**Question:** Haemophilus influenzae has been isolated from the CSF of a 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:

A. Ceftriaxone
B. Amoxicillin
C. Cephalosporin
D. Chloramphenicol

**Core Concept:**

Haemophilus influenzae is a gram-negative coccobacillus that can cause meningitis, particularly in young children. Beta-lactamase production and chloramphenicol resistance in H. influenzae make it challenging to treat with traditional antibiotics like amoxicillin or chloramphenicol. Cephalosporins and beta-lactamase inhibitors like clavulanic acid in ceftriaxone are effective against H. influenzae due to their ability to penetrate the bacterial cell wall and inhibit beta-lactamase enzymes.

**Why the Correct Answer is Right:**

Given the beta-lactamase production and chloramphenicol resistance, the most appropriate antibiotic to treat H. influenzae meningitis is **Ceftriaxone**. Ceftriaxone is a long-acting cephalosporin that is effective against gram-negative bacteria, including H. influenzae. Its ability to penetrate the bacterial cell wall and combine with clavulanic acid (an inhibitor of beta-lactamase enzymes) makes it highly effective against beta-lactamase-producing strains, such as the one in this case.

**Why Each Wrong Option is Inappropriate:**

**Option A (Amoxicillin):**
Amoxicillin is a penicillin, a class of antibiotics that are susceptible to beta-lactamase degradation. Given that the H. influenzae strain is beta-lactamase producing, amoxicillin is not an appropriate choice.

**Option B (Chloramphenicol):**
Chloramphenicol is a chloramphenicol, an antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit. However, the bacterial strain is resistant due to chloramphenicol resistance. Hence, this option is not suitable.

**Option C (Cephalosporin):**
Cephalosporins are a class of antibiotics that inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs). However, the strain's beta-lactamase production is an issue, rendering cephalosporins ineffective against this specific strain.

**Option D (Chloramphenicol):**
As mentioned, chloramphenicol resistance is a significant issue in the case of H. influenzae. This makes chloramphenicol unsuitable for treating this strain.

**Clinical Pearl:**
A thorough understanding of antibiotic resistance mechanisms, such as beta-lactamase production and chloramphenicol resistance, is essential when choosing antibiotics for treatment. It ensures that you select an antibiotic that is effective against the