Urogenital, maternal and neonatal isolates of Haemophilus influenzae: identification of unusually virulent serologically non-typable clone families and evidence for a new Haemophilus species

Epidemiology of Invasive Nontypeable Haemophilus influenzae Disease-United States, 2008-2019

BACKGROUND

Nontypeable Haemophilus influenzae (NTHi) is the most common cause of invasive H. influenzae disease in the United States (US). We evaluated the epidemiology of invasive NTHi disease in the US, including among pregnant women, infants, and people with human immunodeficiency virus (PWH).

METHODS

We used data from population- and laboratory-based surveillance for invasive H. influenzae disease conducted in 10 sites to estimate national incidence of NTHi, and to describe epidemiology in women of childbearing age, infants aged ≤30 days (neonates), and PWH living in the surveillance catchment areas. H. influenzae isolates were sent to the Centers for Disease Control and Prevention for species confirmation, serotyping, and whole genome sequencing of select isolates.

RESULTS

During 2008-⁠2019, average annual NTHi incidence in the US was 1.3/100 000 population overall, 5.8/100 000 among children aged <1 year, and 10.2/100 000 among adults aged ≥80 years. Among 225 reported neonates with NTHi, 92% had a positive culture within the first week of life and 72% were preterm. NTHi risk was 23 times higher among preterm compared to term neonates, and 5.6 times higher in pregnant/postpartum compared to nonpregnant women. More than half of pregnant women with invasive NTHi had loss of pregnancy postinfection. Incidence among PWH aged ≥13 years was 9.5 cases per 100 000, compared to 1.1 cases per 100 000 for non-PWH (rate ratio, 8.3 [95% confidence interval, 7.1-9.7]; P < .0001).

CONCLUSIONS

NTHi causes substantial invasive disease, especially among older adults, pregnant/postpartum women, and neonates. Enhanced surveillance and evaluation of targeted interventions to prevent perinatal NTHi infections may be warranted.

Haemophilus seminalis sp. nov., isolated from human semen

Two Haemophilus-like isolates with similar biochemical characteristics, designated strains SZY H1^T and SZY H2, were isolated from human semen specimens. Cells were Gram-negative, non-motile, non-acid-fast, pleomorphic rods or coccobacilli. The major fatty acids (>10 %) were C_{16 : 0}, C_{14 : 0}, iso-C_{16 : 0} and/or C_{14 : 0} 3-OH and C_{16 : 1} ω6c and/or C_{16 : 1} ω7c. The polar lipids were determined to be phosphatidylethanolamine, phosphatidylglycerol, an unidentified phospholipid, an unidentified aminophospholipid, two unidentified polar lipids and four unidentified aminolipids. The major polyamine was found to be cadaverine. The near-full-length (1462 nt) 16S rRNA gene sequences analysis showed the two isolates were nearly identical (>99.8 %), and closely matched Haemophilus haemolyticus ATCC 33390^T with 98.9-99.1 % sequence similarities. Phylogenetic analysis based on 16S rRNA gene sequences and concatenation of 30 protein markers also revealed that the isolates clustered together with H. haemolyticus ATCC 33390^T, and formed a distinct lineage well separated from the other members of the genus Haemophilus. Further, the average nucleotide identity values between the two isolates and their related species were below the established cut-off values for species delineation (95 %). Based on these findings, the two isolates are considered to represent a new species of the genus Haemophilus, for which name Haemophilus seminalis sp. nov. is proposed. The type strain is SZY H1^T (=NBRC 113782^T=CGMCC 1.17137^T).

Identification and Characterization of "Haemophilus quentini" Strains Causing Invasive Disease in Ontario, Canada (2016 to 2018)

Haemophilus influenzae is a well-established human pathogen capable of causing a range of respiratory and invasive diseases. Since the 1970s, it has been observed that a nontypeable cryptic genospecies of H. influenzae, most often biotype IV, has been associated with the genitourinary tracts of females and with invasive neonatal infections. This distinct genospecies has been provisionally named "Haemophilus quentini" Here, we report seven cases of invasive H. quentini disease in patients from Ontario, Canada, over a 2-year period. Significantly, while most reports of invasive disease with H. quentini to date have been in neonates, we observed five cases in adults (three in women of childbearing age and two in seniors) as well as two in neonates. Identification of H. quentini is challenging and was not possible for frontline laboratories, requiring work at the reference laboratory level. We describe in detail the biochemical results, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-Tof MS) results, and PCR results with several targets, including the 16S rRNA gene and multilocus sequence typing (MLST) genes, for the seven Ontario H. quentini isolates and several controls. Our data, combined with those of other publications, support the fact that H. quentini is distinct from H. influenzae and Haemophilus haemolyticus This organism is recognized as a pathogen of neonates, but we hypothesize that it may be underrecognized as an important pathogen in adults as well, particularly pregnant women. By sharing the detailed descriptions of these isolates, we hope to enable other laboratories to better identify H. quentini so that the true prevalence of this organism and disease can be explored.

Disseminated "Haemophilus quentini" infection in a patient with multiple myeloma - a case report and review of the literature

We describe a case report of a 56-year-old male with undiagnosed multiple myeloma who had severe sepsis associated with pneumonia, meningitis, polyarthritis, and osteomyelitis related to invasive "Haemophilus quentini" infection. The genus was misidentified as H. influenzae by the common bacterial identification systems including newly introduced syndromic PCR-based methods. We review the epidemiological, clinical, and laboratory aspects of this rare, cryptic species of Haemophilus.

First report of neonatal bacteremia caused by "Haemophilus quentini" diagnosed by 16S rRNA gene sequencing, Italy

We report the first case of neonatal bacteremia caused by a "Haemophilus quentini" isolate in Italy. The isolate was differentiated from H. influenzae by 16S rRNA sequencing and was characterized by comparison with the wild-type "H. quentini" CCUG 36167. Both isolates carried substitutions in penicillin-binding protein 3 but were susceptible to aminopenicillins.

