Biomedical subjects

J Jonasson

Publications and source records attributed to J Jonasson.

At least 19 recordsLinked to original sources

PubMed2005

Phene Plate (PhP) biochemical fingerprinting. A screening method for epidemiological typing of enterococcal isolates.

Pulsed-field gel electrophoresis (PFGE) is currently considered the gold standard for genotyping of enterococci. However, PFGE is both expensive and time-consuming. The purpose of this study was to investigate whether the PhP system can be used as a reliable clinical screening method for detection of genetically related isolates of enterococci. If so, it should be possible to minimize the number of isolates subjected to PFGE typing, which would save time and money. Ninety-nine clinical enterococcal isolates were analysed by PhP (similarity levels 0.90-0.975) and PFGE (similarity levels < or =3 and < or =6 bands) and all possible pairs of isolates were cross-classified as matched or mismatched. We found that the probability that a pair of isolates (A and B) belonging to the same type according to PhP also belong to the same cluster according to PFGE, i.e. p(A(PFGE)=B(PFGE) * A(PhP)=B(PhP)), and the probability that a pair of isolates of different types according to PhP also belong to different clusters according to PFGE, i.e. p(A(PFGE) not equalB(PFGE) * A(PhP) not equalB(PhP)), was relatively high for E. faecalis (0.86 and 0.96, respectively), but was lower for E. faecium (0.51 and 0.77, respectively). The concordance which shows the probability that PhP and PFGE agree on match or mismatch was 86%-93% for E. faecalis and 54%-66% for E. faecium, which indicates that the PhP method may be useful for epidemiological typing of E. faecalis in the current settings but not for E. faecium.

Bacterial Typing Techniques↗

PubMed2003

Clustering of enterococcal infections in a general intensive care unit.

This is a retrospective study comparing patients' characteristics, antibiotic consumption and environmental contamination before the impact of a new regimen of intensified infection control measures in a general intensive care unit (ICU) at a university-affiliated tertiary-care teaching hospital. The new regimen consisted of (1) reorganization of patient rooms (2) improved hygienic measures including strict hygiene barrier nursing (3) more isolated patient care and (4) more restrictive use of antibiotics. The regimen was introduced after a cluster of enterococcal infections. All patients admitted to the ICU from 1 March 1995 to 28 february 1997 were included. A study period of 12 months after reorganization of the ward was compared with the 12 months immediately before it. The antibiotic consumption, the individual patient's severity of disease (APACHE score), and the extent of therapeutic interventions (TISS score) were recorded. Enterococci were typed biochemically, antibiograms were established and the relation between the isolates was investigated with pulsed-field gel electrophoresis. The bacteriological results and the patient data suggested a hospital-acquired spread as the cause of the ICU enterococcal outbreak. After implementation of the new regimen, we observed a reduction in the rate of enterococcal bloodstream infections from 3.1 to 1.8%. The consumption of antibiotics fell from 6.11 to 4.24 defined daily doses per patient. The introduction of strict hygiene and barrier nursing, more restrictive use of antibiotics, isolation of infected patients, thorough cleaning and disinfection of the unit was followed by an absence of enterococcal infection clustering and reduction in incidence of enterococcal bacteraemia. We were not able to determine whether the reduction in antibiotic consumption was due to the intervention programme.

Adult↗

PubMed2001

Differential virulence-gene mRNA expression in coccoid forms of Helicobacter pylori.

Controversy exists whether coccoid forms of Helicobacter pylori maintain transcriptional and translational processes. The aim of the present study was to investigate mRNA levels in coccoid H. pylori and, if possible, to establish a correlation with the state of nonrandom fragmentation of rRNA in those cells. For that purpose, UreA, UreI, CagA, VacA, SodB, and Hsp60 mRNA levels in bacillary and coccoid forms of H. pylori CCUG 17874(T), H. pylori 26695, and H. pylori J99, respectively, were studied by means of a multiplex reverse-transcription PCR assay and Southern blot analysis of the RT-PCR-amplified products. Nonrandom fragmentation of 23S rRNA was assessed by a recently described assay. Virulence-gene-derived mRNA transcripts were visualized in DNase I-treated RNA preparations. All three strains revealed the presence of different mRNA patterns in bacillary and coccoid forms. Putative promoter sequences similar to the consensus Escherichia coli -10 hexamer TATAAA box were present in all six virulence genes analyzed. Moreover, the decrease seen in mRNA levels during conversion into the coccoid form appeared to correlate with the 23S rRNA nonrandom fragmentation pattern. The present data indicate that modulation of virulence-gene expression is differently regulated in bacillary and coccoid H. pylori.

