Previous Article | Next Article 
Journal of Clinical Microbiology, March 1999, p. 873-874, Vol. 37, No. 3
Research Sciences Department, U.S. Naval
Medical Research Unit No. 3, Cairo, Egypt,1
and
SBL Vaccin AB, S-105 21 Stockholm,
Sweden2
Received 10 August 1998/Returned for modification 21 October
1998/Accepted 8 December 1998
In a population-based study of diarrhea in rural, northern Egypt,
60 Shigella flexneri strains were identified, of which 10 could not be definitively serotyped. Serological analysis with commercial reagents suggested that they were serotype 1, but the strains failed to react with subserotype 1a- or 1b-specific antibodies. All 10 strains reacted with MASF 1c, a monoclonal antibody specific for
a provisional S. flexneri subserotype, 1c, first identified in Bangladesh and not previously detected outside of that region. Our
results show that S. flexneri subserotype 1c is not unique to Bangladesh and that the inability to detect it may reflect both the
limited use of suitable screening methods and the rarity of this subserotype.
Shigella spp. are a major
bacterial cause of diarrhea, and their sole reservoir appears to be
humans (reviewed in reference 5). Serological
analysis of Shigella has long been used to characterize
isolates for epidemiological and bacteriological purposes (1, 8,
9). Within this genus there are four recognized serogroups
(species): A (S. dysenteriae), B (S. flexneri), C
(S. boydii), and D (S. sonnei) (1, 6).
S. flexneri is further subdivided into eight serotypes In a community-based study conducted from 1991 to 1994 that
investigated the bacterial causes of diarrhea in rural, northern Egypt,
60 S. flexneri strains were identified (11).
Rectal or fecal swabs collected from individuals with diarrhea were
inoculated into Cary-Blair transport medium and stored at 4°C for no
more than 4 days prior to laboratory analysis. Specimens were cultured on Shigella-Salmonella, Hektoen-Enteric, xylose lysine
desoxycholate (XLD), and MacConkey agars (Difco Laboratories, Detroit,
Mich.). S. flexneri was preliminarily identified by Gram
stain, colony morphology, lactose fermentation, and motility, as well
as by results of general biochemical tests (6). All primary
isolates appeared as translucent white colonies on MacConkey agar that were nonmotile and nonlactose fermenting. They showed alkaline-acid (K/A) reactions on either triple sugar-iron agar or Kliger's iron agar
and variable indole degradation, and were negative for both lysine and
ornithine decarboxylation. Confirmatory identifications were performed
with API-20E test kits used according to the instructions of the
manufacturer (Bio-Merieux Vitek Inc., Hazelwood, Mo.). Serogroups and
serotypes were determined by visual inspection of slide agglutination
assays, with commercial antisera used as described by the manufacturer
(Difco Laboratories) (10). Briefly, strains were subcultured
on tryptic soy agar (Difco) and tested for agglutination on glass
slides. Slides were divided into two sections with a wax pencil. A drop
(~20 µl) of 0.85% NaCl solution was placed in one section for use
as a negative control, and a drop of the appropriate antiserum was
placed in the other section. By using a sterile inoculation loop, a
portion of the culture was emulsified with the NaCl solution. This
process was repeated with the section of the slide containing the
antiserum. The slide was then gently rocked, and relative agglutination
was scored after 60 s according to the following scale: ++++,
100% agglutination of the cells; +++, Of the 60 S. flexneri strains identified, 10 could not be
definitively serotyped with commercial reagents. These serologically atypical strains displayed conflicting agglutination patterns, reacting
strongly with serotype 1-specific antisera but also weakly with
serotype 4-specific antisera. These equivocal results may reflect the
limitations of available commercial antibody reagents to reliably
detect the full diversity of serologic variants of S. flexneri (8, 10).
