不同样品处理方法对鸡蛋表面菌落总数及菌相的影响

Effect of Different Sample Treatment Methods on Aerobic Bacterial Count and Bacterial Flora of Eggshell

试验旨在分析比较同一来源鸡蛋采用蛋壳擦拭、蛋壳清洗、蛋壳破碎3种蛋壳处理方法制备的样品中菌落总数、菌相、相对丰度的区别。对市售鸡蛋、鸡场鸡蛋以及人为污染鸡蛋分别采用三种蛋壳处理方法制备样品,按照《GB4789.2-2010食品卫生微生物学检验菌落总数测定》进行菌落总数计数,扫描电镜观察蛋壳结构,Miseq测序分析菌种多样性。结果表明,清洗法处理样品检测到的菌落总数最多,平均为(5.21±0.34)log CFU/个蛋壳,蛋壳破碎为(4.76±0.40)log CFU/个蛋壳、蛋壳擦拭(4.89±0.56)log CFU/个蛋壳。电镜观察显示采用超声波清洗处理的蛋壳表面凹凸不平,有孔径大小不一的孔洞,而擦拭法结构较为完整。Miseq测序结果表明3个样品的有效序列主要属于厚壁菌门(Firmicutes)和变形菌门(Proteobacteria),蛋壳破碎处理样品中埃希氏杆菌-志贺氏杆菌属相对丰度较大,为55.37%,而清洗法为2.29%,擦拭法仅为0.08%;清洗法以肠球菌属最多,为26.98%,擦拭法芽孢杆菌属丰度最大,为99.54%。结果表明蛋壳清洗法适合于蛋壳表面菌落总数计数样品的处理,蛋壳破碎法适合于蛋壳表面致病菌及鸡蛋腐败菌的检测。

The purpose of this study was to compare the effect of recovering bacteria from eggshells with shell rinse, shell crush and shell swab method on aerobic plate count and bacterial floral of eggshells. The samples from chicken farm,commercial market and artificially contaminated eggs were prepared by shell rinse,shell crush and shell swab. The aerobic plate count （APC）was determined according to GB4789.2-2010 Microbiological examination of food Hygiene： Detection of aerobic bacterial count. Uhrastructure of eggshell was observed by Scanning Electron Microscopy （SEM）. Bacterial diversity was studied based on 16 S rDNA （V4＋V5） sequences analyzed by Miseq. The APC of treated samples by shell rinse was （5.20±0.34）log CFU/eggshell,shell crush and shell swab were （4.76±0.40）log CFU/eggshell, （4.89±0.56） log CFU/eggshell,respectively;there was uneven surface with hole of different shapes and sizes on eggshell from shell crush under SEM;the sequencing results showed that effective sequences distributed in Firmieutes and Proteobacteria mostly, among of them shell crush sample obtained high abundance of Escherichia-Shigella （55.37%）, shell rinse and shell swab were 2.29% and 0.08% ,respectively;the high abundance of Enterococcus was 26.95% in shell rinse and high abundance of Bacillu was 99.54% in shell swab. Shell rinse method was suited for APC of eggshell and shell crush method was more effective at recovering Enterobacteriacese from eggshells.