Antigens, Bacterial↗

PubMed2001

Rapid molecular identification and subtyping of Helicobacter pylori by pyrosequencing of the 16S rDNA variable V1 and V3 regions.

We describe here the use of real-time DNA sequence analysis of Helicobacter pylori 16S rRNA gene fragments by pyrosequencing for rapid molecular identification and subtyping of clinical isolates based on DNA sequence heterogeneity within the variable V1 and V3 regions. Six individual 16S rDNA V1 alleles (position 75-100) were identified in 23 clinical isolates obtained from gastric biopsy specimens. Eleven of these revealed sequence identities with H. pylori 26695 and one was identical with the rrn genes in strain J99. The other V1 alleles showing single or double nucleotide mutations or single nucleotide insertions could be divided into four groups with 5, 4, 1, and 1 isolates each. Two out of 25 isolates demonstrated single C to T transitions in the V3 region (position 990-1020). The present findings show that subtle DNA sequence variation occurs sufficiently often in the 16S rDNA variable V1 and V3 regions of H. pylori to provide a consistent system for subtyping.

Bacterial Typing Techniques↗

PubMed2001

Identification of enterococcal isolates by temperature gradient gel electrophoresis and partial sequence analysis of PCR-amplified 16S rDNA variable V6 regions.

Based on partial sequence analysis of PCR-amplified 16S rDNA variable V6 regions of 14 enterococcal type strains, Enterococcus faecalis, Enterococcus mundtii, Enterococcus gallinarum, Enterococcus avium, Enterococcus raffinosus and Enterococcus saccharolyticus showed characteristic sequence motifs which made it possible to separate them into six individual species lines. Furthermore, two species cluster groups could be identified, including (i) Enterococcus faecium, Enterococcus durans, Enterococcus hirae, Enterococcus malodoratus, and (ii) Enterococcus casseliflavus/Enterococcus flavescens, Enterococcus pseudoavium, Enterococcus dispar and Enterococcus sulfureus. There were identical DNA sequences in the V6 region within each group. Temporal temperature gradient gel electrophoresis (TTGE) of the PCR products from 16 type strains, 12 enterococcal reference strains and 8 clinical isolates revealed that a single nucleotide divergence in DNA sequences was sufficient for separation, identification and division of the studied enterococcal strains into corresponding TTGE profiles. It was concluded that partial DNA sequence analysis and TTGE profiling of PCR-amplified 16S rDNA variable V6 regions provide useful tools for the identification of clinically important Enterococcus spp.

Bacterial Typing Techniques↗

PubMed2001

Arbitrarily primed PCR and sequencing of 16S rDNA for epidemiological typing and species identification of Burkholderia cepacia isolates from Swedish patients with cystic fibrosis reveal genetic heterogeneity.

To investigate whether arbitrarily primed (AP)-PCR and/or 16S rDNA sequencing could be used as rapid methods for epidemiological typing and species identification of clinical Burkholderia isolates from patients with cystic fibrosis (CF), a total of 39 clinical B. cepacia isolates, including 33 isolates from 14 CF patients, were fingerprinted. ERIC-2 primer was used for AP-PCR. The AP-PCR clustering analysis resulted in 14 different clusters at a 70% similarity level. The AP-PRC patterns were individual despite considerable similarities. To sequence rDNA, a broad-range PCR was applied. The PCR product included four variable loops (V8, V3, V4 and V9) of the 16S ribosomal small subunit RNA gene. The multiple sequence alignment produced 12 different patterns, 5 of them including more than one isolate. Heterogeneity of the bases in the V3 region, indicating the simultaneous presence of at least two different types of 16S rRNA genes in the same cell, was revealed in 10 isolates. Most of the CF patients were adults who had advanced disease at follow-up. Both the sequencing and the AP-PCR patterns revealed genetic heterogeneity of isolates between patients. According to the results obtained, AP-PCR could advantageously be used for epidemiological typing of Burkholderia, whereas partial species identification could effectively be obtained by sequencing of the V3 region of the 16S RNA gene.