Classification, identification, and clinical significance of Haemophilus and Aggregatibacter species with host specificity for humans

The aim of this review is to provide a comprehensive update on the current classification and identification of Haemophilus and Aggregatibacter species with exclusive or predominant host specificity for humans. Haemophilus influenzae and some of the other Haemophilus species are commonly encountered in the clinical microbiology laboratory and demonstrate a wide range of pathogenicity, from life-threatening invasive disease to respiratory infections to a nonpathogenic, commensal lifestyle. New species of Haemophilus have been described (Haemophilus pittmaniae and Haemophilus sputorum), and the new genus Aggregatibacter was created to accommodate some former Haemophilus and Actinobacillus species (Aggregatibacter aphrophilus, Aggregatibacter segnis, and Aggregatibacter actinomycetemcomitans). Aggregatibacter species are now a dominant etiology of infective endocarditis caused by fastidious organisms (HACEK endocarditis), and A. aphrophilus has emerged as an important cause of brain abscesses. Correct identification of Haemophilus and Aggregatibacter species based on phenotypic characterization can be challenging. It has become clear that 15 to 20% of presumptive H. influenzae isolates from the respiratory tracts of healthy individuals do not belong to this species but represent nonhemolytic variants of Haemophilus haemolyticus. Due to the limited pathogenicity of H. haemolyticus, the proportion of misidentified strains may be lower in clinical samples, but even among invasive strains, a misidentification rate of 0.5 to 2% can be found. Several methods have been investigated for differentiation of H. influenzae from its less pathogenic relatives, but a simple method for reliable discrimination is not available. With the implementation of identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry, the more rarely encountered species of Haemophilus and Aggregatibacter will increasingly be identified in clinical microbiology practice. However, identification of some strains will still be problematic, necessitating DNA sequencing of multiple housekeeping gene fragments or full-length 16S rRNA genes.

The Haemophilus cryptic genospecies Cha adhesin has at least two variants that differ in host cell binding, bacterial aggregation, and biofilm formation properties

The Haemophilus cryptic genospecies (HCG) causes genital tract infections in pregnant and postpartum women and respiratory infections in neonates. The major surface adhesin in HCG is called Cha, which mediates bacterial adherence to cultured human epithelial cells. In this study, we report that there are two antigenically distinct variants of Cha, dubbed Cha1 and Cha2. These variants are encoded by the same genetic locus in diverse strains and have nearly identical N-terminal export and C-terminal surface anchoring domains but significantly different internal adhesive domains. Based on the comparison of derivatives of a laboratory strain of Haemophilus influenzae expressing either surface-associated Cha1 or surface-associated Cha2, Cha1 mediates a higher level of adherence to cultured human epithelial cells and Cha2 mediates a higher level of adherence to abiotic surfaces. We hypothesize that variation in the Cha1 and Cha2 internal region results in changes in binding specificity or binding affinity and may be associated with adaptation to different host environments during colonization and disease.

Population subdivision and the detection of recombination in non-typable Haemophilus influenzae

The disparity in diversity between unencapsulated (non-typable; NT) and encapsulated, serotypable Haemophilus influenzae (Hi) has been recognized for some time. It has previously been suggested that the wider diversity evidenced within NTHi compared with typable lineages may be due to different rates of recombination within the encapsulated and NT populations. To examine whether there is evidence for different levels of recombination within typable and NT lineages of Hi, we performed a statistical genetic analysis of 819 distinct genotypes of Hi to explore the congruence of serotype with population genetic clustering, and to identify patterns of recombination within the Hi population. We find that a significantly larger proportion of NT isolates show evidence of recombination, compared with typable isolates, and also that when admixture is present, the total amount of recombination per strain is greater within NT isolates, compared with the typable population. Furthermore, we demonstrate significant heterogeneity in the number of admixed individuals between NT lineages themselves, while such variation was not observed in typable lineages. This variability suggests that factors other than the presence of capsule are important determinants of recombination rate in the Hi population.

Genotypic and phenotypic characterization and clinical significance of 'Haemophilus quentini' isolated from the urinary tract of adult men

'Haemophilus quentini' has been proposed as the name for a distinct and homogeneous Haemophilus genospecies associated with urogenital tract and neonatal-related infections. Reports of 'H. quentini' isolation from adult men are rare and the disease potential in this population is unknown. We report six cases where 'H. quentini' was isolated from the genito-urinary tract in males. The isolation of 'H. quentini' during routine urine and urethral culture in adult men may aid in the determination of unresolved urethritis and possible urinary tract infections.

Identification of a novel trimeric autotransporter adhesin in the cryptic genospecies of Haemophilus

Haemophilus biotype IV strains belonging to the recently recognized Haemophilus cryptic genospecies are an important cause of maternal genital tract and neonatal systemic infections and initiate infection by colonizing the genital or respiratory epithelium. To gain insight into the mechanism of Haemophilus cryptic genospecies colonization, we began by examining prototype strain 1595 and three other strains for adherence to genital and respiratory epithelial cell lines. Strain 1595 and two of the three other strains demonstrated efficient adherence to all of the cell lines tested. With a stably adherent variant of strain 1595, we generated a Mariner transposon library and identified 16 nonadherent mutants. All of these mutants lacked surface fibers and contained an insertion in the same open reading frame, which encodes a 157-kDa protein designated Cha for cryptic haemophilus adhesin. Analysis of the predicted amino acid sequence of Cha revealed the presence of an N-terminal signal peptide and a C-terminal domain bearing homology to YadA-like and Hia-like trimeric autotransporters. Examination of the C-terminal 120 amino acids of Cha demonstrated mobility as a trimer on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the capacity to present the passenger domain of the Hia trimeric autotransporter on the bacterial surface. Southern analysis revealed that the gene that encodes Cha is conserved among clinical isolates of the Haemophilus cryptic genospecies and is absent from the closely related species Haemophilus influenzae. We speculate that Cha is important in the pathogenesis of disease due to the Haemophilus cryptic genospecies and is in part responsible for the apparent tissue tropism of this organism.

Presence of copper- and zinc-containing superoxide dismutase in commensal Haemophilus haemolyticus isolates can be used as a marker to discriminate them from nontypeable H. influenzae isolates

Respiratory isolates of Haemophilus haemolyticus are regularly misclassified as nontypeable (NT) Haemophilus influenzae due to an aberrant hemolytic reaction on blood agar, with implications for treatment. The presence of sodC or its cognate protein, copper-zinc superoxide dismutase, can distinguish respiratory isolates of H. haemolyticus from NT H. influenzae with 100% accuracy.

