Nasopharyngeal carriage of Haemophilus influenzae among adults with co-morbidities

After the widespread use of Haemophilus influenzae type b (Hib) vaccine, H. influenzae invasive disease is now commonly due to non-encapsulated (NTHi), affecting mostly the youngest and the elderly. The objective of this study was to investigate H. influenzae nasopharyngeal carriage rate in adults with co-morbidities and possible associated risk factors.

METHODS

Patients aged >50 years with co-morbidities attending medical centres were examined. A nasopharyngeal swab was analysed for H. influenzae presence by cultural and molecular methods (RT-PCR). Univariable and multivariable analysis of risk factors for H. influenzae carriage were performed. Serotype of isolates was determined by PCR capsular genotyping. Minimum inhibitory concentration (MIC) was determined by MIC gradient test and β-lactamase production was detected by the nitrocephin test. Genotyping was performed by Multilocus sequence typing (MLST). Phylogenetic relationships among carriage and invasive NTHi strains were assessed.

RESULTS

Among 248 enrolled patients (median age: 73 years), the carriage rate was 5.6% and 10.5% by cultural method or RT-PCR, respectively. Colonization with H. influenzae was significantly associated with the presence of acute respiratory symptoms (adjusted OR = 12.16, 95% CI: 3.05-48.58, p < 0.001). All colonizing isolates were NTHi. Three isolates (3/14, 21.4%) were resistant to ampicillin and beta-lactamase positive. MLST revealed a high degree of genetic diversity, with 11 different STs from 14 isolates. Eight out of the 11 (72.7%) STs were shared among carriage and invasive isolates.

CONCLUSIONS

Adults ≥50 years old with co-morbidities are occasionally colonized by H. influenzae, even if the presence of co-morbidities is not a risk factor for colonization. The presence of acute respiratory symptoms is the only factor associated with H. influenzae colonization. Colonizing H. influenzae are all NTHi. Colonizing H. influenzae often belong to the same STs of invasive disease isolates.

Invasive Haemophilus influenzae type b (Hib) disease in children in Italy, after 20 years of routine use of conjugate Hib vaccines

Haemophilus influenzae serotype b (Hib) was the leading cause of bacterial meningitis in children before the implementation of infant immunization with conjugate Hib vaccines. Despite the effectiveness of the vaccine, invasive Hib disease cases (i.e. isolation of Hib from a normally sterile site) are still reported in children. All invasive Hib disease cases in children ≤ 15 years reported through the National Surveillance System of Invasive Bacterial Disease, during 2012-2018 in Italy, were analyzed. Hib PCR-confirmed isolates were subjected to MLST and PFGE analysis. The number of copies of the capb locus, a virulence factor potentially contributing to true vaccine failures (TVFs), was determined by Southern blot analysis. Vaccine effectiveness (VE) was determined using a multiple Poisson regression model. 31 cases of invasive Hib disease in children were reported. Fourteen children were vaccinated (TVFs), 14 were unvaccinated and 2 partially vaccinated (vaccination status was unknown for 1 case). The median age of children was 12 months (range 3 months-15 years). A decrease in vaccination coverage was observed in 2014-2016 (source Ministry of Health), and a rise in incidence was documented from 2016 until 2018, especially in children < 5 years. Vaccine effectiveness was estimated to be 83% (95% CI:45-95). 24 isolates were available. The predominant ST was ST6 (70.8%). Cluster analysis of ST6 isolates by PFGE identified five variants. Six isolates (25%) contained multiple copies of the capb locus distributed among TVFs (30%) and unvaccinated children (16.7%). Our data show that both failures to vaccinate and TVFs are associated with invasive Hib disease in children in Italy, during the vaccination era. Most cases in children ≤ 2 years were vaccine-preventable, since they occurred in unvaccinated subjects (13/21 cases, 62%). No host predisposing factors for TVF were recognized. TVFs were not significantly associated with either specific genotypes or amplification status of the capb locus.

Increasing trend in invasive non-typeable Haemophilus influenzae disease and molecular characterization of the isolates, Italy, 2012-2016

Routine immunization of infants with conjugate vaccines against Haemophilus influenzae type b (Hib) has greatly reduced the incidence of invasive Hib disease; however changes in the epidemiology of H. influenzae disease have occurred. We describe the epidemiology of invasive H. influenzae disease and the characterization of isolates collected in Italy between 2012 and 2016. Trends in the overall incidence of invasive H. influenzae disease were calculated. Isolates were characterized by PCR capsular genotyping, antimicrobial susceptibility testing, ampicillin resistance-associated gene sequencing and MLST. Trends in incidence by serotype and serotype-specific distribution were estimated using multiple imputation of missing data. The overall incidence of invasive H. influenzae disease increased 22.5% yearly (from 0.11/100,000 in 2012 to 0.24/100,000 in 2016). Most cases (82.0%) were due to non-typeable H. influenzae (NTHi). An increasing trend in NTHi disease burden was estimated; the highest rise was among infants <12 months (40.8% annual increase). Invasive Hib disease showed a fluctuating trend with a clear increase in 2016, while we found an increasing trend for disease due to non-Hib capsulated serotypes in the elderly (32.9% annual increase). Ampicillin resistance mediated by either β-lactamase or altered penicillin-binding proteins 3 (PBP3) increased. In spite of genetic diversity of NTHi, sequence types (STs) associated with ampicillin resistance status were identified (ST103/ST106 linked to β-lactamase production and ST14 linked to a specific PBP3 substitution pattern). The increasing trend in invasive NTHi disease in infants is of concern underlying the need for the development of a future vaccine against NTHi.

Emergence of Invasive Haemophilus influenzae Type A Disease in Italy

We report on the first detection of 2 cases of invasive Haemophilus influenzae type a (Hia) disease in Italy. The cases were sustained by the same Hia "strain" belonging to the ST23 clone that has previously been reported only outside Europe. The emergence of invasive Hia disease is of concern.

Carriage of Haemophilus influenzae in the oropharynx of young children and molecular epidemiology of the isolates after fifteen years of H. influenzae type b vaccination in Italy

BACKGROUND

Haemophilus influenzae is an important pathogen able to cause a wide spectrum of diseases in children. Colonization of the upper respiratory tract is a risk factor for developing disease. This study aimed to investigate the oropharyngeal carriage rate of H. influenzae in young children in two Italian cities, 15 years after H. influenzae type b (Hib) vaccination was introduced. Antibiotic resistant traits and genotypes of the colonizing H. influenzae isolates were investigated.

METHODS

Oropharyngeal swabs were obtained from 717 healthy children aged <6 years (June 2012-July 2013). Potential risk factors for H. influenzae colonization were investigated. H. influenzae isolates from carriage were characterized by PCR capsular typing, ampicillin susceptibility testing, resistance-associated gene sequencing and multilocus sequence typing (MLST). For comparison purposes, 38 non-typeable H. influenzae (NTHi) isolates from invasive disease were genotyped by MLST.

RESULTS

The overall H. influenzae carriage rate was 14.1% (101/717). Age, study site, presence of young siblings, and complete Hib vaccination status were independently associated with colonization. Of 101 isolates, 98 were NTHi, 2 were type e and 1 was type f. The overall ampicillin resistance rate was 15.8% (16/101). Resistance was mediated by TEM-1 β-lactamase production in half of isolates (n=8) or modifications in penicillin-binding protein (PBP) 3 in the other half (n=8). Several substitutions were discovered in PBP3 including the Asn526Lys change. Seventy-six different STs were identified among 98 NTHi isolates from carriage, with only 4 STs (ST12, ST57, ST238, ST1238) encompassing ≥ 3 isolates. Comparison of carriage and disease isolates found that several STs were shared between the two sources, although none of the major disease-associated STs were observed in carriage isolates.

CONCLUSIONS

NTHi is the predominant serotype in carriage. The importance of monitoring both NTHi colonization rate and circulating genotypes should be emphasized in the era of the Hib conjugate vaccines.

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.

Genital carriage of the genus Haemophilus in pregnancy: species distribution and antibiotic susceptibility

Recent reports have hypothesized that colonization of the maternal genital tract with non-capsulated Haemophilus influenzae could result in neonatal invasive disease. In this study, genital carriage of the genus Haemophilus was investigated in 510 pregnant women attending an Italian hospital for routine controls. Overall, vaginal carriage of the genus Haemophilus was 9.0 % (46/510). A high colonization rate with Haemophilus parainfluenzae (37/510, 7.3 %) was found; other species, such as Haemophilus pittmaniae (7/510, 1.4 %) and Haemophilus haemolyticus (2/510, 0.4 %), were detected for the first time in the genital flora by 16S rRNA gene sequencing. Notably, no H. influenzae was identified, in agreement with previous investigations indicating that this species is rarely isolated from the genito-urinary tract of pregnant women. No antibiotic resistance was detected in H. pittmaniae and H. haemolyticus, but quite a high degree of ampicillin (10/37, 27 %) and ciprofloxacin (3/37, 8.1 %) resistance was observed in H. parainfluenzae. Five ampicillin-resistant isolates were β-lactamase producers, whereas five isolates exhibited a β-lactamase-negative ampicillin-resistant (BLNAR) phenotype. Sequencing of penicillin-binding protein 3 revealed that Val511Ala, Asn526Ser, Ala530Ser and Thr574Ala changes were associated with BLNAR phenotypes. Two ciprofloxacin-resistant isolates carried substitutions in both GyrA (Ser84Phe and Asp88Tyr) and ParC (Ser84Tyr and Met198Leu); the other ciprofloxacin-resistant isolate had substitutions in ParC, only (Ser138Thr and Met198Leu). In conclusion, ∼10 % of pregnant women carried a species of Haemophilus in their genital tract. The emergence of non-β-lactamase-mediated resistance in genital H. parainfluenzae is a matter of concern because of the risk of mother-to-baby transmission.

