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Infection and Immunity, June 2002, p. 3290-3294, Vol. 70, No. 6
0019-9567/02/$04.00+0 DOI: 10.1128/IAI.70.6.3290-3294.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Characterization of the spv Locus in Salmonella enterica Serovar Arizona
Stephen J. Libby,1 Marc Lesnick,2 Patricia Hasegawa,2 Michael Kurth,2,
Christopher Belcher,2,
Joshua Fierer,2,3,4 and Donald G. Guiney2*
Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615the,1
Departments of Medicine,2
Pathology, School of Medicine, University of California at San Diego, La Jolla, California 92093,3
Veterans Affairs Healthcare System, San Diego, California 921614
Received 31 October 2001/
Returned for modification 16 January 2002/
Accepted 28 February 2002

ABSTRACT
Salmonella enterica serovar Arizona (
S. enterica subspecies
IIIa) is a common
Salmonella isolate from reptiles and can cause
serious systemic disease in humans. The
spv virulence locus,
found on large plasmids in
Salmonella subspecies I serovars
associated with severe infections, was confirmed to be located
on the chromosome of serovar Arizona. Sequence analysis revealed
that the serovar Arizona
spv locus contains homologues of
spvRABC but lacks the
spvD gene and contains a frameshift in
spvA, resulting
in a different C terminus. The SpvR protein functions as a transcriptional
activator for the
spvA promoter, and SpvB and SpvC are highly
conserved. The analysis supports the proposal that the chromosomal
spv sequence more closely corresponds to the ancestral locus
acquired during evolution of
S. enterica, with plasmid acquisition
of
spv genes in the subspecies I strains involving addition
of
spvD and polymorphisms in
spvA.

TEXT
Salmonella enterica serovar Arizona (
S. enterica subspecies
IIIa) is naturally found in reptiles but also causes outbreaks
of salmonellosis in turkeys and sheep and can produce both enteritis
and serious disseminated disease in humans (
6,
7,
18,
20,
28,
35). Reptiles frequently harbor serovar Arizona as a commensal
organism, but pathological responses to infection have also
been reported, and the bacteria seem capable of vertical transmission
through infection of oviduct tissue (
7). Many human infections
can be traced to contact with reptiles or ingestion of various
reptile products, particularly from rattlesnakes (
3,
27,
29).
Patients with depressed CD4-mediated T-cell immunity, such as
those infected with human immunodeficiency virus, are particularly
susceptible to the development of serious and persistent systemic
infections with serovar Arizona after ingestion of contaminated
products.
The virulence determinants of serovar Arizona are poorly understood. However, the ability of this organism to cause extraintestinal infection in both reptiles and humans is consistent with recent evidence that this subspecies contains the spv virulence gene locus (5). The spv genes have been extensively studied in serovars of the S. enterica subspecies I lineage, including serovars Typhimurium, Dublin, Enteritidis, Choleraesuis, and Gallinarum-Pullorum (15, 16, 17). The spv loci in these strains are highly homologous, consisting of the transcriptional regulator spvR and four structural genes, spvABCD. The SpvB protein is an ADP ribosyltransferase that modifies actin and destabilizes the cytoskeleton of infected cells (22, 34) and appears to be primarily responsible for the spv virulence phenotype (22). In serovar Dublin, the spv genes increase the severity of both intestinal and systemic disease, while, in other serovars examined, a consistent enhancement of systemic virulence has been reported (1, 9, 16, 24). Furthermore, extraintestinal infections caused by serovar Typhimurium in humans are significantly associated with strains that carry the spv locus (11).
Within the genus Salmonella, the spv locus exhibits a distinct phylogenetic distribution. The spv genes are absent from Salmonella bongori and are present in subspecies I, II, IIIa, IV, and VII of S. enterica (5). Within subspecies I, the lineage responsible for the vast majority of human salmonellosis cases, the spv genes are located exclusively on large virulence plasmids present in certain serovars. In contrast, subspecies II, IIIa, IV and VII appear to carry spv genes in the chromosome (5). Moreover, sequence analysis of a portion of the spvA gene reveals polymorphisms consisting of insertions and deletions, as well as base substitutions, among the subspecies (5). Based on the demonstrated importance of serovar Arizona as a human pathogen, we investigated the structure of the entire spv locus in this subspecies.
