Etiology, multidrug resistance, and acute-phase proteins biomarkers as in equine septic arthritis

ABSTRACT: Etiology, multiple antibiotic resistance index, and acute-phase protein profile in the serum and synovial fluid of 44 horses presenting septic arthritis were investigated. Young animals up to 24 months of age not yet submitted to taming were sampled. Synovial samples from the horses were submitted to culture and bacterial isolates subjected to 18 antimicrobials to investigate the in vitro multidrug resistance pattern. Also, hematological aspects, fibrinogen, and serum levels of some acute-phase proteins (total protein, albumin, globulin, amyloid A, and C-reactive protein) were assessed. To statistical analysis, microbiological isolation were divided into four groups: G1 = animals with negative isolation, G2 = isolation of Gram-negative bacteria, G3 = isolation of Gram-positive bacteria), and G4 = isolation of fungi. Microbial isolation was obtained from 77.2% (32/44) of the synovial samples. Escherichia coli (7/44 = 15.9%), Staphylococcus aureus (5/44 = 11.4%), Streptococcus equi subsp. equi (3/44 = 6.8%), Aspergillus niger (3/44 = 6.8%), Pseudomonas aeruginosa (2/44 = 4.5%), Streptococcus equi subsp. zooepidemicus (1/44 = 2.3%), Trueperella pyogenes (1/44 = 2.3%), and Rhodococcus equi (1/44 = 2.3%) were prevalent bacterial agents. Aspergillus niger is reported by the first time as a primary agent of septic arthritis in horses. Gentamicin (84.9%), marbofloxacin (79.3%) and ceftriaxone (72.4%) were the most effective antimicrobials, whereas high resistance of the isolates (>50%) was found to erythromycin (75.9%), clarithromycin (75.9%), penicillin (69%), clindamycin (58.6%), and streptomycin (55.2%). Multiple antibiotic resistance index (≥ 0.3) was identified in 50% (16/32) of the isolates, with highest resistance in Gram-negative bacterial isolates. Serum levels of amyloid A, C-reactive protein, fibrinogen, globulin, and total protein, as well as the number of nucleated cells in the synovial fluid had values above the reference for horses, reinforcing acute-phase proteins as biomarkers in diagnosis of septic arthritis. We highlighted the diversity of microorganisms that may be involved in equine septic arthritis, the high resistance of bacterial isolates to conventional antimicrobials, the high lethality of young horses with septic arthritis, and importance of in vitro antimicrobial susceptibility pattern tests to therapeutic approaches in the disease.

摘要：本研究对44例确诊化脓性关节炎（septic arthritis）的马的血清与滑液的病因、多重抗生素耐药指数（multiple antibiotic resistance index）以及急性期蛋白（acute-phase protein）谱展开了调查。研究采样对象为24月龄以内尚未接受驯服训练的幼龄马驹。对马的滑液样本进行培养，并对分离得到的细菌菌株采用18种抗菌药物开展体外多重耐药模式检测。同时评估了血液学指标、纤维蛋白原以及部分急性期蛋白（总蛋白、白蛋白、球蛋白、淀粉样蛋白A与C反应蛋白）的血清水平。统计分析环节，将微生物分离株划分为四组：G1组为分离结果呈阴性的受试动物，G2组为分离出革兰氏阴性菌的样本，G3组为分离出革兰氏阳性菌的样本，G4组为分离出真菌的样本。本次研究中，77.2%（32/44）的滑液样本成功获得微生物分离株。检出的优势致病菌包括：大肠杆菌（7/44=15.9%）、金黄色葡萄球菌（5/44=11.4%）、马链球菌马亚种（3/44=6.8%）、黑曲霉（3/44=6.8%）、铜绿假单胞菌（2/44=4.5%）、马链球菌兽疫亚种（1/44=2.3%）、化脓隐秘杆菌（1/44=2.3%）以及马红球菌（1/44=2.3%）。其中，黑曲霉首次被报道为马化脓性关节炎的原发致病菌。抗菌药物敏感性检测结果显示，庆大霉素（84.9%）、马波沙星（79.3%）与头孢曲松（72.4%）的抗菌活性最强；而分离菌株对红霉素（75.9%）、克拉霉素（75.9%）、青霉素（69%）、克林霉素（58.6%）以及链霉素（55.2%）的耐药率均超过50%。50%（16/32）的分离株呈现多重抗生素耐药指数≥0.3的特征，其中革兰氏阴性菌分离株的耐药性最高。受试马的血清淀粉样蛋白A、C反应蛋白、纤维蛋白原、球蛋白及总蛋白水平，以及滑液中有核细胞计数均超出马类参考值范围，证实急性期蛋白可作为化脓性关节炎诊断的生物标志物。本研究着重强调了以下几点：可能参与马化脓性关节炎发病的微生物多样性、细菌分离株对常规抗菌药物的高耐药性、幼龄马化脓性关节炎的高致死率，以及体外抗菌药敏试验对该病临床治疗方案制定的重要性。