Beta-lactamase production in the upper respiratory tract flora

Characterisation of a capsular polysaccharide from Moraxella nonliquefaciens CCUG 348T

Moraxella nonliquefaciens is a commensal of the human upper respiratory tract (URT) but on rare occasions is recovered in cases of ocular, septic and pulmonary infections. Hence there is interest in the pathogenic determinants of M. nonliquefaciens, of which outer membrane (OM) structures such as fimbriae and two capsular polysaccharide (CPS) structures, →3)-β-D-GalpNAc-(1→5)-β-Kdop-(2→ and →8)-α-NeuAc-(2→, have been reported in the literature. To further characterise its surface virulence factors, we isolated a novel CPS from M. nonliquefaciens type strain CCUG 348T. This structure was elucidated using NMR data obtained from CPS samples that were subjected to various degrees of mild acid hydrolysis. Together with GLC-MS data, the structure was resolved as a linear polymer composed of two GalfNAc residues consecutively added to Kdo, →3)-β-D-GalfNAc-(1→3)-α-D-GalfNAc-(1→5)-α-(8-OAc)Kdop-(2→. Supporting evidence for this material being CPS was drawn from the proposed CPS biosynthetic locus which encoded a potential GalfNAc transferase, a UDP-GalpNAc mutase for UDP-GalfNAc production and a putative CPS polymerase with predicted GalfNAc and Kdo transferase domains. This study describes a unique CPS composition reported in Moraxella spp. and offers genetic insights into the synthesis and expression of GalfNAc residues, which are rare in bacterial OM glycans.

Association of β-Lactam-Sensitive Haemophilus influenzae Type B with Adenoid Biofilm Formation in Patients with Adenoidectomy Surgery

BACKGROUND

Chronic adenoid infection by β-lactam-resistant Haemophilus influenzae type b (Hib) and biofilm formation contribute to adenoid hyperplasia. Middle ear disease consequently remains a critical issue in the pediatric population. The aim of this study was to investigate the correlation of Hib biofilm formation with middle ear effusion with adenoid hyperplasia (MEE-AH) and with pediatric obstructive sleep apnea (OSA).

METHODS

A total of 384 patients with adenoidectomy from January 2008 to December 2012 were recruited in this investigation. Thirty-two patients (14 female and 18 male; age 4-13 years) who obtained routine adenoidectomy surgery had Hib-positive cultures were enrolled in a retrospective manner. By using polysomnography, 18 patients were diagnosed as having MEE-AH with chronic adenotonsillitis, and 14 patients were diagnosed as having pediatric OSA. The results of the Hib biofilm, antibiotic resistance profiles, and scanning electron microscopy observation, which correlated with the clinical diagnosis, were analyzed by the chi-square test and Fisher exact test.

RESULTS

Biofilm formation by Hib was significantly present in the patients with MEE-AH rather than patients with OSA. β-lactam-sensitive Hib were resistant to augmentin because of the adenoid biofilm formation. However, this finding was uncommon in the pediatric OSA group.

CONCLUSIONS

Properly treating β-lactam-sensitive Hib infection may be an important issue in reducing MEE-AH and adenoid vegetation in the pediatric population. Further research is warranted to elucidate the association of Hib-related biofilm formation with treatment failure and the need to consider earlier surgical intervention.

Down-regulation of porin M35 in Moraxella catarrhalis by aminopenicillins and environmental factors and its potential contribution to the mechanism of resistance to aminopenicillins

Objectives

The outer membrane protein M35 of Moraxella catarrhalis is an antigenically conserved porin. Knocking out M35 significantly increases the MICs of aminopenicillins. The aim of this study was to determine the biological mechanism of this potentially new antimicrobial resistance mechanism of M. catarrhalis and the behaviour of M35 in general stress situations.

Methods

PCR using m35-specific primers was used to detect the m35 gene in clinical isolates. The m35 mRNA expression of strains 300, O35E and 415 after exposure to amoxicillin and different stress conditions was measured by real-time PCR and normalized in relation to their 16S rRNA expression. The expression of M35 protein was analysed by SDS-PAGE and western blotting.

Results

Screening of 52 middle ear isolates resulted in positive PCR products for all tested strains. The analysis of m35 mRNA expression after amoxicillin treatment showed 24%–85% down-regulation compared with the respective amoxicillin-free controls in all three strains tested. Also, analysis of protein concentrations revealed lower M35 expression after growth with amoxicillin. Investigation of M35 during general stress responses showed down-regulation of the porin with growth at 26°C and 42°C, under hyperosmolar stress and under iron restriction.

