Biofilm Matrix Formation in Human: Clinical Significance, Diagnostic Techniques, and Therapeutic Drugs

Context: Some recent reports have indicated that almost 80% of clinical infections in humans have biofilm origin and impose additional healthcare costs. This study was an updated review of extracellular polymeric substance matrix (Biofilm) formation in humans and elaborated on its clinical significance, diagnosis, and therapeutic approaches. Evidence Acquisition: This narrative study reviewed the most recent information on the significance of microbial biofilm formation in clinical settings, common biofilm-producing bacterial species, its diagnosis, antibiotic drug resistance, and new approaches to the treatment of infections associated with biofilm formation. Results: Evidence indicated a permanent increase in the frequency of microbial biofilm in the central venous catheter, mechanical heart valve, and urinary catheter, as well as persistent infections. However, antimicrobial resistance induced by biofilms formation and the antimicrobial treatment of biofilms were problematic. Moreover, several assays and lab devices were described to evaluate biofilm formation. Furthermore, new attitudes towards anti-biofilm treatments were introduced in this paper. Conclusions: The number of different mechanisms were in accordance with the recent knowledge on how biofilms play a critical role in the disease pathogenesis. Biofilm strikes the treatment and surveillance of patients bearing infectious diseases under different conditions. The use of new methods in anti-biofilm treatments is effective for the recovery of infected patients.

Newer Quinolones in the Treatment of Continuous Ambulatory Peritoneal Dialysis (CAPD) Related Infections

Newer fluoroquinolones such as ciprofloxacin, pefloxacin, ofloxacin, enoxacin, and fleroxacin are potent antimicrobial agents against many gram-negative bacteria, including Pseudomonas aeruginosa species and staphylococci-sensitive or resistant to methicillin. They are almost completely absorbed when given orally, reaching therapeutic plasma and dialysate concentrations, and their long half lives permit infrequent dosing intervals.

Clinical studies on fluoroquinolones efficacy in continuous ambulatory peritoneal dialysis (CAPD) infections, although not extensive, demonstrate good results. They are well tolerated and the adverse reactions, consisting mainly of gastrointestinal disturbance, were uncommon, mild, and reversible. The fluoroquinolones offer a promising alternative to standard parenteral treatments in CAPD patients, while their good oral bioavailability makes them attractive and convenient for both patients and hospital staff. However, they must be used with caution until we have more information and gain further experience.

Continuous Ambulatory Peritoneal Dialysis Connection Systems

The history of the various connection systems proposed and tried during the first 15 years of clinlcal application of continuous ambulatory peritoneal dialysis (CAPD) is reviewed.

In order to understand the reasons for their success or lack of success, the main technical and operating characteristics regarding their efficacy In preventing peritonitis are examined in detail, together with a range of other pros and cons (I.e., reliability, simplicity, ease of use, cost, aesthetlcal aspects).

The result Is an updated state-of-the-art review In the field of CAPD connectology, with a look at future trends.

Tenckhoff Catheter Penetrated by Aspergillus Fumigatus: A Case Report

A case of fungal penetration (AspergIllus fumigatus) of a Tenckhoff catheter in a 68-year-old female treated for five years with peritoneal dialysis is reported. Though histopathological and microbiological examination of the removed catheter revealed disseminated colonization, the patient presented no clinical signs of peritoneal infection, cultures of peritoneal fluid were negative, and dialysis procedures were without problems.

Continuous Ambulatory Peritoneal Dialysis (CAPD) Peritonitis: The Effect of Antibiotic on the Adherence of Coagulase-Negative Staphylococci to Silicone Rubber Catheter Material

Peritonitis is the major complication of continuous ambulatory peritoneal dialysis (CAPO) and is caused predominantly by coagulase-negative staphylococci (CNS). Adherence to the silicone rubber Tenckhoff catheter has been identified as one factor in the pathogenesis and persistence of these infections. We have studied the adherence of CNS from patients and controls to silicone rubber in an in vitro model to determine whether this phenomenon can be modified by antibiotics. Adherence was strong for 7/27 (26%) CAPO isolates and for 3/27 (11%) of control strains. The strongly adherent CAPO isolates, when exposed to subinhibitory concentrations of vancomycin, cefuroxime, and ciprofloxacin, showed minimal alteration in adherence with vancomycin in both broth and used dialysate, whereas cefuroxime and ciprofloxacin both significantly reduced it. These observations may have implications for drug selection and prevention of CAPO peritonitis caused by CNS.

