Dr. Keith Lampel From U.S. Food & Drug Administration (FDA) Addresses Standard Method Of Detection

Editor's Note:  We continue presentations from the international Cronobacter conference held earlier this year in Ireland.  In this segment, we hear from the USA's Dr. Keith Lampel from FDA.

Biography: Dr. Keith Lampel is director of the Division of Microbiology at the U.S. Food & Drug Administration (FDA). He joined the FDA as a research microbiologist in 1987 after five years as a senior staff fellow at the National Institutes of Health, National Institute of Neurological Disorders and Stroke.
Dr. Lampel received his PhD in Microbiology from the University of Miami and was a postdoctoral fellow at the State University of New York at Stony Brook.
At FDA today, he is responsible for developing bacteriological and molecular-based methods to isolate, detect, and subtype foodborne pathogens. Dr Lampel is also the Editor of FDA’s Bacteriological Analytical Manual and serves as the FDA’s expert on the detection and isolation of the foodborne bacterial pathogen Shigella.
Other professional activities include serving on several editorial boards; NIH and USDA study panels, and ad’hoc review panels for several journals and extramural grant programs. He also serves as an adjunct professor at the University of Maryland and Uniformed Services University of the Health Sciences, and is a member of several PhD dissertation committees.

Summary - Development of an FDA/AOAC standard method for detection of Cronobacter

Although the number of incidences of illnesses caused by the ingestion of the bacterial pathogen Cronobacter (Enterobacter sakazakii) has not been as dramatic as other foodborne pathogens, a need remains for a robust isolation method to recover this microbe from powdered infant formula (PIF).
The current method described on the FDA website was developed in response to one such incident. Although C. sakazakii was a rather novel pathogen in an unusual food matrix, a method was devised quickly and applied to PIF samples. Unfortunately, this method requires multiple steps and at least 3-4 days for complete analysis of PIF for isolation and confirmation of C. sakazakii from the formula sample.
The revised method, however, includes a bacteriological enrichment and isolation protocol as well as the integration of a PCR-based assay. As for the bacteriological application, plating follows one-step enrichment on chromogenic agar(s) for presumptive identification of C. sakazakii. Suspected colonies are confirmed by either biochemical analysis or a real-time PCR-based assay. Therefore, isolation and identification of E. sakazakii from PIF is markedly improved and can be accomplished in 24-28 hrs.

Dr. Lampel's POWERPOINT can be found here

Development of a CEN-ISO horizontal standard method

Editor's Note: Another of the presentations follows from last January's 1st International Conference on Cronobacter (Enterobacter Sakazakii) held at University College Dublin.  Dr. Han Joosten from the Nestle Research Center in Switzerland addresses the standard method for detection of Cronobacter.

Biography: Dr. Han Joosten is a Senior Scientist at the Nestle Research Center in Lausanne, Switzerland. At Nestle since 1996, he is responsible for providing scientific guidance on various research projects and early identification of emerging microbiological safety issues. He also provides advice to the business and quality management on analytical methods, hurdle technology, safety assessments and HACCP.
After finishing his studies at the University of Nijmegen in the Netherlands in 1983 Joosten worked five years at NIZO Food Research on the formation of biogenic amines in cheese, obtaining his PhD degree from the University of Wageningen on this subject.
From 1989 to 1991 he worked as a postdoc at the Autonomous University of Madrid on molecular characterization of African Swine Fever Virus. After this he headed the microbiological laboratory of Coberco Research in Deventer, the Netherlands and moved back to Spain in 1994 where he worked for two years at the National Instititute for Agricultural and Food Research (CIT-INIA) in Madrid on a bacteriocin-producing Enterococcus strain.


