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PubMed1996

[Erysipelothrix rhusiopathiae: plasmids, resistance to antibacterial drugs].

The plasmid profile, virulence and antibacterial drug susceptibility of various strains of E. rhusiopathiae were determined. No correlations between the virulence of the strains, their antibiotic resistance and the plasmid content were detected. Structural and functional analysis of one of the isolated plasmids was carried out to use the plasmid as a vector in the genetic study of E. rhusiopathiae.

Drug Resistance, Microbial↗
PubMed2007

Amplified fragment length polymorphism of Streptococcus suis strains correlates with their profile of virulence-associated genes and clinical background.

Amplified fragment length polymorphism (AFLP) typing was applied to 116 Streptococcus suis isolates with different clinical backgrounds (invasive/pneumonia/carrier/human) and with known profiles of virulence-associated genes (cps1, -2, -7 and -9, as well as mrp, epf and sly). A dendrogram was generated that allowed identification of two clusters (A and C) with different subclusters (A1, A2, C1 and C2) and two heterogeneous groups of strains (B and D). For comparison, three strains from each AFLP subcluster and group were subjected to multilocus sequence typing (MLST) analysis. The closest relationship and lowest diversity were found for patterns clustering within AFLP subcluster A1, which corresponded with sequence type (ST) complex 1. Strains within subcluster A1 were mainly invasive cps1 and mrp+ epf+ (or epf*) sly+ cps2+ strains of porcine or human origin. A new finding of this study was the clustering of invasive mrp* cps9 isolates within subcluster A2. MLST analysis suggested that A2 correlates with a single ST complex (ST87). In contrast to A1 and A2, subclusters C1 and C2 contained mainly pneumonia isolates of genotype cps7 or cps2 and epf- sly-. In conclusion, this study demonstrates that AFLP allows identification of clusters of S. suis strains with clinical relevance.

Animals↗
PubMed1988

[Plasmid profile types of virulent and avirulent strains of phase-I Shigella sonnei and their rough phase-II and R-form variants].

The study of S. sonnei in phase I, irrespective of their virulence, has revealed the existence of at least 3 types of profiles of large plasmids: (I)A having a single plasmid with a molecular weight of about 120 MD; (I)B having, alongside plasmid pSS120, a plasmid with a molecular weight of about 60 MD; (I)C, represented only by vaccine strain 6S, having three plasmids with molecular weights of about 80, 60 and 37 MD. The plasmid profiles of rough S. sonnei in phase II are characterized by the absence of large plasmids with a molecular weight of 120-80 MD, typical of bacteria in phase I, and can be in their turn subdivided, in accordance with the type of the initial culture, into three subvariants (II)A, (II)B and (II)C. The plasmid profiles of rough S. sonnei (R-forms and phase II) completely coincide. The biosynthesis of the specific antigen of S. sonnei in phase I can be determined by smaller derivatives obtained from large plasmid pSS120 by deletion (e.g., by a plasmid with a molecular weight of about 80 MD, such as plasmid pSS80).

Animals↗
PubMedDate not supplied

Relationship of complement resistance and selected virulence factors in pathogenic avian Escherichia coli.

Complement resistance, antibiotic resistance profiles, and virulence profiles of 80 Escherichia coli isolates from the intestines of normal chickens (40 isolates) and chickens diagnosed as having colisepticemia (40 isolates) were compared. Differences were observed between the two groups for antibiotic resistance, siderophore production, presence of type 1 pili, complement resistance, motility, and size of plasmids. The systemic isolates were more likely to have siderophores and type 1 pili, and to be complement-resistant and motile than were the intestinal isolates. No differences between the two groups were observed for colicin production. Further comparison of the 10 most complement-resistant isolates from the systemic group and 10 most complement-sensitive isolates from the intestinal group revealed a correlation between an isolate's resistance to complement and its ability to kill embryos, express type 1 pili, and be motile. Virulence of avian E. coli strains appears to be correlated with complement resistance and the interaction of this resistance with the ability to produce type 1 pili and be motile.

Animals↗
PubMed2005

Thymidine-dependent Staphylococcus aureus small-colony variants are associated with extensive alterations in regulator and virulence gene expression profiles.

