Opposing roles of PAK2 and PAK4 in synergistic induction of MUC5AC mucin by bacterium NTHi and EGF

Mucin, a major component of mucus, plays a critical role in host mucosal defense response by participating in mucociliary clearance. However, if overproduced, overproduced mucus leads to airway mucus obstruction and conductive hearing loss. Despite extensive studies that focus on investigating how MUC5AC mucin is regulated by one inducer at a time, how MUC5AC is synergistically regulated by multiple factors remains unknown. Here we provide direct evidence for the first time that bacterial pathogen NTHi and human growth factor EGF synergize with each other to potently up-regulate MUC5AC mucin transcription. Moreover, activation of both p38 and ERK is required for synergistic induction of MUC5AC by NTHi and EGF. Finally, PAK2 and PAK4 are differentially involved in this synergistic induction of MUC5AC by acting upstream of p38 and ERK. Our studies bring novel insights into our understanding of synergistic regulation of MUC5AC mucin by both pathological and physiological inducers.

Diversity of antibiotic resistance integrative and conjugative elements among haemophili

The objective of this study was to investigate the sequence diversity in a single country of a family of integrative and conjugative elements (ICEs) that are vectors of antibiotic resistance in Haemophilus influenzae and Haemophilus parainfluenzae, and test the hypothesis that they emerged from a single lineage. Sixty subjects aged 9 months – 13 years were recruited and oropharyngeal samples cultured. Up to 10 morphologically distinct Pasteurellaceae spp. were purified, and then the species were determined and differentiated by partial sequence analysis of 16S rDNA and mdh, respectively. ICEs were detected by PCR directed at five genes distributed evenly across the ICE. These amplicons were sequenced and aligned by the neighbour-joining algorithm. A total of 339 distinguishable isolates were cultured. ICEs with all 5 genes present were found in 9 of 110 (8 %) H. influenzae and 21 of 211 (10 %) H. parainfluenzae, respectively. ICEs were not detected among the other Pasteurellaceae. A total of 20 of 60 (33 %) children carried at least 1 oropharyngeal isolate with an ICE possessing all 5 genes. One of the five genes, integrase, however, consisted of two lineages, one of which was highly associated with H. influenzae. The topology of neighbour-joining trees of the remaining four ICE genes was compared and showed a lack of congruence; though, the genes form a common pool among H. influenzae and H. parainfluenzae. This family of antibiotic resistance ICEs was prevalent among the children studied, was genetically diverse, formed a large gene pool, transferred between H. influenzae and H. parainfluenzae, lacked population structure and possessed features suggestive of panmixia, all indicating it has not recently emerged from a single source.

Real-time PCR for determining capsular serotypes of Haemophilus influenzae

A two-step real-time PCR assay targeting all six capsulation loci of Haemophilus influenzae (i.e., serotypes a to f) was developed and compared with a previously published qualitative PCR assay by using 131 H. influenzae clinical isolates. There was a 98.5% concordance between the two tests. The sensitivity of detection of capsular type-specific reference strains of H. influenzae a to c (10(1) CFU/PCR) was higher than that for type e (10(3) CFU/PCR) and types d and f (10(4) CFU/PCR), and a broader dynamic range was obtained (5 to 8 log(10) units). No cross-reaction was observed with bacteria commonly isolated from the respiratory tract. We showed that both PCR assays are more reliable than slide agglutination serotyping. The real-time PCR-based assay seems to be an alternative of choice for the epidemiological follow-up of H. influenzae invasive infections.

Nucleotide sequence diversity of the bexA gene in serotypeable Haemophilus influenzae strains recovered from invasive disease patients in Canada

The bexA genes of 36 Haemophilus influenzae isolates were sequenced to reveal their nucleotide sequence diversity, which divided them into two groups, similar to clonal divisions I and II. This sequence diversity may lead to false-negative PCR results for H. influenzae infections if bexA is the chosen gene target.

Haemophilus influenzae Type f sepsis in an immunocompetent child

Invasive infections due to Haemophilus influenzae non-type b have been reported to be on the increase with the decline in invasive H.influenzae type b infections after the introduction of the conjugate H.influenzae type b vaccine. We report a case of H. influenzae type f sepsis in a fully immunized, immunocompetent, and previously healthy 9-month-old child.

