Skip to main page content

• HOME
• Current Issue
• Archive
• Alerts
• About ASM
• Contact us
• Tech Support
• Journals.ASM.org

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mullane, N. Articles by Fanning, S. Search for Related Content PubMed PubMed Citation Articles by Mullane, N. Articles by Fanning, S. Agricola Articles by Mullane, N. Articles by Fanning, S.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, October 2008, p. 5913-5917, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.00745-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Dissemination of Cronobacter spp. (Enterobacter sakazakii) in a Powdered Milk Protein Manufacturing Facility

N. Mullane,¹ B. Healy,¹ J. Meade,¹ P. Whyte,¹ P. G. Wall,² and S. Fanning^1*

Centres for Food Safety & Food-borne Zoonomics, UCD Veterinary Sciences Centre, School of Agriculture, Food Science and Veterinary Medicine,¹ School of Public Health & Population Sciences, University College Dublin, Belfield, Dublin 4, Ireland²

Received 30 March 2008/ Accepted 7 July 2008

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The microbial contamination of air filters and possible links to contaminated product in a powdered milk protein-processing facility were investigated. Over a 10-month period, seven air filters, the environment, and powdered product were analyzed for the presence of Cronobacter spp. The effects of air filter installation, maintenance, and subsequent dissemination of Cronobacter were investigated. A total of 30 isolates were characterized by pulsed-field gel electrophoresis (PFGE). PFGE revealed the presence of three clonal populations distributed throughout the manufacturing site. This study highlights the need for proper installation of air filters to limit the dissemination of microorganisms into processing sites.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Enterobacter sakazakii is an opportunistic pathogen that is occasionally associated with food-borne illness in neonates and infants (4, 6, 18). Recent taxonomic studies led to alternative classification of E. sakazakii into several new genomospecies in a novel genus, Cronobacter (12, 13).

The natural habitat of Cronobacter is currently unknown. The identity of a primary reservoir (if there is any) remains to be determined. Since 1958, numerous cases of E. sakazakii infant infection have been documented, and there have been at least 111 cases of infection and 26 associated deaths (18). Even though the incidence of reported infections is low, high mortality rates have been reported for infants who present with Cronobacter meningitis (4, 6, 17).

While Cronobacter has been isolated from a wide range of foods and environmental and clinical sources, powdered infant formula (PIF) has been identified as the dominant vehicle of transmission (10, 11, 18, 20). Unlike commercially available ready-to-feed liquid infant formula, which is sterile, PIF (including dried bovine milk and milk products) is not a sterile product. PIF has been known to be contaminated, on occasion, with bacterial pathogens, including Bacillus spp., Clostridium spp., Staphylococcus spp., and Enterobacteriaceae, notably Cronobacter (9). Therefore, hygienic measures and practices must be used during the manufacture of formula to minimize entry of contaminants into the process.

Cronobacter is often isolated from the environment in milk powder and PIF manufacturing facilities (7, 10, 14, 15, 19). It is generally assumed that Cronobacter contamination of a product occurs in the processing environment at stages after pasteurization, including drying or packing. The prevalence of Cronobacter following the drying stage may be due (in part) to the organism's ability to resist drying or osmotic stress (2, 5, 21). Limited information is available about the contamination entry points in facilities and the routes of dissemination into powdered end products. Hazardous microorganisms found in milk powder products can be transferred by a number of routes, including air.

Air is a potential source of hazardous microorganisms. Air intake in low-risk areas and especially in high-risk areas must be controlled. Air-handling systems servicing high-risk areas must supply air that is a desirable quality and at an overpressure that prevents the ingress of external air. The types of airborne contamination found previously in a milk powder production facility include dust, water droplets, and airborne microorganisms (14, 15, 19). Non-spore-forming microorganisms can become aerosolized in water droplets or when they are attached to dust (1, 16). Dust is generated from a wide variety of processing events, while water droplets can be generated as a result of cleaning operations. Environmental air filters in the air-handling units provide clean air to a controlled area.

