Staphopains Modulate Staphylococcus aureus Biofilm Integrity

Staphylococcus aureus is a known cause of chronic biofilm infections that can reside on medical implants or host tissue. Recent studies have demonstrated an important role for proteinaceous material in the biofilm structure. The S. aureus genome encodes many secreted proteases, and there is growing evidence that these enzymes have self-cleavage properties that alter biofilm integrity. However, the specific contribution of each protease and mechanism of biofilm modulation is not clear. To address this issue, we utilized a sigma factor B (ΔsigB) mutant where protease activity results in a biofilm-negative phenotype, thereby creating a condition where the protease(s) responsible for the phenotype could be identified. Using a plasma-coated microtiter assay, biofilm formation was restored to the ΔsigB mutant through the addition of the cysteine protease inhibitor E-64 or by using Staphostatin inhibitors that specifically target the extracellular cysteine proteases SspB and ScpA (called Staphopains). Through construction of gene deletion mutants, we determined that an sspB scpA double mutant restored ΔsigB biofilm formation, and this recovery could be replicated in plasma-coated flow cell biofilms. Staphopain levels were also found to be decreased under biofilm-forming conditions, possibly allowing biofilm establishment. The treatment of S. aureus biofilms with purified SspB or ScpA enzyme inhibited their formation, and ScpA was also able to disperse an established biofilm. The antibiofilm properties of ScpA were conserved across S. aureus strain lineages. These findings suggest an underappreciated role of the SspB and ScpA cysteine proteases in modulating S. aureus biofilm architecture.     

An update on recent developments in the prevention and treatment of Staphylococcus aureus biofilms

Staphylococcus aureus (S. aureus) readily forms biofilms on prosthetic devices such as the pacemakers, heart valves, orthopaedic implants, and indwelling catheters. Its biofilms are recalcitrant to antibiotic therapy and pose a serious burden in the healthcare setting as they drastically increase the treatment cost and morbidity of the patient. Prevention and treatment of staphylococcal biofilms has therefore been an area of active research for the past two decades. While catheters coated with different antiseptics and antibiotics capable of preventing S. aureus biofilm formation have been developed, an effective therapy for the dispersal and treatment of established staphylococcal biofilms is not yet available. Hence, many studies have focused on developing novel therapeutic strategies that can tackle established S. aureus biofilm associated infections. This has led to the identification of different phytochemicals (e.g., tannic acid, ellagic acid, xanthohumol etc), enzymes (e.g., Dnases, lysostaphin, α-amylase, hyaluronidase and proteases etc.), sulfahydrl compounds (e.g., dithiothreitol, 2-mercaptoethanol), nanoparticles (e.g., gold, silver, iron, copper and selenium), phage cocktails, antibodies and metal chelators. Apart from the conventional techniques, the therapeutic effects of ultra sound, shock waves and photodynamic therapy for treating S. aureus biofilms are also being investigated. Clinical validation of these studies will equip the medical field with alternate preventive and treatment methods against staphylococcal biofilm infections. This review provides recent updates on the preventive and therapeutic strategies explored to eradicate staphylococcal biofilm formation and related infections.     

Mechanistic insights into response of Staphylococcus aureus to bioelectric effect on polypyrrole/chitosan film

Treatment of biofilm-related infections in orthopedics remains a serious clinical challenge. It is known that an electric current can significantly enhance the potency of some antibiotics against biofilms (bioelectric effect) but the uncertainty of the mechanisms and the electrolytic cell-like system used in previous studies limit its applications. Herein, the behavior of Staphylococcus aureus (S. aureus) on an electrically conductive polypyrrole/chitosan film upon passage of a direct current (DC) through the film was investigated in the absence and presence of gentamicin. The killing efficacy of the bacteria within the biofilm by gentamicin was greatly enhanced by the DC treatment. From an analysis of the gene expression by the biofilm bacteria after treatment with gentamicin, DC and their combination, it is postulated that the promotion of bacterial autolysis by DC treatment is responsible for the enhanced susceptibility of biofilm S. aureus to gentamicin. This postulate is supported by an increase in the amount of extracellular deoxyribonucleic acid and adenosine triphosphate, and the appearance of disrupted bacterial cells in the biofilm after DC treatment. These findings provide a new insight into the interaction between DC and bacteria, and offer potential benefits for the treatment of infections in orthopedics.     

