Effect of lipoproteins on hemolytic and antifungal activity of amphotericin B and other polyene antibiotics

Lime Peel Oil–Incorporated Rosin-Based Antimicrobial In Situ Forming Gel

Localized intra-periodontal pocket drug delivery using an injectable in situ forming gel is an effective periodontitis treatment. The aqueous insoluble property of rosin is suitable for preparing a solvent exchange-induced in situ forming gel. This study aims to investigate the role of incorporating lime peel oil (LO) on the physicochemical properties of injectable in situ forming gels based on rosin loaded with 5% w/w doxycycline hyclate (DH) in dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP). Their gel formation, viscosity, injectability, mechanical properties, wettability, drug release, and antimicrobial activities were evaluated. The presence of LO slowed gel formation due to the loose precipitate formation of gel with a high LO content. The viscosity and injectability were slightly increased with higher LO content for the DH-loaded rosin-based in situ forming gel. The addition of 10% LO lowered gel hardness with higher adhesion. LO incorporation promoted a higher drug release pattern than the no oil-added formulation over 10 days and the gel formation rate related to burst drug release. The drug release kinetics followed the non-Fickian diffusion mechanism for oil-added formulations. LO exhibited high antimicrobial activity against Porphyromonas gingivalis and Staphylococcus aureus. The DH-loaded rosin in situ forming gel with an addition of LO (0, 2.5, 5, and 10% w/w) inhibited all tested microorganisms. Adding 10% LO to rosin-based in situ forming gel improved the antimicrobial activities, especially for the P. gingivalis and S. aureus. As a result, the study demonstrates the possibility of using an LO amount of less than 10% loading into a rosin-based in situ forming gel for efficient periodontitis treatment.

A Bioinspired, Sustained-Release Material in Response to Internal Signals for Biphasic Chemical Sensing in Wound Therapy

Biofluorescence in living entities is a functional process associated with information conveyance; whereas the capacity to respond to internal physiological signals is a unique property of a cell. By integrating these two biological features into materials design, a bioinspired material, namely CPS, is developed. Contrary to conventional luminescent polymeric systems whose emission comes from π-conjugated structures, this material displays clusterization-triggered emission. In the preclinical trial on a dermal punch model of tissue repair, it successfully increases the rate of wound closure, reduces inflammatory cell infiltration, and enhances collagen deposition. It can also relay changes in internal chemical signals into changes in its intrinsic luminescence for biphasic chemical sensing to prevent possible occurrence of skin hyperpigmentation caused by minocycline hydrochloride in wound therapy. Together with its ease of fabrication, high biocompatibility, high drug loading efficiency, and high release sustainability, CPS shows high potential to be developed into an intelligent solid-state device for wound treatment in the future.

Minocycline Combined with Vancomycin for the Treatment of Methicillin-Resistant Coagulase-Negative Staphylococcal Prosthetic Joint Infection Managed with Exchange Arthroplasty

Introduction: Treatment of methicillin-resistant (MR) staphylococcal prosthetic joint infections (PJIs) remains a matter of discussion, with vancomycin-rifampin combination therapy being the preferred treatment for DAIR and one-stage exchange arthroplasty strategies. This study analyzes the outcomes of patients with chronic methicillin-resistant coagulase-negative staphylococcal PJIs treated with vancomycin-minocycline combination therapy.

Methods: This prospective, single center cohort study included all chronic MR coagulase-negative staphylococcal PJIs (01/2004-12/2014) treated with exchange arthroplasty and at least 4 weeks of minocycline-vancomycin. The following endpoints were considered: reinfection including relapse (same microorganism) and a new infection (different microorganism) and PJI-related deaths. Their outcomes were compared with PJIs treated with rifampin-vancomycin during the same period.

Results: Thirty-four patients (median age, 69 years) with 22 hip and 12 knee arthroplasty infections were included. Sixteen (47%) had previously been managed in another center. Median vancomycin MIC of strains was 3 mg/L. Nineteen underwent one-stage, 15 two-stage exchange arthroplasty. After a median [IQR] follow-up of 43 [26-68] months, 2 patients relapsed and 6 developed a new PJI. Compared to 36 rifampin-vancomycin treated PJIs, relapse- or reinfection-free survival rates didn't differ, but more new infections developed in the minocycline group (6 vs 3; P 0.3).

Conclusions: Minocycline-vancomycin combination therapy for chronic MR coagulase-negative staphylococcal PJIs seems to be an interesting therapeutic alternative.

