COLI-AEROGENES BACTERIA FROM FARM DAIRY EQUIPMENT AND RAW MILK

SUMMARY: A series of 1,040 cultures of coli-aerogenes bacteria isolated at 30° from farm dairy equipment and raw milk was classified according to the recommendations of the Coliform Sub-Committee of the Society for Applied Bacteriology (Report, 1949). The distribution of species and types isolated from milk did not differ materially from that for dairy equipment, Klebsiella cloacae, K. aerogenes and Citrobacter freundii being the dominant species, while the incidence of Escherichia coli was relatively low. There was no marked seasonal incidence of any type, though E. coli I formed a slightly higher proportion of the coli-aerogenes microflora in winter, whereas K. aerogenes I was slightly higher in summer. Many of the cultures of the dominant types, K. cloacae, K. aerogenes I and Cit. freundii I, did not form acid and gas from lactose in two days at 37°. Consequently 37° negative, anaerogenic and paracolon strains constituted a relatively high proporton (49%) of the coli-aerogenes microflora.     

THE BACTERIOLOGY OF FARM WATER SUPPLIES: A STUDY OF THE COLONY COUNT IN 72 HOURS AT 22°

SUMMARY: The colony count at 22° of farm water supplies from springs and wells was mainly composed of biochemically inactive, non-pigmented, Gram-negative rods. Water from a stream polluted with farmyard sewage showed a similar dominance of Gram-negative rods, but orange or yellow pigmented colonies were more abundant. There were few 37° positive coli-aerogenes bacteria in either the farm water supplies or the sewage polluted stream, and Bact. coli type I was rare.
A high proportion of the bacteria from farm water supplies fermented milk in 3 days at 22°; a third developed acid, 15% proteolysis and 6.4% ropiness.
Contamination of pure spring water with surface soil from a heavily grazed pasture resulted in a hundredfold increase in colony count with aerobic sporing rods replacing Gram-negative rods as the dominant organisms, but coli-aerogenes bacteria were absent.     

THE MULTIPLICATION OF COLI-AEROGENES BACTERIA IN MILK STORED AT 3–5°

SUMMARY: When 108 samples of individual farm milk supplies were held at 3—5° for 72 hr, 35·2% showed increases in coli-aerogenes organisms of over one-hundredfold and 10·2% increases of more than one-thousandfold. The coli-aerogenes microflora after refrigeration was dominated by Klebsiella cloacae and K. aerogenes I. While some strains of all the coli-aerogenes types isolated showed growth, though sometimes scanty, on yeast-dextrose agar in 5 days at 3—5°, the majority of the strains of K. cloacae showed luxuriant growth under these conditions and can be considered as typical facultative psychrophiles of milk.     

Coli-aerogenes Bacteria on Plants

S ummary . Specimens of plant foliage and flowers collected in the region of Attica from various situations and geographical regions were examined over a period of 13 months for the presence of coli-aerogenes bacteria able to grow at 37°. Twenty-five (12.2%) of 204 specimens carried coli-aerogenes bacteria of which Escherichia coli type I was isolated from 12 (5.8%). Coli-aerogenes bacteria were seldom isolated from plants grown in uninhabited areas, and they occured more frequently during summer and autumn.
Vegetables and fruits sold in the central market of Athens are frequently contaminated with coli-aerogenes bacteria. Of 76 specimens of vegetables examined 66 (86.8%) were positive for coli-aerogenes bacteria, and 17 (22.3%) for E. coli type I. The figures from 41 specimens of fruits were 26 (65.8%) and 4 (9.7%), respectively.     

STUDIES OF THE DETERMINATION OF THE BACTERIUM COLI TYPE I CONTENT OF FARM WATER SUPPLIES

SUMMARY: A – comparison of the suitability of brilliant green bile broth and MacConkey's broth at 44° for the detection of Bacterium coli type I in farm water supplies, showed that 83.1% of the samples had no difference in the number of positive tubes at 44°, and only 5 samples (1.7%) had a significantly higher number of positive tubes in MacConkey's broth.
Of 707 strains of coli-aerogenes bacteria isolated from 44° positive tubes of both media, 94.5% were Bact. coli type I. Strains of Bact. coli type II and Bact. aerogenes type I which were 44° positive constituted 3.7% and 0.4% respectively, all of which were indole negative at 44°. In addition there were 10 strains (1.4%) of 44° positive Intermediate type II, 9 of which were indole positive at 44°.
An appreciable number (6.6%) of Bact. coli type I strains failed to give a positive indole reaction in 24 hr at 44°.     

SOME OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Samples of water flowing into watercress beds had higher bacterial contents during the summer months although this was less marked among samples from deep underground sources. Outlet samples showed higher contents than inlet samples and the bacterial content varied markedly with season, being highest in summer.
The presumptive coli-aerogenes contents at 30°, 37° and 44° also showed a similar seasonal variation among samples from the outlets but the marked inferiority of samples other than from bores was no longer apparent after the water had flowed through the beds. The dominant types were Bact. aerogenes type I, pectate liquefiers, Bact. coli type I, and Intermediate type I.
The importance of the pectate liquefiers was confirmed by plating on pectate gel and by their isolation from these plates and from MacConkey's broth.     

