Comp Clin Pathol DOI 10.1007/s00580-014-2011-x
BRIEF COMMUNICATION
Isolation of Rhodococcus equi from a mule with cutaneous wound M. Heidari Sureshjani & N. Atyabi & A. Tazikeh & S. Khanamani Falahatipour & M. Hashemian
Received: 19 May 2014 / Accepted: 30 September 2014 # Springer-Verlag London 2014
Abstract Rhodococcus equi is an encapsulated gram-positive, pleomorphic rod which exists in the soil and frequently is isolated from the feces of normal herbivores. It is the primary cause of pneumonia in foals. This organism has been isolated from various animals, but isolation from the wound is rarely reported. In May 2013, a 7-month-old Janet (female mule) was referred with some ulcers on the face below the zygomatic process in the right side in dimensions of 2×2 cm. Swab samples were taken from the ulcer for bacteriological cultures. The isolated bacteria grew on cysteine tellurite agar. The tests of catalase and nitrate reduction were positive, but urea hydrolysis was negative. The result of the ChristieAtkins-Munch-Petersen (CAMP) test was positive and “spade showel-shaped” hemolytic pattern was seen in blood agar. The bacteria were identified as R. equi. This organism was susceptible to gentamycin, azithromycin, and erythromycin. The presence of R. equi as a pathogen without pulmonary disease is important because it can cause wound contamination and leads to persistence of the organism in the environment. An exposure to soil contaminated with livestock manure seems to be the most probable mode of infection for this case. Keywords Rhodococcus equi . Mule . Wound . CAMP test
Rhodococcus equi is an encapsulated gram-positive, pleomorphic rod which is highly resistant to soil pH, chemical treatment, and drying for long periods. The organism exists in the M. Heidari Sureshjani (*) : N. Atyabi : A. Tazikeh : M. Hashemian Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran e-mail:
[email protected] S. Khanamani Falahatipour Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
soil and frequently isolates from the feces of normal horses and other herbivores (Sahin et al. 2002). Rhodococcus equi is a well-recognized bacterial pathogen in veterinary medicine. First isolated from Swedish foals by Magnusson in 1923, it causes an important chronic granulomatous pneumonia and lung abscesses in foals aged below 4 months and is a common isolate from cervical lymph nodes in swine (Prescott 1991). Although, rare infection occurs in a wide variety of other mammals, often following immunosuppression of various causes. Infection commonly includes granulomatous pneumonia which develops into lung abscesses in these unusual hosts. Other extra pulmonary pathological conditions are: septic arthritis, ulcerative lymphangitis, lymphadenitis (often of the mesenteric, bronchial, or cervical lymph nodes), mesenteric lymph node abscess, gastrointestinal infection, meningitis, mastoiditis, cellulitis, pleuritis, pericarditis, uterine infection, osteomyelitis, endophthalmitis, wound infections and cutaneous wound, and abscesses in various parts of the body such as liver, kidney, and psoas muscles (Chen XY et al. 2009; Prescott 1991; Kedlaya et al. 2001; Sahin et al. 2002). The natural route of R. equi transmission is unknown but it is usually transmitted through inhalation and alimentary tract. R. equi occurs worldwide and is generally considered to be a soil contaminant. Several reports have also described contamination by R. equi (Sahin et al. 2002). This report aims to establish the isolation of R. equi in the cutaneous tissue (wound) in a mule. In May 2013, a 7-month-old Janet (female mule) was referred to the Veterinary Research and Teaching Hospital of the University of Tehran (VRTH) with clinical signs such as anorexia, little labored breathing, heart rate of 90 bpm, sweating and wet skin, mild fever, and some ulcers on the face below the zygomatic process at the right side. According to the owner’s information, the ulcer was pertained to 10 days ago. The dimensions of the wound were 2×2 cm and have
Comp Clin Pathol
partial healing and incomplete granular tissue. After primary observation, some swab samples were taken from the ulcer for bacteriological cultures, aerobically and anaerobically, in blood agar and some specific culture media to detect the probable causative agent. The appearance of colony growth on blood agar was mucoid, moist, non-hemolytic, and yellowish after 48-h incubation in 37 °C. In the microscopic examination, gram-positive pleomorphic rods were observed by gram staining. Additional tests were performed to confirm diagnosis of isolated bacteria. The isolated bacteria grew on cysteine tellurite agar. The tests of catalase and nitrate reduction were positive, but urea hydrolysis was negative. Carbohydrate fermentation such as, glucose, maltose, sucrose, mannitol, and esculin hydrolysis were negative. The result of the Christie-Atkins-Munch-Petersen (CAMP) test was positive and “spade showel-shaped” hemolytic pattern was seen in blood agar against Staphylococcus aureus (Fig. 1). The bacteria were identified as R. equi according to the above observation. Antimicrobial susceptibility was performed as well. Rhodococcus equi has been found in bovine, porcine, and equine fecal flora. It grows best at a summer temperature and on horse farms (Kedlaya et al. 2001). R. equi is the primary cause of pneumonia in foals (Sahin et al. 2002). The presence of R. equi infection has been reported particularly in various organs in newborn foals and immunodeficient horses (Sahin et al. 2002). Ulcerative lymphangitis caused by R. equi has occasionally been reported to develop on foal legs (Prescott 1991). The organism has been isolated from ulcerative lymphangitis in cattle, apparently following skin wounds made by thorns (Prescott 1991). Although, infection is primarily acquired through the respiratory tract, it has been found to be acquired both by the oral route and by traumatic inoculation or super infection of wounds (Kedlaya et al. 2001).
