Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Thu, 27 Dec 2018 16:55:20 Case Report Bacteraemia due to meticillin-resistant Staphylococcus aureus carrying the mecC gene in a patient with urothelial carcinoma Marı ´a Pilar Romero-Go ´ mez, 1 Marta Mora-Rillo, 2 Fernando La ´ zaro-Perona, 1 Marı ´a Rosa Go ´ mez-Gil 1 and Jesu ´ s Mingorance 1 Correspondence Marı ´a Pilar Romero-Go ´ mez mpromero.hulp@salud.madrid.org Received 25 June 2013 Accepted 21 September 2013 1 Servicio de Microbiologı ´a Clı ´nica, Hospital Universitario La Paz, IdiPAZ, Paseo de La Castellana, 261, Madrid 28046, Spain 2 Unidad de Enfermedades Infecciosas y Microbiologı ´a Clı ´nica. Hospital Universitario La Paz, IdiPAZ, Paseo de La Castellana, 261, Madrid 28046, Spain We present a case of bacteraemia due to meticillin-resistant Staphylococcus aureus (MRSA) carrying the mecC gene. The susceptibility to meticillin of Staphylococcus aureus was investigated directly from one blood culture bottle using GenomEra MRSA/SA (Abacus Diagnostica Oy) test. This test identified S. aureus but the presence of the mecA gene result was negative, and the isolate was reported as meticillin-sensitive Staphylococcus aureus (MSSA). Susceptibility studies were done using VITEK 2 AST-P588 susceptibility cards (bioMe ´ rieux). The strain was identified as MRSA by the VITEK 2 system, although oxacillin MIC was low (0.5 mg ml ”1 ). In view of these results, the isolate was tested for the presence of the mecC gene by a specific PCR and was verified as MRSA carrying mecC. The emergence of this new mecA homologue could have important consequences for the detection of MRSA when routine PCR methods are used as an identification method or provisional detection of MRSA, as in the case reported in this article, because S. aureus carrying the mecC gene will be wrongly diagnosed as meticillin susceptible. Negative results must be interpreted with caution and should be followed by conventional culture, and antimicrobial susceptibility testing or detection of mecC gene by a specific PCR. The first meticillin-resistant Staphylococcus aureus (MRSA) was described in the early 1960s, soon after the introduc- tion of meticillin in human therapy, and since then it has become a major public health issue due to the worldwide spread of several clones. The genetic mechanism of meticillin resistance was identified as a gene called mecA, that codes for a specific meticillin-resistant trans- peptidase (penicillin-binding protein 2a). The gene is inserted in a mobile genetic element known as the Staphylococcal chromosomal cassette (SCCmec) which is integrated into the S. aureus chromosome (Ito et al., 1999). The penicillin-binding protein 2a coded by mecA has a low affinity for b-lactam antimicrobial drugs; thus bacteria expressing this protein are resistant to almost all b-lactams (Ruimy et al., 2008). A new divergent mecA homologue (mecC or mecA LGA251 ) (Garcı´a-A ´ lvarez et al., 2011; Shore et al., 2011) has been recently described in a novel SCCmec type XI (Shore et al., 2011). The recent discovery of the SCCmec XI, which harbours this new mecC element with only 70 % sequence similarity to mecA genes, raises concerns about the detection of MRSA carrying this element (Garcı´a-A ´ lvarez et al., 2011). This new mecC was detected in milk samples from dairy cows in the UK and in human clinical samples in the UK, Germany, Denmark and Ireland (Cuny et al., 2011; Garcı ´a- A ´ lvarez et al., 2011; Petersen et al., 2013; Shore et al., 2011). Prevalence studies of S. aureus isolates carrying mecC in Denmark indicate that the frequency could be as high as 4 %. Previous studies in animal and clinical human strains have shown that MRSA carrying mecC gene was identified as MRSA by VITEK 2 automated system (growth in the presence of 6 mg ml 21 cefoxitin according to the VITEK 2 Advanced Expert System), although oxacillin MICs were low (0.5 mg ml 21 ) or moderately high (# 4 mg ml 21 ). The isolates were misidentified as mecA-negative, and therefore meticillin sensitive, by routine PCR (Cartwright et al., 2013; Walther et al., 2012). We present a case of bacteraemia due to MRSA carrying the mecC gene. The patient was a 76-year-old man recently diagnosed as having urothelial carcinoma. He was without Abbreviations: MRSA, meticillin-resistant Staphylococcus aureus; MSSA, meticillin-sensitive Staphylococcus aureus; SSCmec; Staphylococcal chromosomal cassette. Journal of Medical Microbiology (2013), 62, 1914–1916 DOI 10.1099/jmm.0.064683-0 1914 064683 G 2013 SGM Printed in Great Britain