Regarding the microbiology and laboratory diagnosis of Neisseria gonorrhoeae and Chlamydia trachomatis, all of the following are correct EXCEPT:

Explanation

## Microbiology of Gonorrhea and Chlamydia ### Organism Characteristics **Key Point:** Neisseria gonorrhoeae and Chlamydia trachomatis are distinct organisms with different growth requirements and biochemical properties. | Feature | N. gonorrhoeae | C. trachomatis | |---------|---|---| | Gram stain | Gram-negative diplococcus | Gram-negative, obligate intracellular | | Culture medium | Thayer-Martin (selective), NYC medium | Cannot be cultured on standard media; requires cell culture or special systems | | Growth requirement | Fastidious; requires enriched media | Obligate intracellular; requires living cells | | Fermentation pattern | Ferments **glucose only** (not maltose) | Does not ferment glucose or maltose | | Oxidase test | Positive | Negative | ### Why Option 3 Is Incorrect **High-Yield:** The fermentation pattern stated in option 3 is **backwards**. N. gonorrhoeae ferments **glucose only**, NOT both glucose and maltose. Maltose fermentation is a key differentiator: N. meningitidis ferments both glucose and maltose, but gonorrhoeae ferments glucose alone. This is a classic biochemical distinction used to differentiate Neisseria species. ### Diagnosis **Key Point:** NAAT (nucleic acid amplification tests) are now the gold standard for both organisms because they: - Are more sensitive than culture (>95% sensitivity) - Detect both viable and non-viable organisms - Can be performed on urine, urethral, cervical, rectal, and pharyngeal specimens - Are superior to culture, which is insensitive and organism-dependent **Clinical Pearl:** Culture is rarely used now except for antimicrobial susceptibility testing and medicolegal cases. NAAT has replaced culture as the diagnostic standard of care. ### Why Options 1, 2, and 4 Are Correct - **Option 1:** N. gonorrhoeae is indeed a Gram-negative diplococcus requiring Thayer-Martin or NYC medium — correct. - **Option 2:** C. trachomatis is an obligate intracellular pathogen and cannot grow on standard bacterial media — correct. - **Option 4 (incorrect statement in the option):** This is the trap. N. gonorrhoeae ferments glucose ONLY, not both glucose and maltose. The option states it ferments both, which is false.