A STUDY OF TWO HUNDRED CULTURES OF GRAM-NEGATIVE BACILLI ISOLATED FROM CASES OF GENITO-URINARY INFECTION

The Distribution and Sanitary Significance of B. coli, B. lactis aerogenes and Intermediate Types of Coliform Bacilli in Water, Soil, Faeces, and Ice-Cream

This section of the work deals with the routine bacteriological examination of 2144 samples of water, of which 1102 contained lactose-fermenting bacilli, 4333 strains being isolated. Twelve strains which liquefied gelatine and 24 which gave anomalous MR and VP reactions were excluded from the coliform group; the remaining 4297 cultures were classified on the basis of the MR, VP, indol, citrate and uric acid tests.

The ecology and significance of the different types of coliform bacteria found in water: A review of the literature

1. A review has been made of literature on the ecology of different types of coliform bacteria. The main object of the review has been to consider whether there is evidence to support the view thatBact. aerogenesand the intermediate types live normally on plants or in the soil and not in the intestines of man and other animals.

2. There is ample evidence thatBact. coliis by far the most common type of coliform in normal human faeces. On the other hand, there is evidence thatBact. aerogenesor intermediate types are usually present in faeces, may sometimes be present in greater numbers thanBact. coli, and on rare occasions may be the only type present. Both quantitatively and qualitatively the coliform flora of the faeces of an individual person may vary from day to day. There is insufficient evidence on the numbers ofBact. aerogenesand intermediate types in faeces to justify any more definite statement, but limited data suggest that such types may be absent or may be present in numbers of the order of a million per gram.

3. When fresh faeces are stored there is first a multiplication of such bacteria as will grow on ordinary laboratory media, including the coliform types. The rate of multiplication, as with the flora of soil, water, and milk, increases with an increase in the incubation temperature to 37° C, but the period of multiplication becomes shorter. In the literature consulted no evidence can be found to show which groups are prominent in the multiplication. Results are in agreement that on further storage the ratio of the numbers ofBact. colito those ofBact. aerogenesand intermediates decreases, the typicalBact. coliflora dying off more rapidly than other conform types. The rapidity of decrease appears to depend partially at least upon the temperature of the environment, and the decrease may be accelerated by intense sunlight.

4. In urine from patients suffering from genito-urinary infections the dominant types of coliform are usually eitherBact. aerogenesor intermediates. No data on the number of such organisms in urine have been obtained from the works consulted.

5. There is no-evidence that coliform bacteria multiply on fresh grasses or grains. Few quantitative data on this question have been found. In some of the older work it is doubtful whether a large proportion of the cultures isolated were actually coliform bacteria or whether they were species of other genera capable of fermenting lactose at 30° C. but not at 37° C. In the decomposition of grasses and legumes during ensilage, a process involving a considerable increase in temperature, it would appear that multiplication of conform bacteria may take place and counts may for a time equal those found in fresh faeces. No indication has been found that this multiplication is confined toBact. aerogenesor intermediates.

6. Most workers who have studied the coliform bacteria in soil have ignored the quantitative aspects and no counts at intervals over long periods of coliform bacteria in any undisturbed soil appear to have been made. No evidence of any multiplication of coliform bacteria in soil has been found. Results, however, are in agreement that where pollution of the soil by animal excreta has taken place, the heavier the pollution the greater is the number of coliform bacteria; soils relatively free from human or other animal pollution either contain no coliform bacteria or only small numbers. It is generally agreed that the ratio of the numbers ofBact. colito those ofBact. aerogenesand intermediates decreases with the increase of time which has elapsed since pollution of the soil. This change is similar to that which occurs in faeces during storage.

7. There is insufficient evidence to justify the definite statement often made thatBact. aerogenesand intermediates are normal inhabitants of soils, grasses, and grains.

The Classification of the Colon-Aerogenes Group of Bacteria in Relation to their Habitat and its Application to the Sanitary Examination of Water Supplies in the Tropics and in Temperate Climates: A Comparative Study of 2500 Cultures

(1) The ”lactose+ indol+” index as employed in temperate climate is usually an adequate criterion of water purity.

(2) Where a positive test does not appear to be substantiated by the sanitary findings, a further differentiation of the organisms isolated becomes necessary. The methyl-red and citrate tests have been found to supply that differentiation in a satisfactory manner.

(3) In the Tropics, false positive “lactose-indol” tests are commonly encountered, owing to the presence in large numbers in soil and water of organisms derived from sources other than recently excreted faeces.

(4) In the Tropics, the lactose-indol test should always be confirmed by the methyl-red, citrate and saccharose tests or such other reactions or groups of reactions as may be found by a local survey to be applicable.

