Evaluation of the inaccurate assignment of mixed infections by Mycobacterium tuberculosis as exogenous reinfection and analysis of the potential role of bacterial factors in reinfection

Molecular analysis of recurrent tuberculosis has revealed that a second episode may be caused by a strain of Mycobacterium tuberculosis other than that involved in the first infection, thus indicating that exogenous reinfection plays a role in recurrence. We focused on two aspects of reinfection that have received little attention. First, we evaluated whether a lack of methodological refinement could lead to inaccurate assignment of mixed infections as exogenous reinfection, in which a differential selection of each of the coinfecting strains occurred over time. We used the mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) method to genotype 122 isolates from 40 patients with recurrent tuberculosis. We identified 11/40 (27.5%) cases with genotypic differences between the isolates involved in the sequential episodes. Major genotypic differences were found in 8/11 cases, suggesting exogenous reinfection; in the remaining 3 cases, subtle genotypic differences were observed, probably indicating microevolution from a parental strain. In all cases, only a single strain was detected for the isolate(s) from each episode, thus ruling out the possibility that reinfection could correspond to undetected mixed infection. Second, we analyzed the infectivity of a selection of 12 strains from six cases with genotypically different strains between episodes. No main differences were observed in an ex vivo model of infection between the strains involved in the first episodes and those involved in the recurrent episodes. In our setting, our results suggest the following: (i) the possibility of misassignment of mixed infection as exogenous reinfection is improbable, and (ii) bacterial infectivity does not seem to play a role in exogenous reinfection.     

Exogenous reinfection as a cause of recurrent tuberculosis after curative treatment.

BACKGROUND: For decades it has been assumed that postprimary tuberculosis is usually caused by reactivation of endogenous infection rather than by a new, exogenous infection. METHODS: We performed DNA fingerprinting with restriction-fragment-length polymorphism analysis on pairs of isolates of Mycobacterium tuberculosis from 16 compliant patients who had a relapse of pulmonary tuberculosis after curative treatment of postprimary tuberculosis. The patients lived in areas of South Africa where tuberculosis is endemic. Medical records were reviewed for clinical data. RESULTS: For 12 of the 16 patients, the restriction-fragment-length polymorphism banding patterns for the isolates obtained after the relapse were different from those for the isolates from the initial tuberculous disease. This finding indicates that reinfection was the cause of the recurrence of tuberculosis after curative treatment. Two patients had reinfections with a multidrug-resistant strain. All 15 patients who were tested for the human immunodeficiency virus were seronegative. CONCLUSIONS: Exogenous reinfection appears to be a major cause of postprimary tuberculosis after a previous cure in an area with a high incidence of this disease. This finding emphasizes the importance of achieving cures and of preventing anyone with infectious tuberculosis from exposing others to the disease.     

Involvement of multiple Cryptococcus neoformans strains in a single episode of cryptococcosis and reinfection with novel strains in recurrent infection demonstrated by random amplification of polymorphic DNA and DNA fingerprinting.

We compared the abilities of random amplification of polymorphic DNA and DNA fingerprinting, with oligonucleotide probes, to type five pairs of Cryptococcus neoformans clinical isolates recovered from five separate human immunodeficiency virus-positive patients in London, England. The two techniques had comparable discriminatory abilities when applied to these isolates. A total of eight different isolate types were demonstrated in these patients. No isolate type was observed in more than one patient. Two of the isolate pairs recovered from single episodes of cryptococcosis within 1 day of each other were genotypically indistinguishable by both methods. The other three pairs of isolates were all distinguishable. One of these isolate pairs was obtained from a single episode of cryptococcosis, while the other two were obtained from recurrent infections. These results indicate that multiple strains of C. neoformans may be responsible for a single episode of cryptococcosis and that recurrent infection may occur as a result of reinfection with a novel strain.     