Biofilm-growing intestinal anaerobic bacteria

Sessile growth of anaerobic bacteria from the human intestinal tract has been poorly investigated, so far. We recently reported data on the close association existing between biliary stent clogging and polymicrobial biofilm development in its lumen. By exploiting the explanted stents as a rich source of anaerobic bacterial strains belonging to the genera Bacteroides, Clostridium, Fusobacterium, Finegoldia, Prevotella, and Veillonella, the present study focused on their ability to adhere, to grow in sessile mode and to form in vitro mono- or dual-species biofilms. Experiments on dual-species biofilm formation were planned on the basis of the anaerobic strains isolated from each clogged biliary stent, by selecting those in which a couple of anaerobic strains belonging to different species contributed to the polymicrobial biofilm development. Then, strains were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy to reveal if they are able to grow as mono- and/or dual-species biofilms. As far as we know, this is the first report on the ability to adhere and form mono/dual-species biofilms exhibited by strains belonging to the species Bacteroides oralis, Clostridium difficile, Clostridium baratii, Clostridium fallax, Clostridium bifermentans, Finegoldia magna, and Fusobacterium necrophorum.

Microbial biofilms associated with biliary stent clogging

Endoscopic stenting is a palliative approach for the treatment of diseases involving biliary obstruction. Its major limitation is represented by stent occlusion, followed by life-threatening cholangitis, often requiring stent removal and replacement. Although it has been suggested that microbial colonization of biliary stents could play a role in the clogging process, the so far available data, particularly on the role of anaerobic bacteria, are not enough for a comprehensive description of this phenomenon. Our study was focused on the analysis of 28 explanted biliary stents by culturing, denaturing gradient gel electrophoresis and scanning electron microscopy to identify all the aerobic/anaerobic bacteria and fungi involved in the colonization of devices and to verify the ability of isolated anaerobic bacterial strains to form a biofilm in order to better understand the mechanisms of stent clogging.

Haemophilus parainfluenzae meningitis in an adult associated with acute otitis media

A case of Haemophilus parainfluenzae meningitis in a woman with a 3-day history of acute otitis media is reported. Her medical history included bladder cancer surgery. Unequivocal identification of the isolate was obtained by using molecular techniques such as 16S rRNA sequencing besides to conventional culture methods. To investigate bacterial virulent traits possibly related to invasive properties, in vitro serum resistance of our isolate was analyzed, but it was found serum susceptible. Our study demonstrates that H. parainfluenzae can be considered an opportunistic pathogen able to cause life-threatening infections not only in children but also in patients with underlying conditions.

Variation in expression of HMW1 and HMW2 adhesins in invasive nontypeable Haemophilus influenzae isolates

Background

Among surface antigens of nontypeable Haemophilus influenzae (NTHi), the HMW1 and HMW2 proteins are the major adhesins promoting colonization of the upper respiratory tract. Since they are potential vaccine candidates, knowledge concerning variation in HMW proteins expression among clinical isolates is of great interest. In this study, expression of hmw1A and hmw2A genes was evaluated by quantitative real-time reverse transcription-PCR in 3 NTHi invasive isolates (strains 56, 72, 91) and in the prototype strain 12. Number of 7-bp repeats within the hmwA promoters and presence of HMW proteins by Western blotting were also determined.

Results

Results showed that gene transcription varied not only among different isolates but also between the hmw1A and hmw2A genes from the same isolate. Compared to that found in prototype strain 12, up-regulation of the hmw1A gene expression was found in strain 56, down-regulation of both hmw1A and hmw2A genes transcripts was observed in strain 72 whereas the two hmwA genes appeared differentially expressed in strain 91 with the hmw1A transcript enhanced but the hmw2A transcript reduced.

Conclusion

Increasing numbers of 7-bp repeats within the hmwA promoters generally correlated with decreased amounts of mRNA transcript, however additional control mechanisms contributing to modulation of hmw1A gene seem to be present.

First characterization of heterogeneous resistance to imipenem in invasive nontypeable Haemophilus influenzae isolates

This study describes the first two reported invasive nontypeable Haemophilus influenzae (NTHI) isolates (strains 183 and 184) with heterogeneous resistance to imipenem. For both isolates, Etest showed imipenem MICs of > or =32 microg/ml. When the two strains were examined by the quantitative method of population analysis, both strain populations were heterogeneously resistant to imipenem and contained subpopulations growing in the presence of up to 32 microg of imipenem/ml at frequencies of 1.7 x 10(-5) and 1.5 x 10(-7), respectively. By pulsed-field gel electrophoresis analysis, the two isolates appeared to be genetically closely related. The sequencing of the ftsI gene encoding penicillin-binding protein 3 (PBP 3) and comparison with the sequence of the imipenem-susceptible H. influenzae strain Rd identified a pattern of six amino acid substitutions shared between strains 183 and 184; an additional change was unique to strain 183. No relationship between mutations in the dacB gene encoding PBP 4 and imipenem resistance was found. The replacement of the ftsI gene in the imipenem-susceptible strain Rd (for which the MIC of imipenem is 0.38 to 1 microg/ml) with ftsI from strain 183 resulted in a transformant for which the MIC of imipenem ranged from 4 to 8 microg/ml as determined by Etest. The Rd/183 transformant population showed heterogeneous resistance to imipenem; it contained subpopulations growing in the presence of up to 32 mug of imipenem/ml at a frequency of 3.3 x10(-8). The presence of additional resistance mechanisms, such as the overexpression of the AcrAB efflux pump, was investigated and does not seem to be involved. These data indicate that the heterogeneous imipenem resistance phenotype of our NTHI clone depends largely on the PBP 3 amino acid substitutions. We speculated that bacterial regulatory networks may play a role in the control of the heterogeneous expression of the resistance phenotype.

