Increased recovery of Moraxella catarrhalis and Haemophilus influenzae in association with group A beta-haemolytic streptococci in healthy children and those with pharyngo-tonsillitis

The inflamed tonsils harbour numerous types of bacteria, alone or in combination with group A beta-haemolytic streptococci (GABHS). The cohabitation of the tonsils by GABHS and certain other bacterial species may contribute to the inflammatory process and the failure of penicillin therapy. This study evaluated the recovery of Moraxella catarrhalis, Haemophilus influenzae, Staphylococcus aureus and Streptococcus pneumoniae in association with GABHS in healthy children and those with acute pharyngo-tonsillitis (APT). Pharyngo-tonsillar cultures were obtained from 548 children with APT and 866 healthy children. GABHS was recovered from 112 (20.4%) children with APT. Of the 114 H. influenzae isolates, 32 were recovered in association with GABHS (29% of all patients who had GABHS) and 82 were isolated without GABHS (19%) (P=0.0267). Of the 69 M. catarrhalis isolates, 25 were recovered in association with GABHS (22% of all patients who had GABHS) and 44 were isolated without GABHS (10%) (P=0.0012). In contrast, there was no association between the isolation of GABHS and the recovery of Staph. aureus or Strep. pneumoniae. GABHS was recovered from 104 (12%) healthy children. Of the 69 M. catarrhalis isolates, 24 were recovered in association with GABHS (23% of all patients who had GABHS) and 80 were isolated without GABHS (10%) (P=0.006). There was no association between the isolation of GABHS and the recovery of H. influenzae, Staph. aureus or Strep. pneumoniae. This study demonstrates an association between the recovery of GABHS and H. influenzae and M. catarrhalis from pharyngo-tonsillar cultures of patients with APT and M. catarrhalis from pharyngo-tonsillar cultures of healthy children.

The respiratory pathogen moraxella catarrhalis binds to laminin via ubiquitous surface proteins A1 and A2

Moraxella catarrhalis is one of the leading causes of exacerbations in chronic obstructive pulmonary disease (COPD). In the present article, we show that moraxella (n=15) binds to the major basement-membrane glycoprotein laminin, which is thickened in the airways of smokers. Using clinical strains of M. catarrhalis and their corresponding ubiquitous surface protein (Usp) A1/A2 mutants, we demonstrate that UspA1 and UspA2 are important for the laminin interaction. Binding assays with recombinant proteins demonstrated that the binding regions are localized within the N-terminal fragments, where both proteins form a globular head. Thus, UspA1/A2-dependent interactions with laminin might promote bacterial adhesion, particularly in smokers with COPD.

Cold shock response of the UspA1 outer membrane adhesin of Moraxella catarrhalis

Colonization of the human nasopharynx exposes Moraxella catarrhalis, a common cause of otitis media in children and exacerbations of chronic obstructive pulmonary disease in adults, to sudden downshifts in temperature, occurring when the host breathes cold air. We investigated whether in vitro cold shock influences the expressions of the outer membrane adhesins UspA1 and hemagglutinin, which are considered virulence factors, and of an M. catarrhalis homolog of recA, a housekeeping gene, which in Escherichia coli is induced by cold shock. Quantitative real-time reverse transcriptase PCR was used for measuring mRNA copy number. A screening experiment revealed that a cold shock at 26 degrees C maximally induced the copy number of uspA1. In comparison with 37 degrees C conditions, a 1-hour cold shock at 26 degrees C increased copy numbers of uspA1 and recA by 2.5-fold (11.2 +/- 1.8 versus 4.5 +/- 0.8 copies/CFU) and 2.7-fold (0.30 +/- 0.10 versus 0.11 +/- 0.06), respectively, but did not induce transcription of hag. Exposure to 26 degrees C increased surface expression of UspA1, as assessed by fluorescence-activated cell sorter analysis, and resulted in a significant increase in adherence of strain O35E to Chang human conjunctival cells (97.1% +/- 2.0% versus 48.3% +/- 9.2% at 37 degrees C; P = 0.01). Cold shock induction of uspA1 and recA was detected in strains belonging to either phylogenetic subpopulation of M. catarrhalis (16S rRNA types 1 and 2/3) and was most pronounced in type 2/3 strains (4- to 25-fold for uspA1), which do not express detectable amounts of UspA1 protein at 37 degrees C. These data indicate that cold shock at a physiologically relevant temperature of 26 degrees C induces the expression of at least one virulence factor (UspA1). To our knowledge, no similar data are available for other nasopharyngeal pathogens.

