Ray Partha, Knowlton Katharine F, Shang Chao, Xia Kang
Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States of America.
Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States of America.
PLoS One. 2014 Nov 6;9(11):e112343. doi: 10.1371/journal.pone.0112343. eCollection 2014.
Cephapirin, a cephalosporin antibiotic, is used by the majority of dairy farms in the US. Fecal and urinary excretion of cephapirin could introduce this compound into the environment when manure is land applied as fertilizer, and may cause development of bacterial resistance to antibiotics critical for human health. The environmental loading of cephapirin by the livestock industry remains un-assessed, largely due to a lack of appropriate analytical methods. Therefore, this study aimed to develop and validate a cephapirin quantification method to capture the temporal pattern of cephapirin excretion in dairy cows following intramammary infusion. The method includes an extraction with phosphate buffer and methanol, solid-phase extraction (SPE) clean-up, and quantification using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The LOQ values of the developed method were 4.02 µg kg(-1) and 0.96 µg L(-1) for feces and urine, respectively. This robust method recovered >60% and >80% cephapirin from spiked blank fecal and urine samples, respectively, with acceptable intra- and inter-day variation (<10%). Using this method, we detected trace amounts (µg kg(-1)) of cephapirin in dairy cow feces, and cephapirin in urine was detected at very high concentrations (133 to 480 µg L(-1)). Cephapirin was primarily excreted via urine and its urinary excretion was influenced by day (P = 0.03). Peak excretion (2.69 mg) was on day 1 following intramammary infusion and decreased sharply thereafter (0.19, 0.19, 0.08, and 0.17 mg on day 2, 3, 4, and 5, respectively) reflecting a quadratic pattern of excretion (Quadratic: P = 0.03). The described method for quantification of cephapirin in bovine feces and urine is sensitive, accurate, and robust and allowed to monitor the pattern of cephapirin excretion in dairy cows. This data will help develop manure segregation and treatment methods to minimize the risk of antibiotic loading to the environment from dairy farms.
头孢匹林是一种头孢菌素类抗生素，美国大多数奶牛场都在使用。当粪便作为肥料施用于土地时，头孢匹林通过粪便和尿液排泄进入环境，可能会导致对人类健康至关重要的抗生素产生细菌耐药性。畜牧业对头孢匹林的环境负荷尚未得到评估，这主要是由于缺乏合适的分析方法。因此，本研究旨在开发并验证一种头孢匹林定量方法，以了解奶牛经乳房内灌注后头孢匹林排泄的时间模式。该方法包括用磷酸盐缓冲液和甲醇进行萃取、固相萃取（SPE）净化，以及使用超高效液相色谱-串联质谱（UPLC-MS/MS）进行定量。所开发方法的粪便和尿液定量下限（LOQ）值分别为4.02 µg kg⁻¹和0.96 µg L⁻¹。这种可靠的方法分别从加标空白粪便和尿液样本中回收了>60%和>80%的头孢匹林，日内和日间变异均可接受（<10%）。使用该方法，我们在奶牛粪便中检测到痕量（µg kg⁻¹）的头孢匹林，在尿液中检测到高浓度（133至480 µg L⁻¹）的头孢匹林。头孢匹林主要通过尿液排泄，其尿液排泄受天数影响（P = 0.03）。乳房内灌注后第1天排泄峰值为（2.69 mg），此后急剧下降（第2、3、4和5天分别为0.19、0.19、0.08和0.17 mg），呈现二次排泄模式（二次项：P = 0.03）。所描述的牛粪便和尿液中头孢匹林定量方法灵敏、准确且可靠，能够监测奶牛头孢匹林的排泄模式。这些数据将有助于制定粪便分离和处理方法，以尽量减少奶牛场抗生素对环境负荷的风险。