Reduced levofloxacin susceptibility and tetracycline resistance in a clinical isolate of Haemophilus quentini identified by 16S rRNA sequencing

This paper reports the first case of Haemophilus quentini bacteremia with reduced susceptibility to levofloxacin and resistance to nalidixic acid identified by 16S rRNA sequencing. There was an S 84 L substitution in gyrA and an S 84 I substitution in par C. The isolate had co-resistance to ampicillin (beta-lactamase positive) and tetracycline mediated by the tet(B) gene.

Typing of nonencapsulated haemophilus strains by repetitive-element sequence-based PCR using intergenic dyad sequences

Intergenic dyad sequences (IDS) are short repeated elements that have been described for several Haemophilus genomes and for only two other bacterial genera. We developed a repetitive-element sequence-based PCR using an IDS-specific primer as a typing method (IDS-PCR) for nonencapsulated Haemophilus strains and compared this technique with pulsed-field gel electrophoresis (PFGE) of DNA restricted with SmaI. IDS-PCR was rapid, easy to perform, and reproducible, with a high discriminatory capacity for nontypeable Haemophilus influenzae (NTHI) strains. The 69 NTHI strains tested generated 65 different banding patterns. Epidemiologically related strains gave similar or identical fingerprints, and all of the unrelated strains except two showed different patterns. These results were in agreement with those obtained by PFGE. For 20 genital strains usually identified as being biotype IV NTHI and belonging to a cryptic genospecies of Haemophilus with remarkable genetic homogeneity, four bands were significantly present and six bands were significantly absent from the fingerprints. The 20 strains were gathered in 11 closely related profiles, whereas PFGE provided no band when DNA was treated with SmaI. IDS-PCR improved the differentiation previously obtained within this species by ribotyping and multilocus enzyme electrophoresis. Our findings suggest that IDS-PCR is a rapid, reliable, and discriminatory method for typing NTHI strains and is currently the most efficient method for distinguishing strains within the cryptic genospecies of HAEMOPHILUS:

Fimbrial ghf gene cluster of genital strains of Haemophilus spp

We analyzed the LKP fimbrial gene clusters of six piliated strains of a cryptic genospecies of Haemophilus isolated from the genital tracts of adult patients (five strains) and from an infected neonate. In a group of 19 genital strains, LKP-like genes have been found in only these 6 strains. In addition to the ghfA, ghfD, and ghfE genes previously described, we characterized two genes, designated ghfB and ghfC, encoding the putative chaperone and assembly platform proteins. All six strains had a complete and unique LKP-like gene cluster consisting of the five genes ghfA to ghfE, homologous to genes hifA to hifE of Haemophilus influenzae. The sequences of the coding and intergenic regions of the ghf clusters of the six strains were remarkably homologous. Unlike hif clusters, which are inserted between purE and pepN, the ghf cluster was inserted between purK and pepN on the chromosome. Analysis of the flanking regions of the ghf cluster identified a large deletion, identical in the 5' end regions of all strains, including the whole purE gene and much of the purK gene. Ultrastructural observations, an attempt at enriching LKP fimbriae, and hemagglutination experiments demonstrated that none of the strains had LKP-type fimbriae. Nevertheless, reverse transcription (RT)-PCR showed that ghf genes were transcribed in four of the six strains. Sequencing of the intergenic ghfA-ghfB regions, including the ghf gene promoters, showed that the absence of transcripts in the remaining two strains was due to a decrease in the number of TA repeats (4 or 9 repeats rather than 10) between the -10 and -35 boxes of the two overlapping and divergent promoters. The other four strains, which had ghf transcripts, had the optimal 10 TA repeats (one strain) or 5 repeats associated with putative alternative -35 boxes (three strains). The absence of 10 repeated palindromic sequences of 44 or 45 nucleotides upstream of ghfB induces an increased instability of mRNA, as quantified by real-time RT-PCR, and may explain why the LKP fimbrial gene cluster is not expressed in these strains.

Active copper- and zinc-containing superoxide dismutase in the cryptic genospecies of Haemophilus causing urogenital and neonatal infections discriminates them from Haemophilus influenzae sensu stricto

The presence of active copper- and zinc-containing superoxide dismutase in isolates of the cryptic genospecies of Haemophilus, responsible for urogenital, neonatal, and mother-infant infections, can be used as a biochemical marker to discriminate them from H. influenzae sensu stricto strains.

Haemophilus influenzae septic abortion

BACKGROUND

Haemophilus influenzae septic abortion is typically caused by nontypeable strains of the organism. Furthermore, nontypeable species with a special affinity for the genital tract are the most frequent isolates encountered, and an ascending vaginal or cervical infection is often the suspected route of transmission.

CASE

A 39-year-old woman at 8 weeks gestation who underwent dilation, evacuation, and curettage for embryonic demise had clinical evidence for sepsis and isolation of a nontypeable, ampicillin resistant H. influenzae from blood cultures. Although an ascending vaginal infection was suspected, the route of transmission was not determined.

CONCLUSION

Nontypeable strains of. H. influenzae have demonstrated increased beta-lactamase activity, and ampicillin, formerly the treatment of choice, should be used only if isolate susceptibility is known.

