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Micro Anaerobic
| Question | Answer |
|---|---|
| Obligate (strict) aerobic | Require molecular oxygen for growth, cannot grow without it |
| Capnophilic | Grow best @ CO2 conc 5-10%, O2 conc reduced to 15% |
| Microaerophilic | Require oxygen for growth at 5% concentration or less |
| Facultative anaerobe | Prefer aerobic, but will grown anaerobically |
| Aerotolerant Anaerobe | Can survive with Molecular oxygen but not able to perform metabolic processes unless placed in anaerobic environment |
| Obligate (strict) anaerobe | Oxygen is toxic , will destroy them almost instantly. Cannot metabolize molecular Oxygen |
| Why is Oxygen Toxic for anaerobes? | *Due to the free radicals produced Metabolic oxidation-reduction in body produce O2- (superoxide) and H2O2 (Hydrogen peroxide). *anaerobes lack protective enzymes (superoxide dismutase and catalase) :. superoxide = toxic bio oxidant |
| Where are Anaerobes found Endogenously? | Normal internal micro flora of human/animals |
| Exogenous Anaerobes? | Aerobic outside bodies of human/animals are usually gram positive, spore forming bacilli |
| Sites where anaerobes are part of normal micro flora? | *Skin : sebaceous glands and hair follicles *Respiratory Tract: Saliva, gingival and tooth scrapings (90% anaerobes) *Gastrointestinal Tract: colon Anaerobe to aerobe ratio = 1000/1 *Genitourinary tract: urethra, vagina anaerobe to aerobe ration 5/1 |
| What is a predisposition to anaerobic infection | Trauma to protective barriers -skin, mucous membrane etc.. *opportunistic pathogen |
| Example of specimen suitable for anerobic culture? | CSF, Biopsy-tissue, needle and syringe abscess, aspirated pus or urine direct from source, sinus tract of draining wounds, deep tissue/bone surgery spec., pleural fluid, blood, bone marrow, synovial fluid etc.... |
| Example of specimen not suitable for anerobic culture? | superficial wounds, vaginal, cervical, urethral swabs, stool, rectal swab, voided/catheterized urine, gastric content |
| Factors Negatively affecting quality of anaerobic culture | *pH *Moisture *Temp *Volume of spec *presence of other Org |
| 1st eval step of an anaerobic culture? | Gram stain- morphology, leukocytes? epi? Contaminating Bacteria? |
| What are Special nutritional requirements of anaerobes? | Vitamin K, Hemin, Yeast extract |
| What are 3 types of media | Nonselective: support most non-fastidous microbes Selective: inhibit some Enrichment: contain additional factors to help with growth |
| What are the two primary inoculation media for Anaerobes, and Why? | Anaerobic Blood Agar (CDC) -enables growth of obligate & facultative anaerobes, great for anaerobic GPC Phenylethyl Alcohol Agar (PEA) -enables growth of obligates (Gram pos and Gram Neg) and Gram positive facultative |
| In inoculation in Tube Media (Thio) how does aerobes/anaerobes grow? | Obligate aerobes @ top Obligate anaerobes @ bottom Facultative all throughout- where ever their oxygen requirements are satisfied |
| What type of Bacterial growth does KVLB plate support? | Kanamycin-vancomycin-laked blood agar - support Bacteroides -kanamycin -resistant, facultative, GNR |
| What type of Bacterial growth does BBE plate support? | Bacteroides bile esculin agar -support growth of bile-tolerant species |
| Is there a medium that will not grow aerobes? | NO! anaerobic media will also grow aerobes |
| During inoculation ,how long does it take anaerobic chambers to become a complete anaerobic environment? | 3-5 hours |
| How long can inoculated plates sit at room temp? | Max 1 hour |
| At what temp do you incubate inoculated specimens? | 35-37*C |
| When can you examine primary plates? Anaerobic chamber, Jar/bag/pouches with a holding system vs no holding system. | In Anaerobic Chamber= any time Jar/bags/ouches with holding system =24 hour Jar/bags/ouches without holding system = 48 hours |
| How long are Anaerobic cultures held to observe growth? | usually 5-7 days |
| How long are Actinomyces cultures held to observe growth? | 10 days -slow growing anaerobe |
| What are some indicator that an anaerobe is present? | - foul odor -colonies present on anaerobically incubated plates and not CO2 or Chocolate plates - Double zone of hemolysis on BAP incubated anaerobically |
| What are some presumptive way to ID anaerobes? | - Fluorescence - Catalase test - Spot Indole Test - Urease Test - Motility test - Disk *Special=potency antimicrobial disks, SPS * Nitrate Disk * Bile Disk * Lecithinase, lipase and Proteolytic reactions |
