Real-time monitoring of Pseudomonas aeruginosa biofilm growth dynamics and persister cells' eradication

Exploring Citronella's inhibitory mechanism against Listeria monocytogenes and its utilization in preserving cheese

Listeria monocytogenes presents significant risk to human health due to its high resistance and capacity to form toxin-producing biofilms that contaminate food. The objective of this study was to assess the inhibitory effect of citronella aldehyde (CIT) on L. monocytogenes and investigate the underlying mechanism of inhibition. The results indicated that the minimum inhibitory concentration (MIC) and Minimum sterilisation concentration (MBC) of CIT against L. monocytogenes was 2 μL/mL. At this concentration, CIT was able to effectively suppress biofilm formation and reduce metabolic activity. Crystalline violet staining and MTT reaction demonstrated that CIT was able to inhibit biofilm formation and reduce bacterial cell activity. Furthermore, the motility assessment assay revealed that CIT inhibited bacterial swarming and swimming. Scanning electron microscopy (SEM) and laser confocal microscopy (LSCM) observations revealed that CIT had a significant detrimental effect on L. monocytogenes cell structure and biofilm integrity. LSCM also observed that nucleic acids of L. monocytogenes were damaged in the CIT-treated group, along with an increase in bacterial extracellular nucleic acid leakage. The proteomic results also confirmed the ability of CIT to affect the expression of proteins related to processes including metabolism, DNA replication and repair, transcription and biofilm formation in L. monocytogenes. Consistent with the proteomics results are ATPase activity and ATP content of L. monocytogenes were significantly reduced following treatment with various concentrations of CIT. Notably, CIT showed good inhibitory activity against L. monocytogenes on cheese via fumigation at 4 °C.This study establishes a foundation for the potential application of CIT in food safety control.

Real-time biofilm detection techniques: advances and applications

Microbial biofilms, complex assemblies enveloped in extracellular matrices, are significant contributors to various infections. Traditional in vitro biofilm characterization methods, though informative, often disrupt the biofilm structure. The need to address biofilm-related infections urgently emphasizes the importance of continuous monitoring and timely interventions. This review provides a focused examination of advancements in real-time biofilm detection techniques, specifically in electrochemical, optical and mechanical systems. The potential applications of real-time detection in managing and monitoring biofilm growth in industrial settings, preventing medical infections, comprehending biofilm dynamics and evaluating control strategies highlight the necessity for it. Crucially, the review emphasizes the importance of evaluating these methods for their accuracy and reliability in real-time biofilm detection, offering valuable insights for precise interventions across various applications.

Pseudomonas aeruginosa two-component system LadS/PA0034 regulates macrophage phagocytosis via fimbrial protein cupA1

Pseudomonas aeruginosa is one of the most common nosocomial pathogens worldwide, known for its virulence, drug resistance, and elaborate sensor-response network. The primary challenge encountered by pathogens during the initial stages of infection is the immune clearance arising from the host. The resident macrophages of barrier organs serve as the frontline defense against these pathogens. Central to our understanding is the mechanism by which bacteria modify their behavior to circumvent macrophage-mediated clearance, ensuring their persistence and colonization. To successfully evade macrophage-mediated phagocytosis, bacteria must possess an adaptive response mechanism. Two-component systems provide bacteria the agility to navigate diverse environmental challenges, translating external stimuli into cellular adaptive responses. Here, we report that the well-documented histidine kinase, LadS, coupled to a cognate two-component response regulator, PA0034, governs the expression of a vital adhesin called chaperone-usher pathway pilus cupA. The LadS/PA0034 system is susceptible to interference from the reactive oxygen species likely to be produced by macrophages and further lead to a poor adhesive phenotype with scantily cupA pilus, impairing the phagocytosis efficiency of macrophages during acute infection. This dynamic underscores the intriguing interplay: as macrophages deploy reactive oxygen species to combat bacterial invasion, the bacteria recalibrate their exterior to elude these defenses.

