Novel method for studying the public health significance of macroinvertebrates occurring in potable water

Abstract

An experimental procedure was developed to study the association of selected bacteria and macroinvertebrates and their response to free available chlorine disinfection. The organisms selected for study were Escherichia coli (LacZ545), Enterobacter cloacae (ATCC 23355), and the amphipod Hyalella azteca. E. coli was shown to bind tightly (1.6 x 104 CFU per amphipod) to this macroinvertebrate and to resist repeated attempts to wash it off. E. cloacae was shown to bind much less tightly (1.4 x 103 CFU per amphipod) to H. azteca and was less resistant to removal by washing. The extent of association is a function of macroinvertebrate size (surface area), but the procedure produces repeatable results usable for controlled experimentation. This method, together with the dual bacterial identification criteria (morphology and antibiotic resistance), was used to study the response of unassociated and associated E. coli and E. cloacae to disinfection with free available chlorine at 1.0 mg/liter. Unassociated E. coli populations decreased to less than 1% of their zero time controls within 1 min of contact time, whereas more than 2% of the associated E. coli populations remained viable after 60 min of contact at 1.0 mg of free available chlorine per liter. Unassociated E. cloacae populations decreased to less than 1% of their zero time controls within 1 min of contact time, whereas ca. 15% of the associated E. cloacae populations remained viable after 60 min of contact at 1.0 mg of free available chlorine per liter. With minor modifications this method can be used to study essentially any combination of bacterium and macroinvertebrate and to thereby ascertain whether a macroinvertebrate can serve to breach the chlorine disinfection barrier, protect potential bacterial pathogens from disinfection, and possibly allow for subsequent pathogen multiplication within a potable water distribution system. One persistent problem associated with current drinking water resources is the infestation of both filtered and unfiltered water supplies and distribution systems by representatives of several taxonomic groups of meioand macroinvertebrates. These groups include Crustacea, Nematoda, Platyhelminthes, and Insecta. Their presence in potable water distribution systems is also expected, but it should not be tolerated. Macroinvertebrates can be the cause of tastes, odors, water discoloration, filter clogging, high turbidity, and political embarrassment. MacKenthun and Keup (16) stated that none of these organisms found in surface waters used for domestic purposes were injurious to health. No reference was cited to substantiate their conclusions. Haney (11) reported that macroinvertebrates (nematodes, in this case) can pose a threat to the public health, particularly if they are exposed to potential pathogens. In their concise

Inactivation of biofilm bacteria

“…Research has shown that increased resistance to disinfection results from attachment or association of microorganisms to various surfaces, including macroinvertebrates (Crustacea, Nematoda, Platyhelminthes, and Insecta) (31,53), turbidity particles (19-22, 27, 46), algae (51), carbon fines (7, 28), and even glass microscope slides (43), provides increased resistance to disinfection. Ridgway and Olson (46) showed that the majority of viable bacteria in chlorinated drinking water were attached to particles.…”

Factors promoting survival of bacteria in chlorinated water supplies

“…Available research has shown that increased resistance to disinfection may result from the attachment of microorganisms to or the association of microorganisms with various surfaces, including macroinvertebrates (Crustacea, Nematoda, Platyhelminthes, and Insecta) (26,36), turbidity particles (17-19, 23, 31), algae (34), carbon fines (7,24), and even glass microscope slides (29). Ridgway and Olson (31) have shown that the majority of viable bacteria in chlorinated drinking water are attached to particles.…”

Identification and phylogeny of eukaryotic 18S rDNA phylotypes detected in chlorinated finished drinking water samples from three Parisian surface water treatment plants

“…Moreover, many bacteria can survive and multiply within the intracellular environment of eukaryotic cells, an ecosystem that provides protection against hostile environmental conditions (e.g. disinfectants) as well as nutrients for growth (Levy et al. 1984; Barbaree et al.…”