Conventional methods for cleaning and sanitizing commercial grouted ceramic tile floors involve applying aqueous solutions to floors with repeated wetting and wringing cycles using mops and two- or three-compartment buckets. In contrast, in the spray-and-vac method, fresh cleaning and sanitizing solution is applied to the floor with a spray gun and subsequently extracted by vacuum into a waste containerbuilt into the machine. For removing bacterial contamination, the data shows that the spray-and-vac machine is 60 times more effective in reducing bacterial contamination than the conventional method for typical commercial floors, such as those used for aseptic processing.

DIFFICULTIES IN CLEANING TILE AND GROUT
Removal of microbial contamination from ceramic tiles and especially grouting presents a serious cleaning problem because of two factors. Grouting is softer and more porous than tiling and the surface of grouting, and the “grout line” is most often lower than the surfaces of the tiles. Also, the construction of floors with small tiles — common in modern buildings — results in high ratios of grouting surface areas to tile surface areas. Thus, successful removal of microbial contamination of floors by cleaning operations dependscritically on removal of the contamination from grouting.

Numerous scientific methods are available to determine quantitatively surface cleanability and cleanliness. In practical situations, the quantitative cleaning and assay methods selected are based on the cleanliness level required, on the type of surface material and on the type of soil.1,2Although cleaning standards for ceramic tiles have been established (ASTM D5343, 2006), the standards specifically exclude application to the grouting between tiles.

Jointing grouts are usually made of cement, epoxy, a mixture of cement and epoxy, or of an elastic grout material, such as silicone, uretan, or acryl. Only a limited number of investigations have been published concerning the qualitative cleanability of ceramic or any other tile grout materials. In particular, the significance of the porosity and roughness of conventional grout lines is not well known with respect to their cleanability. Recently the cleanability of grout has been studied quantitatively.3This study compared the cleanabilities of cementitious grout, mineral polymer covered cementitious grout, and epoxy grout, and concluded that epoxy grout was the most easily cleaned of these grouts. This finding is expected, since epoxy was the hardest and the least porous material of the grout materials included.

With respect to removing bacteria from porous and rough surfaces, Holah and Thorpe4studied bacterial retention on various ceramic materials. They suggested that the greater the degree of surface irregularities, the greater the chance of bacterial retention after cleaning. The roughness of the surface also increased the area to which bacteria were able to fasten.

For determinations of microbial contamination on solid surfaces, including ceramics, recommended methods have been developed to allow quantitative determination of bacterial and viral removal (ASTM E2414-05; AOAC 961.02). Standard guidances for analyzing microbial contamination of grouting have not been developed.

In this article, we present quantitative data on removal of dried deposits and microbials from soiled tiles and bacterial removal from the grout line using protocols based on standard analytical microbiological practices for examining residual bacterial contamination on surfaces.

CLEANING METHODS AND CHEMICALS
A mild, multipurpose, pH neutral, cleaner that combines citrus d-limonene with hydrogen peroxide was used at a dilution of 2 oz/gal in tap water for cleaning tests using this agent.
A hospital grade broad spectrum, pH neutral disinfectant was used at a dilution of 2 oz/gal in tap water for cleaning tests using this agent.
Household Bleach was used at a concentration of 200 ppm.

Mop Cleaning Method
The following mop cleaning procedures were used throughout this investigation:

• Fresh tap water and a fresh, never-used, mop head was used for each cleaning application.
• The mops were thoroughly wetted and wrung out in a mop-bucket wringer resulting in a dampened mop.

The test area was then cleaned by making a first pass of the mop across the area and then making a second pass in the opposite direction. For each pass across the floor, a slight downward pressure was applied to the mop via the mop handle.