Vancomycin therapy of bacterial endocarditis

Predicting adverse drug effects: A heterogeneous graph convolution network with a multi-layer perceptron approach

We apply a heterogeneous graph convolution network (GCN) combined with a multi-layer perceptron (MLP) denoted by GCNMLP to explore the potential side effects of drugs. Here the SIDER, OFFSIDERS, and FAERS are used as the datasets. We integrate the drug information with similar characteristics from the datasets of known drugs and side effect networks. The heterogeneous graph networks explore the potential side effects of drugs by inferring the relationship between similar drugs and related side effects. This novel in silico method will shorten the time spent in uncovering the unseen side effects within routine drug prescriptions while highlighting the relevance of exploring drug mechanisms from well-documented drugs. In our experiments, we inquire about the drugs Vancomycin, Amlodipine, Cisplatin, and Glimepiride from a trained model, where the parameters are acquired from the dataset SIDER after training. Our results show that the performance of the GCNMLP on these three datasets is superior to the non-negative matrix factorization method (NMF) and some well-known machine learning methods with respect to various evaluation scales. Moreover, new side effects of drugs can be obtained using the GCNMLP.

Vancomycin-induced neutropenia: is it dose- or duration-related?

OBJECTIVE

To systematically evaluate the literature to determine whether vancomycin-induced neutropenia is dose- or duration-related and provide clinicians with feasible treatment alternatives.

DATA SOURCES

A literature search of PubMed (1949-November 2010), MEDLINE (1950-November 2010), EMBASE (1980-November 2010), and International Pharmaceutical Abstracts (1970-November 2010) was performed using the terms vancomycin, neutropenia, and leukopenia. Citations from publications were reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION

Studies and case reports were included if they reported neutropenia with vancomycin administration and excluded if they did not describe vancomycin dosages and/or concentrations, or if neutropenia resolved while the patient was still receiving vancomycin. Cases with significant confounders and those in which authors provided minimal information about patients were also excluded.

DATA SYNTHESIS

Seven retrospective chart reviews (ie, case series) and 33 case reports were identified. Of these, 3 retrospective reviews and 26 case reports met inclusion criteria. To our knowledge, no prospective studies have assessed this clinical complication. Data suggest that vancomycin-induced neutropenia may not be completely related to daily dosages, total cumulative dosage, or supratherapeutic vancomycin concentrations. Furthermore, evidence suggests that neutropenia is more likely associated with therapy longer than 7 days, with the majority of episodes occurring beyond 20 days of therapy. Given these findings, a practical approach is to monitor white blood cell (WBC) count with a differential (including absolute neutrophil count) once a week in patients who are receiving vancomycin for more than 7 days.

CONCLUSIONS

Vancomycin-induced neutropenia is most likely associated with prolonged vancomycin exposure. Patients receiving vancomycin for longer than 7 days should have WBC count, differential, monitored weekly. Vancomycin should be discontinued if there is a high clinical suspicion of it causing neutropenia, and an alternative agent should be initiated. Prospective case-controlled studies are needed to better characterize this adverse event.

Limitations of presently available glycopeptides in the treatment of Gram-positive infection

The glycopeptide antibacterial drugs vancomycin and teicoplanin are widely used in hospitals for therapy of severe or multiresistant Gram-positive infections, notably staphylococcal, enterococcal and rarely pneumococcal. Vancomycin has also been used in the management of Clostridium difficile enteropathy. The incidence and potential for resistance differ between agents. The in vitro activity, pharmacokinetics and clinical use of glycopeptide, as well as epidemiology of glycopeptide resistance are discussed. There are limited comparative studies indicating the need for further investigation. Therapeutic drug monitoring has been widely used for vancomycin and less commonly for teicoplanin, but remains controversial. Advances in our understanding of their pharmacodynamics and clinical studies are helping clarify the situation. This paper reviews the current literature and highlights limitations of glycopeptides in treating Gram-positive infection.

Short-course therapy for right-side endocarditis due to Staphylococcus aureus in drug abusers: cloxacillin versus glycopeptides in combination with gentamicin

A prospective, randomized clinical trial among drug abusers was conducted to assess the efficacy and safety of a short course of a combination of a glycopeptide (vancomycin or teicoplanin) and gentamicin compared with a combination of cloxacillin and gentamicin for treatment of right-side endocarditis caused by Staphylococcus aureus. Therapeutic success was significantly more frequent with cloxacillin than with a glycopeptide. No adverse effects were noted among patients in the cloxacillin group. A 14-day course of vancomycin or teicoplanin plus gentamicin is ineffective in this instance because it is associated with a high rate of clinical and microbiological failure.