Minocycline impairs TNF-α-induced cell fusion of M13SV1-Cre cells with MDA-MB-435-pFDR1 cells by suppressing NF-κB transcriptional activity and its induction of target-gene expression of fusion-relevant factors

Background

To date, several studies have confirmed that driving forces of the inflammatory tumour microenvironment trigger spontaneous cancer cell fusion. However, less is known about the underlying factors and mechanisms that facilitate inflammation-induced cell fusion of a cancer cell with a normal cell. Recently, we demonstrated that minocycline, a tetracycline antibiotic, successfully inhibited the TNF-α-induced fusion of MDA-MB-435 cancer cells with M13SV1 breast epithelial cells. Here, we investigated how minocycline interferes with the TNF-α induced signal transduction pathway.

Methods

A Cre-LoxP recombination system was used to quantify the fusion of MDA-MB-435-pFDR1 cancer cells and M13SV1-Cre breast epithelial cells. The impact of minocycline on the TNF-α signalling pathway was determined by western blotting. The transcriptional activity of NF-κB was characterised by immunocytochemistry, western blot and ChIP analyses. An NF-κB-luciferase reporter assay was indicative of NF-κB activity.

Results

Minocycline treatment successfully inhibited the TNFR1-TRAF2 interaction in both cell types, while minocycline abrogated the phosphorylation of IκBα and NF-κB-p65 to suppress nuclear NF-κB and its promotor activity only in M13SV1-Cre cells, which attenuated the expression of MMP9 and ICAM1. In MDA-MB-435-pFDR1 cells, minocycline increased the activity of NF-κB, leading to greater nuclear accumulation of NF-κB-p65, thus increasing promoter activity to stimulate the expression of ICAM1. Even though TNF-α also activated all MAPKs (ERK1/2, p38 and JNK), minocycline differentially affected these kinases to either inhibit or stimulate their activation. Moreover, SRC activation was analysed as an upstream activator of MAPKs, but no activation by TNF-α was revealed. The addition of several specific inhibitors that block the activation of SRC, MAPKs, AP-1 and NF-κB confirmed that only NF-κB inhibition was successful in inhibiting the TNF-α-induced cell fusion process.

Conclusion

Minocycline is a potent inhibitor in the TNF-α-induced cell fusion process by targeting the NF-κB pathway. Thus, minocycline prevented NF-κB activation and nuclear translocation to abolish the target-gene expression of MMP9 and ICAM1 in M13SV1-Cre cells, resulting in reduced cell fusion frequency.

Community-Associated Methicillin-Resistant Staphylococcus aureus: New Bug, Old Drugs

Objective:

To discuss community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections and evaluate older antibiotics as suitable therapeutic treatment options.

Data Sources:

Searches of MEDLINE, EMBASE, and the Cochrane Library (1966–May 2006) were performed using the key terms methicillin resistance, community-acquired, community associated, treatment, Staphylococcus aureus, mec, and Panton-Valentine leukocidin.

Study Selection and Data Extraction:

All articles were critically evaluated and all relevant information was included in this review.

Data Synthesis:

There has been a documented shift of methicillin resistance occurring in staphylococcal infections manifested within the community. Infections caused by CA-MRSA possess unique characteristics including lack of hospital-associated risk factors, improved susceptibility patterns, distinct genotypes, faster doubling times, and additional toxins. Potential therapeutic options to treat these infections include trimethoprim/sulfamethoxazole (TMP/SMX), clindamycin, tetracyclines, fluoroquinolones, and new antimicrobials.

Conclusions:

CA-MRSA infections can be successfully treated with older, oral antibiotic agents including TMP/SMX, clindamycin, and tetracyclines. Fluoroquinolones and linezolid should be avoided as first-line agents.

Combination of alpha-melanocyte stimulating hormone with conventional antibiotics against methicillin resistant Staphylococcus aureus