Analysis of pilus adhesins from Haemophilus influenzae biotype IV strains

A subset of nontypeable Haemophilus influenzae (NTHI) biotype IV isolates from the human genital tract or from infected newborn infants forms a cryptic genospecies characterized by, among other features, the presence of peritrichous pili. The objective of this study was to determine the similarity of these pili to hemagglutinating, HifA- and HifE-containing pili expressed by respiratory H. influenzae isolates. For this analysis, the presence of hifA and hifE and their gene products in NTHI biotype IV strains was assessed, the binding of H. influenzae biotype IV strains to human epithelial cells was characterized, possible genital tissue tropism of these isolates was explored, and the role of HifA- and HifE-possessing pili in the adhesion of NTHI biotype IV strains to human epithelial cells was determined. None of the six biotype IV NTHI isolates tested agglutinated human red blood cells, nor could they be enriched for hemagglutinating variants. Although hifA, which encodes the major structural subunit of hemagglutinating pili, and hifE, which encodes the tip adhesin of hemagglutinating pili, were detected by PCR from six and five, respectively, of the six biotype IV strains tested, neither HifA nor HifE (the gene products of hifA and hifE) were detected in any of these strains by Western blot analysis using antisera that recognize HifA and HifE of respiratory strains. Transmission electron microscopy showed no surface pili on the two biotype IV H. influenzae isolates examined; strain 4162 containing an insertional mutation in hifA also showed no surface pili, whereas strain 1595 containing an insertional mutation in hifB showed pilus-like structures that were shorter and thicker than hemagglutinating pili of the respiratory strains AAr176 and M43. In enzyme-linked immunosorbent assays, biotype IV strains adhered to 16HBE14o(-) and HEp-2 cells of respiratory origin as well as to ME180 and HeLa cells of genital origin. This adherence was not pilus specific, however, as GM-1, a known pilus receptor analog, did not inhibit binding of biotype IV strains to ME180, HEp-2, or HeLa cells, and GM-1 inhibition of binding to 16HBE14o(-) cells did not correlate with the presence of hifE. While both nonpiliated variants and hifA and hifB (encoding the pilus chaperone) mutants of respiratory strain AAr176 showed reduced binding (64 to 87% of that of piliated AAr176) to 16HBE14o(-) and ME180 cells, hifA and hifB mutants of the biotype IV strains showed minimal reduction in binding to these cell lines (91 to 98% of that of wild-type strains). Thus, although biotype IV H. influenzae isolates of the cryptic genospecies possess the genes that code for HifA- and HifE-containing hemagglutinating pili, epithelial cell adherence exhibited by these strains is not mediated by expression of hemagglutinating pili.

Comparative genetic characterization of Listeria monocytogenes isolates from human and animal listeriosis cases

Listeria monocytogenes isolates from human sporadic and epidemic cases (n=119) and from animal cases (n=76) were characterized by automated ribotyping and PCR-restriction fragment length polymorphism (PCR-RFLP) typing of the virulence genes actA and hly. This combination of typing methods differentiated 39 distinctive strains, each reflecting a unique combination of ribotypes, hly and actA alleles. Simpson's index of discrimination indicated a high discriminatory ability of ribotyping for both animal (0.867) and human isolates (0.857), which was further increased by the addition of hly and actA typing (0.916 and 0.904, respectively). Ribotype and hly allele data were further used to group isolates into three genetically distinct lineages. Each lineage is composed of several ribotype fragment subsets, each of which contains multiple ribotypes characterized by common ribotype fragments. To determine whether certain clones of L. monocytogenes show indications for unique pathogenic potential or host specificity, frequency distributions for five genetic characteristics (i.e. lineage, ribotype, ribotype fragment subset and hly and actA allele) were calculated for isolates from animal cases, human epidemic cases and human sporadic cases. Lineage III isolates were found less frequently in human cases (1 of 119 isolates) than in animal cases (8 of 76 isolates; P=0.003). These results suggest the possibility of host specificity for non-primate mammals among lineage III strains. In addition, lineage I strains were found more frequently among human cases than among animal cases (P<0.001). Among the eight hly alleles observed, hly allele 1 was more common among human isolates as compared to animal isolates (P=0.002). We also identified one ribotype (DUP-1030) which was significantly more common among animal isolates (P=0.005) and one ribotype (DUP-1038; lineage I) which was significantly more common among human epidemic isolates as compared to human sporadic isolates (P<0.001). These findings confirm the presence of clonal groups of L. monocytogenes, which appear to be characterized by unique virulence or host specificity patterns. This study also establishes baseline data describing the genetic diversity of human and animal L. monocytogenes isolates which can be utilized in future surveillance programmes to track the emergence of new strains.

Use of multilocus enzyme electrophoresis to distinguish clinically important strains of Staphylococcus intermedius from the skin of dogs

AIMS

To use multilocus enzyme electrophoresis to determine the genetic structure of Staphylococcus intermedius from normal skin of dogs and those isolated from a variety of disease conditions and to distinguish clinically important strains in dogs.

METHODOLOGY

The diversity amongst 129 isolates of S intermedius from the skin and mucosa of 32 healthy dogs and 120 isolates from diseased sites in 120 individual dogs was examined using multilocus enzyme electrophoresis. Associations among ETs were examined to determine the diversity of isolates.

RESULTS

Twenty two ETs were distinguished comprising 21 containing isolates from diseased sites and 11 containing isolates from normal dogs. The majority of isolates (171 of 249; 69% were located in two ETs (ET1 and ET 4), that were not distinguishable phenotypically. ET 1 contained 94 isolates (54 isolates from healthy dogs and 40 isolates from diseased sites) and ET 4 contained 77 isolates (46 from healthy dogs and 31 isolates from diseased sites). Further, 77.5% of isolates from healthy dogs were present in ET 1 and ET 4 and 59% of isolates from diseased dogs belonged to the same two ETs. There was only a small difference in genetic diversity among isolates taken from healthy dogs (11 ETs; H = 0.182) and those isolates taken from clinical specimens from diseased dogs (21 ETs; H = 0.218). Of the 21 ETs from diseased sites, ET 16 contained all six isolates from Staphylococcal Scalded Skin Syndrome in racing Greyhounds.

CONCLUSIONS

The small difference in genetic diversity between isolates from the skin and mucosa of healthy dogs and isolates from various diseases, as well as the presence of the majority of isolates in two ETs, is consistent with the role of S intermedius as an opportunistic pathogen. The confinement of all Staphylococcal Scalded Skin Syndrome isolates within one ET is confirmation of this entity as a distinct disease of dogs.