Summary - Development of a CEN-ISO horizontal standard method for detection of Cronobacter
The availability of a reliable and internationally accepted reference method for detection of Cronobacter in powdered infant formula is an essential tool to verify compliance with regulatory requirements by public health authorities and manufacturers. ISO-TS 22964:2006 was developed as a temporary solution for this purpose, but shortly after being issued it was decided to prepare a full-fledged horizontal CEN-ISO standard.
A summary will be given of the work done thus far, in particular with respect to the modifications that are envisaged to address the main shortcomings of TS 22964:

  • The scope will be extended to all types of powdered infant formula (incl. soy- based) and infant formula ingredients.
  • It will take into account the latest taxonomical revisions (e.g. definition of the genus Cronobacter and phenotypically related species)
  • It will no longer use yellow pigment production as a confirmation criterion
  • The enrichment broth (mLST) and chromogenic isolation agar (ESIATM) are too selective and need to be replaced by media that will also allow the detection of strains that are very susceptible to commonly used inhibitors of gram positive microorganisms.
  • The main performance characteristics of the new standard will be determined

Based on the results obtained during an extensive comparative/collaborative trial a method based on the utilization of Cronobacter Screening Broth (CSB) in combination with modified DFI agar appears to be the most suitable procedure to be adopted in the new standard.

His POWERPOINT can be found here.

Oxoid Thermofisher Scientist Patrick Duggan Address Culture Media For Isolation and Detection of Cronobacter Species

 Editor's Note: This is another report on the presentations that were made in Dublin earlier this year at the 1st International Meeting on Cronobacter (Enterobacter Sakazakii).  In this segment, we hear from Dr. Patrick Druggan, Oxoid Ltd., Thermo Fisher Scientific, Basingstoke, Hampshire RG24 8PW, United Kingdom.

Biography: Patrick Druggan  is Principle Scientist, Oxoid Thermofisher, Basingstoke, UK.

He received an Honours BSc in Food Science from the University of Strathclyde, Glasgow, UK. He has worked in the diagnostics industry for 22 years. He designed his first chromogenic medium in 1989 while working at Gibco.

Patrick studied part-time for his Ph.D. at the Pharmacy Department of University of Brighton, UK. His thesis was on improvements in the resuscitation of heat-injured Salmonella species from processed food samples.

He synthesized a number of autocytotoxic compounds that could be used during pre-enrichment to inhibit competitive microflora while allowing injured Salmonella spp. to resuscitate and grow.

This invention lead to the development of Inhibigens.™ His skills in chemistry and microbiology have allowed him to design a number of successful rapid biochemical tests and chromogenic culture media, including Druggan-Forsythe-Iversen Agar for the isolation of Cronobacter spp. 

Summary – - Culture media for isolation and detection of Cronobacter species

In 2001 a pre-term infant died of meningitis caused by Enterobacter sakazakii (Cronobacter spp.).  Infant formula milk (IFM) was implicated as a potential source of the infection.

The Food and Drug Administration (FDA) independently develop a method for enumeration of this emerging  pathogen in IFM using culture collections from national bodies that have later been shown to be poorly defined.

This method was introduced in 2002 and has regulatory standing for the import of IFM and skimmed milk powder in to the USA and a number of other countries. The FDA method is a modification of the procedure for the detection of Enterobacteriaceae, with the addition of yellow pigmentation of colonies for presumptive identification of Cronobacter spp.

It should be remembered that the FDA method was developed in a short time due to a public health concern, and this would have put a time constraint and significant pressure on those working on Enterobacter sakazakii (Cronobacter) to get a working method in the field as soon as possible. The FDA method has been shown to have a sensitivity of around 50 percent and a specificity of around 70 percent. Only 75 percent of Cronobacter strains phenotypically express yellow pigmentation, and the low specificity of the method coupled with the recommendation that only five presumptive Enterobacteriaceae colonies are tested from Violet Red Bile Glucose Agar (VRBGA) may explain the poor sensitivity of the method.

Assuming the prevalence of Cronobacter spp. in IFM is around 2 percent, the FDA method will fail to detect around 50 percent of batches contaminated with Cronobacter, while around 95 percent of rejected batches will not contain this organism.

This high rate of failure has lead many stakeholders to question the usefulness of the FDA method. This presentation reviews developments in culture media since the release of the FDA method in 2002, with specific emphasis on media that have improved the specificity of methods for Cronobacter spp. The unique phenotypic trait of this emerging pathogen that aid and hinder design of methods is discussed.  

POWERPOINT is here.

Dublin's Professor Fanning Speaks About Molecular Identification Methods for Cronobacter spp.

Editor’s Note: We next are going to hear from Professor Seamus Fanning of University College Dublin, addressing Molecular identification methods for Cronobacter. He also spoke at the Dublin conference on Cronobacter.