Chronic airway infection is a hallmark of cystic fibrosis (CF) and many CF patients are infected persistently by Staphylococcus aureus. Thymidine-dependent trimethoprim-sulfamethoxazole (SXT)-resistant S. aureus small-colony variants (SCVs), often in combination with isogenic normal S. aureus phenotypes, are highly prevalent and persistent in airway secretions of CF patients due to long-term SXT therapy (B. Kahl, M. Herrmann, A. S. Everding, H. G. Koch, K. Becker, E. Harms, R. A. Proctor, and G. Peters, J. Infect. Dis. 177:1023-1029, 1998). In this report, SCVs were compared to normal S. aureus by transcription analysis of important regulator (sigB, sarA, and agr) and virulence (alpha-hemolysin, hla, and protein A, spa) genes. Growth curve analyses revealed longer doubling times and lower final densities for SCVs than for normal strains. sigB activity was measured by transcription analysis of the sigB target gene asp23. For nearly all SCVs, expression of all regulators was decreased as assessed by asp23 reverse transcription-PCR for sigB and Northern analysis for sarA and agr. These results are in agreement with diminished hla signals in all SCVs and increased spa signals in 5 of 10 SCVs compared to the isogenic normal S. aureus. Both supplementation of SCVs with thymidine and activation of the agr quorum-sensing system by the supernatant of the isogenic normal strain reversed transcription to almost normal levels. In conclusion, multiple changes in growth characteristics and in regulator and virulence gene expression render SCVs less virulent and allow them to survive in the hostile environment present in the airways of CF patients, thereby illustrating adaptation of the bacteria during long-term persistence.

Bacterial Proteins↗
PubMed2006

Molecular evolution of typical enteropathogenic Escherichia coli: clonal analysis by multilocus sequence typing and virulence gene allelic profiling.

Enteropathogenic Escherichia coli (EPEC) infections are a leading cause of infantile diarrhea in developing nations. Typical EPEC isolates are differentiated from other types of pathogenic E. coli by two distinctive phenotypes, attaching effacement and localized adherence. The genes specifying these phenotypes are found on the locus of enterocyte effacement (LEE) and the EPEC adherence factor (EAF) plasmid. To describe how typical EPEC has evolved, we characterized a diverse collection of strains by multilocus sequence typing (MLST) and performed restriction fragment length polymorphism (RFLP) analysis of three virulence genes (eae, bfpA, and perA) to assess allelic variation. Among 129 strains representing 20 O-serogroups, 21 clonal genotypes were identified using MLST. RFLP analysis resolved nine eae, nine bfpA, and four perA alleles. Each bfpA allele was associated with only one perA allele class, suggesting that recombination has not played a large role in shuffling the bfpA and perA loci between separate EAF plasmids. The distribution of eae alleles among typical EPEC strains is more concordant with the clonal relationships than the distribution of the EAF plasmid types. These results provide further support for the hypothesis that the EPEC pathotype has evolved multiple times within E. coli through separate acquisitions of the LEE island and EAF plasmid.

Adhesins, Bacterial↗
PubMed1985

Enzymatic and acidic sensitivity profiles of selected virulent and attenuated transmissible gastroenteritis viruses of swine.

This study identifies the in vitro differences (markers) between virulent and attenuated transmissible gastroenteritis (TGE) viruses. Exposure of virulent Miller strain and attenuated Purdue strain TGE viruses to a spectrum of acidities indicated that the Miller strain was more stable at pH 2. Acidities at or above pH 3 did not reduce viral infectivity of either strain. When virulent and attenuated viruses were exposed to gastric fluids of either fed or fasted swine, there was a similar degree of sensitivity. Carboxypeptidase B, alpha-amylase, and alkaline phosphatase present in porcine small intestinal fluids did not cause a significant difference in sensitivity between virulent and attenuated virus isolates. The digestive enzymes: trypsin, alpha-chymotrypsin, pancreatin, peptidase, and carboxypeptidase A did not (or only slightly) inactivate virulent Miller strain TGE virus, but greatly reduced infectivity of attenuated viruses (Purdue strain and TGE vaccine virus isolates). The attenuated strains were significantly more sensitive to small intestinal fluids from both fasted and fed adult swine. Differential sensitivities between virulent and attenuated TGE viruses to digestive fluids from stomach and small intestine further substantiate the notion of differential susceptibility to small intestinal proteases as a correlate of viral virulence.

Alkaline Phosphatase↗
PubMed2005

Transcriptional profiles of regulatory and virulence factors of Staphylococcus aureus of bovine origin: oxygen impact and strain-to-strain variations.