Nosocomial Outbreak of Multidrug-Resistant Tuberculosis Caused by a Strain of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> W-Beijing Family in St. Petersburg,Russia

A molecular epidemiologic study of 35 Mycobacterium tuberculosis isolates from 19 patients was conducted to define a nosocomial outbreak of multidrug-resistant tuberculosis in St. Petersburg, Russia. IS6110-restriction fragment length polymorphism (RFLP) fingerprinting, together with investigations to detect mutations conferring drug resistance, revealed relationships between the isolates and links between the cases. Three patients and a nurse exposed to active tuberculosis were proved to be involved in the outbreak; the source case was identified. The outbreak strain possessed a 17-band RFLP pattern and a spoligoprofile (signals 35–43) characteristic of the W-Beijing family as well as distinctive mutations in katG315, rpoB531, embB306 and rpsL43. This specific RFLP pattern has previously been identified among Mycobacterium tuberculosis W-Beijing strains isolated across the former Soviet Union and in the St. Petersburg area of Russia. The spread of multidrug-resistant strains of W-Beijing genotype in the general population and in hospital settings presents a serious threat for public health in Russia. Specific pathogenic properties of W-Beijing genotype strains, such as enhanced transmissibility and the ability to cause reinfection and to readily acquire drug resistance to major antituberculosis drugs, along with special features of host response, have yet to be investigated. Electronic Publication     

Long-term molecular analysis of tuberculosis strains in alabama, a state characterized by a largely indigenous, low-risk population

With a tuberculosis case detection rate of 5.9 per 100,000 population in 2001, Alabama ranked twelfth highest in the United States. However, cases among foreign-born and human immunodeficiency virus-infected individuals remain low in Alabama. To understand the endemic statewide disease pattern, tuberculosis strains were studied for clustering in a long-term population-based study from January 1994 to May 2000. IS6110 restriction fragment length polymorphism analysis was performed for 1,834 strains. Spoligotyping was used as a secondary typing method for the 37% of isolates displaying a restriction fragment length polymorphism pattern with <6 IS6110 copies. A total of 721 (41%) patients provided isolates that composed 114 clusters, each containing isolates from 2 to 136 patients, suggesting that recent transmission accounted for 35% of tuberculosis cases. Demographic, behavioral, and clinical characteristics of patients with clustered versus nonclustered isolates stratified by low-copy-number strains (<6 IS6110 copies) versus high-copy-number strains (> or =6 IS6110 copies) were evaluated. Younger age, black race, a history of alcohol abuse, and homelessness were predictors of clustering of low-copy-number, strains and younger age, urban residency, alcohol abuse, homelessness, noninjection drug use, and a history of incarceration and/or cavitary disease were predictors of clustering of high-copy-number strains. By identifying local characteristics of tuberculosis clustering through molecular fingerprinting, control programs can distribute their limited resources to impact the transmission of tuberculosis in high-risk populations and evaluate strain distribution across geographical areas.     

Molecular epidemiology of late recurrent candidaemia—a population-based study in Iceland

Candidaemia is associated with high patient mortality. Among those who survive an initial episode of candidaemia, the incidence of recurrent episodes has been incompletely defined. All patients in Iceland with candidaemia in 1980–2008 were identified, and clinical information was reviewed. Episodes of candidaemia in the same patient were considered to be separate if they occurred ≥1 month apart or were caused by different Candida species. The isolates were genotyped by using PCR fingerprinting, and antifungal susceptibility was determined. During the 29-year period, candidaemia was diagnosed in 307 patients in Iceland, 298 of whom (97.1%) had a single episode. Overall, 206 patients survived >1 month from the first episode and were therefore at risk of recurrence, yielding 1062 patient-years of observation in the survivors. Of those, nine (4.4%) later developed recurrent candidaemia. The median time between recurrences was 6 months (range, <1 month to 14 years). Patients with late recurrences were younger (p 0.012) and more likely to have underlying gastrointestinal diseases than patients with single episodes (55.6% vs. 18.5%, respectively; p 0.017). The recurrences were caused by identical Candida sp. genotypes in two of 13 cases (15%), but by different species or dissimilar genotypes in eight of 13 (62%); isolates were missing in three cases. In conclusion, late recurrent candidaemia was a relatively rare event, and younger patients with gastrointestinal disorders were more prone to recurrent infections. The majority of late recurrences represented re-infections with new Candida strains that were susceptible to common antifungal agents.     

DNA fingerprinting of Mycobacterium tuberculosis isolates from Agra region by IS 6110 probe