Our previous studies revealed that alpha-melanocyte stimulating hormone (α-MSH) is strongly active against Staphylococcus aureus (S. aureus) including methicillin resistant S. aureus (MRSA). Killing due to α-MSH occurred by perturbation of the bacterial membrane. In the present study, we investigated the in vitro synergistic potential of α-MSH with five selected conventional antibiotics viz., oxacillin (OX), ciprofloxacin (CF), tetracycline (TC), gentamicin (GM) and rifampicin (RF) against a clinical MRSA strain which carried a type III staphylococcal cassette chromosome mec (SCCmec) element and belonged to the sequence type (ST) 239. The strain was found to be highly resistant to OX (minimum inhibitory concentration (MIC) = 1024 µg/ml) as well as to other selected antimicrobial agents including α-MSH. The possibility of the existence of intracellular target sites of α-MSH was evaluated by examining the DNA, RNA and protein synthesis pathways. We observed a synergistic potential of α-MSH with GM, CF and TC. Remarkably, the supplementation of α-MSH with GM, CF and TC resulted in ≥64-, 8- and 4-fold reductions in their minimum bactericidal concentrations (MBCs), respectively. Apart from membrane perturbation, in this study we found that α-MSH inhibited ∼53% and ∼47% DNA and protein synthesis, respectively, but not RNA synthesis. Thus, the mechanistic analogy between α-MSH and CF or GM or TC appears to be the reason for the observed synergy between them. In contrast, α-MSH did not act synergistically with RF which may be due to its inability to inhibit RNA synthesis (<10%). Nevertheless, the combination of α-MSH with RF and OX showed an enhanced killing by ∼45% and ∼70%, respectively, perhaps due to the membrane disrupting properties of α-MSH. The synergistic activity of α-MSH with antibiotics is encouraging, and promises to restore the lost potency of discarded antibiotics.

Trends and factors associated with initial and recurrent methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections among HIV-infected persons: an 18-year study

BACKGROUND

Factors associated with initial methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections (SSTIs) and their recurrence have not been fully elucidated among HIV-infected persons.

METHODS

We retrospectively evaluated a large cohort of HIV-infected patients from 1993 to 2010 for culture-proven MRSA SSTIs. Separate logistic regression models evaluated factors associated with initial and recurrent infections.

RESULTS

Of the 794 patients, 63 (8%) developed an initial infection (19.8 infections/1000 person years [PY]); risk factors included CD4 count <500 cells/mm(3) and HIV RNA level ≥400 copies/mL (P < .01), US Centers for Disease Control and Prevention (CDC) stage C versus A/B (P < .01), and injection drug use (IDU, P < .01). In all, 27% developed recurrence (206 infections/1000 PY); risk factors included hospital admission (P = .02). Minocycline for treatment of the initial infection was associated with an 80% decreased odds for recurrence (P = .03).

CONCLUSION

HIV control and avoidance of IDU may be useful in reducing rates of MRSA SSTIs among HIV-infected persons.

Minocycline: old and new therapeutic uses

Since the introduction of minocycline HCl in the late 1960's, it has been used for disease states that have ranged from typical community-acquired infectious diseases to others that are non-infectious, such as resistant rheumatoid arthritis. Owing to its high penetration characteristics throughout the body, minocycline can be used in the treatment of a wide variety of extracellular and intracellular pathogens. This review examines the known and potential therapeutic uses of minocycline in a clinical setting.

Minocycline-EDTA lock solution prevents catheter-related bacteremia in hemodialysis

There is growing concern about the development of antibacterial resistance with the use of antibiotics in catheter lock solutions. The use of an antibiotic that is not usually used to treat other serious infections may be an alternative that may reduce the clinical impact should resistance develop. We conducted a randomized controlled trial to compare a solution of minocycline and EDTA with the conventional unfractionated heparin for the prevention of catheter-related bacteremia in hemodialysis patients during a period of 90 d. The study included 204 incident catheters (27.8% tunneled); 14 catheters were excluded because of early dysfunction and 3 because of protocol violations. We observed catheter-related bacteremia in 19 patients in the heparin group (4.3 per 1000 catheter-days) and in 5 patients in the minocycline-EDTA group (1.1 per 1000 catheter-days; P = 0.005). We did not detect a significant difference in the rate of catheter removal for dysfunction. Catheter-related bacteremia-free survival was significantly higher in the minocycline-EDTA group than in the heparin group (P = 0.005). In conclusion, a minocycline-EDTA catheter lock solution is effective in the prevention of catheter-related bacteremia in hemodialysis patients.

Randomized study of minocycline and edetic acid as a locking solution for central line (port-a-cath) in children with cancer

BACKGROUND

Contamination of central catheters is frequent, and biofilm perpetuates infections. Heparin does not protect against infections because it has no antibiotic action. Minocycline and edetic acid (M-EDTA), a potent calcium chelating agent that destroys bacterial and fungal cell membrane and disrupts biofilm, may be an alternative to allow the associated antibiotic to act locally at a high and safe concentration.

METHODS

Fifty children with cancer and a port-a-cath were followed up: 26 received heparin (group 1) and 24 M-EDTA (group 2). A total of 762 serial prospective blood cultures were obtained, 387 from group 1 and 375 from group 2.

