Classification of beta-lactamases from Branhamella catarrhalis in relation to penicillinases produced by other bacterial species

Production of BRO beta-lactamases and resistance to complement in European Moraxella catarrhalis isolates

Of the 419 Moraxella catarrhalis isolates collected during the 1997-1999 European SENTRY surveillance study, 385 (92%) were beta-lactamase positive. Twenty-two (5.7%) produced BRO-2 beta-lactamase. Twenty-one new mutations were found in the putative promoter region of the bro genes. Nineteen percent of all isolates tested were complement sensitive. Resistance to beta-lactams is not linked to the phylogenetic lineages associated with susceptibility to complement.

Moraxella catarrhalis: clinical significance, antimicrobial susceptibility and BRO beta-lactamases

Moraxella catarrhalis is an important pathogen of humans. It is a common cause of respiratory infections, particularly otitis media in children and lower respiratory tract infections in the elderly. Colonisation of the upper respiratory tract appears to be associated with infection in many cases, although this association is not well understood. Nosocomial transmission is being increasingly documented and the emergence of this organism as a cause of bacteremia is of concern. The widespread production of a beta-lactamase enzyme renders Moraxella catarrhalis resistant to the penicillins. Cephalosporins and beta-lactamase inhibitor combinations are effective for treatment of beta-lactamase producers, and the organism remains nearly universally susceptible to the macrolides, fluoroquinolones, tetracyclines and the combination of trimethoprim and sulfamethoxazole. Two major beta-lactamase forms, BRO-1 and BRO-2, have been described on the basis of their isoelectric focusing patterns. The BRO-1 enzyme is found in the majority of beta-lactamase-producing isolates and confers a higher level of resistance to strains than BRO-2. The BRO enzymes are membrane associated and their production appears to be mediated by chromosomal determinants which are transmissible by an unknown mechanism. The origin of these novel proteins is unknown.

[Moraxella catarrhalis: virulence and resistance mechanisms]

It is more than a century ago that Moraxella catarrhalis was discovered and described in some detail. However, it was not until the last decade that M. catarrhalis was recognized as a facultative pathogen, namely in otitis media (predominantly in children), sinusitis and nosocomial pneumonia in the group of elderly, debilitated patients. Liberation of endotoxin, histamine, and chemotactically active factors can be considered the major pathogenicity factors. The pathogen can protect itself, on the one hand by binding of the Clq subcomponent of the complement system followed by subsequent formation of a functionally inactive complex with Cl, and on the other hand by inactivation of the terminal (lytic) complement complexes by means of a specific protein on the surface of the outer cell wall. Routine diagnostic procedures require, above all, culture of the pathogen: up to now the detection of specific IgA-antibodies has not been routinely available. More than half of the clinical isolates are known to exhibit beta-lactamase production (BRO-enzymes). This is the reason why combinations of a penicillin compound with a beta-lactamase inhibitor, the group of the newer cephalosporins (including the orally active ones), doxycycline and the macrolides are therapeutically effective.

Increased beta-lactamase activity in Branhamella catarrhalis after exposure to amoxicillin and clavulanic acid

Branhamella catarrhalis, previously regarded as a harmless member of the normal nasopharyngeal flora, has periodically been implicated as the major pathogen in representative cases of a variety of infections such as sinusitis, pneumonia, septicemia and meningitis. In addition, beta-lactamase production of these microorganisms, first described in 1977, has been reported with increasing frequency, up to 80%. The first-choice drug for the therapy of the infections caused by beta-lactamase producing strains of B. catarrhalis is amoxicillin combined with clavulanic acid. The aim of our work was to determine the influence of amoxicillin and clavulanic acid on the biosynthesis of beta-lactamase of B. catarrhalis. Our results point out that the combination of amoxicillin and clavulanic acid produces only a slight increase in enzyme activity in 5003 and 462 strains. Clavulanic acid alone caused no increase in enzyme production. Ravasio strain showed no increase in enzyme formation after exposure to antibiotics.

