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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