Community-acquired Haemophilus influenzae meningitis in adults

Haemophilus influenzae is an uncommon cause of bacterial meningitis in adults. This report describes a prospective evaluation of 16 episodes of community-acquired H. influenzae meningitis in a nationwide study on bacterial meningitis. Predisposing conditions were present in eight (50%) of the 16 episodes; the most common predisposing conditions were otitis or sinusitis (five episodes; 31%) and remote neurosurgery or head trauma (three episodes; 19%). One (6%) episode was fatal and hearing loss occurred in four (25%) episodes. It was concluded that H. influenzae meningitis in adults is a disease with a rather benign clinical course and a relatively good prognosis compared with pneumococcal meningitis.

An outbreak of infections caused by non-typeable Haemophilus influenzae in an extended care facility

Nosocomial outbreaks of infection due to non-typeable Haemophilus influenzae (NTHi) are rarely described. There are a few published reports that suggest that elderly patients with underlying pulmonary disease are at risk and that person-to-person spread is key to disease transmission. During the summer months of 2005, we documented an outbreak of NTHi infections in a Veterans Affairs nursing home. Thirteen patients developed conjunctivitis or lower respiratory infection involving a beta-lactamase-negative biotype III NTHi isolate, with an indistinguishable SmaI macrorestriction pattern. Patients were elderly males usually with underlying cardiac and pulmonary disease. A case-control study failed to demonstrate any specific significant risk factor for NTHi infection and there was no evidence of spatial clustering of cases within the nursing home. A random throat culture survey involving nursing home patients during the outbreak showed that only one of 19 persons was colonized with NTHi. The outbreak concluded following appropriate treatment and an emphasis on universal and respiratory droplet precautions. All patients recovered and a specific inciting event for the outbreak was never defined. Literature review revealed a spectrum of responses to nosocomial NTHi infections and a lack of consensus regarding the infection control approach towards NTHi outbreaks.

Horizontal gene transfer of ftsI, encoding penicillin-binding protein 3, in Haemophilus influenzae

Horizontal gene transfer has been identified in only a small number of genes in Haemophilus influenzae, an organism which is naturally competent for transformation. This report provides evidence for the genetic transfer of the ftsI gene, which encodes penicillin-binding protein 3, in H. influenzae. Mosaic structures of the ftsI gene were found in several clinical isolates of H. influenzae. To identify the origin of the mosaic sequence, complete sequences of the corresponding gene from seven type strains of Haemophilus species were determined. Comparison of these sequences with mosaic regions identified a homologous recombination of the ftsI gene between H. influenzae and Haemophilus haemolyticus. Subsequently, ampicillin-resistant H. influenzae strains harboring identical ftsI sequences were genotyped by pulsed-field gel electrophoresis (PFGE). Divergent PFGE patterns among beta-lactamase-nonproducing ampicillin-resistant (BLNAR) strains from different hospitals indicated the potential for the genetic transfer of the mutated ftsI gene between these isolates. Moreover, transfer of the ftsI gene from BLNAR strains to beta-lactamase-nonproducing ampicillin-susceptible (BLNAS) H. influenzae strains was evaluated in vitro. Coincubation of a BLNAS strain (a rifampin-resistant mutant of strain Rd) and BLNAR strains resulted in the emergence of rifampin- and cefdinir-resistant clones at frequencies of 5.1 x 10(-7) to 1.5 x 10(-6). Characterization of these doubly resistant mutants by DNA sequencing of the ftsI gene, susceptibility testing, and genotyping by PFGE revealed that the ftsI genes of BLNAR strains had transferred to BLNAS strains during coincubation. In conclusion, horizontal transfer of the ftsI gene in H. influenzae can occur in an intraspecies and an interspecies manner.

lgtC expression modulates resistance to C4b deposition on an invasive nontypeable Haemophilus influenzae

We have previously shown that C3 binding to serum-resistant nontypeable Haemophilus influenzae (NTHi) strain R2866 is slower than C3 binding to a serum-sensitive strain. Ab-dependent classical pathway activation is required for complement-dependent killing of NTHi. To further characterize the mechanism(s) of serum resistance of R2866, we compared binding of complement component C4b to R2866 with a serum-sensitive variant, R3392. We show that C4b binding to R2866 relative to R3392 was delayed, suggesting regulation of the classical pathway of complement. Increased C4b deposition on R3392 was independent of the amount and subclass of Ab binding, suggesting that an impediment to C4b binding existed on R2866. Immunoblotting and mass spectrometry indicated that lipooligosaccharide and outer membrane proteins P2 and P5 were targets for C4b. P2 and P5 sequences and expression levels were similar in both strains. Insertional inactivation of the phase-variable lipooligosaccharide biosynthesis gene lgtC in R2866 augmented C4b deposition to levels seen with R3392 and rendered the bacteria sensitive to serum and whole blood. These results suggest a direct role of lgtC expression in the inhibition of C4b deposition and consequent serum resistance of R2866. Alteration of surface glycans of NTHi may be a critical event in determining the ability of a strain to evade host defenses and cause disseminated infection.