Adolescent↗

PubMed2001

Probing 23S ribosomal RNA cleavage sites in coccoid Helicobacter pylori.

BACKGROUND: Previous studies have revealed that extensive nonrandom fragmentation of ribosomal RNA occurs during conversion of Helicobacter pylori to the coccoid form. The 16S rRNA fragmentation has been characterised in some detail. The aim of the present study was to define corresponding cleavage-sites in the 3'-half of the 23S rRNA molecule. MATERIALS AND METHODS: Northern blot analysis using 23S rRNA specific antisense riboprobes and a 5'-end-labelled oligonucleotide probe was used to analyse the 23S rRNA fragmentation pattern in coccoid H. pylori type strain CCUG 17874T and H. pylori 26695, for which the genome has been sequenced. A double-stranded cDNA-dependent (ds-cDNA) primer-extension analysis technique using 23S rRNA ds-cDNA and a primer targeting the vicinity of the peptidyl-transferase centre was used to determine cleavage sites at the nucleotide level. RESULTS: We report here the mapping of putative cleavage sites within domains IV and V, enclosing the peptidyl transferase centre, in the 3'-half of the 23S rRNA molecule. Three cleavage sites were located in domain IV. Two other cleavage sites were located in the peptidyl transferase centre, and one presumptive multiple-break site between helices 77 and 78 in domain V. The DNA motifs were different from the postulated A + U rich single-strand cleavage sites recognised by RNase E, which has been implicated in rRNA degradation in Escherichia coli. CONCLUSIONS: The present analysis suggests that a hitherto unknown mechanism is responsible for the nonrandom fragmentation of rRNA in coccoid H. pylori, which may have important consequences for the growth, and survival of the bacterium.

Base Sequence↗

PubMed2000

Detection of vancomycin resistance genes combined with typing of Enterococci by means of multiplex PCR amplification and multiple primer DNA sequencing.

A multiplex PCR assay for the detection of vancomycin resistance (van) genes in enterococci was established. Primers targeting the 16S rRNA gene were included in the reaction mixture. Multiple-primer DNA sequencing of the PCR products provided species identification through partial nucleotide sequences of 16S rRNA genes, as well as confirmation of the correct identification of vanA, vanB, vanC-1, and vanC-2/3 genotypes. Thirty-nine enterococcal clinical isolates and type strains were examined for the presence of vancomycin resistance determinants. Twelve other isolates from a clinical reference collection (some of them having vanA, vanB, vanC-1, or vanC-2/3 genotypes) were used as controls. Hybridization and partial DNA sequence analysis of multiplex PCR products revealed that none of the clinical isolates had a vanA genotype and only one had a vanB genotype. vanC-1 was found in three clinical isolates, and vanC-2/3 in one. Results obtained with the reference and type strains were in agreement with earlier results.

Bacterial Typing Techniques↗

PubMed2000

Evidence for a common Spinocerebellar ataxia type 7 (SCA7) founder mutation in Scandinavia.

Spinocerebellar ataxia type 7 (SCA7) is a neuro-degenerative disorder characterised by progressive cerebellar ataxia and macular degeneration. SCA7 is one of the least common genetically verified autosomal dominant cerebellar ataxias (ADCAs) in the world (4.5 to 11.6%), but in Sweden and Finland SCA7 is the most commonly identified form of ADCA. In an inventory of hereditary ataxias in Scandinavia (Sweden, Norway, Denmark and Finland) we identified 15 SCA7 families, eight in Sweden and seven in Finland, while no cases of SCA7 could be found in Norway or Denmark. We examined whether the relatively high frequency of SCA7 families in Sweden and Finland was the result of a common founder effect. Only two out of 15 families could be connected genealogically. However, an extensive haplotype analysis over a 10.2 cM region surrounding the SCA7 gene locus showed that all 15 families studied shared a common haplotype over at least 1.9 cM. This strongly suggests that all Scandinavian SCA7 families originate from a common founder pre-mutation.

Ataxin-7↗

PubMed2000

Profiling of bacterial flora in gastric biopsies from patients with Helicobacter pylori-associated gastritis and histologically normal control individuals by temperature gradient gel electrophoresis and 16S rDNA sequence analysis.

