Håkan Janson

Actinobacillus pleuropneumoniae : pathobiology and pathogenesis of infection

Actinobacillus pleuropneumoniae causes porcine pleuropneumonia, a highly contagious disease for which there is no effective vaccine. This review considers how adhesins, iron-acquisition factors, capsule and lipopolysaccharide, RTX cytotoxins and other potential future vaccine components contribute to colonisation, to avoidance of host clearance mechanisms and to damage of host tissues.

Isolation and characterization of a novel IgD-binding protein from Moraxella catarrhalis

A novel surface protein of the bacterial species Moraxella catarrhalis that displays a high affinity for IgD (MID) was solubilized in Empigen and isolated by ion exchange chromatography and gel filtration. The apparent molecular mass of monomeric MID was estimated to ∼200 kDa by SDS-PAGE. The mid gene was cloned and expressed in Escherichia coli. The complete mid nucleotide gene sequence was determined, and the deduced amino acid sequence consists of 2123 residues. The sequence of MID has no similarity to other Ig-binding proteins and differs from all previously described outer membrane proteins of M. catarrhalis. MID was found to exhibit unique Ig-binding properties. Thus, in ELISA, dot blots, and Western blots, MID bound two purified IgD myeloma proteins, four IgD myeloma sera, and finally one IgD standard serum. No binding of MID was detected to IgG, IgM, IgA, or IgE myeloma proteins. MID also bound to the surface-expressed B cell receptor IgD, but not to other membrane molecules on human PBLs. This novel Ig-binding reagent promises to be of theoretical and practical interest in immunological research.

Effects on the Ciliated Epithelium of Protein D—Producing and —Nonproducing Nontypeable Haemophilus influenzae in Nasopharyngeal Tissue Cultures

A pair of isogenic, nontypeable Haemophilus influenzae strains, one expressing protein D and the other protein D-negative, was compared in their ability to cause damage in a human nasopharyngeal tissue culture model. Damage was assessed by measuring the ciliary beat frequency (CBF) of tissue specimens at 12 h intervals. Cultures inoculated with H. influenzae manifested a decrease in CBF beginning after 12 h, with a maximum decrease after 36 h. The impairment of ciliary function by the protein D-expressing strain was significantly greater than that caused by the protein D-negative mutant (P<.01). Tissue specimens examined by scanning and transmission electron microscopy after 24 h appeared normal. After 48 h of incubation, the protein D-expressing strain caused a significant loss of cilia. These findings suggest that protein D is involved in the pathogenesis of upper respiratory tract infections due to nontypeable H. influenzae, probably by enhancing functional and morphological damage to cilia.

LTX-109 Is a Novel Agent for Nasal Decolonization of Methicillin-Resistant and -Sensitive Staphylococcus aureus

ABSTRACT Nasal decolonization has a proven effect on the prevention of severe Staphylococcus aureus infections and the control of methicillin-resistant S. aureus (MRSA). However, rising rates of resistance to antibiotics highlight the need for new substances for nasal decolonization. LTX-109 is a broad-spectrum, fast-acting bactericidal antimicrobial drug for topical treatment, which causes membrane disruption and cell lysis. This mechanism of action is not associated with cross-resistance and has a low propensity for development of resistance. In the present study, persistent nasal MRSA and methicillin-sensitive S. aureus (MSSA) carriers were treated for 3 days with vehicle or with 1%, 2%, or 5% LTX-109. A significant effect on nasal decolonization was observed already after 2 days of LTX-109 treatment in subjects treated with 2% or 5% LTX-109 compared to vehicle (P ≤ 0.0012 by Dunnett′s test). No safety issues were noted during the 9-week follow-up period. Minimal reversible epithelial lesions were observed in the nasal cavity. The systemic exposure was very low, with a maximum concentration of drug in plasma (Cmax) at 1 to 2 h postdosing (3.72 to 11.7 ng/ml). One week after treatment initiation, LTX-109 was not detectable in any subject. Intranasal treatment of S. aureus with LTX-109 is safe and reduces the bacterial load already after a single day of treatment. Hence, LTX-109 has potential as a new and effective antimicrobial agent with a low propensity of resistance development that can prevent infections by MSSA/MRSA during hospitalization. (This study has been registered at ClinicalTrials.gov under registration no. NCT01158235.)

