International typing study of toxin A-negative,toxin B-positive Clostridium difficile variants

Clinically important strains of Clostridium difficile that do not produce toxin A but produce toxin B and are cytotoxic (A(-)/B(+)) have been reported from multiple countries. In order to compare the relatedness of these strains, we typed 23 A(-)/B(+) C. difficile isolates from the United Kingdom (6 isolates), Belgium (11 isolates), and the United States (6 isolates) by three well-described typing methods. Restriction endonuclease analysis (REA), PCR ribotyping, and serogrouping differentiated 11, 4, and 3 different strain types, respectively. Twenty-one of the 23 A(-)/B(+) variants had a 1.8-kb truncation of the toxin A gene characteristic of toxinotype VIII strains; 20 of the 21 toxinotype VIII-like strains were PCR type 17. PCR type 17 isolates could be differentiated into two separate strain groups by serogrouping and by REA. REA further discriminated these isolates into eight subgroups (REA types). PCR type 17-serogroup F-REA group CF isolates were recovered from all three countries, and one specific REA type, CF4, was recovered from patients with C. difficile disease in the United Kingdom and the United States. C. difficile A(-)/B(+) variants of apparent clonal origin are widely distributed in Europe and North America.     

Characterization of Streptococcus agalactiae isolates of bovine and human origin by randomly amplified polymorphic DNA analysis

Streptococcus agalactiae is considered one of the major causes of bovine intramammary infections. It is also found in the vaginas of women without any apparent clinical symptoms, but reports of neonatal infections, causing significant morbidity, are relatively frequent. The aim of this study was to evaluate the genetic diversity of S. agalactiae strains isolated from bovine milk and from asymptomatic women in Québec, Canada, by randomly amplified polymorphic DNA (RAPD) analysis. A total of 185 bovine isolates and 38 human isolates were first serotyped for capsular polysaccharide by double diffusion in agarose gel (bovine isolates) and coagglutination (human isolates). Strains were then studied by RAPD using 3 primers, designated OPS11, OPB17, and OPB18, which were selected from 12 primers. Thirty-eight percent of bovine isolates and 82% of human isolates could be serotyped. Prevalent serotypes were type III (28%) for bovine isolates and types V (26%) and III (24%) for human isolates. RAPD results showed that, taken together, all isolates (of bovine and human origin) shared 58% similarity. Ninety-four percent of these isolates were clustered in four groups (I, II, III, and IV) with 70% similarity among them. Three clusters, A (48 isolates), B (14 isolates), and C (32 isolates), with 79 to 80% similarity were identified within group IV, whereas the three other groups did not present any clusters. Despite some clustering of human isolates, relatively high diversity was seen among them. Relatively high heterogeneity was observed with the RAPD profiles, not only for field strains belonging to different serotypes but also for those within a given serotype.     

Ca3 fingerprinting of Candida albicans bloodstream isolates from the United States,Canada, South America,and Europe reveals a European clade

It was previously demonstrated by a cluster analysis that 26 unrelated U.S. isolates of Candida albicans separated into three distinct groups (groups I, II, and III) while South African isolates separated into four distinct groups (groups I, II, III, and SA). To verify the absence or underrepresentation of SA isolates in North America, and to identify which groups are represented in Europe and South America, collections of bloodstream isolates from each geographical locale were analyzed by cluster analyses based on genetic fingerprinting with the Ca3 probe. The results verify that North America is almost devoid of SA isolates (2%). However, the results reveal a new clade, designated group E, relatively specific to Europe. While 26% of a European collection of 46 isolates was composed of group E isolates, only 2% of the 164 North American isolates, 5% of 22 South American isolates, and 1% of 361 South African isolates were composed of group E isolates. The North American collection proved to be the least-diverse collection in regard to group representation. In a comparison of collections from the Northeast, Midwest, and Southwest regions of the United States, Canada, and South America, it was demonstrated that both the U.S. Southwest and the South American collections were devoid of group II isolates. Together these results identify for the first time a European-specific clade and demonstrate clear distinctions in the representations of the five demonstrated clades (groups I, II, III, SA, and E) in different geographical locales.     