[Occurrence of potentially invasive nontypeable Haemophilus influenzae strains isolating from children attending day-care centres and orphanages]

Close contacts between children attending day-care centres, orphanages or similar institutions favours mutual transmission of infections with nontypeable H. influenzae (NTHi) strains. NTHi are transmitted via air-droplets or via direct contact with respiratory system exudates from nonsymptomatic carriers. The study aimed at monitoring of potentially invasive nontypeable H. influenzae strains of hmwA+ profile among children in day-care centres and orphanages. Monitoring of prevalence of strains of hmwA profile in a single day-care centres within 8 months confirmed high level of NTHi strains transmission including NTHi strains potentially invasive. It has been shown, that potentially invasive NTHi strains appear with different frequency in day-care centres and orphanages. It also points out that dissemination NTHi is easy in such an environment.

Haemophilus influenzae type e meningitis and bacteremia in a healthy adult

Haemophilus influenzae type b causes more than 95% of serious H. influenzae meningitis. H. influenzae type e (Hie) has been implicated in a few cases of meningitis. Here, we present an adult Saudi patient with Hie meningitis and review the literature. The patient, a 19-year-old Saudi male with no significant past medical history, was noted by his family to have some changes in his mentation, confusion and refusal to eat; subsequently, he became unresponsive. Cerebrospinal fluid and blood culture grew Hie. The patient was treated with intravenous ceftriaxone with full recovery.

[Study of genetic diversity of nontypeable Haemophilus influenzae strains isolated from healthy children and patients with infection symptoms]

In the study the usefulness of genotyping methods for genetic variability examinations of non-typeable H. influenzae strains circulating in population as well as level the variability of NTHi strains isolated from healthy children and from symptomatic infection cases have been evaluated. Among genotyping methods evaluated, AFLP method of the MfeI/BglII set has been found most useful to study level of genetic variability of NTHi strains population. It has been shown that NTHi strains colonizing nasopharyngeal of healthy children present higher polymorphism level than strains isolated from patient with clinical symptoms of NTHi infection.

Characterization and modeling of the Haemophilus influenzae core and supragenomes based on the complete genomic sequences of Rd and 12 clinical nontypeable strains

BACKGROUND

The distributed genome hypothesis (DGH) posits that chronic bacterial pathogens utilize polyclonal infection and reassortment of genic characters to ensure persistence in the face of adaptive host defenses. Studies based on random sequencing of multiple strain libraries suggested that free-living bacterial species possess a supragenome that is much larger than the genome of any single bacterium.

RESULTS

We derived high depth genomic coverage of nine nontypeable Haemophilus influenzae (NTHi) clinical isolates, bringing to 13 the number of sequenced NTHi genomes. Clustering identified 2,786 genes, of which 1,461 were common to all strains, with each of the remaining 1,328 found in a subset of strains; the number of clusters ranged from 1,686 to 1,878 per strain. Genic differences of between 96 and 585 were identified per strain pair. Comparisons of each of the NTHi strains with the Rd strain revealed between 107 and 158 insertions and 100 and 213 deletions per genome. The mean insertion and deletion sizes were 1,356 and 1,020 base-pairs, respectively, with mean maximum insertions and deletions of 26,977 and 37,299 base-pairs. This relatively large number of small rearrangements among strains is in keeping with what is known about the transformation mechanisms in this naturally competent pathogen.

CONCLUSION

A finite supragenome model was developed to explain the distribution of genes among strains. The model predicts that the NTHi supragenome contains between 4,425 and 6,052 genes with most uncertainty regarding the number of rare genes, those that have a frequency of <0.1 among strains; collectively, these results support the DGH.

