Coliform is present in the digestive tracts and faeces of animals and in soil and and plant material.
A statement released by Hong Kong’s Department of Health on Monday night said 39 samples had been collected and analysed, and played down the possibility of danger to passengers or crew members who had been on the planes affected.
It said “E. Coli was not detected in any of the water samples and hence there is no immediate public health risk to travellers and crew members.”
Nevertheless, a spokesman for the Department of Health said the presence of bacteria in two samples taken from tankers “suggested a suboptimal standard of water quality, which may be likely contributable by the hygienic condition of the water tankers.”
It continued: “Coliform bacteria are not a single species of organism. They are a group of closely related, mostly harmless, bacteria which live in soil, water and the gut of animals. Coliform count is a hygienic indicator and a high level of coliform count generally indicates an unsanitary condition.”
The ground handling companies that operate the tankers will now “conduct thorough cleansing and disinfection” of the tankers before carrying out further tests, the Department of Health said.
The water tanks in all 14 Cathay aircraft affected have been cleaned and disinfected, the department added.
A letter is to be sent to all airlines informing them of the findings.