Nucleotide sequences of genes coding for fimbrial proteins in a cryptic genospecies of Haemophilus spp. isolated from neonatal and genital tract infections

Nineteen isolates belonging to a cryptic genospecies of Haemophilus (referred to here as genital strains) isolated from genital tract infections (6 strains) and from neonatal infections (13 strains) were studied for fimbrial genes. Sixteen strains exhibit peritrichous fimbriae observed by electron microscopy. By PCR with primers corresponding to the extreme ends of the Haemophilus influenzae type b (Hib) hifA and hifD genes and Southern blotting, a hifA-like gene (named ghfA) and a hifD-like gene (named ghfD) were identified in 6 of the 19 strains. Five of these six strains were from the genital tracts of adults, and one was from a neonate. For each gene, the nucleotide sequence was identical for the six strains. A hifE-like gene (named ghfE) was amplified from only one of the 19 genital strains of Haemophilus, but the ghfE probe gave a signal in Southern hybridization with the five other strains positive for ghfA and ghfD. Therefore, these strains may carry a ghfE-like gene. The Hib fimbrial gene cluster is located between the purE and pepN genes as previously described. For the 13 genital Haemophilus strains that lack fimbrial genes, this region corresponds to a noncoding sequence. Another major fimbrial gene designated the fimbrin gene was previously identified in a nontypeable H. influenzae strain. A fimbrin-like gene was identified for all of our 19 genital strains. This gene is similar to the ompP5 gene of many Haemophilus strains. Therefore, other, unidentified genes may explain the piliation observed in electron microscopy on genital Haemophilus strains which do not possess LKP-like fimbrial genes. Fimbrial genes were significantly associated with strains isolated from the genital tract. They may confer on the strain the ability to survive in the genital tract.

Variable serum immunoglobulin G immune response to genetically distinct Eikenella corrodens strains coexisting in the human oral cavity

This study examined the variable serum immunoglobulin G (IgG) levels to genetically distinct autologous Eikenella corrodens strains by enzyme-linked immunosorbent assay (ELISA). Twenty subjects, including 10 adult periodontitis patients, 5 juvenile periodontitis patients and 5 periodontally healthy subjects were examined. Each subject was colonized by 2-8 genetically distinct E. corrodens strains. The serum IgG levels to autologous E. corrodens within individuals were significantly different in 7 adult periodontitis patients, 4 juvenile periodontitis patients and a periodontally healthy subject. Poor correlation was found in diseased subjects between serum IgG levels to autologous strains and to reference strains ATCC 23834 or FDC 373. Four adult periodontitis patients and two juvenile periodontitis patients exhibited significant serum IgG levels to autologous E. corrodens strains (two standard deviations above the mean for periodontally healthy subjects); two of these six diseased subjects exhibited low serum IgG levels to reference strains and would have been classified as low immune responders if only reference strains had been used in ELISA. This study showed the importance of using autologous E. corrodens strains in the assessment of serum IgG immune responses to this organism.

Potential of a novel protein, OMP26, from nontypeable Haemophilus influenzae to enhance pulmonary clearance in a rat model

A major outer membrane protein band of approximately 25 to 27 kDa is commonly observed in strains of Haemophilus influenzae. This study has investigated the potential of a 26-kDa protein (OMP26) from nontypeable H. influenzae (NTHI) as a vaccine candidate. OMP26 was used to immunize rats via intestinal Peyer's patches, followed by an intratracheal boost. Immunization was found to significantly enhance bacterial clearance following pulmonary challenge with both the homologous NTHI strain and a different NTHI strain. Significant levels of anti-OMP26 were found in the serum and bronchoalveolar lavage from immunized rats, and isotypes of immunoglobulin G (IgG) were also measured in serum. Analysis of IgG isotypes present in serum following OMP26-immunization suggest that predominantly a T-helper 1-type response was induced. The OMP26 protein was amino-terminally sequenced and found to have no homology with the P5 of H. influenzae type b P5 or the fimbrin protein of NTHI, both can migrate upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis at similar molecular masses but OMP26 has 100% homology with a segment of the H. influenzae Rd genome. The results of this study suggest that OMP26 may be a suitable vaccine candidate against NTHI infection and warrants continued investigation and characterization.

Prevalence and distribution of the hmw and hia genes and the HMW and Hia adhesins among genetically diverse strains of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae is a common cause of human disease and initiates infection by colonizing the upper respiratory tract. In previous work we identified high-molecular-weight adhesins referred to as HMW1 and HMW2, expressed by nontypeable strain 12, and determined that most strains of nontypeable H. influenzae express one or two antigenically related proteins. More recently, we determined that some strains lack HMW1- and HMW2-like proteins and instead express an adhesin called Hia. In the present study, we determined the prevalence and distribution of the hmw and hia genes in a collection of 59 nontypeable strains previously characterized in terms of genetic relatedness. Based on Southern analysis, 47 strains contained sequences homologous to the hmw1 and hmw2 genes and nine strains contained homologs to hia. No strain harbored both hmw and hia, and three strains harbored neither. Although the hmw and hia genes failed to define distinct genetic divisions, the hmw-deficient strains formed small clusters or lineages within the larger population structure. Additional analysis established that the IS1016 insertion element was uniformly absent from strains containing hmw sequences but was present in two-thirds of the hmw-deficient strains. As IS1016 is associated with the capsule locus (cap) in most encapsulated strains of H. influenzae, we speculate that hmw-deficient nontypeable strains evolved more recently from an encapsulated ancestor.

Genetic identification of cryptic genospecies of Haemophilus causing urogenital and neonatal infections by PCR using specific primers targeting genes coding for 16S rRNA

Previous genetic analysis of Haemophilus influenzae strains isolated from genital and neonatal infections identified a group of biotype IV that constitutes a cryptic genospecies only distantly related to H. influenzae and H. Haemolyticus. Small-subunit rRNA genes of two representative strains of this genital Haemophilus genospecies (strains 16N and 2406) were sequenced. The analysis indicated that these strains form a monophyletic unit with H. haemolyticus and H. influenzae biogroups Influenzae and Aegyptius and are more closely related to H. haemolyticus than to H. influenzae biogroups Influenzae and Aegyptius. 16S rRNA gene sequences were used to formulate primers for PCR-based identification of cryptic genital Haemophilus organisms. A 242-bp fragment was amplified from strains belonging to the genital Haemophilus genospecies but not from strains of 12 other Haemophilus species, including strains of H. influenzae biotype IV sensu stricto.

Molecular population genetic analysis of emerged bacterial pathogens: selected insights

Research in bacterial population genetics has increased in the last 10 years. Population genetic theory and tools and related strategies have been used to investigate bacterial pathogens that have contributed to recent episodes of temporal variation in disease frequency and severity. A common theme demonstrated by these analyses is that distinct bacterial clones are responsible for disease outbreaks and increases in infection frequency. Many of these clones are characterized by unique combinations of virulence genes or alleles of virulence genes. Because substantial interclonal variance exists in relative virulence, molecular population genetic studies have led to the concept that the unit of bacterial pathogenicity is the clone or cell line. Continued new insights into host parasite interactions at the molecular level will be achieved by combining clonal analysis of bacterial pathogens with large-scale comparative sequencing of virulence genes.

