The PulseNet National Database, established by the Centers for Disease Control and Prevention in 1996, consists of pulsed-field gel electrophoresis (PFGE) patterns obtained from isolates of food-borne pathogens (currently Escherichia coli O157:H7, Salmonella, Shigella, and Listeria) and textual information about the isolates. Electronic images and accompanying text are submitted from over 60 U.S. public health and food regulatory agency laboratories. The PFGE patterns are generated according to highly standardized PFGE protocols. Normalization and accurate comparison of gel images require the use of a well-characterized size standard in at least three lanes of each gel. Originally, a well-characterized strain of each organism was chosen as the reference standard for that particular database. The increasing number of databases, difficulty in identifying an organism-specific standard for each database, the increased range of band sizes generated by the use of additional restriction endonucleases, and the maintenance of many different organism-specific strains encouraged us to search for a more versatile and universal DNA size marker. A Salmonella serotype Braenderup strain (H9812) was chosen as the universal size standard. This strain was subjected to rigorous testing in our laboratories to ensure that it met the desired criteria, including coverage of a wide range of DNA fragment sizes, even distribution of bands, and stability of the PFGE pattern. The strategy used to convert and compare data generated by the new and old reference standards is described.

This multistate outbreak of E. coli O157:H7 infections was associated with consumption of mesclun lettuce from a single producer. Molecular subtyping facilitated the epidemiological investigation. This investigation increased the knowledge about current production practices that may contribute to the contamination of lettuce by microbial pathogens. Lettuce production practices should be monitored for microbiological safety.

An outbreak of Salmonella serotype stanley infections occurred in the United States and Finland in 1995. The outbreak was investigated through case-control studies in Arizona, Michigan, and Finland; by isolate subtyping; and by tracing and culturing of the implicated food. Alfalfa sprout consumption was the only exposure associated with S. stanley infections in Arizona (matched odds ratio [MOR] = 11.1; 95% confidence interval [CI], 1.4-513), Michigan (MOR = 5.5; CI, 1.6-23), and Finland (MOR undefined; CI, 4.9-infinity). US and Finnish patient isolates were a unique outbreak strain distinct from S. stanley isolates not linked to the outbreak. Alfalfa sprouts eaten by patients in 6 US states and Finland were traced to seed shipped by a Dutch shipper. Thus, it was concluded that alfalfa sprouts grown from contaminated seed caused an international outbreak of > or =242 S. stanley infections in > or =17 US states and Finland. This outbreak illustrates a new mechanism through which contamination of fresh produce can cause large, widely dispersed outbreaks.

SCHERICHIA COLI O157, SUCH AS E coli O157:H7, causes approximately 70000 illnesses and 60 deaths annually in the United States. 1 Illness is often characterized by severe bloody diarrhea; renal failure from hemolytic-uremic syndrome (HUS) may occur in 3% to 7% of cases. 2 Healthy cattle are believed to be the most important reservoir of E coli O157. 2 Humans usually become infected from contaminated food or water or from contact with infected animals, infected humans, or either's excreta. 3,4 Because E coli O157 has a low infectious dose and can survive in the environment, environmental contamination with E coli O157 may be an important public health problem. 5,6 Outbreaks have been linked to contamination of surfaces regularly touched by animals, such as the soil of pastures or railings in petting zoos. 7-9 County fairs are popular throughout the United States. 10 Because fairs bring animals and humans into close contact, they are increasingly recognized as a setting for E coli O157 outbreaks. 11 Such outbreaks often affect multiple communities because fairs attract large numbers of individuals, particularly children, and person-toperson transmission may occur after a fair has ended. We describe an investigation of a fair-associated E coli O157 outbreak in which epidemiological and microbiological studies document that infections can be Author Affiliations are listed at the end of this article.