The aims of this study were to investigate Cronobacter contamination resulting from contaminated air filters in a powdered milk protein-processing facility and to identify subsequent routes of dissemination of Cronobacter.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Facility.
The study was conducted in a powdered milk protein production facility. Casein is the primary protein found in liquid milk, accounting for approximately 80% of total protein content. Rennet casein is produced when the enzyme chymosin causes casein to coagulate, and then indirect heat is applied to maximize casein precipitation. The casein curd is separated from the whey by centrifugation, washed, spray dried, milled, and bagged. The powdered protein is subsequently sold as an ingredient for food and nutritional products.

Air handling.
A three-step air filtration system was used in this facility to reduce the microbial load associated with air intake prior to entry into the spray dryer, the mill, and other downstream processing areas. Externally drawn air coming into the facility was initially coarse filtered with fiberglass-type screens to trap large particulate matter entering the blower room (Fig. 1). These screens are low-efficiency dust filters used to limit the ingress of dust from external air entering the blower room. This coarse filtration was followed by primary and secondary filtration for the air intake of the dryer and the mill, using a first-stage G4 filter coupled with a second-stage F8 filter (as recommended by CEN EN 779:2002 European standard classification of air filters [8]). The pleated primary filters were low-efficiency filters, while the secondary filters were medium- to higher-efficiency filters and were designed to prevent the release of dust if the primary filter failed. This filter set was employed to control the entry of hazardous material (biological and physical) into the process.

View larger version (31K): [in this window] [in a new window]

FIG. 1. Floor plan of the powdered milk protein production facility investigated in this study. Curved open arrows indicate the direction of the incoming airflow, and solid arrows indicate the process flow. The colored dots indicate the locations of shared clonal isolates (see Fig. 2).

Sampling plan.
This study was performed in the powdered milk protein-processing facility from April 2007 to January 2008. Rennet casein powders and, in addition, once-off Cronobacter environmental monitoring were also included. Environmental monitoring for Cronobacter was sporadic, and the samples consisted of a production vacuum sample and samples obtained by swabbing the dryer air outlet, the inside of the housing of the dryer cyclone, and the air intake of the mill dehumidifier.

A total of seven air filters were analyzed as part of a routine factory overhaul of filter units (Table 1). The primary air filter servicing the spray dryer was subjected to further analysis by a Cronobacter most-probable-number (MPN) method and identification of non-Cronobacter Enterobacteriaceae. Twelve rennet casein powders were analyzed for the presence of Cronobacter.

View this table: [in this window] [in a new window]

TABLE 1. Overview of sampled air filters in the rennet casein facility

Isolation and identification of Cronobacter.
Five 10-cm² sections representing the middle and sides were aseptically cut from each filter unit. Swab samples were collected with sterile cotton swabs moistened in sterile peptone water and directed over a 5-cm² surface area. Swabs and air filter sections were each aseptically placed into 200 ml buffered peptone water (Difco Laboratories Le Pont de Claix, France) and homogenized gently. Powder and vacuum samples were diluted 1:10 (wt/vol) in buffered peptone water. Cronobacter was isolated from all types of samples as recommended by ISO/TS 22964 (http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FTS+22964%3A2006) using DFI agar (CM1055; Oxoid, Hampshire, United Kingdom).

The identities of all presumptive Cronobacter isolates obtained during this study were further confirmed by real-time PCR using a primer set and probe that targeted the dnaG gene in the macromolecular synthesis operon (23). The species to which confirmed Cronobacter isolates belonged were determined using key biochemical tests as described by Iversen et al. (12).

Additional analysis of the primary filter of the spray dryer.
With approximately 80% of the air filter remaining, 9.3 g of dust was aseptically removed from the surface of the primary filter of the dryer and collected in a sterile stomacher bag. The number of Cronobacter CFU was determined by the MPN assay (22). Based on the growth observed on DFI agar at higher dilutions, the MPN of survivors was calculated using a "five-tube" technique. The dust was also analyzed using the Food and Drug Administration method for detection of Cronobacter with violet red bile glucose (Oxoid, Hampshire, United Kingdom) agar to detect Enterobacteriaceae (http://www.cfsan.fda.gov/comm/mmesakaz.html). All isolates were identified using an ID32E biochemical gallery (bioMerieux, Marcy-l'Etoile, France).

