Epidemiologic studies were conducted on 31 cases of Salmonella group E infection detected in 2000 through a laboratory-based pathogen surveillance in Gangwon Province, Korea. Data were collected on the environmental exposures and the patients' foods, including the brand (s) of milk consumed before the onset of diarrhea. The patients' medical records were also reviewed. All of the patients were infants under 10 months of age except one 7-year old child. Surprisingly, all of the infants were fed with infant formulas from Company A, although two infants were fed with infant formulas from both Company A and Company B. Antimicrobial susceptibility test and pulsed-field gel electrophoresis (PFGE) were performed in 25 out of 31 isolates from the patients and in 1 isolate from an opened packet of infant formula collected from the home of an infected infant. All of the 26 isolates were Salmonella enterica serovar London. They showed a single PFGE pattern, and all of the isolates were susceptible to the 18 antibiotics tested. The causative agent of the salmonella outbreaks in the Gangwon Province and its surrounding areas was Salmonella London, and the highly likely source of the infection was infant formula from Company A.
Child ; DNA, Bacterial/analysis ; *Disease Outbreaks ; Female ; *Food Contamination ; Human ; Infant ; *Infant Formula ; Infant, Newborn ; Korea/epidemiology ; Male ; Salmonella Infections/*epidemiology/*transmission ; Salmonella enterica/classification/genetics/*isolation & purification

OBJECTIVETo study the characteristics of the strains of Salmonella enterica (S. enterica) serovar Senftenberg lacking Salmonella pathogenicity island 1 (SPI-1).

METHODSA total of 10 strains of S. enterica serovar Senftenberg were isolated from 10 cases of diarrhea patients. Pulsed field gel electrophoresis (PFGE), PCR, sequencing techniques and cell invasion test were adapted to study the molecular types and invasiveness of the genes and cells; and made a comparison between the 10 strains and the strains (C02013) isolated in Shenzhen in 2002.

RESULTSThe 10 Senftenberg isolated (S09007-S09012, S09014-S09017) in Shanghai showed three PFGE patterns, which were significantly different from the strains isolated in Shenzhen. PCR-amplified results indicated the invasion gene (invA), secreted effector protein gene (sipA) and gene fragments as fhlA-hilA, hilA-spaP and spaP-invH in the 10 strains of SPI-1 were all negative. The sequencing results revealed that the 10 strains isolated in Shanghai lacked most parts of SPI-1 genes, as fragments from orgA to invH and parts of orgA gene itself; however, compared with strains isolated in Shenzhen, the sprB-orgC gene existed. The missing parts of genes were replaced by a simple insertion sequence (IS) of 1000 bp in the strains isolated both in Shenzhen in 2002 and in Shanghai in 2006. The invasiveness rates of the 10 strains (S09007-S09012, S09014-S09017) towards Hela cells were (0.0053 ± 0.0024)%, (0.0046 ± 0.0006)%, (0.0047 ± 0.0003)%, (0.0064 ± 0.0012)%, (0.0065 ± 0.0011)%, (0.0070 ± 0.0020)%, (0.0115 ± 0.0030)%, (0.0099 ± 0.0039)%, (0.0180 ± 0.0135)% and (0.0031 ± 0.0012)%, respectively; which were all significantly lower than the rate of invA-positive control strain STM1344 ((5.0800 ± 0.6333)%); lower or close to the rate of invA-lacked artificial-mutated strain STMinvA-((0.0193 ± 0.0045)%).

CONCLUSIONSPI-1 genes are not essential for the diarrhea caused by S. enterica serovar Senftenberg.

Adult ; Aged ; Bacterial Typing Techniques ; Diarrhea ; microbiology ; Feces ; microbiology ; Female ; Genes, Bacterial ; Genomic Islands ; HeLa Cells ; Humans ; Male ; Middle Aged ; Salmonella enterica ; genetics ; isolation & purification ; pathogenicity

A total of 74 isolates of Salmonella enterica serovar London were collected through the Laboratory-Based Diarrheal Diseases Surveillance in 2000-2001. In order to characterize the isolates and investigate the source of the epidemic, we performed antimicrobial susceptibility tests and XbaI Pulsed-field gel electrophoresis (PFGE) of 44 Salmonella London isolates. Forty isolates were from feces of infants and four isolates were from adults aged 30, 52, 54, and 59 yr. Two subtypes were identified: a tetracycline-susceptible A 0 PFGE pattern and a tetracyclineresistant A 1 PFGE pattern. Interestingly, the isolates from all infants and one 30-yr-old adult were A 0 PFGE pattern and tetracycline-susceptible. Furthermore, the A 0 PFGE pattern strain was approximately 2 times more virulent than the A 1 PFGE pattern strain, according to the results of in vitro invasion assay using J774A.1 macrophage-like cells. These results indicate that the active surveillance with molecular epidemiological tools would be valuable for promptly finding new epidemic strains. Our results also suggested that the virulent Salmonella London strain might infect the infants through a common contaminated source.
Adult ; Anti-Bacterial Agents/therapeutic use ; DNA, Bacterial/analysis ; Diarrhea/epidemiology/microbiology ; Disease Outbreaks ; Enteritis/*epidemiology/microbiology ; Feces/microbiology ; Human ; In Vitro ; Infant ; Microbial Sensitivity Tests ; Middle Aged ; Reactive Oxygen Species/pharmacology ; Salmonella Infections/drug therapy/*epidemiology/microbiology ; Salmonella enterica/genetics/*isolation & purification/pathogenicity ; Virulence