Moraxella catarrhalis bacterium without endotoxin, a potential vaccine candidate

Lipooligosaccharide (LOS) is a major surface component of Moraxella catarrhalis and a possible virulence factor in the pathogenesis of human infections caused by this organism. The presence of LOS on the bacterium is an obstacle to the development of vaccines derived from whole cells or outer membrane components of the bacterium. An lpxA gene encoding UDP-N-acetylglucosamine acyltransferase responsible for the first step of lipid A biosynthesis was identified by the construction and characterization of an isogenic M. catarrhalis lpxA mutant in strain O35E. The resulting mutant was viable despite the complete loss of LOS. The mutant strain showed significantly decreased toxicity by the Limulus amebocyte lysate assay, reduced resistance to normal human serum, reduced adherence to human epithelial cells, and enhanced clearance in lungs and nasopharynx in a mouse aerosol challenge model. Importantly, the mutant elicited high levels of antibodies with bactericidal activity and provided protection against a challenge with the wild-type strain. These data suggest that the null LOS mutant is attenuated and may be a potential vaccine candidate against M. catarrhalis.

Ionic binding of C3 to the human pathogen Moraxella catarrhalis is a unique mechanism for combating innate immunity

Moraxella catarrhalis ubiquitous surface proteins A1 and A2 (UspA1/A2) interfere with the classical pathway of the complement system by binding C4b-binding protein. In this study we demonstrate that M. catarrhalis UspA1 and A2 noncovalently and in a dose-dependent manner bind both the third component of complement (C3) from EDTA-treated serum and methylamine-treated C3. In contrast, related Moraxella subspecies (n = 13) or other human pathogenic bacteria (n = 13) do not bind C3 or methylamine-treated C3. Experiments with recombinant proteins and M. catarrhalis mutants devoid of UspA1/A2 revealed that UspA1/A2 exert their actions by absorbing and neutralizing C3 from serum and restrain complement activation. UspA2 was responsible for most of the effect, and the Moraxella mutant lacking UspA2 was more sensitive to the lytic effect of human serum compared with the wild type. Interestingly, among the large number of bacteria analyzed, only M. catarrhalis has this unique ability to interfere with the innate immune system of complement by binding C3.

Roles of 3-deoxy-D-manno-2-octulosonic acid transferase from Moraxella catarrhalis in lipooligosaccharide biosynthesis and virulence

Lipooligosaccharide (LOS), a major outer membrane component of Moraxella catarrhalis, is a possible virulence factor in the pathogenesis of human infections caused by the organism. However, information about the roles of the oligosaccharide chain from LOS in bacterial infection remains limited. Here, a kdtA gene encoding 3-deoxy-D-manno-2-octulosonic acid (Kdo) transferase, which is responsible for adding Kdo residues to the lipid A portion of the LOS, was identified by transposon mutagenesis and construction of an isogenic kdtA mutant in strain O35E. The resulting O35EkdtA mutant produced only lipid A without any core oligosaccharide, and it was viable. Physicochemical and biological analysis revealed that the mutant was susceptible to hydrophobic reagents and a hydrophilic glycopeptide and was sensitive to bactericidal activity of normal human serum. Importantly, the mutant showed decreased toxicity by the Limulus amebocyte lysate assay, reduced adherence to human epithelial cells, and enhanced clearance in lungs and nasopharynx in a mouse aerosol challenge model. These data suggest that the oligosaccharide moiety of the LOS is important for the biological activity of the LOS and the virulence capability of the bacteria in vitro and in vivo. This study may bring new insights into novel vaccines or therapeutic interventions against M. catarrhalis infections.

Carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-binding recombinant polypeptide confers protection against infection by respiratory and urogenital pathogens

The human-specific pathogens Neisseria meningitidis, N. gonorrhoea, Haemophilus influenzae and Moraxella catarrhalis share the property of targeting the carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) expressed on human epithelia. CEACAMs are signalling receptors implicated in cell adhesion and regulation of several physiological functions. Their targeting by pathogens can lead to tissue invasion. Although the CEACAM-binding ligands of the bacteria are structurally diverse, they target a common site on the receptor. We have generated a recombinant polypeptide that blocks the interactions of the mucosal pathogens with human epithelial cells and antibodies against it inhibit M. catarrhalis interactions with the receptor. As such, it is a potential antimicrobial agent to prevent infection via a strategy unlikely to promote bacterial resistance and a vaccine candidate against M. catarrhalis. In addition, it could serve more widely as a novel research tool and as a potential therapeutic agent in CEACAM-based physiological disorders.

Identification of a conserved Moraxella catarrhalis haemoglobin-utilization protein, MhuA

Moraxella catarrhalis is a leading cause of acute otitis media in children and is a cause of respiratory disease in adults with underlying lung disease. This organism is a strict human pathogen that has an absolute requirement for iron in order to grow and cause disease. Previous studies identified transferrin and lactoferrin receptors used by M. catarrhalis to obtain iron from the human host, yet other iron-acquisition systems remain undefined. In this study, it is demonstrated that this strict mucosal pathogen can utilize haemoglobin (Hb) as a sole source of iron for growth. A novel 107 kDa outer-membrane protein involved in Hb utilization by this pathogen was also identified. An isogenic mutant defective in this Moraxella Hb-utilization protein (MhuA), 7169 : : mhuA, showed a significant lag during growth in the presence of Hb as the sole iron source. This protein appears to be expressed constitutively, regardless of growth conditions, and a mAb directed to MhuA demonstrated that this protein contains highly conserved, surface-exposed epitopes. Data demonstrating that expression of MhuA may be highly specific to isolates of M. catarrhalis are also presented, suggesting a potential role as a diagnostic marker. To our knowledge, this is the first report demonstrating that M. catarrhalis expresses an Hb-binding protein and that this bacterium can utilize Hb as a sole iron source for growth.

Acute otitis media caused by Streptococcus pyogenes in children

BACKGROUND

Streptococcus pyogenes, or group A beta -hemolytic Streptococcus (GAS), is an important causative agent of bacterial pharyngotonsillititis and skin, soft-tissue, and invasive infections. Although it is also an important pathogen in acute otitis media (AOM), its exact role has not been determined.

METHODS

Patients aged 0-18 years with AOM, from whom a specimen of middle-ear fluid was obtained and cultured during 1999-2003, were enrolled. Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and GAS were considered pathogens. Information collected included demographic characteristics, clinical history, and signs and symptoms.

RESULTS

GAS otitis was observed in 350 (3.1%) of 11,311 episodes (of which 117 were also culture-positive for other pathogens). The other 10,961 episodes involved H. influenzae only (n = 2507), S. pneumoniae only (n = 2131), dual infection with H. influenzae and S. pneumoniae (n = 1290), M. catarrhalis only (n = 129), and other combinations of pathogens (n = 271). Increased age and Jewish ethnicity were independent, significant, positive risk factors for GAS AOM, and fall season was a negative risk factor. Episodes of GAS infection were less frequently bilateral, febrile, and accompanied by other systemic findings than were other episodes of other types of infection. Most patients with GAS AOM presented with acute drainage from the ears. A lower proportion of cases of AOM were due to GAS in children with recurrent AOM and in patients recently treated with antibiotics, compared with patients with AOM who did not have these factors. The risk for mastoiditis was highest among patients with GAS AOM, compared with patients infected with other pathogens: 11.6 episodes per 1000 episodes of GAS AOM, compared with 2.2, 0.3, and 0 episodes of mastoiditis per 1000 episodes of AOM due to S. pneumoniae, H. influenzae, and M. catarrhalis, respectively.

CONCLUSION

Compared with AOM caused by pathogens other than GAS, GAS AOM is characterized by older age and higher local aggressiveness manifested by lower rates of fever and respiratory symptoms and higher rates of tympanic perforation and mastoiditis.