DNA fingerprinting using IS 6110 probe has been used all over the world quite successfully to characterize M. tuberculosis strains. The present study has been carried out to study the polymorphism among isolates of M. tuberculosis from Agra region from patients attending the clinics at SN Medical College and TBDTC, Agra. Sputa were collected in sterilized containers and brought to CJIL, Agra. Samples were processed and cultured on Lowenstein Jensen (LJ) slants. M. tuberculosis isolates were identified by standard biochemical tests. DNA from these isolates were purified by a physicochemical procedure, restricted with Pvu II enzyme and hybridized with PCR amplified and DIG labeled 245 bp IS 6110 probe. With a view to study IS 6110 polymorphism, M. tuberculosis isolates obtained from different geographical areas of Agra region were analyzed. Among the 60 isolates taken in study, 5 had no copy of IS 6110, 8 had 1-4 copies and 47 had multiple copies of IS 6110. DNA fingerprinting using this probe was found to be quite discriminating for typing of most of the strains (80%) which had multiple copies. RFLP profiles did not correlate with geographical areas, contacts or the resistance pattern of the strains. While this data shows the potential of IS 6110 based RFLP for strain characterization of M. tuberculosis in Agra, to understand the molecular epidemiology of tuberculosis in this region, a larger number of isolates from defined geographical areas need to be studied.     

Recurrent melioidosis in patients in northeast Thailand is frequently due to reinfection rather than relapse

Human melioidosis is associated with a high rate of recurrent disease, despite adequate antimicrobial treatment. Here, we define the rate of relapse versus the rate of reinfection in 116 patients with 123 episodes of recurrent melioidosis who were treated at Sappasithiprasong Hospital in Northeast Thailand between 1986 and 2005. Pulsed-field gel electrophoresis was performed on all isolates; isolates from primary and recurrent disease for a given patient different by one or more bands were examined by a sequence-based approach based on multilocus sequence typing. Overall, 92 episodes (75%) of recurrent disease were caused by the same strain (relapse) and 31 episodes (25%) were due to infection with a new strain (reinfection). The interval to recurrence differed between patients with relapse and reinfection; those with relapses had a median time to relapse of 228 days (range, 15 to 3,757 days; interquartile range [IQR], 99.5 to 608 days), while those with reinfection had a median time to reinfection of 823 days (range, 17 to 2,931 days; IQR, 453 to 1,211 days) (P = 0.0001). A total of 64 episodes (52%) occurred within 12 months of the primary infection. Relapse was responsible for 57 of 64 (89%) episodes of recurrent infection within the first year after primary disease, whereas relapse was responsible for 35 of 59 (59%) episodes after 1 year (P < 0.0001). Our data indicate that in this setting of endemicity, reinfection is responsible for one-quarter of recurrent cases. This finding has important implications for the clinical management of melioidosis patients and for antibiotic treatment studies that use recurrent disease as a marker for treatment failure.     

Molecular epidemiology of drug-resistant tuberculosis in Hungary

Sixty-eight drug-resistant Mycobacterium tuberculosis isolates (44.2% of all resistant cases) were analyzed by IS6110 restriction fragment length polymorphism fingerprinting and spoligotyping to provide a deeper insight into the status of drug-resistant tuberculosis in Hungary. A total of 54.4% of the drug-resistant cases and 75% of the multidrug-resistant cases could be clustered. Analysis of the spoligotyping patterns of the strains revealed a high rate (66.2%) of infection by the Haarlem genotype, while none of the patients were infected by the Beijing genotype. The magnitude and the dynamics of drug-resistant tuberculosis are underestimated in Hungary.     

Molecular epidemiology of tuberculosis in Austria

Summary The incidence of pulmonary tuberculosis among newspaper vendors, tram operators, and other exposed groups leads to repeated discussions about the importance of single cases for the spread of tuberculous infection. We subjected 36 strains of Mycobacterium tuberculosis, isolated in 1992 from 31 patients, to restriction fragment length polymorphism analysis using PvuII and an insertion element 986 probe. Only two isolates obtained from a married couple showed the same DNA fingerprinting pattern, all the other strains had unique and clearly distinguishable banding patterns. Our investigation revealed no dominating strains except in the case of one married couple, where the chain of infection was obvious (the wife being diagnosed during the course of testing of her alcoholic and tuberculous husband's contacts). The main emphasis in the fight against tuberculosis still rests on securing the availability of diagnostic and therapeutic means for all patients with tuberculosis. The importance of single infected source cases for the spread of tuberculosis should not be overestimated.Abbreviations IS insertion sequence - RFLP restriction fragment length polymorphism     

Systematic molecular characterization of multidrug-resistant Mycobacterium tuberculosis complex isolates from Spain

