Haemophilus influenzae has been isolated from the CSF of two year old boy suffering from meningitis. The strain is beta–lactamase producing and resistant to chloramphenicol. The most appropriate antimicrobial in such a situation is –
**Core Concept**
Haemophilus influenzae is a Gram-negative bacterium that can cause meningitis, a life-threatening infection of the protective membranes covering the brain and spinal cord. The production of beta-lactamase enzymes by the bacteria renders them resistant to beta-lactam antibiotics, such as penicillins and cephalosporins. Additionally, chloramphenicol resistance is a concern, making it essential to select an antimicrobial agent that is effective against beta-lactamase-producing H. influenzae.
**Why the Correct Answer is Right**
The correct choice is a third-generation cephalosporin, such as cefotaxime or ceftriaxone. These antibiotics have a broad spectrum of activity against Gram-negative bacteria, including H. influenzae, and are resistant to beta-lactamase degradation. Ceftriaxone, in particular, has a long half-life, allowing for once-daily dosing and making it an ideal choice for treating meningitis. The efficacy of ceftriaxone against chloramphenicol-resistant H. influenzae further supports its selection in this scenario.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ampicillin, a penicillin antibiotic, is typically ineffective against beta-lactamase-producing H. influenzae due to the enzyme's ability to degrade the beta-lactam ring.
**Option B:** This option is incorrect because chloramphenicol, although effective against many Gram-negative bacteria, is not the best choice in this scenario due to the strain's resistance to this antibiotic.
**Option C:** This option is incorrect because trimethoprim-sulfamethoxazole (TMP-SMX) has limited activity against H. influenzae and is not the preferred treatment for meningitis caused by this organism.
**Clinical Pearl / High-Yield Fact**
When treating bacterial meningitis, it is essential to choose an antimicrobial agent that is effective against the causative organism and has a good penetration into the cerebrospinal fluid (CSF). In the case of H. influenzae meningitis, a third-generation cephalosporin, such as ceftriaxone, is the preferred choice due to its broad spectrum of activity, resistance to beta-lactamase degradation, and excellent CSF penetration.
**Correct Answer:** C. Ceftriaxone