Bacteria in Daily Life

by Grace C. Frankland

Out at sea, beyond the reach of land breezes, it is no uncommon thing to find none whatever; on mountains and even hills of humble elevation the paucity of bacteria is very marked if there are no abnormal or untoward circumstances contributing to their distribution. In illustration of this the recent investigations of the air on the summit of Mont Blanc by M. Jean Binot are of especial interest, inasmuch as the altitude at which they were carried out is the highest at which the search after bacteria has so far been pursued. This intrepid investigator spent no less than five days in the observatory, which is situated on the top of the mountain. As was to be anticipated, frequently no bacteria at all were found, and it was only when such comparatively large volumes of air as one thousand litres (about 200 gallons) were explored that microbes in numbers varying from four to eleven were discovered. The air of the country is far freer from microbial life than that of cities; whilst open spaces, such as those afforded by the London parks, are paradises of purity compared with the streets with their attendant bacterial slums.

That it is no exaggeration to describe streets from the bacterial point of view as slums is to be gathered from the fact that much less than a thimbleful of that dust which is associated with the blustering days of March and the scorching pavements of summer may contain from nine hundred to one hundred and sixty millions of bacteria. But investigators have not been content to merely quantitatively examine street dust; in addition to estimating the numerical strength of these bacterial dust-battalions, the individual characteristics of their units have been exhaustively studied, and the capacity for work, beneficent or otherwise, possessed by them has been carefully recorded. The qualitative discrimination of the bacteria present in dust has resulted in the discovery of, amongst other disease germs, the consumption bacillus, the lock-jaw or tetanus bacillus, bacteria associated with diphtheria, typhoid fever, pulmonary affections, and various septic processes. Such is the appetising menu which dust furnishes for our delectation.

There can be no doubt, therefore, that dust forms a very important distributing agent for micro-organisms, dust particles, aided by the wind, being to bacteria what the modern motor-car, with its benzine or electric current, is to the ambitious itinerant of the present day. Attached to dust, bacteria get transmitted with the greatest facility from place to place, and hence the significance of their presence in dust.

Mention has been made of the fact that the germs of typhoid fever have been discovered in dust, and the belief in the possibility of this disease being spread by dust is gaining ground.

An interesting case in point is afforded by an outbreak of typhoid fever which occurred in Athens a few years ago, and in which the starting-point or nucleus was discovered to be a group of labourers who were engaged upon excavating the soil in a street through which a sewer had once been taken. The epidemic subsequently spread to those districts of the city swept by the prevailing wind, which passed over the place where the soil had been turned up and exposed. M. Bambas, who brought his observations before the International Congress of Hygiene at Buda-Pesth, was convinced from the inquiries he made that this outbreak of typhoid was due to the disturbance of the soil and the dissemination by means of the wind of typhoid-dust-particles to certain parts of the city.

That this hypothesis is by no means without experimental justification is shown by the properties possessed by the typhoid bacillus in regard to its vitality in soil which have been discovered. Thus numerous investigators have studied the important question of the behaviour of this micro-organism in soil, and have found that it can exist over periods extending from three to twelve or more months in the ground. This property of the typhoid bacillus may possibly explain the appearance over and over again of typhoid fever in particular localities, suggesting that the bacteria had become indigenous in the soil.

Dr. Mewius, of Heligoland, describes an epidemic of typhoid fever in the island, concerning which he made a most searching and elaborate inquiry. It appears that a case of typhoid occurred and was concealed from the medical authorities, so that no steps for disinfection could be taken in the first instance; and, following the primitive custom which prevails on the island, the dejecta was thrown over and upon the cliffs, this being the usual method of disposing of sewage. Ample opportunity was thus given for its desiccation and subsequent distribution as dust. That this typhoidal matter did subsequently become pulverised and spread the infection Dr. Mewius has no doubt, the germs having been conveyed to the open rain-water cisterns which constitute the water-supply of the majority of the inhabitants. His theory is again supported by the coincidence between the prevailing direction of the wind and the quarter where the outbreak occurred.

That diphtheria germs can remain for a long time in a living and, what is more, virulent condition in dust has been clearly demonstrated by Germano, amongst other investigators, this organism being specially endowed with the capacity for resisting the, to other microbes, lethal effect of getting dried up.

Bacteria, however, survive this desiccation process much better when they are herded together in large numbers than when they have to face such untoward conditions as isolated individuals. This has been well illustrated in the case of diphtheria bacilli, and the difference in their powers of endurance under these respective conditions is very striking. Thus when a few only were exposed to a very dry atmosphere on silken threads they disappeared after eight days; but when somewhat larger numbers were taken they contrived to exist for eighteen days, whilst when great multitudes of them were herded together even one hundred and forty days' starvation in these desert-like surroundings could not entirely stamp out their vitality.

This dangerous property possessed by the germs of diphtheria should, if possible, increase the vigilance with which the outbreaks of this disease are watched and dealt with. Abel cites an instance in which a wooden toy in the sickroom of a child suffering from diphtheria was found six months later to have virulent diphtheria bacilli upon it.