gram +.
Neurotoxins and Enterotoxins.
Two diseases caused by Enterotoxins
- Infectious diarrhea: bacteria continuously in GI tract
2. Food poisoning: bacteria grow on food and then ingested.
Endotoxins
Lipid A portion of LPS. Released when cell is lysed.
considered normal flora on the skin
Staphylococcus epidermidis. Non pathogenic but can cause disease.
What are the normal flora of the respiratory tract and their pathogenic counterpart?
Strep Viridans- Strep pyogenes
Neisseria- Neisseria menigitidis
Staph epidermidis- Staph aureus
Eikenella corrodens
Skin and soft tissue infections associated with human bites and clenched-fist injuries
B. fragilis
perforation of intestinal wall causing peritonitis
lactobacillus
maintains low pH of vagina
Group B Streptococci
carried by mother, transferred to child during birth causing sepsis and meningitis.
Mycobacterium smegmatis
acid fast organism around female urethras and uncircumcised males
