Powder infant formula milk contaminated with Enterobacter sakazakii
Kenji Oonaka1, Katsunori Furuhata, Motonobu Hara
1Laboratory of Microbiology, School of Life and Environmental Science, Azabu University, Sagamihara, Kanagawa, Japan. oonaka@azabu-u.ac.jp
Abstract:
To clarify the route and source of Enterobacter sakazakii infection in a basic study, we analyzed powder infant formula milk (PIF), which may be an important source of infantile infection, regarding contamination with Enterobacteriaceae including this type of bacteria, and conducted drug sensitivity tests with various antimicrobial agents. Enterobacteriaceae was isolated 36 (24.2%) of 149 PIF samples. These comprised of 12 (19.7%) of 61 domestically produced samples and 24 (27.3%) of 88 imported samples. E. sakazakii was isolated in 9 (6.6%) of the 149 PIF samples. These comprised 4 (6.6%) of 61 domestically produced samples and 5 (5.7%) of 88 imported samples. In 8 of the 9 samples in which E. sakazakii was isolated, the bacterial levels were estimated to be 0.36 MPN/100 g. However, one imported sample showed a bacterial level of 0.91 MPN/100 g. In the drug sensitivity tests of E. sakazakii isolated from PIF, we compared the MIC(90) values. E. sakazakii was highly sensitive to 9 agents: cefotaxime, ceftriaxone, cefoperazone, ceftazidime, cefpirome, cefozopran, gentamicin, meropenem, and ciprofloxacin, and moderately sensitive to 5 agents: piperacillin, erythromycin, minocycline, chloramphenicol, and rifampicin. However, it was resistant to 2 agents, ampicillin and lincomycin.
Insights
Powder infant formula milk (PIF) can be a source of Enterobacter sakazakii infection. This study found E. sakazakii in 6.6% of PIF samples and identified effective antimicrobial agents for treatment.
Area of Science:
- Microbiology
- Food Safety
- Infectious Diseases
Background:
- Enterobacter sakazakii is a pathogen that can cause serious infections in infants.
- Powder infant formula milk (PIF) has been implicated as a potential source of E. sakazakii transmission.
- Understanding the prevalence and antimicrobial susceptibility of E. sakazakii in PIF is crucial for public health.
Purpose of the Study:
- To investigate the contamination of PIF with Enterobacteriaceae, including E. sakazakii.
- To determine the prevalence of E. sakazakii in both domestically produced and imported PIF samples.
- To assess the antimicrobial susceptibility profile of E. sakazakii isolated from PIF.
Main Methods:
- Analysis of 149 PIF samples for the presence of Enterobacteriaceae.
- Isolation and identification of E. sakazakii from positive samples.
- Determination of bacterial levels using most probable number (MPN) method.
- Antimicrobial susceptibility testing using minimum inhibitory concentration (MIC90) values.
Main Results:
- Enterobacteriaceae were detected in 24.2% of PIF samples (36/149).
- E. sakazakii was isolated from 6.6% of PIF samples (9/149), with similar prevalence in domestic (6.6%) and imported (5.7%) samples.
- E. sakazakii showed high sensitivity to cefotaxime, ceftriaxone, gentamicin, meropenem, and ciprofloxacin, moderate sensitivity to erythromycin and chloramphenicol, and resistance to ampicillin and lincomycin.
Conclusions:
- PIF is a potential reservoir for E. sakazakii contamination.
- Effective antimicrobial agents for treating E. sakazakii infections include cephalosporins, aminoglycosides, carbapenems, and fluoroquinolones.
- Monitoring PIF for E. sakazakii and understanding antimicrobial resistance patterns are vital for infant safety.
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