Infective endocarditis and glycopeptides

BACKGROUND

Despite the number of antibacterial agents currently available, endocarditis remains a difficult disease to treat and the mortality rate has not fallen in recent years. The glycopeptides have good activity against the Gram-positive bacteria commonly implicated in endocarditis (staphylococci, both coagulase-positive and negative; enterococci and streptococci).

OBJECTIVES

To assess the impact of the glycopeptides vancomycin and teicoplanin on the therapy of infectious endocarditis caused by Gram-positive bacteria.

METHODS

A retrospective review of all major published or recently conducted studies using vancomycin or teicoplanin to treat endocarditis.

RESULTS

Cure rates obtained with vancomycin and teicoplanin are similar, but there are no controlled studies to investigate this. Vancomycin nephrotoxicity limits its use in endocarditis, in particular when used in combination with an aminoglycoside. By contrast, teicoplanin shows little nephrotoxic potential, even in patients with some degree of renal impairment or when given in combination with an aminoglycoside. Teicoplanin should be used at doses of 6 mg/kg/day or higher to achieve satisfactory cure rates.

CONCLUSIONS

Clinical data on the use of glycopeptides in endocarditis suffer from a lack of controlled trials. Although teicoplanin appears to offer some advantages over vancomycin in the therapy of endocarditis, there is an urgent need for randomized, clinical trials before definitive conclusions can be drawn.

Chemo-enzymatic transformations in sensitive systems: lipase mediated hydrolysis of vancomycin esters

Recently, an interest in the development of new vancomycin derivatives has been demonstrated. Here, the feasibility of using lipases, particularly those from Pseudomonas sp., for the hydrolysis of vancomycin alkyl esters is demonstrated. Benzyl ester derivatives were more easily cleavable than methyl ester derivatives, resulting in good yields of vancomycin acids without degradation.

Vancomycin administration in continuous ambulatory peritoneal dialysis: the risk of ototoxicity

A prospective study was undertaken in 16 patients with chronic renal failure on continuous ambulatory peritoneal dialysis, with 22 episodes of peritonitis treated with vancomycin, a known ototoxic agent. Twelve patients had one episode each, and four had recurrent peritonitis. Each treatment course consisted of two infusions of vancomycin (30 mg/kg body weight) in 2 L of peritoneal dialysate administered at 6-day intervals. Serum vancomycin analyzed by enzyme immunoassay showed a mean trough level of 11.00 microg/ml on day 6 and mean serum levels of 33.8 and 38.6 microg/ml about 12 hours after administration on days 1 and 7, respectively. Similar levels, well within the therapeutic range, were encountered with repeated vancomycin therapy for recurrent episodes of peritonitis, suggesting that no changes occurred in the pharmacokinetic profile of the drug. Pure-tone audiometry, electronystagmography, and clinical assessment performed during each course of treatment showed no evidence of ototoxicity even on repeated courses of vancomycin therapy. The results suggest that vancomycin therapy when given in appropriate concentrations as a single therapeutic agent is both effective and safe. We believe, however, that vancomycin administered in combination with an aminoglycoside may produce ototoxic effects that may be greatly aggravated, possibly because of synergism.

Development of a quantitative vancomycin immunoassay for the Abbott AxSYM analyzer

A novel fluorescence polarization immunoassay for vancomycin on Abbott AxSYM analyzer is described. The immunoassay allows for the accurate quantification of vancomycin in the presence of the crystalline degradation product (CDP). It displays dilution linearity from 1.0 microg/ml to 100.0 microg/ml, coefficients of variation ranging from 2.94% to 4.26%, recovery from 98% to 105%, and a sensitivity of <2.0 microg/ml. The assay demonstrates no cross-reactivity to crystalline degradation product, and to commonly-prescribed and over-the-counter drugs, as well as a minimum interference from endogenous substances.

Prevention of gram-positive sepsis in neonates weighing less than 1500 grams

A prospective, randomized study to evaluate the effectiveness of a continuous low-dose vancomycin infusion to prevent nosocomial gram-positive bacteremia was initiated within the first 2 weeks of life in neonates weighing < 1500 gm. Seventy-one infants received constant infusion of vancomycin (25 micrograms/ml) mixed with their total parenteral nutrition solution; 70 infants served as control subjects. The groups were clinically similar in birth weight, estimated gestational age, and severity of illness. Administration of vancomycin was begun at a mean age of 5.4 +/- 2.9 days. Infants had mean serum vancomycin concentrations of 2.4 micrograms/ml, and received vancomycin for a mean of 11 +/- 7 days. No vancomycin-resistant organisms were detected in surveillance cultures during the 2-year study period. Twenty-four of seventy control infants, in comparison with 1 of 71 infants receiving vancomycin, had gram-positive bacteremia (p < 0.001). The addition of a low dose of vancomycin to alimentation fluids virtually eliminated the incidence of gram-positive bacteremia in an at-risk population of very low birth weight infants. However, the widespread use of vancomycin in total parenteral nutrition solution is not recommended until better data on the emergence of vancomycin-resistant organisms are available.