A novel plasmid (pEMCJH03) isolated from moraxella catarrhalis possibly useful as a cloning and expression vector within this species

A preliminary screening study of six Moraxella catarrhalis isolates from primary school children in the Netherlands identified a small 3.5 kb plasmid (pEMCJH03), containing four open reading frames, which encoded three mobilizing and one replicase protein. Insertion of a kanamycin containing transposon (yielding pEMCJH04) allowed selection and isolation of the plasmid in Escherichia coli. Natural transformation of pEMCJH04 into M. catarrhalis was successful for 25% (3/12) of non-isogenic isolates, with no link between (lack of) transformability and genetic lineage or (lack of) transformability and complement phenotype, though the transformation efficiency was found to be rather low at approximately 615CFU/microg (range=60-1040CFU/microg ). This is only the second publication detailing a plasmid isolated from this important respiratory pathogen, and the ability to clone and express foreign proteins in M. catarrhalis using pEMCJH04 could help in the development of a vaccine expression vector, as well as providing a useful tool for studying promoter activity and in complementation studies of gene knockout mutants.

Induction of CD69 expression and Th1 cytokines release from human peripheral blood lymphocytes after in vitro stimulation with Alloiococcus otitidis and three middle ear pathogens

Alloiococcus otitidis is a recently discovered pathogen of otitis media. However, only a limited number of studies are available about the pathogenic and immunological role of A. otitidis. The aim of this study was to investigate the activation and the cytokine production of human peripheral blood lymphocytes at the early immune response after stimulation with A. otitidis. After stimulation of whole human peripheral blood lymphocytes for 18 h with whole killed A. otitidis or the three major middle ear pathogens (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis), the expression of CD69 and the production of cytokines were analyzed. The expression of CD69 on T cells and B cells was dose-dependently enhanced after stimulation with A. otitidis. The release of interleukin (IL)-12 was induced after stimulation with A. otitidis, whereas the release of IL-4 was not induced after stimulation with A. otitidis. In addition, the release of interferon (IFN)-gamma was induced after stimulation with A. otitidis. Although the release of IFN-gamma started within 18 h after stimulation with A. otitidis, intracellular production of IFN-gamma was not observed in either CD4+ T cells or CD8+ T cells within 18 h upon stimulation. The patterns of CD69 expression and T helper-type 1 (Th1)-promoting cytokines production were similarly shown when human peripheral blood lymphocytes were stimulated with the other three major pathogens. Our results suggest that A. otitidis has sufficient immunogenic potential to modulate a host immune response, like the other three major middle ear pathogens, and also suggest that the immunogenicity of A. otitidis is very similar, at the early immune response, to that of the three major middle ear pathogens.

Moraxella catarrhalis coaggregates with Streptococcus pyogenes and modulates interactions of S. pyogenes with human epithelial cells

The pathogens Streptococcus pyogenes and Moraxella catarrhalis colonize overlapping regions of the human nasopharynx. We have found that M. catarrhalis can dramatically increase S. pyogenes adherence to human epithelial cells and that species-specific coaggregation of these bacteria correlates with this enhanced adherence.

The Emerging PathogenMoraxella catarrhalisInteracts with Complement Inhibitor C4b Binding Protein through Ubiquitous Surface Proteins A1 and A2

Moraxella catarrhalis ubiquitous surface protein A2 (UspA2) mediates resistance to the bactericidal activity of normal human serum. In this study, an interaction between the complement fluid phase regulator of the classical pathway, C4b binding protein (C4BP), and M. catarrhalis mutants lacking UspA1 and/or UspA2 was analyzed by flow cytometry and a RIA. Two clinical isolates of M. catarrhalis expressed UspA2 at a higher density than UspA1. The UspA1 mutants showed a decreased C4BP binding (37.6% reduction), whereas the UspA2-deficient Moraxella mutants displayed a strongly reduced (94.6%) C4BP binding compared with the wild type. In addition, experiments with recombinantly expressed UspA1(50-770) and UspA2(30-539) showed that C4BP (range, 1-1000 nM) bound to the two proteins in a dose-dependent manner. The equilibrium constants (K(D)) for the UspA1(50-770) and UspA2(30-539) interactions with a single subunit of C4BP were 13 microM and 1.1 microM, respectively. The main isoform of C4BP contains seven identical alpha-chains and one beta-chain linked together with disulfide bridges, and the alpha-chains contain eight complement control protein (CCP) modules. The UspA1 and A2 bound to the alpha-chain of C4BP, and experiments with C4BP lacking CCP2, CCP5, or CCP7 showed that these three CCPs were important for the Usp binding. Importantly, C4BP bound to the surface of M. catarrhalis retained its cofactor activity as determined by analysis of C4b degradation. Taken together, M. catarrhalis interferes with the classical complement activation pathway by binding C4BP to UspA1 and UspA2.