Bacteremia and chorioamnionitis due to cryptic genospecies of Haemophilus Influenzae biotype I

Nontypable strains of Haemophilus influenzae are well-known causes of maternal and neonatal infections. Using DNA-DNA hybridization techniques, some of these strains have been shown to belong to a cryptic genospecies of Haemophilus, which is distantly related to Haemophilus influenzae and Haemophilus hemolyticus. This report describes the first case of sepsis and chorioamnionitis due to Haemophilus influenzae biotype I, which was identified using the RapIDNH system and then confirmed by multilocus enzyme electrophoresis to belong to this cryptic genospecies of Haemophilus. The electromorph type 92 of the isolate was consistent with that of biotype I of the cryptic genospecies.

Haemophilus influenzae: then and now

Haemophilus influenzae has long been recognised as a major cause of serious infection and mortality in children less than 5 years old. Prior to the introduction of Haemophilus influenzae type b (Hib) immunisation, the incidence of a child suffering an invasive Haemophilus infection was 20-50/100,000 in industrialised countries and up to ten times higher in developing regions. The introduction of a Hib vaccine programme results in a rapid and dramatic decline in the incidence of Hib infection in the susceptible childhood population. For example, within two years of the introduction of routine Hib vaccination of infants in the UK, the risk of serious Hib infection had fallen from 1:600 to 1:30,000 by 5 years of age. Many other European countries have introduced, or are in the process of introducing, a routine Hib immunisation programme. Because the epidemiology of Haemophilus influenzae infection is changing so dramatically, it is opportune to review Haemophilus influenzae as it was perceived in the pre-vaccine era (the past) and during vaccine implementation (the present), and how its role may change in the post-vaccination era (the future). This review will summarise the historical landmarks that have led to our present-day understanding of Haemophilus influenzae pathogenicity, the concerns about antibiotic resistance, the features of the host immune response to Haemophilus influenzae, and the introduction of the Hib vaccine. Furthermore, the possible importance of this organism in the future will be discussed.

Characterization of Streptococcus agalactiae strains by multilocus enzyme genotype and serotype: identification of multiple virulent clone families that cause invasive neonatal disease

The chromosomal genotypes of 277 isolates of 16 serotypes of Streptococcus agalactiae were characterized by analysis of electrophoretically demonstrable allele profiles at 12 metabolic enzyme loci. The collection comprised the type strain and 276 strains recovered from French symptomatic and asymptomatic subjects. Sixty-one distinctive electrophoretic types (ETs), representing multilocus clonal genotypes, were identified. Cluster analysis of the ETs revealed two primary phylogenetic divisions separated by a genetic distance of 0.62, Division I contained 67 isolates which could be assigned to 13 ETs. Twenty-seven of these isolates were from samples of cerebrospinal fluid (CSF) from neonatal meningitis patients. Two ETs, separated by a genetic distance of 0.217, contained 26 of these 27 isolates. Division II contained 210 isolates, of which 27 were isolated from CSF. This division was more polymorphic and included 48 ETs. Spanning a genetic distance of 0.3, three clusters and one ET were identified within this group. Twenty-four of 27 strains isolated from CSF belonged to one cluster, and 19 of them belonged to two adjacent ETs with a genetic distance of 0.083. Fifty-five of the 68 serotype Ia strains and 24 of the 26 serotype Ib strains were each confined to one of the evolutionary lineages, and 85 of the 86 strains which carried protein antigen c belonged to phylogenetic division II. Most of the type III organisms were assigned to two clone families. The characteristics of this French population argue for the existence of particular groups of strains responsible for neonatal meningitis and demonstrate that serotyping can supply information about the genetic distribution of strains.

Characterization of transferrin binding proteins 1 and 2 in invasive type b and nontypeable strains of Haemophilus influenzae

Haemophilus influenzae has the ability to obtain iron from human transferrin via two bacterial cell surface transferrin binding proteins, Tbp1 and Tbp2. Although a wide array of strains have been shown to express these receptor proteins, two studies have recently identified a series of isolates which appeared to lack the ability to bind transferrin. Included in this group were the members of a cryptic genospecies of nontypeable biotype IV strains which appear to possess a tropism for female urogenital tissues and are major etiologic agents of neonatal and postpartum bacteremia due to H. influenzae. The present study employed oligonucleotide primers specific for genes encoding the Tbp proteins of a type b biotype I strain of H. influenzae to probe the genomic DNAs of isolates from the previous studies. The tbpA and tbpB genes which encode Tbp1 and Tbp2, respectively, were detected in all of the strains tested either by PCR amplification directly or by Southern hybridization analysis. All of the strains displayed a transferrin binding phenotype, and affinity isolation of receptor proteins with transferrin-conjugated Sepharose recovered Tbp1 and/or Tbp2 from 11 of 14 strains, including 2 of the nontypeable biotype IV strains. In addition, all of the strains were capable of growing on human transferrin specifically, indicating that the mechanism of iron assimilation from transferrin is functional and is not siderophore mediated. These results confirm the presence of tbp genes in all of the invasive H. influenzae isolates characterized to date, suggesting that Tbp-mediated iron acquisition is important in disease which initiates from either the respiratory or urogenital mucosa.

Genetic diversity of Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis revealed by restriction fragment length polymorphism of the rRNA gene region

The restriction fragment length polymorphism patterns of rDNAs from Pseudomonas aeruginosa strains isolated from the respiratory tracts of patients suffering from cystic fibrosis were obtained to evaluate the genetic polymorphism of this population of strains. Eighty-seven P. aeruginosa strains isolated from 87 patients from diverse areas of France and the ATCC 10145 strain were examined. Four restriction enzymes were used: BamHI, ClaI, EcoRI, and PstI. Forty-nine strains (56%) were in the three most frequent ribotypes (ribotypes R1 to R3). In addition, hierarchical clustering analysis of the data showed that 71 of the 88 strains (81%) clustered at a distance of less than one-third of the greatest distance observed in the total population. This indicates that clinical isolates implicated in the pathology of cystic fibrosis present a low degree of heterogeneity of rRNA operons, in contrast to the heterogeneity of strains of P. aeruginosa isolated from patients with various other pathologies. This relative homogeneity of rRNA genes was observed independently of the clinical status of the patient and the colony morphology.