IMPORTANCE

The notoriety of Pseudomonas aeruginosa is underscored by its virulence, drug resistance, and elaborate sensor-response network. Yet, the mechanisms by which P. aeruginosa maneuvers to escape phagocytosis during acute infections remain elusive. This study pinpoints a two-component response regulator, PA0034, coupled with the histidine kinase LadS, and responds to macrophage-derived reactive oxygen species. The macrophage-derived reactive oxygen species can impair the LadS/PA0034 system, resulting in reduced expression of cupA pilus in the exterior of P. aeruginosa. Since the cupA pilus is an important adhesin of P. aeruginosa, its deficiency reduces bacterial adhesion and changes their behavior to adopt a planktonic lifestyle, subsequently inhibiting the phagocytosis of macrophages by interfering with bacterial adhesion. Briefly, reactive oxygen species may act as environmental cues for the LadS/PA0034 system. Upon recognition, P. aeruginosa may transition to a poorly adhesive state, efficiently avoiding engulfment by macrophages.

Multimodal evaluation of drug antibacterial activity reveals cinnamaldehyde analog anti-biofilm effects against Haemophilus influenzae

Biofilm formation by the pathobiont Haemophilus influenzae is associated with human nasopharynx colonization, otitis media in children, and chronic respiratory infections in adults suffering from chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD). β-lactam and quinolone antibiotics are commonly used to treat these infections. However, considering the resistance of biofilm-resident bacteria to antibiotic-mediated killing, the use of antibiotics may be insufficient and require being replaced or complemented with novel strategies. Moreover, unlike the standard minimal inhibitory concentration assay used to assess antibacterial activity against planktonic cells, standardization of methods to evaluate anti-biofilm drug activity is limited. In this work, we detail a panel of protocols for systematic analysis of drug antimicrobial effect on bacterial biofilms, customized to evaluate drug effects against H. influenzae biofilms. Testing of two cinnamaldehyde analogs, (E)-trans-2-nonenal and (E)-3-decen-2-one, demonstrated their effectiveness in both H. influenzae inhibition of biofilm formation and eradication or preformed biofilms. Assay complementarity allowed quantifying the dynamics and extent of the inhibitory effects, also observed for ampicillin resistant clinical strains forming biofilms refractory to this antibiotic. Moreover, cinnamaldehyde analog encapsulation into poly(lactic-co-glycolic acid) (PLGA) polymeric nanoparticles allowed drug vehiculization while maintaining efficacy. Overall, we demonstrate the usefulness of cinnamaldehyde analogs against H. influenzae biofilms, present a test panel that can be easily adapted to a wide range of pathogens and drugs, and highlight the benefits of drug nanoencapsulation towards safe controlled release.

Marine-derived bioactive materials as antibiofilm and antivirulence agents

Microbial infections are major human health issues, and, recently, the mortality rate owing to bacterial and fungal infections has been increasing. In addition to intrinsic and extrinsic antimicrobial resistance mechanisms, biofilm formation is a key adaptive resistance mechanism. Several bioactive compounds from marine organisms have been identified for use in biofilm therapy owing to their structural complexity, biocompatibility, and economic viability. In this review, we discuss recent trends in the application of marine natural compounds, marine-bioinspired nanomaterials, and marine polymer conjugates as possible therapeutic agents for controlling biofilms and virulence factors. We also comprehensively discuss the mechanisms underlying biofilm formation and inhibition of virulence factors by marine-derived materials and propose possible applications of novel and effective antibiofilm and antivirulence agents.

A. castellanii and P. aeruginosa mutually exacerbate damage to corneal cells during coinfection

IMPORTANCE

At the National Cheng Kung University Hospital, numerous cases of amoebic keratitis had been identified with concurrent bacterial infections. Among these bacterial coinfections, Pseudomonas aeruginosa accounted for 50% of the reported cases. However, the impact of pathogenic bacteria on amoeba-induced corneal damage remains unclear. In our study, we successfully demonstrated that P. aeruginosa accumulated on the Acanthamoeba castellanii surface and caused more severe corneal damage. We also indicated that the exposure of P. aeruginosa to amoeba-soluble antigens enhanced its adhesion ability, promoted biofilm formation, and led to more severe corneal cell damage. These findings significantly contributed to our understanding of the risk associated with P. aeruginosa coinfection in the progression of amoeba keratitis.

