A role for the stringent response in ciprofloxacin resistance in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a major cause of nosocomial infections and the leading cause of chronic lung infections in cystic fibrosis and chronic obstructive pulmonary disease patients. Antibiotic treatment remains challenging because P. aeruginosa is resistant to high concentrations of antibiotics and has a remarkable ability to acquire mutations conferring resistance to multiple groups of antimicrobial agents. Here we report that when P. aeruginosa is plated on ciprofloxacin (cipro) plates, the majority of cipro-resistant (ciproR) colonies observed at and after 48 h of incubation carry mutations in genes related to the Stringent Response (SR). Mutations in one of the major SR components, spoT, were present in approximately 40% of the ciproR isolates. Compared to the wild-type strain, most of these isolates had decreased growth rate, longer lag phase and altered intracellular ppGpp content. Also, 75% of all sequenced mutations were insertions and deletions, with short deletions being the most frequently occurring mutation type. We present evidence that most of the observed mutations are induced on the selective plates in a subpopulation of cells that are not instantly killed by cipro. Our results suggests that the SR may be an important contributor to antibiotic resistance acquisition in P. aeruginosa.

Detection and Quantification of Mono-Rhamnolipids and Di-Rhamnolipids Produced by Pseudomonas aeruginosa.

The environmental bacterium Pseudomonas aeruginosa is an opportunistic pathogen with high antibiotic resistance that represents a health hazard. This bacterium produces high levels of biosurfactants known as rhamnolipids (RL), which are molecules with significant biotechnological value but are also associated with virulence traits. In this respect, the detection and quantification of RL may be useful for both biotechnology applications and biomedical research projects. In this article, we demonstrate step-by-step the technique to detect the production of the two forms of RL produced by P. aeruginosa using thin-layer chromatography (TLC): mono-rhamnolipids (mRL), molecules constituted by a dimer of fatty acids (mainly C10-C10) linked to one rhamnose moiety, and di-rhamnolipids (dRL), molecules constituted by a similar fatty acid dimer linked to two rhamnose moieties. Additionally, we present a method to measure the total amount of RL based on the acid hydrolysis of these biosurfactants extracted from a P. aeruginosa culture supernatant and the subsequent detection of the concentration of rhamnose that reacts with orcinol. The combination of both techniques can be used to estimate the approximate concentration of mRL and dRL produced by a specific strain, as exemplified here with the type strains PAO1 (phylogroup 1), PA14 (phylogroup 2), and PA7 (phylogroup 3).

The Anti-Microbial Peptide Citrocin Controls Pseudomonas aeruginosa Biofilms by Breaking Down Extracellular Polysaccharide.

Citrocin is an anti-microbial peptide that holds great potential in animal feed. This study evaluates the anti-microbial and anti-biofilm properties of Citrocin and explores the mechanism of action of Citrocin on the biofilm of P. aeruginosa. The results showed that Citrocin had a significant inhibitory effect on the growth of P. aeruginosa with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 0.3 mg/mL. All five concentrations (1/4MIC, 1/2MIC, MIC, 2MIC, and 4MIC) of Citrocin inhibited P. aeruginosa biofilm formation. Citrocin at the MIC, 2MIC and 4MIC removed 42.7%, 76.0% and 83.2% of mature biofilms, respectively, and suppressed the swarming motility, biofilm metabolic activity and extracellular polysaccharide production of P. aeruginosa. Metabolomics analysis indicated that 0.3 mg/mL of Citrocin up- regulated 26 and down-regulated 83 metabolites, mainly comprising amino acids, fatty acids, organic acids and sugars. Glucose and amino acid metabolic pathways, including starch and sucrose metabolism as well as arginine and proline metabolism, were highly enriched by Citrocin. In summary, our research reveals the anti-biofilm mechanism of Citrocin at the metabolic level, which provides theoretical support for the development of novel anti-biofilm strategies for combatting P. aeruginosa.

Tracking of Bacteriophage Predation on Pseudomonas aeruginosa Using a New Radiofrequency Biofilm Sensor.