Biofilm formation of Bdellovibrio bacteriovorus host-independent derivatives

Bdellovibrios are Gram-negative predatory bacteria which are ubiquitous to many environmental niches, including natural biofilms. In this study, host-independent (HI) variants of Bdellovibrio bacteriovorus 109J were isolated. Predation assays and genetic analysis confirmed that the selected HI variants are derivatives of B. bacteriovorus. When grown in microtiter plates, HI variants were able to form tenacious biofilms on the surface of the wells. HI biofilm formation on different surfaces, media and temperatures was examined. HI biofilm development was seen on all of the examined surfaces, with the most robust biofilm developing at 22 °C and in media supplemented with yeast extract. Biofilm detachment experiments revealed that the HI cells are firmly attached to the surface of the wells and are not easily removed by physical and chemical treatments. Treating the biofilm with proteinase K and DNase-I caused rapid detachment of the biofilm as well as inhibition of biofilm formation, suggesting that DNA and proteins are major components of the HI biofilm extracellular matrix. Our data suggest that under conditions that might favor the development of HI variants, such as a rich nutrient environment, Bdellovibrio facultative prey cells are capable of attaching to abiotic surfaces and forming biofilms.     

Vaccination with SesC Decreases Staphylococcus epidermidis Biofilm Formation

The increased use of medical implants has resulted in a concomitant rise in device-related infections. The majority of these infections are caused by Staphylococcus epidermidis biofilms. Immunoprophylaxis and immunotherapy targeting in vivo-expressed, biofilm-associated, bacterial cell surface-exposed proteins are promising new approaches to prevent and treat biofilm-related infections, respectively. Using an in silico procedure, we identified 64 proteins that are predicted to be S. epidermidis surface exposed (Ses), of which 36 were annotated as (conserved) hypothetical. Of these 36 proteins, 5 proteins-3 LPXTG motif-containing proteins (SesL, SesB, and SesC) and 2 of the largest ABC transporters (SesK and SesM)-were selected for evaluation as vaccine candidates. This choice was based on protein size, number of antigenic determinants, or the established role in S. epidermidis biofilm formation of the protein family to which the candidate protein belongs. Anti-SesC antibodies exhibited the greatest inhibitory effect on S. epidermidis biofilm formation in vitro and on colonization and infection in a mouse jugular vein catheter infection model that includes biofilms and organ infections. Active vaccination with a recombinant truncated SesC inhibited S. epidermidis biofilm formation in a rat model of subcutaneous foreign body infection. Antibodies to SesC were shown to be opsonic by an in vitro opsonophagocytosis assay. We conclude that SesC is a promising target for antibody mediated strategies against S. epidermidis biofilm formation.     

Clearance of Pseudomonas aeruginosa Foreign-Body Biofilm Infections through Reduction of the Cyclic Di-GMP Level in the Bacteria

Opportunistic pathogenic bacteria can engage in biofilm-based infections that evade immune responses and develop into chronic conditions. Because conventional antimicrobials cannot efficiently eradicate biofilms, there is an urgent need to develop alternative measures to combat biofilm infections. It has recently been established that the secondary messenger cyclic diguanosine monophosphate (c-di-GMP) functions as a positive regulator of biofilm formation in several different bacteria. In the present study we investigated whether manipulation of the c-di-GMP level in bacteria potentially can be used for biofilm control in vivo. We constructed a Pseudomonas aeruginosa strain in which a reduction in the c-di-GMP level can be achieved via induction of the Escherichia coli YhjH c-di-GMP phosphodiesterase. Initial experiments showed that induction of yhjH expression led to dispersal of the majority of the bacteria in in vitro-grown P. aeruginosa biofilms. Subsequently, we demonstrated that P. aeruginosa biofilms growing on silicone implants, located in the peritoneal cavity of mice, dispersed after induction of the YhjH protein. Bacteria accumulated temporarily in the spleen after induction of biofilm dispersal, but the mice tolerated the dispersed bacteria well. The present work provides proof of the concept that modulation of the c-di-GMP level in bacteria is a viable strategy for biofilm control.     