Staphylococcus aureus is responsible for a large panel of infections in humans and animals. In cows, S. aureus provokes chronic intramammary infections. Little information is available about the regulation of virulence factors in bovine isolates. Moreover, oxygenation, which is low in an inflamed mammary gland, could play an important role during the infectious process. We investigated the impact of oxygen on regulatory and virulence factors transcription for three S. aureus bovine isolates cultivated in CYPG medium into a fermentor under moderate oxygenation or low oxygenation. A selective panel of regulatory factors and virulence factors was studied through their mRNA profiles by real-time PCR according to growth phases and oxygenation. RNAIII, rot and sarR genes, for the regulatory factors, and asp23 and cflA genes, for the virulence factors, were strongly expressed, whatever the oxygenation and the strains. Under low oxygenation, whatever the strain, an enhanced expression of srr, clfA and spa genes was detected. Some regulators such as sae, sarA and sigB were differentially transcribed according to the strain and the oxygenation condition. This study sustains the complexity of S. aureus genes global regulation and suggests the coexistence of different pathways that can be activated depending on the strain and the oxygen availability.

Animals↗
PubMed2002

Antibiotic resistance, virulence gene, and molecular profiles of Shiga toxin-producing Escherichia coli isolates from diverse sources in Calcutta, India.

Antibiotic resistance, virulence gene, and molecular profiles of Shiga toxin-producing Escherichia coli (STEC) non-O157 strains isolated from human stool samples, cow stool samples, and beef samples over a period of 2 years in Calcutta, India, were determined. Resistance to one or more antibiotics was observed in 49.2% of the STEC strains, with some of the strains exhibiting multidrug resistance. The dominant combinations of virulence genes present in the strains studied were stx(1) and stx(2) (44.5% of strains) and stx(1), stx(2), and hlyA (enterohemorrhagic E. coli hemolysin gene) (19% of strains). Only 6.4% of the STEC strains harbored eae. The diversity of STEC strains from various sources was assessed by random amplification of polymorphic DNA (RAPD). STEC strains that gave identical or nearly similar DNA fingerprints in RAPD-PCR and had similar virulence genotypes were further characterized by pulsed-field gel electrophoresis (PFGE). Identical RAPD and PFGE profiles were observed in four sets of strains, with each set comprising two strains. There was no match in the RAPD and PFGE profiles between strains of STEC isolated from cows and those isolated from humans. It appears that the clones present in bovine sources are not transmitted to humans in the Calcutta setting although these strains showed evolutionary relatedness. Maybe for this reason, STEC has still not become a major problem in India.

Animals↗
PubMed2006

Genes for the majority of group a streptococcal virulence factors and extracellular surface proteins do not confer an increased propensity to cause invasive disease.

BACKGROUND: The factors behind the reemergence of severe, invasive group A streptococcal (GAS) diseases are unclear, but it could be caused by altered genetic endowment in these organisms. However, data from previous studies assessing the association between single genetic factors and invasive disease are often conflicting, suggesting that other, as-yet unidentified factors are necessary for the development of this class of disease. METHODS: In this study, we used a targeted GAS virulence microarray containing 226 GAS genes to determine the virulence gene repertoires of 68 GAS isolates (42 associated with invasive disease and 28 associated with noninvasive disease) collected in a defined geographic location during a contiguous time period. We then employed 3 advanced machine learning methods (genetic algorithm neural network, support vector machines, and classification trees) to identify genes with an increased association with invasive disease. RESULTS: Virulence gene profiles of individual GAS isolates varied extensively among these geographically and temporally related strains. Using genetic algorithm neural network analysis, we identified 3 genes with a marginal overrepresentation in invasive disease isolates. Significantly, 2 of these genes, ssa and mf4, encoded superantigens but were only present in a restricted set of GAS M-types. The third gene, spa, was found in variable distributions in all M-types in the study. CONCLUSIONS: Our comprehensive analysis of GAS virulence profiles provides strong evidence for the incongruent relationships among any of the 226 genes represented on the array and the overall propensity of GAS to cause invasive disease, underscoring the pathogenic complexity of these diseases, as well as the importance of multiple bacteria and/or host factors.

Humans↗
PubMed2004

Heterogeneity among virulence and antimicrobial resistance gene profiles of extraintestinal Escherichia coli isolates of animal and human origin.