Determination of molecular subtypes by PFGE and band analysis.
The subtypes of all Cronobacter isolates were determined by pulsed-field gel electrophoresis (PFGE) using previously described methods (19).

DNA fingerprints were stored as tagged image file format (TIFF) files and imported into the BioNumerics software (Applied Maths, Sint-Martens-Latem, Belgium), and a dendrogram was created using the Dice coefficient and the unweighted-pair group method with arithmetic means. The genetic diversity of the Cronobacter isolates was compared at a level of similarity of 80%, with a position and optimization tolerance of 1.5%.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
A sequential series of air filters was examined microbiologically following replacement during a routine overhaul in a powdered milk protein production facility. Five sections were sampled from each filter. In addition, environmental and rennet casein powder samples were included in the study.

All seven air filters were positive for Cronobacter, yielding 24 isolates. The results were as follows. The sections analyzed from two coarse dust wall filters, labeled a and b (Fig. 2), were 40 and 20% positive, respectively; the sections analyzed from two primary filters, also labeled a and b (Fig. 2), of the spray dryer were both 100% positive; and the sections analyzed from the secondary filter were 60% positive. The sections from the primary and secondary filters of the mill were both 80% positive. A total of three Cronobacter isolates were obtained from environmental samples, including the production vacuum sample and samples from swabs of the dyer outlet and dehumidifier air intake. Additionally, three isolates were recovered from rennet casein powder at a frequency of 25%.

View larger version (25K): [in this window] [in a new window]

FIG. 2. Representative XbaI macrorestriction DNA profiles of Cronobacter isolates from a milk-processing facility. A dendrogram showing the relationships between isolates was created using the BioNumerics software. The colored dots indicate three disseminated strain types.

XbaI subtyping by PFGE was conducted for all 30 strains. Each strain produced between 8 and 13 DNA fragments ranging from 48.5 to 1,000 kbp long. A dendrogram showing the fingerprint pattern similarities among the isolates was constructed (Fig. 2). A low degree of genetic diversity was observed among the isolates belonging to three DNA pulsotypes (designated pulsotypes P-1 through P-3), as shown in the dendrogram. Each pulsotype contained between 3 and 14 isolates. Pulsotype P-1 (Fig. 2) contained the largest number of isolates (n = 14; 47%), including isolates from filter samples from the coarse wall filter and both the primary and secondary filters for the drying and milling operations. In addition, this pulsotype included isolates from rennet casein powder and from a swab of the dryer air outlet. Pulsotype P-2 (Fig. 2) was the second largest cluster and contained 13 (43%) isolates recovered from both primary filters for the dryer and both secondary filters for the dryer and the mill. This pulsotype also contained isolates from a swab of the air intake dehumidifier of the mill and from a production vacuum sample. The third pulsotype (pulsotype P-3) (Fig. 2) contained three isolates (10%), was 73% similar to pulsotype P-2, and included isolates from the coarse wall screen and from the primary filter for the dryer. No single sample or location contained all three pulsotypes. The three pulsotypes were identified as Cronobacter sakazakii (pulsotype P-1) and Cronobacter malonaticus (pulsotypes P-2 and P3).

All locations for the three pulsotypes were mapped to locations in the facility (Fig. 1). Pulsotype P-1 was the most ubiquitous pulsotype and was recovered from six of seven filters, the dryer outlet, and the final product. Pulsotype P-2 was isolated from four of seven filters tested, the production vacuum, and the air intake dehumidifier for the mill. Pulsotype P-3 was found on the coarse wall filter and the primary filter of the dryer.

Analysis of the dust from the primary filter for the spray dryer revealed 111 MPN Cronobacter per g of dust. Members of the Enterobacteriaceae that were not members of Cronobacter recovered from this dust included Enterobacter cloacae, Citrobacter braakii, Citrobacter sedlakii, and Klebsiella pneumoniae. Pseudomonas aeruginosa and Acinetobacter baumannii were also detected on the filters. These organisms were not investigated further.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The production site studied supplied rennet casein powder that was subsequently included as an ingredient in various food products but not in PIF. A total of 30 Cronobacter isolates were recovered from different processing sites, including air filters (n = 24), environmental samples (n = 3), and the final powdered product (n = 3). This study used PFGE to assess the fingerprint pattern similarities between these isolates in order to establish possible routes of dissemination of contamination and to identify failures at critical control points to limit contamination of the final product.

