title: Prevalence of tetracycline resistance genes among multi-drug resistant bacteria from selected water distribution systems in southwestern Nigeria.
abstract: BACKGROUND
  Antibiotic resistance genes [ARGs] in aquatic systems have drawn increasing attention they could be transferred horizontally to pathogenic bacteria. Water treatment plants (WTPs) are intended to provide quality and widely available water to the local populace they serve. However, WTPs in developing countries may not be dependable for clean water and they could serve as points of dissemination for antibiotic resistant bacteria. Only a few studies have investigated the occurrence of ARGs among these bacteria including tetracycline resistance genes in water distribution systems in Nigeria.
  
  
  METHODS
  Multi-drug resistant (MDR) bacteria, including resistance to tetracycline, were isolated from treated and untreated water distribution systems in southwest Nigeria. MDR bacteria were resistant to >3 classes of antibiotics based on break-point assays. Isolates were characterized using partial 16S rDNA sequencing and PCR assays for six tetracycline-resistance genes. Plasmid conjugation was evaluated using E. coli strain DH5α as the recipient strain.
  
  
  RESULTS
  Out of the 105 bacteria, 85 (81 %) and 20 (19 %) were Gram- negative or Gram- positive, respectively. Twenty-nine isolates carried at least one of the targeted tetracycline resistance genes including strains of Aeromonas, Alcaligenes, Bacillus, Klebsiella, Leucobacter, Morganella, Proteus and a sequence matching a previously uncultured bacteria. Tet(A) was the most prevalent (16/29) followed by tet(E) (4/29) and tet30 (2/29). Tet(O) was not detected in any of the isolates. Tet(A) was mostly found with Alcaligenes strains (9/10) and a combination of more than one resistance gene was observed only amongst Alcaligenes strains [tet(A) + tet30 (2/10), tet(A) + tet(E) (3/10), tet(E) + tet(M) (1/10), tet(E) + tet30 (1/10)]. Tet(A) was transferred by conjugation for five Alcaligenes and two E. coli isolates.
  
  
  CONCLUSIONS
  This study found a high prevalence of plasmid-encoded tet(A) among Alcaligenes isolates, raising the possibility that this strain could shuttle resistance plasmids to pathogenic bacteria.
authors.affiliation: Department of Biological Sciences, Federal University Dutsin-Ma, Dutsin-Ma, Katsina State, Nigeria. timmyayus2002@yahoo.com.
authors.forename: Ayodele T
authors.initials: AT
authors.lastname: Adesoji
authors.affiliation: Department of Microbiology, University of Ibadan, Ibadan, Oyo State, Nigeria. aaogunjobi@hotmail.com.
authors.forename: Adeniyi A
authors.initials: AA
authors.lastname: Ogunjobi
authors.affiliation: Department of Veterinary Public Health and Preventive Medicine, University of Ibadan, Ibadan, Oyo State, Nigeria. olatoyevet@yahoo.com.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington State, USA. olatoyevet@yahoo.com.
authors.forename: Isaac O
authors.initials: IO
authors.lastname: Olatoye
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington State, USA. drcall@vetmed.wsu.edu.|Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, USA. drcall@vetmed.wsu.edu.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Call
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Douglas
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D005798:Genes, Bacterial; D005838:Genotype; D008826:Microbial Sensitivity Tests; D009549:Nigeria; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013752:Tetracycline / Q000494:pharmacology*; D014871:Water Microbiology; D018508:Water Purification
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D013752:Tetracycline