Extraintestinal pathogenic Escherichia coli (ExPEC) isolates collected from different infected animals and from human patients with extraintestinal infections in 2001 were characterized for their phenotypic and genotypic antimicrobial resistance profiles, genotypes, and key virulence factors. Among the 10 antimicrobial agents tested, resistance to ampicillin, tetracycline, and sulfonamides was most frequent. Multiresistant strains were found in both the animal and the human groups of isolates. Resistance gene distribution was assessed by colony hybridization. Similar antibiotic resistance patterns could be observed in the animal and the human isolates. Although some resistance genes, such as bla(TEM), sulI, and sulII, were equally represented in the animal and human ExPEC isolates, differences in the distributions of tetracycline [tet(D)], chloramphenicol (catI, catIII, and floR), and trimethoprim (dhfrI, dhfrV, dhfrVII, and dhfrXIII) resistance genes were observed between the animal and the human isolates. Approximately one-third of the ExPEC isolates possessed a class 1 integron. The four major different variable regions of the class 1 integron contained aminoglycoside (aadA1, aadA2, aadA5, and aadA6) and/or trimethoprim (dhfrIb, dhfrXII, and dhfrXVII) resistance genes. The ExPEC strains belonged to different phylogenetic groups, depending on their host origin. Strains isolated from animal tissues belonged to either a commensal group (group A or B1) or a virulent group (group B2 or D), while the majority of the human isolates belonged to a virulent group (group B2 or D). Although the limited number of isolates evaluated in the present study prevents firm epidemiological conclusions from being made, on a more global scale, these data demonstrate that extraintestinal isolates of E. coli can possess relatively distinct intra- and intergroup resistance gene profiles, with animal isolates presenting a more heterogeneous group than human isolates.

Animals↗
PubMed2005

Virulence factors of septicemic Escherichia coli strains.

Extraintestinal pathogenic Escherichia coli strains (ExPEC) are the cause of a diverse spectrum of invasive human and animal infections, often leading to septicemia. This review deals with the virulence genes of septicemic ExPEC strains. We discuss the meaning of a virulence gene and survey the genomic, genetic and physiological studies on these strains. Apparently, there are a few virulence factors, which are conserved in the septicemic strains, implying that they are essential for the infection. For the other virulence-related genes a high level of diversity is observed, demonstrating that all stages of the infection can be mediated by a number of alternative virulence factors. The variable profile of virulence genes in septicemic E. coli strains, as well as a prevalence of mobility-related sequences point out the existence of a "mix and match" combinatorial system.

Adhesins, Escherichia coli↗
PubMed2026

Prevalence, genomic characterization, and biofilm-forming capacity of extended-spectrum β-lactamase-producing Escherichia coli from faecal samples of broiler chickens in Jinan City, China.

The emergence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in food animals threatens both veterinary and human medicine by compromising critically important antimicrobials. This study characterized the prevalence, antimicrobial resistance profiles, molecular epidemiology, and virulence attributes of ESBL-producing E. coli isolated from broiler farms in Jinan City, China. From 600 faecal samples, 537 E. coli isolates were recovered (89.5 % isolation rate), with 71 (13.2 %) identified as ESBL producers. Antimicrobial susceptibility testing revealed markedly more severe resistance among ESBL-producing isolates, with complete ampicillin resistance (100 %) and high-level resistance to sulfamethoxazole/trimethoprim (94.37 %), streptomycin (87.32 %), chloramphenicol (78.87 %), and tetracycline (70.42 %). Resistance to extended-spectrum cephalosporins cefuroxime and ceftriaxone reached 43.66 % and 36.62 %, respectively, while amoxicillin/clavulanic acid susceptibility declined to 61.97 %. Whole-genome sequencing identified blaCTX-M-55 (29.58 %) as the predominant ESBL genotype, followed by blaCTX-M-64 (23.94 %), blaCTX-M-15 (19.71 %), blaCTX-M-14 (12.68 %), and blaCTX-M-65 (9.86 %). The plasmid-mediated colistin resistance gene mcr-1 was detected in 25.35 % of ESBL-producing isolates, indicating a substantial reservoir of last-resort antibiotic resistance determinants, though physical linkage between mcr-1 and ESBL-encoding genes remains undetermined due to short-read sequencing limitations. Multilocus sequence typing revealed ST117 (18.3 %) as the predominant sequence type, associated mainly with serogroup O78 (25.4 %). Virulence gene profiling demonstrated high prevalence of the serum survival gene iss (85.9 %), commonly associated with avian pathogenic E. coli, though avian pathogenicity was not experimentally confirmed. Notably, 90.14 % of ESBL-producing isolates demonstrated biofilm-forming capacity, with 16.90 % classified as strong biofilm producers forming mature, mushroom-shaped microcolonies. These findings demonstrate that broiler chickens in the sampled Jinan farms constitute a significant reservoir of multidrug-resistant, biofilm-forming ESBL-producing E. coli harboring clinically relevant genotypes, including mcr-1. The predominance of ST117, reported in both poultry and human clinical settings, along with extensive co-resistance profiles, underscores the value of integrated surveillance and antimicrobial stewardship in poultry production, though direct zoonotic transmission evidence requires further comparative genomic and epidemiological investigation.