Biofilm formation by ST17 and ST19 strains of Streptococcus agalactiae

Bacterial biofilms are an important virulence factor with a vital role in evasion from the host immune system, colonization and infection. The aim of the present study was to evaluate in vitro the effects of three environmental factors (H⁺, glucose and human plasma) in biofilm formation, by carrier and invasive Streptococcus agalactiae strains of ST17 and ST19 sequence types, including DNase producers and non-producers. Bacteria ability to assemble biofilms was classified based on crystal violet assay. Biofilm formation was also monitored by scanning electron microscopy. Depending on the growth medium used, each bacterial isolate could fit in different biofilm production categories. Our data showed that optimal conditions for S. agalactiae biofilm assembly were reached after 48 h incubation at pH 7.6 in the presence of glucose and inactivated human plasma. In the presence of inactivated human plasma, the biofilm biomass of ST19 strains experienced a higher increase than ST17 strains. The composition of the extracellular polymeric matrix of the three strongest biofilm producers (all from ST17) was accessed by enzymatic digestion of mature biofilms and proteins were shown to be the predominant component. The detailed identification of the extracellular protein components should contribute to the development of new therapeutic strategies to fight S. agalactiae infections.     

High reduction of staphylococcal biofilm by aqueous extract from marine sponge-isolated Enterobacter sp.

Staphylococcus aureus and Staphylococcus epidermidis are among the most important bacterial species responsible for biofilm formation on indwelling medical devices, including orthopaedic implants. The increasing resistance to antimicrobials, partly attributed to the ability to form biofilms, is a challenge for the development of new antimicrobial agents. In this study, the cell-free supernatant obtained from sponge-associated Enterobacter strain 84.3 culture inhibited biofilm formation (>65%) and dissociated mature biofilm (>85%) formed by S. aureus and S. epidermidis strains. The culture supernatant was subjected to solvent partitioning and the aqueous extract presented a concentration-dependent antibiofilm activity for each strain with a minimum biofilm eradication concentration (MBEC) ranging from 16 to 256 μg/mL. The effect of the aqueous extract on mature S. aureus biofilm was analyzed by confocal scanning laser microscopy, showing a significant reduction of the biofilm layer as well as diminished interactions among the cells. This extract is not toxic for mammalian cells (L929 cell line). Studies targeting substances with antibiofilm activity gained significant attention in recent years due to difficult-to-treat biofilm infections. Here, sponge-associated Enterobacter 84.3 proved to be a source of substances capable of eradicating staphylococcal biofilm, with potential medical use in the future.     

Inhibition of Staphylococcus epidermidis Biofilm Formation by Rabbit Polyclonal Antibodies against the SesC Protein