How vancomycin is used in Australasia--a survey

BACKGROUND

Vancomycin serum concentrations have been monitored over the last 30 years in an attempt to avoid dose-dependent toxicity and enhance efficacy. Current literature recommendations for peak and trough concentrations are usually in the range of 20-40 mg/L and 5-10 mg/L, respectively. Literature recommendations regarding the time at which peak concentrations are measured are highly variable, ranging from immediately after the end of the infusion to three hours post-dose.

AIMS

To identify how vancomycin dosing is being monitored and assess variability in the current practice.

METHODS

A survey of microbiology departments and infectious disease physicians in major Australasian hospitals was undertaken. The variability in the current practice was assessed by fitting mean recommendations to a two compartment Bayesian model.

RESULTS

Of the 83 (70%) who replied 71 (86%) monitored vancomycin concentrations. Fifty-four percent targeted peak concentrations within the range of 20-40 mg/L, and 73% targeted trough concentrations < or = 10 mg/L. The time of sampling of peak concentrations varied considerably ranging from immediately (12%) to 120 minutes (12%) post-infusion (median 30 minutes [40%]). The concentration-time curves resulting from three sets of mean recommendations ('peaks' drawn at: 0, 30 and 120 minutes aiming for a concentration of 35 mg/L with a trough concentration of 10 mg/L) were modelled using a two compartment Bayesian programme. The predicted true peak (maximum) concentrations ranged from 30 to 86 mg/L, despite aiming for identical target concentrations, indicating marked variation in the actual dosing practice.

CONCLUSIONS

There is thus considerable variation in the practice of vancomycin therapeutic monitoring which has a major effect on dosing. The main contributing factor is the variable timing of sampling peak concentrations.

Infections due to antibiotic-resistant gram-positive cocci

Gram-positive cocci are becoming increasingly resistant to traditionally used antimicrobial agents. Staphylococcus aureus, coagulase-negative staphylococci, the enterococcus, and Streptococcus pneumoniae are the most commonly encountered of such pathogens in clinical practice. Clinicians should be keenly aware of the usual types of infections that are caused by these organisms and the importance of documenting susceptibilities of infecting strains. The basic mechanisms of resistance should be familiar to clinicians so that an inappropriate empiric regimen will not be selected (e.g., addition of a beta-lactamase inhibitor for penicillin-resistant pneumococci). Vancomycin remains the agent of choice, sometimes in combination with gentamicin and/or rifampin, for most cases of infection due to these resistant gram-positive organisms. Last, increased efforts toward prevention, such as strict adherence to infection control measures, selective use of broad-spectrum antibiotics, and increased use of pneumococcal vaccine, may be useful to help stem the rising tide of infections due to resistant gram-positive cocci.

Enterococcus, an emerging pathogen

OBJECTIVE

To review the bacterial genus Enterococcus with respect to its epidemiology, specific infections in humans, mechanisms of resistance and tolerance, and antimicrobial treatment.

DATA SOURCES

A MEDLINE search of English-language journal articles published from 1977 to 1992 was completed. Articles published prior to 1977 were identified through Index Medicus and from references appearing in the bibliographies of other journal articles. Information also was acquired from abstracts, personal communication with infectious disease specialists with active research in the area of enterococcal infection, and conference proceedings.

STUDY SELECTION

In vitro data; animal models of enterococcal infection; case reports; and case-controlled, cohort, and randomized controlled trials in humans were evaluated for relevant information.

DATA EXTRACTION

Studies were evaluated by their methodologic strength (e.g., randomized controlled trial), reporting of clinically relevant outcomes (e.g., clinical response to antimicrobial therapy), statistical analyses, and accountability of all patients who entered the study.

DATA SYNTHESIS

The incidence of enterococcal infections has increased in recent years and enterococci are now the second most frequently reported nosocomial pathogens. Enterococcus faecalis is the pathogen responsible for most enterococcal infections seen today; it has been implicated as an important cause of endocarditis, bacteremia, urinary tract infections, and intraabdominal infections.