Comparison of strain typing results for Clostridium difficile isolates from North America

Accurate strain typing is critical for understanding the changing epidemiology of Clostridium difficile infections. We typed 350 isolates of toxigenic C. difficile from 2008 to 2009 from seven laboratories in the United States and Canada. Typing was performed by PCR-ribotyping, pulsed-field gel electrophoresis (PFGE), and restriction endonuclease analysis (REA) of whole-cell DNA. The Cepheid Xpert C. difficile test for presumptive identification of 027/NAP1/BI isolates was also tested directly on original stool samples. Of 350 isolates, 244 (70%) were known PCR ribotypes, 224 (68%) were 1 of 8 common REA groups, and 187 (54%) were known PFGE types. Eighty-four isolates typed as 027, NAP1, and BI, and 83 of these were identified as presumptive 027/NAP1/BI by Xpert C. difficile. Eight additional isolates were called presumptive 027/NAP1/BI by Xpert C. difficile, of which three were ribotype 027. Five PCR ribotypes contained multiple REA groups, and three North American pulsed-field (NAP) profiles contained both multiple REA groups and PCR ribotypes. There was modest concordance of results among the three methods for C. difficile strains, including the J strain (ribotype 001 and PFGE NAP2), the toxin A-negative 017 strain (PFGE NAP9 and REA type CF), the 078 animal strain (PFGE NAP7 and REA type BK), and type 106 (PFGE NAP11 and REA type DH). PCR-ribotyping, REA, and PFGE provide different but overlapping patterns of strain clustering. Unlike the other methods, the Xpert C. difficile 027/NAP1/BI assay gave results directly from stool specimens, required only 45 min to complete, but was limited to detection of a single strain type.     

International surveillance of bloodstream infections due to Candida species: frequency of occurrence and in vitro susceptibilities to fluconazole, ravuconazole, and voriconazole of isolates collected from 1997 through 1999 in the SENTRY antimicrobial surveillance program

A surveillance program (SENTRY) of bloodstream infections (BSI) in the United States, Canada, Latin America, and Europe from 1997 through 1999 detected 1,184 episodes of candidemia in 71 medical centers (32 in the United States, 23 in Europe, 9 in Latin America, and 7 in Canada). Overall, 55% of the yeast BSIs were due to Candida albicans, followed by Candida glabrata and Candida parapsilosis (15%), Candida tropicalis (9%), and miscellaneous Candida spp. (6%). In the United States, 45% of candidemias were due to non-C. albicans species. C. glabrata (21%) was the most common non-C. albicans species in the United States, and the proportion of non-C. albicans BSIs was highest in Latin America (55%). C. albicans accounted for 60% of BSI in Canada and 58% in Europe. C. parapsilosis was the most common non-C. albicans species in Latin America (25%), Canada (16%), and Europe (17%). Isolates of C. albicans, C. parapsilosis, and C. tropicalis were all highly susceptible to fluconazole (97 to 100% at < or =8 microg/ml). Likewise, 97 to 100% of these species were inhibited by < or =1 microg/ml of ravuconazole (concentration at which 50% were inhibited [MIC(50)], 0.007 to 0.03 microg/ml) or voriconazole (MIC(50), 0.007 to 0.06 microg/ml). Both ravuconazole and voriconazole were significantly more active than fluconazole against C. glabrata (MIC(90)s of 0.5 to 1.0 microg/ml versus 16 to 32 microg/ml, respectively). A trend of increased susceptibility of C. glabrata to fluconazole was noted over the three-year period. The percentage of C. glabrata isolates susceptible to fluconazole increased from 48% in 1997 to 84% in 1999, and MIC(50)s decreased from 16 to 4 microg/ml. A similar trend was documented in both the Americas (57 to 84% susceptible) and Europe (22 to 80% susceptible). Some geographic differences in susceptibility to triazole were observed with Canadian isolates generally more susceptible than isolates from the United States and Europe. These observations suggest susceptibility patterns and trends among yeast isolates from BSI and raise additional questions that can be answered only by continued surveillance and clinical investigations of the type reported here (SENTRY Program).     

Comparison of restriction endonuclease analysis, ribotyping, and pulsed-field gel electrophoresis for molecular differentiation of Clostridium difficile strains.