Several well-studied proteins with defined roles in Staphylococcus epidermidis biofilm formation are LPXTG motif-containing proteins. Here, we investigate the possible use of the LPXTG motif-containing protein SesC (S. epidermidis surface protein C; accession no. {"type":"entrez-protein","attrs":{"text":"NP_765787","term_id":"27469150","term_text":"NP_765787"}}NP_765787) as a target for antibodies to prevent biofilm formation. In vitro and in a in vivo rat model of catheter infection, gene and protein expression analysis showed that SesC is expressed more strongly in biofilm-associated cells than in planktonic cells and is expressed particularly during the late phase of in vivo biofilm formation. Polyclonal rabbit antibodies raised against SesC reduced the fibrinogen-binding ability of S. epidermidis RP62A and Staphylococcus aureus RN4220 transformants expressing SesC, inhibited in vitro biofilm formation by S. epidermidis strains 10b and 1457, and significantly reduced the numbers of bacteria in a 1-day-old in vivo biofilm (P < 0.001, one-way analysis of variance). Our findings revealed that SesC is a promising target for prevention and treatment of S. epidermidis biofilms because it affects both the primary attachment and biofilm accumulation phases. The precise role of SesC in biofilm formation remains to be identified.There has been substantial interest in Staphylococcus epidermidis in recent years because it is the most important cause of foreign-body infections (27, 34). Biofilm formation is a key factor in this process and is considered the most important virulence factor of S. epidermidis (6).S. epidermidis biofilm formation is a complex, multifactorial process, involving different factors that play roles at different stages in biofilm formation. Several of the genes that have been found to play important roles in biofilm formation by S. epidermidis (for a review, see reference 21) encode LPXTG motif-containing proteins (Aap, Bhp, SdrF, and SdrG) (1, 8, 9, 15). Recently, Söderquist reported that SesI, another LPXTG protein, was present in “about one-half” of the S. epidermidis isolates causing postoperative infection following cardiac surgery and might be a bacterial adherence factor (25).In publicly available genomes of S. epidermidis strains RP62A (11) and ATCC 12228 (37), 11 and 10 genes encoding LPXTG proteins, respectively, have been identified (2), including genes encoding the proteins mentioned above. Except for the five LPXTG proteins mentioned above, the roles of these LPXTG proteins have not been studied yet. In the present study we examined the S. epidermidis LPXTG protein SesC as a potential target for vaccination against S. epidermidis biofilms.Bowden et al. (2) reported that the sesC gene was present in all of the 116 clinical isolates of S. epidermidis that they investigated, indicating that it might be an essential gene. Yao et al. (36), however, reported that sesC was absent in some S. epidermidis isolates, particularly isolates from the skin of healthy individuals (9 of 20 isolates).SesC is predicted to encode a 676-amino-acid (aa) protein with a predicted molecular mass of 75 kDa. The cytoplasmic precursor of SesC contains a 35-aa N-terminal signal peptide (predicted using the SignalP server at http://www.cbs.dtu.dk/services/SignalP/), a 37-aa C-terminal LPXTG sorting signal, and a large extracellular domain. The N-terminal signal is required for sec-dependent secretion and is cleaved by signal peptidase. The C-terminal signal is needed for cleavage between the threonine and the glycine of the LPXTG motif and for attachment to peptidoglycan by sortase.The presence of mature SesC (∼68 kDa) in the cell wall fraction of S. epidermidis RP62A in the exponential and stationary phases of growth was shown using a Western immunoblotting technique (2). All of the homologues of SesC in publicly available protein data banks had less than 70% sequence identity to SesC, and all of the homologues with identities higher than 26% were hypothetical proteins with unknown structures and functions. The closest homologue of SesC with a known function is a 341-aa fragment of clumping factor A (ClfA) (26.6% identity and 65.1% similarity in a 335-aa overlap). ClfA is a fibrinogen (Fg)-binding microbial surface component recognizing adhesive matrix molecules (MSCRAMM) of Staphylococcus aureus. However, the putative Fg-binding site of ClfA is located outside the similarity region.Targeting specific staphylococcal biofilm-associated factors is an alternative to treatment of staphylococcal infections with antibiotics (34). Antibodies against extracellular macromolecules and surface binding proteins essential for cell-surface and cell-cell interaction and adhesion, such as polysaccharide intracellular adhesin (PIA), teichoic acids, Fbe, and Aap, have been shown to prevent biofilm formation without killing the bacteria (19, 22, 26, 35).In this study we demonstrate that SesC is highly expressed in biofilm-associated cells and we present data showing that it is a potential target for preventing S. epidermidis biofilm formation and for treating established mature biofilms with anti-SesC antibodies.     

Nosocomial pathogen biofilms on biomaterials: Different growth medium conditions and components of biofilms produced in vitro

Background/Purpose (s)Nosocomial pathogens can develop biofilms on hospital surfaces and medical devices; however, few studies have focused on the evaluation of mono-and dual-species biofilms developed by nosocomial pathogens under different growth conditions.MethodsThis study investigated biofilm development by nosocomial pathogens (Acinetobacter baumannii, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) on biomaterials in different culture media and their components of the extracellular matrix biofilm.ResultsThe mono-species biofilms showed cell densities from 7.50 to 9.27 Log₁₀ CFU/cm² on natural rubber latex type I (NLTI) and from 7.58 to 8.79 Log₁₀ CFU/cm² on stainless steel (SS). Dual-species biofilms consisted of S. aureus + P. aeruginosa (7.87–8.27 Log₁₀ CFU/cm² in TSBP and TSBME onto SS; p < 0.05), E. coli + P. aeruginosa (8.32–8.86 Log₁₀ CFU/cm² in TSBME onto SS and TSBP onto NLTI; p < 0.05), and S. aureus + E. coli (7.82 Log₁₀ CFU/cm² in TSBME onto SS; p < 0.05). Furthermore, biofilm detachment after proteinase K treatment was 5.54–32.81% compared to 7.95–24.15% after DNase I treatment in the mono-dual species biofilm matrix. Epifluorescence microscopy and scanning electron microscopy (SEM) enabled visualizing the bacteria and extracellular polymeric substances of biofilms on SS and NLTI.ConclusionNosocomial pathogens can develop biofilms on biomaterials. Mono-species biofilms of Gram-negative bacteria showed lower densities than dual-species biofilms in TSBME and TSBP. Additionally, dual-species biofilms showed a higher concentration of proteins and eDNA in the extracellular matrix.     