Invasive Haemophilus influenzae infections in children in Kamikawa subprefecture, Hokkaido, Japan, 1996-2005, before the introduction of H. influenzae type b vaccination

We evaluated 52 children with invasive Haemophilus influenzae infection in Kamikawa subprefucture, Hokkaido, Japan between 1996 and 2005. The most frequent disease was meningitis, in 30 children (57.7%), followed by pneumonia in 9 (17.3%), bacteremia in 8 (15.4%), epiglottitis in 4 (7.7%), and cellulitis in 1 (1.9%). Patients ranged in age from 0 days to 8 years. Thirty (57.7%) of the patients were less than 2 years old. Only 6 cases of invasive H. influenzae infection occurred in children older than 5 years. Between 1996 and 2005 the annual incidence rates of invasive H. influenzae infection in children aged less than 5 years, and those aged from 5 to 9 years were 4.3/100,000 to 56.8/100,000 and 0/100,000 to 12.4/100,000, respectively. A marked increase of the annual incidence rate in children aged under 5 years was observed in the most recent 2 years (2004 and 2005). No patients with invasive H. influenzae infection died, but sequelae were seen at discharge in 2 patients with meningitis, predominantly epilepsy and developmental delay of varying severity. Two patients with epiglottitis were treated by endotracheal intubation or tracheostomy. Of 41 strains isolated from 1999 to 2005, 35 were classified for antimicrobial resistance by the polymerase chain reaction (PCR) method. The number of strains of beta-lactamase-negative ampicillin-susceptible, low beta-lactamase-negative ampicillin-resistant, beta-lactamase-negative ampicillin-resistant, beta-lactamase-negative amoxicillin/clavulanic acid resistant-I, and beta-lactamase-positive amoxicillin/clavulanic acid resistant-II, were 22, 3, 5, 2, and 3, respectively. The serotype in 37 (97.4%) of 38 cases demonstrated type b.

Bacterial pericarditis and tamponade due to nonencapsulated Haemophilus influenzae complicating a case of adult community-acquired pneumonia

We report a case of bacterial pericarditis in an immunologically competent adult female caused by nonencapsulated Haemophilus influenzae (H influenzae) that was complicated by the acute development of life-threatening pericardial tamponade. H influenzae is a gram-negative coccobacillus, a pathogen most frequently associated with childhood exanthema (otitis media, meningitis) and, less frequently, adult pneumonia. Encapsulated, type b, or typable H influenzae is the strain implicated in childhood infections. On the other hand, nonencapsulated or nontypable H influenzae is the specific strain most often associated with exacerbation of chronic obstructive airway disease. Bacterial pericarditis caused by either subtype of H influenzae is exceedingly rare. We have located only 15 previously reported cases of H influenzae pericarditis occurring in adults in the world medical literature, the majority of which date back to the pre-antibiotic era. In 12 of these 15 cases (the only cases in which typing could be accomplished), the encapsulated strain of H influenzae was cultured from the pericardial fluid. Thus, to the best of our knowledge, we are reporting here the first case of bacterial pericarditis caused by nonencapsulated H influenzae in an immunologically competent adult.

The OxyR regulon in nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a gram-negative bacterium and a common commensal organism of the upper respiratory tract in humans. NTHi causes a number of diseases, including otitis media, sinusitis, conjunctivitis, exacerbations of chronic obstructive pulmonary disease, and bronchitis. During the course of colonization and infection, NTHi must withstand oxidative stress generated by insult due to multiple reactive oxygen species produced endogenously by other copathogens and by host cells. Using an NTHi-specific microarray containing oligonucleotides representing the 1821 open reading frames of the recently sequenced NTHi isolate 86-028NP, we have identified 40 genes in strain 86-028NP that are upregulated after induction of oxidative stress due to hydrogen peroxide. Further comparisons between the parent and an isogenic oxyR mutant identified a subset of 11 genes that were transcriptionally regulated by OxyR, a global regulator of oxidative stress. Interestingly, hydrogen peroxide induced the OxyR-independent upregulation of expression of the genes encoding components of multiple iron utilization systems. This finding suggested that careful balancing of levels of intracellular iron was important for minimizing the effects of oxidative stress during NTHi colonization and infection and that there are additional regulatory pathways involved in iron utilization.