Biography:  Seamus Fanning is the Professor of Food Safety & Zoonoses and the Director of the Centre for Food Safety, University College Dublin. Professor Fanning is an editor of Research in Microbiology and a member of the editorial board of the Journal of Food Protection.

Professor Fanning received an Honours BSc in Biochemistry from NUI, Cork, where he also completed his PhD in Microbiology and Molecular Genetics. Current research interests include the application of molecular methods to Food Safety to control zoonotic microorganisms associated with human disease. A significant part of this work relates to the characterization of the genetic mechanisms contributing to the emergence of multiple drug resistance (MDR); the role of membrane bound efflux pumps in MDR and virulence and how these phenotypes are regulated at a local and global level.
Also, in the past few years the UCD Centre for Food Safety has published several papers describing the detection and characterization of Cronobacter. Professor Fanning is a member of the Microbiology Sub-Committee of the Food Safety Authority of Ireland (FSAI), the Scientific Advisory Committee of safe food and was recently appointed by the European Food Safety Authority (ESFA) to a working group to provide expert opinion on the emergence of antibiotic resistance in food. He also served as a member on the FAO/WHO expert panel on Enterobacter sakazakii in follow-up formula.


Summary: Molecular identification methods for Cronobacter spp.


Historically the ancestry of the genus Enterobacter can best be described as nebulus and confusing. In the 1970’s and 1980’s considerable movement of species, originally assigned to this genus occurred, and these re-designations arose because of initial misplacements, based on older phenotypic and morphological approaches to describing taxonomy.
Currently the genus Enterobacter comprises a large and heterogenous group of organisms within the Enterobacteriaceae family being accounted for by 16 distinct species. Enterobacter sakazakii (E. sakazakii) is one of these species and the only member of the genus recognised as a food-borne pathogen. Following a revision of Enterobacter taxonomy, a new genus Cronobacter was devised which is synonymous with E. sakazakii. Cronobacter consists of a least five distinct species and an additional genomospecies, Cronobacter sakazakii (C. sakazakii), C. dublinensis, C. malonaticus, C. muytjensii, C. turicensis and C. genomospecies I. A further three sub-species of C. dublinensis are also recognised. Correct identification of these organisms is important in order to improve our understanding of the broader epidemiology of the members of this new genus.
In recent years there have been rapid improvements in the provision of microbiologically-based culture approaches to isolate and identify these organisms. A number of molecular identification methods have also been proposed, however the recent recognition of multiple species that share less than 70 percent DNA-DNA similarity has important implications for the sensitivity and specificity of these methods. In this paper, three examples of the application of molecular-based detection strategies for the identification of Cronobacter will be presented.
These will include strategies to identify the genus, specific targets that are thought to be related to pathogenicity and the development of a molecular-based approach to begin to define the O-serotypes of C. sakazakii. Although by no means complete, these examples will illustrate some of the current and future challenges to enable a more refined and reliable molecular-based approach to the identification of all Cronobacter spp.
The development of appropriate molecular methods will facilitate not only a rapid identification of an isolate, but in addition complement the more traditional microbiological-based methods.


POWERPOINT is here.

It's All In The Enterobacteriaceae Family For University of Bern's Dr. Kuhnert

Editor's Note: This is another report on the presentations that were made in Dublin earlier this year at the 1st International Meeting on Cronobacter (Enterobacter Sakazakii). Below we hear from Professor Peter Kuhnert of the Institute of Veterinary Bacteriology, University of Bern, Switzerland.

Biography:  Peter Kuhnert is working at the University of Bern, Switzerland as an associate professor in bacteriology. He completed a PhD in molecular biology studying gene regulation of the porcine TNF-locus.
As a postdoc at the Weizmann Institute of Science in Israel he focused on the regulation of the human TNF-receptor genes and its role in the immune response. After his return 1994 he switched topics and is since then working at the Institute of Veterinary Bacteriology where he focuses on bacterial virulence, phylogeny and taxonomy.  His work includes pathotyping of E. coli, genotyping of foodborne pathogens with an emphasis on Campylobacter, pathogenesis and virulence mechanisms of Pasteurellaceae as well as work on Mycoplasma hyopneumoniae.