A recent report concluded (on the basis of a pulsed-field electrophoresis analysis) that the spv genes of serovar Arizona were located in the chromosome (5). However, this study did not rule out the possibility that the spv locus was carried on a very large plasmid, since the patterns of spv hybridization were similar for whole-cell DNA run either undigested or digested with I-CeuI. To establish the chromosomal location of the spv locus in serovar Arizona, we used transverse alternating-field electrophoresis (TAFE) to resolve very large DNA molecules (14). Cells of serovar Arizona strains 2323, 2334, and 2335, as well as serovar Dublin Lane, were lysed in agarose plugs, run on TAFE, transferred to a nylon membrane, and hybridized to a 4-kb EcoRI probe fragment containing the spvA, -B, and -C genes from serovar Dublin (30). The result, shown in Fig. 1, demonstrates the absence of extrachromosomal DNA that hybridizes to the spv probe in lanes containing the undigested whole-cell DNA of the serovar Arizona strains, while a strongly hybridizing band representing the pSDL2 plasmid is seen in the DNA containing the spv locus from serovar Dublin. This result is consistent with our inability to demonstrate an extrachromosomal locus of the spv genes (data not shown) using DNA isolation techniques (8, 19, 26) specifically designed to detect large plasmid molecules.
Further evidence that the
spv locus is located in the serovar
Arizona chromosome was obtained by digesting the whole-cell
DNA with I-
CeuI, an enzyme that recognizes an extended sequence
within the
rrl rRNA genes of
Salmonella strains (
25). Figure
2 shows the result of hybridizing the
spv probe to I-
CeuI digests
of serovar Dublin and serovar Arizona strains 2323 and 2334,
resolved by TAFE. Both serovar Arizona strains contain a large
I-
CeuI fragment, greater than 1 Mb in size, that hybridizes
to the
spv probe. These results prove that the
spv genes in
serovar Arizona strains are located on a very large I-
CeuI fragment
of the chromosome.
For further analysis, the
spv locus from a recent clinical isolate,
serovar Arizona strain 5705A, was cloned on cosmid pLAFR2 (
23)
by partial
Sau3A digestion of whole-cell DNA. Two clones containing
the
spv region were identified by colony hybridization. Both
cosmids contained common 6.5- and 2.2-kb
EcoRI fragments that
hybridized to the
spvABC and
spvR probes, respectively. These
fragments were sequenced, and the results are shown in Fig.
3. Close homology to the serovar Dublin pSDL2
spv sequence (
21)
was found in a region from serovar Arizona extending 515 bp
upstream from the
spvR start codon to a site only 3 bp downstream
from the
spvC stop codon (96% conserved residues overall). The
spvD gene is absent from the serovar Arizona sequence. Southern
blot hybridization of whole-cell DNA demonstrated that the
spvD gene is missing from the serovar Arizona genome (data not shown).
The flanking regions upstream and downstream of the serovar
Arizona
spv locus do not show significant extended homology
with any DNA sequences in the database or with the
S. enterica serovar Typhi sequence. The translated DNA sequence downstream
from the serovar Arizona
spvC gene shows fragments of open reading
frames related to transposases and a resolvase, suggesting that
this region represents a degenerated insertion element.
The regulatory regions of the
spvR and
spvA promoters are highly
conserved between the subspecies I sequences and serovar Arizona.
The transcriptional activator SpvR binds to well-defined sequences
upstream of the -25 position in both promoters, and promoter
mutations within these sites have been isolated and characterized
in serovar Dublin and serovar Typhimurium (
12,
13,
32). There
is a 1-bp difference between the serovar Typhimurium and serovar
Dublin
spvR promoter sequences, and serovar Arizona matches
the serovar Typhimurium sequence. In the
spvA regulatory region,
the serovar Typhimurium and serovar Dublin sequences are identical,
but serovar Arizona has an A-to-G change at -13 and two A-to-G
differences in the promoter-proximal end of the SpvR binding
region (
12). The significance of these changes remains to be
established, since none of them corresponds to the promoter-defective
mutations previously reported for serovar Dublin and serovar
Typhimurium (
13,
32).
