Chapter XVI 



SANITARY ASPECTS OF MARINE MICROBIOLOGY 



Treatises on "water bacteriology" are generally concerned primarily 

 with the study of the sanitary properties of domestic water supplies, swim- 

 ming pools, and sewage. For various reasons sea water is rarely consid- 

 ered. Nevertheless, the sea does present certain problems of interest to 

 sanitary engineers and students of pubhc health. Outbreaks of oyster- 

 borne typhoid and the development of beaches for recreational purposes 

 have focussed attention upon some of these problems in recent years. The 

 problems are of acute interest to those municipalities discharging raw or 

 partially treated wastes into oceans, bays, or estuaries. 



Human pathogens in sea water : — It is the consensus of opinion that 

 there are no autochthonous marine bacteria which infect man, but the lit- 

 erature is replete with contradictory accounts of the viability of adventi- 

 tious pathogens in sea water. Some workers hold that sea water is highly 

 lethal for bacteria from land-dwelling animals while other workers present 

 data which indicate that such bacteria can live almost indefinitely in the 

 sea. A reconciliation of the divergent views requires that several factors 

 which influence the survival of bacteria in sea water be taken into consid- 

 eration. Artificial, synthetic, diluted, or autoclaved sea water, which has 

 been used for many of the experiments, does not necessarily simulate 

 natural sea water, and the biological properties of the latter may vary 

 greatly. 



In his studies on the factors which influence the survival of pathogenic 

 bacteria, de Giaxa (1889) observed that enteric bacteria perish very soon 

 in the sea. He found more than 100,000 bacteria per ml. of sea water 

 50 meters from a sewage outfall in the Gulf of Naples, 26,000 at a distance 

 of 350 meters, and fewer than 100 per ml. 3000 meters from the sewage 

 outfall. Controlled experiments showed that Bacillus anthracis and 

 Vibrio comma were unable to compete with saprophytes in polluted sea 

 water. The typhoid bacillus and pathogenic species of Staphylococcus . 

 were even less resistant. Vibrio comma lived for several days in heat- 

 sterilized sea water, but in untreated sea water it soon disappeared. The 

 period of survival was a function of the organic content and the bacterial 

 population of the water. In grossly polluted water these organisms sur- 

 vived for less than 24 hours. 



Experiments of various authors summarized by Frankland and 

 Frankland (1894) show that, in general, human pathogens do not survive 

 as long in sea water as in fresh water, although it is related that Vibrio 

 comma was observed by Nicati and Rietsch to remain viable in sterilized 

 sea water for as long as 81 days. 



According to Soper (1909), the virulence of Ebcrthella typhosa is not 

 reduced by sea water in two or three weeks. The persistence of Eb. 

 typhosa in refrigerated oysters for 49 days is reported by Krumwiede et al. 

 (1926), who believed that a few typhoid bacilli may live for several 

 months. Repeatedly washing the oysters with fresh sea water materially 

 reduced the number of surviving typhoid bacilli. The occurrence of para- 

 typhoid bacilli and other pathogens in sea water is discussed on page 191. 