Antimicrobial resistance↗
PubMed1992

Low-passage-associated proteins of Borrelia burgdorferi B31: characterization and molecular cloning of OspD, a surface-exposed, plasmid-encoded lipoprotein.

Borrelia burgdorferi, the causative agent of Lyme disease, loses its ability to infect and cause disease in mammalian hosts after repeated in vitro passage. To identify proteins preferentially expressed by the low-passage strain and thus representing potential virulence factors, the polypeptide profiles of virulent, low-passage and nonvirulent, high-passage forms of B. burgdorferi B31 were compared by nonequilibrium pH gradient two-dimensional gel electrophoresis. Four low-passage-associated proteins with relative molecular masses (M(r)s) of 35,000, 28,000, 24,000, and 20,000 were identified. Of these, the 28- and 35-kDa polypeptides were not expressed in detectable quantities in the high-passage B31 strain, whereas the 24- and 20-kDa proteins were present in reduced quantities. All four of these proteins were lipoproteins, as determined by labelling with [3H]palmitate. The abundant 28-kDa component, called outer surface protein D (OspD), is surface exposed on the basis of its proteolysis during treatment of intact organisms with proteinase K. The ospD gene is located on a 38-kb linear plasmid present in seven of nine low-passage strains of B. burgdorferi examined but absent in most high-passage, nonvirulent strains tested. Molecular cloning and sequence analysis of the ospD gene locus revealed an open reading frame encoding a 28,436-Da polypeptide with a putative signal peptidase II leader sequence. An unusual feature of the region upstream of the gene was the presence of seven contiguous, direct repeats of a 17-bp sequence that includes consensus -35 and -10 transcription initiation signals; however, only one transcription initiation site was active as determined by primer extension analysis. Further study of these and other polypeptides associated with low-passage strains may lead to identification of B. burgdorferi gene products required for infection and pathogenesis in mammalian hosts.

Amino Acid Sequence↗
PubMed2002

Molecular characterization of a serotype O121:H19 clone, a distinct Shiga toxin-producing clone of pathogenic Escherichia coli.

Most illnesses caused by Shiga toxin-producing Escherichia coli (STEC) have been attributed to E. coli serotype O157:H7, but non-O157 STEC infections are now increasingly recognized as public health problems worldwide. The O121:H19 serotype is being isolated more frequently from clinical specimens and has been implicated in one waterborne outbreak. We used multilocus virulence gene profiling, a PCR-based assay, to characterize the virulence gene content of 24 isolates of serotype O121:H19 and nonmotile variants. We also performed multilocus enzyme electrophoresis and multilocus sequencing to establish the clonal relatedness of O121 isolates and to elucidate the relationship of O121 to common STEC clones. The 24 isolates were found to represent a single bacterial clone, as there was no allelic variation across 18 enzyme loci among the isolates. The complete nucleotide sequence of the intimin gene differed by four substitutions from that of the epsilon (Int- epsilon ) allele of O103:H2 strain PMK5. The typical O121 virulence gene profile was similar to the profiles of enterohemorrhagic E. coli (EHEC) clones of E. coli: it included a Shiga toxin 2 gene (stx(2)), two genes on the EHEC plasmid (toxB and ehxA), and the gene encoding intimin (eae). Despite the similarities, putative virulence genes distributed on O islands-large chromosomal DNA segments present in the O157:H7 genome-were useful for discriminating among STEC serotypes and the O121:H19 clone had a composite profile that was distinct from the profiles of the other major EHEC clones of pathogenic E. coli. On the basis of sequencing analysis with 13 housekeeping genes, the O121:H19 clone did not fall into any of the four classical EHEC and enteropathogenic E. coli groups but instead was closely related to two eae-negative STEC strains.

Adhesins, Bacterial↗
PubMed2026

A rapid molecular assay for the detection of hypervirulent Klebsiella pneumoniae in the context of antimicrobial resistance surveillance.