Morphostructural damage and the inhibition of bacterial adhesiveness of Staphylococcus aureus and Moraxella catarrhalis induced by moxifloxacin

The aim of this study was to investigate the ability of moxifloxacin to interfere with the mechanism of bacterial adhesion and disrupt the morphological and structural integrity of bacteria. Three Staphylococcus aureus and three Moraxella catarrhalis strains were grown in the presence of 1/2-1/128 minimum inhibitory concentration (MIC) serial dilutions and incubated with human epithelial cells. A significant decrease in adhesion was observed from 1/2 MIC to 1/64 MIC for S. aureus, and from 1/2 MIC to 1/16 MIC for M. catarrhalis. The use of atomic force microscopy, a new technique capable of revealing surface structures in three-dimensional detail and at very high resolution, showed the rapid onset and time course of the sequence of disruptive morphostructural events following the incubation of both S. aureus and M. catarrhalis with sub-MICs of moxifloxacin. Our findings suggest that less than conventional MIC moxifloxacin concentrations may be effective in reducing bacterial adhesiveness and structural integrity on which the maintenance of bacterial activity depends.

Eustachian tube gland tissue changes are related to bacterial species in acute otitis media

BACKGROUND AND OBJECTIVE

Prior investigations have shown that the number of mucus producing goblet cells in the middle ear and Eustachian tube (ET) mucosa is highly increased during and up to at least six months after experimental acute otitis media (AOM) caused by Streptococcus pneumoniae (SP). Further, the volume of the mucus producing paratubal gland components is increased up to 3 months after the acute infection. These changes may in conjunction with a deteriorated ET function predispose a subsequent development of secretory otitis media. The present investigation compares changes in goblet cell density and gland structures of the ET during and after AOM caused by various bacteria typically encountered in this disease, with emphasis on potential differences due to bacterial species.

METHODS

Rat models of AOM caused by SP, non-typeable or type b Haemophilus influenzae (NTHI/HIB) or Moraxella catarrhalis (MC) were studied longitudinally up to 6 months after bacterial challenge. The ET was dissected and decalcified, paraffin embedded and serially sectioned, followed by PAS/alcian blue staining. The goblet cell density and the paratubal gland composition and volume were determined morphometrically in every 20th section, using a light microscope.

RESULTS

Regardless of bacterial species, the ET goblet cell density was increased from day 8 and peaked day 16, followed by some degree of normalisation, although not reaching normal numbers within the 6 month period, except for MC. The highest increase was seen in AOM caused by the non-typeable Haemophilus strain, followed by HIB, SP and MC. Except with MC, pathological intra-epithelial glands formed and goblet cells were found in mucosal areas normally devoid of these. In all species but MC, the volume of the paratubal glands progressed to peak 16 days post-inoculation, followed by a gradual normalisation. The volume was still increased 3 months after the acute infection, but completely normalised after 6 months. The increase was primarily due to hypertrophy of the mucous gland components and highest in AOM caused by the Haemophilus species, followed by SP.

CONCLUSION

The Eustachian tube goblet cell density is increased during and up to at least six months after AOM regardless of bacterial species, except when employing MC, by which the density was increased for a few weeks only. Except in AOM caused by MC, the volume of the ET glands increases during and up to at least 3 months after infection, primarily due to hypertrophy of the mucous gland components. The non-typeable Haemophilus strain induced the highest increase of both goblet cell density and mucous gland volume. The increased secretory capacity of the ET following AOM may by excessive mucus secretion contribute to the deteriorated ET function found after AOM and thus predispose, sustain or aggravate middle ear disease.