CONCLUSIONS

Enterococcal infection is of particular concern clinically because of its resistance to several antibiotics. Controlled comparative clinical trials of antimicrobial therapy in humans are lacking for several enterococcal infections. Therefore, the recommendations for antimicrobial therapy presented in this review are guidelines that reflect our current understanding of antibiotics used for enterococcal infection.

Vancomycin kinetics in plasma and synovial fluid following intravenous administration in horses

Vancomycin hydrochloride was infused intravenously (i.v.) over a 30-min period in five horses at doses of 6.6, 11.0 and 15.4 mg/kg. Vancomycin concentration in plasma and synovial fluid samples was measured using a polarization immunoassay. A pharmacokinetic model was developed to accommodate the special features of the present study. The data were described by a two compartment open model with synovial fluid as an additional compartment in exchange with plasma. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) were measured for Staphylococcus aureus and Enterococcus sp. using isolates from hospital patients. Based on the pharmacokinetic model and MIC/MBC data, a practical therapeutic protocol for vancomycin administration was established at doses of 4.3-7.5 mg/kg given as a 1-h infusion every 8 h.

Corynebacterium JK: a new pathogen in ventriculostomy infections

In the past decade, Corynebacterium JK has emerged as a pathogen in several distinct clinical settings, including sepsis in immunocompromised patients and prosthetic valve endocarditis. It is also recognized as a nosocomial pathogen in infections of prosthetic devices. We present a case of a patient with carcinomatous meningitis who developed a Corynebacterium JK infection of an internal ventriculostomy which was used for intraventricular chemotherapy. Treatment with systemic and intraventriculostomy vancomycin for three weeks resulted in bacteriologic resolution of the infection. Removal of the prosthetic device was not essential for cure in this patient. The clinical spectrum of infection with this organism and aspects of therapy are reviewed. As a greater awareness of the pathogenic nature of this organism develops, it is likely to be implicated as a causative agent in a variety of infections.

Antibiotic choices in surgical intensive care unit patients

Antibiotics have dramatically changed the care of the critically ill patient over the last 60 years. Patients with complex physiological conditions present with infectious processes requiring the effective use of antimicrobial drugs. In many situations, the inability to eradicate the infectious process is complicated by the progressive development of resistance among the causative organisms. Systemic antibiotic prophylaxis is warranted only for the prevention of wound infections. Regimens in these cases should use large doses of nontoxic antibiotics covering the spectrum of organisms likely to contaminate the wound. The duration of wound prophylaxis should be short, essentially covering only the period of active wound closure; this is usually less than 24 hours. Prevention of most other infections in the ICU depends on the recognition and correction of the various disturbances of host defenses. Topical antibiotic therapy may reduce the level of colonization for a few specific types of infection. Initial empiric antibiotic therapy should be started for clear indications. The antibiotics chosen should be those most likely to be effective against the probable organisms, those which have the lowest toxicity, and those with the smallest likelihood of inducing multiresistance. They must be adjusted promptly based on the microbiologic sensitivities observed. The realization that the physiology of critical illness may alter the normal relations between drug dosages and the tissue antibiotic levels obtained mandates a different approach to the treatment of these patients. The drug volumes of distribution are generally markedly expanded in these patients. Furthermore, these patients require high tissue antibiotic concentrations to improve the chances for successful therapy. Thus, the antibiotics selected must be capable of providing these levels without significant toxicity to the host. Therapy should be continued based on the clinical response observed. Premature cessation of effective therapy often results in relapse.

High incidence of vancomycin-associated leucopenia and neutropenia in a cardiothoracic surgical unit

A retrospective case record review was undertaken to determine the incidence of vancomycin-associated leucopenia in a cardiothoracic surgical unit. Forty-nine patients received 50 courses of vancomycin therapy. Nine patients (18%) developed reversible leucopenia (white cell count less than 4000 x 10(6)/l) or neutropenia (polymorphonuclear leucocyte count less than 1500 x 10(6)/l). Four patients (8%) had severe neutropenia (less than 1000 x 10(6)/l). The median total dosage associated with leucopenia and neutropenia was 30 g, range 22-56 g. The median duration of treatment in leucopenic and neutropenic patients was 22 days, range 6-28 days. The median recovery time to a normal white cell count was 4 days, range 1-11 days. Patients who developed leucopenia on vancomycin therapy did not differ from those who did not with respect to age, total vancomycin dose, length of therapy, underlying illness, incidence of cardiac surgery or use of concomitant medications. Vancomycin-associated leucopenia and neutropenia is common in patients with cardiothoracic infections, many of whom are on several other medications. White cell counts should be estimated regularly in such patients.