Nontypeable Haemophilus influenzae meningitis in children: phenotypic and genotypic characterization of isolates

BACKGROUND

With the decline in the incidence of invasive Haemophilus influenzae type b disease as result of routine immunization of infants, the potential emergence of nontypeable H. influenzae (NTHi) strains as important pathogens has been suggested.

METHODS

From June 1997 to July 2006, 9 cases of NTHi meningitis in children aged < or =60 months were detected. The 9 NTHi isolates were characterized. Antimicrobial susceptibility patterns were determined by E-test. The transpeptidase domain of penicillin binding protein 3 of a beta-lactamase negative ampicillin-resistant strain was sequenced. Genetic relatedness among isolates was assessed by pulsed field gel electrophoresis and by multilocus sequence typing. The presence of HMW and Hia adhesins and hemagglutinating fimbriae was investigated by PCR and Western Blotting.

RESULTS

The 9 cases of NTHi meningitis did not occur in specific risk groups, except for one patient. Of the 9 NTHi isolates, 2 were beta-lactamase producers and 1 showed the beta-lactamase negative ampicillin-resistant phenotype. Sequencing of the penicillin binding protein 3 revealed novel amino acid substitutions. A high degree of genetic diversity among isolates was demonstrated by pulsed field gel electrophoresis. Multilocus sequence genotyping confirmed that the 9 NTHi isolates did not belong to related phylogenetic clusters. HMW adhesins were found in 2 isolates, and 5 strains possessed Hia. No hemagglutinating fimbriae were detected, even though 2 isolates contained hifA gene sequences.

CONCLUSION

NTHi isolates from cases of meningitis in children are genetically diverse. Distribution of adhesins among the isolates we examined is unusual: most strains express Hia that generally occurs in a minority of strains in NTHi, suggesting that this adhesin may play a role in virulence mechanisms of NTHi causing meningitis.

Genetic Diversity of Invasive Strains ofHaemophilus influenzaeType b before and after Introduction of the Conjugate Vaccine in Italy

We determined the genotypes of 95 invasive Haemophilus influenzae type b (Hib) strains collected before and after introduction of widespread Hib vaccination in Italy. No substantial change in genetic diversity was highlighted by pulsed-field gel electrophoresis. However, an upward temporal trend in proportion of strains possessing multiple copies of the capsulation b locus was detected (P = .03).

Detection of six copies of the capsulation b locus in a Haemophilus influenzae type b strain isolated from a splenectomized patient with fulminant septic shock

We report on the first detection of six copies of the capsulation b locus in a Haemophilus influenzae type b strain isolated from a splenectomized patient with fulminant septic shock associated with disseminated intravascular coagulation and death. The unusual amplification of the locus might have contributed to the rare and severe clinical presentation.

Conservation and diversity of HMW1 and HMW2 adhesin binding domains among invasive nontypeable Haemophilus influenzae isolates

The pathogenesis of nontypeable Haemophilus influenzae (NTHi) begins with adhesion to the rhinopharyngeal mucosa. In almost 80% of NTHi clinical isolates, the HMW proteins are the major adhesins. The prototype HMW1 and HMW2 proteins, identified in NTHi strain 12, exhibit different binding specificities. The two binding domains have been localized in regions of maximal sequence dissimilarity (40% identity, 58% similarity). Two areas within these binding domains have been found essential for full level adhesive activity (designated the core-binding domains). To investigate the conservation and diversity of the HMW1 and HMW2 core-binding domains among isolates, PCR and DNA sequencing were used. First, we separately amplified the hmw1A-like and hmw2A-like structural genes in nine invasive NTHi isolates, discovering two new hmwA alleles, whose sequences are herein reported. Then, the hmw1A-like and hmw2A-like PCR products were used as the template in nested PCR to produce amplicons encompassing the encoding sequences of the two core-binding domains. In-depth sequence analysis was then performed among sequences of each group, with the support of specific computer programs. Overall, extensive sequence diversity among isolates was highlighted. However, similarity plots showed patterns consisting of peaks of relatively high similarity alternating with strongly divergent regions. The phylogenetic tree clearly indicated the HMW1-like and HMW2-like core-binding domain sequences as two clusters. Distinct sets of conserved amino acid motifs were identified within each group of sequences using the MEME/MOTIFSEARCH tool. Since HMW adhesins could represent candidates for future vaccines, identification of specific patterns of conserved motifs in otherwise highly variable regions is of great interest.