Evaluation of coliforms as indicators of water quality in India.

The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.     

SOME BIOCHEMICAL CHARACTERISTICS OF FRESHLY ISOLATED STRAINS OF THE GENUS SERRATIA

SUMMARY: Many of 110 strains of Serratia , isolated from soil, water, milk and dairy equipment, were biochemically closely related to the coli-aerogenes bacteria. Acid and gas was formed from glucose in 14 days at 30° by 53% and from lactose and MacConkey's broth by about 40%. All except one strain gave——++ IMViC reactions.
An inverse relationship was observed between depth of pigmentation and carbohydrate fermentation. Complete loss of pigment in mutant strains was not uncommon, and was associated with loss of proteolytic properties and increase of saccharolytic activity.
The majority of the strains had psychrophilic characteristics: 75% grew at 3–5°. Most strains showed moderate growth at 37°, but only 7 formed red pigment at that temperature.
All strains resembled Serratia marcescens in morphology, containing minute coccoid rods smaller than those of coli-aerogenes bacteria.     

FURTHER OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Observations on two watercress beds in Kent have confirmed previous findings (Jones & Baker, 1955) that even in comparatively well-protected beds the coli-aerogenes content of the water may be high in summer. They have also shown that in spite of circumstances which would lead one to expect pollution, as in the case of one bed, the coli-aerogenes content can be low in winter. The season appears to influence the content in the water of coli-aerogenes bacteria, pectate liquefying bacteria and those capable of growing at 37°, but in the case of those growing at 22° other factors can play a more important part, as higher counts were not uncommon in winter. Seasonal effects were less marked with inlet samples; they were less influenced by atmospheric temperature, and little extraneous contamination occurred. Numbers increased as the sampling point moved from inlet to outlet.     

THE DETERMINATION OF THE COLI-AEROGENES CONTENT OF MILK AND DAIRY EQUIPMENT BY PLATING ON VIOLET RED BILE AGAR INCUBATED AT 30°

SUMMARY: Violet red bile agar (VRB) incubated at 30° for 20–24 hr was as good an indicator of coli-aerogenes bacteria in milk as MacConkey's broth. A high proportion (82%) of the large, deep red colonies considered to be formed by coli-aerogenes bacteria were confirmed as such. A British brand of dehydrated VRB agar was as suitable as an American brand of this medium for determining the coli-aerogenes content of milk. All the strains of typical coli-aerogenes bacteria tested formed red colonies. In a small proportion of cases the diameter was less than 0·5 mm. The only other milk bacteria which formed colonies resembling those of coli-aerogenes organisms were some acid forming strains of Gram-negative rods. Coli-aerogenes bacteria, determined on VRB agar at 30°, generally constituted only a small proportion of the microflora of fresh raw milk and of farm dairy equipment.     

THE EFFECT OF VARIOUS WATER BACTERIA ON THE GROWTH OF ESCHERICHIA COLI I IN MACCONKEY'S BROTH AT 37° AND 42°

SUMMARY: The growth of a streptomycin resistant strain of Escherichia coli I in MacConkey's broth at 37° or 42° was not inhibited by water organisms of the genera Micrococcus, Proteus, Achromobacter and Pseudomonas , but the presence of large numbers of other members of the coli-aerogenes group resulted in retardation or inhibition of its growth.     

COLD-TOLERANT FERMENTATIVE GRAM-NEGATIVE ORGANISMS FROM MEAT AND OTHER SOURCES

SUMMARY: From various chilled meats, twenty-eight strains of coli-aerogenes bacteria and one Aeromonas were isolated which grew well at +1±5° and some at −1±5°. The optimum growth temperature for most of these strains was nearer 37° than 30°. Nine strains (including the Aeromonas ) fermented lactose rapidly, the remainder slowly or not at all. All the strains which fermented lactose rapidly with the production of gas gave positive presumptive coli-aerogenes tests in MacConkey's broth at 30°, but only five were positive at 37°; none was positive at 44°. Because such organisms can attain populations of millions/cm², they could confuse the interpretation of presumptive coli-aerogenes tests made on chilled meat.     

Comparison of selective agars for the isolation and identification of Klebsiella oxytoca and Escherichia coli from environmental drinking water samples

Various selective media were assessed for their ability to detect and differentiate Klebsiella oxytoca and Escherichia coli in environmental water samples. Only two, Membrane Lauryl Sulphate agar and Deoxycholate Agar, could differentiate the two coliforms from each other and from the 'background' heterotrophs in water and this was a consequence of E. coli's ability to grow at 44°C and 37°C whereas Kl. oxytoca could only grow at 37°C. Modified M-FC medium effectively differentiated Kl. oxytoca but not E. coli in environmental samples. Other media characterized the different coliforms in pure culture but failed to do likewise in environmental samples. For example, pure cultures of E. coli fluoresced when MUG was added to the medium but single colonies on a mixed species plate failed to do so. MT7 agar distinguished the two coliforms from water heterotrophs but not from each other.     

