The beta-lactamases of Moraxella (Branhamella) catarrhalis isolated from Danish children

The characterization of Moraxella catarrhalis carried in the general population

Moraxella catarrhalis is a common cause of respiratory tract infection, particularly otitis media in children, whilst it is also associated with the onset of exacerbation in chronic obstructive pulmonary disease in adults. Despite the need for an efficacious vaccine against M. catarrhalis, no candidates have progressed to clinical trial. This study, therefore, aimed to characterize the diversity of M. catarrhalis isolated from the upper respiratory tract of healthy children and adults, to gain a better understanding of the epidemiology of M. catarrhalis and the distribution of genes associated with virulence factors, to aid vaccine efforts. Isolates were sequenced and the presence of target genes reported. Contrary to prevailing data, this study found that lipooligosaccharide (LOS) B serotypes are not exclusively associated with 16S type 1. In addition, a particularly low prevalence of LOS B and high prevalence of LOS C serotypes was observed. M. catarrhalis isolates showed low prevalence of antimicrobial resistance and a high gene prevalence for a number of the target genes investigated: ompB2 (also known as copB), ompCD, ompE, ompG1a, ompG1b, mid (also known as hag), mcaP, m35, tbpA, lbpA, tbpB, lbpB, msp22, msp75 and msp78, afeA, pilA, pilQ, pilT, mod, oppA, sbp2, mcmA and mclS.

First outbreak of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae in Germany

We report the first outbreak of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae in Germany. The presence of KPC was confirmed by polymerase chain reaction (PCR). The KPC-encoding plasmid was analysed by transconjugation experiments, DNA sequencing, Southern blotting and isoelectric focussing. Typing was performed by pulsed-field gel electrophoresis (PFGE). An ertapenem-resistant K. pneumoniae with low minimum inhibitory concentrations (MIC) to other cabapenems (tested by the Vitek system) was isolated from the index patient in January 2008. A KPC-2 was identified after K. pneumoniae with identical susceptibility patterns had been isolated from two more patients. Despite the introduction of infection control measures, transmission occurred in five additional patients and three of the patients died from infections. The source of the outbreak strain remained unclear; however, the Tn4401-containing bla (KPC-2) gene was similar to previously described isolates from Greece. Five months after the end of the outbreak, a KPC-K. pneumoniae was isolated from a patient who had been treated in Greece previously. Retrospectively, this patient was treated in November 2007 on the same unit as the index case. Typing revealed that all patients were colonised by the same strain. KPC-K. pneumoniae has been introduced to Germany possibly from Greece and transmission to other institutions is likely.

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.

Successful shortening from seven to four days of parenteral beta-lactam treatment for common childhood infections: a prospective and randomized study

OBJECTIVES

To explore whether 4-day parenteral beta-lactam therapy is as effective as 7-day therapy for children hospitalized for parenteral antimicrobials.

METHODS

A series of patients aged 3 months to 15 years who fulfilled strict criteria for bacterial pneumonia, other respiratory infections, sepsis-like infections, and other acute infections were prospectively randomized to receive parenteral penicillin or cefuroxime randomly for 4 or 7 days. Besides blood and throat cultures, the etiology was searched by serology for 23 different agents.

RESULTS

Of 154 children analyzed, a probable etiology was established in 96. Of those, a bacterial infection, with or without concomitant viral infection, was disclosed in 80% and 94% in the 4-day and 7-day treatment groups, respectively; pneumococcus being the commonest agent. There was one possible treatment failure in the 4-day group, but with a questionable relation to the short course. Three patients in the 4-day and two in the 7-day group underwent treatment changes, or were rehospitalized within 30 days. All children recovered entirely.

CONCLUSIONS

Shortening parenteral beta-lactam treatment to 4 days in infections for which most parenteral antimicrobials are instituted, is not only safe, but reduces costs, is ecologically sound, and minimizes the risks of nosocomial infections and other adverse effects of treatment.

Rapid discrimination between BRO beta-lactamases from clinical isolates of Moraxella catarrhalis using restriction endonuclease analysis

An important feature of Moraxella catarrhalis is the production of beta-lactamases, which causes resistance to the penicillins. Restriction enzyme analysis was able to distinguish between the bro-1 and bro-2 beta-lactamase-encoding genes from 89 clinical isolates of M. catarrhalis. This is a rapid, simple and cost effective method of characterizing these genes.

