Comparison of the recoveries of Escherichia coli and total coliforms from drinking water by the MI agar method and the U.S. Environmental Protection Agency-approved membrane filter method.

Drinking water regulations under the Final Coliform Rule require that total coliform-positive drinking water samples be examined for the presence of Escherichia coli or fecal coliforms. The current U.S. Environmental Protection Agency-approved membrane filter (MF) method for E. coli requires two media, an MF transfer, and a total incubation time of 28 h. A newly developed MF method, the MI agar method, containing indoxyl-beta-D-glucuronide and 4-methylumbelliferyl-beta-D-galactopyranoside for the simultaneous detection of E. coli and total coliforms, respectively, by means of their specific enzyme reactions, was compared with the approved method by the use of wastewater-spiked tap water samples. Overall, weighted analysis of variance (significance level, 0.05) showed that the new medium recoveries of total coliforms and E. coli were significantly higher than those of mEndo agar and nutrient agar plus MUG (4-methylumbelliferyl-beta-D-glucuronide), respectively, and the background counts were significantly lower than those of mEndo agar (< 5%). Generally, the tap water source, overall chlorine level, wastewater source, granular activated carbon treatment of the tap water, and method of grouping data by E. coli count for statistical analysis did not affect the performance of the new medium.

New medium for the simultaneous detection of total coliforms and Escherichia coli in water.

A new membrane filter agar medium (MI agar) containing a chromogen, indoxyl-beta-D-glucuronide, and a fluorogen, 4-methylumbelliferyl-beta-D-galactopyranoside, was developed to simultaneously detect and enumerate Escherichia coli and total coliforms (TC) in water samples on the basis of their enzyme activities. TC produced beta-galactosidase, which cleaved 4-methylumbelliferyl-beta-D-galactopyranoside to form 4-methylumbelliferone, a compound that fluoresced under longwave UV light (366 nm), while E. coli produced beta-glucuronidase, which cleaved indoxyl-beta-D-glucuronide to form a blue color. The new medium TC and E. coli recoveries were compared with those of mEndo agar and two E. coli media, mTEC agar and nutrient agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide, using natural water samples and spiked drinking water samples. On average, the new medium recovered 1.8 times as many TC as mEndo agar, with greatly reduced background counts (< or = 7%). These differences were statistically significant (significance level, 0.05). Although the overall analysis revealed no statistically significant difference between the E. coli recoveries on MI agar and mTEC agar, the new medium recovered more E. coli in 16 of 23 samples (69.6%). Both MI agar and mTEC agar recovered significantly more E. coli than nutrient agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide. Specificities for E. coli, TC, and noncoliforms on MI agar were 95.7% (66 of 69 samples), 93.1% (161 of 173 samples), and 93.8% (61 of 65 samples), respectively. The E. coli false-positive and false-negative rates were both 4.3%. This selective and specific medium, which employs familiar membrane filter technology [corrected] to analyze several types of water samples, is less expensive than the liquid chromogen and fluorogen media and may be useful for compliance monitoring of drinking water.

Evaluation of eight bioaerosol samplers challenged with aerosols of free bacteria.

The need to quantify airborne microorganisms in the commercial microbiology industry (biotechnology) and during evaluations of indoor air quality, infectious disease outbreaks, and agriculture health investigations has shown there is a major technological void in bioaerosol sampling techniques to measure and identify viable and nonviable aerosols. As commercialization of microbiology increases and diversifies, it is increasingly necessary to assess occupational exposure to bioaerosols. Meaningful exposure estimates, by using area or environmental samplers, can only be ensured by the generation of data that are both precise and accurate. The Andersen six-stage viable (microbial) particle sizing sampler (6-STG) and the Ace Glass all-glass impinger-30 (AGI-30) have been suggested as the samplers of choice for the collection of viable microorganisms by the International Aerobiology Symposium and the American Conference of Governmental Industrial Hygienists. Some researchers consider these samplers inconvenient for evaluating industrial bioprocesses and indoor or outdoor environments. Alternative samplers for the collection of bioaerosols are available; however, limited information has been reported on their collection efficiencies. A study of the relative sampling efficiencies of eight bioaerosol samplers has been completed. Eight samplers were individually challenged with a bioaerosol, created with a Collison nebulizer, of either Bacillus subtilis or Escherichia coli. The samplers were evaluated under controlled conditions in a horizontal bioaerosol chamber. During each experimental run, simultaneous samples were collected with a reference AGI-30 to verify the concentration of microorganisms in the chamber from run to run and day to day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal viruses, coliphages, and bacteria in aerosols and wastewater at a spray irrigation site.

Aerosol samples collected at the Muskegon County Wastewater Management System Number 1 spray irrigation site in Michigan by using the Army prototype XM2 Biological Sampler/Collector were examined for the presence of animal viruses, coliphages, and bacteria. Air samples, collected in Earle lactalbumen hydrolysate, and wastewater samples were filtered through a 0.45- and 1.2-micron membrane filter sandwich, pretreated with 10% beef extract (pH 7.0), and assayed for animal viruses by the plaque method on Buffalo green monkey kidney cells. Untreated air and wastewater samples were assayed for coliphages by the soft agar overlay method with three Escherichia coli hosts (ATCC 13706, 15597, and 11303) and for bacteria by the heterotrophic plate count method. Filtered air samples were assayed for coliphages by the most-probable-number method with the same three hosts. Although no animal viruses were detected in the aerosol samples, coliphages and bacteria were recovered. E. coli ATCC 13706 coliphage were recovered more often and in greater numbers than either of the other two types of coliphages. Concentrations of animal viruses, coliphages, and bacteria detected in the raw influent decreased as the wastewater was aerated and stored in the lagoons. No animal viruses were detected in the wastewater at the pump station just before distribution to the spray irrigation rigs. The most-probable-number method was more sensitive and consistent than the overlay procedure in detecting low levels of coliphages in air samples.