RESULTS

In group 1 (heparin), 19 blood cultures were positive, and infection incidence was 73.1% (19/26 ports). In group 2 (M-EDTA), 5 blood cultures were positive, and the incidence rate was 20.8% (5/24 ports).

CONCLUSION

M-EDTA, compared with heparin, prevents and treats catheter infections, and is a promising alternative to decrease sepsis during chemotherapy.

Community-associated meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide, and causes substantial morbidity and mortality. Health-care-associated MRSA infections arise in individuals with predisposing risk factors, such as surgery or presence of an indwelling medical device. By contrast, many community-associated MRSA (CA-MRSA) infections arise in otherwise healthy individuals who do not have such risk factors. Additionally, CA-MRSA infections are epidemic in some countries. These features suggest that CA-MRSA strains are more virulent and transmissible than are traditional hospital-associated MRSA strains. The restricted treatment options for CA-MRSA infections compound the effect of enhanced virulence and transmission. Although progress has been made towards understanding emergence of CA-MRSA, virulence, and treatment of infections, our knowledge remains incomplete. Here we review the most up-to-date knowledge and provide a perspective for the future prophylaxis or new treatments for CA-MRSA infections.

Treatment options for skin and soft tissue infections caused by meticillin-resistant Staphylococcus aureus:oralvs.parenteral; home vs. hospital

Although meticillin-resistant Staphylococcus aureus (MRSA) is recognized as a significant cause of nosocomial infections, it is also becoming an increasingly common cause of infections in the community. Overall, the most common infections caused by MRSA are those involving the skin and skin structures. These infections are difficult to treat and are associated with high morbidity and substantial cost. This article summarizes the current oral and parenteral therapeutic options, of which there are several, and the optimal site of care for the management of these infections. Defining the severity of the illness is central to improving the decision-making process about the route of administration and site of care.

Minocycline--an old drug for a new century: emphasis on methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii

The epidemiology of nosocomial and community-acquired infections has changed in recent years. Methicillin-resistant Staphylococcus aureus (MRSA), especially community-associated MRSA (CA-MRSA), has emerged as a gram-positive organism with an increasing impact in clinical practice. Infections with Acinetobacter baumannii have become a major cause of morbidity and mortality. Minocycline has significant in vitro activity against MRSA and A. baumannii that is comparable with agents currently used against these organisms. The absence of an intravenous (i.v.) minocycline formulation in recent years has limited its use in seriously ill patients infected with these organisms. However, minocycline i.v. has recently been reintroduced to the US market. The objective of this study was to review available information on the chemistry, mechanism of action, in vitro activity, resistance mechanisms, pharmacokinetics, tolerability and efficacy of minocycline against MRSA and A. baumannii. This article provides suggestions for future studies and potential uses of minocycline and is designed to trigger interest in systematic clinical evaluation of minocycline for patients infected with these organisms. In conclusion, minocycline is an old drug that has the potential to become an important part of the armamentarium against emerging infections such as CA-MRSA and A. baumannii. Owing to its promising profile against these clinically important pathogens as well as excellent pharmacokinetic properties, minocycline merits evaluation in serious infections.

Management of methicillin-resistant Staphylococcus aureus infections

This review addresses selected aspects of the management of severe healthcare-associated infections due to methicillin-resistant Staphylococcus aureus (MRSA), including the limitations of current therapy, potential alternative agents, new therapeutic options, clinical approaches to MRSA bacteraemia/endocarditis and ventilator-associated pneumonia, and strategies to improve outcomes in patients with severe MRSA infections.

Effect of oxazolidinone, RBx 7644 (ranbezolid), on inhibition of staphylococcal adherence to plastic surfaces

Adhesion to biomaterial is assumed to be a crucial step in the pathogenesis of foreign body infection. Slime producing Staphylococcus epidermidis and Staphylococcus aureus have emerged as a preeminent cause of nosocomial bacteremia and infections of prosthetic medical devices. We evaluated the time-dependent anti-adhesive effect of RBx 7644 (ranbezolid), vancomycin, linezolid and quinupristin/ dalfopristin on two isolates each of S. epidermidis and S. aureus. Linezolid and quinupristin/ dalfopristin showed inhibition only at supra-inhibitory concentrations (2 and 4X MIC) following 2 and 4 h delayed treatment, whereas RBx 7644 demonstrated significant activity against adhesion of staphylococcal cells that had been treated with 2 to 6 h delay. When vancomycin treatment was delayed by 4 to 6 h, even concentrations above the MIC were unable to prevent adherence. This study indicates that RBx 7644 has anti-adhesion potential and may emerge as an important antibiotic for prevention and treatment of device-related infections caused by staphylococci.