Confronting the challenge of biofilm resistance and widespread antimicrobial resistance (AMR), this study emphasizes the need for innovative monitoring methods and explores the potential of bacteriophages against bacterial biofilms. Traditional methods, like optical density (OD) measurements and confocal microscopy, crucial in studying biofilm-virus interactions, often lack real-time monitoring and early detection capabilities, especially for biofilm formation and low bacterial concentrations. Addressing these gaps, we developed a new real-time, label-free radiofrequency sensor for monitoring bacteria and biofilm growth. The sensor, an open-ended coaxial probe, offers enhanced monitoring of bacterial development stages. Tested on a biological model of bacteria and bacteriophages, our results indicate the limitations of traditional OD measurements, influenced by factors like sedimented cell fragments and biofilm formation on well walls. While confocal microscopy provides detailed 3D biofilm architecture, its real-time monitoring application is limited. Our novel approach using radio frequency measurements (300 MHz) overcomes these shortcomings. It facilitates a finer analysis of the dynamic interaction between bacterial populations and phages, detecting real-time subtle changes. This method reveals distinct phases and breakpoints in biofilm formation and virion interaction not captured by conventional techniques. This study underscores the sensor's potential in detecting irregular viral activity and assessing the efficacy of anti-biofilm treatments, contributing significantly to the understanding of biofilm dynamics. This research is vital in developing effective monitoring tools, guiding therapeutic strategies, and combating AMR.

Adaptive response of Pseudomonas aeruginosa under serial ciprofloxacin exposure.

Understanding the evolution of antibiotic resistance is important for combating drug-resistant bacteria. In this work, we investigated the adaptive response of Pseudomonas aeruginosa to ciprofloxacin. Ciprofloxacin-susceptible P. aeruginosa ATCC 9027, CIP-E1 (P. aeruginosa ATCC 9027 exposed to ciprofloxacin for 14 days) and CIP-E2 (CIP-E1 cultured in antibiotic-free broth for 10 days) were compared. Phenotypic responses including cell morphology, antibiotic susceptibility, and production of pyoverdine, pyocyanin and rhamnolipid were assessed. Proteomic responses were evaluated using comparative iTRAQ labelling LC-MS/MS to identify differentially expressed proteins (DEPs). Expression of associated genes coding for notable DEPs and their related regulatory genes were checked using quantitative reverse transcriptase PCR. CIP-E1 displayed a heterogeneous morphology, featuring both filamentous cells and cells with reduced length and width. By contrast, although filaments were not present, CIP-E2 still exhibited size reduction. Considering the MIC values, ciprofloxacin-exposed strains developed resistance to fluoroquinolone antibiotics but maintained susceptibility to other antibiotic classes, except for carbapenems. Pyoverdine and pyocyanin production showed insignificant decreases, whereas there was a significant decrease in rhamnolipid production. A total of 1039 proteins were identified, of which approximately 25 % were DEPs. In general, there were more downregulated proteins than upregulated proteins. Noted changes included decreased OprD and PilP, and increased MexEF-OprN, MvaT and Vfr, as well as proteins of ribosome machinery and metabolism clusters. Gene expression analysis confirmed the proteomic data and indicated the downregulation of rpoB and rpoS. In summary, the response to CIP involved approximately a quarter of the proteome, primarily associated with ribosome machinery and metabolic processes. Potential targets for bacterial interference encompassed outer membrane proteins and global regulators, such as MvaT.

Qualitative and Quantitative Analysis of Siderophore Production from Pseudomonas aeruginosa.

Pseudomonas aeruginosa (P. aeruginosa) is known for its production of a diverse range of virulence factors to establish infections in the host. One such mechanism is the scavenging of iron through siderophore production. P. aeruginosa produces two different siderophores: pyochelin, which has lower iron-chelating affinity, and pyoverdine, which has higher iron-chelating affinity. This report demonstrates that pyoverdine can be directly quantified from bacterial supernatants, while pyochelin needs to be extracted from supernatants before quantification. The primary method for qualitatively analyzing siderophore production is the Chrome Azurol Sulfonate (CAS) agar plate assay. In this assay, the release of CAS dye from the Fe3+-Dye complex leads to a color change from blue to orange, indicating siderophore production. For the quantification of total siderophores, bacterial supernatants were mixed in equal proportions with CAS dye in a microtiter plate, followed by spectrophotometric analysis at 630 nm. Pyoverdine was directly quantified from the bacterial supernatant by mixing it in equal proportions with 50 mM Tris-HCl, followed by spectrophotometric analysis. A peak at 380 nm confirmed the presence of pyoverdine. As for Pyochelin, direct quantification from the bacterial supernatant was not possible, so it had to be extracted first. Subsequent spectrophotometric analysis revealed the presence of pyochelin, with a peak at 313 nm.