Presence of Multiple Copies of the Capsulation b Locus in InvasiveHaemophilus influenzaeType b (Hib) Strains Isolated from Children with Hib Conjugate Vaccine Failure

Most invasive Haemophilus influenzae type b strains possess a duplication of the capsulation locus. Further amplification resulting in as many as 5 copies has been described. To verify whether amplification is involved in vaccine failure, the number of copies of the locus was determined by Southern blotting in 90 strains from children with true vaccine failure (TVF) between 1993 and 1999 and in 139 strains from unvaccinated children (50 collected between 1993 and 1999 and 89 collected between 1991 and 1992, before routine immunization was introduced). A significantly greater proportion of strains from TVFs contained multiple copies, compared with strains from control children (24% vs. 10%; P = .0379), which suggests that amplification of the capb locus may be a contributory factor in vaccine failure. The presence of multiple-copy strains was associated with disease other than meningitis.

Antimicrobial susceptibility of Haemophilus influenzae strains isolated from invasive disease in Italy

OBJECTIVES

Haemophilus influenzae invasive disease is potentially life threatening and requires prompt antibiotic therapy. The aim of this study was to assess the antimicrobial susceptibility of H. influenzae strains isolated from invasive disease in Italy and to investigate ampicillin-resistant isolates by molecular biology techniques.

MATERIALS AND METHODS

One-hundred and seventy-six invasive H. influenzae isolates, collected during 1998-2003, were analysed for susceptibility to ampicillin, azithromycin, chloramphenicol and ciprofloxacin. Ampicillin-resistant isolates were further tested against cefotaxime and imipenem. MICs were determined by Etest and interpreted according to NCCLS criteria. The ampicillin resistance genes, bla(TEM) and bla(ROB), were searched for by PCR. Genetic relatedness among ampicillin-resistant isolates was investigated by PFGE.

RESULTS

Overall, ampicillin resistance was 10.2% (all beta-lactamase producer strains). The prevalence of ampicillin-resistant isolates increased from 6.9% in 1998/1999 to 19% in 2002/2003. Resistance to azithromycin and chloramphenicol was 6.8% and 1.7%, respectively. No strains were resistant to ciprofloxacin. Co-resistance between ampicillin and chloramphenicol and between ampicillin and azithromycin was observed in three and one isolates, respectively. All ampicillin-resistant isolates were susceptible to cefotaxime and imipenem and all harboured the bla(TEM) gene. PFGE demonstrated that most of the ampicillin-resistant isolates showed little genetic homology.

CONCLUSIONS

An upward trend in resistance to ampicillin due to beta-lactamase production was demonstrated In Italy. According to PFGE results, clonal dissemination of ampicillin-resistant isolates does not occur. Imipenem may represent an appropriate alternative for treatment of H. influenzae invasive disease caused by ampicillin-resistant isolates when third-generation cephalosporins cannot be used.

Evidence for cytoskeletal changes secondary to plasma membrane functional alterations in the in vitro cell response to Clostridium perfringens epsilon-toxin

To investigate the mode of action of Clostridium perfringens epsilon-toxin, MDCK cells were treated with purified toxin and incubated at 37 degrees C for up to 24h. Exposure to epsilon-toxin caused a time-dependent decrease in cell-cell and cell-substrate interactions. After 30min of treatment retraction of the cell body and the emission of filopodia were detectable in a number of cells. Longer exposure resulted in cell rounding and cell blebbing which reached a maximum after 5h of toxin treatment. A parallel modification in the cytoskeleton was also detected. Actin marginalization and the entanglement of microtubules and intermediate filaments were observed by fluorescence microscopy after 30min of toxin exposure. Functional alterations of the plasma membrane of MDCK cells were assessed by flow cytometry. After 10 or 30min of intoxication an increase in cell volume was detected, indicating an alteration in plasma membrane permeability. These findings provide evidence for cytoskeletal changes and plasma membrane functional alterations in the in vitro cell response to C. perfringens epsilon-toxin.

Invasive type e Haemophilus influenzae disease in Italy

We describe the first reported cases of invasive type e Haemophilus influenzae disease in Italy. All five cases occurred in adults. The isolates were susceptible to ampicillin and eight other antimicrobial agents. Molecular analysis showed two distinct type e strains circulating in Italy, both containing a single copy of the capsulation locus.

Molecular typing and long-term comparison of clostridium difficile strains by pulsed-field gel electrophoresis and PCR-ribotyping

Thirty-two related and 68 unrelated isolates of Clostridium difficile, isolated in different Italian hospitals since 1987, were analysed by PFGE and PCR-ribotyping to investigate their genetic relatedness. The isolates were classified into 28 groups by PFGE and 20 ribotypes by PCR-ribotyping. A single clone of C. difficile was recognised as the cause of three geographically and chronologically distant outbreaks. The correlation between PFGE and PCR-ribotyping results was good, with agreement for 77 (84%) of the 92 isolates typed by both methods. However, among sporadic isolates the discriminatory power of PFGE was more evident. Eight isolates that were untypable by PFGE could be analysed by PCR-ribotyping. The dendrograms generated showed that the genetic relatedness of the C. difficile isolates obtained by both techniques was comparable. The majority of the isolates in recent years appeared to be genetically unrelated to isolates from past infections. However, two clonal groups identified in all time periods had a common origin and this seems to indicate that they share some advantageous biological characteristics. The constant monitoring of C. difficile epidemiology will allow acquisition of further important data on this nosocomial pathogen.