Tetracyclines as an oral treatment option for patients with community onset skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus

Few data exist on the clinical utility of the expanded-spectrum tetracyclines doxycycline and minocycline for the treatment of community-associated methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTI). We performed a retrospective cohort study of 276 patients who presented with 282 episodes of MRSA SSTI to the emergency room or outpatient clinic at two tertiary medical centers between October 2002 and February 2007. The median percentage of patients infected with MRSA strains that were susceptible to tetracycline was 95%. Time zero was defined as the time of the first incision and drainage procedure or, if none was performed, the time of the first positive wound culture. The median patient age was 48 years. Abscesses constituted the majority of clinical presentations (75%), followed by furuncles or carbuncles (13%) and cellulitis originating from a purulent focus of infection (12%). A total of 225 patients (80%) underwent incision and drainage. Doxycycline or minocycline was administered in 90 episodes (32%); the other 192 SSTI were treated with beta-lactams. Treatment failure, defined as the need for a second incision and drainage procedure and/or admission to the hospital within at least 2 days after time zero, was diagnosed in 28 episodes (10%) at a median of 3 days after time zero. On logistic regression analysis, receipt of a beta-lactam agent was the only clinical characteristic associated with treatment failure (adjusted odds ratio, 3.94; 95% confidence interval, 1.28 to 12.15; P = 0.02). The expanded-spectrum tetracyclines appear to be a reasonable oral treatment option for patients with community onset MRSA SSTI in areas where MRSA strains are susceptible to the tetracyclines.

New uses for older antibiotics: nitrofurantoin, amikacin, colistin, polymyxin B, doxycycline, and minocycline revisited

Nitrofurantoin, amikacin, colistin, polymyxin B, doxycycline, and minocycline are antibiotics with proven effectiveness against selected pathogens. These antibiotics have not developed resistance over time. As "low-resistance potential antibiotics" that are effective against an increasing number of infections due to resistant gram-positive or gram-negative pathogens, these antimicrobials remain an important part of the antibiotic armamentarium. They will be used increasingly in the future, as highly resistant organisms continue to be important clinically and therapeutic options remain limited.

Use of Long-Acting Tetracyclines for Methicillin-Resistant Staphylococcus aureus Infections: Case Series and Review of the Literature

BACKGROUND

Few data exist on the efficacy of the long-acting tetracyclines doxycycline and minocycline against methicillin-resistant Staphylococcus aureus (MRSA) infection.

METHODS

The medical records of 24 patients with serious tetracycline-susceptible MRSA infections who were treated with doxycycline or minocycline were reviewed. A review of the literature on the use of these antibiotics for treatment of both methicillin-susceptible and methicillin-resistant S. aureus infection was also performed.

RESULTS

Complicated skin and skin-structure infections were most common (67%). Clinical cure was achieved in 20 (83%) of 24 patients in our case series. Both drugs were well-tolerated. The review of the literature on a total of 85 patients with S. aureus infection revealed similar results.

CONCLUSIONS

Long-acting tetracyclines may be a reasonable treatment alternative for patients with certain types of MRSA infection.

Molecular basis for the selective toxicity of amphotericin B for yeast and filipin for animal cells

Among the polyene antibiotics, many, like filipin, cannot be used clinically because they are toxic; amphotericin B, however, is useful in therapy of human fungal infections because it is less toxic. Both the toxicity of filipin and the therapeutic value of amphotericin B can be rationalized at the cellular and molecular level by the following observations: (i) these polyene antibiotics showed differential effects on cells; filipin was more potent in lysing human red blood cells, whereas amphotericin B was more potent in inhibiting yeast cell growth; and (ii) the effects of filipin were more efficiently inhibited by added cholesterol, the major membrane sterol in human cells, whereas the effects of amphotericin B were more efficiently inhibited by ergosterol, the major membrane sterol in yeast. The simplest inference is that the toxicity and effectiveness of polyenes are determined by their relative avidities for the predominant sterol in cell membranes.

Penile prosthesis coating and the reduction of postoperative infection

Despite the recent development of effective oral agents for the treatment of erectile dysfunction, penile prosthesis implantation remains an effective and acceptable treatment for the significant number of men who fail to respond to nonsurgical therapy. The most serious complication that can affect the use of most prosthetic devices is infection. In penile prostheses, this can be devastating and frequently results in removal of the device despite aggressive antibiotic therapy. In recent years, new strategies have been developed in an attempt to minimize this risk. This review focuses on one such method, namely the use of an antibiotic coating on the device. It reviews recent published data regarding the effectiveness of such devices at decreasing infection rates.