Alkyl quinolones mediate heterogeneous colony biofilm architecture that improves community-level survival.

Bacterial communities exhibit complex self-organization that contributes to their survival. To better understand the molecules that contribute to transforming a small number of cells into a heterogeneous surface biofilm community, we studied acellular aggregates, structures seen by light microscopy in Pseudomonas aeruginosa colony biofilms using light microscopy and chemical imaging. These structures differ from cellular aggregates, cohesive clusters of cells important for biofilm formation, in that they are visually distinct from cells using light microscopy and are reliant on metabolites for assembly. To investigate how these structures benefit a biofilm community we characterized three recurrent types of acellular aggregates with distinct geometries that were each abundant in specific areas of these biofilms. Alkyl quinolones (AQs) were essential for the formation of all aggregate types with AQ signatures outside the aggregates below the limit of detection. These acellular aggregates spatially sequester AQs and differentiate the biofilm space. However, the three types of aggregates showed differing properties in their size, associated cell death, and lipid content. The largest aggregate type co-localized with spatially confined cell death that was not mediated by Pf4 bacteriophage. Biofilms lacking AQs were absent of localized cell death but exhibited increased, homogeneously distributed cell death. Thus, these AQ-rich aggregates regulate metabolite accessibility, differentiate regions of the biofilm, and promote survival in biofilms.IMPORTANCEPseudomonas aeruginosa is an opportunistic pathogen with the ability to cause infection in the immune-compromised. It is well established that P. aeruginosa biofilms exhibit resilience that includes decreased susceptibility to antimicrobial treatment. This work examines the self-assembled heterogeneity in biofilm communities studying acellular aggregates, regions of condensed matter requiring alkyl quinolones (AQs). AQs are important to both virulence and biofilm formation. Aggregate structures described here spatially regulate the accessibility of these AQs, differentiate regions of the biofilm community, and despite their association with autolysis, correlate with improved P. aeruginosa colony biofilm survival.

Etiology of bacterial pneumonia and multi-drug resistance pattern among pneumonia suspected patients in Ethiopia: a systematic review and meta-analysis.

BACKGROUND: Bacterial pneumonia can affect all age groups, but people with weakened immune systems, young children, and the elderly are at a higher risk. Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa are the most common causative agents of pneumonia, and they have developed high MDR in recent decades in Ethiopia. This systematic review and meta-analysis aimed to determine the pooled prevalence of bacterial pneumonia and multidrug resistance in Ethiopia. METHODS: The articles were searched extensively in the electronic databases and grey literature using entry terms or phrases. Studies meeting the eligibility criteria were extracted in MS Excel and exported for statistical analysis into STATA version 14 software. The pooled prevalence of bacterial pneumonia and multidrug resistance were calculated using a random-effects model. Heterogeneity was assessed by using the I2 value. Publication bias was assessed using a funnel plot and Egger's test. A sensitivity analysis was done to assess the impact of a single study on the pooled effect size. RESULT: Of the 651 studies identified, 87 were eligible for qualitative analysis, of which 11 were included in the meta-analysis consisting of 1154 isolates. The individual studies reported prevalence of bacterial pneumonia ranging from 6.19 to 46.3%. In this systematic review and metanalysis, the pooled prevalence of bacterial pneumonia in Ethiopia was 37.17% (95% CI 25.72-46.62), with substantial heterogeneity (I2 = 98.4%, p < 0.001) across the studies. The pooled prevalence of multidrug resistance in bacteria isolated from patients with pneumonia in Ethiopia was 67.73% (95% CI: 57.05-78.40). The most commonly isolated bacteria was Klebsiella pneumoniae, with pooled prevalence of 21.97% (95% CI 16.11-27.83), followed by Streptococcus pneumoniae, with pooled prevalence of 17.02% (95% CI 9.19-24.86), respectively. CONCLUSION: The pooled prevalence of bacterial isolates from bacterial pneumonia and their multidrug resistance were high among Ethiopian population. The initial empirical treatment of these patients remains challenging because of the strikingly high prevalence of antimicrobial resistance.

