Search PubMed⌕ Search

Biomedical subjects

V J Cabelli

Publications and source records attributed to V J Cabelli.

11 recordsLinked to original sources
PubMed1991

Evaluation of an Escherichia coli host strain for enumeration of F male-specific bacteriophages.

A method was developed for the selective enumeration of F male-specific bacteriophages in samples of environmental waters. The host strain for the phages, Escherichia coli HS(pFamp)R, has three antibiotic resistance markers, ampicillin on the Famp plasmid, which codes for pilus production, and streptomycin and nalidixic acid on the chromosome. The strain is resistant to coliphages T2 to T7 and phi X174. More than 95% of the phages from environmental samples which plaqued on the host strain were F male specific. The host bacterium had a higher plaquing efficiency than E. coli K-12 Hfr for F-specific phages in stock suspensions and sewage effluents. The F male-specific phage levels in prechlorinated, secondary-treated sewage effluents generally were about 10(3) to 10(4) PFU/100 ml. The levels in the influents to the sewage treatment plants and in septic tank contents were about 10(5) PFU/100 ml. RNA-containing phages composed about 90% of the total F-specific phage population in sewage effluents.

Bacteriophage phi X 174↗
PubMed1979

Membrane filter enumeration method for Clostridium perfringens.

A membrane filter procedure has been developed for the rapid quantitation of C. perfringens in the aquatic environment. Background growth is inhibited by the use of D-cycloserine, polymyxin B sulfate, and incubation at 45 degrees C. Differential characteristics include the fermentation of sucrose, production of acid phosphatase, and the absence of beta-D-glucosidase activity. The medium is prepared as follows (in grams per 100 ml of distilled water): tryptose, 3.0; yeast extract, 2.0; sucrose, 0.5; L-cysteine, 0.1; MgSO4. 7H2O, 0.01; bromocresol purple, 0.004; and agar, 1.5. The ingredients are dissolved, and the pH is adjusted to 7.6. After autoclaving at 121 degrees C for 15 min, the medium is allowed to cool at 50 degrees C, and the following are added per 100 ml: D-cycloserine, 40 mg; polymyxin B sulfate, 2.5 mg; indoxyl-beta-D-glucoside, 60 mg; 2.0 ml of a filter-sterilized 0.5% phenolpthalein diphosphate solution; and 0.2 ml of a filter-sterilized 4.5% FeCl3.6H2O solution. Enumeration of C. perfringens in a water sample is completed within 18 to 24 h. The verification of typical colonies was 93%. The average recovery from peptone-water spore suspensions of five strains was 79%, and that from filter-sterilized seawater suspensions was 90%. The precision of the method was approximately equal to that expected from random error alone. Confirmed recoveries of C. perfringens from water and sewage samples generally were greater than those by the Bonde pour tube method.

Bacteriological Techniques↗
PubMed1979

Limitations of the Moeller lysine and ornithine decarboxylase tests.

A total of 40 fecal and environmental isolates, including 26 Escherichia coli strains, 9 members of the genus Klebsiella, and 5 members of the genus Enterobacter, were tested by enzyme assay for their endogenous and induced levels of lysine decarboxylase and ornithine decarboxylase when grown in Moeller decarboxylase medium. All of the coliforms examined had measurable lysine decarboxylase and ornithine decarboxylase activities whether or not they were positive in the Moeller test. In general, the Moeller lysine decarboxylase test reflected the inducibility of lysine decarboxylase whereas the Moeller ornithine decarboxylase test did not relect the inducibility of ornithine decarboxylase. Neither test measured the amount of intracellular enzyme; rather, they indicated whether the amount of polyamine liberated was sufficient to raise the pH of the culture medium above 7. Changing the growth conditions (i.e., the concentrations of glucose, lysine, and amino acids other than lysine) greatly influenced the lysine decarboxylase activity in coliforms. The limitations on the interpretation of the Moeller test results are discussed.

Bacteriological Techniques↗
PubMed1979

Membrane filter procedure for enumeration of Aeromonas hydrophila in fresh waters.

A membrane filter method (mA) for the enumeration of Aeromonas hydrophila in natural water samples was developed. The complex, primary medium employs trehalose as a fermentable carbohydrate and ampicillin and ethanol as selective inhibitors. After 20 h of incubation at 37 degrees C, an in situ mannitol fermentation test followed by an in situ oxidase test is used to further differentiate A. hydrophila from other aquatic and terrestrial microorganisms present in freshwaters. The primary medium decreases background microbial growth by about two orders of magnitude. The recoveries on mA medium from suspensions of A. hydrophila prepared from pure cultures and held for 24 h at 15 degrees C exceeded 95% of the recoveries on brain-heart infusion agar spread plates. The confirmation rate for colonies designated A. hydrophila was 98%, whereas 11% of the presumptively negative colonies were, in fact, A. hydrophila. Recoveries of A. hydrophila from fresh, surface water samples exceeded recoveries by the other methods examined.

