Brazilian purpuric fever identified in a new region of Brazil. The Brazilian Purpuric Fever Study Group

Emergence and disappearance of a virulent clone of Haemophilus influenzae biogroup aegyptius, cause of Brazilian purpuric fever

SUMMARY

In 1984, children presented to the emergency department of a hospital in the small town of Promissão, São Paulo State, Brazil, with an acute febrile illness that rapidly progressed to death. Local clinicians and public health officials recognized that these children had an unusual illness, which led to outbreak investigations conducted by Brazilian health officials in collaboration with the U.S. Centers for Disease Control and Prevention. The studies that followed are an excellent example of the coordinated and parallel studies that are used to investigate outbreaks of a new disease, which became known as Brazilian purpuric fever (BPF). In the first outbreak investigation, a case-control study confirmed an association between BPF and antecedent conjunctivitis but the etiology of the disease could not be determined. In a subsequent outbreak, children with BPF were found to have bacteremia caused by Haemophilus influenzae biogroup aegyptius (H. aegyptius), an organism previously known mainly to cause self-limited purulent conjunctivitis. Molecular characterization of blood and other isolates demonstrated the clonal nature of the H. aegyptius strains that caused BPF, which were genetically distant from the diverse strains that cause only conjunctivitis. This led to an intense effort to identify the factors causing the unusual invasiveness of the BPF clone, which has yet to definitively identify the virulence factor or factors involved. After a series of outbreaks and sporadic cases through 1993, no additional cases of BPF have been reported.

Public health challenges and emerging diseases: the case of São Paulo

The author discusses the challenges posed by emerging infectious diseases in 100 years of public health in the state of São Paulo, Brazil. With an advanced and organized public health system, São Paulo responded to the emergence of infectious diseases by creating research institutions and control programs. The late 19th century witnessed the first modern research institution in microbiology, in response to the bubonic plague. A changing economy led to constant changes in ecosystems. The late 20th century presents a wide array of both emerging and rapidly changing infectious diseases. The present situation calls for creative solutions. Ecosystem analysis and more agile epidemiological surveillance are seen as the best alternatives.

Evolution of the major pilus gene cluster of Haemophilus influenzae

Haemophilus influenzae is a ubiquitous colonizer of the human respiratory tract and causes diseases ranging from otitis media to meningitis. Many H. influenzae isolates express pili (fimbriae), which mediate adherence to epithelial cells and facilitate colonization. The pilus gene (hif) cluster of H. influenzae type b maps between purE and pepN and resembles a pathogenicity island: it is present in invasive strains, absent from the nonpathogenic Rd strain, and flanked by direct repeats of sequence at the insertion site. To investigate the evolution and role in pathogenesis of the hif cluster, we compared the purE-pepN regions of various H. influenzae laboratory strains and clinical isolates. Unlike Rd, most strains had an insert at this site, which usually was the only chromosomal locus of hif DNA. The inserts are diverse in length and organization: among 20 strains, nine different arrangements were found. Several nontypeable isolates lack hif genes but have two conserved open reading frames (hicA and hicB) upstream of purE; their inferred products are small proteins with no data bank homologs. Other isolates have hif genes but lack hic DNA or have combinations of hif and hic genes. By comparing these arrangements, we have reconstructed a hypothetical ancestral genotype, the extended hif cluster. The hif region of INT1, an invasive nontypeable isolate, resembles the hypothetical ancestor. We propose that a progenitor strain acquired the extended cluster by horizontal transfer and that other variants arose as deletions. The structure of the hif cluster may correlate with colonization site or pathogenicity.

Human microvascular endothelial tissue culture cell model for studying pathogenesis of Brazilian purpuric fever