Bronchiectasis-associated infections and outcomes in a large, geographically diverse electronic health record cohort in the United States.

BACKGROUND: Bronchiectasis is a pulmonary disease characterized by irreversible dilation of the bronchi and recurring respiratory infections. Few studies have described the microbiology and prevalence of infections in large patient populations outside of specialized tertiary care centers. METHODS: We used the Cerner HealthFacts Electronic Health Record database to characterize the nature, burden, and frequency of pulmonary infections among persons with bronchiectasis. Chronic infections were defined based on organism-specific guidelines. RESULTS: We identified 7,749 patients who met our incident bronchiectasis case definition. In this study population, the organisms with the highest rates of isolate prevalence were Pseudomonas aeruginosa with 937 (12%) individuals, Staphylococcus aureus with 502 (6%), Mycobacterium avium complex (MAC) with 336 (4%), and Aspergillus sp. with 288 (4%). Among persons with at least one isolate of each respective pathogen, 219 (23%) met criteria for chronic P. aeruginosa colonization, 74 (15%) met criteria for S. aureus chronic colonization, 101 (30%) met criteria for MAC chronic infection, and 50 (17%) met criteria for Aspergillus sp. chronic infection. Of 5,795 persons with at least two years of observation, 1,860 (32%) had a bronchiectasis exacerbation and 3,462 (60%) were hospitalized within two years of bronchiectasis diagnoses. Among patients with chronic respiratory infections, the two-year occurrence of exacerbations was 53% and for hospitalizations was 82%. CONCLUSIONS: Patients with bronchiectasis experiencing chronic respiratory infections have high rates of hospitalization.

Characterization of ß-lactamase and virulence genes in Pseudomonas aeruginosa isolated from clinical, environmental and poultry sources in Bangladesh.

The emergence and spread of multidrug-resistant pathogens like Pseudomonas aeruginosa are major concerns for public health worldwide. This study aimed to assess the prevalence of P. aeruginosa in clinical, environmental, and poultry sources in Bangladesh, along with their antibiotic susceptibility and the profiling of ß-lactamase and virulence genes using standard molecular and microbiology techniques. We collected 110 samples from five different locations, viz., BAU residential area (BAURA; n = 15), BAU Healthcare Center (BAUHCC; n = 20), BAU Veterinary Teaching Hospital (BAUVTH; n = 22), Poultry Market (PM; n = 30) and Mymensingh Medical College Hospital (MCCH; n = 23). After overnight enrichment in nutrient broth, 89 probable Pseudomonas isolates (80.90%) were screened through selective culture, gram-staining and biochemical tests. Using genus- and species-specific PCR, we confirmed 22 isolates (20.0%) as P. aeruginosa from these samples. Antibiogram profiling revealed that 100.0% P. aeruginosa isolates (n = 22) were multidrug-resistant isolates, showing resistance against Doripenem, Penicillin, Ceftazidime, Cefepime, and Imipenem. Furthermore, resistance to aztreonam was observed in 95.45% isolates. However, P. aeruginosa isolates showed a varying degree of sensitivity against Amikacin, Gentamicin, and Ciprofloxacin. The blaTEM gene was detected in 86.0% isolates, while blaCMY, blaSHV and blaOXA, were detected in 27.0%, 18.0% and 5.0% of the P. aeruginosa isolates, respectively. The algD gene was detected in 32.0% isolates, whereas lasB and exoA genes were identified in 9.0% and 5.0% P. aeruginosa isolates. However, none of the P. aeruginosa isolates harbored exoS gene. Hence, this study provides valuable and novel insights on the resistance and virulence of circulating P. aeruginosa within the clinical, environmental, and poultry environments of Bangladesh. These findings are crucial for understanding the emergence of ß-lactamase resistance in P. aeruginosa, highlighting its usefulness in the treatment and control of P. aeruginosa infections in both human and animal populations.

