Arcanobacterium Selective Agar

Cat. no. A134 Arcanobacterium Selective Agar, 15x100mm Plate, 17ml 10 plates/bag
Cat. no. J134 Arcano Select / Group A Beta Strep Biplate, 15x100mm Plate, 10ml/10ml 10 plates/bag

INTENDED USE

Hardy Diagnostics Arcanobacterium Selective Agar is recommended for use as a selective medium for the isolation of Arcanobacterium haemolyticum, especially from respiratory specimens.

SUMMARY

Arcanobacterium haemolyticum is a beta-hemolytic, gram-positive, pleomorphic, facultative anaerobic rod that has been isolated from a variety of clinical conditions such as skin and wound infections, pharyngotonsillitis, peritonsillar abscesses, and systemic infections in all age groups.(1-5) The bacterium is most commonly associated with pharyngitis in adolescents and young adults.(1-4)

A. haemolyticum typically grows slowly and exhibits a narrow zone of beta-hemolysis on sheep blood agar. This pathogen can easily be masked by commensal throat flora or misinterpreted as an oral contaminant. The organism may be missed on routine throat cultures because most specimens are plated on special selective culture media used to optimize the recovery of group A Streptococcus (GAS). Additionally, most cultures are examined in 24 hours, at which A. haemolyticum colonies are very small and demonstrate minimal hemolysis. A. haemolyticum can be grown in CO2 or anaerobic conditions and requires 48 hours to reach full maturity; enhanced hemolysis occurs when the organism is grown under anaerobic conditions.

The symptoms of A. haemolyticum pharyngitis may be confused with those of GAS, diphtheria, and drug allergies.(1,2) Studies show that approximately half of patients  with positive throat cultures for A. haemolyticum have a diffuse, red rash resembling what is seen with scarlet fever or a penicillin allergy.(1-3) The characteristic rash and symptoms of a GAS infection may result in a misdiagnosis in adolescents infected with A. haemolyticum.

Misdiagnosis can often lead to treatment with penicillin, the drug of choice for GAS. Although A. haemolyticum is usually sensitive to penicillin in vitro, there are many reported treatment failures due to penicillin tolerance.(1,2,4) The study by Banck et al. found that A. haemolyticum was recovered from patients 2-4 weeks after treatment with penicillin.(1) The same study noted that one third of patients positive for A. haemolyticum had a history of recurrent tonsillitis.(1) For this reason, erythromycin is the drug of choice for A. haemolyticum pharyngotonsillitis.(1,2,4)

In an article by Cummings et al., the estimated frequency of pharyngitis caused by A. haemolyticum was reported in about 5 to 13% of the total pharyngitis cases caused by GAS, but it was noted that this may be an underestimate.(5) In throat swab cultures, A. haemolyticum is found to be responsible for 0.5-2.5% of pharyngitis cases.(1-4) However, the prevalence of A. haemolyticum is much higher in adolescents and young adults. In a study by Brenwald using a selective culture medium, A haemolyticum was isolated from 6.3% of specimens from patients 11-20 years old. GAS was isolated from 14.3% of specimens from the same age group.(4) These results demonstrate the value of a selective medium for A. haemolyticum, especially for use with throat cultures on young adults and adolescents.

Arcanobacterium Selective Agar contains digests of soybean meal and casein. The combination of soy and casein peptones supply organic nitrogen in the form of amino acids and polypeptides, making the medium highly nutritious. Sheep blood is included to enable detection of hemolysis. Selective agents have been added to the medium to inhibit Streptococcus pyogenes and other commensal organisms, without affecting the growth of Arcanobacterium haemolyticum.

Hardy Diagnostics Arcanobacterium Selective Agar allows for the selective isolation of A. haemolyticum from specimens containing high numbers of commensal organisms, and will increase the detection rate of this organism.

FORMULA

Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 15.0g
Peptic Digest of Soybean Meal 5.0g
Sodium Chloride 20.0g
Selective Agents 40.0mg
Sheep Blood 50.0mL
Agar 15.0g

Final pH 7.2 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-8ºC away from direct light. Media should not be used if there are any signs of
deterioration (shrinking, cracking, or discoloration), hemolysis, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

Specimen Collection: Infectious material should be submitted directly to the laboratory without delay and protected from excessive heat and cold. If there is to be a delay in processing, specimens should be inoculated into an appropriate transport media and refrigerated until inoculation.

Method of Use: Prior to inoculation, the medium should be brought to room temperature. Inoculate media with specimen and streak for isolation. For testing an isolated organism, touch the top of a colony with a sterile loop and streak for isolation. Incubate anaerobically at 35ºC. for 42-48 hours. Plates may also be incubated in 5-10% CO2, however anaerobic incubation is recommended and yields enhanced growth and better development of hemolytic reactions. Examine plate for growth and typical colony morphology and hemolysis.

INTERPRETATION OF RESULTS

Typical colonies of Arcanobacterium haemolyticum appear small, white, and rough to convex surrounded by a zone of beta-hemolysis after 42 to 48 hours of incubation. Mature colonies will often pit the agar beneath the colony. Refer to listed references for more information.

LIMITATIONS

Anaerobic incubation is  recommended.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, swabs, applicator sticks, other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Arcanobacterium haemolyticum
ATCC ® BAA-1784**
A 48hr 35°C Anaerobic Growth with beta-hemolysis
Streptococcus pyogenes
ATCC ® 19615
B 48hr 35°C Anaerobic Partial to complete inhibition
Streptococcus mitis
ATCC ® 6249
B 48hr 35°C Anaerobic Partial to complete inhibition
Escherichia coli
ATCC ® 25922**
B 48hr 35°C Anaerobic Partial to complete inhibition

** Recommended QC strains for User Quality Control according to the CLSI document M22 when applicable.

USER QUALITY CONTROL

Physical Appearance

Arcanobacterium Selective Agar should appear opaque, and cherry red in color.

A. haemolyticum growing on Arcanobacterium Selective Agar

Arcanobacterium haemolyticum (ATCC® BAA-1784) colonies growing on Arcanobacterium Selective Agar (Cat. no. A134). Colonies shown with reflected light. Incubated anaerobically for 48 hours at 35ºC.

A. haemolyticum beta-hemolysis on Arcanobacterium Selective Agar

Arcanobacterium haemolyticum (ATCC® BAA-1784) colonies growing on Arcanobacterium Selective Agar (Cat. no. A134). Beta-hemolysis is demonstrated with transmitted light. Incubated anaerobically for 48 hours at 35ºC.

Uninoculated plate of Arcanobacterium Selective Agar

Uninoculated plate of Arcanobacterium Selective Agar (Cat. no. A134).

REFERENCES

1. Banck, G., et al. 1986. Tonsillitis and rash associated with Corynebacterium haemolyticum. J. Infect. Dis. 154:1037-1040.

2. Mackenzie, A., et al. 1995. Incidence and pathogenicity of Arcanobacterium haemolyticum during a 2-year study in Ottawa. Clin. Infect. Dis.; 21:177-81.

3. Fell, H., et al.1977. Corynebactenum haemolyticum infections in Cambridgeshire. J. Hyg. Camb.; 79:269-274.

4. Brenwald, N.P., et al. 1990. Selective medium for isolating Arcanobacterium haemolyticum. J. Clin. Pathol.; 43(7):610.

5. Cummings, L.A., et al. 1993. Effects of Media, Atmosphere, and Incubation Time on the Colonial Morphology of Arcanobacterium haemolyticum. J. Clin. Microbiol.; 31:3223-3226.

6. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

7. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

8. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

9. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

ATCC is a registered trademark of the American Type Culture Collection.

080216gr