A combined clinical and molecular epidemiologic analysis of 46 strains of Clostridium difficile, including 16 nosocomial isolates from one ward (outbreak ward) plus 17 other nosocomial isolates and 13 community-acquired isolates, was performed. HindIII digests of total cellular DNA were analyzed by restriction enzyme analysis (REA) and ribotyping; SmaI digests were analyzed by pulsed-field gel electrophoresis (PFGE). Isolates were assigned to typing groups on the basis of the profiles detected; isolates with closely related profiles were assigned to subgroups. The 16 isolates from the outbreak ward were resolved by both REA and PFGE into five distinct groups; 13 isolates represented two REA groups and three PFGE groups and two isolates were resolved as distinct groups by both techniques. DNA obtained from one isolate was persistently partially degraded, precluding analysis by PFGE. Seventeen sporadic nosocomial isolates were resolved by REA and PFGE into comparable numbers of groups (i.e., nine groups) and subgroups (i.e., 15 and 14 subgroups, respectively), with two isolates not evaluable by PFGE. The 13 epidemiologically unrelated community-acquired isolates were assigned to 11 groups by REA and to 12 groups by PFGE. Overall, ribotyping identified only nine groups among the 46 isolates. We conclude that REA and PFGE have comparable discriminatory powers for epidemiologic typing of C. difficile isolates and that ribotyping is appreciably less discriminatory. For a few isolates, partial DNA degradation prevented analysis by PFGE but not by REA or ribotyping; the cause of the degradation is unknown.     

Pulsed-field gel electrophoresis genotyping of Taylorella equigenitalis isolates collected in the United States from 1978 to 2010

Taylorella equigenitalis is the etiologic agent of contagious equine metritis (CEM), a venereal disease of horses. A total of 82 strains of T. equigenitalis isolated in the United States were analyzed by pulsed-field gel electrophoresis (PFGE) after digestion of genomic DNA with restriction enzyme ApaI. Twenty-eight of those strains isolated from horses in the 2009 U.S. outbreak (CEM09) were further analyzed with NotI and NaeI enzymes. When ApaI alone was used for analysis, the 82 isolates clustered into 15 different genotypes that clearly defined groups of horses with known epidemiological connections. The PFGE profiles of the CEM09 isolates were indistinguishable after digestion with ApaI, NotI, and NaeI and did not match those of isolates from previous U.S. outbreaks in 1978 and 2006 or of any other isolate from the National Veterinary Services Laboratories (NVSL) culture library. Coupled with the fact that the CEM09 isolates are epidemiologically related, these results suggest a common source for the outbreak not linked to previous occurrences of CEM in the United States.     

Genetic diversity among Borrelia burgdorferi isolates from wood rats and kangaroo rats in California.

Twenty-nine Borrelia burgdorferi isolates, obtained from dusky-footed wood rats (Neotoma fuscipes) and California kangaroo rats (Dipodomys californicus) in California, were analyzed genetically. Chromosomal DNA was examined by restriction endonuclease analysis (REA) and gene probe restriction fragment length polymorphism. Pulsed-field gel electrophoresis was used to analyze the plasmid profiles of the isolates. REA, the method with the greatest discrimination, disclosed 24 distinct restriction patterns among the 29 isolates. These restriction patterns were sorted into four restriction fragment length polymorphism groups on the basis of their gene hybridization patterns. Results of the REA and plasmid profile analysis supported this grouping. The degree of genetic diversity among Californian isolates demonstrated by our findings is greater than that previously reported among other groups of North American isolates and is similar or greater than the diversity reported among European isolates.     

Concordance of clinical and environmental isolates of Cryptococcus neoformans var. gattii by random amplification of polymorphic DNA analysis and PCR fingerprinting.

Sixty-one clinical and forty-nine environmental isolates of Cryptococcus neoformans var. gattii from Australia and the United States were analyzed by random amplification of polymorphic DNA (RAPD), using 12- to 22-mer primers in pairs, and/or PCR fingerprinting with a single primer derived from the microsatellite core sequence of the wild-type phage M13 (5' GAGGGTGGCGGTTCT 3'). Three major genetic profiles were identified by both typing techniques. A single RAPD profile (VGI) predominated among clinical isolates (44 of 48, 92%) and isolates from host eucalypts (45 of 45, 100%) from Australia. Of the 94 Australian isolates, 4 (3 clinical and 1 environmental) were assigned to profile VGII; 2 of these were recovered from patients and one was recovered from plant debris from Western Australia. Only one Australian clinical isolate was assigned to profile VGIII. A different distribution of RAPD profiles (four VGIII, two VGII, and one VGI) was found among four clinical and three environmental isolates from the United States. RAPD profiles of 8 of the 101 isolates studied revealed minor genetic variants, 4 of profile VGI and 4 of profile VGII. Genetic concordance between the majority of clinical and environmental isolates in Australia is consistent with the hypothesis that human disease is acquired from exposure to host eucalypts. Profiles of clinical isolates were independent of body site of infection, and profiles of all isolates were stable over time. Analysis by PCR fingerprinting confirmed the RAPD results. A second RAPD profile (VGII) was associated with infection in southwest Western Australia, where the two host eucalypts do not occur naturally. This raises the possibility of an alternative and as yet unidentified natural habitat of C. neoformans var. gattii. Our results indicate that RAPD analysis is a sensitive and useful method for investigating environmental sources of human infection with this biotype.     