My very grateful thanks are due to Dr P. A. Clearkin, Deputy Director of Laboratory Service, Tanganyika Territory, for his ready advice and constant encouragement; and also to Mr W. Whitley, Analytical Chemist, who performed a chemical analysis of the water samples, and very kindly gave me the benefit of his opinion on them. In addition I have to thank Dr R. R. Scott, Medical Officer of Health, and the Staff of the Health Office, Dar-es-Salaam, who have rendered every facility in the choice and collection of samples. It is a pleasure to be able to record once more my indebtedness to Prof. Bigger, of Trinity College, Dublin, whose fund of valuable suggestions and kindly criticism has been ever at my disposal.

The bacteriology of urinary infections in paraplegia

Two hundred and forty-seven strains of micro-organisms were isolated from the urinary tract of 121 patients with neurological complaints leading to paraplegia. The commonest infecting organism was E. coli and the commonest type of Proteus was P. mirabilis. Infections with more than one type of organism were present in 37% of urine specimens, and in such cases the incidence of E. coli was lower and that of Strep. faecalis higher than the incidences in infections with only one type of organism. No evidence was found which might suggest that the various bacterial species encountered showed either an undue degree of synergism or of mutual antagonism. Coliforms were the commonest primary pathogens, but Strep. faecalis and Proteus species occurred with the same frequency as the coliforms when they were considered as secondary invaders. The variance between the incidences of various species as reported by different workers is considered to be due to the different illnesses and conditions which predispose to urinary tract infection. It appears that infections in the urinary tract by more than one type of organism at a time occur more frequently in those patients with the more chronic predisposing causes. (Some disparity in findings may also result from the differing taxonomic methods employed by different workers, but this is probably insufficiently important to account for the largest differences.)

A comparative study of coliform organisms found in chlorinated and in non-chlorinated swimming bath water

The investigation deals with the bacteriological examination of 386 samples of water from Manchester swimming baths where the method of purification could be studied.

There were 339 samples from chlorinated pools of which 160 gave acid and gas in MacConkey broth at 37° C. and 2130 strains were isolated. The remaining forty-seven samples were from untreated open-air pools. Thirty of these samples were positive and 270 strains were isolated. The strains were classified according to Wilson's method into thecoli, intermediate,aerogenesand irregular groups, and only 1·78% of the total were found to be irregular. Both series of samples included more than 72% which containedcoli, and among the chlorinated samples no less than 70% yieldedaerogenesand nearly 49% intermediate type, while among the non-chlorinated baths there were 43% withaerogenesand 40% with intermediate type. There was a similar difference in the proportions ofcoli, aerogenesand intermediate type in chlorinated and in non-chlorinated baths when the results were considered on the basis of strains (Table II).

Since these differences in proportion were considered significant, and since the chief variation in conditions between outdoor and indoor baths consists of chlorination, a series of experiments was devised to test the effect of chlorine on pure cultures ofcoli, aerogenes, and intermediate type. There was very little change after adding 0·1 part of chlorine per million, but the addition of 0·3 and 0·5 part was followed by very rapid reduction in numbers with diminution in free chlorine. This reduction was on the whole least withaerogenes. The numbers continued to fall for about 48 hr. until all trace of chlorine had disappeared and then regrowth occurred. This regrowth was most vigorous and most rapid withaerogenes(see figures) but was very slow in all cases.

The Type of Coliform Bacilli Prevalent in Urine and their Significance, with Special Reference to the Sanitary Aspects

1. 1000 urinary and 500 faecal cultures of coliform bacteria were studied by means of the methyl-red, citrate and indol tests and also by their fermentation reactions upon saccharose and dulcite.

2. 8 per cent, of the faecal strains and 52 per cent, of the urinary strains were of theaerogenestype,i.e.methyl-red negative and citrate positive. Indol was produced in 94 per cent, and 43 per cent, of cases respectively.

3. This would suggest additional evidence that thecoligroup are quickly outnumbered by theaerogenesgroup once they leave the faeces, and also that the presence of theaerogenestype is not confined even in large numbers to an extra-corporeal habitat.

4. In water bacteriology the constancy or change in the relative proportions ofcoliandaerogenesstrains present is the goal at which to aim. Theaerogenesvariety cannot of itself be regarded as non-excretal or even non-faecal.

5. From a sanitary standpoint, the classification of coliform bacteria by means of the methyl-red and citrate tests cannot be regarded as entirely free from error so long as (a) theaerogenesstrains are found in faeces, in however small numbers, (b) these strains occur as the predominant type in urine, and (c) intermediate strains are found in the faeces, urine, soil and water.

6. The principal value of these tests lies in their comparative specificity in identifyingB. coliof immediate faecal origin. The presence of such an organism, interpreted together with the indol test, may be said to suggest dangerous faecal pollution if found prominently in a water sample. The presence of other types identified by the same tests cannot be regarded as having the same significant value in regard to a negative opinion.

7. A plea is made for a further study of coliform bacteria by means of the tests described in relation to the biological behaviour of the bacteria under different environmental conditions.