We used spoligotyping and restriction fragment length polymorphism (RFLP) of the IS6110-insertion sequence to study the molecular epidemiology of multidrug-resistant (MDR) tuberculosis in Spain. We analyzed 180 Mycobacterium tuberculosis complex isolates collected between January 1998 and December 2000. Consecutive isolates from the same patients (n = 23) always had identical genotypes, meaning that no cases of reinfection occurred. A total of 105 isolates (58.3%) had unique RFLP patterns, whereas 75 isolates (41.7%) were in 20 different RFLP clusters. Characterization of the katG and rpoB genes showed that 14 strains included in the RFLP clusters did not actually cluster. Only 33.8% of the strains isolated were suggestive of MDR transmission, a frequency lower than that for susceptible strains in Spain (46.6%). We found that the Beijing/W genotype, which is prevalent worldwide, was significantly associated with immigrants. The 22 isolates in the largest cluster corresponded to the Mycobacterium bovis strain responsible for two nosocomial MDR outbreaks in Spain.     

Molecular epidemiology of tuberculosis in Denmark in 1992.

The incidence of tuberculosis (TB) is increasing all over the world, including in countries with a high standard of living and good social security. Denmark represents such a region. Furthermore, it is a small country (5 million inhabitants) with a long tradition in TB control, including a centralization of the bacteriological diagnostic facility. The present study was intended to analyze the transmission of Mycobacterium tuberculosis in a country in which TB has low endemicity by a combination of conventional epidemiological approaches and DNA fingerprinting techniques, whereby individual bacterial strains can be traced. M. tuberculosis isolates from 92% of all new cases of bacteriologically verified TB in Denmark during 1992 were subjected to IS6110 DNA fingerprinting to visualize the DNA restriction fragment length polymorphism (RFLP) patterns of the isolated strains. The data obtained from the RFLP analyses were interpreted by using demographic data, such as age, sex, ethnicity, and residence, for the patients. The risk factors among the patients for being part of an active chain of transmission, as opposed to demonstrating reactivation of a previously acquired latent infection, were estimated by statistical analyses. The magnitude of TB transmission in 1992 in Denmark was determined, and transmitted infections were shown to comprise at least one quarter of the total number of cases. Almost half of the TB cases involved patients of foreign origin. However, most of these isolates showed unique DNA fingerprint patterns and were rarely part of an active chain of transmission. The major chains of recent transmission were localized to distinct geographical regions in the country.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular Fingerprinting of Mycobacterium tuberculosis and Risk Factors for Tuberculosis Transmission in Paris, France, and Surrounding Area

Forty-three percent of the tuberculosis cases reported in France are from the Ile de France region. The incidence of tuberculosis in this region is 33 cases per 100,000 inhabitants, twice the national average. A restriction fragment length polymorphism (RFLP) analysis was performed with clinical isolates of Mycobacterium tuberculosis isolated during 1995 in 10 hospitals in Paris and surrounding areas to detect tuberculosis transmission and define the factors associated with clustering in this population. The molecular markers used were the insertion sequence IS6110 and the direct repeat (DR) sequence. Social, demographic, and clinical data were collected from the patients’ medical files. Ten patients with isolates with a single copy of IS6110 were excluded from further analysis. Twenty-four patients with false-positive cultures due to laboratory contamination (based on RFLP analysis with IS6110 and examination of patient data) were also excluded. The study was then conducted with 272 strains isolated from 272 patients. Further fingerprinting was performed by using the DR element with strains with patterns by RFLP analysis with IS6110 that differed by one band only and strains with identical patterns by RFLP analysis with IS6110 and with low numbers of copies of IS6110. The combined use of both markers identified unique patterns for 177 strains and clustered 95 (35.7%) strains in 26 groups, each containing isolates from 2 to 12 patients. The clustering was strongly associated with homelessness and the male sex. It was not associated with age, birth in a foreign country, human immunodeficiency virus positivity, or residence in hostels or prison. Isolates from homeless people were often included in large clusters, and homeless people could be the source of tuberculosis transmission for more than 50% of the clustered patients. These results suggest that homeless people play a key role in the spread of M. tuberculosis in the community and that poor socioeconomic conditions are the main risk factors associated with active tuberculosis transmission.     

