Historical and regulatory perspectives on the treatment effect of antibacterial drugs for community-acquired pneumonia

[Therapy-relevant antibiotic resistances in a One Health context]

One Health refers to a concept that links human, animal, and environmental health. In Germany, there is extensive data on antibiotic resistance (AMR) and multidrug-resistant (micro)organisms (MDRO) in human and veterinary medicine, as well as from studies in various environmental compartments (soil, water, wastewater). All these activities are conducted according to different specifications and standards, which makes it difficult to compare data. A focus on AMR and MDRO of human therapeutic importance is helpful to provide some guidance. Most data are available across sectors on methicillin-resistant Staphylococcus aureus (MRSA) and multiresistant Enterobacterales such as Escherichia coli and Klebsiella pneumoniae. Here, the trends of resistance are heterogeneous. Antibiotic use leads to MRE selection, which is well documented. Success in minimizing antibiotic use has also been demonstrated in recent years in several sectors and could be correlated with success in containing AMR and MDRO (e.g., decrease in MRSA in human medicine). Sector-specific measures to reduce the burden of MDRO and AMR are also necessary, as not all resistance problems are linked to other sectors. Carbapenem resistance is still rare, but most apparent in human pathogens. Colistin resistance occurs in different sectors but shows different mechanisms in each. Resistance to antibiotics of last resort such as linezolid is rare in Germany, but shows a specific One Health correlation. Efforts to harmonize methods, for example in the field of antimicrobial susceptibility testing and genome-based pathogen and AMR surveillance, are an important first step towards a better comparability of the different data collections.

Psychological and cultural factors influencing antibiotic prescription

Humans have inundated the environment worldwide with antimicrobials for about one century, giving selective advantage to antibiotic-resistant bacteria. Therefore, antibiotic resistance has become a public health problem responsible for increased mortality and extended hospital stays because the efficacy of antibiotics has diminished. Hospitals and other clinical settings have implemented stewardship measures to reduce antibiotic administration and prescription. However, these measures demand multifactorial approaches, including multidisciplinary teams in clinical settings and the education of professionals and patients. Recent studies indicate that individual factors, such as mother-infant attachment and parenting styles, play a critical role in antibiotic use. Also, macrocontextual factors, such as economic, social, or cultural backgrounds, may impact antibiotic use rates. Therefore, research aiming to ameliorate stewardship measures must include psychologically and sociologically based research.

Atypical Pathogens in Adult Community-Acquired Pneumonia and Implications for Empiric Antibiotic Treatment: A Narrative Review

Atypical pathogens are intracellular bacteria causing community-acquired pneumonia (CAP) in a significant minority of patients. Legionella spp., Chlamydia pneumoniae and psittaci, Mycoplasma pneumoniae, and Coxiella burnetii are commonly included in this category. M. pneumoniae is present in 5-8% of CAP, being the second most frequent pathogen after Streptococcus pneumoniae. Legionella pneumophila is found in 3-5% of inpatients. Chlamydia spp. and Coxiella burnetii are present in less than 1% of patients. Legionella longbeachae is relatively frequent in New Zealand and Australia and might also be present in other parts of the world. Uncertainty remains on the prevalence of atypical pathogens, due to limitations in diagnostic means and methodological issues in epidemiological studies. Despite differences between CAP caused by typical and atypical pathogens, the clinical presentation alone does not allow accurate discrimination. Hence, antibiotics active against atypical pathogens (macrolides, tetracyclines and fluoroquinolones) should be included in the empiric antibiotic treatment of all patients with severe CAP. For patients with milder disease, evidence is lacking and recommendations differ between guidelines. Use of clinical prediction rules to identify patients most likely to be infected with atypical pathogens, and strategies of narrowing the antibiotic spectrum according to initial microbiologic investigations, should be the focus of future investigations.