Treatment of vancomycin-resistant enterococcal infections in the immunocompromised host: quinupristin-dalfopristin in combination with minocycline

Between February 1994 and November 1998, 56 oncology patients infected with vancomycin-resistant enterococci (VRE) were treated with quinopristin-dalfopristin (Q-D) plus minocycline (MIN). Infections included bacteremia, urinary tract infection, pneumonia, and wound infection. The response rate was 68%, and the most frequent adverse event was arthralgia or myalgia (36%). Q-D-MIN is effective for VRE infection in cancer patients but is associated with a substantial frequency of arthralgia or myalgia.

Antimicrobial durability and rare ultrastructural colonization of indwelling central catheters coated with minocycline and rifampin

OBJECTIVE

To determine the duration of antimicrobial activity and the efficacy of indwelling catheters coated with minocycline and rifampin in preventing ultrastructural colonization.

DESIGN

Multicenter, prospective, randomized, clinical trial.

SETTING

Five university-based medical centers.

PATIENTS

Cohort 1 consisted of 40 randomized patients in whom an equal number of minocycline- and rifampin-coated and uncoated catheters were inserted and studied using scanning electron microscopy. Cohort 2 consisted of 118 patients who received coated catheters that were tested for the antimicrobial activity and levels of the antibiotics at the time of removal.

INTERVENTIONS

Catheters pretreated with tridodecylmethylammonium chloride and subsequently coated with minocycline and rifampin; uncoated catheters (control).

MEASUREMENTS AND MAIN RESULTS

Quantitative scanning electron microscopy was utilized to determine both the ultrastructural colonization in biofilm on coated and uncoated catheters. The zones of inhibition of coated catheters from studied patients against Staphylococcus epidermidis was used to determine the antimicrobial durability. High-performance liquid chromatography was used to determine antibiotic levels on indwelling coated catheters and in serum. Mild-to-heavy ultrastructural colonization was detected in 7 (35%) of 20 coated catheters and in 16 (80%) of 20 uncoated catheters (p = .004). Significant antimicrobial inhibitory activity against S. epidermidis was maintained for 16 days. Rifampin and minocycline continued to be detected on the surfaces of coated catheters for at least 2 wks after placement. Neither antibiotic was detected in the 60 serum samples obtained from 15 patients during catheterization.

CONCLUSION

Coating catheters with minocycline and rifampin inhibits ultrastructural colonization of indwelling catheters and maintains effective antimicrobial activity for at least 2 wks.

New uses for older antibiotics. The 'rediscovery' of four beneficial and cost-effective antimicrobials

Because of its intracellular mechanism of activity, excellent safety profile, and low cost, doxycycline is one of the most extensively used antibiotics in the world, and its use will increase as new applications are found. One of its most important uses is in treatment of bacterial community-acquired pneumonias, but it is also useful against atypical pneumonias and sexually transmitted disease. As zoonotic infections continue to increase around the world, doxycycline will occupy an increasingly prominent place. Minocycline shares doxycycline's favorable attributes and also has tissue-penetration characteristics that are important when therapeutic alternatives are few, as in MRSA. TMP-SMX is widely used to treat urinary and respiratory tract infections and for prophylaxis and treatment of P carinii infection. As the AIDS epidemic continues, its use will continue to grow, because it is also effective against other pathogens associated with AIDS. TMP-SMX is relatively underused for treating gram-negative bacteremias, especially nosocomial infections caused by nonaeruginosa pseudomonads. Metronidazole is a cost-effective antianaerobic component in treatment of intra-abdominal and pelvic infections, especially when it is combined with a once-a-day antibiotic.

Antibiotics and prevention of microbial colonization of catheters

Slime-producing staphylococci frequently colonize catheters, and when they are embedded in biofilm, they become resistant to various antibiotics. In the study that is described, the comparative efficacies of vancomycin, clindamycin, novobiocin, and minocycline, alone or in combination with rifampin, were tested in an in vitro model of colonization. The model consisted of the modified Robbins device with antibiotic-impregnated cement filling the lumen of catheter segments. The synergistic combination of minocycline and rifampin was the most efficacious in preventing bacterial colonization of slime-producing strains of Staphylococcus epidermidis and Staphylococcus aureus to catheter surfaces. A similar trend was observed when the inhibitory activities of polyurethane catheters coated with minocycline and rifampin were compared with the inhibitory activities of catheters coated with other antimicrobial agents. The inhibitory activities of catheters coated with minocycline and rifampin against S. epidermidis, S. aureus, and Enterococcus faecalis strains, for example, were significantly better than those of catheters coated with vancomycin (P < 0.05). The inhibitory activities of catheters coated with minocycline and rifampin against gram-negative bacilli and Candida albicans were comparable to those of catheters coated with ceftazidime and amphotericin B, respectively. We found that the combination of minocycline and rifampin is unique and highly effective in preventing the colonization of catheters with slime-producing staphylococci and that it also displays a broad-spectrum inhibitory activity against gram-negative bacteria and yeast cells.