Typing of group A streptococci by random amplified polymorphic DNA analysis.

Random amplified polymorphic DNA (RAPD) analysis was evaluated in comparison with restriction endonuclease analysis (REA) of genomic DNA and serotyping in the typing of 160 epidemiologically unrelated group A streptococci (GAS). Amplification of genomic DNA of GAS was performed with a single primer with an arbitrarily selected nucleotide sequence of 12 nucleotides. In total, 31 RAPD patterns and 15 REA patterns were observed among the isolates studied. The results of RAPD analysis were in accordance with the results of REA for 86% of the isolates, as both methods identified 15 different strains among 138 isolates. However, RAPD analysis differentiated 16 additional strains among 22 isolates. RAPD analysis was somewhat better than REA for differentiation of isolates of the same and different serotypes. However, not all of the serotypes were differentiated by RAPD analysis either. In conclusion, RAPD analysis provides a practical alternative for genomic typing of GAS. It can be recommended for the typing of GAS, especially if used in parallel with serotyping.     

Restriction endonuclease analysis of nosocomial isolates of Clostridium difficile.

A total of 110 clinical isolates of Clostridium difficile were analyzed by agarose gel electrophoresis by using both bacterial restriction endonuclease analysis (REA) and plasmid profiles. A total of 72 isolates were divided into 12 groups according to their REA patterns. Some 38 isolates exhibited unique patterns. Pattern A occurred in 20% of isolates. Isolates with patterns B, E, and G were cytotoxin negative. The remaining groups were cytotoxin positive. Multiple isolates obtained from two stool specimens were studied to examine the variation in REA profiles found in single specimens. In these specimens no variation in REA profiles was found. The stability of C. difficile was studied by examining sequential in vitro subcultures of a single isolate and strains isolated over a 4-month period from two long-term carriers. REA patterns were stable over time, both in vitro and in vivo. Because plasmid DNA was observed in 53% of isolates, plasmid profiles alone could not be used to study the spread of C. difficile; however, they were necessary for the interpretation of REA patterns in some instances.     

Characterization of Scedosporium prolificans clinical isolates by randomly amplified polymorphic DNA analysis.

Fingerprinting by randomly amplified polymorphic DNA (RAPD) analysis was used to differentiate Scedosporium prolificans isolates. A total of 59 arbitrary primers were screened with six unrelated S. prolificans isolates, and a panel of 12 primers was selected. The 12 primers were then used to detect DNA polymorphisms among 17 S. prolificans isolates from 11 patients with systemic S. prolificans infections diagnosed in three hospitals located in geographically different areas of Spain. Eight patients were diagnosed with S. prolificans infection in a single institution over a 6-year period, and two other patients were diagnosed with S. prolificans infection in a different hospital over a 1-year period. No single primer allowed for the discrimination of all the isolates from different patients, but this was possible by combining the RAPD patterns from three primers (UBC 701, AB1.08, and AB1.11 or UBC 701, AB1.08, and UBC 707). However, multiple isolates from the same patient were identical. In this study, we also compared a visual method and a computerized method for the analysis of the RAPD patterns. Both methods were satisfactory and gave few discordances, but given the advantages and disadvantages of each method, both systems should be used together. RAPD analysis provided a fast and economical means of typing S. prolificans isolates, with a high level of discrimination among unrelated isolates. Typing by RAPD analysis confirmed that the S. prolificans infections were epidemiologically unrelated.     

