The effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum in 20-ppm free chlorine

Cyanuric acid is used to stabilize free chlorine to reduce photodegradation in outdoor swimming pools. While there have been numerous studies examining its effect on the disinfection rates of bacteria and viruses, it is not known whether cyanuric acid can significantly impact the effectiveness of hyperchlorination for inactivating Cryptosporidium oocysts present in fecally-contaminated swimming pools. This study examined the effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum under swimming pool hyperchlorination conditions (20 mg/ml free chlorine). When 50 mg/L cyanuric acid was present there was a 0.70-log₁₀ reduction in oocyst viability after 10 hours as compared to a 3.7-log₁₀ reduction without cyanuric acid. Aids to remediation, such as decreasing the pH to enhance the germicidal efficiency of the free chlorine and doubling the amount of free chlorine residual, were still unable to achieve a 3-log₁₀ reduction. Current public health recommendations for hyperchlorination and pool remediation are insufficient for pools using cyanurate-stabilized chlorine to achieve a three log inactivation of the parasite.     

The effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum in 20-ppm free chlorine

Cyanuric acid is used to stabilize free chlorine to reduce photodegradation in outdoor swimming pools. While there have been numerous studies examining its effect on the disinfection rates of bacteria and viruses, it is not known whether cyanuric acid can significantly impact the effectiveness of hyperchlorination for inactivating Cryptosporidium oocysts present in fecally-contaminated swimming pools. This study examined the effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum under swimming pool hyperchlorination conditions (20 mg/ml free chlorine). When 50 mg/L cyanuric acid was present there was a 0.70-log10 reduction in oocyst viability after 10 hours as compared to a 3.7-log10 reduction without cyanuric acid. Aids to remediation, such as decreasing the pH to enhance the germicidal efficiency of the free chlorine and doubling the amount of free chlorine residual, were still unable to achieve a 3-log10 reduction. Current public health recommendations for hyperchlorination and pool remediation are insufficient for pools using cyanurate-stabilized chlorine to achieve a three log inactivation of the parasite.     

连续消毒对水中大肠杆菌抗力曩探讨

Under defined conditions E. coli were subjected to repeated chlorine disinfections 10 times. The survival E. coli at 30 s (A10), and the survival E. coli at 10 min (B10) had no difference in resistance to chlorine to their original strain (A0). However, the compound E. coli (C10) survived at various contact time showed an increased resistance than their original strain (A10), the degree of increased resistance varying with different conditions of disinfection. E. coli C1(0) lost its increased resistance after it has been passaged 10 times on nutrient agar.     

Studies on porphyrin-heme biosynthesis in organotypic cultures of chick dorsal root ganglia. II. The effect of lead.

Organotypic cultures of chick dorsal root ganglia retain the morphology and the metabolism of intact nervous tissues which are observed in vivo. Such cultures are capable of synthesizing porphyrins from a precursor, δ-aminolevulinic acid (ALA). The present study was undertaken to estimate the capacity of these cultures to form porphyrins from ALA and to study the effect of lead on porphyrin formation. Control cultures which were not incubated with ALA did not show detectable amounts of porphyrins. On the other hand, cultures incubated with ALA synthesized porphyrins linearly as a function of ALA concentration up to 2 mm as well as a function of incubation period for up to 24 hr. The major porphyrin synthesized by the cultures was uroporphyrin as demonstrated by its characteristic fluorescence emission spectrum and by its migration on thin-layer chromatographic plates. Porphyrin formation was inhibited 50% after treatment with lead at 10 μm; this was accompanied by a shift toward the formation of coproporphyrin and protoporphyrin. These results indicate that isolated chick dorsal root ganglion cultures are able to synthesize a full spectrum of porphyrins from ALA and that an inhibitory effect of lead on porphyrin formation can be demonstrated in such cultures. These data suggest the usefulness of organotypic cultures of chick dorsal root ganglia for the study of the effects of environmental chemicals on porphyrin — heme biosynthesis in isolated nervous tissues.     

前馈控制对消毒供应中心洗消合格率及骨科手术患者切口感染率的影响

目的　探讨实施前馈控制措施对医院消毒供应中心洗消合格率及骨科手术患者切口感染率的影响。方法　比较我院消毒供应中心实施前馈控制措施前后,洗消合格率以及骨科手术患者切口感染率的变化。结果　实施前馈控制措施前后,医疗器械的采样合格率分别为86.02%和95.15%,清洗合格率分别为86.50%和97.50%,包装合格率分别为88.50%和95.50%,发放合格率分别为93.50%和96.50%,物品丢失率分别为0.93%和0.19%,差异均具有统计学意义（P均＜0.05）。实施前馈控制措施前后骨科手术患者切口感染率分别为5.00%和1.00%（P＜0.05）。实施前馈控制措施前后共检出病原菌29株,其中革兰阴性菌占58.62%,革兰阳性菌占41.38%。结论　前馈控制能够明显提高消毒供应中心医护工作人员的工作效率,发挥很好的预防控制作用,在一定程度上降低骨手术患者感染的风险。