Hypervirulent Klebsiella pneumoniae (hvKP) represents an emerging clinical and public-health concern, particularly as hypervirulence increasingly converges with multidrug resistance. Current diagnostic approaches rely on phenotypic assays, such as the string test, or on whole-genome sequencing (WGS), both of which have limitations in specificity, turnaround time, standardization, and feasibility for routine surveillance. To address this gap, we developed a multiplex real-time PCR assay targeting key hvKP-associated virulence loci, including siderophore systems, hypermucoviscosity regulators, and additional markers linked to invasive potential. The assay was evaluated on 110 K. pneumoniae clinical isolates and 9 positive blood cultures, using WGS and the string test as comparators. The molecular panel demonstrated high concordance with WGS for principal virulence determinants, correctly identifying all high-virulence (score 4) profiles, and most intermediate profiles. Against WGS, the assay yielded a sensitivity of 82% and a specificity of 73%; performance against the string test was 96% and 87%, respectively. Direct testing from blood culture pellets yielded results consistent with both WGS and DNA-based PCR for the limited number of targets detected, supporting the technical feasibility of this approach. However, broader validation is needed to confirm performance in this specimen type. Overall, this multiplex PCR assay provides a targeted molecular screening approach for the rapid identification of hvKP-associated virulence profiles. Its agreement with genomic data supports its potential utility as an accessible complement to WGS for hvKP surveillance, although further workflow optimization will be required before broader routine implementation.IMPORTANCEThe global emergence of hypervirulent and multidrug-resistant K. pneumoniae represents a major public-health threat, as the convergence of virulence and antimicrobial resistance dramatically limits therapeutic options and increases the likelihood of severe, invasive, and potentially untreatable infections. Rapid identification of essential virulence determinants is therefore critical for timely clinical management and for preventing onward transmission. However, current diagnostic approaches are either insufficiently sensitive or require substantial resources, limiting their routine use. By providing a rapid and targeted molecular assay capable of detecting the principal loci associated with hypervirulent K. pneumoniae and by demonstrating the preliminary feasibility of its use directly on blood culture pellets previously identified as Klebsiella spp. by MALDI-TOF MS, this work provides a pragmatic approach for early virulence profiling. Implementation of such assays can significantly enhance epidemiological surveillance, support tailored patient management, and reduce the spread of high-risk K. pneumoniae lineages in both community and healthcare environments.

Klebsiella pneumoniae↗
PubMed1992

Isolation of two Giardia lamblia (WB strain) clones with distinct surface protein and antigenic profiles and differing infectivity and virulence.

To determine the relationship between antigenic profiles and pathogenicity among Giardia lamblia clones (WB strain), trophozoites were cloned by the technique of limiting dilution. The phenotype of each clone was determined by an indirect immunofluorescence test using a polyclonal rabbit anti-G. lamblia trophozoite serum made against the parent strain. Two clones were chosen for further studies: a highly fluorescent clone, F+, in which more than 95% of the trophozoites fluoresced, and a low-fluorescence clone, F-, in which fewer than 5% fluoresced. Sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis and enzyme-linked immunotransfer blot studies of the membrane fractions of the two clones and parent strain revealed differences in both the total protein and antigenic profiles. A serum cytotoxicity test with the polyclonal serum showed that the F+ clones were more susceptible to immobilization and killing, while the majority of cells of the F- clones were resistant to such killing. Assessment of the infectivity of the two clones in the Mongolian gerbil animal model indicated that the F- clone more readily initiated infections, produced more cysts, had a higher intestinal trophozoite load, and produced a more severe clinical syndrome, while the F+ clone was less phenotypically stable in vivo and in some cases took longer to be cleared from the intestine.

Animals↗
PubMed1990

Babesia bovis: evidence for selection of subpopulations during attenuation.

DNA probes were used to detect variation in subpopulations of virulent and serially passaged Babesia bovis. Two distinct patterns were evident after hybridization to genomic DNA; the first was a basic profile typical of virulent B. bovis and the second, a more variable array, was characteristic of B. bovis after various stages of attenuation. Tick transmission of avirulent B. bovis causes reversion to the virulent genomic pattern, suggesting that selective enrichment of a small residual subpopulation caused reversion to a virulent profile of subpopulations. Certain genomic fragments, predominant in either virulent or avirulent parasite forms, are putative "markers" or actual elements responsible for these biological characteristics.

Animals↗