Location of the double-bond position of monounsaturated fatty acids in Campylobacter cryaerophila was accomplished with combined gas chromatography-mass spectrometry analysis of dimethyl disulfide (DMDS) derivatives. The monoenoic fatty acids from whole bacterial celis were converted to methyl esters and then to DMDS adducts and analyzed by capillary gas chromatography-mass spectrometry. The mass spectra of DMDS adducts gave an easily recognizable molecular ion (M+) and two major diagnostic ions attributable to fragmentation between the two CH3S groups located at the original site of unsaturation. Two previously unidentified acids that distinguish C. cryaerophila from other bacteria were identified as C14:lw7 and C,6:,w7 from their mass spectral fragmentation patterns. Resolution of cis and trans isomers by capillary column gas chromatography permitted assignment of the trans isomer to the C16: 1w7 acid.

Between 23 June and 15 July 1994, 21 cases (19 primary and 2 secondary) of Escherichia coli O157:H7 infection were identified in the Bethel, Connecticut, area. Three pulsed-field gel electrophoresis (PFGE) patterns from 15 isolates (I, n = 13; II, n = 2; and III, n = 1) were observed. A case-control study that excluded secondary cases and patients with PFGE II and III patterns (n = 16) demonstrated that consumption of food from one supermarket was associated with illness (15/16 cases vs. 31/47 geographically matched controls, odds ratio [OR] undefined, lower 95% confidence interval OR = 1.45, P = .018). No one food was associated with illness. Inspection of the supermarket revealed deficiencies in hygiene and meat handling practices. The 2 cases with PFGE II ate raw beef and raw lamb from a second supermarket. These outbreaks demonstrate the value of PFGE in supporting epidemiologic investigations and the potential for outbreaks arising from retail outlets.

It is now established that two species of Bartonella, namely, Bartonella henselae and B. quintana, cause bacillary angiomatosis in human immunodeficiency virus-infected patients. In addition, B. henselae causes cat scratch disease and B. quintana, B. henselae, andB. elizabethae can cause bacteremia and endocarditis in immunocompetent persons. We have developed a PCR-restriction fragment length polymorphism-based assay for direct detection and identification to species level of Bartonella in clinical specimens. This is accomplished by PCR amplification of Bartonella DNA using primers derived from conserved regions of the gene carrying the 16S ribosomal DNA, followed by restriction analysis usingDdeI and MseI restriction endonucleases. We amplified a Bartonella genus-specific 296-bp fragment from 25 clinical samples obtained from 25 different individuals. Restriction analysis of amplicons showed that identical patterns were seen from digestion of B. henselae and B. quintanaamplicons with DdeI, whereas a different unique pattern was seen by using the same enzyme with B. vinsonii and B. elizabethae. With MseI digestion, B. henselae and B. vinsonii gave nearly identical patterns while B. quintana and B. elizabethaegave a different pattern. By combining the restriction analysis data generated with MseI and DdeI, unique “signature” restriction patterns characteristic for each species were obtained. These patterns were useful in identifying theBartonella species associated with each tissue specimen.

The isoprenoid quinone contents of Campylobacter cryaerophila, C. cinaedi, C. fennelliae, C. hyointestinalis, C. pylori, and "C. upsaliensis" were determined by reverse-phase thin-layer and high-performance liquid chromatography. Ail six of these recently named Campylobacter species contained menaquinone-6 (MK-6), but only C. hyointestinalis and "C. upsaliensis" contained 2,[5 or 8]-dimethyl-3-farnesyl-farnesyl-1,4-naphthoquinone (*MK-6), a previously described novel menaquinone of the Campylobacter genus. C. cryaerophila, C. cinaedi, C.fennelliae, and C. pylori contained an unidentified quinone (Un-MK-6) with a molecular weight of 580 and a base peak ion of mle = 225 by mass spectrometry but with chromatographic properties different from those of MK-6. *MK-6 and Un-MK-6 are important chemotaxonomic markers of Campylobacter and Campylobacter-like organisms.