Journal of Small Animal Practice • Vol 53 • June 2012 • © 2012 British Small Animal Veterinary Association 365 LETTERS Nitrofurantoin reveals good in vitro antimicrobial activity against methicillin- resistant staphylococci isolated from dogs with topic infections MADAM Staphylococci, mainly Staphylococcus pseudintermedius, are important opportunistic pathogens in dogs, frequently associated with dermatological infections. Since the resistance pattern to antimicrobials of members of this genus are constantly changing, knowledge of these patterns requires frequent updating (Penna and others 2010). Methicillin-resistant staphylococci (MRS) are resistant to beta-lactam antibiotics. In recent years, MRS have been increasingly reported as an emerging problem not only in hospitals but also in veterinary medicine, particularly in small animal practice (Cohn and Middleton 2010). Nitrofurantoin is currently not used in small animal practice, mainly due to its toxicity, lower pharmacokinetic performance (Maaland and Guardabassi 2011) and high resistance rates (Penna and others 2010). Nevertheless, we have been observing encouraging results regarding the in vitro antimicrobial activity of nitrofurantoin against staphylococci isolated from dogs with topical infections. A total of 194 isolates of Staphylococcus obtained from dogs with otitis externa (123) or pyoderma (71) were identified by phenotypic methods (Bannerman 2003) and tested for their antimicrobial susceptibility by disk diffusion for nitrofurantoin (CLSI 2011). Resistance to methicillin was determined by poly- merase chain reaction targeting the mecA gene (Zhang and others 2005). Staphylococcus intermedius (48) was the most frequent species, followed by Staphylococcus schleiferi schleiferi (41), S. pseudinter- medius (39), Staphylococcus simulans (22), S. schleiferi coagulans (20), Staphylococcus epidermidis (18) and Staphylococcus aureus (5). Resistance to methicillin was observed in 15 isolates, distributed among S. intermedius (8), S. pseudintermedius (4), S. schleiferi schleiferi (1), S. simulans (1) and S. epidermidis (1). Only eight of the 194 isolates (4·1%) were resistant to nitrofurantoin. More importantly, that drug presented excellent results when MRS isolates are considered, since no resistance to nitrofurantoin was verified among those 15 isolates. MRS has acquired a mobile genetic element known as staphylococcal cassette chromosome mec (SCCmec). This cas- sette not only carries the mecA gene but may also carry addi- tional antimicrobial resistance markers. This in part explains why MRS are often resistant to many antimicrobials of different classes, besides the beta-lactams (Cohn and Middleton 2010). Therefore, the treatment of infections caused by MRS may very often be difficult to handle, and nitrofurantoin may act as an alternative. Although there is some information regarding the oral administration of nitrofurantoin in dogs (Maaland and Guard- abassi 2011), one of the limitations of its use in canine topical infections relates to the unknown variables in administration, including a lack of information regarding in vivo efficacy, tox- icity and side-effects in dogs after topical administration. A possible drawback of this study is related to the breakpoints Radiographic features of presumed congenital subluxation of the radial head in three Newfoundland littermates MADAM Congenital luxation or subluxation of the radial head (type I) is an uncommon condition of the canine elbow (Milton & Montgomery 1987; Dassler & Vasseur 2003; Piermattei & Johnson 2004). Diagnosis of congenital elbow subluxation is based on early onset of clinical signs and radiographs; it must be differentiated from developmental elbow luxation (McDonell 2004). To the authors knowledge, type I congenital elbow luxation has not been described in the Newfoundland. Two male and one female 20-week-old Newfoundlands pre- sented with a history of abnormal gait and severe bilateral elbow and antebrachial deformity. Orthopaedic examination revealed bilateral elbow pain, effusion and laterally displaced radial head. Radiographically, all three dogs had malalignment, incongru- ity and abnormal configuration of the elbow joints. Severe, cau- dolateral subluxation of the humero-radial joints and widening of the humeroulnar joints was present (Fig 1). There was marked lateral angulation of the radius originating at the mid-diaphysis and valgus of the carpi. Diagnosis: Type I congenital luxation of the radial head Outcome: All three dogs were euthanased by 21 weeks of age due to poor quality of life. that were used for determining nitrofurantoin resistance. The only available breakpoints have been established for Staphylo- coccus of human origin, and mainly for urinary tract infections (CLSI 2011). If nitrofurantoin becomes an interesting alterna- tive for MRS topical infections in dogs, further studies may be required. B. Penna, R. F. Rabello and W. Lilenbaum Veterinary Bacteriology Laboratory, Fluminense Federal University, Niteroi, RJ 24210-130, Brazil References BANNERMAN, T. L. (2003) Staphylococcus, Micrococcus and other catalase- positive cocci that grow aerobically. In: Manual of clinical microbiology. 8th edn. Eds P . R. Murray, E. J. Baron, M. A. Pfaller, J. H. Jorgensen and R. H. Yolken. ASM Press, Washington, DC, USA. pp 384-404 Clinical and Laboratory Standards Institute (CLSI). (2011) Performance Standards for Antimicrobial Susceptibility Testing; Twenty-first Informational Supplement. Approved Standard M100-S21. Clinical and Laboratory Standards Institute, Wayne, PA, USA COHN, L. A. & MIDDLETON, J. R. (2010) A veterinary perspective on methicillin- resistant staphylococci. Journal of Veterinay Emergency and Critical Care 20, 31-45 MAALAND, M. & GUARDABASSI, L. (2011) In vitro antimicrobial activity of nitrofuran- toin against Escherichia coli and Staphylococcus pseudintermedius isolated from dogs and cats. Veterinary Microbiology 151, 396-399 PENNA, B., VARGES, R., MEDEIROS, L., MARTINS, G., MARTINS, R. & LILENBAUM, W. (2010) Species distribution and antimicrobial susceptibility of staphylococci isola- ted from canine otitis externa. Veterinary Dermatology 21, 292-296 ZHANG, K., MCCLURE, J. A., ELSAYED, S., LOUIE, T. & CONLY, J. M. (2005) Novel multi- plex PCR assay for characterization and concomitant subtyping of staphy- lococcal cassette chromosome mec types I to V in methicillin-resistant Staphylococcus aureus. Journal of Clinical Microbiology 43, 5026-5033 http://www.bsava.com/