The amino acid sequences of SpvR from five different subspecies I serovars differ at only 4 positions out of 297 residues. At each of these, the serovar Arizona sequence conforms to the consensus of the subspecies I sequences. However, serovar Arizona differs from the subspecies I serovars at 5 other positions which are exactly conserved in subspecies I strains. Therefore, we determined whether the SpvR protein from serovar Arizona was able to activate transcription from the spvA promoter of serovar Dublin. The 2.2-kb EcoRI fragment containing the serovar Arizona spvR was cloned on pBluescript II SK(+) and was transformed into Escherichia coli TB1 containing the spvA promoter reporter plasmid pFF26 (10). As a control, the 6.5-kb fragment carrying the serovar Arizona spvABC region was also cloned into pBluescript. The result of a representative ß-galactosidase assay is shown in Fig. 4 and demonstrates that SpvR from serovar Arizona (encoded by the 2.2-kb fragment) can activate the serovar Dublin spvA promoter on pFF26. Controls using the 6.5-kb fragment gave background levels of spvA promoter activation.
The sequence of an internal fragment of the serovar Arizona
SpvA protein has been previously reported as containing an additional
33-amino-acid segment not present in the SpvA proteins of subspecies
I strains (
5). Our sequence of the complete SpvA protein from
serovar Arizona reveals a frameshift in the C-terminal region
resulting in a different protein sequence and slightly longer
C terminus than in the subspecies I SpvA proteins. Interestingly,
the
Salmonella SpvA proteins share significant homology with
the TccA component of an insecticidal toxin from
Photorhabdus luminescens (
4). Figure
5 shows a multiple alignment of the
SpvA proteins from serovar Dublin and serovar Arizona with TccA.
The serovar Arizona SpvA protein and TccA share two key sequence
features that are different from SpvA from serovar Dublin. The
33-amino-acid segment present in serovar Arizona (residues 175
to 209) is also found in TccA but is missing from serovar Dublin.
Likewise, the C-terminal frameshift change in serovar Arizona
is also present in TccA, following residue 323. This comparison
suggests that the common ancestor of TccA and the SpvA proteins
also contained these two sequence features and that the deletion
and frameshift mutations arose during evolution of the serovar
Dublin and other subspecies I
spvA genes.
Both SpvB and SpvC are highly conserved between serovar Arizona
and the corresponding subspecies I virulence plasmid genes.
The serovar Arizona SpvB protein differs at only 20 of its 593
residues from the consensus subspecies I sequence. Two of these
are additional prolines in the polyproline bridge that separates
the N-terminal domain from the C-terminal ADP-ribosylating domain
(
22). SpvC from serovar Arizona contains 6 differences out of
241 residues. As noted above for SpvR and SpvA, SpvB and SpvC
from the subspecies I plasmids are more closely related to each
other than to serovar Arizona, a finding consistent with the
ancestral status of the serovar Arizona locus.
We have provided definitive evidence that the serovar Arizona spv locus is in the chromosome. Sequence analysis of the flanking regions comprising 370 bp upstream from the region of homology to the subspecies I strains and about 2 kb downstream do not reveal extended homologies with available Salmonella sequences, suggesting that there may be an extended region around the serovar Arizona locus that is not present in the chromosomes of Salmonella strains of the subspecies I lineage. We propose that the spv locus represents a pathogenicity island in serovar Arizona.
Within the spv region, the most significant differences between serovar Arizona and the subspecies I strains are the absence of spvD and polymorphisms in spvA. Earlier studies have implicated only a minor virulence role for spvD in murine infections (31). However, it is possible that this gene could have a function in other hosts or environments. Based primarily on polymorphisms in the spvA locus, Boyd and Hartl (5) proposed that the chromosomal serovar Arizona spv sequence corresponds more closely than the subspecies I plasmid sequence to the ancestral locus that was acquired by the S. enterica lineage after divergence from S. bongori. Subspecies I, IIIb, VI, and VII and strains of IV would then have lost their chromosomal spv locus, to be regained on a family of virulence plasmids by certain serovars of subspecies I. Our results are consistent with this model, given the additional conditions that spvD was also acquired by the plasmid locus and that spvA suffered a frameshift mutation in addition to the previously reported central in-frame deletion (5) during the evolution of the plasmid spv genes. Comparison of the serovar Arizona SpvA sequence with TccA of P. luminescens demonstrates that the common ancestor contained both the central region and the original C-terminal reading frame. This model suggests that spvA had a role in the ancestral lineage and perhaps in present-day serovar Arizona strains but either tolerates extensive polymorphism or is dispensable in plasmid-encoded loci. The latter possibility is supported by mutational analysis indicating that spvA is not required for virulence in mice (31).