Genetic structure of populations of beta-haemolytic Lancefield group C streptococci from horses and their association with disease

The genetic structure of beta-haemolytic Lancefield group C streptococci isolated from horses in Australia was examined by multilocus enzyme electrophoresis. The 249 isolates comprised 70 classified phenotypically as Streptococcus equi subspecies equi, 177 classified as S equi subspecies zooepidemicus and two which were unclassifiable. Forty-one electrophoretic types were identified which could be classified into three major clusters, A, B and C. Of the isolates, 178 fell into cluster B (types 4 to 22) and lay within a genetic distance of 0.36. Sixty-nine of the 70 S equi subspecies equi isolates fell into type 12, which suggests that they were members of a single clone, and the isolates from abscesses were significantly more likely to belong to type 12 than those from horses with no clinical signs (P < 0.001). There were no other significant associations between electrophoretic types or clusters and the isolation of the organism from particular sites. These data suggested that S zooepidemicus may be the archetypal species from which the clone designated subspecies equi has been derived. If isolates of the subspecies equi from other geographical regions also prove to be members of electrophoretic type 12, this hypothesis would be strengthened.

Nosocomial transmission of disease caused by nontypeable strains of Haemophilus influenzae

PURPOSE

The authors evaluated a geographic and temporal cluster of lower respiratory tract infections due to unencapsulated (serologically nontypeable) Haemophilus influenzae to determine whether this event represented the transmission of a single clone.

METHODS AND MATERIALS

H influenzae was recovered from eight patients at a nursing home and from three patients in an adjacent acute care hospital. Serotypes, biotypes, outer membrane protein profiles, and multilocus enzyme genotypes were determined to characterize bacterial isolates. Patient records were retrospectively examined to determine clinical and epidemiologic characteristics.

RESULTS

During a 10-day period in September 1991, lower respiratory tract infections caused by H influenzae were diagnosed in four patients residing in a single nursing home unit. Oropharyngeal cultures from four of seven asymptomatic roommates of these patients also grew H influenzae. During the month before and after the nursing home cluster of cases, four other individuals in acute care areas of the hospital had positive sputum cultures for H influenzae. Three of these latter specimens were also available for analysis. All H influenzae isolates were unencapsulated and beta-lactamase-negative. Eight of the nine isolates from the nursing home patients (two morphologically distinct colony types of H influenzae were isolated from one case) had a single outer membrane protein profile arbitrarily designated as X and a single multilocus enzyme genotype arbitrarily designated as A. In contrast, none of the isolates from the acute care cases had this profile (P < or = 0.02; two-tailed Fisher's exact test). The isolates obtained from two of the patients in acute care areas had an outer membrane protein profile arbitrarily designated as Y and a single multilocus enzyme genotype designated as B. These two patients were contemporaneously hospitalized in adjacent intensive care unit cubicles. The remaining isolates displayed an outer membrane protein profile arbitrarily designated as W. All roommates of the four patients in the nursing home were administered oral rifampin 600 mg daily for 4 days. H influenzae was not recovered from follow-up oropharyngeal cultures obtained 1 week after the completion of therapy. No beta-lactamase-negative H influenzae were identified in this unit during the subsequent 9 months.

CONCLUSION

This study furnishes strong evidence for the nosocomial transmission of a clone of unencapsulated H influenzae in a nursing home unit. Epidemiologic data showed temporal and geographic clustering of respiratory tract infections and colonization by H influenzae. Outer membrane protein profiles and multilocus enzyme genotype analysis indicated that seven of eight patients at the nursing home carried a single clone of unencapsulated H influenzae. Laboratory and epidemiologic data also demonstrated the presence, and possible nosocomial transmission, of a second clone of unencapsulated H influenzae in a physically separate area of the hospital. Finally, although a causal relationship is not proven, the outbreak ended following the administration of rifampin prophylaxis of asymptomatic carriers.

Expression of the Haemophilus influenzae transferrin receptor is repressible by hemin but not elemental iron alone

The absolute requirement for elemental iron and the porphyrin nucleus for growth of Haemophilus influenzae led us to investigate the role of iron and hemin in regulation of expression of the H. influenzae transferrin receptor. H. influenzae type b strain H1689 was grown in brain heart infusion broth supplemented with beta-NAD and either 10 or 0.1 microgram of hemin ml-1. Transferrin-binding ability was determined with a dot blot assay using human transferrin-horseradish peroxidase conjugate. Cells grown in media with 0.1 microgram of hemin ml-1 bound transferrin, but organisms grown in media with 10 micrograms ml-1 did not. In hemin-restricted media, transferrin binding occurred despite addition of up to 10 mM ferric nitrate, ferric citrate, or ferric PPi, whereas addition of 10 micrograms of hemoglobin ml-1 repressed expression. The breadth of species distribution of this mode of regulation was determined with strains previously characterized by multilocus enzyme electrophoresis. When grown in hemin-restricted media, 24 of 28 type b strains and 52 of 57 serologically nontypeable strains exhibited transferrin binding, although none did so in hemin- and iron-sufficient media. Strain H1689 and serologically nontypeable strain HI1423 grown in heat-inactivated pooled normal human serum, human cerebrospinal fluid, or human breast milk exhibited transferrin binding. Growth in these fluids with 10 micrograms of added hemin ml-1 abolished transferrin binding, whereas addition of 10 mM ferric nitrate did not. These data suggest that the transferrin receptor of H. influenzae is regulated by levels of hemin but not elemental iron alone and that this property is widely distributed among several major cloned families in the species.

Use of nonradioactive DNA probes to identify a Campylobacter jejuni strain causing abortion

A case of human abortion due to a Campylobacter infection is reported. Cultures revealed two morphologically different isolates with large and small colonies respectively. Using conventional methods of identification, the large colonies were identified as Campylobacter jejuni and the small colonies as Campylobacter coli. Dot blot hybridization and determination of rDNA restriction fragment patterns revealed that both colony types were the same strain of Campylobacter jejuni. This observation illustrates the need to use methods other than phenotypic methods when identifying strains of Campylobacter.