In light of these contradictory results a panel of 10 mouse and rat
monoclonal antibodies specific for the different type- and
group-specific O-antigenic determinants of S. flexneri
lipopolysaccharide was used in the slide agglutination assay for the
further serological analysis of these 10 strains (Table
1) (2-4). Each strain reacted strongly with the serogroup B-specific antibody, MASF B, confirming that all were S. flexneri. Each strain reacted strongly with
the serotype 4-specific antibody, MASF IV-2, but not with the type 1-specific antibody, MASF I, suggesting that all were serotype 4. However, none of the 10 strains agglutinated with the MASF reagents in
a pattern specific for subserotypes 4a and 4b or for subserotypes 1a
and 1b. Since a similar pattern of reactivity had been reported for the
S. flexneri strain Y400 of the provisional subserotype, 1c
(4, 4a, 15), we tested the 10 S. flexneri strains
for reactivity with MASF 1c, a monoclonal antibody specific for this
provisional subserotype (4a). All of these strains reacted
strongly with the MASF 1c antibody (Table
2).
0095-1137/99/$00.00+0
Identification of Shigella flexneri
Subserotype 1c in Rural Egypt
ABSTRACT
Top
Abstract
Text
References
TEXT
Top
Abstract
Text
References
1,
2, 3, 4, 5, 6, X, and Ywith eleven subserotypes1a, 1b, 1c, 2a, 2b,
3a, 3b, 4a, 4b, 5a, and 5b (4, 7). This typing scheme
exploits the polysaccharide O antigen found on the cellular surface
(12-14).
75% agglutination; ++, 50%
agglutination; +, <50% agglutination; 
, no agglutination detected.
A strain was considered positive if its relative agglutination was +++ or greater.
TABLE 1.
Key for S. flexneri subserotyping using the
MASF panela
TABLE 2.
Serological characteristics of 10 atypical S. flexneri strains from Egypt tested with the
MASF panela
Based on our results, these 10 strains belong to the provisional 1c subserotype, first described in Bangladesh (4, 15) in the late 1980s and not previously detected outside of that region. While the clinical and epidemiological significance of this observation remains unclear, our results indicate that this subserotype is not restricted to Bangladesh. We suspect that the failure to detect S. flexneri subserotype 1c in other regions may reflect both the limited use of appropriate screening methods and the rarity of this subserotype. In light of our findings, we recommend that reference laboratories performing serological analysis of S. flexneri consider expanding current screening methods to include detection of subserotype 1c, particularly for those isolates which give equivocal results.
| |
ACKNOWLEDGMENTS |
|---|
This research was supported by the U.S. Naval Medical Research and Development Command (work unit no. 00101.EDX.3413 and 00101.HDX.3414).
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: c/o Commanding Officer, U.S. Naval Medical Research Unit No. 3, PSC 452, Box 5000, FPO AE 09835-0007. Phone: 20/2 284 1381. Fax: 20/2 284 1382. E-mail: boushrah{at}namru3.navy.mil.
Present address: Centers for Disease Control and Prevention,
Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333.
| |
REFERENCES |
|---|
|
Top
Abstract
Text
References
|
|---|
| 1. | Boyd, J. S. K. 1938. The antigenic structure of the mannitol fermenting group of dysentery bacilli. J. Hyg. 38:477-499. |
| 2. |
Carlin, N. I. A., and A. A. Lindberg.
1986.
Monoclonal antibodies specific for Shigella flexneri lipopolysaccharides: clones binding to type I and type III:6,7,8 antigens, group 6 antigen, and a core epitope.
Infect. Immun.
53:103-109 |
| 3. |
Carlin, N. I. A., and A. A. Lindberg.
1987.
Monoclonal antibodies specific for Shigella flexneri lipopolysaccharides: clones binding to type IV, V, and VI antigens, group 3,4 antigen, and an epitope common to all Shigella flexneri and Shigella dysenteriae type 1 strains.
Infect. Immun.
55:1412-1420 |
| 4. |
Carlin, N. I. A.,
M. Rahman,
D. A. Sack,
A. Zaman,
B. Kay, and A. A. Lindberg.
1989.
Use of monoclonal antibodies to type Shigella flexneri in Bangladesh.
J. Clin. Microbiol.
27:1163-1166 |
| 4a. | Carlin, N. I. A. Unpublished results. |
| 5. | DuPont, H. L. 1988. Shigella. Infect. Dis. Clin. N. Am. 2:599-605[Medline]. |
| 6. | Ewing, W. H. 1986. Edwards and Ewing's identification of Enterobacteriaceae, p. 169-181. Elsevier Science Publishing Co., Inc., New York, N.Y. |
| 7. |
Ewing, W. H., and K. P. Carpenter.
