Microbiology/Bacteriology PDF

Summary

This document is a study guide on microbiology and bacteriology, including bacterial growth requirements, sterilization methods, and antibiotics. It details the importance of temperature, pH, oxygen, and other atmospheric requirements for bacterial growth. It also lists different culture media, sterilization and disinfection methods.

Full Transcript

137 MICROBIOLOGY/ Bacteriology by Mona Bakeer and Mary Lux Bacteria...

137 MICROBIOLOGY/ Bacteriology by Mona Bakeer and Mary Lux Bacterial Growth Requirements ❖ Palladium pellets catalyze the 1. T emperature reaction a. P sychrophiles - cold loving; ❖ Some require hemin, Vitamin K , optimum temper ature = 15°C and yeast extract b. Mesophiles - moderate temper ature; 5. Typical incub ation optimum temperature = 37 C; (most a. 5-10% CO2 (incubator or candle pathogenic organism s) j ar ) c. Thermophiles - heat loving; b. 35-37°C optimum temperature = 50-60°C c. 50-70% humidity 2. pH optimized for most 6. May be selective and/or differential a. Bacteria 6.5-7.5 b. Fungi 5.0-6.0 STERIUZATION/INHIBITION TECHNIQUES 1. H eat - denatures p rotein 3. Oxygen a. Moist - autoclave (steam under a. Aerobes - require 0 2 pressure) b. Facultative anaerobes - can grow ❖ 15 lbs pressure/sq. in., 121 °C, with or without 0 2 15 minutes c. Obligate anaerobes - harmed by 0 2 ❖ QC - Bacillus stearothermopbilus d. F ormation of superoxide radical!,, b. Dry heat toxic; n eutr alized by catalase, ❖ Flame, incinerator peroxidase and ❖ Hot air oven 170°C, 2 hrs superoxide dismutase (p ossessed b y c. Pasteuriza tion , ultra high aerobes and fa cultatives) temperature ❖ 140°G, 3 secon ds 4. Other atmosph eric requirements ❖ NOT sterilization a. Microaerophiles - p refer lower 0 2 than :in air 2. Filtration b. Capnophilcs - prefer higher CO2 a. Pore size 0. 22 µ - 0.45 µ than in air b. Used for sugar solutions, urea c. Aerotolerant- do not require 0 2 but media , vaccines not poisoned by 0 2 3. Refriger ation - slows gr owth CULTURE MEDIA 4. Dessication - no multiplication, but 1. Must meet growth r equirements or ganisms r emain viable (Jyophilization) 2. Agar - polysaccharide der ived from marine algae 5. Osmotic pressure hypertonic solution a. Melts at l00°C a. Causes plasmolysis b. Solidifies at approximately 45°C h. "Cured " meat, fruit preserves 3. Complex media - most common ; ma de 6. Radiation of peptones and extracts a. Forms h ydroxyl radicals b. Damages D A 4. Anaerobic media - contain r educing agents which bind with dissolved 0 2 7. Disinfection (tbi.oglycollate, cysteine) a. Phenol - damages cytoplasmic a. Bro th tubes should h e heated prior membrane, denatures protein to use to drive out 0 2 b. Halogen s (iodine and chlorine) - b. Gas pak en velop es oxidizer s ❖ Contain Na2 CO3 and sodium c. Alcohols - denature protein and horohydride dissolve lipids ❖ Add water - produces H2 and CO2 (aids in growth) 138 STERILIZATION 0ISINFErTION Kills All Microorganisms Inactivation or Inhibition of (Including Spores and Microorllanisms (May Not Viruses) A ect Spores) Examples: [xample: Autoclave (121 'C at 1Spsi Bleach (1:10 Hypochlorite) Autoclave Pressure, for 15 min.) Temperature and Time Incineration Filtration (Physically Removes Microorganisms) Antibiotics and Their Actions ANTIBIOTIC EXAMPLES ACTION NOTES B-lactams Penicillins Inhibits cell wall synthesis Ceftriaxone, Cefotax ime Cephalosporins Carbapenams (lmipenam) Monobactams (Azotreonam) B-lactamase Inhibiting Combin- ations (Augmentin, etc.) Glycopeptides Vancomycin Inhibits cell wall synthesis Drug of choice for Clostridium d ifficile and MRSA Aminoglycosides Gentamicin Inhibits protein synthesis Acts on 30S subunit; not active Tobramycin against anaerobes; used with a Amikacin penicillin for Enterococcus Tetracyclines Tetracycline Inhibits protein synthesis Acts on 30S subunit; affects Doxycycline bone an d teeth in children ; may lead to super infection of yeast Chloramphenicol Chloramphenicol Inhibits protein synthesis Acts on 50S subunit; can cause aplastic anemia MacroIides Erythromycin Inhibits protein synthesis Acts o n 50S subunit; Clindamycin clindamycin for GP and G N anaerobes Quinolines Ciprofloxacin Inhibits nucleic acid Fo r Pseudomonas aeruginosa Norfloxacin synthesis and other aerobes Sulfa Drugs (Sulfonomides) Sulfamethoxazole Analogue of PABA For UTI. enteric infections; used (intermediate in folic acid with trimethoprim (Bactrim, etc.) synthesis) Streptogramins Quinupristin/dalfopristin Inhibits protein sythesis For GP, especially vancomycin resistant Enterococcus faecium Oxazdidinones Linezolid Inhibits protein sythesis For GP, including those resistant to other antibiotics Antibiotics/Susceptibi/i'ty Testing 4. Bactericidal action - kills bacteria without host immune help ANTIMICROBIAL THERAPY 1. Narrow spectrum - only certain 5. Bacteriostatic action - rever sible groups covered inhibition ( ultimate destruction d epends on h ost defen ses) 2. Broad spectrum - Gram pos (GP) and Gram n eg ( GN) coverage 6. Drug combination a. Synergism - combined b etter than 3. Selective toxicity - action against the sum: 1 + 2 = 4 microbe only without injuring cells of b. Antagonism - one d ecreases activity host of other: 1 + 2 = l

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