Risk of infection associated with a wastewater spray irrigation system used for farming.

The use of wastewater for agricultural purposes involves the potential risk of infection from microorganisms in the wastewater. The application of partially treated wastewater on farms has been reported in one study to be associated with human illness, but this has not been confirmed. In the present study, workers at a land application system involving low-pressure spray irrigation of corn fields with wastewater were followed through a growing season to determine if they had an increased risk of infection as compared with a control population of the same socioeconomic group who had no direct exposure to wastewater. Enteroviruses were recovered from the wastewater used for irrigation, but not from the air during spraying. There was no increase in clinical illness among the workers and there was no evidence of an increased risk of infection. The workers who seemed at greatest risk, those who cleaned the spray nozzles, had higher antibody levels to one enterovirus, coxsackievirus B5, but acute symptomatic infections with viral excretion were not documented. This study indicates that there is very limited risk of infection among workers using partially treated wastewater for agriculture purposes.

Survival rates of parasite eggs in sludge during aerobic and anaerobic digestion.

The effects of mesothermic anaerobic or aerobic sludge digestion on survival of eggs from the roundworms Ascaris suum, toxocara canis, Trichuris vulpis, and Trichuris suis and from the rat tapeworm Hymenolepis diminuta were studied. Destruction of eggs throughout a 15-day treatment period, as well as their viabilities after reisolation, was analyzed. The laboratory model digesters used in this study were maintained at a 15-day retention schedule, partially simulating a continuously operating system. Ascaris eggs were destroyed in the anaerobic (23%) or aerobic (38%) digesters, and 11% Trichuris eggs were destroyed in the aerobic digesters. Trichuris eggs in anaerobic digesters and Toxocara eggs in either anaerobic or aerobic digesters were not destroyed. Destruction of eggs in digesters was correlated with the state of the eggs before subjection to the treatment processes; i.e., some Ascaris and Trichuris eggs were already embryonated in host intestinal contents or feces and hence past their most resistant stage. The viabilities of Ascaris and Toxocara eggs that survived the digestion processes were greater in anaerobically treated than in aerobically treated material. Eggs from Hymenolepis were nonviable before use in the experiments. However, they were more effectively destroyed in aerobic digesters than in anaerobic digesters.

Demonstration of invasiveness of Vibrio parahaemolyticus in adult rabbits by immunofluorescence.

To determine possible pathogenesis of Vibrio parahaemolyticus-host-organ system interactions, studies of invasiveness were made by a direct fluorescent-antibody method. Broth cultures of live cells isolated from seafish or symptomatic humans were inoculated separately into ligated ileal loops of young New Zealand white rabbits. After suitable incubation, rabbits were sacrificed, and ileal loops and tissue specimens were aseptically removed. Ileal loops were prepared and stained with specific fluorescein-tagged antibody, and organ specimens were cultured for isolation of the inoculated Vibrio strain. All strains tested penetrated into the lamina propria of the ileum and were isolated from the cultured tissue specimens, indicating that the organism is capable of more than a superficial colonization of the gut. The presence of Vibrio in cultured tissue specimens suggests invasion of deeper tissue by either the lymphatic or the circulatory system.

Gamma radiation inactivation of coxsackievirus B-2.

The radioresistance of coxsackievirus B-2 was studied when the virus was suspended in Eagle minimal essential medium, distilled water, cooked ground beef, and raw ground beef and irradiated at various temperatures in a cobalt-60 gamma radiation source. The number of surviving viruses at given doses of radiation was determined by a plaque assay system. All destruction curves indicated a first-order reaction. When the virus was irradiated in minimal essential medium at temperatures of -30, -60, and -90 C, D values (in Mrad) were 0.69, 0.59, and 0.64, respectively. When the virus was suspended in water and irradiated at -90 C, the D value was 0.53. Cooked ground beef containing the virus was irradiated at temperatures ranging from 16 to -90 C. The D values were 0.70 (16 C), 0.76 (0.5 C), 0.68 (-30 C), 0.78 (-60 C), and 0.81 (-90 C). Raw ground beef containing the virus was irradiated at -30, -60, and -90 C, and the D values were respectively 0.75, 0.71, and 0.68. The D values indicate that the rate of viral inactivation was dependent on the suspending menstrum.

Delayed-incubation membrane-filter test for fecal coliforms.

A delayed-incubation membrane-filter technique for fecal coliforms was developed and compared with the immediate fecal coliform test described in Standard Methods for the Examination of Water and Wastewater (13th ed., 1971). Laboratory and field evaluations demonstrated that the delayed-incubation test, with the use of the proposed vitamin-free Casitone holding medium, produces fecal coliform counts which very closely approximate those from the immediate test, regardless of the source or type of fresh-water sample. Limited testing indicated that the method is not as effective when used with saline waters. The delayed-incubation membrane-filter test will be especially useful in survey monitoring or emergency situations when the standard immediate fecal coliform test cannot be performed at or near the sample site or when time and temperature limitations for water sample storage cannot be met. The procedure can also be used for analyzing the bacterial quality of water or waste discharges by a standardized procedure in a central examining laboratory remote from the sample source.