Immunogenicity issues in the quality control of the new acellular pertussis vaccines

Over the last few years our laboratory has been assessing the consistency of production of different batches of acellular pertussis vaccines to be marketed in Italy. Central to this is immunogenicity assay of the lots under control compared with those of a reference vaccine with documented clinical efficacy.However, the current assays based on the assessment of antibody (Ab) response in the mouse are unrelated to mechanisms of protection in children. The absence of a clear correlation between Ab responses and protection has also been documented in recent clinical trials. On this basis, we are currently considering the possibility of adding to the established criteria of immunogenicity in mice based on Ab responses, information from studies on cell-mediated immune responses to the vaccine constituents.

Oligonucleotide probes for detection of cephalosporinases among Bacteroides strains

Two oligonucleotide probes selected from the sequences of cepA and cfxA genes, respectively, were used to detect beta-lactamase production among strains of the Bacteroides fragilis group. By using these probes, colony hybridization was shown to be a specific and rapid method for identifying the more prevalent beta-lactamase, CepA, and the rarer CfxA enzyme among B. fragilis strains.

A 5-year immunization field trial against hepatitis B using a Chinese hamster ovary cell recombinant vaccine in French Polynesian newborns: results at 3 years

A hepatitis immunization field trial, using a Chinese hamster ovary (CHO) cell recombinant vaccine, was implemented for newborns in the Austral archipelago of French Polynesia in 1988. Three different schedules were used: (1) four vaccine doses at months (M) M0, M1, M2 and M12; (2) three vaccine doses at M0, M1 and M6; and (3) three vaccine doses at M0, M1 and M12. The programme evaluation was performed yearly at fixed dates, i.e. October-November 1989, 1990 and 1991. After the third year, of the 582 children who received one or more doses of vaccine, four were HBsAg carriers. After one or two doses, 88 and 98%, respectively, had seroconverted for at least one of the two measured antibodies, anti-HBs or anti pre-S2. After three doses, seroconversion rates and geometric mean anti-HBs titres were, respectively, 94% and 187 mIU ml-1 using schedule M0, M1, M2; 95% and 507 mIU ml-1 using schedule M0, M1, M6 and 96% and 476 mIU ml-1 using schedule M0, M1, M12. After four doses (M0, M1, M2, M12) the corresponding results were 99% and 1518 mIU ml-1. One of the 16 vaccinated neonates born to HBsAg/HBeAg-positive mothers was an HBsAg carrier, implying a protective rate for the prevention of perinatal transmission of 93%. Overall, these results indicate that, in field conditions, indiscriminate vaccination of newborns with a CHO-recombinant vaccine without hepatitis B immunoglobulin (HiBG) resulted in high immunogenicity. Final evaluation in 1993-1994 will permit confirmation of the effectiveness of the two three-dose vaccine schedules.

Ivermectin plus diethylcarbamazine: an additive effect on early microfilarial clearance

The effects of ivermectin, diethylcarbamazine (DEC), and the combination of both drugs on levels of microfilaremia (mf) were studied in 30 male Polynesian Wuchereria bancrofti carriers. Microfilarial densities were measured 30 min (H1/2), 1 hr (H1), and 2, 4, 8, 24, and 96 hr (H2, H4, H8, H24, and H96) after supervised single doses of ivermectin plus DEC (400 micrograms/kg plus 1 mg/kg, respectively, 400 micrograms/kg plus 3 mg/kg, respectively, and 400 micrograms/kg plus 6 mg/kg, respectively), DEC (6 mg/kg) alone, and ivermectin (400 micrograms/kg and 100 micrograms/kg, respectively) alone given to six groups of five patients each. The results showed that 1) DEC alone or combined with ivermectin induced a rapid clearance of mf after drug intake; at H1/2, the number of circulating microfilariae was reduced to 16%, 8%, 28%, and 31%, respectively, of pretreatment values in the groups receiving ivermectin plus DEC (400 micrograms/kg plus 1 mg/kg, 400 micrograms/kg plus 3 mg/kg, and 400 micrograms/kg plus 6 mg/kg) and DEC (6 mg/kg) alone; 2) ivermectin alone induced a rapid increase of mf densities during the first 2 hr, followed by a sharp decrease from H4 to H96; and 3) between H8 and H96, mf clearance was almost complete with the combination of ivermectin and DEC. A comparison among groups did not show any synergistic interaction between ivermectin and DEC on the clearance of microfilaria, with the effect of each drug being additive to each another.

Leprosy in French Polynesia. Epidemiological trends between 1946 and 1987

The analysis of computerized data (OMSLEP system) on patients from French Polynesia followed since 1940 has shown a decrease in the mean annual detection rates for leprosy, all forms combined, from 24.73 per 100,000 inhabitants in 1946 to 8.1 per 100,000 in 1987 (y = -0.49 x + 45.83; p < 0.05). In fact, the decrease was significant (y = -1.18 x + 83.54; p < 0.05) during the first half of the study period (1946-66), but not during the second half (1967-87). Similarly, a significant decrease in all of the specific mean annual detection rates (according to the form of leprosy and to the sex and age of patients), in the proportion of multibacillary patients among the total of newly detected cases, and in the proportion of all patients with disabilities at the onset of leprosy was observed only during the first half of the study period (1946-66). Nevertheless, when comparing age-specific cumulative detection rates, calculated by 10-year age groups over the period 1946-66, to those of the period 1967-87, an ageing of the leprosy population was noted. Finally, the decrease of mean annual detection rates was greater in the smaller populations of remote islands than in the population of Tahiti, the main island, where 70% of the total population were living during the study period. This decline was shown to correspond to an effective improvement of the leprosy situation which could be attributed, among other factors (such as economic development and systematic BCG vaccination), to the implementation of a control programme for leprosy in 1950. The introduction in 1982 of multidrug therapy for all patients suffering active leprosy has raised the hope of a subsequent decline of leprosy in French Polynesia in the near future.

