Int J Clin Exp Pathol 2014;7(4):1733-1734 www.ijcep.com /ISSN:1936-2625/IJCEP1312062 Brief Communication Staphylococcus pseudintermedius for CAMP-test Vincenzo Savini 1 , Antonello Paparella 2 , Annalisa Serio 2 , Roberta Marrollo 1 , Edoardo Carretto 3 , Paolo Fazii 1 1 Clinical Microbiology and Virology, Spirito Santo Hospital, Pescara (PE), Italy; 2 Faculty of Bioscience and Technolo- gy for Food, Agriculture and Environment, University of Teramo (TE), Italy; 3 Clinical Microbiology Laboratory, IRCCS Arcispedale S. Maria Nuova, Reggio Emilia (RE), Italy Received December 21, 2013; Accepted February 28, 2014; Epub March 15, 2014; Published April 1, 2014 Abstract: CAMP test reliably detects Listeria monocytogenes (Lm) and Streptococcus agalactiae (group B strepto- coccus, GBS); it is traditionally performed streaking the tested isolate perpendicularly to Staphylococcus aureus (Sa), provided that reference Sa strains (that produce β-hemolysin) are used. In a zone of β-hemolysin activity, in fact, GBS and Lm form typical arrow-shaped hemolytic areas. While Sa production of the toxin is strain-dependent, however, that of Staphylococcus pseudintermedius (Sp), a pet-owner colonizer and an emerging human pathogen, is constitutive, then observed in all clinical isolates. Therefore, Sp may indeed represent a valid alternative to per- form the assay. Keywords: Staphylococcus pseudintermedius, β-hemolysin, CAMP-test, Listeria monocytogenes, GBS CAMP test is one of the most affordable, easy- to-perform methods that may be used in clini- cal laboratories to identify Listeria monocyto- genes ( Lm) and Streptococcus agalactiae (group B streptococcus, GBS) from clinical sam- ples [1, 2]. The term “CAMP” comes from the initials of authors (Christie, Atkins, and Munch- Petersen) who irst studied this assay as well as the particular phenomenon it is based on; we mean that test positivity is typically indicated by formation of an arrow-shaped hemolysis (‘arrowhead’) where GBS and Lm grow in a zone of Staphylococcus aureus (Sa) β-hemolysin activity perpendicularly to Sa and without touching [1-3]. While Sa β-hemolysin synthesis is strain- dependent (then only producing strains may be used for CAMP test), Staphylococcus pseudin- termedius (Sp), a coagulase-positive pet-owner colonizer and an emerging human pathogen, constitutively produces the toxin [3], that is therefore found in all isolates. Hence, any clini- cal Sp may indeed represent a valid alternative to reference Sa strains. Accordingly, Figure 1 reports a positive test carried out using the Sp strain DSM 25713 [3], along with a nonhemo- lytic GBS (identiied with Lioilchem ® Chromatic StrepB and Strepto B latex kit, along with the GenXpert technology (Cepheid, US).) and Lm (identiied with the Lioilchem ® O.A. Listeria Agar (Figure 2), as well as molecularly). The test was performed on the Lioilchem ® Tryptic Soy agar medium (TSS), that is based on a sheep blood composition, and read after 24 h incuba- tion, at 36±1°C, under microaerophilic condi- tions. CAMP test is a diagnostic tool that reliably and quickly provides presumptive identiication of GBS and Lm. Arrowheads promptly develop when bacterial inocula are in an early stage of growth and the sheep blood plate is prewarmed to 37°C [1, 2]. Although, traditionally, only Sa is used (provided that reference strains producing β-hemolysin are previously obtained), we high- light that, indeed, any Sp clinical isolate repre- sents a reliable alternative; production of β-hemolysin (that is strain-dependent in Sa) is in fact intrinsical in Sp, and almost pathog- nomonic. Acknowledgements We thank Lioilchem ® , Roseto degli Abruzzi (Italy), for providing TSS, Strepto B latex kit, and O.A. Listeria Agar. Disclosure of conlict of interest None.