Previous Article | Next Article ![]()
Journal of Clinical Microbiology, February 2006, p. 589-591, Vol. 44, No. 2
0095-1137/06/$08.00+0 doi:10.1128/JCM.44.2.589-591.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Division of Geographic Medicine and Infectious Diseases, TuftsNew England Medical Center, Boston, Massachusetts 02111,1 Laboratoire de Parasitologie Mycologie et Laboratoire de Microbiologie Médicale et Moléculaire (EA 562), CHU, et Faculté de Médecine, Dijon,2 Institut de Veille Sanitaire, Saint Maurice,3 DRASS de Bourgogne, CIR Centre Est, Dijon, France4
Received 3 June 2005/ Returned for modification 18 July 2005/ Accepted 19 October 2005
|
|
|---|
|
|
|---|
Previous investigations have identified two major species that infect humans. Cryptosporidium hominis, previously referred to as genotype I (8), is anthroponotic and is almost exclusively confined to human infections (10). In contrast, C. parvum (previously referred to as genotype II) is zoonotic and is able to infect humans and animals. These genotypic distinctions have been confirmed at several loci through restriction fragment length polymorphism (RFLP) and sequence analysis (10). Overall, C. hominis appears to be responsible for more waterborne outbreaks of cryptosporidiosis than C. parvum (12).
Recently, we and others identified a highly polymorphic Cryptosporidium gene, Cpgp40/15 (2, 11, 13, 15). The degree of sequence variation at this locus is far greater than that of any other Cryptosporidium gene described thus far. Since highly polymorphic loci are particularly useful for subgenotyping, analysis of sequence polymorphism at this locus has facilitated the identification of a number of allelic subgroups, particularly among C. hominis isolates (1, 6, 9, 13, 16). It has been shown that the Cpgp40/15 allelic subgroup Ib had a major role in the Milwaukee outbreak (17). Although subgenotypic data from outbreaks in other parts of the world are scarce, two studies from Ireland also found an elevated rate of infection attributed to isolates with the Cpgp40/15 type Ib allele (4).
We previously reported on a waterborne outbreak of cryptosporidiosis in Dracy le Fort in eastern France (3). Briefly, on 20 September 2001, clustered cases of gastroenteritis occurred in the county of Dracy le Fort. Complaints about the quality of the public water supply had been reported during the previous week. Public health authorities declared an outbreak; and a series of three investigations followed: (i) analysis of fecal samples from symptomatic patients, (ii) analysis of water samples collected from the public water supply, and (iii) epidemiologic investigations based on telephone surveys of physicians from the cities served by the same public water system and all households in the city of Dracy le Fort (3).
Analysis of fecal samples showed that the outbreak was polymicrobial. Altogether, 61.2% of the samples were positive for Cryptosporidium DNA by PCR for the Hsp70 and the 18S rRNA genes. Genotyping of the isolates by direct sequencing of the PCR products showed that all isolates were genotype 1 (3). Water samples collected on 20 and 21 September confirmed a bacterial contamination of the public network. Of 56 water samples tested, 15 were positive for Cryptosporidium sp. oocysts, with the maximum oocyst concentration reaching 0.19/liter on 1 October. Samples collected after 3 October were negative for Cryptosporidium spp.
The telephone survey of physicians showed that the outbreak was almost exclusively limited to Dracy le Fort. A retrospective telephone survey reached 387 households; 291 were included in the analysis. It showed that the attack rate increased in children aged 0 to 9 years (P < 0.05) and with the amount of water consumed before 20 September (P < 0.001) (Table 1). The present study was conducted to determine the subgenotypes of isolates from the Dracy le Fort outbreak by PCR-RFLP and sequencing of the Cpgp40/15 locus. Samples from 25 symptomatic patients that tested positive for Cryptosporidium spp. were analyzed to determine which allelic subgroups were associated with the outbreak.