In vitro inhibition of Pseudomonas aeruginosa PAO1 biofilm formation by DZ2002 through regulation of extracellular DNA and alginate production

Introduction

Pseudomonas aeruginosa (P. aeruginosa) is a common pathogen associated with biofilm infections, which can lead to persistent infections. Therefore, there is an urgent need to develop new anti-biofilm drugs. DZ2002 is a reversible inhibitor that targets S-adenosylhomocysteine hydrolase and possesses anti-inflammatory and immune-regulatory activities. However, its anti-biofilm activity has not been reported yet.

Methods and results

Therefore, we investigated the effect of DZ2002 on P. aeruginosa PAO1 biofilm formation by crystal violet staining (CV), real-time quantitative polymerase chain reaction (RT-qPCR) and confocal laser scanning microscopy (CLSM). The results indicated that although DZ2002 didn't affect the growth of planktonic PAO1, it could significantly inhibit the formation of mature biofilms. During the inhibition of biofilm formation by DZ2002, there was a parallel decrease in the synthesis of alginate and the expression level of alginate genes, along with a weakening of swarming motility. However, these results were unrelated to the expression of lasI, lasR, rhII, rhIR. Additionally, we also found that after treatment with DZ2002, the biofilms and extracellular DNA content of PAO1 were significantly reduced. Molecular docking results further confirmed that DZ2002 had a strong binding affinity with the active site of S-adenosylhomocysteine hydrolase (SahH) of PAO1.

Discussion

In summary, our results indicated that DZ2002 may interact with SahH in PAO1, inhibiting the formation of mature biofilms by downregulating alginate synthesis, extracellular DNA production and swarming motility. These findings demonstrate the potential value of DZ2002 in treating biofilm infections associated with P. aeruginosa.

Development and characterization of a spray-dried inhalable ternary combination for the treatment of Pseudomonas aeruginosa biofilm infection in cystic fibrosis

Cystic fibrosis (CF) is an inherited lung disease characterised by the accumulation of thick layers of dried mucus in the lungs which serve as a nidus for chronic infection. Pseudomonas aeruginosa is the predominant cause of chronic lung infection in cystic fibrosis. The dense mucus coupled with biofilm formation hinder antibiotic penetration and prevent them from reaching their target. Mucoactive agents are recommended in the treatment of CF in combination with antibiotics. In spite of the extensive research in developing novel drug combinations for the treatment of lung infection in CF, to our knowledge, there is no study that combines antibiotic, antibiofilm and mucoactive agent in a single inhaled dry powder formulation. In the present study, we investigate the possibility of adding a mucoactive agent to our previously developed ciprofloxacinquercetin (antibiotic-antibiofilm) dry powder for inhalation. Three mucoactive agents, namely mannitol (MAN), N-acetyl-L-cysteine (NAC) and ambroxol hydrochloride (AMB), were investigated for this purpose. The ternary combinations were prepared via spray drying without the addition of excipients. All ternary combinations conserved or improved the antibacterial and biofilm inhibition activities of ciprofloxacin against P. aeruginosa (ATCC 10145). The addition of AMB resulted in an amorphous ternary combination (SD-CQA) with superior physical stability as indicated by DSC and nonambient XRPD. Furthermore, SD-CQA displayed better in vitro aerosolization performance (ED ∼ 71 %; FPF ∼ 49 %) compared to formulations containing MAN and NAC (ED ∼ 64 % and 44 %; FPF ∼ 44 % and 29 %, respectively). In conclusion, a ternary drug combination powder with suitable aerosolization, physical stability and antibacterial/antibiofilm properties was prepared by a single spray drying step.

