a 4-year - old male neutered domestic shorthair cat was presented to the oregon state university cardiology service for suspected pericardial effusion . cardiac tamponade was documented and pericardiocentesis yielded purulent fluid with cytologic results supportive of bacterial pericarditis . the microbial population consisted of pasteurella multocida , actinomyces canis , fusobacterium and bacteroides species . conservative management was elected consisting of intravenous antibiotic therapy with ampicillin sodium / sulbactam sodium and metronidazole for 48 h followed by 4 weeks of oral antibiotics . re - examination 3 months after the initial incident indicated no recurrence of effusion and the cat remained free of clinical signs 2 years after presentation . bacterial pericarditis is a rare cause of pericardial effusion in cats . growth of p multocida , a canis , conservative management with broad - spectrum antibiotics may be considered when further diagnostic imaging or exploratory surgery to search for a primary nidus of infection is not feasible or elected . pericardial disease in cats is relatively uncommon , with a reported prevalence ranging from 1.0 - 2.3% in post - mortem studies . the most common causes of pericardial effusion in cats results from congestive heart failure secondary to cardiomyopathic disease and neoplasia . other less frequently cited etiologies include trauma , disseminated intravascular coagulation , uremic pericarditis , peritoneopericardial diaphragmatic hernia , feline infectious peritonitis , coagulopathy , hypoalbuminemia and infective pericarditis . infective pericarditis includes viral , bacterial , fungal or parasitic colonization of the pericardium , and is rarely reported in cats . this case report describes a cat with bacterial pericarditis with previously undocumented microorganisms and a favorable clinical response to conservative medical management . a 4-year - old male neutered domestic shorthair cat presented to the primary veterinarian after being found recumbent and dyspneic at home . mild pyrexia ( 39.5c ) , muffled heart sounds and weak femoral pulses were identified on physical examination . thoracic radiographs revealed a globoid cardiac silhouette , and the cat was referred immediately to the oregon state university ( osu ) cardiology service for suspected pericardial effusion ( figures 1 and 2 ) . review of the incoming thoracic radiographs suggested a large - volume pericardial effusion with a small amount of concurrent pleural effusion . the cat s past pertinent history was unremarkable ; it was an indoor cat with no historical altercations with the other household cat . there is a generalized increase in cardiac silhouette size with dorsal deviation of the thoracic trachea . the increased opacity of the cranial mediastinum is most consistent with fat infiltration ventrodorsal radiograph . the cat is positioned obliquely upon presentation to osu , the cat was depressed but responsive . it was hypothermic ( 36.7c ) and tachypneic ( 60 breaths per minute ) with a high - to - normal heart rate ( 220 beats per minute ) . its mucous membranes were blanched and tacky ; no capillary refill time could be obtained . the cat s heart sounds were muffled and femoral pulse quality was poor . echocardiography was performed emergently , confirming a large volume of anechoic pericardial effusion with cardiac tamponade ( figure 3 ; see also supplementary material ) . a small volume of pleural effusion was also present , likely due to impaired filling of the right heart with cardiac tamponade . pericardiocentesis was prioritized and buprenorphine ( 0.15 mg / kg iv , buprenex ; rickitt benckiser healthcare ) was administered for sedation . following aseptic skin preparation of the right fourth  sixth intercostal space at the costochondral junction , pericardiocentesis performed with an 18 g intravenous catheter resulted in the removal of 80 ml of malodorous opaque red - tinged fluid flecked with white particles . cytologic evaluation of the pericardial fluid indicated a markedly increased nucleated cell count ( 138,100/l ; international system of units si : 138.1  10/l ) consisting of 20% macrophages and 80% degenerative neutrophils , many with intracellular bacteria of various types . these findings were consistent with a septic suppurative exudate ; consequently , the pericardial fluid was submitted for aerobic and anaerobic bacterial culture and antimicrobial susceptibility . testing for non - bacterial microorganisms ( fungal , viral etiologies ) was not performed . diastolic collapse of the right atrium and ventricle was noted , consistent with cardiac tamponade . the lumens of the right ventricle ( rv ) and left ventricle ( lv ) are labeled . the pericardial effusion is diffusely present around the ventricles ( * ) the signs of cardiogenic shock resolved following pericardiocentesis . the echocardiographic examination was completed with no evidence of structural heart disease or neoplastic masses . cardiac tamponade was abolished and a small amount of residual pericardial and pleural effusions remained after pericardiocentesis . other diagnostics performed included complete blood count ( cbc ) , chemistry