1966.
Recommended designations for the subserotypes of Shigella flexneri.
Int. J. Syst. Bacteriol.
16:145-149 |
| 8. | Grinberg, L. D. 1967. Fimbrial antigens of S. flexneri bacteria and the methods of their serological study. I. J. Hyg. Epidemiol. Microbiol. Immunol. 11:451-458. |
| 9. | Grinberg, L. D., and M. A. Gordon. 1971. Further study of fimbrial antigens in Enterobacteriaceae. III. Distribution of the fimbrial phase in the genus Shigella. J. Hyg. Epidemiol. Microbiol. Immunol. 15:293-297[Medline]. |
| 10. | Lefebvre, J., F. Gosselin, J. Ismail, M. Lorange, H. Lior, and D. Woodward. 1995. Evaluation of commercial antisera for Shigella serogrouping. J. Clin. Microbiol. 33:1997-2001[Abstract]. |
| 11. | Oyofo, B. A., S. H. El-Etr, M. O. Wasfy, L. F. Peruski, Jr., B. A. Kay, M. Mansour, J. R. Campbell, A.-M. Svennerholm, A. M. Churilla, and J. R. Murphy. 1995. Colonization factors of enterotoxigenic E. coli (ETEC) from residents of northern Egypt. Microbiol. Res. 150:1-8. |
| 12. | Seltmann, G. 1972. Antigen structure of Shigellae. Chemical basis of Shigella flexneri antigens. Z. Allg. Mikrobiol. 12:497-520[Medline]. |
| 13. |
Simmons, D. A. R.
1971.
Immunochemistry of Shigella flexneri O-antigens: a study of structural and genetic aspects of the biosynthesis of cell-surface antigens.
Bacteriol. Rev.
35:117-148 |
| 14. |
Simmons, D. A., and E. Romanowska.
1987.
Structure and biology of Shigella flexneri O antigens.
J. Med. Microbiol.
23:289-302 |
| 15. | Wehler, T., and N. I. Carlin. 1988. Structural and immunochemical studies of the lipopolysaccharide from a new provisional serotype of Shigella flexneri. Eur. J. Biochem. 176:471-476[Medline]. |
Journal of Clinical Microbiology, March 1999, p. 873-874, Vol. 37, No. 3
0095-1137/99/$00.00+0
This article has been cited by other articles:
-
Farshad, S., Sheikhi, R., Japoni, A., Basiri, E., Alborzi, A.
(2006). Characterization of Shigella Strains in Iran by Plasmid Profile Analysis and PCR Amplification of ipa Genes.. J. Clin. Microbiol.
44: 2879-2883
[Abstract] [Full Text] -
Talukder, K. A., Islam, Z., Aminul Islam, M., Dutta, D. K., Safa, A., Ansaruzzaman, M., Faruque, A. S. G., Shahed, S. N., Nair, G. B., Sack, D. A.
(2003). Phenotypic and Genotypic Characterization of Provisional Serotype Shigella flexneri 1c and Clonal Relationships with 1a and 1b Strains Isolated in Bangladesh. J. Clin. Microbiol.
41: 110-117
[Abstract] [Full Text] -
Talukder, K. A., Islam, M. A., Dutta, D. K., Hassan, F., Safa, A., Nair, G. B., Sack, D. A.
(2002). Phenotypic and Genotypic Characterization of Serologically Atypical Strains of Shigella flexneri Type 4 Isolated in Dhaka, Bangladesh. J. Clin. Microbiol.
40: 2490-2497
[Abstract] [Full Text] -
Talukder, K. A., Dutta, D. K., Safa, A., Ansaruzzaman, M., Hassan, F., Alam, K., Islam, K. M. N., Carlin, N. I. A., Nair, G. B., Sack, D. A.
(2001). Altering Trends in the Dominance of Shigella flexneri Serotypes and Emergence of Serologically Atypical S. flexneri Strains in Dhaka, Bangladesh. J. Clin. Microbiol.
39: 3757-3759
[Abstract] [Full Text]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»