Minocycline versus vancomycin for treatment of experimental endocarditis caused by oxacillin-resistant Staphylococcus aureus

The purpose of this study was to determine the penetration of minocycline and vancomycin into cardiac vegetations and to determine their efficacy in a rabbit model of endocarditis caused by oxacillin-resistant Staphylococcus aureus. Animals were randomized into three groups: control (no antibiotic), minocycline (6 mg/kg given intravenously every 8 h), and vancomycin (50 mg/kg given intravenously every 8 h). Penetration of the antibiotics into aortic valve vegetations was determined by using the tissue/serum area under the concentration-time curve ratio. The reductions in the bacterial density of the vegetations caused by both vancomycin (4.8 +/- 1.2 CFU/g) and minocycline (5.3 +/- 1.6 CFU/g) were significantly different from that of controls (8.7 +/- 1.8 CFU/g). Although the penetration of minocycline was twice that of vancomycin, they were equally effective in reducing the bacterial density of the vegetations, since the concentrations of both agents in tissue remained above their MICs for oxacillin-resistant S. aureus. For organisms for which the MICs are higher, however, these penetration differences may result in treatment differences.

Methicillin-resistant Staphylococcus aureus: a consensus review of the microbiology, pathogenesis, and epidemiology with implications for prevention and management

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major nosocomial pathogen in community hospitals, long-term-care facilities, and tertiary care hospitals. The basic mechanism of resistance is alteration in penicillin-binding proteins of the organism. Methods for isolation by culture and typing of the organism are reviewed. MRSA colonization precedes infection. A major reservoir is the anterior nares. MRSA is usually introduced into an institution by a colonized or infected patient or health care worker. The principal mode of transmission is via the transiently colonized hands of hospital personnel. Indications for antibiotic therapy for eradication of colonization and treatment of infection are reviewed. Infection control guidelines and discharge policy are presented in detail for acute-care hospitals, intensive care and burn units, outpatient settings, and long-term-care facilities. Recommendations for handling an outbreak, surveillance, and culturing of patients are presented based on the known epidemiology.

In vitro activity of minocycline and rifampin against staphylococci

We tested the in vitro inhibitory and bactericidal activity of minocycline against 26 methicillin-susceptible Staphylococcus aureus, 24 methicillin-resistant S. aureus, 1 methicillin-susceptible coagulase-negative staphylococci, and 33 methicillin-resistant coagulase-negative staphylococci. Minocycline and rifampin had MIC90 results in the susceptible range, but MBCs were markedly elevated for minocycline alone (MBC50 greater than 32 micrograms/ml). The combination of minocycline and rifampin was synergistic for 30% of the isolates with the highest rates of synergy being against methicillin-resistant isolates.

Combination of minocycline and rifampicin against methicillin- and gentamicin-resistant Staphylococcus aureus

Methicillin- and gentamicin-resistant Staphylococcus aureus may remain sensitive to minocycline and to rifampicin. A study of growth curves has shown that at inhibitory concentrations (0.4 mug/ml), minocycline prevents the development of mutants resistant to rifampicin.

Minocycline resistance in Staphylococcus aureus: effect on phage susceptibility

Tetracycline-resistant strains of Staphylococcus aureus are minocycline sensitive, with the exception of strains susceptible to phages of the 83A/84/85 complex and some methicillin-resistant strains of other phage types. Strains of the 83A/84/85 complex yield mutants with increased minocycline resistance. Transduction of minocycline resistance into the susceptible strain RN 450 was obtained with donor strains possessing either markers for both extrachromosomal tetracycline resistance (tet) and chromosomal tetracycline + minocycline resistance (tmn R), or only for chromosomal tmn R resistance. The chromosomal marker was differentiated from the extrachromosomal marker by the lack of detectable extrachromosomal deoxyribonucleic acid after transfer into strain RN 450, transfer into a rec(+) strain, lack of transfer into rec(-) acceptor strain, and cotransduction with chromosomal determinants for guanine biosynthesis. Both chromosomal and extrachromosomal tetracycline resistance can be induced by tetracycline. Induction by tetracycline of chromosomal tetracycline resistance resulted in simultaneous induction of minocycline resistance. The mutation toward increased minocycline resistance (tmn --> tmn R) is a regulatory mutation toward constitutivity or semiconstitutivity. Constitutive resistance is dominant in tmn R/tet diploids. Transfer of the tet marker does not affect the phage susceptibility of the acceptor strain. The tmn R marker, originating from donor strains of the 83A/84/85 complex, renders strain RN 450 resistant to several typing phages, with the exception of phages of the 83A/84/85 complex. This could possibly account for the phage typing patterns of minocycline-resistant staphylococci.