Assessment of pathogen frequency and resistance patterns among pediatric patient isolates: Report from the 2004 SENTRY Antimicrobial Surveillance Program on 3 continents

Selecting empiric or directed therapy for pathogens isolated from pediatric patients can be problematic. Many antimicrobial agents are not indicated for use in pediatric patients, and regional variations of resistance mechanisms have been reported. The purpose of this study was to analyze antimicrobial resistance patterns and pathogen occurrence rates in pediatric-aged patient infections on 3 continents using data from the SENTRY Antimicrobial Surveillance Program. A total of 3537 clinical isolates were collected from 47 medical centers in 2004. With a protocol that dictated a sampling of 80 consecutive isolates from children (< or =18 years of age), all samples were forwarded to a central laboratory for reference susceptibility testing. Broth microdilution methods and current Clinical and Laboratory Standards Institute breakpoint criteria were used. The 15 most frequently observed pathogens accounted for 93.6% of all isolates. Staphylococcus aureus was the most common pathogen isolated in North America (27.4%) and Europe (19.0%), but Escherichia coli was most common in Latin America (19.3%). All Streptococcus pneumoniae strains from North America and Latin America were susceptible to the newer fluoroquinolones, gatifloxacin and levofloxacin. However, 2 S. pneumoniae strains from Italy were resistant to gatifloxacin, levofloxacin, and ciprofloxacin (> or =4 microg/mL). Ribotype and pulsed-field gel electrophoresis patterns found that these resistant pneumococci were clonal. Numerous strains of Klebsiella spp. (22.5%), E. coli (4.5%), and Proteus mirabilis (4.9%) exhibited phenotypic extended-spectrum beta-lactamase resistance patterns. Four Pseudomonas aeruginosa strains (3 from Latin America and 1 from Europe) were multidrug resistant, 2 P. aeruginosa isolates from Turkey were resistant to polymyxin B (> or =4 microg/mL), and 8.7% of Stenotrophomonas maltophilia isolates from Latin America were resistant to the "drug of choice", trimethoprim/sulfamethoxazole. Physicians should be aware of pathogen occurrences that vary by children's age, geographic location, and prior antimicrobial exposure. Therefore, continued surveillance will be necessary to monitor emerging antimicrobial resistance in the pediatric patient population, especially because new agents such as the fluoroquinolones are used to a greater extent in this age group.

Haemophilus haemolyticus: a human respiratory tract commensal to be distinguished from Haemophilus influenzae

BACKGROUND

Haemophilus influenzae is a common pathogen in adults with chronic obstructive pulmonary disease (COPD). In a prospective study, selected isolates of apparent H. influenzae had an altered phenotype. We tested the hypothesis that these variant strains were genetically different from typical H. influenzae.

METHODS

A prospective study of adults with COPD was conducted. Strains of apparent H. influenzae obtained from a range of clinical sources were evaluated by ribosomal DNA sequence analysis, multilocus sequence analysis, DNA-DNA hybridization, and sequencing of the conserved P6 gene.

RESULTS

Variant strains were determined to be Haemophilus haemolyticus by means of 4 independent methods. Analysis of 490 apparent H. influenzae strains, identified by standard methods, revealed that 39.5% of sputum isolates and 27.3% of nasopharyngeal isolates were H. haemolyticus. Isolates obtained from normally sterile sites were all H. influenzae. In a prospective study, acquisitions of new strains of H. haemolyticus were not associated with exacerbations of COPD, whereas 45% of acquisitions of new strains of H. influenzae were associated with exacerbations.

CONCLUSIONS

Standard methods do not reliably distinguish H. haemolyticus from H. influenzae. H. haemolyticus is a respiratory tract commensal. The recognition that some strains of apparent H. influenzae are H. haemolyticus substantially strengthens the association of true H. influenzae with clinical infection.

Invasive Haemophilus influenzae in Manitoba, Canada, in the postvaccination era

Fifty-two Haemophilus influenzae isolates from patients with invasive disease in the province of Manitoba, Canada, were examined for serotype, biotype, genotype, and antibiotic susceptibility. Half of the 52 isolates were found to be serotype a, and 38.5% (20 isolates) were found to be nonserotypeable (NST). There were only three serotype b strains and one each for serotypes c, d, and f. All 26 serotype a isolates belonged to biotype II and demonstrated identical or highly similar DNA fingerprints by pulsed-field gel electrophoresis. An analysis of these isolates by multilocus sequence typing showed that they belong to the clonal complex ST-23. While 69% (18 of 26) of the serotype a cases were found in males, only 9 (45%) of the 20 patients with NST isolates were males. Twenty (77%) of the 26 serotype a isolates were from patients who were </=24 months old. Twelve (63%) of the NST isolates were from adult or adolescent patients. In contrast to the clonal nature of serotype a isolates, the 20 NST isolates were found to belong to 18 different sequence types. Most of these 18 different sequence types were unrelated to each other, with the exception of 7 sequence types grouped into three clonal groups. Two (6.25%) out of 32 serotypeable isolates (1 serotype a and 1 serotype b) and 6 (30%) of 20 NST isolates were resistant to ampicillin due to beta-lactamase production. These results suggest a change in the epidemiology of H. influenzae disease, with the majority of invasive H. influenzae isolates being associated with serotype a and NST strains.