The lack of a feasible animal model for serovar Arizona virulence precludes a definitive analysis of the role of the spv genes in this subspecies. However, several indirect lines of evidence support the functional significance of the spv locus that we have characterized. The SpvR, SpvB, and SpvC genes are all intact and highly conserved relative to the subspecies I counterparts. We also demonstrated that the serovar Arizona SpvR protein is a functional activator of the spvA promoter. Finally, serovar Arizona is associated with the same severe systemic clinical disease as the spv-containing subspecies I strains serovar Typhimurium, serovar Enteritidis, serovar Dublin, and serovar Choleraesuis (3, 20, 27, 28, 29). The key pathogenic mechanism appears to involve the induction of cytotoxicity due to actin depolymerization by the SpvB protein, enhancing systemic growth of the organism (22). This property of the spv locus may have enabled certain Salmonella lineages to adapt to particular ecological niches. A major role of the spv genes could be to promote transmission of the organism through systemic spread and localization in key target tissues. Serovar Dublin is host adapted to cattle, and colonization of the udder, with intermittent shedding in milk, appears to be a major mechanism for long-term persistence of the organism in herds (33). In nature, serovar Arizona infection of reptiles is widespread but often is present without manifestation of disease. Systemic spread with transovarial passage of serovar Arizona in snakes has been postulated as a major mechanism of transmission (7).

ACKNOWLEDGMENTS
This work was supported by grants from the National Institutes
of Health (AI-32178 and DK35108). Michael Kurth was the recipient
of a Science Teacher Summer Research Fellowship from the American
Society for Clinical Investigation.

FOOTNOTES
* Corresponding author. Mailing address: University of California, 9500 Gilman Dr., La Jolla, CA 92093-0640. Phone: (858) 534-6030. Fax: (858) 534-6020. E-mail:
dguiney{at}ucsd.edu.

Editor: J. T. Barbieri
Present address: Department of Biology, Poway High School, Poway, CA 92064. 
Present address: Department of Pediatrics, Stanford University, Stanford, CA 94305. 

REFERENCES
1
- Barrow, P. A., J. M. Simpson, M. A. Lovell, and M. M. Binns. 1987. Contribution of Salmonella gallinarum large plasmid toward virulence in fowl typhoid. Infect. Immun. 55:388-392.[Abstract/Free Full Text]
2
- Beninger, P. R., G. Chikami, K. Tanabe, C. Roudier, J. Fierer, and D. G. Guiney. 1988. Physical and genetic mapping of the Salmonella dublin virulence plasmid pSDL2. Relationship to plasmids from other Salmonella strains. J. Clin. Investig. 81:1341-1347.
3
- Bhatt, B. D., M. J. Zuckerman, J. A. Foland, S. M. Polly, and R. K. Marwah. 1989. Disseminated Salmonella arizona infection associated with rattlesnake meat ingestion. Am. J. Gastroenterol. 84:433-435.[Medline]
4
- Bowen, D., T. A. Rocheleau, M. Blackburn, O. Andreer, E. Golubera, R. Bhartia, and R. H. ffrench-Constant. 1998. Insecticidal toxins from the bacterium Photorhabdus luminescens. Science 280:2129-2132.[Abstract/Free Full Text]
5
- Boyd, E. F., and D. L. Hartl. 1998. Salmonella virulence plasmid: modular acquisition of the spv virulence region by an F-plasmid in Salmonella enterica subspecies I and insertion into the chromosome of subspecies II, IIIa, IV and VII isolates. Genetics 149:1183-1190.[Abstract/Free Full Text]
6
- Caldwell, M. E., and D. L. Ryerson. 1939. Salmonellosis in certain reptiles. J. Infect. Dis. 65:242-245.