Conclusions

The reduced expression of M35 after aminopenicillin exposure indicates a novel resistance mechanism against aminopenicillins in M. catarrhalis, which may be relevant in vivo. The differences in expression after different stress treatments demonstrate that M35 is involved in general stress responses.

Correlation between susceptibility and BRO type enzyme of Moraxella catarrhalis strains

Clinical isolates of Moraxella catarrhalis (76 isolates) were screened for beta-lactamase production and antibiotic susceptibility. beta-Lactamases (detected in 90.8% of isolates) were typed using isoelectric focusing to BRO-1 (87%) and BRO-2 (13%). Minor variations in electrofocusing patterns between the two types were seen. Isolates expressing BRO type enzymes showed solid resistance to penicillin, ampicillin and cephalothin, in particular BRO-1 producers. BRO-1 isolates were less susceptible to cephems and to beta-lactamase inhibitors than BRO-2 isolates. Isolates harbouring BRO-1 enzymes have more enzymatic activity than those expressed by BRO-2 isolates. Apart from resistance to tetracycline (14.5%), all isolates were consistently susceptible to erythromycin, chloramphenicol, ciprofloxacin and gentamicin. The conjugal transfer of BRO beta-lactamase gene(s) between M. catarrhalis isolates occurred with a frequency of 10(-5) to 10(-7)/donor cell. The data emphasize the importance of M. catarrhalis as an etiological agent spreading beta-lactamases that may inhibit some beta-lactams and lead to failure in treatment of mixed infections.

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.

Antibiotic resistance in oral/respiratory bacteria

In the last 20 years, changes in world technology have occurred which have allowed for the rapid transport of people, food, and goods. Unfortunately, antibiotic residues and antibiotic-resistant bacteria have been transported as well. Over the past 20 years, the rise in antibiotic-resistant gene carriage in virtually every species of bacteria, not just oral/respiratory bacteria, has been documented. In this review, the main mechanisms of resistance to the important antibiotics used for treatment of disease caused by oral/respiratory bacteria--including beta-lactams, tetracycline, and metronidazole--are discussed in detail. Mechanisms of resistance for macrolides, lincosamides, streptogramins, trimethoprim, sulfonamides, aminoglycosides, and chloramphenicol are also discussed, along with the possible role that mercury resistance may play in the bacterial ecology.

Mucosal Immunity and Bacteriology of the Eustachian Tube

The pathogenesis of otitis media is a multifaceted process that is not completely understood. Eustachian tube dysfunction plays a central but uncertain role, as do viral and bacterial microorganisms. Of the latter, the three most important are Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. This article reviews the various mechanisms of infection and the immune system's response to them.

Prevalence of potential respiratory disease bacteria in children in Ethiopia. Antimicrobial susceptibility of the pathogens and use of antibiotics among the children

Acute respiratory infections are primary causes of morbidity and mortality in children in developing countries. This project was designed to investigate antimicrobial susceptibility of respiratory tract pathogens isolated from children in rural and city areas, and to contribute to the rational choice of antibiotics for respiratory tract infections in children in Ethiopia. Nasopharynx and throat cultures were taken from all children under five years of age in three study areas representing different levels of contact with health care and accessibility to modern drugs, such as antibiotics. In all, 1126 children were cultured. Haemophilus influenzae and Streptococcus pneumoniae were both found in 85-90% of the children, and beta-haemolytic streptococci group A in 12%. The level of antimicrobial resistance was low. None of the 954 strains of H. influenzae were beta-lactamase producers. Pneumococci were susceptible to penicillin. The use of antibiotics was also low; 11 of 1126 children had antibiotics on the day of culture or the day before. The choice of antibiotics was not limited by resistance, and emphasis could be put on low cost, minimizing adverse drug reactions and ecological impact.

Characterization of cell-bound papain-soluble beta-lactamases in BRO-1 and BRO-2 producing strains of Moraxella (Branhamella) catarrhalis and Moraxella nonliquefaciens

In Moraxella (Branhamella) catarrhalis and Moraxella nonliquefaciens strains isolated from clinical specimens in the south of Sweden two variants of beta-lactamase were distinguished by isoelectric focusing (IEF). The BRO-1 (Ravasio type) enzyme was the most common in Branhamella catarrhalis, constituting about 90% of the beta-lactamase found in this species, while the BRO-2 enzyme (1908 type) was as common as BRO-1 in Moraxella nonliquefaciens. The determinants mediating the production of BRO-1 and BRO-2 were both transferable by conjugation. Cell-bound beta-lactamase from reference strains producing BRO-1 and BRO-2 could be solubilized by papain digestion. The isoelectric point of the solubilized enzymes differed distinctly between BRO-1 (pI 6.5) and BRO-2 (pI 6.9). The molecular species of BRO-1 and BRO-2 released by papain digestion were purified by affinity chromatography with phenylboronic acid agarose gel. They had identical molecular weights of approximately 28,000. Their kinetic constants were indistinguishable for a number of substrates and beta-lactamase inhibitors.