Ecology and significance of Pasteurellaceae in man--an update

Within the last decade new knowledge has emerged concerning the significance of Pasteurellaceae in man; the classification has undergone some changes, and new taxa were described. Haemophilus influenzae serotype b was shown to have a clonal distribution that is related to demographic patterns of the human host. Brazilian purpuric fever is caused by a special clone of Haemophilus aegyptius. H. influenzae biotype IV seems to be a genital pathogen, and may deserve species rank. New Pasteurella species have been described, that occur in well known pathological foci in man, e.g. bite wounds. Toxigenic P. multocida may occur in man also; the significance of toxigenicity in man is not known. The real actinobacilli of man, A. ureae and A. hominis are still very rarely reported. In order to avoid wrong epidemiological conclusions, correct diagnosis is emphasized.

Genetic characterization of a cryptic genospecies of Haemophilus causing urogenital and neonatal infections

In recent years, reports originating from several areas of the world have identified biotype IV strains of Haemophilus influenzae as a cause of serious urogenital, neonatal, and mother-infant infections. Preliminary analysis of a sample of biotype IV isolates found evidence for a cryptic genospecies of Haemophilus (R. Quentin, A. Goudeau, R. J. Wallace, Jr., A. L. Smith, R. K. Selander, and J. M. Musser. J. Gen. Microbiol. 136:1203-1209, 1990). Eighteen biotype IV strains assigned to the cryptic genospecies were further characterized by their rDNA restriction fragment length polymorphism patterns and genomic DNA-DNA hybridization. Isolates of the cryptic genospecies have distinctive rDNA restriction fragment length polymorphisms that differ from those of Haemophilus haemolyticus and H. influenzae. Genomic hybridization studies show that these organisms are allied with H. influenzae and H. haemolyticus and suggest a distant trifurcation of H. influenzae, H. haemolyticus, and the cryptic genospecies.

Population-based study of non-typable Haemophilus influenzae invasive disease in children and neonates

The extent of non-capsulate, non-serotypable Haemophilus influenzae (NST) as a cause of serious invasive disease in children has not been fully defined. We describe the epidemiology of these childhood infections from cases identified during a continuing prospective survey of invasive H influenzae disease in the Oxford region, UK. 408 strains of H influenzae were isolated from cases of invasive disease. 383 (94%) were H influenzae type b (Hib), 24 (6%) were NST strains, and 1 was a type f strain. 3 of the NST strains were non-capsulate type b mutants (b-), but the remaining 21 strains were from the phylogenetically distinct and heterogeneous population of non-capsulate H influenzae (NC). 10 of the NC strains were isolated from neonates with sepsis; crude mortality rate was 40%, with an incidence of 4.6 cases per 100,000 livebirths. 11 NC strains were isolated from children after the neonatal period and under 10 years of age, 4 (36%) of which had severe, unrelated, predisposing conditions. The incidence of NC invasive diseases in these children was 0.5 per 100,000 per year. The attributable mortality for these infections was 10%. Infections due to these H influenzae strains are, after the implementation of Hib vaccines, likely to persist and represent a substantial proportion of the serious infections caused by this species.

Molecular population genetic evidence of horizontal spread of two alleles of the pyrogenic exotoxin C gene (speC) among pathogenic clones of Streptococcus pyogenes

It has recently been demonstrated that the bacteriophage-borne gene (speC) encoding pyrogenic exotoxin C is harbored by phylogenetic lineages representing virtually the entire breadth of genomic differentiation present in the species Streptococcus pyogenes (J. M. Musser, A. R. Hauser, M. H. Kim, P. M. Schlievert, K. Nelson, and R. K. Selander, Proc. Natl. Acad. Sci. USA 88:2668-2672, 1991). To determine whether the speC genes occurring in association with divergent chromosomal genotypes (clones) are identical or represent a group of allelic variants, we sequenced speC from 23 S. pyogenes strains representing 15 clones identified by multilocus enzyme electrophoresis. Two alleles of speC are present in natural populations, and each allele occurs in clones that are well differentiated in overall chromosomal character; in one case, isolates of a single clone had different speC alleles. We interpret these patterns of toxin allele-clone distribution as evidence of occasional episodes of speC horizontal dissemination, presumably by bacteriophage-mediated gene transfer and recombination.

Evaluation of four commercial methods for identification and biotyping of genital and neonatal strains of Haemophilus species

Four commercial methods for identification of Haemophilus species were evaluated in comparison to conventional methods using 188 genital and neonatal Haemophilus strains. In the case of discrepancies between results obtained by the different methods, DNA-DNA hybridization was performed. The four commercial systems and conventional methods showed excellent correlation of results in 167 strains (88%). DNA-DNA hybridization was performed in 8 strains with discrepant identification results and 13 strains with discrepant biotyping results. In 15 cases discrepancies could be explained by the fact that the strains belonged to a newly recognised species of Haemophilus.

Neonatal, urogenital isolates of biotype 4 nontypeable Haemophilus influenzae express a variant P6 outer membrane protein molecule

The P6 outer membrane protein is a highly conserved molecule which is present on the surface of all strains of Haemophilus influenzae. Sixty strains of nontypeable H. influenzae which caused invasive disease or colonized the female urogenital tract were studied with monoclonal antibodies 7F3 and 4G4, which recognize different surface-exposed epitopes on the P6 molecule. All 60 strains expressed the epitope recognized by 4G4, whereas 47 of 60 strains expressed the epitope recognized by antibody 7F3. The 7F3-nonreactive strains were all biotype 4 and were recovered from the blood of neonates or postpartum women or from the female urogenital tract. The P6 genes from two 7F3-nonreactive strains were cloned, and the nucleotide sequences were determined. Analysis of amino acid sequences, immunoassays with synthetic peptides, and site-directed mutation of the P6 gene indicate that the epitope recognized by antibody 7F3 is conformational and that the sequence Asp-Ile-Thr is critical in maintaining the conformation of the epitope. We conclude that the unusually virulent clone family of biotype 4 strains of nontypeable H. influenzae express a variant P6 molecule which has an alteration in a highly conserved surface-exposed epitope.