Beta-lactam effects on mixed cultures of common respiratory isolates as an approach to treatment effects on nasopharyngeal bacterial population dynamics

Nasopharyngeal microbiota in hospitalized children with Bordetella pertussis and Rhinovirus infection

Despite great advances in describing Bordetella pertussis infection, the role of the host microbiota in pertussis pathogenesis remains unexplored. Indeed, the microbiota plays important role in defending against bacterial and viral respiratory infections. We investigated the nasopharyngeal microbiota in infants infected by B. pertussis (Bp), Rhinovirus (Rv) and simultaneously by both infectious agents (Bp + Rv). We demonstrated a specific nasopharyngeal microbiome profiles for Bp group, compared to Rv and Bp + Rv groups, and a reduction of microbial richness during coinfection compared to the single infections. The comparison amongst the three groups showed the increase of Alcaligenaceae and Achromobacter in Bp and Moraxellaceae and Moraxella in Rv group. Furthermore, correlation analysis between patients’ features and nasopharyngeal microbiota profile highlighted a link between delivery and feeding modality, antibiotic administration and B. pertussis infection. A model classification demonstrated a microbiota fingerprinting specific of Bp and Rv infections. In conclusion, external factors since the first moments of life contribute to the alteration of nasopharyngeal microbiota, indeed increasing the susceptibility of the host to the pathogens' infections. When the infection is triggered, the presence of infectious agents modifies the microbiota favoring the overgrowth of commensal bacteria that turn in pathobionts, hence contributing to the disease severity.

Human Nasal Microbiome as Characterized by Metagenomics Differs Markedly Between Rural and Industrial Communities in Egypt

Microbial communities residing in the nose play important roles in human health and disease. We report marked differences in nasal microbiota between a rural community and an industrial setting located near a major urban city. Nasal samples were collected from 19 healthy male subjects: 9 samples from persons living in a rural village, and 10 samples from ceramic factory workers in a major industrial Egyptian city. The nasal microbiota in the rural sample had higher and distinct diversity compared with industrial samples from workers exposed to pollution daily. Taxonomic analysis of the sequences revealed five major phyla; among these phyla were Actinobacteria, Proteobacteria, Bacteroidetes, and Fusobacteria, revealing significant abundance variation by geographical location. For example, the rural group had a significant increase in representation of Actinobacteria and Bacteroidetes (p = 0.004, p = 0.01, respectively) compared with the industrial group. However, the industrial group showed a significant increase in relative abundance of phylum Proteobacteria (p = 0.02). The most predominant genera for the rural group were Corynebacterium, Staphylococcus, Alloiococcus, and Peptoniphilus. By contrast, the industrial group was dominated by Staphylococcus, Sphingomonas, and Moraxella. Environmental pollution might alter the nasal microbiome leading to an attendant disturbance in the microbiome community structure. The clinical and public health implications of these nasal microbiome variations by rural and industrialized geography warrant further research. This study contributes to our knowledge of the bacterial composition of nasal microbiome in rural and industrialized geographies, and informs public health, respiratory medicine, and occupational health scholarship.

Revisiting cefditoren for the treatment of community-acquired infections caused by human-adapted respiratory pathogens in adults

Fifteen years after its licensure, this revision assesses the role of cefditoren facing the current pharmacoepidemiology of resistances in respiratory human-adapted pathogens (Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis). In the era of post- pneumococcal conjugate vaccines and in an environment of increasing diffusion of the ftsI gene among H. influenzae isolates, published studies on the cefditoren in vitro microbiological activity, pharmacokinetic/pharmcodynamic (PK/PD) activity and clinical efficacy are reviewed. Based on published data, an overall analysis is performed for PK/PD susceptibility interpretation. Further translation of PK/PD data into clinical/microbiological outcomes obtained in clinical trials carried out in the respiratory indications approved for cefditoren in adults (tonsillitis, sinusitis, acute exacerbation of chronic bronchitis and community-acquired pneumonia) is commented. Finally, the role of cefditoren within the current antibiotic armamentarium for the treatment of community respiratory tract infections in adults is discussed based on the revised information on its intrinsic activity, pharmacodynamic adequacy and clinical/bacteriological efficacy. Cefditoren remains an option to be taken into account when selecting an oral antibiotic for the empirical treatment of respiratory infections in the community caused by human-adapted pathogens, even when considering changes in the pharmacoepidemiology of resistances over the last two decades.