Summary - Multilocus sequence analysis (MLSA) of Cronobacter and related taxa Genetic similarity as determined by DNA-DNA hybridization is still considered the ‘gold standard’ method to determine relatedness between bacterial species. Nevertheless, it is very time consuming and cumbersome to perform and requires cross-hybridization between representatives of a species and related taxa. Moreover, variation between experiments, techniques and laboratories make exchange and comparison of data difficult. Whole genome sequence comparisons could be an alternative to DNA-DNA hybridization however, data handling and the
open question as to what genes should be used for defining genome similarity cannot be neglected. Therefore, for taxonomic purposes investigating as many isolates of a species as possible in order to respect the biodiversity of taxa, a few representative genes indicative for genetic similarity between isolates is the optimal way to go. Recently, we showed that the three genes recN, rpoA, and thdF can be used to estimate whole genome similarity of representatives of the family Pasteurellaceae [Kuhnert & Korczak (2006) Int.J.Syst.Evol.Microbiol 152: 2537-2548]
In the presented work multilocus sequence analysis (MLSA) based on recN, rpoA and thdF genes was done on more than 30 species of the family Enterobacteriaceae with a focus on Cronobacter and the related genus Enterobacter. The sequences provided valuable data for phylogenetic, taxonomic and diagnostic purposes. Phylogenetic analysis showed that the genus Cronobacter forms a homogenous cluster related to recently described species of Enterobacter, but distant to
other species of this genus. Combining sequence information on all three genes is highly representative for the species’ percentage of GC-content used as taxonomic marker. Sequence similarity of the three genes and even of recN alone can also be used to extrapolate genetic similarities between species of Enterobacteriaceae, being an alternative to DNA-DNA hybridization. Finally, the rpoA gene sequence, which is the easiest one to determine, provides a powerful diagnostic tool to identify and differentiate pathogens of this family. The comparative analysis gives important
insights into the phylogeny and genetic relatedness of the family Enterobacteriaceae and will serve as a basis for further studies and clarifications on the taxonomy of this large and heterogeneous family.

Powerpoint: Find it here.

USA's Dr. Ben Tall Reports on Cronobacter diversity

Editor's Note: This is another report on the presentations that were made in Dublin earlier this year at the 1st International Meeting on Cronobacter (Enterobacter Sakazakii). This time we focus on Dr. Ben Tall from the United States.

Biography: Dr Ben Tall completed his PhD at the University of Maryland at Baltimore (UMAB) in 1988. His postdoctoral training took place with the Center for Vaccine Development, UMAB, and as a senior staff fellow with the Div. of Microbiol. (DMS), Microbial Ecol. Br., CFSAN, FDA. He currently works within the Virulence Mechanisms Branch of CFSAN.

His research interests include: pathogenic mechanisms of foodborne enteric bacteria; characterization and expression of adherence factors; fimbriae ultrastructure, effects of environmental influences on bacterial attachment/invasion mechanisms associated with foodborne enteric pathogens such as enteropathogenic E. coli, Salmonella spp., Cronobacter spp., Vibrio spp. and the use of BSL-3 lab protocols and methods for the detection of bio-threat agents from foods. Dr Tall has served in the District of Columbia Branch of the American Society for Microbiology (ASM; 1992-1999), and is currently serving on the Committee for the Advancement of FDA Science (2008). He has received a total of 28 awards including U.S. Health and Human Services Secretary’s Award for Distinguished Service; CFSAN Excellence in Laboratory Science Scientific Achievement Award, Several CFSAN Exceptional Achievement Awards, and a FDA Commissioner’s Special Citation award. He has given 31 invited talks, published more than 73 refereed scientific articles or Book Chapters and has given over 140 abstract presentations at international scientific meetings.