The Assessment of Convalescent Plasma Efficacy against COVID-19

Antibody-based therapy for infectious diseases predates modern antibiotics and, in the absence of other therapeutic options, was deployed early in the SARS-CoV-2 pandemic through COVID-19 convalescent plasma (CCP) administration. Although most studies have demonstrated signals of efficacy for CCP, definitive assessment has proved difficult under pandemic conditions, with rapid changes in disease incidence and the knowledge base complicating the design and implementation of randomized controlled trials. Nevertheless, evidence from a variety of studies demonstrates that CCP is as safe as ordinary plasma and strongly suggests that it can reduce mortality if given early and with sufficient antibody content.

Pneumococcal conjugate vaccine use during humanitarian crises

Streptococcus pneumoniae is a common human commensal that causes a sizeable part of the overall childhood mortality in low income settings. Populations affected by humanitarian crises are at especially high risk, because a multitude of risk factors that are enhanced during crises increase pneumococcal transmission and disease severity. Pneumococcal conjugate vaccines (PCVs) provide effective protection and have been introduced into the majority of routine childhood immunisation programmes globally, though several barriers have hitherto limited their uptake during humanitarian crises. When PCV coverage cannot be sustained during crises or when PCV has not been part of routine programmes, mass vaccination campaigns offer a quick acting and programmatically feasible bridging solution until services can be restored. However, we currently face a paucity of evidence on which to base the structure of such campaigns. We believe that, now that PCV can be procured at a substantially reduced price through the Humanitarian Mechanism, this lack of information is a remaining hurdle to PCV use in humanitarian crises. Considering the difficulties in conducting research in crises, we propose an evidence generation pathway consisting of primary data collection in combination with mathematical modelling followed by quasi-experimental evaluation of a PCV intervention, which can inform on optimal vaccination strategies that consider age targeting, dosing regimens and impact duration.

Opsonic monoclonal antibodies enhance phagocytic killing activity and clearance of Mycobacterium tuberculosis from blood in a quantitative qPCR mouse model

Background

Patients with impaired immunity often have rapid progression of tuberculosis (TB) which can lead to highly lethal Mycobacterium tuberculosis (MTB) sepsis. Opsonic monoclonal antibodies (MABs) directed against MTB that enhance phagocytic killing activity and clearance of MTB from blood may be useful to enhance TB immunity.

Methods

BALB/c mice were immunized with ethanol-killed MTB (EK-MTB) and MABs were produced and screened by ELISA for binding to killed and live Mycobacterium smegmatis (SMEG) and MTB. MAB opsonophagocytic killing activity (OPKA) was examined using SMEG with HL60 and U-937 cells and MTB with U-937 cells. Clearance of MTB from blood was evaluated in Institute of Cancer Research (ICR) mice given opsonic anti-MTB MABs or saline (control) 24 h prior to intravenous infusion with 10⁸ CFUs gamma-irradiated MTB (HN878). MTB levels in murine blood collected 0.25, 4 and 24 h post-challenge were assessed by qPCR. MAB binding to peptidoglycan (PGN) was examined by ELISA using PGN cell wall mixture and ultra-pure PGN.

Results

Two MABs (GG9 and JG7) bound to killed and live SMEG and MTB (susceptible and resistant), and promoted OPKA with live MTB. MAB JG7 significantly enhanced OPKA of MTB. Both MABs significantly enhanced clearance of killed MTB from murine blood at 4 and 24 h as measured by qPCR. These opsonic MABs bound to PGN, a major cell wall constituent.

Conclusions

Anti-MTB MABs that promote bactericidal phagocytic activity of MTB and enhance clearance of killed MTB from the blood, may offer an immunotherapeutic approach for treatment of MTB bacteremia or sepsis, and augment treatment of multi-drug resistant (MDR) or extensively drug resistant (XDR) TB.

The promise and peril of universal health care

Universal health care (UHC) is garnering growing support throughout the world, a reflection of social and economic progress and of the recognition that population health is both an indicator and an instrument of national development. Substantial human and financial resources will be required to achieve UHC in any of the various ways it has been conceived and defined. Progress toward achieving UHC will be aided by new technologies, a willingness to shift medical tasks from highly trained to appropriately well-trained personnel, a judicious balance between the quantity and quality of health care services, and resource allocation decisions that acknowledge the important role of public health interventions and nonmedical influences on population health.