Ultrastructure Analysis of Tenckhoff Chronic Peritoneal Catheters Used in Continuous Ambulatory Peritoneal Dialysis Patients

The luminal and external surfaces of 18 curled silicone double-cuff catheters removed from patients who had been on continuous ambulatory peritoneal dialysis (CAPO) for 2-77 months (average 37±21 months) were analyzed by scanning electron microscopy (SEM) and microbiological cultures.

Eight catheters (G1) were removed due to recurrent peritonitis or peritonitis refractory to antibiotic management, and the others (G2) due to local or clinical problems.

The peritonitis rate was one episode every 24 patient months in G1, and 80 patient-months in G2.

All catheter surfaces were covered with proteinlike granular deposits (0.15±0.111cm); 6 catheters were covered by microbial biofilm (0.24±0.161cm). Positive cultures of catheter segments were obtained in 6 cases (4 for G1 and 2 for G2) with a preponderance (33%) of StaphYlococcus aureus among the cultivated bacteria.

Structural defects and small linear tears were present on both luminal and external surfaces in 8 catheters. Structural defects were frequent in the catheters removed for recurrent peritonitis. Linear tears appeared more frequently in the catheters used for a longer time. Structural defects of catheter surfaces were also discovered in the newer devices.

The structural defects of the catheter appear to facilitate microbial adhesion and colonization and to predispose the patient to recurrence of peritonitis.

A better catheter design and an improvement in the production process should therefore be recommended.

Demonstration of the Bacterial-Biomaterial Interface in Implant Specimens

Bacterial infection can be a problem associated with biomaterial implants especially with the total artificial heart or other cardiovascular prostheses such as ventricular assist devices, intravenous catheters, ventriculo-atrial shunts, pacemaker electrodes and, rarely, prosthetic heart valves. Bacterial commensals such as Staphylococcus epidermidis, which is ordinarily non-infective in human skin and mucous membranes, is now recognized as an opportunistic pathogen of biomaterial implants, particularly cardiovascular prostheses. In these implantations the S. epidermidis undergoes transformation to produce mucoid or polysaccharide extracellular coating substances. The latter promote bacterial adherence to biomaterial surfaces and protect the bacteria to some extent against antibiotics and host defense mechanisms. The result is increased virulence of the slime-producing strains. A number of techniques have been developed in our laboratories which facilitate identification of such bacterial pathogens on biopsy or postmortem specimens. These light and analytical electron microscopic methodologies include special cytochemical staining and rapid drying and embedding methods. Their efficacy and accuracy have been verified by studies on cultured and subcultured pathogens which are more time consuming. It is of interest that the microscopic methods showed the presence of macrophages as well as neutrophils on the specimens.

Infections in patients undergoing peritoneal dialysis

Considering experience acquired in the past years, it seems as though physicians have reached a plateau in the frequency of peritonitis. A peritonitis rate of 1 every 2 patient years may be acceptable. Further reduction of this peritonitis rate will require inordinately large efforts on all fronts. One will have to consider what are the acceptable costs and risks of peritonitis in patients on peritoneal dialysis. New developments in catheter technology, improved connections, better understanding of patient selection and training programs, improved diagnostic and therapeutic methods in the management of peritonitis, and understanding of the infectious and immune processes are eagerly awaited developments.

Biofilm susceptibility to antimicrobials

Microbial biofilms, where organisms are intimately associated with each other and a solid substratum through binding and inclusion within an exopolymer matrix, are widely distributed in nature and disease. In the mouth, multispecies biofilms are associated not only with dental plaque and tooth decay but also with soft tissues of the buccal cavity and with most forms of periodontal disease. Organization of micro-organisms within biofilms confers, on the component species, properties which are not evident with the individual species grown independently or as planktonic populations in liquid media. While many of these properties relate to the establishment of functional, mixed-species consortia within the exopolymeric matrices, others relate to the establishment of physico-chemical gradients, within the biofilm, that modify the metabolism of the component cells. A consequence of biofilm growth that has profound implications for their control in the environment and in medicine is a markedly enhanced resistance to chemical antimicrobial agents and antibiotics. Mechanisms associated with such resistance in biofilms will form the substance of the present review. While some aspects of biofilm resistance are yet only poorly understood, the dominant mechanisms are thought to be related to: (i) modified nutrient environments and suppression of growth rate within the biofilm; (ii) direct interactions between the exopolymer matrices, and their constituents, and antimicrobials, affecting diffusion and availability; and (iii) the development of biofilm/attachment-specific phenotypes.