General handling of ingredients, spray drying, and milling operations can create aerosols. Aerosols can also be generated from cleaning operations, including wet cleaning (in the form of water droplets) and dry cleaning (where aerosols are generated by sweeping actions or directly from the exhaust of vacuum cleaners, which represents a hazard unless appropriate filters are used). Dust particles are a significant hazard as even in slowly moving air, small particles (0.1 to 5.0 µm) can remain airborne for hours and potentially travel long distances from their source (16). Therefore, it is recommended that high-pressure hoses not be used in high-hygiene areas and that cleaning equipment be sanitized regularly to prevent buildup of microorganisms. Correct selection, fitting, and maintenance of air filters are essential to control the ingress of airborne contaminants into processes and ultimately to exclude hazards from the final powdered product.

Indistinguishable Cronobacter isolates were observed at various processing sites (Fig. 1 and 2). A total of three pulsotypes were identified, indicating that the genetic diversity was low. Pulsotype P-1 was recovered from all seven air filters, including both coarse wall filters. We could not definitively conclude that the isolates originated from external air as aerosolization of dust within the blower room could also have accounted for the bacteria on the filter. Both the P-1 and P-2 pulsotypes were also found on the primary and secondary air filters from the spray dryer and the mill. Dust recovered from a primary pleated air filter from the dryer yielded 111 Cronobacter MPN per g. The elevated number of Cronobacter bacteria present on this filter indicates that there was recurring contamination from the processing environment and/or proliferation due to the presence of moisture on the primary filter. The presence of pulsotypes P-1 and P-2 on both secondary filters suggests that both primary filter units failed to control microbial contamination. The presence of pulsotype P-1 in the final rennet powder and the presence of pulsotype P-2 in the dehumidifier could be explained by failure of the secondary filtration units.

Furthermore, pulsotypes P-1 and P-3 were indistinguishable from isolates recovered from an adjoining acid casein facility (data not shown). Walls physically separated the two processes, but open doorways between the two areas allowed exchange of air and unrestricted access for personnel. Positive samples in the acid casein plant included samples from the production vacuum, the bag-off filter (used to decrease product loss and avoid release of powder dust into the atmosphere from exhaust air), and the final powdered product, suggesting that there was wider dissemination between these sites.

A primary G4 air filter, with medium efficiency (25 to 30%), removes large dust particles from air, while the F8 air filter specifications state that this filter type is 90 to 95% efficient at trapping 0.4-µm-diameter particles. A common misconception is that filters should be selected based on particle size. However, a microorganism is often larger when it is suspended in a water droplet or attached to a dust particle. This filter combination has long been used by the milk-processing industry (and PIF industry) to supply air to "high-care" areas and is a well-established means of controlling microbial contamination, but it works only when it is installed and maintained at a satisfactory level (16; J.-L. Cordier, personal communication). Inspection of the primary air filters of the spray dryer and mill revealed significant accumulations of dust on the intake sides of the filters. Examination of the filter housings showed that the filters were inadequately fixed in position and that the gasket between the filter and the housing was often damaged. We hypothesize that, as the pressure progressively increased due to accumulation of dust, an increased amount of air bypassed the filter via a break in the gasket, thereby rendering the primary filtration step ineffective. It was not possible to assess the operation of the secondary filters, as these filters were inaccessible at the time of inspection.

It is acknowledged that hazard analysis and critical control point plans play an important role in the control of microbiological hazards. All milk powder and PIF manufacturers incorporate the principles of such plans into their control programs, and air filters are an important critical control point that must be considered. Air intake filters are used to remove particulate matter and other physical hazards, but correct installation and maintenance are critical. Our findings highlighted the need to monitor air-handling units to ensure that the desired performance is being achieved. Control of moisture and humidity in air and on filters must also be considered in the control of microbial contamination. Humidity is controlled by passing hot air through the cooling coil of a dehumidifier, where condensation and drainage of the resulting water occur. Our study identified Cronobacter in the air intake of the mill dehumidifier. This finding indicates that there is increased risk to the downstream process due to the likelihood of the presence of water and subsequent proliferation of bacteria at this site. The cooling coils must be considered a critical control point and disinfected as part of a manufacturing control program.