The aim of this study was to establish bacterial profiles in gastric biopsy specimens from patients with Helicobacter pylori-associated gastritis by means of temporal temperature gradient gel electrophoresis (TTGE) of PCR-amplified 16S rDNA fragments. Specimens from eight patients with asymptomatic gastritis and five histologically normal controls revealed a Helicobacter-specific band in the TTGE profile with increased amounts of Helicobacter-specific DNA in the biopsies from most of the gastritis patients. DNA from other genera including Enterococcus, Pseudomonas, Streptococcus, Staphylococcus and Stomatococcus was also found in the stomach. In the absence of gastric inflammation, Helicobacter spp. appeared to be part of a complex, presumably indigenous microbial flora found in the biopsy specimens from the stomach.

Biopsy↗

PubMed1998

Identification of Helicobacter in gastric biopsies by PCR based on 16S rDNA sequences: a matter of little significance for the prediction of H. pylori-associated gastritis?

The aim of the present study was to correlate molecular evidence of the presence of Helicobacter pylori in gastric biopsy samples, based on analysis of 16S rDNA, vacuolating toxin (vacA), urease A (ureA) and cagA genes, with the clinical, histological and serological findings in patients with H. pylori-associated gastritis. Fresh biopsy samples were collected from the gastric antrum and corpus of 22 asymptomatic volunteers with or without H. pylori-associated gastritis. Total DNA was extracted from the biopsy material and subjected to 16S rDNA PCR amplification, Southern blotting and 16S rDNA sequence analysis of the PCR products. The vacA, ureA and cagA genes were characterised by PCR amplification and Southern blot analysis. Based on partial 16S rDNA sequence analysis, DNA belonging to the genus Helicobacter was detected in gastric biopsy samples from 20 of 22 subjects, including seven of nine histologically and serologically normal controls. Six of 20 partial 16S rDNA sequences revealed variations within variable regions V3 and V4 that deviated from those of the H. pylori type strain ATCC 4350T and, therefore, possibly represented other species of Helicobacter. VacA genes identical with those of the type strain were found predominantly in the subjects with H. pylori gastritis, and all the patients except one were found to be cagA-positive. There was no evidence of false positive PCR reactions. In conclusion, the PCR-based molecular typing methods used here were apparently too sensitive when applied to the detection of H. pylori in human gastric tissues. The lack of quantitative analysis makes them inappropriate as clinical tools for the diagnosis of H. pylori-associated gastritis, despite the fact that they provide a qualitative and sensitive tool for the detection and characterisation of H. pylori in the gastrointestinal tract.

Adult↗

PubMed1998

Non-random fragmentation of ribosomal RNA in Helicobacter pylori during conversion to the coccoid form.

The integrity of DNA and ribosomal RNAs in exponentially growing (bacillary) and ageing stationary phase (coccoid) cultures of Helicobacter pylori type strain CCUG 17874 was investigated. Extensive non-random fragmentation of rRNAs was observed during the conversion to the coccoid form. Beside a small proportion of full-length 16S and 23S rRNA that was always present, the majority of both 16S and 23S rRNA molecules showed distinct highly specific fragmentation patterns. The 16S rRNA fragmentation was characterised in detail by means of Northern blot and primer extension analysis. One cleavage site was located within the highly conserved U5 region (position about 920). The results could not be attributed to the presence of intervening sequences in the 16S and 23S rRNA genes.

Blotting, Northern↗

PubMed1996

Polymerase chain reaction for the detection of Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Burkholderia cepacia in sputum of patients with cystic fibrosis.

Occurrence of Pseudomonas aeruginosa, Stenotrophomonas (Xanthomonas) maltophilia and Burkholderia (Pseudomonas) cepacia in sputum of cystic fibrosis (CF) patients was demonstrated with a simple and rapid polymerase chain reaction (PCR) technique. The PCR was performed with a set of three primer pairs based on 16S rRNA sequences after sputum preparation with dithiothreitol and NaOH lysis. All three pathogens could be individually detected by the use of this technique. To prevent carry-over contamination, dUTP and uracil-N-glycosylase were included in the reaction. The amplicons were visualized by agarose gel electrophoresis. Sputum culture was performed on all samples. Ninety specimens from CF patients were analysed. The sensitivity for the detection of P. aeruginosa was 37/40 (93%) compared to culture. Bacterial growth of P. aeruginosa was found in three cases, where PCR amplicons were not detected, while PCR was positive in five cases, where culture did not reveal the presence of this bacterium. For this reason, the specificity was 45/50 (90%). For S. maltophilia, the PCR was less sensitive than culture (positive in three of six cases). In our series, B. cepacia was detected by culture in one case and this was also detected by PCR. There were no false-positive PCR results regarding S. maltophilia or B. cepacia. Thus, combined PCR-based detection of these three clinically relevant bacteria in sputum samples from CF patients can be performed by a reliable technique in a relatively simple manner. The present data indicate a high sensitivity and specificity for P. aeruginosa. The lower sensitivity observed for the detection of S. maltophilia in sputum and B. cepacia, as estimated from laboratory strains, may depend on PCR conditions and genetic heterogeneity, respectively. The greatest gains with this method can be made when it is used for the early detection of P. aeruginosa in sputum-producing CF patients.