Antimicrobial resistance--pharmacological solutions

The interaction between microbial resistance and antibacterial agents occurs in a direct and an indirect fashion. Directly--through the development of resistance to the agent used, or to agents of the same class--as exemplified by the induction of beta-lactamase by both gram-positive and gram-negative bacteria. It also takes place through the development of resistance to compounds of different classes to the compound used, as exemplified by the loss of Streptococcus pneumoniae susceptibility to penicillin that is accompanied by a parallel loss of sensitivity to erythromycin and to tetracycline. As for the indirect way--microbial resistance may develop through selection of resistant organisms when the patient is treated with antibiotics, when the environment is contaminated with antibiotics (hospital) or when antibacterial agents are used in agriculture and animal husbandry.

Genesis of BRO beta-lactamase-producing Moraxella catarrhalis: evidence for transformation-mediated horizontal transfer

The dramatic rise in BRO-producing M. catarrhalis strains observed in the last decades is without precedence. The aim of this study was to elucidate the events that led to the emergence of BRO-1 and BRO-2 beta-lactamases. Previously, we showed bro1 and bro2 to be >99% identical. Data presented here suggested that bro2 was acquired by a fortuitous event and inserted between M. catarrhalis genes orf1 and orf3. Subsequently, bro1 evolved from bro2. Promoter-up mutations increased fitness of bro2, explaining its present predominance. The highly conserved nature of bro compared with orf1 and orf3 suggested that acquisition has occurred relatively recently. The random distribution of bro among M. catarrhalis fingerprint types indicated that bro has spread by horizontal transfer. Sequence analysis revealed that 80-200 bp is generally cotransferred with bro, serving as regions of homology that target bro to the same chromosomal locus. A region of 160 bases upstream of bro1 lacked polymorphism, indicating it was derived from the original strain that acquired bro2. We observed that bro was readily transferred by transformation between M. catarrhalis strains in vitro, suggesting a mechanism by which bro has disseminated. In conclusion, we have been able to reconstruct the steps that led to the emergence of BRO-producing M. catarrhalis.

Molecular characterization of the beta-lactamases from clinical isolates of Moraxella (Branhamella) catarrhalis obtained from 24 U.S. medical centers during 1994-1995 and 1997-1998

The beta-lactamases from 403 Moraxella (Branhamella) catarrhalis clinical isolates obtained during 1994-1995 and 1997-1998 U.S. multicenter surveillance studies were characterized by isoelectric focusing. The overall prevalences of the BRO-1 and BRO-2 enzymes among beta-lactamase-positive isolates were estimated to be 97.5 and 2.5%, respectively. The minimum inhibitory concentrations (MICs) of ampicillin for all BRO-2-producing isolates were </=1 microg/ml; however, numerous beta-lactamase-positive isolates for which the ampicillin MICs were </=1 microg/ml produced the BRO-1 enzyme (88. 1%).

Long-term trends in susceptibility of Moraxella catarrhalis: a population analysis

A retrospective, population analysis of antimicrobial susceptibility patterns was performed on Moraxella catarrhalis isolates recovered from a single medical centre to detect temporal trends and infer potential mechanisms of reduced susceptibility. The duration of this study, June 1984 to July 1994, encompassed the period during which the frequency of beta-lactamase production expanded from 30 to 96% in the population. MICs of penicillin G, cefamandole, ceftriaxone, amoxycillin/clavulanate, imipenem, clarithromycin, tetracycline, ciprofloxacin and trimethoprim/sulphamethoxazole for a representative sample of 375 isolates were determined. Analyses were conducted to test for variation in susceptibility among isolates, correlations of susceptibility levels among different antimicrobial agents, and temporal patterns in susceptibility. All antimicrobials except clarithromycin displayed significant differences among isolates within years, and mean MICs of all antimicrobial agents except tetracycline and clarithromycin varied significantly between years. Temporal trends to a reduction in susceptibility were detected to four of five beta-lactam antimicrobials (all except cefamandole). Significant correlations in MICs were uncovered among all pairs of four beta-lactam antimicrobials in both producers and non-producers of beta-lactamase. In contrast, cefamandole MICs were correlated only with ceftriaxone and penicillin, and these were limited to beta-lactam producing isolates; cefamandole and amoxycillin/clavulanate showed a correlation limited to non-producing isolates. For some antimicrobials, trends toward decreasing susceptibility may have been caused by an increased proportion of beta-lactamase producing isolates in the population, but the observation of significant decreases in susceptibility limited to beta-lactamase-producing isolates suggests that the underlying factors were different forms of beta-lactamase, beta-lactamase-dependent modifiers and/or additional factors.

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.