Application of phage typing and pulsed-field gel electrophoresis to analyse Salmonella enterica isolates from a suspected outbreak in Lagos, Nigeria.
BACKGROUND
Inadequate potable water supply and poor sanitation predispose to food- and water-borne diseases associated with Salmonella enterica serovars in developing countries. In this study the possible source of an unprecedented upsurge of Salmonella-associated community gastroenteritis was traced using both phage-typing and pulsed-field gel electrophoresis (PFGE).


METHODS
Nineteen Salmonella Typhimurium (three sporadic isolates included) and 13 Salmonella Enteritidis isolates from clinical, animal, and environmental samples were subjected to antimicrobial susceptibility testing, phage-typing, and PFGE analysis using standard procedures.


RESULTS
Eleven (68.8%) of the 16 outbreak-related multidrug resistant S. Typhimurium belonged to DT 71 phage type with cluster PFGE type X3, representing the most prevalent strain identified among human, animal, and environmental isolates. The remaining five (31.2%) outbreak-related strains  reacted but did not conform with clear phage types (RDNC) with cluster PFGE types X1 and X2 (96.8% similarity). Sporadic strains were untypable and belonged to X4 PFGE type. However, the evaluated S. Enteritidis strains that were multidrug resistant without a definite phage type belonged to PFGE cluster type X1e and were identified among the water and human strains. None of the Typhimurium and Enteritdis isolates was resistant to the fluoroquinolone antibiotics that were evaluated.


CONCLUSIONS
This study emphasizes the epidemiological usefulness of PFGE typing in the detection of emerging strains of multipledrug resistant Salmonella, particularly S. Typhimurium DT71, that pose serious health implications in our environment. The study provides epidemiological links between environmental reservoirs and human infection in this community.
Department of Microbiology, Lagos State University, Ojo, PMB 1087, Apapa, Lagos, Nigeria. akinyemiko@yahoo.com
Kabiru Olusegun
KO
Akinyemi
Werner
W
Philipp
Wolfgang
W
Beyer
Reinhard
R
Böhm
D000818:Animals; D000900:Anti-Bacterial Agents; D001434:Bacteriophage Typing; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004783:Environmental Microbiology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D009549:Nigeria / Q000453:epidemiology; D012480:Salmonella Infections / Q000453:epidemiology* / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012477:Salmonella enteritidis / Q000145:classification* / Q000302:isolation & purification; D012486:Salmonella typhimurium / Q000145:classification* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents