This study evaluated the capacity of 23 multidrug-resistant (MDR) clinical isolates of Acinetobacter baumannii to adhere to respiratory epithelial cell surfaces and to form biofilm on a polystyrene surface. All 23 A. baumannii isolates were capable of adhering efficiently to respiratory epithelial cells, and biofilm production was positively associated with epithelial cell adhesiveness (r 0.80, p <0.0001). In the presence of the chelating agent EDTA, biofilm formation was markedly reduced. Cell adhesiveness and biofilm formation were significantly higher in isolates carrying the bla_PER-1 gene as compared with isolates without this extended-spectrum β-lactamase gene (p <0.005 and p <0.001, respectively). Further examination by RT-PCR showed a positive correlation between the level of expression of the bla_PER-1 gene and the level of biofilm formation (r 0.89, p <0.0001) and cell adhesiveness (r 0.74, p <0.006). Overall, the study demonstrated a high capacity of clinical isolates of MDR A. baumannii to form biofilm and to adhere to respiratory epithelial cells. This feature, combined with multidrug resistance, might contribute to the survival of these organisms and their dissemination in the hospital environment.

Multidrug-resistant (MDR) bacteria are a major concern in public health. Endolysins (lysins) from bacteriophage can be used as a novel antimicrobial agent against bacterial infectious diseases. In this study, a novel endolysin (LysSS) containing a lysozyme-like domain was evaluated for its antibacterial activity against various bacterial species. LysSS-encoding gene was analyzed and cloned and LysSS recombinant protein was expressed and purified. Purified LysSS was used to determine antimicrobial activities against various bacterial speciesin vitro and to measure its protection rate against Acinetobacter baumannii systemic infection model in vivo. Recombinant LysSS showed activity against MDRAcinetobacter baumannii, MDR Escherichia coli, MDR Klebsiella pneumoniae, MDR Pseudomonas aeruginosa, and Salmonella without pretreatment with an outer membrane permeabilizer. Moreover, LysSS inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration of LysSS against 16 strains of MDR Acinetobacter baumannii ranged from 0.063 to 0.25 mg/mL. LysSS had no cytotoxic effect on A549 human lung cells under 250 µg/mL. In an animal model, mice infected with A. baumannii were protected with a 40% survival rate by intraperitoneal injection of LysSS. Our current results demonstrated that LysSS can be a novel and promising antimicrobial agent against MRSA and MDR Gram-negative bacteria includingA. baumannii and P. aeruginosa.

Lytic bacteriophages (phages) have been investigated as treatments for bacterial infectious diseases. An induced phage, SAP-26, was isolated from a clinical isolate of Staphylococcus aureus. It belongs to the family Siphoviridae and its genome consists of double-stranded 41,207 bp DNA coding for 63 open reading frames. The phage SAP-26 showed a wide spectrum of lytic activity against both methicillin-resistant S. aureus and methicillin-susceptible S.aureus. Furthermore, combined treatment with a phage and antimicrobial agents showed a strong biofilm removal effect which induced structural changes in the biofilm matrix and a substantial decrease in the number of bacteria. Such a broad host range in S. aureus and biofilm removal activity of the phage SAP-26 suggests the possibility of its use as a therapeutic phage in combination with appropriate antimicrobial agent(s). Among the three antimicrobial agents combined with phage, the combination of rifampicin showed the best biofilm removal effect. To the authors' knowledge, this study showed for the first time that S. aureus biofilm could be efficiently eradicated with the mixture of phage and an antimicrobial agent, especially rifampicin.

Recently, lytic bacteriophages (phages) have been focused on treating bacterial infectious diseases. We investigated the protective efficacy of a novel Pseudomonas aeruginosa phage, PA1Ø, in normal and neutropenic mice. A lethal dose of P. aeruginosa PAO1 was administered via the intraperitoneal route and a single dose of PA1Ø with different multiplicities of infection (MOI) was treated into infected mice. Immunocompetent mice infected with P. aeruginosa PAO1 were successfully protected by PA1Ø of 1 MOI, 10 MOI or 100 MOI with 80% to 100% survival rate. No viable bacteria were found in organ samples after 48 h of the phage treatment. Phage clearing patterns were different in the presence or absence of host bacteria but PA1Ø disappeared from all organs after 72 h except spleen in the presence of host bacteria. On the contrary, PA1Ø treatment could not protect neutropenic mice infected with P. aeruginosa PAO1 even though could extend their lives for a short time. In in vitro phage-neutrophil bactericidal test, a stronger bactericidal effect was observed in phage-neutrophil co-treatment than in phage single treatment without neutrophils, suggesting phage-neutrophil co-work is essential for the efficient killing of bacteria in the mouse model. In conclusion, PA1Ø can be possibly utilized in future phage therapy endeavors since it exhibited strong protective effects against virulent P. aeruginosa infection.

The collection of whole microbial communities (bacteria, archaea, fungi, and viruses) together constitutes the gut microbiome. Diet, age, stress, host genetics, and diseases cause increases or decreases in the relative abundance and diversity of bacterial species (dysbiosis). We aimed to investigate the gut microbial composition at different taxonomic levels of healthy controls (HCs) with active Crohn’s disease (CD), ulcerative colitis (UC), and ischemic colitis (IC) using culture- and non-culture-based approaches and identify biomarkers to discriminate CD, UC, or IC. We determined the specific changes in the gut microbial profile using culture-independent (16S rRNA gene amplicon sequencing) as well as culture-based (culturomic) approaches. Biomarkers were validated using quantitative Real-Time PCR (qPCR). In both methods, bacterial diversity and species richness decreased in disease-associated conditions compared with that in HCs. Highly reduced abundance of Faecalibacterium prausnitzii and Prevotella sp. and an increased abundance of potentially pathogenic bacteria such as Enterococcus faecium, Enterococcus faecalis, and Escherichia coli in all CD, UC, or IC conditions were observed. We noted a high abundance of Latilactobacillus sakei in CD patients; Ligilactobacillus ruminis in UC patients; and Enterococcus faecium, Escherichia coli, and Enterococcus faecalis in IC patients. Highly reduced abundance of Faecalibacterium prausnitzii in all cases, and increased abundance of Latilactobacillus sakei and Enterococcus faecium in CD, Ligilactobacillus ruminis and Enterococcus faecium in UC, and Enterococcus faecium, Escherichia coli, and Enterococcus faecalis in IC could be biomarkers for CD, UC, and IC, respectively. These biomarkers may help in IBD (CD or UC) and IC diagnosis.

Acinetobacter baumannii is an aerobic and gram-negative pathogenic bacterium that is resistant to most antibiotics. Recently, A. baumannii 1656-2 exhibited the ability to form biofilms under clinical conditions. In this study, global metabolite profiling of both planktonic and biofilm forms of A. baumannii 1656-2 was performed using high-resolution nuclear magnetic resonance (NMR) spectroscopy and multivariate statistical analysis to investigate the metabolic patterns leading to biofilm formation. Principal components analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) score plots showed a distinct separation between planktonic and biofilm cells. Metabolites including acetates, pyruvate, succinate, UDP-glucose, AMP, glutamate, and lysine were increasingly involved in the energy metabolism of biofilm formation. In particular, the ratio of N-acetyl-D-glucosamine (GlcNAc) to D-glucosamine (GlcNH₂) was significantly higher during biofilm formation than under the planktonic condition. This study demonstrates that NMR-based global metabolite profiling of bacterial cells can provide valuable insight into the metabolic changes in multidrug resistant and biofilm-forming bacteria such as A. baumannii 1656-2.