Comparative analysis of genetic variability among Borrelia burgdorferi isolates from Europe and the United States by restriction enzyme analysis, gene restriction fragment length polymorphism, and pulsed-field gel electrophoresis.

The genomes of 62 North American and European Borrelia burgdorferi isolates were examined by restriction endonuclease analysis (REA), gene probe restriction fragment length polymorphism, and pulsed-field gel electrophoresis (PFGE). Hybridization of restriction fragments with the immunologically relevant 83-kDa antigen gene revealed polymorphisms and divided the isolates into three major groups. Group I included all but two of the American isolates and some of the European isolates. One of two Californian isolates (DN 127) and one Ixodes dammini isolate from New York (strain 25015), previously described as atypical, were distinct from the isolates in the three groups. Plasmid profile analysis and REA, the method with the highest level of discrimination, revealed extensive heterogeneity among isolates of the same major group. Our study demonstrates the usefulness of the 83-kDa antigen gene probe for dividing the isolates into major genogroups, whereas REA and plasmid profile analysis allow for a distinction of individual strains within these groups.     

Phylogenetic analysis of classical swine fever virus (CSFV) field isolates from outbreaks in South and Central America

To date, there is little information concerning the epidemiological situation of classical swine fever (CSF) in the Americas. Besides summarizing the available data, genotyping of isolates from outbreaks in domestic pigs in several countries of South and Central America was performed. For this, a 190 base fragment of the E2 envelope glycoprotein gene was used. European strains and isolates, and historical isolates from the United States (US) were included for comparison. In contrast to the situation in most parts of Europe, where group 2 isolates predominate, it was found that all the isolates from the American continent analyzed belonged to group 1 and were further resolved into three subgroups. The Cuban isolates clustered in subgroup 1.2, whereas the isolates from Honduras and Guatemala clustered in subgroup 1.3. The remaining isolates from Argentina, Brazil, Colombia and Mexico generated four poorly resolved clusters in subgroup 1.1, together with the vaccine strains, with historical European and US isolates, and with a recent Russian isolate. While the vaccine strains and the historical European isolates formed a relatively distinct cluster, one of the US isolates clustered together with the Mexican, and another one with Colombian isolates. Historically, CSF (hog cholera) was observed almost simultaneously in the US and in Europe in the first half of the 19th century, and its origin remains a matter of discussion. Our results showed that the US isolates are closely related to isolates from South America, while appearance of isolates in Cuba on one hand and in Honduras and Guatemala on the other hand, seems to have been due to unrelated events. This allows to speculate that at least in the American continent, CSF virus may have appeared independently in several regions, and spreading may have been a secondary effect.     

Characterization of noncapsulate Haemophilus influenzae by whole-cell polypeptide profiles, restriction endonuclease analysis, and rRNA gene restriction patterns.

Thirty-four clinical isolates of noncapsulate Haemophilus influenzae representing isolates with either related or dissimilar patterns of whole-cell polypeptide profiles on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were further characterized by restriction enzyme analysis (REA) and rRNA gene restriction patterns. Total cellular DNA was extracted by a rapid, microcentrifuge-scale method and digested with BamHI, which gave a pattern of about 18 discrete bands. This confirmed the five closely related groupings suggested by SDS-PAGE. Isolates dissimilar by SDS-PAGE were also distinguishable by REA. However, there was no correlation between the degrees of similarity estimated from whole-cell polypeptide profiles and those obtained from REA for the dissimilar isolates. Therefore, inferences of genetic relatedness made on the basis of these data should be interpreted with caution. rRNA gene restriction patterns also confirmed the groupings suggested by the other two techniques. We conclude that the three methods were highly discriminatory and that whole-cell polypeptide patterns or REA with BamHI would be appropriate techniques for epidemiological studies of noncapsulate H. influenzae.     

Restriction endonuclease analysis of Staphylococcus epidermidis DNA may be a useful epidemiological marker.

