Background. Hospital effluents are considered an important source of both microorganisms and chemical substances (e. g. drug residues, disinfectants) that might impact the environment, often requiring pre-treatment before they can be released to public wastewater treatment plants. In order to investigate how wastewater treatment could affect the microbial biodiversity and its associated antimicrobial resistance, we performed a microbiological and molecular analysis of samples collected at the inlet and outlet of our local wastewater treatment plant. Methods. Samples were collected at the University Hospital of Siena wastewater treatment plant during Feb and Oct 2012. Microbial aerobic count was determined on Nutrient Agar and McConkey Agar plates at 30 or 37 °C. Identification of microorganisms was carried out using a Vitek MS. Antimicrobial susceptibility testing was performed as recommended by CLSI. Determinants of antimicrobial resistance were analyzed using either phenotypic tests or molecular methods. Results. A comparative analysis of pre- and post-treatment samples (total bacterial counts in the various samples ranged 5×104 – 2×106 CFU/ml) revealed important differences in both microbial biodiversity and its associated antimicrobial resistance: (a) the percentage of Gram-negative (GN) bacteria in post-treatment samples was significantly lower than that found in pre-treatment samples (5 vs 40% total, respectively) and (b) a higher proportion of antibiotic-resistant GN isolates was found in post-treatment samples, with 59% isolates showing ceftazidime resistance (vs 6% in pre-treatment samples). Approx. 10% of CAZ-resistant GN isolates exhibited resistance to carbapenems, fluoroquinolones and aminoglycosides and belonged to genera Citrobacter, Klebsiella and Shewanella. Molecular analysis revealed the presence of KPC-producing Klebsiella pneumoniae and VIM-2-producing Citrobacter spp. isolates (including C. braaki in which such determinant was not previously reported). Conclusions. The hospital wastewater samples contained both environmental and clinically-relevant bacterial species. Despite post-treatment samples showed a lower prevalence of GN species, a higher of rate antibiotic resistance was found.

TAPPA BROCCI, N., DE LUCA, F., Lenzi, D., Basagni, C., Rossolini, G.M., & Docquier, J.D. (2013). Microbiological analysis of hospital wastewaters: impact of water treatment on microbial biodiversity and antimicrobial resistance.. In 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy Abstract Book. Washington : ASM Press.

Microbiological analysis of hospital wastewaters: impact of water treatment on microbial biodiversity and antimicrobial resistance.

TAPPA BROCCI, NICCOLO';DE LUCA, FILOMENA;ROSSOLINI, GIAN MARIA;DOCQUIER, JEAN DENIS
2013

Abstract

Background. Hospital effluents are considered an important source of both microorganisms and chemical substances (e. g. drug residues, disinfectants) that might impact the environment, often requiring pre-treatment before they can be released to public wastewater treatment plants. In order to investigate how wastewater treatment could affect the microbial biodiversity and its associated antimicrobial resistance, we performed a microbiological and molecular analysis of samples collected at the inlet and outlet of our local wastewater treatment plant. Methods. Samples were collected at the University Hospital of Siena wastewater treatment plant during Feb and Oct 2012. Microbial aerobic count was determined on Nutrient Agar and McConkey Agar plates at 30 or 37 °C. Identification of microorganisms was carried out using a Vitek MS. Antimicrobial susceptibility testing was performed as recommended by CLSI. Determinants of antimicrobial resistance were analyzed using either phenotypic tests or molecular methods. Results. A comparative analysis of pre- and post-treatment samples (total bacterial counts in the various samples ranged 5×104 – 2×106 CFU/ml) revealed important differences in both microbial biodiversity and its associated antimicrobial resistance: (a) the percentage of Gram-negative (GN) bacteria in post-treatment samples was significantly lower than that found in pre-treatment samples (5 vs 40% total, respectively) and (b) a higher proportion of antibiotic-resistant GN isolates was found in post-treatment samples, with 59% isolates showing ceftazidime resistance (vs 6% in pre-treatment samples). Approx. 10% of CAZ-resistant GN isolates exhibited resistance to carbapenems, fluoroquinolones and aminoglycosides and belonged to genera Citrobacter, Klebsiella and Shewanella. Molecular analysis revealed the presence of KPC-producing Klebsiella pneumoniae and VIM-2-producing Citrobacter spp. isolates (including C. braaki in which such determinant was not previously reported). Conclusions. The hospital wastewater samples contained both environmental and clinically-relevant bacterial species. Despite post-treatment samples showed a lower prevalence of GN species, a higher of rate antibiotic resistance was found.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11365/975438