The AbgT family: A novel class of antimetabolite transporters

The AbgT family of transporters was thought to contribute to bacterial folate biosynthesis by importing the catabolite p-aminobenzoyl-glutamate for producing this essential vitamin. Approximately 13,000 putative transporters of the family have been identified. However, before our work, no structural information was available and even functional data were minimal for this family of membrane proteins. To elucidate the structure and function of the AbgT family of transporters, we recently determined the X-ray structures of the full-length Alcanivorax borkumensis YdaH and Neisseria gonorrhoeae MtrF membrane proteins. The structures reveal that these two transporters assemble as dimers with architectures distinct from all other families of transporters. Both YdaH and MtrF are bowl-shaped dimers with a solvent-filled basin extending from the cytoplasm halfway across the membrane bilayer. The protomers of YdaH and MtrF contain nine transmembrane helices and two hairpins. These structures directly suggest a plausible pathway for substrate transport. A combination of the crystal structure, genetic analysis and substrate accumulation assay indicates that both YdaH and MtrF behave as exporters, capable of removing the folate metabolite p-aminobenzoic acid from bacterial cells. Further experimental data based on drug susceptibility and radioactive transport assay suggest that both YdaH and MtrF participate as antibiotic efflux pumps, importantly mediating bacterial resistance to sulfonamide antimetabolite drugs. It is possible that many of these AbgT-family transporters act as exporters, thereby conferring bacterial resistance to sulfonamides. The AbgT-family transporters may be important targets for the rational design of novel antibiotics to combat bacterial infections.

Crystal structure of the Alcanivorax borkumensis YdaH transporter reveals an unusual topology

The potential of the folic acid biosynthesis pathway as a target for the development of antibiotics has been clinically validated. However, many pathogens have developed resistance to these antibiotics, prompting a reevaluation of potential drug targets within the pathway. The ydaH gene of Alcanivorax borkumensis encodes an integral membrane protein of the AbgT family of transporters for which no structural information was available. Here, we report the crystal structure of A. borkumensis YdaH, revealing a dimeric molecule with an architecture distinct from other families of transporters. YdaH is a bowl-shaped dimer with a solvent-filled basin extending from the cytoplasm to halfway across the membrane bilayer. Each subunit of the transporter contains nine transmembrane helices and two hairpins that suggest a plausible pathway for substrate transport. Further analyses also suggest that YdaH could act as an antibiotic efflux pump and mediate bacterial resistance to sulfonamide antimetabolite drugs.

Assessment of bias in outcomes reported in trials on pneumonia: a systematic review

Subjective outcomes may exaggerate intervention effects compared to objectively measured outcomes. We compared effect estimates for clinical failure and all-cause mortality clinical trials of antibiotic treatment for pneumonia. A systematic review of randomized controlled trials assessing adults with pneumonia, comparing different antibiotics, published between 2005 and 2012 was undertaken. We compared the intervention to the control arm. The all-cause mortality in the intention-to-treat population and clinical failure as defined by the study investigators for the primary analyzed population were the primary outcomes examined. Risk ratios (RRs) with 95 % confidence intervals (CIs) were pooled, using a fixed effect model. Meta-regression was used to examine the impact of clinical failure on the mortality effect size. Thirty-six trials were included, of which 30 were industry-sponsored and 30 were non-inferiority trials. There was no difference between the effect on mortality for intervention versus control (RR 1.02, 95 % CI 0.91-1.16) and clinical failure (RR 1.01, 95 % CI 0.93-1.10), without significant heterogeneity in both analyses. In double-blind trials with adequate sequence generation and concealment, there was a significant advantage to the intervention for clinical failure (RR 0.86, 95 % CI 0.76-0.98), but not for mortality (RR 0.96, 95 % CI 0.76-1.21). RRs for clinical failure did not explain the variability in the RRs for mortality significantly, with a meta-regression coefficient of 0.32 (95 % CI -0.21-0.85). In non-inferiority trials of antibiotic treatment for pneumonia, we did not find evidence for bias induced by the use of a subjective outcome overall. The small number of trials without sponsorship precludes an adequate assessment of sponsorship effects.