The Immunomodulatory Activity of Staphylococcus aureus Products Derived from Biofilm and Planktonic Cultures

Biofilms are probably one of the most common structures formed by microorganisms in various environments. The higher resistance of such microbial communities to stress conditions, including antibiotics and host immune response, is recently extensively studied. However, the weak activity of phagocytic cells against microbial biofilm is not yet fully understood and explained. The aim of this study was: (1) a qualitative and quantitative comparison of cell components/products released from Staphylococcus aureus biofilm or planktonic cultures, (2) evaluation of the influence of such cell components/products on murine leukocytes secretory function. For this, mouse peritoneal leukocytes were stimulated with biofilm or planktonic staphylococcal cultures or their acellular filtrates, and then the production of cytokines (TNF-α, IL-6, IL-10, MCP-1 and MIP-1α), hemolytic activity and staphylokinase (SAK) production was determined. It was found that similar staphylococcal components/products possessing the immunomodulatory properties, were present in both, biofilm and planktonic filtrates. Moreover, these compounds were similarly active in the stimulation of TNF-α and MCP-1 release from leukocytes. The hemolytic activity and SAK release by planktonic and biofilm cultures were also comparable. What is interesting, stronger stimulatory activity of biofilm-derived components/products of clinical S. aureus strains in the case of MIP-1α, IL-6 and IL-10 was noticed. On the other hand, taking into consideration the reference strains, MIP-1α production was enhanced by “planktonic filtrates”. Thus, in our study it was proved, first of all, that biofilm is not a structure fully separated from the external environment. Second, the influence of these S. aureus constituents/metabolites on leukocytes seems to be more strain-dependent than culture phenotype-dependent. The lack of one common profile of biofilm and planktonic S. aureus cultures/filtrates biological activity indicates that the disturbances in cytokines’ production could not be the only reason for the so-called “frustrated phagocytosis”, connected with enhanced biofilm resistance.     

The role of biofilms in persistent infections and factors involved in ica-independent biofilm development and gene regulation in Staphylococcus aureus

Staphylococcus aureus biofilms represent a unique micro-environment that directly contribute to the bacterial fitness within hospital settings. The accumulation of this structure on implanted medical devices has frequently caused the development of persistent and chronic S. aureus-associated infections, which represent an important social and economic burden worldwide. ica-independent biofilms are composed of an assortment of bacterial products and modulated by a multifaceted and overlapping regulatory network; therefore, biofilm composition can vary among S. aureus strains. In the microniches formed by biofilms–produced by a number of bacterial species and composed by different structural components–drug refractory cell subpopulations with distinct physiological characteristics can emerge and result in therapeutic failures in patients with recalcitrant bacterial infections. In this review, we highlight the importance of biofilms in the development of persistence and chronicity in some S. aureus diseases, the main molecules associated with ica-independent biofilm development and the regulatory mechanisms that modulate ica-independent biofilm production, accumulation, and dispersion.     

Important Contribution of the Novel Locus comEB to Extracellular DNA-Dependent Staphylococcus lugdunensis Biofilm Formation

The coagulase-negative species Staphylococcus lugdunensis is an emerging cause of serious and potentially life-threatening infections, such as infective endocarditis. The pathogenesis of these infections is characterized by the ability of S. lugdunensis to form biofilms on either biotic or abiotic surfaces. To elucidate the genetic basis of biofilm formation in S. lugdunensis, we performed transposon (Tn917) mutagenesis. One mutant had a significantly reduced biofilm-forming capacity and carried a Tn917 insertion within the competence gene comEB. Site-directed mutagenesis and subsequent complementation with a functional copy of comEB verified the importance of comEB in biofilm formation. In several bacterial species, natural competence stimulates DNA release via lysis-dependent or -independent mechanisms. Extracellular DNA (eDNA) has been demonstrated to be an important structural component of many bacterial biofilms. Therefore, we quantified the eDNA in the biofilms and found diminished eDNA amounts in the comEB mutant biofilm. High-resolution images and three-dimensional data obtained via confocal laser scanning microscopy (CSLM) visualized the impact of the comEB mutation on biofilm integrity. The comEB mutant did not show reduced expression of autolysin genes, decreased autolytic activities, or increased cell viability, suggesting a cell lysis-independent mechanism of DNA release. Furthermore, reduced amounts of eDNA in the comEB mutant biofilms did not result from elevated levels or activity of the S. lugdunensis thermonuclease NucI. In conclusion, we defined here, for the first time, a role for the competence gene comEB in staphylococcal biofilm formation. Our findings indicate that comEB stimulates biofilm formation via a lysis-independent mechanism of DNA release.     