A mouse model for acute otitis media

To induce acute otitis media in the mouse and to describe the clinical and bacteriological course of the infection, middle ears of BALB/c, Swiss-Webster and C57BL/6 mice were inoculated with Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Systemic and local changes were monitored by clinical observations, otomicroscopy, and analysis of bacterial samples from blood and middle ears. Agglutination of mouse erythrocytes by M. catarrhalis was also tested. Depending on bacterial strain, bacterial dose, and mouse strain three responses were identified: acute otitis media, otitis media with serous effusion, or no reaction. BALB/c mice were the most susceptible animals. On day 3, 76% of the BALB/c mice had developed middle ear infection, 50% had a positive middle ear culture, 56% were bacteremic, and 10% had succumbed to a disseminated infection. The local infections lasted approximately a week. Animals which survived recovered without permanent deterioration or otomicroscopically discernible changes. In no case did M. catarrhalis induce a culture-positive middle ear infection, possibly due to an inability to agglutinate the mouse erythrocytes. The mouse model can become a useful tool in studies of pneumococcal and H. influenzae-induced otitis media, but the bacterial dose has to be carefully titrated and adjusted to the chosen mouse strain.

Prevention and management of antibacterial resistance for primary care patients with respiratory tract infections

This review examines the problem of increasing antibacterial resistance among the pathogens commonly associated with community-acquired respiratory tract infections, particularly Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increases in morbidity, mortality, and treatment cost associated with increased resistance to available antibiotics are challenging prescribers to find more effective therapeutic strategies. A MEDLINE search of the literature from 1966 to the present was performed to seek data relevant to the issue of resistance, especially the negative effects on patient outcomes and costs of therapy. Several observations and conclusions emerged. Data are lacking on local resistance patterns, broad-spectrum agents are overprescribed when narrower-spectrum choices would be more appropriate, a need exists for educational programs to encourage restricting drug use and changing prescribing habits, and there is a need for new antibiotic choices. The best antibiotic options are agents with a tailored spectrum of activity that are targeted at particular respiratory tract pathogens and have low potential to select for resistant organisms.

The Hag protein of Moraxella catarrhalis strain O35E is associated with adherence to human lung and middle ear cells

Previous studies have demonstrated that the Moraxella catarrhalis surface antigen UspA1 is an adhesin for Chang human conjunctival cells. The present report demonstrates that lack of UspA1 expression does not affect the adherence of strain O35E to A549 human lung cells or primary cultures of human middle ear epithelial (HMEE) cells. These results imply that another molecule mediates the adherence of M. catarrhalis to these two cell lines. To identify this adhesin, strain O35E was mutagenized with a transposon and 1,000 mutants were screened in a microcolony formation assay using A549 cells. Nine independent isolates exhibited an 8- to 19-fold reduction in adherence and contained a transposon in the same locus. Nucleotide sequence data and PCR analysis indicated that the transposons were inserted in different locations in the gene encoding the surface protein Hag. Quantitative assays using one representative transposon mutant, O35E.TN2, showed considerably decreased binding to A549 as well as HMEE cells. However, this mutant adhered at wild-type levels to Chang conjunctival cells. These findings suggest that the M. catarrhalis Hag protein is an adhesin for cell lines derived from human lung and middle ear tissues.

Identification of a Moraxella catarrhalis outer membrane protein exhibiting both adhesin and lipolytic activities

The UspA1 and Hag proteins have previously been shown to be involved in the ability of the Moraxella catarrhalis wild-type strain O35E to bind to human Chang and A549 cells, respectively. In an effort to identify novel adhesins, we generated a plasmid library of M. catarrhalis DNA fragments, which was introduced into a nonadherent Escherichia coli strain. Recombinant E. coli bacteria were subsequently enriched for clones that gained the ability to bind to Chang and A549 cells, yielding the plasmid pELFOS190. Transposon mutagenesis of this plasmid identified the potential adhesin gene mcaP (M. catarrhalis adherence protein). Sequence analysis revealed that McaP is related to autotransporter proteins and has substantial similarity with the GDSL family of lipolytic enzymes, particularly the Moraxella bovis phospholipase B. Expression of the mcaP gene product by E. coli increased adherence to Chang, A549, and 16HBE14o(-) polarized human bronchial cells 50- to 100-fold. Spectrophotometric assays with p-nitrophenol derivatives also demonstrated that McaP is an esterase. Furthermore, thin-layer chromatography revealed that McaP cleaves both phosphatidylcholine and lysophosphatidylcholine. McaP releases fatty acids and glycerophosphorylcholine upon cleavage of phosphatidylcholine, thus exhibiting phospholipase B activity. The construction and characterization of isogenic M. catarrhalis O35E mutants demonstrated that the lack of McaP expression abolishes esterase activity and considerably decreases adherence to several human cell lines.