7
- Chiodini, R. J. 1982. Transovarian passage, visceral distribution, and pathogenicity of salmonella in snakes. Infect. Immun. 36:710-713.[Abstract/Free Full Text]
8
- Currier, T. C., and E. W. Nester. 1976. Isolation of covalently closed circular DNA of high molecular weight from bacteria. Anal. Biochem. 76:431-444.[CrossRef][Medline]
9
- Danbara, H., R. Moriguchi, S. Suseke, Y. Tamura, M. Kijima, K. Oishi, H. Matsui, A. Abe, and M. Kakamura. 1992. Effect of 50 kilobase-plasmid, pKD5C50, of Salmonella choleraesuis RF-1 strain on pig septicemia. J. Vet. Med. Sci. 54:1175-1178.[Medline]
10
- Fang, F. C., M. Krause, C. Roudier, J. Fierer, and D. G. Guiney. 1991. Growth regulation of a Salmonella plasmid gene essential for virulence. J. Bacteriol. 173:6783-6789.[Abstract/Free Full Text]
11
- Fierer, J., M. Krause, R. Tauxe, and D. Guiney. 1992. Salmonella typhimurium bacteremia: association with the virulence plasmid. J. Infect. Dis. 166:639-642.[Medline]
12
- Grob, P., and D. G. Guiney. 1996. In vitro binding of the Salmonella dublin virulence plasmid regulatory protein SpvR to the promoter regions of spvA and spvR. J. Bacteriol. 178:1813-1820.[Abstract/Free Full Text]
13
- Grob, P., D. Kahn, and D. G. Guiney. 1997. Mutational characterization of promoter regions recognized by the Salmonella dublin virulence plasmid regulatory protein SpvR. J. Bacteriol. 179:5398-5406.[Abstract/Free Full Text]
14
- Guiney, D. G., and P. Hasegawa. 1992. Transfer of conjugal elements in oral black pigmented Bacteroides (Prevotella) spp. involves DNA rearrangements. J. Bacteriol. 174:4853-4855.[Abstract/Free Full Text]
15
- Guiney, D. G., F. C. Fang, M. Krause, and S. Libby. 1994. Plasmid-mediated virulence genes in non-typhoid Salmonella serovars. FEMS Microbiol. Lett. 124:1-10.[CrossRef][Medline]
16
- Guiney, D. G., F. C. Fang, M. Krause, S. Libby, N. A. Buchmeier, and J. Fierer. 1995. Biology and clinical significance of virulence plasmids in Salmonella serovars. Clin. Infect. Dis. 21(Suppl. 2):S146-S151.
17
- Gulig, P. A., H. Danbara, D. G. Guiney, A. J. Lax, F. Norel, and M. Rhen. 1993. Molecular analysis of spv virulence genes of the Salmonella virulence plasmids. Mol. Microbiol. 7:825-830.[Medline]
18
- Hall, M. L. M., and B. Rowe. 1992. Salmonella arizona in the United Kingdom from 1966-1990. Epidemiol. Infect. 108:59-65.[Medline]
19
- Hansen, J. B., and R. H. Olsen. 1978. Isolation of large bacterial plasmids and characterization of the P2 incompatibility group plasmids pMG1 and pMG5. J. Bacteriol. 135:227-238.[Abstract/Free Full Text]
20
- Johnson, R. H., L. I. Lutwick, G. A. Huntley, and K. L. Vosti. 1976. Arizona hinshawii infections. Ann. Intern. Med. 85:587-592.
