Quantification and characterization of Salmonella spp. isolates in sewage sludge with potential usage in agriculture.
BACKGROUND
This study aims to scrutinize Salmonella spp. and its serotypes in sewage sludge samples from wastewater treatment plants, and assesses the presence of virulence genes and antibiotics resistant to the profile. Samples (n = 54) were collected and analyzed in accordance with the EPA Method 1682/2006. For positive serological reaction, 40 strains were selected for PCR analyses and detection of spvC, invA and sseL virulence genes, plasmid presence and resistance to antibiotics.


RESULTS
Salmonella spp. was detected in 38.9% of the samples collected (<0.006473 to 12.19 MPN/gTS). The most prevalent serotype was Salmonella Infantis. All Salmonella spp. (n = 35) presented at least one of the three virulence genes mentioned above and 40% harboured plasmids. Salmonella Typhimurium strains were isolated harbouring at least one of the following virulence genes: spvC, invA or sseL. Four Salmonella spp. isolates were resistant to tetracycline; three were resistant to trimethoprim-sulfamethoxazole, and one isolate was resistant to ciprofloxacin. Two Salmonella spp. strains presented multi resistance to antimicrobial agents.


CONCLUSIONS
The results obtained demonstrated that Salmonella spp. have been found in sewage sludge, thus it is essential to set measures to mitigate human health risks when it is intended to be applied on agricultural soils.
Instituto Federal de Educação, Ciência e Tecnologia de São Paulo - Brasil, Rua Pedro Vicente 625, 01109-010, São Paulo, Brazil. fkjuniormeister@gmail.com.|School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. fkjuniormeister@gmail.com.
Flávio
F
Krzyzanowski
Instituto Federal de Educação, Ciência e Tecnologia de São Paulo - Brasil, Rua Pedro Vicente 625, 01109-010, São Paulo, Brazil. lincohn.zappelini@gmail.com.|School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. lincohn.zappelini@gmail.com.
Lincohn
L
Zappelini
School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. martone@usp.br.
Solange
S
Martone-Rocha
School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. milenadropa@usp.br.
Milena
M
Dropa
School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. mhmatte@usp.br.
Maria Helena
MH
Matté
School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. fla_nacache@hotmail.com.
Flávia
F
Nacache
School of Public Health of University of São Paulo-Brazil, Av. Dr Arnaldo 715, 1°andar, 01246-904, São Paulo, Brasil. razzolini@usp.br.
Maria Tereza Pepe
MT
Razzolini
D000383:Agriculture / Q000379:methods; D024881:Drug Resistance, Bacterial; D006801:Humans; D010957:Plasmids / Q000032:analysis; D012475:Salmonella / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D012703:Serotyping; D012722:Sewage / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics; D018508:Water Purification / Q000379:methods
D012722:Sewage; D037521:Virulence Factors