Minocycline: A review of its antibacterial and pharmacokinetic properties and therapeutic use

Minocycline is a semi-synthetic tetracycline derivative which is well absorbed and distributed in body tissues and is suitable for twice daily administration. It appears to be as generally effective as other tetracyclines and analogues, but also to be effective in infections due to tetracycline-resistant staphylococci. Side-effects are typical of those of other tetracyclines, but minocycline has been associated with a high incidence of vertigo in some studies. On the other hand, minocycline appears to have little or no photosensitising potential. It is not yet clear whether minocycline can be safely used in patients with moderate or severe impairment of renal function, but if used in renal failure, the plasma urea concentration should be monitored.

Antibacterial drugs today. I

Since the development of the sulphonamides in the 1930s and the subsequent development of antibiotics from the 1940s onwards, there have now been many drugs developed which are capable of chemotherapeutic activity in a patient infected by a susceptible micro-organism. This review is concerned with precise descriptions of important groups of antimicrobial drugs, with emphasis being placed on the more recently developed drugs. With each group of drugs the pharmacology, major therapeutic indications, dosages and adverse reactions are discussed. Part I of the article discusses the sulphonamides, the natural and semi-synthetic penicillins, cotrimoxazole, chloramphenicol, tetracyclines, the macrolides, lincomycin and clindamycin, fusidic acid, and the urinary antiseptics. The place of each in therapy is defined.

Permeability control in animal cells by polyenes: a possibility

The polyenes amphotericin B and vitamin A enhanced the specific actions of rifampin, fusidic acid, and 1,3-bis(2-chloroethyl)-1-nitrosourea against mouse L cells in tissue culture as measured by macromolecular synthesis and cell survival.

Effect of rapid intravenous infusion on serum concentrations of amphotericin B

The magnitude of the concentrations of amphotericin B produced in serum of patients with systemic mycoses may significantly influence the outcome of therapy with this drug. Since amphotericin B is conventionally administered in intravenous infusions lasting 4 to 6 hr, we asked whether faster infusions of this drug might yield higher serum concentrations without an increase in dose. This question was studied in three patients who received 16 infusions of this drug: eight infusions administered slowly (5 hr) and eight administered rapidly (45 min). Serum concentrations after each rapid infusion were compared with those after a slow infusion administered to the same patient. The mean serum concentration of amphotericin B 1 hr after the rapid infusions (2.02 mug/ml) was significantly higher (P < 0.001) than the mean serum concentration of amphotericin B 1 hr after the slow infusions of this drug (1.18 mug/ml). Mean serum concentrations 18 and 42 hr after rapid infusion remained slightly but not significantly higher than respective mean concentrations after slow infusions. By yielding higher initial serum concentration, rapid intravenous infusion may be therapeutically more effective than slow infusion of amphotericin B. Although rapid infusions caused no more toxicity than did slow infusions, the lack of greater toxicity with rapid infusion of amphotericin B should be further documented prior to extensive clinical application of this procedure.

Amphotericin B serum concentrations during therapy

Therapeutic outcome of patients being treated for systemic mycoses with amphotericin B is possibly related to the serum concentrations of this drug that are produced in these patients. Because current data are conflicting, the magnitude of these concentrations was restudied by using a bioassay which gave precise and accurate results. The highest of 155 serum concentrations was 2.01 mug/ml. Mean concentrations were 1.21, 0.62, and 0.32 mug/ml, at 1, 18, and 42 hr, respectively, after intravenous infusion of amphotericin B. This drug was detected in serum 7 weeks after completion of treatment, but it could not be detected 13 weeks after treatment. Drug levels did not appreciably decrease in serum stored for 8 to 9 months at - 10 C. Unequal serum content in assay tubes and measurement of assay turbidity by visual inspection may explain previously reported amphotericin B levels of 3.0 to 12.5 mug/ml.