panel , urinalysis , feline immunodeficiency virus ( fiv ) and feline leukemia virus ( felv ) antigen testing ( idexx laboratories ) , blood pressure measurement and ecg . the cat s blood pressure was 130 mmhg ( doppler method ) and its ecg indicated sinus rhythm with a left anterior fascicular block - like pattern . the relevant laboratory test abnormalities are listed in table 1 ; abnormalities were consistent with sepsis ( eg , transitional leukogram , mild hyperbilirubinemia ) . the urine sample was obtained several hours after fluid therapy , indicating a urine specific gravity of 1.018 without bilirubin , glucose , protein , cells or bacteria present . wbc = white blood cell diagnostic and therapeutic options were discussed with the cat s owners , including the recommendation to pursue computed tomography ( ct ) to search for a local thoracic or distant source of infection . owing to financial limitations , the owners elected to pursue conservative management with hospitalization and empiric parenteral antibiotic therapy . ampicillin sodium / sulbactam sodium ( 30/kg mg iv q8h ; aurobindo pharma ) , metronidazole ( 15 mg / kg iv q12h ; claris lifesciences ) and intravenous fluid therapy ( lactated ringer s solution ) were initiated . the cat s 5% dehydration deficit was replaced over 6 h , followed by a maintenance fluid rate of 20 ml / h . over the next 48 h , a cbc and chemistry panel were repeated 2 days after presentation ; the relevant results are presented in table 1 . after 2 days of hospitalization , the cat was transitioned to oral medications and discharged with instructions to receive amoxicillin / clavulanic acid ( 20 mg / kg po q8h ; pfizer ) and metronidazole ( 10 mg / kg po q12h ; watson pharma private ) for 4 weeks . at the time of discharge , the pleural effusion was likely either residual pleural fluid from impaired diastolic filling of the right heart during cardiac tamponade , or the result of pericardial effusion leakage following percardiocentesis . the final aerobic culture results yielded heavy growth of both pasteurella multocida and actinomyces canis . aerobic antimicrobial susceptibility testing suggested p multocida was sensitive to ampicillin though resistant to clindamycin and tobramycin . the cat presented to osu for re - evaluation 1 week after discharge and was reported to have normal appetite , energy and demeanor at home . a recheck cbc indicated normalization of the white blood cell count ( 8970/l ; si 8.97  10/l ) with an unremarkable leukogram . furthermore , the chemistry panel indicated complete resolution of the previous electrolyte disturbances , as well as normalization of creatine kinase and alanine aminotransferase . continuation of the antibiotic regimen was recommended and recheck examination was advised following completion of the course . the cat was re - evaluated by echocardiography 3 months after its initial presentation , and no recurrent effusion was noted . feline bacterial pericarditis has been sparsely reported in the veterinary literature . in a large - scale retrospective study of pericardial effusion in 146 cats , several mechanisms can result in septic pericarditis , including pericarditis secondary to localized spread of infection ( eg , pneumonia , suppurative mediastinal lymphadenitis ) , hematogenous infection , extension of endocarditis / myocarditis , or direct inoculation resulting from penetrating wounds , migrating foreign material or surgery . the associated clinical signs are often related to hemodynamic compromise from pericardial effusion or related to systemic infection ( eg , pyrexia , weight loss ) . of the published case reports , some have shown a documented predisposing infection , whereas the inciting etiology was not conclusively identified in others . a cat in one report developed bacterial pericarditis in close temporal proximity to a dental prophylaxis with a common oropharyngeal microorganism , peptostreptococcus . clavulanic acid for approximately 3 weeks and a full recovery was reported 6 weeks after completion of the antibiotic course . another recent case report described bacterial pericarditis in an intact female cat with pyometra and hematogenous spread of escherichia coli . that cat responded well to a 4 week course of enrofloxacin and metronidazole following peri - cardiectomy , and remained clinically stable 1 year later . conversely , another published report of feline bacterial pericarditis identified infection with a mixed population of enterobacteriaceae species and coagulase - negative staphylococcus species without an obvious predisposing cause . an anaerobic culture was not performed , and the cat responded favorably to an 8 week course of broad - spectrum antimicrobial therapy . owing to the multiple organisms involved , direct inoculation via a penetrating wound or foreign material the case reported here did not have a readily apparent systemic or focal infection , or any immune - modulating systemic diseases ; however , an exhaustive search was not pursued . bite wounds are generally associated with the oral flora of the biting animal rather than the skin flora of the victim . the most common aerobic isolate in cat bites is p multocida , and