Design of clinical trials of antibacterial agents for community-acquired bacterial pneumonia

Standards for the conduct of clinical trials of antibacterial agents for community-acquired bacterial pneumonia (CABP) have changed dramatically in recent years. A draft guidance from the US FDA on the conduct of such trials was issued in March 2009. However, the guidance has already faced substantial criticism during the open public comment period, resulting in uncertainty regarding the appropriate design of such studies from a regulatory perspective. Controversies regarding the magnitude of the treatment effect associated with antibacterial therapy versus placebo/no therapy, the appropriate timing, nature and noninferiority margin for the primary efficacy end point, and other clinical and statistical issues have complicated efforts to reach consensus on appropriate trial design of antibacterial therapy for CABP. It is critical that studies of new drugs for CABP are designed to ensure that they are feasible to conduct and that their results are scientifically valid, statistically rigorous and clinically meaningful. Based on 3 years of active dialog between clinical, statistical, and regulatory experts, this article proposes an approach to enable a balance of clinical trial feasibility with appropriate scientific, statistical and clinical rigor.

Nanoscale particle therapies for wounds and ulcers

‘Small is beautiful’ – this should be the slogan of nanoscientists. Indeed, working with particles less than 100 nm in size, nanotechnology is on the verge of providing a host of new materials and approaches, revolutionizing applied medicine. The obvious potential of nanotechnology has attracted considerable investment from governments and industry hoping to drive its economic development. Several areas of medical care already benefit from the advantages that nanotechnology provides and its application in wound healing will be reviewed in this article.

Impact of burden on granulocyte clearance of bacteria in a mouse thigh infection model

We wished to delineate granulocytes' impact on the clearance of different bacterial burdens of Pseudomonas aeruginosa and Staphylococcus aureus in a granulocyte-replete mouse thigh infection model. A mouse thigh model was employed. Bacterial challenges from 10(5) to 3 × 10(7) CFU (S. aureus) and from 3 × 10(4) to 3 × 10(8) CFU (P. aeruginosa) were injected into murine posterior thighs. Organism quantitation was at baseline, 2 h (Pseudomonas only), and 24 h. A Michaelis-Menten population model was fit to the data for each organism. Breakpoints for microbial containment by granulocytes were identified. Bacterial burdens exceeding that breakpoint value resulted in organism multiplication. The Michaelis-Menten model fit the data well. For P. aeruginosa, the observed-predicted plot had a regression equation that explained over 98% of the variance (P ≪ 0.001). For S. aureus, this relationship explained greater than 94% of the variance (P ≪ 0.001). Maximal growth rate constants, maximal population burdens, and the bacterial loads at which granulocytes killed if half-saturated were not different. The kill rate constant for P. aeruginosa was almost 10 times that of S. aureus. Bacterial kill by granulocytes is saturable. No difference between saturation points of different isolates was seen. A higher bacterial burden means an increasing reliance on chemotherapy to drive bacterial clearance.

Overview of recent studies of community-acquired pneumonia

All recent studies of antibacterial drugs for the indication of community-acquired pneumonia submitted to the US Food and Drug Administration have been designed as noninferiority studies. We provide a summary of results of 7 recent clinical studies of oral antibacterial drugs for treatment of community-acquired pneumonia. In these 7 studies, the majority of patients enrolled had Pneumonia Patient Outcomes Research Team scores of I or II. The percentage of randomized subjects with pathogens identified at baseline ranged from 47% to 76%, and the percentage of subjects with Streptoccocus pneumoniae isolated at baseline ranged from approximately 6% to 20%. The primary end point in these studies was clinical cure, assessed 7-21 days after completion of therapy. Clinical cure rates were >80% in the intent-to-treat populations and >90% in the per-protocol populations. We also briefly summarize the results from several recently submitted clinical studies of intravenously administered antibacterial drugs for treatment of community-acquired pneumonia, in which we found similar results.