Machine learning and phylogenetic analysis allow for predicting antibiotic resistance in M. tuberculosis

BACKGROUND

Antimicrobial resistance (AMR) poses a significant global health threat, and an accurate prediction of bacterial resistance patterns is critical for effective treatment and control strategies. In recent years, machine learning (ML) approaches have emerged as powerful tools for analyzing large-scale bacterial AMR data. However, ML methods often ignore evolutionary relationships among bacterial strains, which can greatly impact performance of the ML methods, especially if resistance-associated features are attempted to be detected. Genome-wide association studies (GWAS) methods like linear mixed models accounts for the evolutionary relationships in bacteria, but they uncover only highly significant variants which have already been reported in literature.

RESULTS

In this work, we introduce a novel phylogeny-related parallelism score (PRPS), which measures whether a certain feature is correlated with the population structure of a set of samples. We demonstrate that PRPS can be used, in combination with SVM- and random forest-based models, to reduce the number of features in the analysis, while simultaneously increasing models' performance. We applied our pipeline to publicly available AMR data from PATRIC database for Mycobacterium tuberculosis against six common antibiotics.

CONCLUSIONS

Using our pipeline, we re-discovered known resistance-associated mutations as well as new candidate mutations which can be related to resistance and not previously reported in the literature. We demonstrated that taking into account phylogenetic relationships not only improves the model performance, but also yields more biologically relevant predicted most contributing resistance markers.

Personalized antibiotic selection in periodontal treatment improves clinical and microbiological outputs

Introduction

Periodontitis is a biofilm-mediated disease that is usually treated by non-surgical biofilm elimination with or without antibiotics. Antibiotic treatment in periodontal patients is typically selected empirically or using qPCR or DNA hybridization methods. These approaches are directed towards establishing the levels of different periodontal pathogens in periodontal pockets to infer the antibiotic treatment. However, current methods are costly and do not consider the antibiotic susceptibility of the whole subgingival biofilm.

Methods

In the current manuscript, we have developed a method to culture subgingival samples ex vivo in a fast, label-free impedance-based system where biofilm growth is monitored in real-time under exposure to different antibiotics, producing results in 4 hours. To test its efficacy, we performed a double-blind, randomized clinical trial where patients were treated with an antibiotic either selected by the hybridization method (n=32) or by the one with the best effect in the ex vivo growth system (n=32).

Results

Antibiotic selection was different in over 80% of the cases. Clinical parameters such as periodontal pocket depth, attachment level, and bleeding upon probing improved in both groups. However, dental plaque was significantly reduced only in the group where antibiotics were selected according to the ex vivo growth. In addition, 16S rRNA sequencing showed a larger reduction in periodontal pathogens and a larger increase in health-associated bacteria in the ex vivo growth group.

Discussion

The results of clinical and microbiological parameters, together with the reduced cost and low analysis time, support the use of the impedance system for improved individualized antibiotic selection.

Culture Shock: An Investigation into the Tolerance of Pathogenic Biofilms to Antiseptics in Environments Resembling the Chronic Wound Milieu

Credible assessment methods must be applied to evaluate antiseptics' in vitro activity reliably. Studies indicate that the medium for biofilm culturing should resemble the conditions present at the site of infection. We cultured S. aureus, S. epidermidis, P. aeruginosa, C. albicans, and E. coli biofilms in IVWM (In Vitro Wound Milieu)-the medium reflecting wound milieu-and were compared to the ones cultured in the laboratory microbiological Mueller-Hinton (MH) medium. We analyzed and compared crucial biofilm characteristics and treated microbes with polyhexamethylene biguanide hydrochloride (PHMB), povidone-iodine (PVP-I), and super-oxidized solution with hypochlorites (SOHs). Biofilm biomass of S. aureus and S. epidermidis was higher in IVWM than in MH medium. Microbes cultured in IVWM exhibited greater metabolic activity and thickness than in MH medium. Biofilm of the majority of microbial species was more resistant to PHMB and PVP-I in the IVWM than in the MH medium. P. aeruginosa displayed a two-fold lower MBEC value of PHMB in the IVWM than in the MH medium. PHMB was more effective in the IVWM than in the MH medium against S. aureus biofilm cultured on a biocellulose carrier (instead of polystyrene). The applied improvement of the standard in vitro methodology allows us to predict the effects of treatment of non-healing wounds with specific antiseptics.