An agent-based model on antimicrobial de-escalation in intensive care units: Implications on clinical trial design.

Antimicrobial de-escalation refers to reducing the spectrum of antibiotics used in treating bacterial infections. This strategy is widely recommended in many antimicrobial stewardship programs and is believed to reduce patients' exposure to broad-spectrum antibiotics and prevent resistance. However, the ecological benefits of de-escalation have not been universally observed in clinical studies. This paper conducts computer simulations to assess the ecological effects of de-escalation on the resistance prevalence of Pseudomonas aeruginosa-a frequent pathogen causing nosocomial infections. Synthetic data produced by the models are then used to estimate the sample size and study period needed to observe the predicted effects in clinical trials. Our results show that de-escalation can reduce colonization and infections caused by bacterial strains resistant to the empiric antibiotic, limit the use of broad-spectrum antibiotics, and avoid inappropriate empiric therapies. Further, we show that de-escalation could reduce the overall super-infection incidence, and this benefit becomes more evident under good compliance with hand hygiene protocols among health care workers. Finally, we find that any clinical study aiming to observe the essential effects of de-escalation should involve at least ten arms and last for four years-a size never attained in prior studies. This study explains the controversial findings of de-escalation in previous clinical studies and illustrates how mathematical models can inform outcome expectations and guide the design of clinical studies.

Prevalence of meropenem-resistant Pseudomonas Aeruginosa in Ethiopia: a systematic review and meta­analysis.

INTRODUCTION: Antimicrobial resistance (AMR) is a pressing global health concern, particularly pronounced in low-resource settings. In Ethiopia, the escalating prevalence of carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) poses a substantial threat to public health. METHODS: A comprehensive search of databases, including PubMed, Scopus, Embase, Hinari, and Google Scholar, identified relevant studies. Inclusion criteria encompassed observational studies reporting the prevalence of meropenem-resistant P. aeruginosa in Ethiopia. Quality assessment utilized JBI checklists. A random-effects meta-analysis pooled data on study characteristics and prevalence estimates, with subsequent subgroup and sensitivity analyses. Publication bias was assessed graphically and statistically. RESULTS: Out of 433 studies, nineteen, comprising a total sample of 11,131, met inclusion criteria. The pooled prevalence of meropenem-resistant P. aeruginosa was 15% (95% CI: 10-21%). Significant heterogeneity (I2 = 83.6%) was observed, with the number of P. aeruginosa isolates identified as the primary source of heterogeneity (p = 0.127). Subgroup analysis by infection source revealed a higher prevalence in hospital-acquired infections (28%, 95% CI: 10, 46) compared to community settings (6%, 95% CI: 2, 11). Geographic based subgroup analysis indicated the highest prevalence in the Amhara region (23%, 95% CI: 8, 38), followed by Addis Ababa (21%, 95% CI: 11, 32), and lower prevalence in the Oromia region (7%, 95% CI: 4, 19). Wound samples exhibited the highest resistance (25%, 95% CI: 25, 78), while sputum samples showed the lowest prevalence. Publication bias, identified through funnel plot examination and Egger's regression test (p < 0.001), execution of trim and fill analysis resulted in an adjusted pooled prevalence of (3.7%, 95% CI: 2.3, 9.6). CONCLUSION: The noteworthy prevalence of meropenem resistance among P. aeruginosa isolates in Ethiopia, particularly in healthcare settings, underscores the urgency of implementing strict infection control practices and antibiotic stewardship. Further research is imperative to address and mitigate the challenges posed by antimicrobial resistance in the country.

The changing epidemiology of pulmonary infection in children and adolescents with cystic fibrosis: an 18-year experience.

