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To determine the prevalence of Shiga toxin (Stx)-producing Escherichia coli (STEC) in slaughter animals in Dhaka, Bangladesh, we collected rectal contents immediately after animals were slaughtered. Of the samples collected from buffalo (n ‫؍‬ 174), cows (n ‫؍‬ 139), and goats (n ‫؍‬ 110), 82.2%, 72.7%, and 11.8% tested positive for stx 1 and/or stx 2 , respectively. STEC could be isolated from 37.9%, 20.1%, and 10.0% of the buffalo, cows, and goats, respectively. STEC O157 samples were isolated from 14.4% of the buffalo, 7.2% of the cows, and 9.1% of the goats. More than 93% (n ‫؍‬ 42) of the STEC O157 isolates were positive for the stx 2 , eae, katP, etpD, and enterohemorrhagic E. coli hly (hly EHEC ) virulence genes. STEC O157 isolates were characterized by seven recognized phage types, of which types 14 (24.4%) and 31 (24.4%) were predominant. Subtyping of the 45 STEC O157 isolates by pulsed-field gel electrophoresis showed 37 distinct restriction patterns, suggesting a heterogeneous clonal diversity. In addition to STEC O157, 71 STEC non-O157 strains were isolated from 60 stx-positive samples from 23.6% of the buffalo, 12.9% of the cows, and 0.9% of the goats. The STEC non-O157 isolates belonged to 36 different O groups and 52 O:H serotypes. Unlike STEC O157, most of the STEC non-O157 isolates (78.9%) were positive for stx 1 . Only 7.0% (n ‫؍‬ 5) of the isolates were positive for hly EHEC , and none was positive for eae, katP, and etpD. None of the isolates was positive for the iha, toxB, and efa1 putative adhesion genes. However, 35.2% (n ‫؍‬ 25), 11.3% (n ‫؍‬ 8), 12.7% (n ‫؍‬ 9), and 12.7% (n ‫؍‬ 9) of the isolates were positive for the lpf O113 , saa, lpfA O157/01-141 , and lpfA O157/OI-154 genes, respectively. The results of this study provide the first evidence that slaughtered animals like buffalo, cows, and goats in Bangladesh are reservoirs for STEC, including the potentially virulent STEC strain O157.

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c Environmental surfaces contaminated with pathogens can be sources of indirect transmission, and cleaning and disinfection are common interventions focused on reducing contamination levels. We determined the efficacy of cleaning and disinfection procedures for reducing contamination by noroviruses, rotavirus, poliovirus, parechovirus, adenovirus, influenza virus, Staphylococcus aureus, and Salmonella enterica from artificially contaminated stainless steel surfaces. After a single wipe with water, liquid soap, or 250-ppm free chlorine solution, the numbers of infective viruses and bacteria were reduced by 1 log 10 for poliovirus and close to 4 log 10 for influenza virus. There was no significant difference in residual contamination levels after wiping with water, liquid soap, or 250-ppm chlorine solution. When a single wipe with liquid soap was followed by a second wipe using 250-or 1,000-ppm chlorine, an extra 1-to 3-log 10 reduction was achieved, and except for rotavirus and norovirus genogroup I, no significant additional effect of 1,000 ppm compared to 250 ppm was found. A reduced correlation between reduction in PCR units (PCRU) and reduction in infectious particles suggests that at least part of the reduction achieved in the second step is due to inactivation instead of removal alone. We used data on infectious doses and transfer efficiencies to estimate a target level to which the residual contamination should be reduced and found that a single wipe with liquid soap followed by a wipe with 250-ppm free chlorine solution was sufficient to reduce the residual contamination to below the target level for most of the pathogens tested.

The need for protozoa for the proliferation of Legionella pneumophila in aquatic habitats is still not fully understood and is even questioned by some investigators. This study shows the in vivo growth of L. pneumophila in protozoa in aquatic biofilms developing at high concentrations on plasticized polyvinyl chloride in a batch system with autoclaved tap water. The inoculum, a mixed microbial community including indigenous L. pneumophila originating from a tap water system, was added in an unfiltered as well as filtered (cellulose nitrate, 3.0-m pore size) state. Both the attached and suspended biomasses were examined for their total amounts of ATP, for culturable L. pneumophila, and for their concentrations of protozoa. L. pneumophila grew to high numbers (6.3 log CFU/cm 2 ) only in flasks with an unfiltered inoculum. Filtration obviously removed the growth-supporting factor, but it did not affect biofilm formation, as determined by measuring ATP. Cultivation, direct counting, and 18S ribosomal DNA-targeted PCR with subsequent sequencing revealed the presence of Hartmannella vermiformis in all flasks in which L. pneumophila multiplied and also when cycloheximide had been added. Fluorescent in situ hybridization clearly demonstrated the intracellular growth of L. pneumophila in trophozoites of H. vermiformis, with 25.9% ؎ 10.5% of the trophozoites containing L. pneumophila on day 10 and >90% containing L. pneumophila on day 14. Calculations confirmed that intracellular growth was most likely the only way for L. pneumophila to proliferate within the biofilm. Higher biofilm concentrations, measured as amounts of ATP, gave higher L. pneumophila concentrations, and therefore the growth of L. pneumophila within engineered water systems can be limited by controlling biofilm formation.Legionella pneumophila is widespread in natural freshwater environments, despite its fastidious nature (16). The bacterium has also frequently been observed in engineered water systems such as warm water distributing systems, cooling towers, humidifiers, and fountains (25,43,50). The multiplication of the organism in water systems poses a potential human health risk when aerosolization can occur (12).Legionellae grow in vitro only in complex media with supplements of cysteine and iron salts (11). For their multiplication in vivo, other microorganisms are required, but different species of heterotrophic bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Flavobacterium sp.) alone do not support the growth of L. pneumophila (31,45). In vitro studies using cocultures have repeatedly demonstrated the intracellular multiplication of L. pneumophila in amoebae (Acanthamoeba, Echinamoeba, Hartmannella, Naegleria, Vahlkampfia, and Dictyostelium) and in a ciliated protozoon (Tetrahymena pyriformis) (12,15,21,39). Amoebae have been observed in water systems associated with Legionnaires' disease (5, 7), and L. pneumophila can recolonize water distributing systems within a few weeks after disinfection (26,27). Batch experiments with tap wate...

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