Why do we prefer chocolate agar for culturing Haemophilus influenzae over blood agar?

Chocolate agar is prepared by heating blood agar, which in turn ruptures the red blood cell (RBC) and releases nutrients that aid in the growth of fastidious bacteria, most notably Haemophilus and Neisseria species. The name is derived from the fact that the lysis of RBC gives the medium a chocolate-brown color.

Which bacteria can grow on chocolate agar?

Chocolate agar is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae and Neisseria meningitidis.

Can Haemophilus influenzae grow on nutrient agar?

Haemophilus influenzae requires both factors X and V; accordingly, it grows on chocolate agar but not on blood agar (Fig. 30-2), although it may appear on a blood agar plate as tiny satellite colonies around the colonies of other bacteria that have lysed red blood cells.

Can Haemophilus influenzae be cultured?

CSF samples should be cultured on blood agar plates (BAP) and supplemented chocolate agar plates (CAP) that are prepared with 5–10% sheep or horse blood. The optimal medium for growth for H. influenzae is CAP with X and V factors, whereas pneumococcus grows best on BAP.

Does gonorrhea grow on chocolate agar?

Red blood cell lysis gives the medium a chocolate-brown coloration when prepared from which the agar gets its name. The most common bacterial pathogens that require this enriched medium for growth include Neisseria gonorrhoeae and Haemophilus species.

Does Neisseria gonorrhoeae grow on chocolate agar?

Why does Haemophilus not grow on blood agar?

Members of the genus Haemophilus will not grow on blood agar plates, as all species require at least one of these blood factors for growth: hemin (X-factor) and/or nicotinamide adenine dinucleotide (V-factor).

How do you grow Haemophilus influenzae?

H. influenzae strains normally grow well in rich media such as brain heart infusion (BHI), suitably supplemented with hemin and NAD (sBHI), and on sBHI or chocolate agar plates. Many isolates classified as H. influenzae differ in their other nutritional requirements, for a purine and for specific amino acids (1,2).

What agar does N gonorrhoeae grow on?

N. gonorrhoeae is usually isolated on Thayer–Martin agar (or VPN) agar in an atmosphere enriched with 3-7% carbon dioxide.

Does strep grow on chocolate agar?

Chapter 8: Identification and Characterization of Streptococcus pneumoniae. S. pneumoniae is a fastidious bacterium, growing best at 35-37°C with ~5% CO2 (or in a candle-jar). It is usually cultured on media that contain blood, but can also grow on a chocolate agar plate (CAP).

What does chocolate agar do?

Chocolate Agar is an enriched general- purpose medium that supports the growth of most fastidious and non-fastidious organisms. Because it is a non-selective medium, resident flora from clinical specimens may overgrow potential fastidious pathogens, such as Neisseria species.

What are Haemophilus influenzae colonies on chocolate agar?

Haemophilus influenzae colonies on chocolate agar after overnight incubation in a carbon dioxide atmosphere as shown above image. It must contain haemin or other iron-containing porphyrin and nicotinamide adenine dinucleotide (NAD) or its phosphate (NADP).

Can H influenzae grow on sheep blood agar?

The most common species that require this enriched medium for growth include Neisseria meningitidis and Haemophilus spp. H. influenzae is not able to grow on sheep blood agar. It can be prepared by the following methods. Take already prepared blood agar plates (5% sheep blood agar) and put those plates into a hot air oven for 2 hours at 55°C.

What is the best medium for growth of H influenzae?

The standard medium used for growth of H. influenzae is a chocolate agar plate (CAP), which can be prepared with heat-lysed horse blood, a good source of both hemin and NAD, although sheep blood can also be used.

What is the composition of chocolate agar used for?

It is used for the isolation of fastidious bacteria, such as Haemophilus influenzae , when incubated at 35-37°C in a 5% CO 2 incubator. The composition of chocolate agar is the same as the blood agar and the only difference is while preparing Chocolate agar, the red blood cells are lysed changing the medium color chocolate brown.