Antibodies specific for the high-molecular-weight adhesion proteins of nontypeable Haemophilus influenzae are opsonophagocytic for both homologous and heterologous strains

The HMW1/HMW2-like adhesion proteins of nontypeable Haemophilus influenzae (NTHI) are expressed by 75% of NTHI strains. Antibodies directed against these proteins are opsonophagocytic in vitro and are protective in an animal model of infection. The objective of the present study was to determine the opsonophagocytic activity of high-titer anti-HMW1/HMW2 immune sera against both homologous and heterologous NTHI strains. Chinchillas were immunized with purified HMW1/HMW2-like proteins from five prototype NTHI strains. Serum opsonophagocytic activity was monitored in an assay that uses a human promyelocytic cell line, HL-60, as the source of phagocytic cells. Preimmune sera did not demonstrate opsonophagocytic killing of any strains. In contrast, the immune sera demonstrated killing of the five homologous NTHI strains at titers ranging from 1:320 to 1:640. The immune sera also demonstrated killing of eight heterologous NTHI strains that express HMW1/HMW2-like proteins at titers ranging from 0 to 1:640. Killing of heterologous strains sometimes demonstrated a prozone phenomenon. None of the immune sera killed NTHI strains that did not express HMW1/HMW2-like proteins. Adsorption of immune sera with HMW1/HMW2-like proteins purified from either homologous or heterologous NTHI strains eliminated opsonophagocytic killing of homologous strains in most cases. These data demonstrate that antibodies produced following immunization with the HMW1/HMW2-like proteins are opsonophagocytic for both homologous and heterologous NTHI and strongly suggest that common epitopes recognized by functionally active antibodies exist on the HMW1/HMW2-like proteins of unrelated NTHI strains. The results argue for the continued investigation of the HMW1/HMW2-like proteins as potential vaccine candidates for the prevention of NTHI disease.

Identification of new genetic regions more prevalent in nontypeable Haemophilus influenzae otitis media strains than in throat strains

Nontypeable (NT) Haemophilus influenzae strains cause significant respiratory illness and are isolated from up to half of middle ear aspirates from children with acute otitis media. Previous studies have identified two genes, lic2B and hmwA, that are associated with NT H. influenzae strains isolated from the middle ears of children with otitis media but that are not associated with NT H. influenzae strains isolated from the throats of healthy children, suggesting that they may play a role in virulence in otitis media. In this study, genomic subtraction was used to identify additional genetic regions unique to middle ear strains. The genome of NT H. influenzae middle ear strain G622 was subtracted from that of NT H. influenzae throat strain 23221, and the resultant gene regions unique to the middle ear strain were identified. Subsequently, the relative prevalence of the middle ear-specific gene regions among a large panel of otitis media and throat strains was determined by dot blot hybridization. By this approach, nine genetic regions were found to be significantly more prevalent in otitis media strains. Classification tree analysis of lic2B, hmwA, and the nine new potential otitis media virulence genes revealed two H. influenzae pathotypes associated with otitis media.

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.

Nontypeable Haemophilus influenzae strains with the capsule-associated insertion element IS1016 may mimic encapsulated strains

With the elimination of Haemophilus influenzae type b through vaccination, it has been suggested that other types of H. influenzae strains might acquire virulence traits and emerge as important pathogens. The gene sequence IS1016 has been associated with an increased capacity to cause severe infections. It is usually present in encapsulated strains but is sometimes harbored by nontypeable H. influenzae strains. To explore this further, 118 H. influenzae isolates, collected from both patients and healthy carriers, were investigated with PCR with reference to this gene sequence. Isolates positive for the insertion element were bio- and serotyped. The presence of hmw genes for adherence, the genetic profile, and the ability to form biofilm in vitro were investigated. A total of 15 isolates were IS1016-positive, whereof 12 were nontypeable. All 12 nontypeable isolates were obtained from healthy carriers, and 92% of the isolates were biotype I. They cross-reacted to some extent with type-specific antisera or exhibited a restricted genetic diversity like encapsulated strains. Furthermore, they lacked hmw-genes, and their ability to form biofilms was comparable with a capsule-deficient type b strain. Although this subset of strains mimicked traits usually exhibited by encapsulated strains, the isolation frequency did not seem to have been affected by vaccination.