There is considerable interest in the use of bacteriophages (phages) to treat Pseudomonas aeruginosa infections associated with left ventricular assist devices (LVADs). These infections are often challenging to manage due to high rates of multidrug resistance and biofilm formation, which could potentially be overcome with the use of phages. We report a case of a 54-year-old man with relapsing multidrug-resistant P. aeruginosa LVAD driveline infection, who was treated with a combination of two lytic antipseudomonal phages administered intravenously and locally. Treatment was combined with LVAD driveline repositioning and systemic antibiotic administration, resulting in a successful outcome with clinical cure and eradication of the targeted bacteria. However, laboratory in vitro models showed that phages alone could not eradicate biofilms but could prevent biofilm formation. Phage-resistant bacterial strains evolved in biofilm models and showed decreased susceptibility to the phages used. Further studies are needed to understand the complexity of phage resistance and the interaction of phages and antibiotics. Our results indicate that the combination of phages, antibiotics, and surgical intervention can have great potential in treating LVAD-associated infections. More than 21 months post-treatment, our patient remains cured of the infection.

High-energy trauma with severe bone fractures can be complicated by infection, leading to the development of osteomyelitis. Pseudomonas aeruginosa is an important causative agent of such infections because of its high virulence profile and ability to develop resistance against a wide range of antimicrobials quickly. P. aeruginosa biofilms cause treatment failure and relapsing infections. Bacteriophages are viruses that can be used to treat biofilm-associated infections. Moreover, the combination of phages with certain antimicrobials have demonstrated synergistic and additive effects. We present a case of a 21-year-old patient with relapsing multidrug-resistant (MDR) P. aeruginosa femur osteomyelitis that developed after a road accident, with a proximal right femoral Grade III B open fracture and severe soft tissue damage. Despite extensive antimicrobial treatment and multiple surgical interventions with wound debridement, the infection persisted, with subsequent development of femoral osteomyelitis with a fistula. Patient care management included femoral head excision with wound debridement, intravenous (IV) ceftazidime-avibactam, and the local application of the lytic Pseudomonas bacteriophage cocktail BFC 1.10. Nine months after the intervention, the patient did not show any clinical, radiological, or laboratory signs of inflammation; therefore, hip replacement was performed. Nevertheless, recurrent P. aeruginosa infection evolved at the distal side of the femur and was successfully treated with conventional antimicrobials. In this case, wound debridement combined with antibiotics and bacteriophages resulted in bacterial eradication of proximal femoral segment, avoiding leg amputation, but failed to treat osteomyelitis in distal bone segment. An in vitro assessment of the isolated MDR P. aeruginosa strain for biofilm formation and phage susceptibility was performed. Additionally, the antimicrobial effects of ceftazidime-avibactam and BFC 1.10 were determined on planktonic cell growth and bacterial biofilm prevention was evaluated. The isolated bacterial strains were susceptible to the bacteriophage cocktail. Strong biofilm formation was detected 6 h after inoculation. Ceftazidime-avibactam combined with BFC 1.10 was most effective in preventing planktonic cell growth and biofilm formation. In both cases, the required concentration of ceftazidime-avibactam decreased two-fold. This study demonstrates the possible use of bacteriophages and antibiotics in difficult-to-treat bone and soft tissue infections, where the additive effects of phages and antibiotics were observed.

Background: Despite the widespread use of antibiotics to treat infected tonsils, episodes of tonsillitis tend to recur and turn into recurrent tonsillitis (RT) or are complicated by peritonsillar abscesses (PTAs). The treatment of RT and PTAs remains surgical, and tonsillectomies are still relevant. Materials and methods: In a prospective, controlled study, we analyzed the bacteria of the tonsillar crypts of 99 patients with RT and 29 patients with a PTA. We performed the biofilm formation and antibacterial susceptibility testing of strains isolated from study patients. We compared the results obtained between patient groups with the aim to identify any differences that may contribute to ongoing symptoms of RT or that may play a role in developing PTAs. Results: The greatest diversity of microorganisms was found in patients with RT. Gram-positive bacteria were predominant in both groups. Candida species were predominant in patients with a PTA (48.3% of cases). Irrespective of patient group, the most commonly isolated pathogenic bacterium was S. aureus (in 33.3% of RT cases and in 24.14% of PTA cases). The most prevalent Gram-negative bacterium was K. pneumoniae (in 10.1% of RT cases and in 13.4% of PTA cases). At least one biofilm-producing strain was found in 37.4% of RT cases and in 27.6% of PTA cases. Moderate or strong biofilm producers were detected in 16 out of 37 cases of RT and in 2 out of 8 PTA cases. There was a statistically significant association found between the presence of Gram-positive bacteria and a biofilm-formation phenotype in the RT group and PTA group (Pearson χ² test, p < 0.001). S. aureus and K. pneumoniae strains were sensitive to commonly used antibiotics. One S. aureus isolate was identified as MRSA. Conclusions: S. aureus is the most common pathogen isolated from patients with RT, and Candida spp. are the most common pathogens isolated from patients with a PTA. S. aureus isolates are susceptible to most antibiotics. Patients with RT more commonly have biofilm-producing strains, but patients with a PTA more commonly have biofilm non-producer strains. K. pneumoniae does not play a major role in biofilm production.