|
View this table: [in a new window] |
TABLE 1. Gastroenteritis attack rates determined from a retrospective telephone survey in the city of Dracy le Fort
|
Cpgp40/15 sequence analysis. The Cpgp40/15 gene was amplified by nested PCR by using the conditions mentioned above and Proofstart Taq polymerase (QIAGEN, Inc., Valencia, Calif.). The secondary PCR products were purified by using a QIAquick kit (QIAGEN) and were sequenced by the dye-terminator method at the Tufts University Core Facility with a Perkin-Elmer ABI 377 sequencer. The nucleotide sequences from this study were compared with each other and with sequences deposited in GenBank by using the Clustal W alignment algorithm in the MegAlign 6.2 program from the Lasergene suite 6.0 of DNASTAR Inc. (Madison, Wis.). Three Cpgp40/15 allelic subgroups were found in the Dracy le Fort outbreak. Of 23 isolates, 21 were type Ib by PCR-RFLP (products were not amplified from two of the original samples). Isolate 7 belonged to the type Id subgroup, while isolate 15, previously identified as genotype I, was found to be type IIa at this locus (Fig. 1). These results were confirmed through sequence analysis. A complete or a partial nucleotide sequence could be obtained from the PCR products of all 21 isolates. The phylogenetic tree in Fig. 2 shows the relationship of the Cpgp40/15 nucleotide sequences of isolates from this study to each other and to those of previously identified representative subgroup Id, Ib, and IIa isolates deposited in GenBank. The sequences of the isolates of type Ib, which was the predominant subtype identified in this study, were almost identical to each other, suggesting that the outbreak may have occurred from a common source.
![]() View larger version (53K): [in a new window] |
FIG. 1. PCR-RFLP analysis of the Cpgp40/15 locus from representative isolates. (A) Secondary PCR amplicons digested with RsaI; (B) secondary PCR amplicons digested with AluI. The first three lanes of both panels show the RFLP profiles for known subgenotype Ib, Id, and IIa Cpgp40/15 sequences previously deposited in GenBank (GenBank accession numbers AF440626, AF440625, and AF114166, respectively), while the last three lanes in each panel show the PCR-RFLP profiles from isolates 5 (a representative type Ib isolate), 7, and 15, respectively. Lane M, markers. Following RsaI digestion, the expected sizes of the PCR products, based on the known sequences of isolates with GenBank accession numbers AF440626 (type Ib), AF440625 (type Id), and AF114166 (type IIa), were 387, 200, 195, 159, and 35 bp for the Ib subtype; 483, 367, 200, and 30 bp for the Id subtype; and 329, 207, 195, 177, and 35 bp for the IIa subtype. Following AluI digestion, the expected sizes of the PCR products were 457, 380, 85, and 56 bp for the Ib subtype; 520, 385, and 175 bp for the Id subtype; and 294, 258, 214, 81, 60, and 36 bp for the IIa subtype.
|
![]() View larger version (23K): [in a new window] |
FIG. 2. Genetic relationship among isolates from the outbreak. The Cpgp40/15 nucleotide sequences from the type Ib, Id, and IIa isolates from the outbreak were aligned with each other and with known Cpgp40/15 subgenotype sequences previously deposited in GenBank (GenBank accession numbers AF440626, AF440625, and AF114166, respectively) by using the Clustal W algorithm in the MegAlign 6.2 program from the Lasergene suite 6.0 of DNASTAR Inc. A phylogenetic tree was constructed from the alignment by using the neighbor-joining algorithm in the MegAlign 6.2 program. The nucleotide substitutions are in hundreds.
|
Nucleotide sequence accession numbers. The Cpgp40/15 sequences from isolates in this study have been deposited in GenBank under accession numbers DQ184508, AY677199, AY677200, and AY702619 to AY702638.
We thank Anne Kane and the Intestinal Microbiology Core of the GRASP Center for reagents and Anne Kane and Roberta O'Connor for careful review of the manuscript.
|
|
|---|
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»