| What are some definitive way to ID anaerobes? | -Biochemical-based multitest systems -Enzyme-Based systems -Conventional Tubed biochemical Identification systems *liquid gas chromatography -Cellular Fatty Acid analysis by high-resolution GLC -16 S Ribosomal RNA Gene sequencing |
| What is the best way to ID an anaerobe isolate | By using a combination technique, each anaerobe react differently and can be ID using culture results, gas liquid chromatography, rapid enzyme systems, and biochemical characterization. |
| Name 3 anaerobic gram positive cocci | * Peptostrptococcus spp: -Normal on skim mouth I, GU, resemble streptococcus *Finegoldia: most pathogenic, most often isolated in pure culture - resemble staph *Peptoniphilus. GPC in pairs, short chains, tetrads/clusters, yellow colonies |
| Name spore forming Gram- positive anaerobic bacilli | Clostridium -C.perfrigens -C.difficile -C.tentani -C.botlulinum -C.septicum |
| Name non-spore forming Gram- positive anaerobic bacilli | Actinomyces, Bifidobacterium, Eubacterium, Lactobacillus, Propionibacterium |
| All spore-forming anaerobic bacilli are classified in the genus Clostridium are collectively referred to as what? | clostridia |
| How do you differentiate clostridia? | lecithinas and lipase reactions |
| How is clostridia differentiated? | based on location of the spore -terminal: end of bacteria -subterminal: found at location other than the end |
| How does Clostridum usually gain access to the body? | Via ingestion/open wound from contaminated soil/foos/water |
| What does Clostridium infections cause? | Tetanus, gas gangrene, botulism, food poisoning |
| What are two obligate anaerobic Clostridia? | C.haemolyticum, C.novyi |
| What are two aerotolerant Clostridia? | C.histolyticum, C.carnis |
| What is an adverse reaction of treating Clostridium difficile infections? | Antibiotic-associated diarrhea and pseudomembrane colitis -C.diff allow bacteria to multiple and produce 2 toxins (enterotoxin + cytotoxin) -freq transmitted among hospital patients and nursing homes |
| What disease does Clostridium tetani cause? | Tetanus: spastic type of paralysis with continous muscle spasms |
| What disease does C.perfrigens cause? | Gas gangrene/ myonecrosis -amputation if not treated |
| What disease does C.botulinum cause? | Botulism: potent neurotoxin, attach to neuromuscular junction and prevents the release of acetocholine (paralysis) and eventually leads to death |
| What disease does C.perfringens cause? | Food poisoning |
| State Morphology of C.Perfrigens and Methodology of Identification | -no spore, large with blunt ends "box car" like -Large, irregular on blood agar -double zone of beta hemolysis -positive for lecithinase |
| State Morphology of C.difficile and Methodology of Identification | -subterminal spores, thin GPR, may form chains -large flat colonies -barnyard odor -fluoresce (greenish/yellow) under UV light |
| State Morphology of C.tetani | -terminal spores, drum like appearance |
| State Morphology of C.botulinum | -subterminal spore, GPR |
| What causes Actinomycosis? | Actinomyces, bifidobacterium, propionibacterium |
| What causes Bacterial Vaginosis? | Mobiluncus, Lactobacillus |
| Describe Actinomycosis | Chronic, granulomatous infection developed in sinus tract and fistula that erupt to the surface, drainage of pus contain sulfur granules (small colonies of bacteria) |
| What is the Principal agent of Actinomycosis? | Actinomyces israelii: non-spore forming, gram positive bacilli. frequently exhibits branching and produces sulfur granules |
| What is the morphology of Actinomyces? | -straight to slightly curved rods, varying in length, rods may have clubbed ends, dip like arrangements, short chains or small clusters. * Young colonies are spider like or wooly, older colonies resemble raspberry or a molar tooth. Color varies by species |
| Describe the Morphology of Bifidobacterium species | -variable in shape, ranging from coccobacilli to ling branching rods. -end of cell pointed/bent/clubbed shaped. Spatulated or bifurcated (forked). -can be single or in chains, star-like cluster aggregates "V" arrangement, or "palisade" clusters. |
| Describe the Morphology of Propionibacterium species and the method of Identification | Pleomorphic rods that frequently appear as diphtheroid. P. acmes is catalase-positive, spot indole-positive, anaerobic gram-positive diphtheroid. Common member of skin flora but not always a contaminant |