Background and Objective: Tonsillar crypts can be considered a reservoir for a variety of bacterial species. Some bacterial species can be considered part of the normal oropharyngeal microbiota. The roles of other pathogens, for example, the so-called non-oral and respiratory pathogens Staphylococcus aureus, Klebsiella, Pseudomonas, and Acinetobacter spp., which have strong virulence factors, biofilm production capacity, and the ability to initiate infectious diseases, are unclear. The purpose of this study was to detect the presence of S. aureus, K. pneumoniae, P. aeruginosa, and Acinetobacter spp. within the tonsillar crypts of healthy individuals, and to analyze the pathogens’ biofilm production and antibacterial resistances. Results: Only common oropharyngeal microbiota were cultivated from 37 participant samples (40.7%). The most commonly isolated pathogenic bacterium was S. aureus, which was isolated in 41 (45%) participant samples. K. pneumoniae was isolated in seven (7.7%) samples, Acinetobacter spp. were isolated in five (5.5%) samples, and P. aeruginosa was isolated in two (2.2%) samples. Biofilm producers predominated among the pathogenic bacteria; 51 strains were biofilm producers, and among them, 31 strains were moderate or strong biofilm producers. The tested S. aureus, K. pneumoniae, P. aeruginosa, and Acinetobacter spp. strains were sensitive to commonly used antibiotics (amoxicillin–clavulanic acid, clindamycin, or ciprofloxacin). One of the isolated S. aureus strains was MRSA. Conclusions: Biofilm is a commonly observed feature that seems to be a naturally existing form of pathogenic bacteria colonizing human tissue. S. aureus, K. pneumoniae, P. aeruginosa, and Acinetobacter spp. occasionally occur in the tonsillar crypts of healthy individuals, and, therefore, it is most likely that S. aureus, K. pneumoniae, P. aeruginosa, and Acinetobacter spp. in opportunistic tonsillar infections originate from the tonsillar crypt microbiota.

Escherichia coli is a common cause of biofilm-associated urinary tract infections. Bacteria inside the biofilm are more resistant to antibiotics. Six E. coli strains isolated from patients with urinary tract infections were screened for biofilm-forming capability and antimicrobial susceptibility. Two of the most significant biofilm-producing strains were selected for minimal inhibitory concentration and minimal biofilm eradication concentration in vitro testing using amoxicillin–clavulanic acid, ciprofloxacin, and three commercial bacteriophage cocktails (Pyobacteriophag, Ses, and Intesti). In case of a low phage effect, an adaptation procedure was performed. Although the biofilms formed by strain 021UR were resistant to amoxicillin–clavulanic acid and ciprofloxacin, the three phage cocktails were able to reduce biofilm formation. In contrast, phages did not affect the 01206UR strain against planktonic and biofilm-forming cells. After Pyobacteriophag adaptation, the effect improved, and, regardless of the concentration, the adapted phage cocktail could destroy both planktonic cells and the biofilm of strain 01206UR. Bacteriophages capable of killing bacteria in biofilms can be used as an alternative to antibiotics. However, each case should be considered individually due to the lack of clinical trials for phage therapy. Antimicrobial and phage susceptibility should be determined in biofilm models before treatment to achieve the desired anti-biofilm effect.

IgA nephropathy (IgAN) is characterised by the production of galactose-deficient IgA1 (GdIgA1) antibodies. As the source of pathogenic antibodies, B cells are central to IgAN pathogenesis, but the B cell activation pathways as well as the potential B cell source of dysregulated IgA-secretion remain unknown. We carried out flow cytometry analysis of peripheral blood B cells in patients with IgA nephropathy and control subjects with a focus on IgA-expressing B cells to uncover the pathways of B cell activation in IgAN and how these could give rise to pathogenic GdIgA1 antibodies. In addition to global changes in the B cell landscape – expansion of naive and reduction in memory B cells – IgAN patients present with an increased frequency of IgA-expressing B cells that lack the classical memory marker CD27, but are CD21^pos. IgAN patients further have an expanded population of IgA^pos antibody-secreting cells, which correlate with serum IgA levels. Both IgA^pos plasmabalsts and CD27^neg B cells co-express GdIgA1. Implicating dysregulation at mucosal surfaces as the driver of such B cell differentiation, we found a correlation between lipopolysaccharide (LPS) in the serum and IgA^posCD27^neg B cell frequency. We propose that dysregulated immunity in the mucosa may drive de novo B cell activation within germinal centres, giving rise to IgA^posCD27^neg B cells and subsequently IgA-producing plasmablasts. These data integrate B cells into the paradigm of IgAN pathogenesis and allow to further investigate this pathway to uncover biomarkers and develop therapeutic interventions.