Summary: Phenotypic diversity among Cronobacter supp. (Enterobacter sakazakii) One hundred sixty-five isolates of Cronobacter spp. (formerly known as Enterobacter sakazakii) from clinical samples, foods, food processing areas and isolates of unknown origin were phenotypically characterized by API20E; VITEK 2.0 Compact GN (VITEK), and Biolog Microlog3 microbial identification analytical systems; and by Biolog Phenotypic Microarray (PM) analysis.  Also assessed were other phenotypic traits such as expression of rugosity, colony pigmentation, α-glucosidase activity, antibiotic susceptibility, Congo Red (CR) and Calcofluor (CAL) binding and growth on two chromogenic media. API20E analysis identified all isolates as E. sakazakii and VITEK analysis correctly identified 159 of 160 isolates (99.4 %) as E. sakazakii. In contrast, only 23 (60.5%) of a subset of 38 Cronobacter isolates were correctly identified by the Microlog ID system. Antibiotic susceptibility of 46 clinical isolates showed that all isolates were resistant to Ampicillin, Cefazolin, Amoxicillin, Cefalotin, and Cefpodoxime while a few isolates were resistant to Cefoxitin, Imipenem, Ertapenem, Nitrofuratoin, and Cefuroxime. Comparative PM analysis of 95 isolates demonstrated the metabolic diversity among the Cronobacter spp. Based on utilization of 89 carbon sources by known Cronobacter spp. isolates, the different species could be distinguished from one another and from Enterobacter cloacae. Approximately 53 (32%) of the isolates expressed the rugose colony phenotype when grown at 30°C or 37°C. Over 132 (80%) of the isolates produced yellow pigmented colonies when grown at 30°C, whereas the remaining 33 isolates produced white colonies.

All isolates produced typical blue-grey to blue-black E. sakazakii-like colonies on ESPM agar, whereas, 152 (92%) of the isolates produced typical blue-green Cronobacter-like colonies on Druggan-Forsythe-Iversen (DFI) medium when both media were incubated at 37ºC for 24 h. Thirteen isolates which gave atypical colony phenotypes on DFI showed variable α-glucosidase activity. However, PCR analysis detected the presence of both α- gluA and α-gluB genes in these isolates. Lastly, CR- and CAL- binding studies showed that over 140 (87 %) of the isolates expressed both curli and cellulose when grown at 37°C, yet only 21 (13%) of the isolates expressed both structures at 23°C. Tn5 mutagenesis studies revealed two CAL-binding negative and one CR-binding negative mutant. Sequences around the Tn5 insertions in the CAL-binding negative mutants were similar to a RadA ATP-dependent serine protease gene and to an aminotransferase gene. The sequence associated with the CR-binding defective mutant, was found to be similar to an arginine repressor gene. PM analysis showed a variety of altered phenotypes such as different carbon utilization patterns, different osmolarity and acid-base tolerance phenotypes among these mutants. These results demonstrate that Cronobacter spp. display numerous phenotypes which may have significant implications, not only in understanding bacterial diversity, but in understanding survival strategies of the pathogen in confronting multiple stresses in the food processing environment and in hosts.

Powerpoint: Dr. Tall's slide can be found HERE.

Dr. Iversen Introduces The Updated Version Of E. Sakazakii; Now Call It Cronobacter

Editor's Note:  In January, the 1st International Meeting on Cronobacter (Enterobacter sakazakii) was held in Dublin. As we can get to it, we are featuring summaries from some of the main speakers along with links to their power point presentations.

We begin with Ireland's own Dr. Carol Iversen.

Biography:  After completing a PhD at Nottingham Trent University, Carol Iversen worked for Nestlé Research Centre, Switzerland, where she led an international collaboration to define the taxonomy of Enterobacter sakazakii and propose a new genus, Cronobacter.
Dr. Iversen then joined the research team at the Institute for Food Safety and Hygiene, University of Zürich, to continue work on isolation methods and virulence characterisation of these organisms before moving to Ireland under an IRCSET postdoctoral fellowship in 2008.
Dr. Iversen is currently engaged in research on foodborne pathogens at the Centre for Food Safety, UCD. She is also a representative for the National Standards Authority of
Ireland on the ISO and CEN committees for Microbiology and Microbial Contamination, and is co-project leader of the ad’hoc group for development of a horizontal EN ISO
standard for the detection of Cronobacter (E. sakazakii).

Summary: What is (and isn’t) Cronobacter?  