Aeromonas↗
PubMed1979

Relationship of microbial indicators to health effects at marine bathing beaches.

Findings are described from the second year of an epidemiological-microbiological study conducted at New York City beaches as part of the U.S. Environmental Protection Agency program to develop health effects-recreational water quality criteria. Symptomatology rates among swimmers (defined as immersion of the head in the water) relative to nonswimming but beach-going controls at a "barely acceptable" (BA) beach and a "relatively unpolluted" (RU) beach were examined. Data were collected by contacting family groups at the beach on weekends, obtaining information on bathing activity, and then questioning them by phone some 8--10 days later. In addition measurements were made for a number of potential water quality indicators. It was observed that the symptom rates, categorized as gastrointestinal (GI), respiratory, "other", and "disabling" (stayed home, stayed in bed, consulted a physician), were higher among swimmers than nonswimmers. As in the pretest conducted the previous year, the rate of GI symptoms was significantly higher among swimmers relative to nonswimmers at the BA but not the RU beach. Children, Hispanic Americans, and the low-middle socioeconomic groups were identified as the most susceptible portions of the population.

Adolescent↗
PubMed1976

Membrane filter procedure for enumeration of Vibrio parahaemolyticus.

A membrane filtration procedure has been developed for the enumeration of Vibrio parahaemolyticus in marine waters. Background microbial growth on the primary medium was decreased through the use of sodium cholate and copper sulfate, high pH, 3% NaCl, and an elevated incubation temperature. A series of in situ tests was employed to obviate the picking of colonies for identification; thereby, the enumeration of V. parahaemolyticus was accomplished within 30 h. Confirmation of typical colonies approached 95%. Relative to immediate plating on brain heart infusion agar spread plates, the recovery of V. parahaemolyticus cells suspended in phosphate-buffered saline or in seawater held for 24 h at 4 to 6 degrees C was about 90%. Assay variability did not exceed that expected by chance. Recoveries of V. parahaemolyticus from coastal and estuarine surface waters exceeded those obtainable by other methods examined.

Culture Media↗
PubMed1975

Membrane filter procedure for enumerating the component genera of the coliform group in seawater.

A facile, quantitative, membrane filter procedure (mC) for defining the distribution of coliform populations in seawater according to the component genera was developed. The procedure, which utilizes a series of in situ substrate tests to obviate the picking of colonies for identification, also provides an estimate of the total coliform density. When pure cultures of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were suspended in seawater and held at 4 C for 24 h, between 56 and 100% of the cells which grew on nutrient agar spread plates at 35 C could be recovered by the mC procedure. Confirmation as coliforms of typical colonies from natural samples was about 95%. Assay variability was found to be insignificant. The recovery of coliforms from marine waters by the mC procedure was comparable to those obtainable by current methods. Klebsiella was differentiated by the urease reaction and E. coli by its ability to form indole. The confirmation frequencies for colonies designated as Klebsiella and E. coli by the in situ tests approached 95% for the former and 98% for the latter.

Bacteriological Techniques↗
PubMed1975

Membrane filter technique for enumeration of enterococci in marine waters.

A membrane filter procedure is described for the enumeration of enterococci in marine waters. The procedure utilizes a highly selective and somewhat differential primary isolation medium followed by an in situ substrate test for identifying colonies of those organisms capable of hydrolyzing esculin. The procedure (mE) was evaluated with known streptococci strains and field samples with regard to its accuracy, sensitivity, selectivity, precision, and comparability to existing methods. Essentially quantitative recovery was obtained with seawater-stressed cells of Streptococcus faecalis and S. faecium. Neither S. bovis, S. equinus, S. mitis, nor S. salivarius grew on the medium. The selectivity of the medium was such that a 10,000-fold reduction in background organisms was obtained relative to a medium which contained no inhibitors and was incubated at 35 C. About 90% of those typical colonies designated as enterococci confirmed as such and about 12% of the colonies not so designated were, in fact, identified as enterococci. Plate to plate variability across samples approximated that expected by chance alone. Verified recoveries of enterococci from natural samples by the mE procedure, on the average, exceeded those by the KF method by one order of magnitude.

Cell Count↗