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Short Communication
Short Communication Meticillin-resistant commensal staphylococci in the oral cavity of healthy cats: a reservoir of meticillin resistance I. M. Muniz, B. Penna, W. Lilenbaum Staphylococcus species are recognised as constituents of the microbiota of several animal species, and have been isolated from various samples of healthy and diseased cats, including saliva (Lilenbaum and others 1999). Meticillin-resistant Staphylococcus aureus (MRSA) infections are shared between pets and their human handlers, particularly community-acquired MRSA (Oehler and others 2009), and represent an important emerging syndrome in veterinary and human medicine. An increased incidence of human infection with MRSA has resulted in an increased awareness and concern regarding other meticillin-resistant staphylococci (MRS) species that affect veterinary patients. Meticillin resistance is mediated by the mecA gene, which encodes for altered penicillin binding protein 2a (PBP2a), which confers intrinsic resistance to all β-lactam antibiotics. Although some studies have evaluated the presence of staphylococci in the oral cavity of cats, only a few have addressed the presence of MRS. Cats lick themselves and others, and the presence of MRS isolates in cat saliva could serve as a possible source of opportunistic infections. Also, it has been established that animals colonised by MRS can serve as a reservoir for human infections (Cuny and others 2010). Many studies have examined the possibility of MRSA transmission between owners and their pets, including dogs, cats and horses (Wan and others 2011). This study therefore aimed to assess the presence and antimicrobial susceptibility of MRS in the oral cavity of cats. Samples were collected from 200 clinically healthy adult cats (aged one year or older), from Rio de Janeiro, Brazil. In order to avoid bias, only households with five or fewer animals were studied. The clinical status of the cats was determined by a veterinarian who determined each animal’s body temperature, body score, and the presence or absence of skin lesions, and undertook a mucosal examination and auscultation of the cardiorespiratory system. Cats presenting with any signs of dental or periodontal diseases were excluded from the study. In order to avoid previously selected resistant strains, the absence of antimicrobial treatment for at least 30 days before the collection of the samples was required. Saliva samples were collected, using a sterile cotton swab with Stuart medium, from the sublingual region of each cat. All the swabs were spread directly onto mannitol salt agar (Merck, Darmstadt, Germany) and incubated at 37°C for 24 hours. From
Veterinary Record (2013) I. M. Muniz, PhD B. Penna, PhD W. Lilenbaum, PhD Veterinary Bacteriology Laboratory, Universdade Federal Fluminense, R. Prof. Hernani Mello,101/309. Zipcode 24210-130, Niteroi, RJ, Brazil
doi: 10.1136/vr.101971 E-mail for correspondence: [email protected] Provenance: not commissioned; externally peer reviewed Accepted October 1, 2013
each plate, three to five colonies with morphologies compatible with Staphylococcus species were transferred to tryptic soy agar and 5 per cent sheep blood agar. Isolates in pure culture were identified on the basis of colony morphology, Gram staining and by phenotypic (biochemical) methods (Penna and others 2010). Resistance to meticillin was first screened by the disk diffusion test using oxacillin (1 µg) and cefoxitin (30 µg) disks and confirmed by PCR targeting the mecA gene (Zhang and others 2005). All the MRS were tested for their antimicrobial susceptibility (disk diffusion) to other drugs, such as gentamicin (10 µg), tobramycin (10 mg), enrofloxacin (5 µg), ciprofloxacin (5 µg) norfloxacin (10 µg), tetracycline (30 µg), doxycycline (30 µg), clindamycin (2 µg), erythromycin (15 µg), nitrofurantoin (300 µg), trimethoprim+sulfamethoxazole (1.25/23.75 µg), chloramphenicol (30 µg) and rifampicin (5 µg), and the results interpreted according to official recommendations (CLSI 2012). Of the 200 cats examined, 141 (70.5 per cent) yielded 212 staphylococci isolates, because in some cases more than one strain could be recovered. Thirty isolates (14.5 per cent) were phenotypically resistant to meticillin, and 26 (12.3 per cent) of them were confirmed by PCR as harbouring the mecA gene. Of these isolates, coagulase-negative species were by far the most frequent (P