Restoring Colistin Sensitivity and Combating Biofilm Formation: Synergistic Effects of Colistin and Usnic Acid against Colistin-Resistant Enterobacteriaceae

Colistin (COL), the last line of defense in clinical medicine, is an important therapeutic option against multidrug-resistant Gram-negative bacteria. In this context, the emergence of colistin-resistant (COL-R) bacteria mediated by broad-spectrum efflux pumps, mobile genetic elements, and biofilm formation poses a significant public health concern. In response to this challenge, a novel approach of combining COL with usnic acid (UA) has been proposed in this study. UA is a secondary metabolite derived from lichens and is well-known for its anti-inflammatory properties. This study aimed to investigate the synergistic effects of UA and COL against COL-R Enterobacteriaceae both in vitro and in vivo. The exceptional synergistic antibacterial activity exhibited by the combination of COL and UA was demonstrated by performing a comprehensive set of assays, including the checkerboard assay, time-dependent killing assay, and Live/Dead bacterial cell viability assay. Furthermore, crystal violet staining and scanning electron microscopy assays revealed the inhibitory effect of this combination on the biofilm formation. Mechanistically, the combination of UA and COL exacerbated cell membrane rupture, induced DNA damage, and generated a significant amount of reactive oxygen species, which ultimately resulted in bacterial cell death. In addition, erythrocyte hemolysis and cell viability tests confirmed the biocompatibility of the combination. The evaluation of the COL/UA combination in vivo using Galleria mellonella larvae and a mouse infection model showed a significant improvement in the survival rate of the infected larvae as well as a reduction in the bacterial load in the mouse thigh muscle. These findings, for the first time, provide strong evidence for the potential application of COL/UA as an effective alternative therapeutic option to combat infections caused by COL-R Enterobacteriaceae strains.

Real-time monitoring of biofilm growth identifies andrographolide as a potent antifungal compound eradicating Candida biofilms

Candida species cause life-threatening infections with high morbidity and mortality rates and their resistance to conventional therapy is closely linked to biofilm formation. Thus, the development of new approaches to study Candida biofilms and the identification of novel therapeutic strategies could yield improved clinical outcomes. In the current study, we have set up an impedance-based in vitro system to study Candida spp. biofilms in real-time and to evaluate their sensitivity to two conventional antifungal groups used in clinical practice - azoles and echinocandins. Both fluconazole and voriconazole were unable to inhibit biofilm formation in most strains tested, while echinocandins showed biofilm inhibitory capacity at relatively low concentrations (starting from 0.625 mg/L). However, assays performed on 24 h Candida albicans and C. glabrata biofilms revealed that micafungin and caspofungin failed to eradicate mature biofilms at all tested concentrations, evidencing that once formed, Candida spp. biofilms are extremely difficult to eliminate using currently available antifungals. We then evaluated the antifungal and anti-biofilm effect of andrographolide, a natural compound isolated from the plant Andrographis paniculata with known antibiofilm activity on Gram-positive and Gram-negative bacteria. Optical density measures, impedance evaluation, CFU counts, and electron microscopy data showed that andrographolide strongly inhibits planktonic Candida spp. growth and halts Candida spp. biofilm formation in a dose-dependent manner in all tested strains. Moreover, andrographolide was capable of eliminating mature biofilms and viable cell numbers by up to 99.9% in the C. albicans and C. glabrata strains tested, suggesting its potential as a new approach to treat multi-resistant Candida spp. biofilm-related infections.