Compared efficacy of repeated annual and semi-annual doses of ivermectin and diethylcarbamazine for prevention of Wuchereria bancrofti filariasis in French Polynesia. Final evaluation

In October 1989, 58 apparently healthy Polynesian Wuchereria bancrofti carriers, in whom microfilarial (mf) density was greater than or equal to 100 mf/ml, were randomly allocated to treatment groups receiving single doses of either ivermectin at 100 mcg/kg or diethylcarbamazine (DEC) at 3 and 6 mg/kg. Six months later, half of the carriers initially treated with ivermectin 100 mcg/kg or DEC 3 mg/kg were given a second similar dose while the rest were given a placebo. Six months later again, all of the carriers received a last treatment dose similar to the initial one. The results observed during the 12-month period which followed this last treatment have confirmed that (i) in terms of immediate clearance or complete negativation of microfilaremia, the efficacy of ivermectin is higher than that of DEC (at dosage of 3 or 6 mg/kg), (ii) DEC is more effective than ivermectin in sustaining the reduction of microfilaremia over a longer period of time and (iii) the efficacy of repeated single doses of either DEC 3 mg/kg or ivermectin 100 mcg/kg is much higher when given semi-annually than annually.(ABSTRACT TRUNCATED AT 250 WORDS)

Dengue 1 epidemic in French Polynesia, 1988-1989: surveillance and clinical, epidemiological, virological and serological findings in 1752 documented clinical cases

An epidemic of dengue 1 occurred in French Polynesia in December 1988 and June 1989. This paper records (i) the trend of the outbreak and its surveillance and (ii) the clinical, epidemiological and virological data obtained from 1752 documented cases. The epidemic reached its peak in February in Tahiti Island, 7 weeks after its recognition. Among 6034 suspect cases reported by sentinel physicians, 60.3% were < 20 years old. The illness was classical dengue. No fatality or case of dengue haemorrhagic fever/dengue with shock syndrome was reported. Of 4792 patients subjected to laboratory testing, 41% were confirmed as positive. The serological attack rate was c. 40%. The estimated number of dengue infections in the Windward Islands was about 20,000. Transmission was associated with Aedes aegypti. Study of documented cases showed a higher confirmation rate in both the civilian population < 15 years old (46.5%) and the susceptible French military population (47.6%) than in older civilians (31.1%, P < 0.05). Furthermore, primary dengue infections were predominant in both of the first 2 groups. The diagnosis was mostly confirmed (i) by virus isolation on day < 5 of illness and (ii) by detection of immunoglobulin (Ig) M on day > or = 5 of illness. The study showed that adequate surveillance of an epidemic requires both clinically and laboratory-based systems.

[Goiter in Tahiti]

The authors report on a prospective study about goitre in French Polynesia carried out in 1989, dealing with epidemiology and disease characterization in 39 patients. 1. Epidemiology of goitre in Tahiti; In schools: 517 children (236 boys and 281 girls) aged from 10 to 15. Prevalence rate is 1.55 p.c. (8/517); Adults: 226 adults (112 males and 114 females) aged from 50 to 65. Prevalence rate is 4.42 p.c. (10/226). 2. Case study on 39 Polynesian patients (38 females and 1 male) living in Tahiti (mean age: 35.6 years old) showing euthyroidic goitre, detected from 1989 April 1st and October 31; Goitre did not present in Tahiti any particularity. It is a pathology mainly feminine, at low evolution and late local consequences; In 3/4 of the cases, goitre is visible and more it is voluminous more modules are present; There is no iodine deficiency, and the mean value of iodine excretion (536 mcg/24 h) is very high in comparison with what is described in the literature; Presence of a high thiocyanatemia (greater than 100 mmol/l) is found in 1/4 of the patients; There is no correlation between consumption of foods well-known as cyanogenical ones and the level of thiocyanatemia; There is a correlation between the rate of thiocyanatemia and tabagism.