Spread of drug-resistant pulmonary tuberculosis in Estonia

Restriction fragment length polymorphism (RFLP) analysis of 209 Mycobacterium tuberculosis clinical isolates obtained from newly detected pulmonary tuberculosis patients (151 male and 58 female; mean age, 41 years) in Estonia during 1994 showed that 61 isolates (29%) belonged to a genetically closely related group of isolates, family A, with a predominant IS6110 banding pattern. These strains shared the majority of their IS6110 DNA-containing restriction fragments, representing a predominant banding pattern (similarity, >65%). This family A comprised 12 clusters of identical isolates, and the largest cluster comprised 10 strains. The majority (87.5%) of all multidrug-resistant (MDR) isolates, 67.2% of all isolates with any drug resistance, but only 12% of the fully susceptible isolates of M. tuberculosis belonged to family A. These strains were confirmed by spoligotyping as members of the Beijing genotype family. The spread of Beijing genotype MDR M. tuberculosis strains was also frequently seen in 1997 to 1999. The members of this homogenous group of drug-resistant M. tuberculosis strains have contributed substantially to the continual emergence of drug-resistant tuberculosis all over Estonia.     

Tuberculosis reinfection and relapse in eastern China: a prospective study using whole-genome sequencing

ObjectivesTuberculosis recurrence after an initial successful treatment episode can occur from either reinfection or relapse. In a population-based sample and whole genome sequencing in eastern China, we aimed to evaluate risk factors for tuberculosis recurrence and assess the proportion of recurrence because of either reinfection or relapse.MethodsSuccessfully treated pulmonary tuberculosis patients with sputum culture positive results were recruited from five cities in Jiangsu Province from 2013 to 2015 and followed for 2 years for tuberculosis recurrence. Among patients developing a second tuberculosis episode, whole genome sequencing was performed to distinguish relapse or reinfection through a distance threshold of 6-single-nucleotide polymorphisms. We analyzed risk factors for recurrence and epidemiological characteristics of different types of recurrent patients.ResultsOf 1897 successfully treated tuberculosis patients, 7.4% (141/1879) developed recurrent tuberculosis. Compared with nonrecurrent tuberculosis, patients were at higher risk of recurrence in older age (adjusted odds ratio, 1.02 for each additional year; 95% CI, 1.01 to 1.03, p = 0.003), patients previously treated for tuberculosis (adjusted odds ratio = 2.22; 95% CI, 1.52 to 3.26, p < 0.001), or with bilateral cavities (adjusted odds ratio, 1.56; 95% CI, 1.05 to 2.32, p = 0.029). Among 27.0% (38/141) recurrent tuberculosis patients with successfully sequenced pairs, relapse was substantially more common than reinfection (71.1% vs 28.9%, p = 0.014).DiscussionEndogenous relapse was significantly more common than exogenous reinfection in the first 2 years after treatment in eastern China. Prioritization of high-risk groups for recurrence, such as the elderly, with a previous tuberculosis diagnosis, or with bilateral cavities, may provide opportunities to reduce post-tuberculosis morbidity.     

Mixed-linker polymerase chain reaction: a new method for rapid fingerprinting of isolates of the Mycobacterium tuberculosis complex.

Rapid recognition of multidrug-resistant strains of Mycobacterium tuberculosis is a desirable goal for treatment of patients and protection of health care workers. DNA fingerprints produced with the insertion sequence IS6110 generate restriction fragment length polymorphism (RFLP) patterns that reliably identify M. tuberculosis complex strains. This report describes a rapid technique for RFLP typing using the polymerase chain reaction. The method uses one primer specific for IS6110 and a second primer complementary to a linker ligated to the restricted genomic DNA. In one strand the linker contains uracil in place of thymidine, and specific amplification is obtained by elimination of this strand with uracil N-glycosylase. Mixed-linker fingerprinting clearly differentiated multidrug-resistant isolates from 12 outbreaks and unambiguously assigned them to 26 RFLP groups.     

Emergence of additional drug resistance during treatment of multidrug-resistant tuberculosis in China: a prospective cohort study