The ducts of air-handling systems should have inspection and cleaning access panels located at regular intervals. This allows cleaning of the ducts, especially critical areas such as filters and coils, when necessary. The cleanliness of internal duct surfaces should be monitored visually in conjunction with microbiological sampling either by swabbing or by using agar contact plates.

It is important to ensure that filters are maintained according to manufacturers' specifications and that performance of filters is controlled by using planned visual inspection schedules. Criteria for replacement are based on (i) when the filter manufacturer's maximum differential pressure of a filter has been reached, (ii) when the integrity of a filter has been compromised, and (iii) when company practice indicates that a planned filter change is required.

Satisfactory performance of air filters requires regular checking, and documentation of all maintenance and filter change is essential.

In conclusion, the installation of differential pressure gauges to monitor filter resistance and pressure drops, along with regular replacement of filters, especially those with low load capacities, should be considered. Appropriate air filter maintenance along with surveillance for Cronobacter spp. would contribute to reducing the dissemination of these pathogens in the food chain.

 
We acknowledge the financial support provided through Irish government Food Institutional Research Measure (FIRM) grant 05/R&D/D/363.

We thank Carol Iversen and Stephen O'Brien for providing helpful comments on the manuscript.

 
* Corresponding author. Mailing address: Centre for Food Safety, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. Phone: (353-1) 716 6082. Fax: (353-1) 716 6091. E-mail: sfanning{at}ucd.ie

Published ahead of print on 18 July 2008.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