Fragmentation heterogeneity of 23S ribosomal RNA in Haemophilus species

The fragmentation of 23S rRNA of 23 Haemophilus influenzae strains and eight strains belonging to other Haemophilus species was investigated. Instead of intact molecules, the 23S rRNA molecules were found to be cleaved into two to five smaller conserved fragments in most strains examined, especially in H. influenzae type b (5/6) and nontypeable strains (5/5). One or two conserved potential cleavage sites were identified by PCR analysis of the strains showing a fragmented 23S rRNA pattern. The relevant nucleotide sequences were determined and compared to H. influenzae Rd, which contains intact 23S rRNA molecules. An identical 112bp long intervening sequence (IVS) at position 542 and a conserved 121-123bp IVS sequence at position 1171 were found in two H. influenzae type b strains and one nontypeable strain. Among the strains with fragmented 23S rRNA, nearly half showed a heterogeneous cleavage pattern due to the dispersion of IVSs among different 23S rRNA operons. The localization of the conserved H. influenzae IVSs coincided well with the extensively studied IVSs among other bacteria, but differed in nucleotide sequence from any other reported IVSs. Therefore, the IVSs of Haemophilus 23S rRNA may originate from a common source that is independent of other bacteria.

Decline of the new Swedish variant of Chlamydia trachomatis after introduction of appropriate testing

Objective The longitudinal epidemiological development of the new variant of Chlamydia trachomatis was studied after appropriate testing procedures had been introduced when the strain was detected in 2006. Methods The number of cases of the new variant of C trachomatis was followed from 2007 through 2011 from the laboratory records. Testing for C trachomatis is centralised to one laboratory with around 80–85 000 persons being tested annually in a population of 1.1 million. Results During the 5-year period, 410 973 patients were tested of which 25 723 cases were positive. The proportion of the new variant of all positive cases declined from 30% in 2007 to 6% in 2011. While the number of the new variant of C trachomatis declined, the ordinary wild-type strains remained largely unchanged. Conclusions A selective decline of the new variant of C trachomatis has occurred after appropriate laboratory testing was introduced. A new balance point between 5% and 10% for the new variant seems to be gradually approached.

Differences in genetic and transcriptional organization of the glpTQ operons between Haemophilus influenzae type b and nontypeable strains.

The glpTQ operon of Haemophilus influenzae type b (Hib) and nontypeable H. influenzae (NTHi) strains is highly conserved, except for a 1.4-kb glpTQ intergenic region that was found in most Hib strains. The presence of this intergenic region results in divergent glpTQ transcriptional profiles for Hib and NTHi where Hib strains appear to have evolved an alternative promoter for glpQ expression. Based on the intergenic regions low G+C content, we speculate that this DNA fragment was acquired by lateral transfer.

The majority of MRSA colonized children not given eradication treatment are still colonized one year later. Systemic antibiotics improve the eradication rate

Abstract Background: Colonization with methicillin-resistant Staphylococcus aureus (MRSA) can cause endogenously derived infections and be a source of transmission to other people. Neither colonization time of asymptomatic MRSA colonization nor the effect of treatment aiming at MRSA eradication in children has been thoroughly investigated. Methods: Two hundred ninety-three children <18 years in the mandatory follow-up program for MRSA-carriers in Malmö, Sweden were evaluated. Samples from the throat, nares, perineum and skin lesions from each child were screened for MRSA with a PCR-based broth enrichment method. PVL presence and spa-type were evaluated in a majority of cases. The sampling was repeated approximately every 6 month after initial detection. When three consecutive sets of negative samples during at least a 6-month period were obtained, the MRSA was considered permanently eradicated. MRSA eradication treatment given, on clinical grounds during follow-up, was noted. Results: One year after detection 62% of the untreated children were still MRSA positive and after 2 years 28%. MRSA throat colonization and having MRSA positive household contacts significantly prolonged the observed colonization time. Topical MRSA eradication treatment was successful in 36% of cases and in 65% if systemic antibiotics were added. Presence of PVL correlated with shorter observed colonization time in the older age group and with increased eradication success among throat carriers. Conclusion: MRSA throat colonization and having MRSA positive household contacts prolongs the time of MRSA colonization in children. Systemic antibiotics enhance the effect of MRSA eradication treatment.