# Translucent colonies and gram-negative diplococci: Meningococcal pneumonia masquerading as Moraxella pneumonia

## TL;DR

A case of pneumonia caused by Neisseria meningitidis was mistaken for Moraxella pneumonia due to similar initial test results.

## Contribution

This case highlights the importance of colony appearance in differentiating meningococcal from Moraxella pneumonia.

## Key findings

- Gram-negative diplococci in sputum can be from either Neisseria meningitidis or Moraxella catarrhalis.
- N. meningitidis colonies are mucoid and translucent, while M. catarrhalis colonies are firm and white.
- Accurate diagnosis requires culture-based differentiation of these bacteria.

## Abstract

•The patient presented with pneumonia and gram-negative diplococci on sputum smear.•Neisseria meningitidis and Moraxella catarrhalis are both gram-negative diplococci.•Both bacteria can cause pneumonia but can be differentiated by culture.•Colonies of N. meningitidis are mucoid and translucent.•Colonies of M catarrhalis are firm and white.

The patient presented with pneumonia and gram-negative diplococci on sputum smear.

Neisseria meningitidis and Moraxella catarrhalis are both gram-negative diplococci.

Both bacteria can cause pneumonia but can be differentiated by culture.

Colonies of N. meningitidis are mucoid and translucent.

Colonies of M catarrhalis are firm and white.