ObjectivesLittle is known about how additional second-line drug resistance emerges during multidrug-resistant tuberculosis (MDR-TB) treatment. The present study aimed to investigate the influence of microevolution, exogenous reinfection and mixed infection on second-line drug resistance during the recommended 2-year MDR-TB treatment.MethodsIndividuals with MDR-TB were enrolled between 2013 and 2016 in a multicentre prospective observational cohort study and were followed up for 2 years until treatment completion. Whole-genome sequencing (WGS) was applied for serial Mycobacterium tuberculosis isolates from study participants throughout the treatment, to study the role of microevolution, exogenous reinfection and mixed infection in the development of second-line drug resistance.ResultsOf the 286 enrolled patients with MDR-TB, 63 (22.0%) M. tuberculosis isolates developed additional drug resistance during the MDR-TB treatment, including 5 that fulfilled the criteria of extensively drug-resistant TB. By comparing WGS data of serial isolates retrieved from the patients throughout treatment, 41 (65.1%) of the cases of additional second-line drug resistance were the result of exogenous reinfection, 18 (28.6%) were caused by acquired drug resistance, i.e. microevolution, while the remaining 4 (6.3%) were caused by mixed infections with drug-resistant and drug-susceptible strains. In multivariate analysis, previous TB treatment (adjusted hazard ratio (aHR) 2.51, 95% CI 1.51–4.18), extensive disease on chest X-ray (aHR 3.39, 95% CI 2.03–5.66) and type 2 diabetes mellitus (aHR 4.00, 95% CI 2.22–7.21) were independent risk factors associated with the development of additional second-line drug resistance.ConclusionsA large proportion of additional second-line drug resistance emerging during MDR-TB treatment was attributed to exogenous reinfection, indicating the urgency of infection control in health facilities as well as the need for repeated drug susceptibility testing throughout MDR-TB treatment.     

Comparison of DNA fingerprint patterns of isolates of Mycobacterium africanum from east and west Africa.

Mycobacterium africanum is a pathogen found in tuberculosis patients in certain parts of Africa and is a member of the Mycobacterium tuberculosis complex. Biochemically, strains of M. africanum exhibit a high degree of variability, with some tendency to cluster according to their geographical origin. To investigate whether this phenotypic variability is reflected at the genetic level, we performed DNA fingerprint analysis of strains isolated from patients with pulmonary tuberculosis in Uganda and Sierra Leone. IS6110 DNA fingerprinting was carried out by the mixed-linker PCR method. A total of 138 strains of M. africanum were analyzed: 42 isolates from Uganda and 96 isolates from Sierra Leone. With few exceptions, the resulting DNA fingerprint patterns grouped together according to their country of origin. A striking lack of variability of DNA fingerprints was found for strains from Sierra Leone, where 70 of 96 isolates (61.5%) fell into clusters. The two largest clusters accounted for 41.7% of all isolates and differed by only one band, as confirmed by standard DNA fingerprinting. In contrast, only two clusters (7.1%) with two and three isolates, respectively, were found for M. africanum isolates collected in Uganda, and three of the DNA fingerprints contained fewer than seven bands. Strains of M. tuberculosis collected and processed during the same time period were highly variable in both countries. Our results support the concept of geographically defined subtypes of M. africanum. In addition, they demonstrate that natural geographic differences in the variability of IS6110 DNA fingerprints within the M. tuberculosis complex must be considered if this technique is used for epidemiologic studies.     

Clinical Manifestations and Molecular Epidemiology of Late Recurrent Candidemia, and Implications for Management

 The aim of this study was to define the epidemiology and clinical manifestations of late recurrent candidemia. For this purpose, late recurrent candidemia was defined as an episode of candidemia occurring at least 1 month after the apparent complete resolution of an infectious episode caused by the same Candida sp. A total of five patients with recurrent candidemia were investigated. For all patients, isolates from the initial and recurrent episodes of candidemia were available for in vitro susceptibility testing and genetic characterization by DNA-based techniques. The results revealed the following salient features: prolonged duration between the initial and recurrent episodes (range, 1–8 months); recurrence of candidemia despite antifungal therapy; importance of retained intravascular catheters, neutropenia, and corticosteroids as factors predisposing to recurrence; high morbidity and mortality; no emergence of antifungal drug resistance between the initial and recurrent episodes; and relapse of infection due to the original infecting strain, rather than reinfection with a new strain. These findings raise several issues about the management and follow-up of patients with candidemia, which require assessment in future studies.     

Culture-Confirmed Reinfection of a Person with Different Strains of Borrelia burgdorferi Sensu Stricto

In recent years, the utility of serum-based diagnostic testing for Lyme disease has improved substantially; however, recovery by culture of the bacterium from skin biopsies of suspected patients is still the only definitive laboratory test. Reinfection of patients has been assumed to occur but as yet has not been documented by serial isolates from the same person. We present a case of culture-confirmed reinfection of a patient in Menominee County, Michigan. Borrelia burgdorferi was isolated from the skin punch biopsy specimens during each episode of erythema migrans (EM) and was subjected to molecular strain typing, genetic analysis of two outer surface protein genes, protein profile analysis, and serum antibody response testing. Results show that these isolates are distinct strains of the bacterium and that the two episodes of EM were caused by independent infections. This report describes the documented, culture-confirmed reinfection of a human by two different strains of B. burgdorferi.