Production of betalactamase by respiratory tract bacteria in children: relationship to antibiotic use

Sales of antibiotics have increased in Sweden during the past decade. This has been paralleled by an increase in the frequency of beta-lactamase-producing respiratory tract bacteria. To investigate the effects of regional differences in use of antibiotics on beta-lactamase production in respiratory tract bacteria, we collected nasopharyngeal specimens and information about antibiotic use from 1133 children attending day-care centres in four rural municipalities with low use, and one urban municipality with high use of antibiotics, use being assessed from pharmacy sales. The frequency of beta-lactamase production among isolates of Branhamella catarrhalis and Moraxella nonliquefaciens was significantly higher in the urban municipality. This appeared to be a long-term ecological effect of differences in the level of use of antibiotics between the urban and rural populations, rather than an effect of recent antibiotic treatment of individual patients.

Direct and indirect pathogenicity of beta-lactamase-producing bacteria in respiratory tract infection in children. Role of cephalosporins resistant to enzymatic hydrolysis

A recent increase in the incidence of beta-lactamase-producing aerobic and anaerobic bacteria in upper respiratory tract infection has been associated with an increase in the failure rate of penicillin treatment of these infections. Experimental evidence for this correlation has been reported by many investigators, who have described the sheltering of susceptible pathogens by beta-lactamase-producing organisms as 'indirect pathogenicity'. The organisms implicated in mixed infections that cooperate are Staphylococcus aureus, Haemophilus influenzae, Branhamella (Moraxella) catarrhalis and Bacteroides spp., which are pathogenic and also normal oropharyngeal inhabitants. Since these bacteria exhibit both direct and indirect pathogenicity, effective treatment requires administration of antimicrobial therapy active against all microorganisms present in mixed infection. Oral third generation cephalosporins, which are resistant to enzymatic hydrolysis, seem to be suitable initial therapy.

Respiratory tract carrier rates of Moraxella (Branhamella) catarrhalis in adults and children and interpretation of the isolation of M. catarrhalis from sputum

Nonselective media and previously described selective media were used to study the occurrence of Moraxella (Branhamella) catarrhalis in sputum samples of good and poor quality and in samples taken from different sites of the upper respiratory tracts of healthy subjects. It was found that in healthy adults the carrier rate was 5.4%, as opposed to 50.8% in children and 26.5% in people older than 60 years. M. catarrhalis was recovered significantly more often from sputum samples of good quality (5%) than from poor quality samples (0.5%), and when present, it was found mostly in the presence of high inocula. From these data gathered from healthy and diseased subjects, it is concluded that the presence of M. catarrhalis in the sputum of adults is rarely due to oronasopharyngeal contamination of the sputum. Similar findings reported by others are discussed, and the origins of the currently held concept that M. catarrhalis is a common commensal organism of the human upper respiratory tract are traced.

Circulation in Italy of beta-lactamase-producing strains within the major groups of bacterial pathogens

A multicenter study was undertaken in Italy to assess the circulation of beta-lactamase-producing organisms and their current incidence within the major groups of bacterial pathogens. Almost four thousand strains, all freshly isolated from clinical material, were examined at four centers serving different areas of Italy. Despite some significant center-to-center differences, this survey documented the occurrence of a large overall circulation of beta-lactamase-producing organisms among clinical bacterial isolates. In particular, ampicillin resistance was recorded in one third to one half of the isolates of some Enterobacteriaceae, including Escherichia coli, Proteus, and Citrobacter species, and 80-90% of these resistant strains proved to be beta-lactamase producers. Both ampicillin resistance and beta-lactamase production were almost the rule in other Enterobacteriaceae, including Klebsiella, Enterobacter, and Serratia species. beta-lactamase was also produced by about 80% of glucose-non-fermenting gram-negative bacteria and Aeromonas hydrophila strains, by all of the isolates of Branhamella catarrhalis manifesting ampicillin resistance (i.e. more than half the total number of isolates), and by about two thirds of the ampicillin-resistant Haemophilus strains (which accounted for 20-25% of all Haemophilus isolates examined). In contrast, no beta-lactamase producers were observed among Neisseria gonorrhoeae isolates.

