Biofilm Related Infections: Is There a Place for Conservative Treatment of Port-Related Bloodstream Infections?

A Novel Antimicrobial Peptide (Kassinatuerin-3) Isolated from the Skin Secretion of the African Frog, Kassina senegalensis

Amphibian skin secretions are remarkable sources of novel bioactive peptides. Among these, antimicrobial peptides have demonstrated an outstanding efficacy in killing microorganisms via a general membranolytic mechanism, which may offer the prospect of solving specific target-driven antibiotic resistance. Here, the discovery of a novel defensive peptide is described from the skin secretion of the African frog, Kassina senegalensis. Named kassinatuerin-3, it was identified through a combination of “shot-gun” cloning and MS/MS fragmentation sequencing. Subsequently, a synthetic replicate was subjected to biofunctional evaluation. The results indicated that kassinatuerin-3 possessed antimicrobial activity against Gram-positive bacteria but no effect against Gram-negative bacteria. Additionally, it was active in biofilm eradication on S. aureus and MRSA and in the antiproliferation of selected cancer cell lines. Moreover, it had a very mild hemolytic effect, which demonstrated a high therapeutic index for kassinatuerin-3. Collectively, although kassinatuerin-3 did not demonstrate remarkable bioactivities compared with other natural or synthetic antimicrobial peptides (AMPs), it offered a new insight into the design of antimicrobial derivatives.

Biotechnological War against Biofilms. Could Phages Mean the End of Device-Related Infections?

Microorganisms universally attach to surfaces, resulting in biofilm formation. These biofilms entail a serious problem in daily clinical practice because of the great prevalence of implantable device-related infections. Differences in antibiotic activity against planktonic and sessile bacteria may relate to clinical failures in the treatment of biofilm-related infections (BRI). Bacteriophages have several characteristics that make them potentially attractive therapeutic agents in some selected clinical settings, like for example BRI. They are highly specific and very effective in lysing targeted bacteria, moreover, they appear to be safe for humans. Many studies have shown the potential of phages for the treatment of infectious diseases in plants and animals, including infections with highly drug-resistant bacteria. The therapeutic use of bacteriophages, possibly in combination with antibiotics, may be a valuable approach in BRI. However, many important questions still remain that must be addressed before phages can be endorsed for therapeutic use in humans.

Role of Antibiotic Lock Therapy for the Treatment of Catheter-Related Bloodstream Infections

Catheter-related bloodstream infections are often difficult to treat because they are caused by organisms that embed themselves in a bio film layer on the catheter surface, resulting in an increased resistance to antimicrobial agents. Systemic antibiotics are usually administered but, although generally effective in eliminating circulating bacteria, they frequently fail to sterilize the line, leaving the patient at a continuing risk of complications or recurrence. A successful approach to managing these infections requires making an appropriate decision regarding whether the catheter should be removed or retained using antibiotic lock therapy; and choosing the type and duration of antimicrobial therapy based on the type of organism and its resistance pattern. Studies that have evaluated antibiotic lock therapy have varied in the types of antibiotics and concentrations used, the addition of heparin to the solutions, and dwell times in the catheter lumen. Guidelines from the Infectious Diseases Society of America include use of antibiotic lock therapy as a therapeutic option for intraluminal infections when the device is not removed and, although not routine, as prophylaxis for catheter-related infection in select patient populations. However, there are no published guidelines on the concentration of heparin or antibiotics that should be used, and minimal published data on the stability of heparin combinations with antibiotics. It is to be hoped that antibiotic locks will be subject to randomized controlled trials of sufficient power to confirm or refute their use.

A rat model of central venous catheter to study establishment of long-term bacterial biofilm and related acute and chronic infections

Formation of resilient biofilms on medical devices colonized by pathogenic microorganisms is a major cause of health-care associated infection. While in vitro biofilm analyses led to promising anti-biofilm approaches, little is known about their translation to in vivo situations and on host contribution to the in vivo dynamics of infections on medical devices. Here we have developed an in vivo model of long-term bacterial biofilm infections in a pediatric totally implantable venous access port (TIVAP) surgically placed in adult rats. Using non-invasive and quantitative bioluminescence, we studied TIVAP contamination by clinically relevant pathogens, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis, and we demonstrated that TIVAP bacterial populations display typical biofilm phenotypes. In our study, we showed that immunocompetent rats were able to control the colonization and clear the bloodstream infection except for up to 30% that suffered systemic infection and death whereas none of the immunosuppressed rats survived the infection. Besides, we mimicked some clinically relevant TIVAP associated complications such as port-pocket infection and hematogenous route of colonization. Finally, by assessing an optimized antibiotic lock therapy, we established that our in vivo model enables to assess innovative therapeutic strategies against bacterial biofilm infections.

A new approach for the discovery of antibiotics by targeting non-multiplying bacteria: a novel topical antibiotic for staphylococcal infections

In a clinical infection, multiplying and non-multiplying bacteria co-exist. Antibiotics kill multiplying bacteria, but they are very inefficient at killing non-multipliers which leads to slow or partial death of the total target population of microbes in an infected tissue. This prolongs the duration of therapy, increases the emergence of resistance and so contributes to the short life span of antibiotics after they reach the market. Targeting non-multiplying bacteria from the onset of an antibiotic development program is a new concept. This paper describes the proof of principle for this concept, which has resulted in the development of the first antibiotic using this approach. The antibiotic, called HT61, is a small quinolone-derived compound with a molecular mass of about 400 Daltons, and is active against non-multiplying bacteria, including methicillin sensitive and resistant, as well as Panton-Valentine leukocidin-carrying Staphylococcus aureus. It also kills mupirocin resistant MRSA. The mechanism of action of the drug is depolarisation of the cell membrane and destruction of the cell wall. The speed of kill is within two hours. In comparison to the conventional antibiotics, HT61 kills non-multiplying cells more effectively, 6 logs versus less than one log for major marketed antibiotics. HT61 kills methicillin sensitive and resistant S. aureus in the murine skin bacterial colonization and infection models. No resistant phenotype was produced during 50 serial cultures over a one year period. The antibiotic caused no adverse affects after application to the skin of minipigs. Targeting non-multiplying bacteria using this method should be able to yield many new classes of antibiotic. These antibiotics may be able to reduce the rate of emergence of resistance, shorten the duration of therapy, and reduce relapse rates.