Antibiotic resistance of biofilms

Microbial biofilms are notably recalcitrant towards treatment with antibiotics, biocides or disinfectants that would adequately control the same organisms growing in planktonic mode. Much of this resistance has been attributed to an organisation of the biofilm cells within exopolymer matrices. Whilst such exopolymers are unlikely to hinder the diffusion and access of antimicrobial agents to the underlying cells, they will chemically quench reactive biocides such as chlorine and peroxygens, and bind highly charged antibiotics, such as tobramycin and gentamycin, thereby providing some protection to the more deep lying cells. Extracellular enzymes, bound within the glycocalyx and able to degrade the treatment agents, will further reduce the access of susceptible compounds. Diffusion limitation however, is unlikely to be the sole moderator of the resistance properties of microbial biofilms. In addition, gradients of oxygen and nutrients established across the biofilm community will cause growth rates to be much reduced at points remoted from the accessible nutrient. Slow growth rates, and the associated induction of stringent responses further contribute towards this resistance. Finally, there have been recent demonstrations that attachment of microorganisms to surfaces promotes the expression of genes that are not normally expressed in planktonic culture. Whether or not the expression of such genes alters the phenotype in a manner which alters the response of the cells to antimicrobial agents remains to be demonstrated.

Methicillin-resistant staphylococcal infections in an outpatient peritoneal dialysis program

In view of the increasing concern about hospital-acquired methicillin resistance, we examined the sensitivities and outcome of staphylococcal infections related to outpatient peritoneal dialysis over a 5-year period. Data on all episodes of peritonitis (n = 360) and catheter infections (n = 507) were gathered prospectively from January 1984 to December 1988. The numbers of patients on peritoneal dialysis each year ranged from 136 in 1984 to 109 in 1987. Fifteen methicillin-resistant staphylococcal infections (MRSI) related to outpatient peritoneal dialysis occurred. Three were due to methicillin-resistant Staphylococcus aureus found in infected exit sites (2.3% of all S aureus catheter infections). Two of these infections occurred in a continuous ambulatory peritoneal dialysis (CAPD) patient who carried methicillin-resistant S aureus in his nares. The other 12 methicillin-resistant organisms were coagulase-negative staphylococci that caused peritonitis. There was a significant increase in the percentage of episodes of coagulase-negative staphylococci peritonitis caused by methicillin-resistant organisms; from 5% (3/57) in 1984 through 1986 to 28% (9/32) in 1987 through 1988 (P less than 0.005). In view of the high percentage of coagulase-negative staphylococci peritonitis that is methicillin-resistant, vancomycin rather than cephalosporins should be used for initial treatment.

Role of the cell envelope in bacterial adaptation to growth in vivo in infections

To establish an infection, a pathogenic bacterium must adapt to growth in the hostile environment encountered in vivo in host tissues. The cell envelope plays a crucial role in this adaptive process, since it is involved in promoting adhesion to and colonisation of host tissues, in the acquisition of essential nutrients and in conferring resistance to host defences and to antibiotics. Its properties are ultimately determined by the information stored within the genome, which also contains the potential to respond to environmental change. The macromolecular structure and function of the cell envelope are largely determined by the growth environment and, in particular, specific nutrient limitation, growth rate, growth temperature and replication in suspension or within a surface-associated biofilm. Bacteria growing in vivo will manufacture envelopes characteristic of that environment and which will differ markedly in physiology, biochemistry and immunogenicity from those of cells grown in a standard laboratory medium. In vivo, the ability to withhold iron is an important component of the host's defence and iron deprivation has a pronounced effect on the metabolism and cell envelope properties of pathogenic bacteria. The phenotypic plasticity of the bacterial cell surface plays an important role in determining susceptibility to host defences and antibiotics and has important implications for the design and evaluation of new therapeutic strategies for the treatment and prevention of bacterial infections.