II$.$ Gram$-$Negative Bacteria$$

$1.$ Identification:$$

o Gram stain morphology: diplococci, rods.$$

o Examples:$$

$$ Pseudomonas aeruginosa: Oxidase positive, grows on MacConkey agar.$$

$$ Neisseria meningitidis: Gram$-$negative diplococci, meningitis symptoms.$$

$2.$ Tests:$$

o Oxidase test: Differentiates Enterobacterales $($oxidase$-$negative$)$ from non$-$fermenters$$

$($oxidase$-$positive$).$

o MacConkey agar: Differentiates lactose fermenters from non$-$fermenters.$$

$3.$ Clinical Relevance:$$

o Symptoms and conditions: Severe headache, fever, spinal fluid results indicating$$

bacterial meningitis.$$

III. Laboratory Techniques$$

$1.$ Streaking Methods:$$

o Isolation streak: Obtain pure colonies.$$

o Quantitative streak: Estimate colony count.$$

$2.$ Microscopy:$$

o Gram stain observations:$$

$$ Gram$-$positive cocci in chains $($e$.$g$.,$ Streptococcus spp$.).$

$$ Gram$-$negative diplococci in cerebrospinal fluid $($e$.$g$.,$ Neisseria meningitidis$).$

$3.$ Media Observations:$$

o MacConkey agar: Lactose fermentation $($pink colonies$).$

o Blood agar: Hemolysis patterns.$$

IV$.$ Clinical Specimens$$

$1.$ Sputum Criteria:$$

o Acceptable: Adequate epithelial and PMN cells.$$

$2.$ Interpretation of Cultures:$$

o Case$-$based analysis of various specimen types$$

V$.$ General Bacteriology$$

$1.$ Cell Structure:$$

o Prokaryotes$$

$2.$ Bacterial Shapes:$$

o Cocci, bacilli, spirochetes.$$

$3.$ Metabolism:$$

o Aerobes vs$.$ anaerobes:$$

$$ Obligate aerobes: Require oxygen.$$

$$ Obligate anaerobes: Cannot grow in oxygen.$$

VI$.$ Case Study analysis$$

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