Host Intestinal Signal-Promoted Biofilm Dispersal Induces Vibrio cholerae Colonization

Vibrio cholerae causes human infection through ingestion of contaminated food and water, leading to the devastating diarrheal disease cholera. V. cholerae forms matrix-encased aggregates, known as biofilms, in the native aquatic environment. While the formation of V. cholerae biofilms has been well studied, little is known about the dispersal from biofilms, particularly upon entry into the host. In this study, we found that the exposure of mature biofilms to physiologic levels of the bile salt taurocholate, a host signal for the virulence gene induction of V. cholerae, induces an increase in the number of detached cells with a concomitant decrease in biofilm mass. Scanning electron microscopy micrographs of biofilms exposed to taurocholate revealed an altered, perhaps degraded, appearance of the biofilm matrix. The inhibition of protein synthesis did not alter rates of detachment, suggesting that V. cholerae undergoes a passive dispersal. Cell-free media from taurocholate-exposed biofilms contains a larger amount of free polysaccharide, suggesting an abiotic degradation of biofilm matrix by taurocholate. Furthermore, we found that V. cholerae is only able to induce virulence in response to taurocholate after exit from the biofilm. Thus, we propose a model in which V. cholerae ingested as a biofilm has coopted the host-derived bile salt signal to detach from the biofilm and go on to activate virulence.     

Biofilm Formation Avoids Complement Immunity and Phagocytosis of Streptococcus pneumoniae

Streptococcus pneumoniae is a frequent member of the microbiota of the human nasopharynx. Colonization of the nasopharyngeal tract is a first and necessary step in the infectious process and often involves the formation of sessile microbial communities by this human pathogen. The ability to grow and persist as biofilms is an advantage for many microorganisms, because biofilm-grown bacteria show reduced susceptibility to antimicrobial agents and hinder recognition by the immune system. The extent of host protection against biofilm-related pneumococcal disease has not been determined yet. Using pneumococcal strains growing as planktonic cultures or as biofilms, we have investigated the recognition of S. pneumoniae by the complement system and its interactions with human neutrophils. Deposition of C3b, the key complement component, was impaired on S. pneumoniae biofilms. In addition, binding of C-reactive protein and the complement component C1q to the pneumococcal surface was reduced in biofilm bacteria, demonstrating that pneumococcal biofilms avoid the activation of the classical complement pathway. In addition, recruitment of factor H, the downregulator of the alternative pathway, was enhanced by S. pneumoniae growing as biofilms. Our results also show that biofilm formation diverts the alternative complement pathway activation by a PspC-mediated mechanism. Furthermore, phagocytosis of pneumococcal biofilms was also impaired. The present study confirms that biofilm formation in S. pneumoniae is an efficient means of evading both the classical and the PspC-dependent alternative complement pathways the host immune system.     

肺炎克雷伯菌生物膜相关研究进展

肺炎克雷伯菌(Klebsiella pneumoniae)是临床常见的院内感染致病菌,常引起泌尿系统、呼吸系统以及血流感染等。近年来,肺炎克雷伯菌生物膜引起的慢性感染日益得到重视,对肺炎克雷伯菌生物膜的研究也越来越多。为了适应周围环境,肺炎克雷伯菌会形成生物膜(biofilm),这是一种相对于浮游细菌的生存方式,生物膜由细菌及其自身分泌的代谢产物(胞外多糖、蛋白质、胞外DNA、脂质等)组成。生物膜状态下的肺炎克雷伯菌耐药性极强,容易逃避机体的免疫攻击,难以彻底清除,使临床抗感染变得更加棘手。本文就生物膜形成过程、生物膜状态细菌的耐药机制、生物膜测定方法以及生物膜防治作简要综述。