Staphylococcus aureus represents a serious infectious threat to global public health and a vaccine against S. aureus represents an unmet medical need. We here characterise two S. aureus vaccine candidates, coproporphyrinogen III oxidase (CgoX) and triose phosphate isomerase (TPI), which fulfil essential housekeeping functions in heme synthesis and glycolysis, respectively. Immunisation with rCgoX and rTPI elicited protective immunity against S. aureus bacteremia. Two monoclonal antibodies (mAb), CgoX-D3 and TPI-H8, raised against CgoX and TPI, efficiently provided protection against S. aureus infection. MAb-CgoX-D3 recognised a linear epitope spanning 12 amino acids (aa), whereas TPI-H8 recognised a larger discontinuous epitope. The CgoX-D3 epitope conjugated to BSA elicited a strong, protective immune response against S. aureus infection. The CgoX-D3 epitope is highly conserved in clinical S. aureus isolates, indicating its potential wide usability against S. aureus infection. These data suggest that immunofocusing through epitope-based immunisation constitutes a strategy for the development of a S. aureus vaccine with greater efficacy and better safety profile.

Introduction. Acinetobacter baumannii infections can be extremely challenging to treat owing to the worldwide prevalence of multidrug-resistant isolates, especially against carbapenems. Colonization with carbapenem-resistant A. baumannii (CRAb) requires rapid action from an infection control perspective because the organism is known for its propensity for epidemic spread. Hypothesis/Gap Statement. There is an unmet medical need to rapidly identify CRAb to enable appropriate antimicrobial treatment and to prevent transmission. Aim. Our aim was to expand the OXA-detection abilities of the rapid immunochromatographic test (ICT) OXA-23 K-SeT (Coris BioConcept) to include OXA-40- and OXA-58-like carbapenemases, which together confer carbapenem resistance to more than 94 % of CRAb isolates worldwide. Methodology. We used hybridoma technology to generate mAbs against OXA-40 and OXA-58 and selected them for productivity and specificity against recombinant and endogenous OXA-40 and OXA-58. Combinations of the resulting mAbs were analysed in ICT format for their ability to detect recombinant rOXA-40His6 or rOXA-58His6, respectively. Subsequently, selected antibody pairs were implemented into single-OXA-40 or single-OXA-58 prototypes and the final OXA-23/40/58/NDM ICT and were evaluated on clinical Acinetobacter spp. isolates with well-defined carbapenem resistance mechanisms. Results. Five anti-OXA-40 and anti-OXA-58 mAbs were selected. Competition ELISA with combinations of these antibodies revealed that the anti-OXA-40 antibodies bind to one of two binding clusters on OXA-40, while anti-OXA-58 antibodies bind to one of four binding clusters on OXA-58. Direct binding to the corresponding antigen in an ICT format has left only three antibodies against rOXA-40His6 and rOXA-58His6, respectively for the subsequent sandwich ICT selection procedure, which revealed that the anti-OXA-40 (#5) and anti-OXA-58 (#A8) mAbs in combination with the cross-reactive mAb #C8 performed best. They were implemented into single-OXA-40 and single-OXA-58 ICT prototypes and evaluated. These single ICT prototypes demonstrated 100 % specificity and sensitivity. Based on these results, an OXA-23/40/58/NDM-ICT was developed, complemented with OXA-23 and NDM-specific detection. An evaluation with selected carbapenem-resistant Acinetobacter spp. isolates (n=34) showed 100 % specificity. Conclusion. With this easy-to-use detection assay, one can save 12–48 h in diagnostics, which helps to treat patients earlier with appropriate antibiotics and allows immediate intervention to control transmission of CRAb.

The display of binding ligands, such as recombinant antibody fragments, on the surface of filamentous phage makes it possible to specifically attach these phage particles to target cells. After uptake of the phage, their internal single-stranded DNA is processed by the host cell, which allows transient expression of an encoded eukaryotic gene cassette. This opens the possibility to use bacteriophage as vectors for targeted gene therapy, although the transduction efficiency is very low.

Zusammenfassung: Impfungen gegen bakterielle Erreger spielen eine wichtige Rolle in der Prävention von Infektionen, insbesondere angesichts der wachsenden Antibiotikaresistenz. Historisch markierten Impfstoffe gegen Cholera, Diphtherie und Pertussis (Keuchhusten) erste bedeutende Fortschritte im Kampf gegen bakterielle Krankheiten. Später kamen Impfstoffe unter anderem gegen Meningokokken und Tetanus dazu. Bei diesen aktiven Immunisierungen wird das Immunsystem mit Teilen des Erregers konfrontiert, was die Bildung von Antikörpern, T‑Helferzellen, B‑Zellen und Gedächtniszellen anregt und dadurch einen langfristigen Schutz entstehen lässt. Die gezielte Entwicklung neuer Impfstoffe, auch gegen schwer behandelbare bakterielle Erreger, wird durch eine große Bandbreite von verschiedenen Impfstoffarten ermöglicht, darunter inaktivierte, toxoidbasierte und rekombinante Impfstoffe, sowie moderne Ansätze, wie die reverse Vakzinologie und messenger Ribonucleic Acid (mRNA)-Technologien verbunden mit verstärkenden Adjuvanzien. Neben der aktiven Immunisierung spielt die passive Immunisierung eine wichtige Rolle, bei der erregerspezifische Antikörper direkt verabreicht werden. Auf Bevölkerungsebene zeigen sich durch Impfprogramme deutliche epidemiologische Effekte, da Impfungen nicht nur Einzelpersonen, sondern auch Gemeinschaften schützen und damit zur Volksgesundheit beitragen. Trotz klarer medizinischer und ökonomischer Vorteile von Impfprogrammen muss deren Akzeptanz in der Bevölkerung durch objektive Informationspolitik noch deutlich erhöht werden. Derzeit befinden sich zahlreiche Impfstoffe in der Entwicklung, die durch innovative Technologien neue Wege eröffnen, bakterielle Infektionen wirksam zu verhindern und zu kontrollieren – ein entscheidender Schritt in einer Ära zunehmender Antibiotikaresistenz.