Designing phage cocktails to combat the emergence of bacteriophage-resistant mutants in multidrug-resistant Klebsiella pneumoniae.

IMPORTANCE: In this study, we aimed to design a novel and effective bacteriophage cocktail that can target both wild-type bacteria and phage-resistant mutants. To achieve this goal, we isolated four phages (U2874, phi_KPN_H2, phi_KPN_S3, and phi_KPN_HS3) that recognized different bacterial surface molecules using phage-resistant bacteria. We constructed three phage cocktails and tested their phage resistance-suppressing ability against multidrug-resistant Klebsiella pneumoniae. We argue that the phage cocktail that induces resensitization of phage susceptibility exhibited superior phage resistance-suppressing ability. Moreover, we observed trade-off effects that manifested progressively in phage-resistant bacteria. We hypothesize that such trade-off effects can augment therapeutic efficacy. We also recommend collating phage host range data against phage-resistant mutants in addition to wild-type bacteria when establishing phage banks to improve the efficiency of phage therapy. Our study underscores the importance of phage host range data in constructing effective phage cocktails for clinical use.

Appelmans protocol - A directed in vitro evolution enables induction and recombination of prophages with expanded host range.

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) present significant healthcare challenges due to limited treatment options. Bacteriophage (phage) therapy offers potential as an alternative treatment. However, the high host specificity of phages poses challenges for their therapeutic application. To broaden the phage spectrum, laboratory-based phage training using the Appelmans protocol was employed in this study. As a result, the protocol successfully expanded the host range of a phage cocktail targeting CRAB. Further analysis revealed that the expanded host range phages isolated from the output cocktail were identified as recombinant derivatives originating from prophages induced from encountered bacterial strains. These findings provide valuable genetic insights into the protocol's mechanism when applied to phages infecting A. baumannii strains that have never been investigated before. However, it is noteworthy that the expanded host range phages obtained from this protocol exhibited limited stability, raising concerns about their suitability for therapeutic purposes.

First Report of New Delhi Metallo-ß-Lactamase Carbapenemase-Producing Acinetobacter baumannii in Peru.

Here we report the first incidence of New Delhi metallo-ß-lactamase (NDM-1)-producing Acinetobacter baumannii in Peru, identified via a strain-based nosocomial surveillance project carried out in Lima and Iquitos. The bla NDM-1 gene was detected by multiplex polymerase chain reaction (PCR) and confirmed by loci sequencing. Acinetobacter baumannii is a nearly ubiquitous and promiscuous nosocomial pathogen, and the acquisition of bla NDM-1 by A. baumannii may facilitate an increase in the prevalence of this important resistance marker in other nosocomial pathogens.