Adult↗

PubMed1996

Expression of stem-cell factor and its receptor c-kit protein in normal testicular tissue and malignant germ-cell tumours.

The proto-oncogene c-kit and its ligand stem-cell factor (SCF) may play an important role in the development of normal and malignant testicular tissue. This study investigates the presence of SCF and c-kit protein in 32 orchiectomy specimens of patients with testicular cancer, in 5 specimens of normal testicular tissue and in three established non-seminomatous germ-cell cancer cell lines (H12.1, H32, 577ML) by an immunohistochemical approach. Out of 9 testicular cancer specimens classified as pure seminomas, 7 (78%) showed a strong immunohistochemical reaction for both SCF and c-kit protein on the surface of the tumour cells. Fourteen non-seminomatous germ-cell tumours composed of embryonal carcinoma were completely negative for both SCF and c-kit proteins and only faint positivity was found in 6 tumours (26%). Differentiated teratomatous structures within the specimens on non-seminomatous tumours showed a strong immunohistochemical reaction for SCF and c-kit protein in 8 of 11 (73%) cases. All three testicular cancer cell lines showed only faint staining reactions for c-kit protein and none for SCF. No secretion of SCF by the three lines in vitro was detected. The addition of high concentrations of SCF (100 ng/ml) to the testicular cancer cell lines in culture conditions without fetal calf serum resulted in a 1.4 to 3-fold growth stimulation compared to cell growth in serum-free medium alone. This effect was not detectable when the cells were cultured in serum-containing media. In the normal testicular tissue the germ-cells displayed a strong immunohistochemical reaction for c-kit protein while SCF positivity was found at the tubular membrane and on the surface of Sertoli cells. The SCF/c-kit system may possess a regulatory function in normal testicular tissue by possibly providing the microenvironment necessary for spermatogenesis. With the development of testicular cancer, this regulatory system seems to be lost, particularly in non-seminomatous germ-cell tumours. A growth-stimulatory effect of high concentrations of SCF on non-seminomatous testicular cancer cell lines can be detected only in culture conditions with serum-free media. The effects achievable by the combination of SCF with other growth factors need to be further studied, as well as the role of the c-kit/SCF regulatory system for normal spermatogenesis and its possible implications for the understanding and treatment of male infertility.

Germinoma↗

PubMed1996

Persistence of nontypeable Haemophilus influenzae in adenoid macrophages: a putative colonization mechanism.

That nontypeable H. influenzae (NTHI) can reside intracellularly in human adenoid tissue has been suggested by use of in situ hybridization of a fluorescein labelled 16S rRNA-targeted oligonucleotide probe (FISH). Adenoid tissues from 43 children operated on in a clinically infection-free interval were investigated. FISH revealed H. influenzae in macrophage-like cells, located subepithelially in the crypts in all 43 adenoids. Furthermore, H. influenzae was detected in 22/22 adenoids using immunohistochemistry with the monoclonal antibody MAHI-3 recognizing a conserved H. influenzae LPS inner-core region. FISH and staining with monoclonal antibodies against immunophenotypic markers were performed simultaneously in order to characterize the cellular interrelations in this microenvironment. The findings of widespread presence of H. influenzae in cells of which some strongly expressed the CD14 marker of the monocyte/macrophage lineage may correspond to an important aspect of the colonization mechanisms whereby NTHI persists in the nasopharynx of children.

Adenoids↗

PubMed1995

Monoclonal antibodies against Haemophilus ducreyi lipooligosaccharide and their diagnostic usefulness.

