Lec_13_Fate and Transport

Lec_13_Fate and Transport - Fate and Transport of Microbes...

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Fate and Transport of Microbes in Water, Soils and Sediments
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Microbial Survival in the Environment – Pathogens Pathogen survival: Differs widely among microbes: Bacteria: spores survive better than vegetative cells Also differs between Gram-positive and Gram-negative bacteria Some Gram-positives, e.g., enterococci, survive better than Gram-negatives, e.g., E. coli But, Gram-negative bacilli are more resistant than Gram-negative or Gram-positive cocci to antimicrobial chemicals Fungi: spores survive better than other forms Viruses: non-enveloped viruses survive better than enveloped viruses under most environmental conditions Envelopes are relatively fragile compared to outer capsids (protein coats)
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Survival of Selected Pathogens E.coli 0157:H7 Better survival at lower temperatures Can enter VBNC state In Water: >91 days at 8ºC; 49-84 days at 25ºC In Soil: Up to 8 wks at 25ºC; >99days under fluctuating temperature (-6 to 20ºC) In Manure: >1 year under fluctuating environmental conditions (non-aerated); 47- 120 days (aerated) Yersinia enterocolitica In Water: 64 weeks at 4ºC In Soil: 7-10 days at 30ºC
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Survival of Selected Pathogens Cryptosporidium parvum In Water: >12 weeks at 4ºC; 10 weeks at 25ºC In Soil: 8 weeks at 4ºC; 4 weeks at 25ºC In Manure: 8 weeks at 4ºC; 4 weeks at 25ºC Giardia lamblia Less stable under all conditions
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Survival of Selected Pathogens Poliovirus In Water: >70 weeks in groundwater at 8-10ºC In Soil: > 50 weeks at 8-10ºC In Sewage: 45 minutes in Raw Sewage at room temperature; 28 days in Septic Tank Effluent Norwalk Virus (by RT-PCR) In Water: >70 weeks In Soil: >70 weeks
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Survival Pathogen Survival time in fresh water and sewage at 20-30ºC Viruses Enteroviruses <120 days, but usually <50 Bacteria Fecal Coliforms <60 days, but usually <30 Salmonella <60 days, but usually <30 Shigella <30 days, but usually <10 Vibrio cholerae <30 days, but usually <5 Protozoa Entamoeba Histolytica <30 days, but usually <15 Cryptosporidium parvum >12 months Helminths Ascaris lumbricoides Many months Pathogen Survival time in soil at 20-30ºC Viruses Enteroviruses <100 days, but usually <20 Bacteria Fecal Coliforms <70 days, but usually <20 Salmonella <70 days, but usually <20 Vibrio cholerae <20 days, but usually <10 Protozoa Entamoeba Histolytica <20 days, but usually <10 Cryptosporidium parvum >12 months Helminths Ascaris lumbricoides Many months
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TEMPERATURE Greater Inactivation/death rates at higher temperatures Lower survival rates at higher temperatures But, some microbes will grow or grow better at higher temperatures Many microbes survive better at lower temperature Some bacteria experience “cold injury” or“cold shock” and cold inactivation; VBNC Thermal inactivation differs between dry heat and moist heat Dry heat is much less efficient than moist heat in inactivating
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Lec_13_Fate and Transport - Fate and Transport of Microbes...

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