Single versus repeated doses of ivermectin and diethylcarbamazine for the treatment of Wuchereria bancrofti var. pacifica microfilaremia. Results at 12 months of a double-blind study

In October 1989, 58 apparently healthy Polynesian Wuchereria bancrofti carriers in whom microfilarial (mf) density was greater than or equal to 100 mf/ml were randomly allocated to treatment groups receiving single doses of either ivermectin at 100 mcg/kg or diethylcarbamazine (DEC) at 3 and 6 mg/kg. Six months later, half of the carriers initially treated with ivermectin 100 mcg/kg or DEC 3 mg/kg were given a second similar dose while the rest were given a placebo. By day 360 (6 months after retreatment), comparison of adjusted geometric mean mf counts per group indicated that (i) among the 3 treatments given once a year the DEC 6 mg/kg dose resulted in the highest efficacy, (ii) nevertheless, regarding either ivermectin 100 mcg/kg or DEC 3 mg/kg, 2 successive doses resulted in higher efficacy than one annual dose and (iii) though no significant difference could be evidenced between efficacy of ivermectin 100 mcg/kg and DEC 3 mg/kg given twice a year, DEC seemed to sustain the mf reduction for a longer period of time. During the 3 days following retreatment, adverse reactions (mild to moderate) were observed in 46% of carriers treated with microfilaricidal drugs and in 20% of those treated with placebo. These results suggest that single dose therapy with either DEC or ivermectin is safe and effective for prevention of lymphatic filariasis due to Wuchereria bancrofti in French Polynesia. The real impact on transmission by the vector, Aedes polynesiensis, of the complete negativation of microfilaremia observed during the previous part of the trial in carriers treated with ivermectin should be evaluated in a community-based trial including entomological study.(ABSTRACT TRUNCATED AT 250 WORDS)

One year evaluation of immunogenicity conferred by a Chinese hamster ovary cell recombinant hepatitis B vaccine in a French Polynesian newborn immunization programme

In 1988, a hepatitis immunization programme, using a Chinese hamster ovary (CHO) cell recombinant vaccine, was implemented for newborn children in the Austral archipelago (French Polynesia). Three different schedules were used: (i) 4 vaccine doses at months (M) 0, M1, M2 and M12; (ii) 3 vaccine doses at M0, M1, M6; and (iii) 3 vaccine doses at M0, M1, M2. Results at the one year follow-up may be summarized as follows. Of 197 infants who received one or more doses of CHO-recombinant vaccine, (i) none was an HBsAg carrier; (ii) 89.5% had anti-HBs-antibody titres greater than 10 miu/ml; and (iii) 95.9% had seroconverted for at least one of the 2 antibodies studied (anti-HBs or anti-pre-S2). After 2 doses (M0, M1), anti-HBs seroconversion rate and geometric mean titre were, respectively, 82.6% and 98.47 miu/ml. After 3 doses, seroconversion rates and geometric mean titres were, respectively, 91.1% and 200.59 miu/ml using schedule M0, M1, M2, and 100% and 1253.4 miu/ml using the M0, M1, M6 schedule. None of the 7 vaccinated neonates born to HBsAg/HBeAg positive mothers was found to be an HBsAg carrier. These preliminary results indicate that, in field conditions, vaccination with a CHO-recombinant vaccine resulted in high immunogenicity.

Prevalence of hepatitis B virus infection in the Austral archipelago, French Polynesia: identification of transmission patterns for the formulation of immunization strategies

A sero-epidemiological survey of hepatitis B virus (HBV) infection in a randomly selected sample of 957 persons from the population of the Austral Island group in French Polynesia was conducted as a first step before developing an immunization programme strategy. Prevalence rates of HBsAg ranged from 3.09% to 27% in the different islands of the group with a weighted mean of 10.48%, while the prevalence rate for at least one marker ranged from 46.91% to 81.03% with a weighted mean of 64.12%. In the 0-11 months and 1-4 years age groups, 2.08% and 10.57%, respectively, of the children were HBsAg carriers. These findings, when compared to the mean population carrier rate of 10.48%, suggest that HBV transmission occurred mostly after the first year of life. The highest prevalence rate for HBeAg positivity was in the 5-19 years age group (more than 40% of the HBsAg carriers were HBeAg positive), suggesting that contagiousness was greatest in childhood and adolescence. HBsAg was found in 11.45% of women of child-bearing age and HBeAg in 19.09% of women positive for HBsAg. It is concluded that immunization of newborns and infants, using vaccine alone, should be the most effective strategy for reducing HBV infection in the Austral Islands archipelago.

Clostridium difficile in preterm neonates

Stool specimens from premature neonates over the first month of life were examined for the presence of toxigenic Clostridium difficile and to evaluate a possible correlation between colonization and bowel disorders or prior antibiotic administration. Results showed a high isolation rate (63%) of Clostridium difficile with similar incidence in infants treated or not with antibiotics and with or without bowel disorders. Differentiation among strains according to SDS-PAGE, antibiotic susceptibility patterns and toxin production were useful to reveal cross-contamination. Both toxin-producing and non toxigenic strains were found in the infants' intestines. However, toxigenic strains were only present in infants suffering from bowel disorders and thus treated with oral antibiotics, suggesting that these factors may favour colonization by toxigenic strains.

Comparison of the in vitro activities of teicoplanin and vancomycin against Clostridium difficile and their interactions with cholestyramine

The in vitro activity of teicoplanin was compared with that of vancomycin against fecal isolates of Clostridium difficile. All strains were susceptible to both antibiotics, but teicoplanin was fourfold more active than vancomycin. Cholestyramine was found to bind teicoplanin almost completely, reducing its activity to nondetectable levels.