A future perspective on neurodegenerative diseases: nasopharyngeal and gut microbiota

Neurodegenerative diseases are considered a serious life-threatening issue regardless of age. Resulting nerve damage progressively affects important activities, such as movement, coordination, balance, breathing, speech and the functioning of vital organs. Reports on the subject have concluded that neurodegenerative disease can be caused by mutations of susceptible genes, alcohol consumption, toxins, chemicals and other unknown environmental factors. Although several diagnostic techniques can be used to determine aetiologies, the process is difficult and often fails. Research shows that nasopharyngeal and gut microbiota play important roles in brain to spinal cord coordination. However, no conclusive epidemiologic evidence is available on the roles played by respiratory and gut microbiota in the development of neurodegenerative diseases. Thus, understanding the connection between respiratory and gut microbiota and the nervous system could provide information on causal links. The present review describes future perspectives on the role played by nasopharyngeal and gut microbiota in the development of neurodegenerative diseases.

Pharmacodynamics for predicting therapeutic outcome and countering resistance spread: The cefditoren case

The relationship between pharmacokinetics and pharmacodynamics is a key instrument to improve antimicrobial stewardship and should be aimed to identification of the drug exposure measure that is closely associated not only with the ability to kill organisms but also to suppress the emergence of resistant subpopulations. This article reviews published studies for efficacy prediction with cefditoren and those aimed to explore its potential for countering resistance spread, focusing on the three most prevalent community-acquired isolates from respiratory infections: Streptococcus pneumoniae (S. pneumoniae), Haemophilus influenzae (H. influenzae) and Streptococcus pyogenes (S. pyogenes). Studies for efficacy prediction include in vitro pharmacodynamic simulations (using physiological concentrations of human albumin) and mice models (taking advantage of the same protein binding rate in mice and humans) to determine the value of the pharmacodynamic indices predicting efficacy, and Monte Carlo simulations to explore population pharmacodynamic coverage, as weapons for establishing breakpoints. Studies exploring the potential of cefditoren (free concentrations obtained with 400 mg cefditoren bid administration) for countering spread of resistance showed its capability for countering (1) intra-strain spread of resistance linked to ftsI gene mutations in H. influenzae; (2) the spread of H. influenzae resistant strains (with ftsI gene mutations) in multi-strain H. influenzae niches or of S. pneumoniae strains with multiple resistance traits in multi-strain S. pneumoniae niches; and (3) for overcoming indirect pathogenicity linked to β-lactamase production by H. influenzae that protects S. pyogenes in multibacterial niches. This revision evidences the ecological potential for cefditoren (countering resistance spread among human-adapted commensals) and its adequate pharmacodynamic coverage of respiratory pathogens (including those resistant to previous oral compounds) producing community-acquired infections.

Update on the clinical utility and optimal use of cefditoren

This article reviews and updates published data on cefditoren. The in vitro activity of cefditoren and its potential pharmacokinetic/pharmacodynamic adequacy to cover emerging resistance phenotypes in the present decade is reviewed. Cefditoren’s in vitro activity against most prevalent bacterial respiratory pathogens in the community and its pharmacokinetic/pharmacodynamic profile suggests a significant role for cefditoren in the treatment of respiratory tract infections. Clinical trials (in acute exacerbations of chronic bronchitis, community-acquired pneumonia, pharyngotonsillitis, and sinusitis) performed during clinical development outside Japan, mainly in adults, are reviewed, together with new clinical studies in the treatment of pharyngotonsillitis, sinusitis, and otitis media in children, mainly in Japan, for efficacy and safety assessment. The results of these studies support the adequacy of cefditoren for the treatment of community-acquired respiratory tract infections with a safety profile similar to previous oral antibiotics. From the data reviewed, it is concluded that cefditoren is an adequate option for the treatment of mild-to-moderate community-acquired respiratory infections, especially in geographical areas with a reported prevalence of phenotypes exhibiting nonsusceptibility to common oral antibiotics.

Variability and diversity of nasopharyngeal microbiota in children: a metagenomic analysis

The nasopharynx is the ecological niche for many commensal bacteria and for potential respiratory or invasive pathogens like Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. Disturbance of a balanced nasopharyngeal (NP) microbiome might be involved in the onset of symptomatic infections with these pathogens, which occurs primarily in fall and winter. It is unknown whether seasonal infection patterns are associated with concomitant changes in NP microbiota. As young children are generally prone to respiratory and invasive infections, we characterized the NP microbiota of 96 healthy children by barcoded pyrosequencing of the V5–V6 hypervariable region of the 16S-rRNA gene, and compared microbiota composition between children sampled in winter/fall with children sampled in spring. The approximately 1000000 sequences generated represented 13 taxonomic phyla and approximately 250 species-level phyla types (OTUs). The 5 most predominant phyla were Proteobacteria (64%), Firmicutes (21%), Bacteroidetes (11%), Actinobacteria (3%) and Fusobacteria (1,4%) with Moraxella, Haemophilus, Streptococcus, Flavobacteria, Dolosigranulum, Corynebacterium and Neisseria as predominant genera. The inter-individual variability was that high that on OTU level a core microbiome could not be defined. Microbiota profiles varied strongly with season, with in fall/winter a predominance of Proteobacteria (relative abundance (% of all sequences): 75% versus 51% in spring) and Fusobacteria (absolute abundance (% of children): 14% versus 2% in spring), and in spring a predominance of Bacteroidetes (relative abundance: 19% versus 3% in fall/winter, absolute abundance: 91% versus 54% in fall/winter), and Firmicutes. The latter increase is mainly due to (Brevi)bacillus and Lactobacillus species (absolute abundance: 96% versus 10% in fall/winter) which are like Bacteroidetes species generally related to healthy ecosystems. The observed seasonal effects could not be attributed to recent antibiotics or viral co-infection.