TEMPERATURE-COMPENSATED TESTS FOR RAW MILK SUPPLIES. PART IV. STUDIES ON A KEEPING QUALITY TEST AT 19–20°

SUMMARY: A field-scale experiment carried out in Wales and the West Midlands, in which the temperature-compensated clot-on-boiling (C.O.B.) test of Rowlands & Hosking (1951) was applied to 11,626 samples of designated milk, morning, mixed and evening milk, gave proportions of failures in the ratio 1:2:3 respectively. Despite temperature compensation, failures varied according to atmospheric temperature from c. 50% at 72°F. or more to 10% at 56°F. or less and averaged 20% during the summer and 7% during the six winter months.
No marked differences were noted between the keeping qualities of tuberculin tested or accredited milk. During the winter no difference was found between producer-wholesaler and producer-retailer supplies, but the latter had a higher proportion of failures of evening and mixed milks during the summer.
In a set of 8,297 samples examined in addition by the methylene blue and coli-aerogenes tests, the C.O.B. test gave a lower incidence of failures than either the methylene blue or combined methylene blue and coli-aerogenes tests throughout almost the entire year. It is suggested that a temperature-compensated C.O.B. test is practicable as a routine procedure.     

THE INCIDENCE OF BACTERIUM COLI IN FARM WATER SUPPLIES

SUMMARY: Farm water supplies giving 37° positives in MacConkey's broth within 24 hr. had a much higher incidence of presumptive Bact. coli type I than those which gave 37° positives during the second day of incubation only; presumptive Bact. coli reactions were obtained with 85% of the 7,522 tubes positive in 24 hr. compared with 23% for the 7,593 tubes showing positive reactions during the second day at 37°.     

Evaluation of coliforms as indicators of water quality in India

P.W. RAMTEKE, J.W. BHATTACHARJEE, S.P. PATHAK AND N. KALRA. 1992. The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.     

Studies on Coli-aerogenes and Other Gram-negative Intestinal Bacteria in Various Animals and Birds

S ummary . Some faecal material from native animals and birds (especially) showed either no coli-aerogenes bacteria or contained types other than Escherichia coli I.
Amongst coli-aerogenes isolates, E. coli I was frequent but the high percentage of other biotypes indicated that the animal host may serve as a pool of intermediate and irregular strains. Paracolons and Proteus spp. were abundant, and Salmonella spp. were isolated from dogs and native animals possibly in contact with man.
Animals were only occasionally carriers of enteropathogenic E. coli serotypes and seldom of types locally important in the etiology of infantile diarrhoea, such as E. coli O26:B6 and O55:B5. In this series O86 serotypes other than the diarrhoeal strain isolated from babies were found. The results of the study indicated some degree of host specificity. In the group of 20 O serotypes (referred to as specific E. coli ), O8 was most commonly listed. Most strains were sensitive to chemotherapeutic agents but resistance of some strains especially to sulphonamide was recorded.
The implication of the presence in the animal gut of coli-aerogenes bacteria other than E. coli type I is discussed in relation to bacterial standards for drinking water.     

THE ASSOCIATED GROWTH OF STREPTOCOCCUS LACTIS AND ESCHERICHIA COLI

SUMMARY: The possibility that contamination of farmhouse starters by coli-aerogenes bacteria may be a factor in producing the subtle flavour of farmhouse Cheddar cheese has been discussed. The associated growth of Strep. lactis and E. coli I at 30° and 37° resulted in the rapid disappearance of E. coli from the mixtures, even though it had been the dominant organism in some of them originally. Mixtures containing Strep. lactis and an anaerogenic strain of E. coli still contained this variant at the end of a month, although in no definite ratio and in a very much reduced proportion. It is concluded that the components of coli-lactic starters to be used in the manufacture of cheese should be combined together in the vats.     

A COMPARISON OF 30° AND 37° AS INCUBATION TEMPERATURES IN THE PRESUMPTIVE COLIAEROGENES TEST FOR RAW AND PASTEURIZED MILK

SUMMARY: Incubation at 30° and 37° for the presumptive coli-aerogenes test for raw and pasterurized milk has been investigated. There were more positives at the lower temperature and it is suggested that in this test, incubation at 30° might provide a much better guide to the hygienic quality of both raw and pasterurized milk. The ability of the coli-aerogenes bacteria studied to ferment lactose in MacConkey's broth at 30° but not at 37° was found to be a stable factor which was unchanged by prolonged storage on agar slopes at room temperature or on continued incubation in MacConkey's broth at temperatures above the optimum for lactose fermentation.     

THE RAPID IDENTIFICATION OF ESCHERICHIA COLI I BY THE PRODUCTION AT 44° OF BOTH INDOLE AND GAS FROM LACTOSE

SUMMARY: The modification of the 44° test proposed by Mackenzie, Taylor & Gilbert (1948) is useful for the rapid identification of Escherichia coli I in water and foods. False positive tests caused by other coli-aerogenes bacteria, or by their association with other organisms, can be considered rare. Only a few E. coli I fail to produce indole or ferment lactose at 44°, and further confirmation for routine purposes is necessary only when the results at 44° are discordant, e.g. indole positive-lactose negative or indole negative-lactose positive.