Fig. 1 Synergistic hemolysis on blood agar
Immunologic status associated with age, levels of antibody, and environmental stress increase susceptibility to infection (Sahin et al. 2002). It is well known that R. equi can affect several organs including the eyes and digestive tract and can be associated with lymph nodes, bones, joints, and various organs (Sahin et al. 2002). Wound infections and subcutaneous abscesses have been reported in cats and dogs (Takai et al. 2003). In this case, the naturally occurring R. equi cutaneous ulcer, in which there was no accompanying pneumonia, indicated that the organism was capable of causing infection and disease in skin as well (Sahin et al. 2002). Rhodococcus equi is usually susceptible to erythromycin, ciprofloxacin, vancomycin, aminoglycosides, rifampin, imipenem, and meropenem (Puthucheary et al. 2006). Antimicrobial susceptibility in the present case revealed that R. equi is susceptible to gentamycin, azithromycin, and erythromycin. Its susceptibility for enrofloxacine, norfloxacine, oxytetracycline, tetracycline, tylosin, and penicillin was moderate. Although in this case, bacteria was not resistant to penicillin, but all human isolates have been resistant to penicillin, the same as some soil isolates, which are susceptible (Fierer et al. 1987). Our antimicrobial susceptibility test yielded results parallel to those of Sahin et al. (2002). Combination therapy is recommended to prevent antibiotic resistance (Denes et al. 2010). One of the most common combinations involved a macrolide often with erythromycin (Kedlaya et al. 2001; Vengust et al. 2002; Denes et al. 2010; Puthucheary et al. 2006; Fierer et al. 1987). Since the core of pathogenesis of R. equi is being weak in acid fast, it can persist in macrophages. Thus, the intracellular survival of the organism has recommended that R. equi infections can be treated with lipophilic antibiotics that penetrate the cells (Puthucheary et al. 2006). Rhodococcus equi is ubiquitous in the environment but is not reported as a cause of cutaneous ulcer in mule. In this case, a mule was presented with anorexia, little labored breathing, heart rate of 90 bpm, sweating and wet skin, mild fever, and some ulcers on face below the zygomatic process in the right side. This is a short communication of cutaneous ulcer associated with R. equi in a mule. Dust controlling can be important in preventing R. equi infection as well as preventing trauma in skin. An exposure to soil contaminated with livestock manure seems to be the most probable mode of infection for this case. Since these bacteria lives in the soil, disinfection and keeping the wound clean are apparently effective to prevent and control infection. Regarding the occurrence of the infection in immune-compromised patients, the owners should attempt to feed the colostrum to the neonate and become sure of providing the sufficient level of primary immunity in the animal.
Comp Clin Pathol
References Chen XY, Feng XU, Xia JY, Cheng YS, Yang Y (2009) Bacteremia due to Rhodococcus equi: a case report and review of the literature. J Zhejiang Univ Sci B 10:933–936 Denes E, Peignon-Orsoni D, Terrade FX (2010) Nonhealing wound due to Rhodococcus equi in an apparently immunocompetent patient, revealing CD8_ T-lymphocyte deficiency. J Clin Microbiol 48: 4658–4660 Fierer J, Wolf P, Seed L, Gay T, Noonan K, Haghighi P (1987) Nonpulmonary Rhodococcus equi infections in patients with acquired immune deficiency syndrome (AIDS). J Clin Pathol 40:556–558 Kedlaya I, Mb I, Ss W (2001) Rhodococcus equi infections in immunocompetent hosts: case report and review. Clin Infect Dis 32:39–47
Prescott JF (1991) Rhodococcus equi: an animal and human pathogen. Clin Microbiol Rev 4:20–34 Puthucheary SD, Sangkar V, Hafeez A, Karunakaran R, Ns R, Hassan HH (2006) Rhodococcus equi—an emerging human pathogen in immunocompromized hosts: a report of four cases from Malaysia. Southeast Asian J Trop Med Public Health 37:1 Sahin M, Otlu S, Kankavi O (2002) Isolation of Rhodococcus equi from a horse with corneal ulcer. Kafkas Univ Vet Fak Derg 8:67–69 Takai SH, Martens RJ, Julian A, Ribeiro MG, Rodrigues DE, Farias M, Sasaki Y, Inuzuka K, Kakuda T, Tsubaki S, Prescott JF (2003) Virulence of Rhodococcus equi isolated from cats and dogs. J Clin Microbiol 41:4468–4470 Vengust M, Staempfli H, Prescott JF (2002) Rhodococcus equi pleuropneumonia in an adult horse. Can Vet J 43:706–708