Monoclonal antibodies against the lipooligosaccharide of Haemophilus ducreyi were produced. Two of them, MAHD6 and MAHD7, were found to be relatively, although not absolutely, specific and reacted with nearly all strains of Haemophilus ducreyi tested: 59 of 60 and 60 of 60, respectively. The diagnostic usefulness of MAHD7 was assessed. Clinical specimens collected in Zambia from patients with genital ulcers were tested using indirect immunofluorescence (IF), enzyme immunoassay (EIA), the polymerase chain reaction (PCR) and bacterial culture. Compared with culture, IF had a sensitivity of 100%; compared with PCR, sensitivity was 89%. The corresponding figures for the EIA were 83% and 74%, respectively. The sensitivity of culture compared with PCR was 63%. The results suggest that IF on genital smears using MAHD7 might be an excellent tool for the diagnosis of chancroid in high-prevalence populations. However, further evaluation of the specificity of this test is needed.

Adolescent↗

PubMed1995

Monoclonal antibodies against Haemophilus lipopolysaccharides: clone DP8 specific for Haemophilus ducreyi and clone DH24 binding to lacto-N-neotetraose.

Mouse monoclonal antibodies (MAbs) DP8 [immunoglobulin G1(kappa)] and DH24 [immunoglobulin M(kappa)], which are specific for Haemophilus ducreyi lipopolysaccharide (LPS), were generated by fusing mouse myeloma NS0 cells with spleen cells of BALB/c mice immunized with a total membrane preparation of H. ducreyi. MAb DP8 reacted in whole-cell enzyme immunoassay (EIA) and colony dot immunoblotting with all 50 strains of H. ducreyi but not with any other bacteria tested, which suggests an exposed and species-specific epitope on the H. ducreyi cell surface. This conclusion was supported by the finding that DP8 bound to all six H. ducreyi LPSs tested but not to any of the Haemophilus influenzae or enterobacterial LPSs or synthetic glycoconjugates. The MAb DH24 bound to 43 of 50 strains of H. ducreyi and to few strains of H. influenzae, Neisseria gonorrhoeae, and Neisseria meningitidis, as evaluated by whole-cell EIA and colony dot immunoblotting. The MAb DH24 reacted with five of the six H. ducreyi LPSs tested and with the lacto-N-neotetraose (Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc) series of synthetic glycoconjugates, as determined by EIA. By using polysaccharides obtained after both mild acidic hydrolysis and strong alkali treatment and dephosphorylated samples as inhibitors of the MAbs binding to H. ducreyi LPS antigens, it could be shown that phosphate groups were essential for the binding of DP8 to LPS but that they did not affect antigenic recognition by DH24. None of the MAbs bound to isolated lipid A, but aggregation caused by the fatty acids of lipid A was essential for epitope recognition.

Animals↗

PubMed1995

Turnover of nonencapsulated Haemophilus influenzae in the nasopharynges of otitis-prone children.

Restriction enzyme analysis of total genomic DNA was applied to study the epidemiology of nontypeable Haemophilus influenzae (NTHI) isolated from the nasopharynges of children with recurrent acute otitis media (AOM). The turnover of strains, as judged from genetic fingerprinting of a total of 213 H. influenzae isolates collected prospectively during a 2-year study period from 38 children under 3 years of age, was examined in relation to episodes of AOM as well as to courses of antibiotic treatment. The children were selected if they had had at least one episode of AOM before 1 year of age and if more than two nasopharyngeal isolates of H. influenzae were recovered. The 213 H. influenzae isolates (90% NTHI) recovered corresponded to 128 different DNA fingerprints. Fifty-eight percent of the fingerprints were observed only once, whereas 42% appeared on two or more occasions in isolates from the same individual or in close relatives, i.e., brothers and sisters. Sixty-seven percent of these strains had a minimum colonization period of 2 months or less. Intermittent nasopharyngeal colonization periods longer than 5 months could be demonstrated for 13% of the strains. The present data suggest that intermittent colonization is due to endogenous reinfections. Genetically identical NTHI strains from unrelated individuals were never identified. As expected from the observation of a relatively high proportion of persistent colonizations, no correlation was found between episodes of AOM and the acquisition of new strains of H. influenzae, nor was any direct relation between antimicrobial therapy and the elimination of nasopharyngeal colonization with a particular strain of H. influenzae observed.

Anti-Bacterial Agents↗