Bok Kwon Lee

Surveillance of Stool Samples for the Presence of Enterobacter sakazakii among Korean People

Purpose Enterobacter sakazakii (E. sakazakii) infections are an important cause of life-threatening meningitis, septicemia, and necrotizing enterocolitis in infants. Dried infant formula milk is an important vehicle for E. sakazakii infection. E. sakazakii was isolated in Korea from dried infant formula milk. Although E. sakazakii infection of infants may occur in Korea, its prevalence has not yet been documented. Therefore, we determined the prevalence of E. sakazakii and documented symptoms. Materials and Methods Between March and October 2006, 1,146 stool samples were collected from patients at Uijeongbu St. Marys Hospital. Each fecal swab was dissolved in 10 mL of buffered peptone solution, and enriched culture was streaked onto Druggan-Forsythe-Iversen (DFI) agar. Presumptive E. sakazakii colonies that exhibited a blue-green color during culture on DFI medium were selected. The identity of colonies that developed yellow pigment during culture on TSA was determined using the Vitek system and PCR. Results We isolated 4 E. sakazakii strains whose 16S rRNA sequence alignments had a similarity of 99% with those of 3 E. sakazakii ATCC strains. Conclusion This is the first report on isolation of E. sakazakii from stool samples and to document the symptoms of Korean patients.

A Korean Nationwide Surveillance Study for Non-Typhoidal Salmonella Isolated in Humans and Food Animals from 2006 to 2008: Extended-Spectrum β-Lactamase, Plasmid-Mediated AmpC β-Lactamase, and Plasmid-Mediated Quinolone Resistance qnr Genes

Background: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum β-lactamase (ESBL), plasmid-mediated AmpC β-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study. Methods: National Institute of Health and National Veterinary Research and Quarantine Service collected NTS strains from 219 clinical and 293 non-clinical specimens from 2006 to 2008. The antimicrobial susceptibilities were determined using the Clinical and Laboratory Standards Institute disk diffusion test. ESBL, PABL, and qnr genotyping were performed using PCR and nucleotide sequencing. Pulsed-field gel electrophoresis was used for the molecular epidemiologic study. Results: The resistance to ampicillin in clinical and non-clinical NTS was 49% and 18 to 47%, respectively. The resistance rates to trimethoprim-sulfamethoxazole in clinical and non-clinical NTS were 8% and 0 to 41%, respectively. The rates to extendedspectrum cephalosporin were 0 to 1%. One CTX-M15-producing isolate and four CMY-2-producing isolates were detected. Notably, PFGE analysis showed four isolates carrying blaCMY-2, including one non-clinical strain had high clonality. Although the rate of ciprofloxacin resistance was very low, two qnrS1-carrying NTS strains were detected in non-clinical specimens. Conclusion: The resistance rates to ampicillin in both clinical and non-clinical NTS were high, while those to trimethoprim-sulfamethoxazole varied depending on the specimen. NTS strains harboring CTX-M-15type ESBL or CMY-2-type PABL were detected even though the resistance rates to cephalosporins were very low. Four NTS strains carrying the blaCMY-2gene implied zoonotic infection. Continuous effort to minimize transfer of resistance genes in NTS is necessary. (Korean J Clin Microbiol 2012;15:14-20)