Morozzi G, Cenci G, Caldini G, Sportolari R, Bahojbi A G
Ann Ig. 1989 Jan-Apr;1(1-2):351-62.
Antibiotic-resistance is widely spread phenomenon in the environment because of uncontrolled discharge of urban and animal wastewaters. Sewage treatment can significantly reduce the number of both sensitive and resistant bacteria. A reduction of about 1.5 logarithmic units in faecal coliforms was observed during biological treatment (3, 7), but a simultaneous increase in the percentage of resistant strains occurred because of not well understood selection phenomena. The above reported bacterial reduction is not always sufficient to meet the quality standards of Italian legislation required to discharge the treated effluents into surface waters, and so, chlorination become a compulsory additional treatment whose impact on both sensitive and resistant microflora must be evaluated. The results obtained in the present research have demonstrated that chlorine concentrations in the range of 0.5-2 ppm are able to reduce significantly the faecal coliforms concentrations and, in particular, treatment with 1 ppm of chlorine for 1 hour reduces the concentration of the above reported bacteria to the extent of 2 logarithmic units, so that their final concentration are of the about 10(2)/100 ml. The surviving chlorine tolerant bacteria seem to be antibiotic resistant in higher percentage than the chlorine sensitive ones and so, as a consequence, a significant increase in the antibiotic resistance and multiresistance was observed in the chlorinated effluents. In this context it is interesting to underline the larger variety of resistance patterns observed in the chlorine-resistant bacteria in comparison with the uniformity in the resistance patterns observed in isolated from unchlorinated effluents. The selected chlorine-tolerant strains seem to be less able to transfer their resistances under laboratory conditions, not because of curing effect of chlorine on the plasmids but, probably, because of the damage to cellular cell envelopes.
由于城市和动物废水的无节制排放，抗生素耐药性在环境中是一种广泛传播的现象。污水处理可以显著减少敏感菌和耐药菌的数量。在生物处理过程中，粪便大肠菌群数量减少了约1.5个对数单位（3, 7），但由于尚未完全了解的选择现象，耐药菌株的百分比同时增加。上述报道的细菌减少量并不总是足以满足意大利法律规定的将处理后的废水排放到地表水中的质量标准，因此，氯化成为一种强制的额外处理方法，其对敏感和耐药微生物群落的影响都必须进行评估。本研究获得的结果表明，0.5 - 2 ppm范围内的氯浓度能够显著降低粪便大肠菌群浓度，特别是用1 ppm的氯处理1小时可将上述细菌的浓度降低2个对数单位，使其最终浓度约为10²/100 ml。存活的耐氯细菌似乎比氯敏感细菌具有更高百分比的抗生素耐药性，因此，在氯化废水中观察到抗生素耐药性和多重耐药性显著增加。在这种情况下，值得注意的是，与从未氯化废水中分离出的细菌所观察到的耐药模式的一致性相比，在耐氯细菌中观察到了更多样化的耐药模式。所选的耐氯菌株在实验室条件下似乎较难转移其耐药性，这不是因为氯对质粒的消除作用，而是可能因为对细胞包膜的损伤。