The NP microbiota of young children is highly diverse and appears different between seasons. These differences seem independent of antibiotic use or viral co-infection.

Cefditoren in upper and lower community-acquired respiratory tract infections

This article reviews and updates published data on cefditoren in the evolving scenario of resistance among the most prevalent isolates from respiratory tract infections in the community (Streptococcus pyogenes, Haemophilus influenzae, and Streptococcus pneumoniae). By relating the in vitro activity of cefditoren (in national and multinational surveillance and against isolates with emerging resistant genotypes/phenotypes) to its pharmacokinetics, the cefditoren pharmacodynamic activity predicting efficacy (in humans, animal models, and in vitro simulations) is analyzed prior to reviewing clinical studies (tonsillopharyngitis, sinusitis, acute exacerbations of chronic bronchitis, and community-acquired pneumonia) and the relationship between bacterial eradication and clinical efficacy. The high in vitro activity of cefditoren against the most prevalent respiratory isolates in the community, together with its pharmacokinetics (enabling a twice daily regimen) leading to adequate pharmacodynamic indexes covering all S. pyogenes, H. influenzae, and at least 95% S. pneumoniae isolates, makes cefditoren an antibiotic that will play a significant role in the treatment of respiratory tract infections in the community. In the clinical setting, studies carried out with cefditoren showed that treatments with the 400 mg twice daily regimen were associated with high rates of bacteriological response, even against penicillin-nonsusceptible S. pneumoniae, with good correlation between bacteriological efficacy/response and clinical outcome.

Interspecies effects in a ceftazidime-treated mixed culture of Pseudomonas aeruginosa, Burkholderia cepacia and Staphylococcus aureus: analysis at the single-species level

OBJECTIVES

in vitro studies commonly use single bacterial isolates for testing antibiotic susceptibilities. However, interspecies effects that may arise when mixed infections are treated with antibiotics can obviously not be investigated by this approach. In the study presented here, the effect of ceftazidime against a model microbial community consisting of Pseudomonas aeruginosa, Burkholderia cepacia and Staphylococcus aureus was studied in order to reveal effects that only may appear in a ceftazidime-treated mixed culture.

METHODS

time-kill experiments were conducted with mixed and pure cultures in a defined medium containing 30 mg/L ceftazidime. Interspecies effects were revealed by comparing growth and kill dynamics from time-kill experiments with results from untreated mixed and pure cultures. For species-specific cell enumeration, a quantitative terminal restriction fragment length polymorphism was used. Ceftazidime was measured by HPLC.

RESULTS

P. aeruginosa showed only a lytic phase in the ceftazidime-treated mixed culture, but not in the untreated mixed culture nor in the ceftazidime-treated pure culture. On the other hand, S. aureus did not lyse in the ceftazidime-treated mixed culture, while it did in the untreated mixed culture.

CONCLUSIONS

this finding suggests that the efficacy of ceftazidime against P. aeruginosa was increased by an interspecies effect during co-cultivation with B. cepacia and S. aureus. The latter seemed to be negatively affected by interspecies effects in mixed culture without ceftazidime. The same effect was nullified when ceftazidime was applied to the mixed culture. Further studies are required to reveal the underlying mechanisms.

Drug resistance in community-acquired respiratory tract infections: role for an emerging antibacterial

The nasopharynx is the ecological niche where evolution towards resistance occurs in respiratory tract isolates. Dynamics of different bacterial populations in antibiotic-free multibacterial niches are the baseline that antibiotic treatments can alter by shifting the competitive balance in favor of resistant populations. For this reason, antibiotic resistance is increasingly being considered to be an ecological problem. Traditionally, resistance has implied the need for development of new antibiotics for which basic efficacy and safety data are required prior to licensing. Antibiotic development is mainly focused on demonstrating clinical efficacy and setting susceptibility breakpoints for efficacy prediction. However, additional information on pharmacodynamic data predicting absence of selection of resistance and of resistant subpopulations, and specific surveillance on resistance to core antibiotics (to detect emerging resistances and its link with antibiotic consumption in the community) are valuable data in defining the role of a new antibiotic, not only from the perspective of its therapeutic potential but also from the ecologic perspective (countering resistances to core antibiotics in the community). The documented information on cefditoren gleaned from published studies in recent years is an example of the role for an emerging oral antibacterial facing current antibiotic resistance in community-acquired respiratory tract infections.