Short Communication
Short Communication Meticillin-resistant commensal staphylococci in the oral cavity of healthy cats: a reservoir of meticillin resistance I. M. Muniz, B. Penna, W. Lilenbaum Staphylococcus species are recognised as constituents of the microbiota of several animal species, and have been isolated from various samples of healthy and diseased cats, including saliva (Lilenbaum and others 1999). Meticillin-resistant Staphylococcus aureus (MRSA) infections are shared between pets and their human handlers, particularly community-acquired MRSA (Oehler and others 2009), and represent an important emerging syndrome in veterinary and human medicine. An increased incidence of human infection with MRSA has resulted in an increased awareness and concern regarding other meticillin-resistant staphylococci (MRS) species that affect veterinary patients. Meticillin resistance is mediated by the mecA gene, which encodes for altered penicillin binding protein 2a (PBP2a), which confers intrinsic resistance to all β-lactam antibiotics. Although some studies have evaluated the presence of staphylococci in the oral cavity of cats, only a few have addressed the presence of MRS. Cats lick themselves and others, and the presence of MRS isolates in cat saliva could serve as a possible source of opportunistic infections. Also, it has been established that animals colonised by MRS can serve as a reservoir for human infections (Cuny and others 2010). Many studies have examined the possibility of MRSA transmission between owners and their pets, including dogs, cats and horses (Wan and others 2011). This study therefore aimed to assess the presence and antimicrobial susceptibility of MRS in the oral cavity of cats. Samples were collected from 200 clinically healthy adult cats (aged one year or older), from Rio de Janeiro, Brazil. In order to avoid bias, only households with five or fewer animals were studied. The clinical status of the cats was determined by a veterinarian who determined each animal’s body temperature, body score, and the presence or absence of skin lesions, and undertook a mucosal examination and auscultation of the cardiorespiratory system. Cats presenting with any signs of dental or periodontal diseases were excluded from the study. In order to avoid previously selected resistant strains, the absence of antimicrobial treatment for at least 30 days before the collection of the samples was required. Saliva samples were collected, using a sterile cotton swab with Stuart medium, from the sublingual region of each cat. All the swabs were spread directly onto mannitol salt agar (Merck, Darmstadt, Germany) and incubated at 37°C for 24 hours. From
Veterinary Record (2013) I. M. Muniz, PhD B. Penna, PhD W. Lilenbaum, PhD Veterinary Bacteriology Laboratory, Universdade Federal Fluminense, R. Prof. Hernani Mello,101/309. Zipcode 24210-130, Niteroi, RJ, Brazil
doi: 10.1136/vr.101971 E-mail for correspondence: [email protected] Provenance: not commissioned; externally peer reviewed Accepted October 1, 2013
each plate, three to five colonies with morphologies compatible with Staphylococcus species were transferred to tryptic soy agar and 5 per cent sheep blood agar. Isolates in pure culture were identified on the basis of colony morphology, Gram staining and by phenotypic (biochemical) methods (Penna and others 2010). Resistance to meticillin was first screened by the disk diffusion test using oxacillin (1 µg) and cefoxitin (30 µg) disks and confirmed by PCR targeting the mecA gene (Zhang and others 2005). All the MRS were tested for their antimicrobial susceptibility (disk diffusion) to other drugs, such as gentamicin (10 µg), tobramycin (10 mg), enrofloxacin (5 µg), ciprofloxacin (5 µg) norfloxacin (10 µg), tetracycline (30 µg), doxycycline (30 µg), clindamycin (2 µg), erythromycin (15 µg), nitrofurantoin (300 µg), trimethoprim+sulfamethoxazole (1.25/23.75 µg), chloramphenicol (30 µg) and rifampicin (5 µg), and the results interpreted according to official recommendations (CLSI 2012). Of the 200 cats examined, 141 (70.5 per cent) yielded 212 staphylococci isolates, because in some cases more than one strain could be recovered. Thirty isolates (14.5 per cent) were phenotypically resistant to meticillin, and 26 (12.3 per cent) of them were confirmed by PCR as harbouring the mecA gene. Of these isolates, coagulase-negative species were by far the most frequent (P
