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13 Cards in this Set
- Front
- Back
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Describe the Cellular Morphology of Listeria monocytogenes |
gram positive rods averaging 0.5-2.0 micrometres tend to be coccobacilli in direct smears and when grown on solid media, often pairs and short chains longer bacillary forms seen in broth cultures palisades may be seen in broth cultures motile with peritrichous flagella |
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Describe the Growth Requirements for Listeria monocytogenes |
facultative anaerobe, increased CO2 may enhance growth optimum temperature 35C, may grow at temperatures as low as 4C |
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Describe the cultural characteristics of Listeria monocytogenes |
small zone of beta hemolysis, ranges from 0.5 - 2.0mm gray to white translucent |
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describe genus identification for Listeria |
suspected when gray, beta hemolytic colonies on BAP are found to be coccoid Gram positive rods Catalase positive motility positive (tumbling motility) |
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Describe specific tests for Listeria monocytogenes |
BEA positive Hippurate positive CAMP positive (area of hemolysis is more rectangular than that of Group B Streptococcus) |
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Describe the Listeria genus in nature |
ubiquitous in nature L. monocytogenes causes disease in animals |
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describe common infections caused by Listeria monocytogenes |
neonatal infections infant meningitis adult infections not common, include meningitis, pneumonia, septicemia, endocarditis. Listeria outbreaks often traced back to food |
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describe the antimicrobial susceptibility of L. monocytogenes |
generally susceptible to penicillin, ampicillin, erythromycin and aminoglycosides. |
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Describe the characteristics of the genus Lactobacillus |
Long gram positive rods non-spore forming mainly produce lactic acid from carbohydrate fermentation non-motile |
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describe the cellular morphology of Lactobacillus |
Gram positive rods coccoid to long bacilli, usually see long bacilli in direct films occasionally see palisades |
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describe the atmospheric requirements for Lactobacillus |
BAP aerobic - no growth BAP in CO2 - scant growth BAP anaerobic - good growth |
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describe the clinical significance of Lactobacillus |
rarely pathogenic, some endocarditis and meningitis reported predominant organisms in the healthy vaginal mucosa; absence of Lactobacilli may indicate infection |
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describe and explain the presence and absence of Lactobacilli in vaginas as humans age. |
Baby - Lactobacillus present. maternal estrogen causes glycogen deposition in the vaginal epithelium. Lactobacillus colonize and create an acidic pH Child - No Lactobacillus present. Without maternal estrogen there is no glycogen deposited in the vaginal epithelium. Lactobacillus disappear and pH neutralizes Puberty - Lactobacillus present. Endogenous estrogen causes glycogen to be deposited again, and Lactobacillus return to lower the pH. |