Emergence and persistence of beta-lactamase-producing bacteria in the upper respiratory tract in children treated with beta-lactam antibiotics

PURPOSE

To assess the ecologic impact, in terms of selection of beta-lactamase-producing respiratory tract bacteria, of a single course of peroral beta-lactam antibiotics.

PATIENTS AND METHODS

One-hundred fifty consecutive children with clinical signs of bacterial respiratory tract infection were randomly assigned to a seven-day course of treatment with either penicillin V, amoxicillin, or cefaclor. Bacteriologic specimens were collected before treatment, at its termination, and at follow-up four weeks later.

RESULTS

All three drugs investigated caused a similar increase in beta-lactamase-producing bacteria, both in absolute and relative terms, an increase that persisted over a period of at least one month after completion of treatment.

CONCLUSION

Penicillin V, amoxicillin, and cefaclor all act as selective agents for beta-lactamase-producing bacteria in the upper respiratory tract. Treatment with a peroral beta-lactam antibiotic puts patients at risk of becoming persistent carriers of beta-lactamase-producing bacteria.

Colonization by Haemophilus influenzae and group A streptococci in recurrent acute tonsillitis and in tonsillar hypertrophy

One hundred patients subjected to tonsillectomy because of recurrent acute tonsillitis or tonsillar hypertrophy were evaluated bacteriologically both with ordinary throat culturing and cultures from tonsillar cores. In 26% of the patients H. influenzae was isolated and in 20% beta-haemolytic group A streptococci. Growth of B. catarrhalis was obtained in 10% and group C-, group G streptococci or pneumococci in less than 5% each. None of the group A streptococcal strains proved tolerant to penicillin. A much higher isolation rate of H. influenzae was found in cultures obtained from tonsillar core tissue (23%) than from ordinary throat cultures (2%). This was also the fact, though to a lower extent, regarding group A streptococci. H. influenzae and group A streptococci were isolated as often in patients with tonsillar hypertrophy as in patients suffering from recurrent acute tonsillitis, suggesting a role of these bacteria in both conditions.

BRO beta-lactamases of Branhamella catarrhalis and Moraxella subgenus Moraxella, including evidence for chromosomal beta-lactamase transfer by conjugation in B. catarrhalis, M. nonliquefaciens, and M. lacunata

Two closely related beta-lactamases, BRO-1 and BRO-2 (formerly called Ravasio and 1908), are found in Moraxella (Branhamella) catarrhalis. We screened strains of B. catarrhalis recovered in the United States since 1952 and identified the first beta-lactamase-positive isolate in August 1976. The prevalence of the enzymes among 394 clinical isolates from one Texas hospital has averaged 75% since testing began in 1983. Screening of isolates of Moraxella subgenus Moraxella revealed the BRO enzymes in two other human respiratory tract species, M. lacunata and M. nonliquefaciens, beginning in 1978. A different beta-lactamase with a pI of 6.4 predominated in other species of subgenus Moraxella. BRO-2 had a different isoelectric focusing pattern and was produced in lesser amounts than BRO-1, but the two enzymes were indistinguishable by substrate or inhibitor profile. BRO enzymes from B. catarrhalis, M. nonliquefaciens, and M. lacunata could be transferred by conjugation and, for B. catarrhalis, also by transformation to B. catarrhalis. Plasmid bands were demonstrated in 90% of M. nonliquefaciens and in one previously reported strain of B. catarrhalis, but no change in plasmid profiles was seen in beta-lactamase-positive recombinants, supporting previous studies that suggested the beta-lactamase genes are chromosomal.

Beta-lactamase production in the upper respiratory tract flora in relation to antibiotic consumption: a study in children attending day nurseries

The occurrence of beta-lactamase production in Haemophilus influenzae, Branhamella catarrhalis and Moraxella nonliquefaciens was compared in 191 healthy children attending day nurseries in 2 municipalities differing with regard to the prescription rate of beta-lactam antibiotics. A significantly higher frequency of beta-lactamase production was recorded in M. nonliquefaciens isolated in the municipality with the higher prescription rate. A corresponding difference was not recorded for H. influenzae or B. catarrhalis. Approximately 75% of the nasopharyngeal pathogens H. influenzae, B. catarrhalis and Streptococcus pneumoniae, as well as the commensal M. nonliquefaciens, were eliminated and often replaced by other strains of either species over a period of one month. Although none of the children were on antibiotics a substantial proportion of the acquired strains produced beta-lactamase. This suggested that the carrier rate of beta-lactamase producing strains of the respiratory tract is not only related to the effect of recent antibiotic treatment but also to the prevalence of such strains in the population.