(P)ppGpp synthetase Rsh participates in rifampicin tolerance of persister cells in Brucella abortus in vitro

Brucella abortus is facultative intracellular pathogen that causes chronic persistent infections and results in abortion and infertility in food animals. Recurrent infections can be one of the results of persister cells formation that transiently displays phenotypic tolerance to high dose of antibiotics treatment. We examined persister cells formation of B. abortus strain A19 in stationary phase and investigated a potential role for the (p)ppGpp synthetase Rsh in this process. We found that B. abortus stationary phase cells can produce higher levels of multi-drugs tolerant persister cells in vitro under high dose of antibiotics (20 × MIC) exposure than do exponential phase cells. Persister cell formation was also induced with environmental stressors pH 4.5, 0.01 M PBS (pH7.0), 2% NaCl and 25 °C, upon exposure to ampicillin, enrofloxacin and rifampicin. Persister cells were not formed following exposure to 1 mM H2O2. The numbers of persister cells were significantly increased following uptake of B. abortus stationary phase cells by RAW264.7 macrophages in contrast with cultures in TSB liquid medium. Environmental stressors to B. abortus significantly increased expression of rsh mRNA level. The rsh null mutant (Δrsh) formed significantly fewer persister cells than the complemented (CΔrsh) and wildtype (WT) strains under high dose of rifampicin in vitro. These data for the first time demonstrate that B. abortus can produce multi-drug tolerant persister cells in stationary phase. The (p)ppGpp synthetase Rsh is necessary for persister cell formation in B. abortus in the presence of rifampicin. On this basis, a new understanding of the recurrent infections of Brucella was advanced, thus provided a new basis for revelation of pathogenic mechanism of the chronic persistent infection in Brucella.

Recent Advances in Bacterial Persistence Mechanisms

The recurrence of bacterial infectious diseases is closely associated with bacterial persisters. This subpopulation of bacteria can escape antibiotic treatment by entering a metabolic status of low activity through various mechanisms, for example, biofilm, toxin-antitoxin modules, the stringent response, and the SOS response. Correspondingly, multiple new treatments are being developed. However, due to their spontaneous low abundance in populations and the lack of research on in vivo interactions between persisters and the host's immune system, microfluidics, high-throughput sequencing, and microscopy techniques are combined innovatively to explore the mechanisms of persister formation and maintenance at the single-cell level. Here, we outline the main mechanisms of persister formation, and describe the cutting-edge technology for further research. Despite the significant progress regarding study techniques, some challenges remain to be tackled.

Genome Analysis of Pseudomonas aeruginosa Strains from Chronically Infected Patients with High Levels of Persister Formation

The appearance of persister cells with low metabolic rates are key factors leading to antibiotic treatment failure. Such persisters are multidrug tolerant and play a key role in the recalcitrance of biofilm-based chronic infections. Here, we present the genomic analyses of three distinct Pseudomonas aeruginosa Egyptian persister-isolates recovered from chronic human infections. To calculate the persister frequencies, viable counts were determined before and after treatment with levofloxacin. The susceptibilities of isolates to different antibiotics were determined using the agar-dilution method. To determine their recalcitrance, the levofloxacin persisters were further challenged with lethal concentrations of meropenem, tobramycin, or colistin. Furthermore, the biofilm formation of the persister strains was estimated phenotypically, and they were reported to be strong biofilm-forming strains. The genotypic characterization of the persisters was performed using whole genome sequencing (WGS) followed by phylogenetic analysis and resistome profiling. Interestingly, out of the thirty-eight clinical isolates, three isolates (8%) demonstrated a persister phenotype. The three levofloxacin-persister isolates were tested for their susceptibility to selected antibiotics; all of the tested isolates were multidrug resistant (MDR). Additionally, the P. aeruginosa persisters were capable of surviving over 24 h and were not eradicated after exposure to 100X-MIC of levofloxacin. WGS for the three persisters revealed a smaller genome size compared to PAO1-genome. Resistome profiling indicated the presence of a broad collection of antibiotic-resistance genes, including genes encoding for antibiotic-modifying enzymes and efflux pump. Phylogenetic analysis indicated that the persister isolates belong to a distinct clade rather than the deposited P. aeruginosa strains in the GenBank. Conclusively, the persister isolates in our study are MDR and form a highly strong biofilm. WGS revealed a smaller genome that belongs to a distinct clade.