The impact of evolving treatment regimens, airway clearance strategies, and antibiotic combinations on the incidence and prevalence of respiratory infection in cystic fibrosis (CF) in children and adolescents remains unclear. The incidence, prevalence, and prescription trends from 2002 to 2019 with 18,339 airway samples were analysed. Staphylococcus aureus [- 3.86% (95% CI - 5.28-2.43)] showed the largest annual decline in incidence, followed by Haemophilus influenzae [- 3.46% (95% CI - 4.95-1.96)] and Pseudomonas aeruginosa [- 2.80%95% CI (- 4.26-1.34)]. Non-tuberculous mycobacteria and Burkholderia cepacia showed a non-significant increase in incidence. A similar pattern of change in prevalence was observed. No change in trend was observed in infants < 2 years of age. The mean age of the first isolation of S. aureus (p < 0.001), P. aeruginosa (p < 0.001), H. influenza (p < 0.001), Serratia marcescens (p = 0.006) and Aspergillus fumigatus (p = 0.02) have increased. Nebulised amikacin (+ 3.09 ± 2.24 prescription/year, p = 0.003) and colistin (+ 1.95 ± 0.3 prescriptions/year, p = 0.032) were increasingly prescribed, while tobramycin (- 8.46 ± 4.7 prescriptions/year, p < 0.001) showed a decrease in prescription. Dornase alfa and hypertonic saline nebulisation prescription increased by 16.74 ± 4.1 prescriptions/year and 24 ± 4.6 prescriptions/year (p < 0.001). There is a shift in CF among respiratory pathogens and prescriptions which reflects the evolution of cystic fibrosis treatment strategies over time.

Significant role of pyocyanin and exotoxin A in the pathogenesis of Pseudomonas aeruginosa isolated from hospitalized patients.

AIM: Due to the importance of exotoxin A and pyocyanin in the pathogenicity of this bacterium, we decided to evaluate the prevalence of genes encoding these virulence factors in clinical isolates of P.aeruginosa.

PqsA mutation-mediated enhancement of phage-mediated combat against Pseudomonas aeruginosa.

Phage therapy is a potential approach in the biocontrol of foodborne pathogens. However, the emergence of phage resistance and the narrow host range of most phage isolates continue to limit the antimicrobial efficacy of phages. Here, we investigated the potential of the pqsA gene, encoding the anthranilate-CoA ligase enzyme, as an adjuvant for phage therapy. The knockout of the pqsA gene significantly enhanced the bactericidal effect of phages vB_Pae_QDWS and vB_Pae_S1 against Pseudomonas aeruginosa. Under phage infection pressure, the growth of the PaΔpqsA was significantly inhibited within 8 h compared to the wild-type PAO1. Furthermore, we found that altering phage adsorption is not how PaΔpqsA responds to phage infection. Although pqsA represents a promising target for enhancing phage killing, it may not be applicable to all phages, such as types vB_Pae_W3 and vB_Pae_TR. Our findings provide new material reserves for the future design of novel phage-based therapeutic strategies.

Nanocomposites against Pseudomonas aeruginosa biofilms: Recent advances, challenges, and future prospects.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that causes life-threatening and persistent infections in immunocompromised patients. It is the culprit behind a variety of hospital-acquired infections owing to its multiple tolerance mechanisms against antibiotics and disinfectants. Biofilms are sessile microbial aggregates that are formed as a result of the cooperation and competition between microbial cells encased in a self-produced matrix comprised of extracellular polymeric constituents that trigger surface adhesion and microbial aggregation. Bacteria in biofilms exhibit unique features that are quite different from planktonic bacteria, such as high resistance to antibacterial agents and host immunity. Biofilms of P. aeruginosa are difficult to eradicate due to intrinsic, acquired, and adaptive resistance mechanisms. Consequently, innovative approaches to combat biofilms are the focus of the current research. Nanocomposites, composed of two or more different types of nanoparticles, have diverse therapeutic applications owing to their unique physicochemical properties. They are emerging multifunctional nanoformulations that combine the desired features of the different elements to obtain the highest functionality. This review assesses the recent advances of nanocomposites, including metal-, metal oxide-, polymer-, carbon-, hydrogel/cryogel-, and metal organic framework-based nanocomposites for the eradication of P. aeruginosa biofilms. The characteristics and virulence mechanisms of P. aeruginosa biofilms, as well as their devastating impact and economic burden are discussed. Future research addressing the potential use of nanocomposites as innovative anti-biofilm agents is emphasized. Utilization of nanocomposites safely and effectively should be further strengthened to confirm the safety aspects of their application.