21
- Krause, M., C. Roudier, J. Fierer, J. Harwood, and D. Guiney. 1991. Molecular analysis of the virulence locus of the Salmonella dublin plasmid pSDL2. Mol. Microbiol. 5:307-316.[CrossRef][Medline]
22
- Lesnick, M. L., N. E. Reiner, J. Fierer, and D. G. Guiney. 2001. The Salmonella spvB virulence gene encodes an enzyme that ADP-ribosylates actin and destabilizes the cytoskeleton of eukaryotic cells. Mol. Microbiol. 39:1464-1470.[CrossRef][Medline]
23
- Libby, S. J., W. Goebel, A. Ludwig, F. Bowe, N. Buchmeier, G. Songer, F. Fang, D. Guiney, and F. Heffron. 1994. A cytolysin from Salmonella typhimurium is required for survival in macrophages. Proc. Natl. Acad. Sci. USA 91:489-493.[Abstract/Free Full Text]
24
- Libby, S. J., L. G. Adams, T. A. Ficht, C. Allen, H. A. Whitford, N. A. Buchmeier, S. Bossie, and D. G. Guiney. 1997. The spv genes on the Salmonella dublin virulence plasmid are required for severe enteritis and systemic infection in the natural host. Infect. Immun. 65:1786-1792.[Abstract]
25
- Liu, S.-L., A. Hessel, and K. E. Sanderson. 1993. Genomic mapping with I-Ceu I, an intron-encoded endonuclease specific for genes for ribosomal RNA, in Salmonella spp., Escherichia coli, and other bacteria. Proc. Natl. Acad. Sci. USA 90:6874-6878.[Abstract/Free Full Text]
26
- Meyer, R., D. Figurski, and D. R. Helinski. 1977. Physical and genetic studies with restriction endonucleases on the broad host-range plasmid RK2. Mol. Gen. Genet. 152:129-135.[CrossRef][Medline]
27
- Noskin, G. A., and J. T. Clarke. 1990. Salmonella arizonae bacteremia as the presenting manifestation of human immunodeficiency virus infection following rattlesnake meat ingestion. Rev. Infect. Dis. 12:514-517.[Medline]
28
- Petru, M. A., and D. D. Richman. 1981. Arizona hinshawii infection of an atherosclerotic abdominal aorta. Arch. Intern. Med. 141:537-538.[Abstract/Free Full Text]
29
- Riley, K. B., D. Antoniskis, R. Mavis, and J. M. Leedom. 1988. Rattlesnake capsule-associated Salmonella arizona infections. Arch. Intern. Med. 148:1207-1210.[Abstract/Free Full Text]
30
- Roudier, C., M. Krause, J. Fierer, and D. G. Guiney. 1990. Correlation between the presence of sequences homologous to the vir region of Salmonella dublin plasmid pSDL2 and the virulence of twenty-two Salmonella serotypes in mice. Infect. Immun. 58:1180-1185.[Abstract/Free Full Text]
31
- Roudier, C., J. Fierer, and D. G. Guiney. 1992. Characterization of translation termination mutations in the spv operon of the Salmonella virulence plasmid pSDL2. J. Bacteriol. 174:6418-6423.[Abstract/Free Full Text]
32
- Sheehan, B. J., and C. J. Dorman. 1998. In vitro analysis of the interactions of the LysR-like regulator SpvR with the operator sequences of the spvA and spvR virulence genes of Salmonella typhimurium. Mol. Microbiol. 30:91-105.[CrossRef][Medline]
33
- Smith, B. P., D. G. Oliver, P. Singh, G. Dilling, P. A. Marvin, B. P. Ram, L. S. Jang, N. Sharkov, J. S. Osborn, and K. Jackett. 1989. Detection of Salmonella dublin mammary gland infection in carrier cows, using an enzyme-linked immunosorbent assay for antibody in milk or serum. Am. J. Vet. Res. 50:1352-1360.[Medline]
34
- Tezcan-Merdol, D., T. Nyman, V. Lindberg, F. Haag, F. Koch-Nolte, and M. Rhen. 2001. Actin is ADP-ribosylated by the Salmonella enterica virulence-associated protein SpvB. Mol. Microbiol. 39:606-619.[CrossRef][Medline]
35
- Weiss, S. H., M. J. Blaser, F. P. Paleologo, R. E. Black, A. C. McWhorter, M. A. Ashbery, G. P. Carter, R. A. Feldman, and D. J. Brenner. 1986. Occurrence and distribution of serotypes of the Arizona subgroup of Salmonella strains in the United States from 1967 to 1976. J. Clin. Microbiol. 23:1056-1064.[Abstract/Free Full Text]
Infection and Immunity, June 2002, p. 3290-3294, Vol. 70, No. 6
0019-9567/02/$04.00+0 DOI: 10.1128/IAI.70.6.3290-3294.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
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