Brazilian purpuric fever (BPF) is a fulminant pediatric disease characterized by fever, with rapid progression to purpura, hypotensive shock, and death. All known BPF cases have been caused by three clones of Haemophilus influenzae biogroup aegyptius and have occurred in either Brazil or Australia. Using an immortalized line of human vascular endothelial cells, we developed an in vitro assay that identifies all known BPF-causing H. influenzae biogroup aegyptius strains (R. S. Weyant, F. D. Quinn, E. A. Utt, M. Worley, V. G. George, F. J. Candal, and E. W. Ades, J. Infect. Dis. 169:430-433, 1994). With multiplicities of infection (MOIs) as low as one bacterium per 1,000 tissue culture cells, BPF-associated strains produce a unique cytotoxic effect in which the tissue culture cells detach and aggregate in large floating masses after 48 h of incubation. In this study, using a BPF-associated strain and a non-BPF-associated control, we demonstrated that strains which produce the cytotoxic phenotype were able to replicate intracellularly whereas non-BPF-associated strains, with MOIs of > or = 1,000 did not replicate and did not produce the phenotype. We also showed that this phenotype is not caused by the activity of an endotoxin or the release of some other compound from the bacterial cell, since neither gamma irradiation-killed whole BPF clone bacteria nor bacterial cell fractions at MOIs of > 1,000 produced the cytotoxic effect. Furthermore, bacteria in numbers equal to MOIs of > 1,000 treated with chloramphenicol did not produce the cytotoxic phenotype, suggesting a requirement for bacterial protein synthesis. In addition, viable bacteria separated from the tissue culture monolayer by a 0.2-micron-pore-size membrane also failed to produce the phenotype. The ability of the bacterium to invade, replicate, and produce the phenotype appears to be primarily parasite directed since phagocytosis, pinocytosis, and eukaryotic protein synthesis inhibitors, including cycloheximide, cytochalasin D, and methylamine, had no effect on the ability of the bacterium to invade and cause a cytotoxic response. Understanding the basic mechanisms involved in this tissue-destructive process should enhance our knowledge of the general pathogenesis of BPF.

Isolamento de Haemophiliis aegyptius associado à Febre Purpúrica Brasileira, de cloropídeos (Diptera) dos gêneros Hippelates e Liohippelates

O reconhecimento da Febre Purpúrica Brasileira (FPB), em 1984, originou uma série de estudos que revelaram uma correlação desta doença com conjuntivites causadas por Haemophiliis aegyptius. A associação do aumento de conjuntivites em crianças e a maior densidade populacional de cloropídeos do gênero Hippelates já havia sido verificada desde o século passado. Este fenômeno está relacionado ao tropismo que estes insetos apresentam pelos olhos, secreções e feridas de onde se alimentam. Embora haja evidências do papel destes cloropídeos na transmissão mecânica de conjuntivites bacterianas, o isolamento de Haemophilus aegyptius a partir dos mesmos, no seu habitat natural, ainda não havia sido verificado. No presente trabalho obtivemos o isolamento de cepas invasivas de Haemophilus aegyptius, associadas à FPB, de duas coleções de cloropídeos, classificados como Liohippelates peruanus e uma espécie nova, Hippelates neoproboscideus, coletados ao redor dos olhos de crianças com conjuntivite.

Febre purpúrica brasileira, virulência em modelo animal do Haemophilus Aegyptius (H. influenzae biogrupo aegyptius)

Febre Purpúrica Brasileira (FPB) é causada por cepas invasoras de Haemophilus aegyptius (H. influenzae biogrupo aegyptius, Hae). Estas cepas invasoras foram diferenciadas de cepas de Hae associadas apenas a conjuntivites (cepas não invasoras) através de marcadores moleculares específicos. Modelo de ratos recém nascidos depletados de complemento foi aplicado ao estudo de cepas de Hae, associadas e não associadas a FPB, com o objetivo de se caracterizar seus potenciais de virulência. Com dose infectante de 10(5) células, as cepas invasoras causaram bacteriemia em 80-100% dos ratos inoculados,.e a magnitude da bacteriemia variou de 10(2,5±0,49) a > 10(4,69) ufc/ml de sangue. Usando a mesma dose infectante as cepas controles não causaram bacteriemia frequente (0 a 50%) e a magnitude variou de 0 a 10(3,69±0,53) ufc/ml de sangue. As doses infectantes capazes de causar bacteriemia em 50% dos ratos inoculados (DB50%) para as cepas invasoras de Hae variaram de < 10³ a 10(4,2) bactérias, enquanto que para as cepas não invasoras, as DB50% variaram de 10(6,2) a > 10(7,3) bactérias. Imunização passiva com antissoros produzidos com cepas invasoras demonstrou que os ratos foram protegidos das bacteriemias causadas pelas cepas homólogas, mas não da infecção causada pela cepa heteróloga. Comparando a bacteriemia causada pelas cepas de Hae com a bacteriemia causada pelo H. influenzae b, cepa Eagan (Hib), foi demonstrado o maior potencial de invasibilidade de Hib. Este modelo animal demonstrou ser útil para esclarecer o maior potencial de virulência das cepas invasoras de Hae.