The Alexander Project 1998-2000: susceptibility of pathogens isolated from community-acquired respiratory tract infection to commonly used antimicrobial agents

OBJECTIVES

The Alexander Project is a continuing surveillance study, begun in 1992, examining the susceptibility of pathogens involved in adult community-acquired respiratory tract infections (CARTI) to a range of antimicrobial agents.

MATERIALS AND METHODS

This study tested the susceptibility of isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected between 1998 and 2000 to 23 antimicrobials. Minimum inhibitory concentrations of agents were determined using the broth microdilution method and interpreted according to NCCLS and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

RESULTS

In total, 8882 isolates of S. pneumoniae, 8523 isolates of H. influenzae and 874 isolates of M. catarrhalis were collected during 1998-2000 from centres in 26 countries. The world-wide prevalence of penicillin resistance (penicillin MICs > or = 2 mg/l) in isolates of S. pneumoniae was 18.2% over the study period, and the prevalence of macrolide resistance (erythromycin MICs > or = 1 mg/l) in this pathogen was 24.6%. Over the study period, macrolide resistance exceeded penicillin resistance in 19 of the 26 countries included in the study. Of the non-fluoroquinolone agents, the only oral agents to which over 90% of S. pneumoniae isolates were susceptible at both NCCLS and PK/PD breakpoints were amoxicillin (95.1%) and co-amoxiclav (95.5-97.9%). The prevalence of fluoroquinolone-resistant S. pneumoniae (ofloxacin MICs > or = 8 mg/l) was 1.1%. Gemifloxacin was the most potent fluoroquinolone tested against S. pneumoniae (99.9% susceptible). In isolates of H. influenzae, beta-lactamase production was 16.9%, whereas the prevalence of beta-lactamase-negative, ampicillin-resistant strains was low (0.2%). beta-Lactamase production in M. catarrhalis world-wide remained high over the period studied (92.1%). Using PK/PD breakpoints, the most active non-fluoroquinolone agents against H. influenzae were ceftriaxone (100% susceptible), cefixime (99.8%) and co-amoxiclav (98.1-99.6%). Co-amoxiclav, cefdinir and cefixime (100%) were the most active beta-lactams against M. catarrhalis. Both H. influenzae and M. catarrhalis were highly susceptible to the fluoroquinolones.

CONCLUSIONS

These data demonstrate the continued evolution of and geographical variation in bacterial resistance and highlight the need for appropriate prescribing of antimicrobials in CARTI, using agents with adequate activity, based on local susceptibility profiles and PK/PD parameters.

[Invasive infection with Moraxella catarrhalis in two children with lymphatic leukemia and granulocytopenia]

In two young children with leukaemia, a girl and a boy aged 5 and 4 years, respectively, an invasive infection due to Moraxella catarrhalis was diagnosed at the time of granulocytopenia. They were treated with antibiotics. The first child developed pneumonia and recovered, the other developed severe septic shock and died. M. catarrhalis is a Gram-negative diplococcus, frequently colonising the upper respiratory tract in young children. In childhood this pathogen mainly causes infections such as otitis media and sinusitis, while in adults it primarily causes laryngitis, bronchitis and pneumonia. Immunocompromised patients or patients with chronic cardiopulmonary disease have an increased risk of severe infections.

Dynamics of nasopharyngeal colonization by potential respiratory pathogens

Studies have shown that colonization of the nasopharynx by potential respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis is established early in childhood, although rates vary greatly according to locality, sampling frequency, individual and social factors. Factors influencing colonization and elimination are not as yet fully understood, but adhesion to mucosal receptors and immune responses are implicated in addition to bacterial properties and colonization resistance dynamics. Colonization in children and adults has been intensively studied in various localities. Potential pathogens are more likely to colonize the nasopharynx of children prone to recurrent otitis media, where impaired local immunity and repeated exposure to respiratory pathogens are additional risk factors. Adults with chronic respiratory tract disease also have higher carriage rates. The factors contributing to increased risk of carriage of potential respiratory pathogens, as well as to clinical infection and antimicrobial resistance, are summarized in this review.