Abstract
BackgroundMulti-drug resistant forms of Pseudomonas aeruginosa (MDRPA) are a major source of nosocomial infections and when discharged into streams and rivers from hospital wastewater treatment plants (HWWTP) they are known to be able to persist for extended periods. In the city of Manaus (Western Brazilian Amazon), the effluent of three HWWTPs feed into the urban Mindu stream which crosses the city from its rainforest source before draining into the Rio Negro. The stream is routinely used by Manaus residents for bathing and cleaning (of clothes as well as domestic utensils) and, during periods of flooding, can contaminate wells used for drinking water.Results16S rRNA metagenomic sequence analysis of 293 cloned PCR fragments, detected an abundance of Pseudomonas aeruginosa (P. aeruginosa) at the stream’s Rio Negro drainage site, but failed to detect it at the stream’s source. An array of antimicrobial resistance profiles and resistance to all 14 tested antimicrobials was detected among P. aeruginosa cultures prepared from wastewater samples taken from water entering and being discharged from a Manaus HWWTP. Just one P. aeruginosa antimicrobial resistance profile, however, was detected from cultures made from Mindu stream isolates. Comparisons made between P. aeruginosa isolates’ genomic DNA restriction enzyme digest fingerprints, failed to determine if any of the P. aeruginosa found in the Mindu stream were of HWWTP origin, but suggested that Mindu stream P. aeruginosa are from diverse origins. Culturing experiments also showed that P. aeruginosa biofilm formation and the extent of biofilm formation produced were both significantly higher in multi drug resistant forms of P. aeruginosa.ConclusionsOur results show that a diverse range of MDRPA are being discharged in an urban stream from a HWWTP in Manaus and that P. aeruginosa strains with ampicillin and amikacin can persist well within it.
Highlights
Multi-drug resistant forms of Pseudomonas aeruginosa (MDRPA) are a major source of nosocomial infections and when discharged into streams and rivers from hospital wastewater treatment plants (HWWTP) they are known to be able to persist for extended periods
Our results suggest that HWWTP are polluting the Mindu stream in Manaus with antibiotic resistant P. aeruginosa and may be putting residents that live in contact with these contaminated waters at risk to nosocomial infections
Bacterial diversity at the Mindu streams source and drainage sites As a preliminary and general assessment of the bacterial ecology of the Mindu stream, two bacterial 16S rRNA gene metagenomic libraries were constructed from bacterial concentrates made from the surface water of: (1) a site close to the stream’s source and (2) a site close to where the stream drains into the Rio Negro
Summary
Multi-drug resistant forms of Pseudomonas aeruginosa (MDRPA) are a major source of nosocomial infections and when discharged into streams and rivers from hospital wastewater treatment plants (HWWTP) they are known to be able to persist for extended periods. Previous studies have identified MDRPA as the primary pathogen found in the discharge of HWWTP, suggesting that the bacterium could have an important role in the spread of antimicrobial resistance, which is a global and increasing healthcare problem [23] Consistent with this notion, studies investigating the distribution and persistence of P. aeruginosa have shown that the bacterium is widely distributed in the environment and that P. aeruginosa, including MDRPA, discharged from HWWTP can persist in the environment over extended periods [24]. The discharge of MDRPA in hospital effluents is increasingly being seen as having an important role in the global spread of antimicrobial resistance and is an important public health concern [24, 25]
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