We compared the epidemiological markers of 13 Staphylococcus epidermidis strains isolated from an adult inpatient during a febrile episode and 23 S. epidermidis strains isolated during a presumptive outbreak of nosocomial infection in a neonatal ward. The total DNA restriction endonuclease analysis (REA) was processed along with the following conventional markers: biotyping, serotyping, phage typing, antibiotic susceptibility profiles, and plasmid profiles. The REA method was reproducible, giving stable results both in vitro and in vivo. For the hospitalized adult patient, the conventional markers of the 13 strains were concordant and the restriction profiles were identical. Five restriction groups were demonstrated during the course of the outbreak. Within two of the groups, the identities of all of the markers were used to verify whether all of the isolates belonged to the same cell clone. In a third group, combined analysis of the conventional markers and REA had to be used to demonstrate isolate similarity. On the other hand, in another group, none of the markers were similar; interpretation was not easy. An epidemiological study of S. epidermidis infections in hospitals must take into account all of the epidemiological markers: biotypes, serotypes, phage types, antibiograms, plasmid profiles, and REA.     

A fluorescent amplified fragment length polymorphism study of Salmonella enterica serovar Sofia, the major Salmonella serovar isolated from chickens in Australia

Fluorescent amplified fragment length polymorphism (FAFLP) analysis was performed on 68 isolates of Salmonella enterica subsp. salamae serovar Sofia (S. Sofia). Fifty eight isolates were obtained over a period of approximately 15 years from a range of human, chicken industry and environmental sources throughout Australia. A further ten isolates were identified from human and poultry sources in Israel from 1972 to 1987. Analysis of FAFLP profiles for fragments between 50 to 500 base pairs in length indicated distinct clusters of isolates. All but seven isolates clustered into four groups of >90% similarity and all isolates displayed at least 70% similarity with each other. No cluster could be attributed to a particular geographical, temporal or source-of-isolation origin. It is concluded that S. Sofia is genetically variable with certain clones persisting over time but no group appears unique to Australia.     

Comparison of three typing methods for clinical and environmental isolates of Aspergillus fumigatus.

To evaluate procedures used for epidemiologic analysis of outbreaks of aspergillosis, we analyzed a collection of 35 Aspergillus fumigatus isolates using three typing methods: isoenzyme analysis (IEA), random amplified polymorphic DNA (RAPD) analysis, and restriction endonuclease analysis (REA). Twenty-one isolates were from a single hospital, with four isolates coming from different patients. Three clinical isolates came from a different hospital, and 11 clinical or environmental isolates were derived from a culture collection. With IEA, the patterns of alkaline phosphatase, esterase, and catalase discriminated nine types. In contrast, 22 types were obtained with five different RAPD primers, and 21 types could be detected with three of these (R108, R151, and UBC90). Restriction endonuclease analysis of genomic DNA, digested with either XbaI, XhoI, or SalI, detected 3, 17, and 13 different REA types, respectively, and 22 types were identified by combining the data from the XhoI and SalI REAs. Twenty-eight types were obtainable with a combination of REA, IEA, and RAPD patterns. Overall, the results pointed to substantial genetic variation among the isolates. Though two isolates had markedly distinct genotypes, their morphologic features and exoantigens were consistent with their being A. fumigatus. The analysis will help in planning epidemiologic studies of aspergillosis.     

Molecular characterization of Haemophilus ducreyi isolates from different geographical locations

The technique of random amplified polymorphic DNA (RAPD) was adapted and optimized to study Haemophilus ducreyi isolates. A panel of 43 strains isolated from chancroid patients from different countries in Africa, Europe, North America, and Asia were characterized. The strains were also studied with respect to lipooligosaccharide (LOS) migration and immunoblotting patterns and the presence of cytolethal distending toxin genes. The RAPD method with the OPJ20 primer generated nine banding patterns (1 to 9). The majority of the isolates were clustered into two major profiles, 14 and 13 strains into profiles 1 and 2, respectively, and just a few strains revealed patterns 3 and 4. The isolates from Thailand were exceptional in that they showed greater diversity and were represented by six different RAPD patterns, i.e., patterns 3 and 5 to 9. The LOS migration and immunoblotting analyses revealed two different patterns, which indicated long and short forms of LOS; the former was found in 20/23 tested strains. Two strains that expressed the short form of LOS were grouped into RAPD pattern 4. The absence of cdtABC genes was observed in only 4/23 strains, and three of these isolates were assigned to RAPD pattern 4. Our results showed limited genotypic and phenotypic variations among H. ducreyi strains, as supported by the conserved RAPD and LOS profiles shared by the majority of the studied strains. However, the RAPD method identified differences between strains, including those from different geographic areas, which indicate the potential of RAPD as an epidemiological tool for the typing of H. ducreyi isolates in countries where chancroid is endemic.