Chronic infective arthritis with osteomyelitis of the ankle due to Pseudomonas aeruginosa infection in a middle-age woman: A rare causative pathogen requiring vigilance.

RATIONALE: Pseudomonas aeruginosa-induced septic arthritis is a relatively uncommon phenomenon. It has been documented in children with traumatic wounds, young adults with a history of intravenous drug use, and elderly patients with recent urinary tract infections or surgical procedures. PATIENT CONCERNS: Fifty-nine year-old female had no reported risk factors. The patient sought medical attention due to a 6-month history of persistent pain and swelling in her right ankle. DIAGNOSES: Magnetic resonance imaging and a 3-phase bone scan revealed findings suggestive of infectious arthritis with concurrent osteomyelitis. Histopathological examination of the synovium suggested chronic synovitis, and synovial tissue culture confirmed the presence of P aeruginosa. INTERVENTION: Arthroscopic synovectomy and debridement, followed by 6 weeks of targeted antibiotic therapy for P aeruginosa. OUTCOMES: Following treatment, the patient experienced successful recovery with no symptom recurrence, although she retained a mild limitation in the range of motion of her ankle. LESSONS: To our knowledge, this is the first reported case of chronic arthritis and osteomyelitis caused by P aeruginosa in a patient without conventional risk factors. This serves as a crucial reminder for clinicians to consider rare causative organisms in patients with chronic arthritis. Targeted therapy is imperative for preventing further irreversible bone damage and long-term morbidity.

Airway commensal bacteria in cystic fibrosis inhibit the growth of P. aeruginosa via a released metabolite.

In cystic fibrosis (CF), Pseudomonas aeruginosa infection plays a critical role in disease progression. Although multiple studies suggest that airway commensals might be able to interfere with pathogenic bacteria, the role of the distinct commensals in the polymicrobial lung infections is largely unknown. In this study, we aimed to identify airway commensal bacteria that may inhibit the growth of P. aeruginosa. Through a screening study with more than 80 CF commensal strains across 21 species, more than 30 commensal strains from various species have been identified to be able to inhibit the growth of P. aeruginosa. The underlying mechanisms were investigated via genomic, metabolic and functional analysis, revealing that the inhibitory commensals may affect the growth of P. aeruginosa by releasing a large amount of acetic acid. The data provide information about the distinct roles of airway commensals and provide insights into novel strategies for controlling airway infections.

Experimentally evolved Staphylococcus aureus shows increased survival in the presence of Pseudomonas aeruginosa by acquiring mutations in the amino acid transporter, GltT.

When cultured together under standard laboratory conditions Pseudomonas aeruginosa has been shown to be an effective inhibitor of Staphylococcus aureus. However, P. aeruginosa and S. aureus are commonly observed in coinfections of individuals with cystic fibrosis (CF) and in chronic wounds. Previous work from our group revealed that S. aureus isolates from CF infections are able to persist in the presence of P. aeruginosa strain PAO1 with a range of tolerances with some isolates being eliminated entirely and others maintaining large populations. In this study, we designed a serial transfer, evolution experiment to identify mutations that allow S. aureus to survive in the presence of P. aeruginosa. Using S. aureus USA300 JE2 as our ancestral strain, populations of S. aureus were repeatedly cocultured with fresh P. aeruginosa PAO1. After eight coculture periods, S. aureus populations that survived better in the presence of PAO1 were observed. We found two independent mutations in the highly conserved S. aureus aspartate transporter, gltT, that were unique to evolved P. aeruginosa-tolerant isolates. Subsequent phenotypic testing demonstrated that gltT mutants have reduced uptake of glutamate and outcompeted wild-type S. aureus when glutamate was absent from chemically defined media. These findings together demonstrate that the presence of P. aeruginosa exerts selective pressure on S. aureus to alter its uptake and metabolism of key amino acids when the two are cultured together.