Branhamella catarrhalis: phenotypic characteristics

PURPOSE

This review provides a comprehensive description and discussion of recognized phenotypic characteristics of Branhamella catarrhalis. An emphasis is placed on attributes of this organism that are relevant to its recovery and identification in the clinical microbiology laboratory. In addition, characteristics useful in determining strain identity for use in epidemiologic investigations are addressed. Finally, factors are discussed that may account for the infection-causing potential of B. catarrhalis or at least are of potential consequence to investigations of the pathogenesis of Branhamella disease.

CONCLUSIONS

B. catarrhalis is readily isolated from human clinical specimens and can be easily identified using simple, rapid laboratory techniques. Restriction endonuclease analysis of chromosomal deoxyribonucleic acid has proven to be a useful tool in epidemiologic studies. Beta-lactamase isoelectric focusing is of limited value because of the small number of distinct patterns. The lipopolysaccharide and outer membrane proteins of B. catarrhalis have been characterized and found to be relatively non-varying among different strains. Circumstantial evidence exists in support of the hypothesis that the B. catarrhalis beta-lactamase is a virulence determinant.

Amoxycillin and clavulanic acid in the treatment of urinary tract infections in children

The efficacy of amoxycillin-clavulanic acid combination in the treatment of urinary tract infections resistant, in vitro, to amoxycillin was studied in 42 children. Of the 24 children with urinary tract infection for the first time, combination therapy, dosing twice daily for 5 days (40 mg/kg.day), cleared the infection in 23 (96%) cases. Relapse occurred in four (17%) cases within 30 days. Of the 18 children who presented with recurrent urinary tract infections therapy, as above, cleared the infection in 16 (89%) cases. In these cases, long-term therapy was performed at a dosage of 20 mg/kg once daily. Tolerance was good; gastro-intestinal disorders in five (12%) cases which regressed by dosing at 8 h rather than 12 h intervals. In conclusion, amoxycillin-clavulanic acid can be considered a first choice treatment of urinary tract infections in children.

Detection of beta-lactamase activity among clinical isolates of Branhamella catarrhalis with six different beta-lactamase assays

A total of 74 different clinical isolates of Branhamella catarrhalis were examined for their ability to produce beta-lactamase by six different beta-lactamase assays. These included a conventional tube and disk test, in which the chromogenic cephalosporin nitrocefin was used as a substrate; a disk procedure, in which pyridinium-2-azo-p-dimethylanaline cephalosporin was used as a substrate; broth and disk acidometric methods; and a conventional tube iodometric assay. A total of 58 of the study isolates produced beta-lactamase. In all cases, positive results were obtained with the nitrocefin tube and disk assays after 1 min. With the pyridinium-2-azo-p-dimethylanaline cephalosporin disk test, 57 of the 58 beta-lactamase-producing strains yielded a positive reaction in 1 min; the remaining strain was positive after 10 min. None of the beta-lactamase-producing strains produced positive reactions by either the broth or disk acidometric methods after 1 min. With the broth test, 10 min was required for positive test results for 42 strains; 30 min was necessary for 16 strains. By the disk acidometric procedure, all 58 strains were positive after 10 min. Of 58 beta-lactamase-producing strains, 30 were positive by the iodometric assay after 1 min, 13 strains required 10 min, and 4 strains were detected as being beta-lactamase positive only after 30 min. One beta-lactamase-producing strain remained negative by the iodometric method. Among the 16 strains of B. catarrhalis that lacked beta-lactamase that were examined in this study, no false-positive results were obtained by any of the six assays.

Effect of inoculum size on results of macrotube broth dilution susceptibility tests with Branhamella catarrhalis

The effect of inoculum size on the results of macrotube broth dilution MICs was assessed with 15 strains of Branhamella catarrhalis versus 22 antimicrobial agents. The study isolates included five beta-lactamase-negative strains, five strains that produced beta-lactamase and for which ampicillin MICs were high, and five beta-lactamase-producing strains for which ampicillin MICs were low. An inoculum effect was observed only with strains in the last group when tested versus the following antimicrobial agents: penicillin G, ampicillin, cephalothin, cefamandole, cefuroxime, and cefaclor.