Evaluation of Bacteria in a Novel In Vitro Biofilm Model of Penile Prosthesis

BACKGROUND

Delayed infection, thought to be due to gradual biofilm formation, remains a feared complication after inflatable penile prosthesis (IPP) insertion. Understanding and preventing biofilm formation is necessary to prevent infections.

AIM

To develop an in vitro model and compare growth of biofilm by different bacteria on IPPs and evaluate the anti-infective efficacy of the Coloplast Titan and AMS 700 InhibiZone.

METHODS

Sterile IPPs (Coloplast) were cut into rings and incubated with S. epidermidis, S. aureus, P. aeruginosa, A. baumannii, or K. pneumoniae cultures in tryptic soy broth (TSB) (4 hour) to ensure adequate bacteria attachment, and then in only TSB (120 hours) to allow for biofilm formation. Rings were fixed with ethanol and biofilm measured by spectrophotometer (OD570) after crystal violet staining. This methodology was repeated for S. epidermidis and P. aeruginosa with Coloplast rings dipped in 10 ml of a 10 mg/ml Rifampin, 1 mg/ml Gentamicin, and deionized water solution and undipped AMS InhibiZone rings. Crystal violet assay (OD570) was repeated after incubation within bacteria (2 hour), and then only TSB (120 hours).

OUTCOMES

The primary outcome of the study was OD570 readings, indirectly measuring biofilm mass on implant rings.

RESULTS

S. epidermidis, S. aureus, A. baumannii, P. aeruginosa, and K. pneumoniae all formed significant biofilm. P. aeruginosa showed the strongest predilection to grow biofilm on IPPs. P. aeruginosa also formed significant biofilm on antibiotic-treated Coloplast and AMS rings, while S. epidermidis was inhibited. No significant difference was found in biofilm inhibition between the implants.

CLINICAL TRANSLATION

Our findings suggest gram-negative bacteria may form biofilm more proficiently and quickly on IPPs than gram-positive organisms. Commonly used antibiotic treatments on IPPs may be effective against S. epidermidis but not against P. aeruginosa biofilm formation.

STRENGTHS & LIMITATIONS

This is the first study comparing biofilm formation by different bacteria organisms on IPPs and the inhibitive ability of Coloplast and AMS implants against biofilm formation. Clinical data on organisms responsible for infected IPPs is needed to determine the clinical relevance of our findings.

CONCLUSION

Our novel in vitro model of biofilm formation of IPPs evaluated the effect of a gentamicin/rifampin antibiotic dip on Coloplast Titan implants and the anti-infective capacity of the minocycline/rifampin precoated AMS 700 InhibiZone against S. epidermidis and P. aeruginosa. P. aeruginosa was able to grow on both antibiotic-treated implants, with no significant difference, and should continue to be a specific target of investigation to reduce delayed post-operative IPP infections. Narasimman M, Ory J, Bartra SS, et al. Evaluation of Bacteria in a Novel In Vitro Biofilm Model of Penile Prosthesis. J Sex Med 2022;19:1024-1031.

Evolution of Bacterial Persistence to Antibiotics during a 50,000-Generation Experiment in an Antibiotic-Free Environment

Failure of antibiotic therapies causes > 700,000 deaths yearly and involves both bacterial resistance and persistence. Persistence results in the relapse of infections by producing a tiny fraction of pathogen survivors that stay dormant during antibiotic exposure. From an evolutionary perspective, persistence is either a ‘bet-hedging strategy’ that helps to cope with stochastically changing environments or an unavoidable minimal rate of ‘cellular errors’ that lock the cells in a low activity state. Here, we analyzed the evolution of persistence over 50,000 bacterial generations in a stable environment by improving a published method that estimates the number of persister cells based on the growth of the reviving population. Our results challenged our understanding of the factors underlying persistence evolution. In one case, we observed a substantial decrease in persistence proportion, suggesting that the naturally observed persistence level is not an unavoidable minimal rate of ‘cellular errors’. However, although there was no obvious environmental stochasticity, in 11 of the 12 investigated populations, the persistence level was maintained during 50,000 bacterial generations.