Brown Mindy G, Balkwill David L
Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306-4300, USA.
Microb Ecol. 2009 Apr;57(3):484-93. doi: 10.1007/s00248-008-9431-6. Epub 2008 Aug 2.
Various natural environments have been examined for the presence of antibiotic-resistant bacteria and/or novel resistance mechanisms, but little is known about resistance in the terrestrial deep subsurface. This study examined two deep environments that differ in their known period of isolation from surface environments and the bacteria therein. One hundred fifty-four strains of bacteria were isolated from sediments located 170-259 m below land surface at the US Department of Energy Savannah River Site (SRS) in South Carolina and Hanford Site (HS) in Washington. Analyses of 16S rRNA gene sequences showed that both sets of strains were phylogenetically diverse and could be assigned to several genera in three to four phyla. All of the strains were screened for resistance to 13 antibiotics by plating on selective media and 90% were resistant to at least one antibiotic. Eighty-six percent of the SRS and 62% of the HS strains were resistant to more than one antibiotic. Resistance to nalidixic acid, mupirocin, or ampicillin was noted most frequently. The results indicate that antibiotic resistance is common among subsurface bacteria. The somewhat higher frequencies of resistance and multiple resistance at the SRS may, in part, be due to recent surface influence, such as exposure to antibiotics used in agriculture. However, the HS strains have never been exposed to anthropogenic antibiotics but still had a reasonably high frequency of resistance. Given their long period of isolation from surface influences, it is possible that they possess some novel antibiotic resistance genes and/or resistance mechanisms.
人们已经对各种自然环境中抗生素抗性细菌和/或新型抗性机制的存在情况进行了研究，但对于陆地深层地下环境中的抗性情况却知之甚少。本研究考察了两个深层环境，它们与地表环境及其内部细菌的已知隔离时间不同。从位于南卡罗来纳州美国能源部萨凡纳河场地（SRS）和华盛顿州汉福德场地（HS）地表以下170 - 259米处的沉积物中分离出154株细菌。对16S rRNA基因序列的分析表明，两组菌株在系统发育上具有多样性，可归为三到四个门中的几个属。通过在选择性培养基上平板培养，对所有菌株进行了对13种抗生素的抗性筛选，90%的菌株对至少一种抗生素具有抗性。SRS菌株中有86%、HS菌株中有62%对不止一种抗生素具有抗性。对萘啶酸、莫匹罗星或氨苄西林的抗性最为常见。结果表明，抗生素抗性在地下细菌中很普遍。SRS处抗性和多重抗性频率略高，部分原因可能是近期受到地表影响，比如接触农业中使用的抗生素。然而，HS菌株从未接触过人为抗生素，但仍有相当高的抗性频率。鉴于它们与地表影响长期隔离，有可能它们拥有一些新型抗生素抗性基因和/或抗性机制。