Enterobacter sakazakii is an opportunistic pathogen that can cause meningitis, necrotising enterocolitis, and bacteraemia infants. It was first designated as a species in 1980 by Farmer et al. and several outbreaks in NICUs have been linked to contaminated powdered infant formula.
The organism is therefore of concern to infant food manufacturers as well as clinical microbiologists and food safety regulators. In 2008 the taxonomy of E. sakazakii was updated using a polyphasic approach based on extensive geno- and phenotypic evaluations. This resulted in the description of five novel species and the proposal that these be incorporated into a new genus, Cronobacter, which is contaxic with E. sakazakii. The isolation of Cronobacter is complicated by the existence of closely related species, Enterobacter pulveris, E. helveticus and E. turicensis. These species share
similar characteristics to Cronobacter and occur in the same ecological niches including infant foods. However, no health risk has been attributed to these organisms.

Her Powerpoint is Here.

Bad Whey Not the Route Into China's Infant Market.

 

 

Whey protein being exported from the United States and New Zealand has been stopped at the borders of the People's Republic of China, the Shanghai Daily reports.

The whey protein was, according to China, contaminated by enterobacter sakazakii, a potentially fatal bacteria for infants that can cause bacteraemia, meningitis and necrotising enterocolitis.

The whey protein was being shipped to the infant products manufacturer Beingmate Group Co Ltd and Hangzhou-based Wahaha Health Food Co Ltd.

A total of 37 tons of whey protein imported by Beingmate from the United States and 5.2 tons Wahaha imported from New Zealand were tainted with the bacteria.

All the whey protein was " rejected or destroyed." The Shanghai Daily did not name the companies importing the bad whey.  For more, go here.

50 Year Old Species Gets New Name: Cronobacter

In January some of the world's most distinguished health scientists gathered in Dublin for what they called "1st International Conference on Cronobacter (Enterobacter sakazakii)"

We've been reviewing the conference proceedings.   It seems that one of the things they did was change the name of Enterobacter sakazakii to Cronobacter.

Being diplomatic about it, they also recognized both the memory of Dr. Riichi Sakazaki (August 21, 1920 - January 11, 2002) for whom the organism is named (see picture) and Dr. Don J. Brenner,  Frances Brenner, Richard Fanning,  Arnold J. Steigerwalt, and the late Mary Alyce Fife-Asbury who were all involved in the original Centers on Disease Control(CDC) studies that led to it being recognized as a separate species.  They also gave a salute to Dr. Harry Muytjens for "his pioneering work in uncovering its ecology and epidemiology in cases of neonatal meningitis and the important role of powdered infant formula."

It's been 50 years since the first case of neonatal meningitis due to the organism now known as Cronobacter (Enterobacter sakazakii) was documented.  That case occurred in 1958, and was reported in 1961 by Urmenyi and White-Franklin.

Obviously, this name-changing is going to eventually be recognized in the name of this blog.  In the meantime, and probably for a long time, we will do what every scientist in Dublin did, which is to use the old and new names interchangeably. 

Iowa Family Sues Maker Of Enfamil In Federal Court: Seeks Damages, Requests Jury Trial

 Daniel Korte was one of the twin boys born prematurely on April 23, 2007 at Mercy Medical Center in Des Moines, Iowa.  Because of the pre-mature birth, Daniel remained in Mercy’s NICU unit where he was fed Enfamil Powdered Human Milk Fortifier for the first time on May 5, 2007.

This week, Patrick and Michelle L. Korte, Daniel’s parents, sued Mead Johnson Nutritionals, the spin-off of Bristol Myers Squibb Co. that makes the Enfamil Powdered Human Milk Fortifier.

The family alleges that within hours of consuming the Enfamil product, Daniel was in tachycardia and blood cultures taken revealed the presence of the Enterobacter Sakazakii bacteria.

“The E. Sakazakii bacteria that infected Daniel Korte came from the powdered human milk fortifier he received out of the Enfamil container,” says the lawsuit filed in U.S. District Court in Iowa.

The two year old continues to suffer from severe brain and other physical damages caused by the E. Sakazakii, which the Korte family blames the manufacturing defect in the Enfamil product, which they says was produced in a defective and unreasonably dangerous condition of contamination.

Evansville, IN-based Mead Johnson just raised $724 million in its initial public offering.  Symbol for its now publicly traded stock is MJN.  Its IPO was priced at $24 a share.

The Korte family is represented by attorneys William R. King of the Davis, Brown, Koehn, Shors & Roberts law firm in Des Moines, and Andrew Weisbecker and Bruce Clark of Marler Clark in Seattle.  In seeking damages for the Korte family, the lawyers have asked for a jury trial.