1
1. Anonymous. 2006. Guidelines on air handling in the food industry. Trends Food Sci. Technol. 17:331-336.[CrossRef]
2
2. Arku, B., N. Mullane, E. Fox, S. Fanning, and K. Jordan. 2008. Enterobacter sakazakii survives spray drying. Int. J. Dairy Technol. 61:102-108.[CrossRef]
3
3. ASHRAE. 1999. ASHRAR Standard 52.2-1999. The American Society of Heating Refrigeration and Air Conditioning Engineers, Atlanta, GA.
4
4. Bowen, A. B., and C. R. Braden. 2006. Invasive Enterobacter sakazakii disease in infants. Emerg. Infect. Dis. 12:1185-1189.[Medline]
5
5. Breeuwer, P., A. Lardeau, M. Peterz, and H. M. Joosten. 2003. Desiccation and heat tolerance of Enterobacter sakazakii. J. Appl. Microbiol. 95:967-973.[CrossRef][Medline]
6
6. Drudy, D., N. R. Mullane, T. Quinn, P. G. Wall, and S. Fanning. 2006. Enterobacter sakazakii: an emerging pathogen in powdered infant formula. Clin. Infect. Dis. 42:996-1002.[CrossRef][Medline]
7
7. Drudy, D., M. O'Rourke, M. Murphy, N. R. Mullane, R. O'Mahony, L. Kelly, M. Fischer, S. Sanjaq, P. Shannon, P. Wall, M. O'Mahony, P. Whyte, and S. Fanning. 2006. Characterization of a collection of Enterobacter sakazakii isolates from environmental and food sources. Int. J. Food Microbiol. 110:127-134.[CrossRef][Medline]
8
8. European Committee for Standardization. 2002. Particulate air filters for general ventilation—determination of the filtration performance. EN 779:2002. European Committee for Standardization, BSI British Standards, London, United Kingdom.
9
9. Forsythe, S. J. 2005. Enterobacter sakazakii and other bacteria in powdered infant milk formula. Matern. Child Nutr. 1:44-50.[CrossRef][Medline]
10
10. Gurtler, J. B., J. L. Kornacki, and L. R. Beuchat. 2005. Enterobacter sakazakii: a coliform of increased concern to infant health. Int. J. Food Microbiol. 104:1-34.[CrossRef][Medline]
11
11. Iversen, C., and S. J. Forsythe. 2003. Risk profile of Enterobacter sakazakii, an emergent pathogen associated with infant milk formula. Trends Food Sci. Technol. 14:443-454.[CrossRef]
12
12. Iversen, C., A. Lehner, N. Mullane, E. Bidlas, I. Cleenwerck, J. Marugg, S. Fanning, R. Stephan, and H. Joosten. 2007. The taxonomy of Enterobacter sakazakii: proposal of a new genus Cronobacter gen. nov. and descriptions of Cronobacter sakazakii comb. nov., Cronobacter sakazakii subsp. sakazakii comb. nov., Cronobacter sakazakii subsp. malonaticus subsp. nov., Cronobacter turicensis sp. nov., Cronobacter muytjensii sp. nov., Cronobacter dublinensis sp. nov. and Cronobacter genomospecies 1. BMC Evol. Biol. 7:64.[CrossRef][Medline]
13
13. Iversen, C., A. Lehner, N. Mullane, J. Marugg, S. Fanning, R. Stephan, and H. Joosten. 2007. Identification of "Cronobacter" spp. (Enterobacter sakazakii). J. Clin. Microbiol. 45:3814-3816.[Abstract/Free Full Text]
14
14. Kandhai, M. C., M. W. Reij, L. G. Gorris, O. Guillaume-Gentil, and M. van Schothorst. 2004. Occurrence of Enterobacter sakazakii in food production environments and households. Lancet 363:39-40.[CrossRef][Medline]
15
15. Kandhai, M. C., M. W. Reij, K. van Puyvelde, O. Guillaume-Gentil, R. R. Beumer, and M. van Schothorst. 2004. A new protocol for the detection of Enterobacter sakazakii applied to environmental samples. J. Food Prot. 67:1267-1270.[Medline]
16
16. Lelieveld, H. L. M., M. A. Mostert, J. Holah, and B. White. 2003. Hygiene in food processing. Woodhead Publishing Limited, Cambridge, United Kingdom.
17
17. Mullane, N. R., R. Drudy, P. Whyte, M. O'Mahony, A. G. M. Scannell, P. G. Wall, and S. Fanning. 2006. Enterobacter sakazakii: biological properties and significance in dried infant milk formula (IMF) powder. Int. J. Dairy Technol. 59:102-111.[CrossRef]
18
18. Mullane, N. R., C. Iversen, B. Healy, C. Walsh, P. Whyte, P. G. Wall, T. Quinn, and S. Fanning. 2007. Enterobacter sakazakii, an emerging bacterial pathogen with implications for infant health. Minerva Pediatr. 59:137-148.[Medline]
19
19. Mullane, N. R., P. Whyte, P. G. Wall, T. Quinn, and S. Fanning. 2007. Application of pulsed-field gel electrophoresis to characterise and trace the prevalence of Enterobacter sakazakii in an infant formula processing facility. Int. J. Food. Microbiol. 116:73-81.[CrossRef][Medline]
20
20. Nazarowec-White, M., and J. M. Farber. 1997. Enterobacter sakazakii: a review. Int. J. Food. Microbiol. 34:103-113.[CrossRef][Medline]
21
21. Riedel, K., and A. Lehner. 2007. Identification of proteins involved in osmotic stress response in Enterobacter sakazakii by proteomics. Proteomics 7:1217-1231.[CrossRef][Medline]
22
22. Russek, E., and R. Colwell. 1983. Computation of the most probable numbers. Appl. Environ. Microbiol. 1646-1650.
23
23. Seo, K. H., and R. E. Brackett. 2005. Rapid, specific detection of Enterobacter sakazakii in infant formula using a real-time PCR assay. J. Food Prot. 68:59-63.[Medline]

---

Applied and Environmental Microbiology, October 2008, p. 5913-5917, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.00745-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mullane, N. Articles by Fanning, S. Search for Related Content PubMed PubMed Citation Articles by Mullane, N. Articles by Fanning, S. Agricola Articles by Mullane, N. Articles by Fanning, S.