| What is the morphology of Eubacterium | pleomorphic rods to coccobacilli in pairs and short chains |
| Where is Eubacterium found to be normal flora? | it is normal in GI tract and oral flora |
| Rarely pathogenic, What diseases can Eubacterium cause? | Endocarditis, Dental infections, Wound infections |
| Name another Microbe that can also cause BV | Mobiluncus, Bacteroides (GNR), Prevotella (GNR) , Gardnerella vaginalis |
| Is it appropriate to perform a culture on BV discharge? Why? | No, most anaerobes associated with BV are part of normal flora |
| Describe the morphology of Lactobacillus species? | -Gram positive pleomorphic bacilli, coccoid or spiral-shaped, over 100 species |
| Where in the body is Lactobacillus normal flora? | The mouth, GI tract, female genital tract |
| How does Lactobacillus protect the female genital tract? | -It protects the host from urogenital infection -Lactobacillus produces lactic acid which lowers vaginal pH suppressing the overgrowth of Mobiluncus, Prevotella and G. Vaginalis |
| What is the morphology of Mobiluncus species and what is its susceptibility. | -Curved, motile bacilli. Stain pink or gram-variable but are not gram-negative organism. -Cell wall lack lipopolysaccharide -susceptible to vancomycin and resistant to colistin |
| Do anaerobic gram negative bacilli form spore? Where are they found as part of normal flora? | -they do not from spores. They are normal flora in the mouth and urogenital tract of humans and animals. |
| Where is Bacteroides found as normal flora? What are some facts about its sensitivity? What infection is it frequently involve? | -in oral cavity, gastrointestinal and genitourinary tracts -frequently involved in abscesses and sepsis -resistance to antibiotic -has species that are bile tolerant and bile sensitive |
| Name a bile tolerant Bacteroides | B. fragillis |
| What are some characteristic of B. fragilis? | -On BBE agar, the yellow medium-> brown around the colonies due to esculin hydrolysis -dark stippling in medium around heavy growth -resistant to Kanamycin, Colistin and Vancomycin |
| What is the Morphology of Prevotella and what are some ways of presumptive Identification? | Produce protoporphyrin- dark pigment that cause colonies to become brown with age. Gram neg coccobacilli/bacilli only brick red fluorescence- key ID Resistant to vancomycin and kanamycin grow on KVLB but not BBE |
| What is the Morphology of Porphyromonas and what are some ways of presumptive Identification? | produce dark brown to black pigment Brick red fluorescence - but will fluoresce other colors as well susceptible to vancomycin |
| What is the Morphology of Fusobacterium? | long, thin, tapered rods(pointed) Only F. nucleatum has cells that are consistently fusiform Will grow on KVLB |
| Of anaerobic gram negative cocci, which one is considered a pathogen? | Only Veillonella |
| Where is Veillonella considered normal flora? | In upper respiratory, Gi and GU tract |
| What is the morphology of Veillonella on gram stain? | Tiny GNDC in pairs, cluster or short chains -can resemble Neisseria |
| What can be identify presumptively after it is found to be nitrate-positive, anaerobic and gram negative? | Veillonella |
| What are problems with susceptibility testing? | -reproducibility -failure of anaerobe to grow on/in media -lack of comparability between methods -cost and complexity factors -accuracy of methos and correlation with in vivo/clinal situation |
| What are two methods which are acceptable to use for susceptibility testing? | -Agar dilution =gold standard -Micro broth dilution :disks have diff antibiotic conc. |
| E-test | ETEST is a well-established method for Minimum Inhibitory Concentration (MIC) determinations |
| B-lactamase testing | Beta-lactamases are a diverse class of enzymes produced by bacteria that break open the beta-lactam ring, inactivating the beta-lactam antibiotic (penicillin and cephalosporins) |
| How is Anaerobe-associated Disease treated?? | -Surgical therapy: removal or infected/eliminating obstruction/improve circulation etc. -Hyperbaric Oxygen- force oxygen into necrotic tissue -Antimicrobial therapy -select antibiotic based on org involved/known/factor -Antitoxins-treat neurotoxins |
| What are the primary antibiotics for anaerobes | Carbapenems= structure resistant to B-lactamase Metronidazole= low toxicity, no B-lactam ring B-lactam or a combination of it= Combination includes B-lactamase inhibitor |
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lemon8
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