anaerobic isolates commonly include fusobacterium and bacteroides species . though the cat reported here was exclusively housed indoors , another cat was present in the household and may have incited the infection through an unwitnessed altercation . less likely , this infection may have resulted from atraumatic hematagenous spread of bacteria and alternate sources of infection ( eg , odontogenic , esophageal , pleuropulmonary ) were not systematically excluded . while the incidence and causes of septic pericarditis vary across species , the diagnostic approach and therapeutic goals remain the same . identification of the specific pathogen(s ) , related antibiotic susceptibility and source of the infection are paramount . cytology and culture of the pericardial fluid is crucial in the diagnosis of septic cases , unlike most other causes of pericardial effusion . in addition , blood cultures are advised in humans as they are positive in 4070% of cases . aerobic and anaerobic susceptibility testing is also recommended , although most laboratories do not routinely perform susceptibility testing on anaerobic isolates . as anaerobic pericarditis is associated with odontogenic infection , esophageal disease , pleuropulmonary infection , abdominal infection and pelvic infection in humans , a thorough search for adjacent and distant infections owing to the low incidence and small number of published case reports , the ideal therapy for septic pericarditis in cats is unclear . results of susceptibility testing facilitate antibiotic selection , although , if unavailable , broad - spectrum coverage is recommended based on the wide range of bacterial isolates reported . the standard of care in affected humans involves aggressive medical management , including an indwelling pericardial catheter for drainage and targeted antibiotic therapy . in dogs affected by bacterial pericarditis , eradication of the source of the infection is imperative and surgical exploration is indicated in cases that have failed medical management or have suspected abscessation identified on diagnostic imaging . consequently , advanced imaging , exploratory surgery and pericardectomy could be advised in affected cats , although , interestingly , complete recovery has been reported with antibiotics alone in previous cases and the cat reported here . the development of constriction is an important potential sequela to septic and non - septic pericarditis , and should be assessed on patient follow - up . constriction is theorized to occur secondarily to the influx of inflammatory cells into the pericardial space , ultimately leading to proliferation of fibrotic connective tissue and neovascularization . these changes can result in a loss of pericardial elasticity and thus limit diastolic filling . in a prospective human study , 9/500 ( 1.8% ) patients developed constriction over a median follow - up time of 72 months . while overall constriction is a rare complication of human viral or idiopathic pericarditis ( < 0.5% ) , the risk of constriction was highest in the bacterial pericarditis group ( 33% ) . the prevalence of constriction in cats is unknown , although echocardiographic evidence of constrictive physiology was identified in one cat with septic pericarditis . constrictive pericarditis is difficult to definitively diagnose , but echocardiographic findings of a thickened pericardium and respiratory variation of > 25% in mitral inflow velocities can be highly suggestive . in the case presented here , no subjective or clinical evidence of constrictive pericarditis was identified during the limited echocardiograms during recheck examinations ; however , concern exists for its development nonetheless . the cat reported here fully recovered following conservative therapy consisting of pericardiocentesis and broad - spectrum antibiotic treatment . larger retrospective or prospective studies could help further characterize treatment strategies and prognosis in affected cats .
case summarya 4-year - old male neutered domestic shorthair cat was presented to the oregon state university cardiology service for suspected pericardial effusion . 
 cardiac tamponade was documented and pericardiocentesis yielded purulent fluid with cytologic results supportive of bacterial pericarditis . 
 the microbial population consisted of pasteurella multocida , actinomyces canis , fusobacterium and bacteroides species . 
 conservative management was elected consisting of intravenous antibiotic therapy with ampicillin sodium / sulbactam sodium and metronidazole for 48 h followed by 4 weeks of oral antibiotics . 
 re - examination 3 months after the initial incident indicated no recurrence of effusion and the cat remained free of clinical signs 2 years after presentation.relevance and novel informationbacterial pericarditis is a rare cause of pericardial effusion in cats . 
 growth of p multocida , a canis , fusobacterium and bacteroides species has not previously been documented in feline septic pericarditis . 
 conservative management with broad - spectrum antibiotics may be considered when further diagnostic imaging or exploratory surgery to search for a primary nidus of infection is not feasible or elected .