Vancomycin-aminoglycoside combinations in therapy of endocarditis caused by Enterococcus species and Streptococcus bovis

Between 1974 and 1986, five patients with enterococcal endocarditis (three of whom had a prosthetic valve) and three patients with Streptococcus bovis endocarditis were treated with a combination of vancomycin and an aminoglycoside for a mean duration of 40 days. This regimen was prescribed because of allergy to beta-lactam (n = 7) and/or failure of previous treatment (n = 4). Three of the eight patients underwent valve replacement. In the six evaluable patients cure was achieved with the vancomycin-aminoglycoside combination. An increase of the creatinine serum levels was observed in all cases but it was never necessary to discontinue treatment, adjustment of the vancomycin and aminoglycoside dosage according to the serum and/or serum creatinine levels allowing continuation of therapy.

Vancomycin ototoxicity and nephrotoxicity. A review

Vancomycin has been in clinical use as a potent antistaphylococcal antibiotic for over 30 years. Most reports of ototoxicity and nephrotoxicity have been associated with early, relatively impure, formulations of vancomycin. This paper reviews the literature concerning vancomycin ototoxocity and nephrotoxicity and the evidence for their correlation with the therapeutic serum concentration range. There have been 28 reports of vancomycin-associated ototoxicity published in the medical literature since 1958. It remains unclear whether any diminution in hearing is permanent or reversible. Few patients in the literature had follow-up audiometry and the hearing impairment tends to be at higher frequencies. Several authors reported peak serum vancomycin concentrations, but the exact time these were drawn with respect to the last dose is mostly unclear. In other reports, the 'peak' concentrations noted 3 to 6 hours after the last dose are probably indicative of much higher concentrations because of vancomycin's rapid phase of distribution. More than half the 57 cases of reported nephrotoxicity due to vancomycin occurred within the first 6 years of the drug's use. Many of these patients also had pre-existing renal dysfunction or were concomitantly receiving other nephrotoxic agents. It is unclear whether the coadministration of aminoglycosides produces a synergistic toxicity. The exact incidence of nephrotoxicity is uncertain, but is probably less with the current, relatively pure, product. The correlation of nephrotoxicity with certain serum vancomycin concentrations remains to be clarified. Other aspects also require clarification, such as when to draw samples to determine peak serum concentrations and whether or not routine measurements are necessary at all. In the absence of better guidelines, efforts should be made to tailor individual patient's regimens to produce peak and trough serum vancomycin concentrations to within the widely accepted ranges of 30 to 40 and 5 to 10 mg/L, respectively. In addition, the concomitant use of other potentially nephrotoxic and ototoxic agents should be avoided.

Vancomycin: a review

This article reviewed the past experience and updated the present data on vancomycin. In recent years, with the release of more purified preparations of vancomycin and new clinical problems facing the clinician (that is, increasing prevalence of serious methicillin-resistant staphylococcal infections; use of hemodialysis and CAPD; widespread use of prosthetic devices; aggressive chemotherapy), the indication for vancomycin use has increased dramatically. More information is needed on the distribution of vancomycin in body tissues and the incidence and mechanisms of toxicity. Close surveillance of in vitro susceptibility patterns will be necessary as widespread use of vancomycin continues to increase.

The enterococcus

In 1899, Thiercilin used the term “enterococcus” to describe microscopic organisms seen in pairs or short chains in feces. Later (in the 1930s) the name was used in a more restrictive sense for streptococci that had the hardy capacity to survive under extreme conditions.

Enterococci belong to a group D family of streptococci, as characterized by Lancefield in 1938. In contrast to other groups of streptococci, the group D antigen is not a wall carbohydrate but a glycerol teichoic acid containing glucose and D-alanine. This antigen appears to be related directly to the cytoplasm or plasma membrane.

Vancomycin-induced neutropenia

A case of vancomycin-induced neutropenia is presented with a review of other reported cases in the literature. A 59-year-old white female was started on vancomycin therapy for a chronic infection of a total left hip replacement. After 38 days of treatment, the patient developed a severe leukopenia with a white blood cell count of 1700/mm3 and the presence of only occasional neutrophils. Upon discontinuation of vancomycin, the leukocyte and neutrophil counts promptly increased with full recovery in one week. Subsequently, the patient was restarted on a five-day course of vancomycin at a lower dose that proved uneventful with no recurrence of neutropenia. It is unclear whether the neutropenia would have recurred with a longer course of vancomycin. A review of the literature suggests that an immunologic mechanism may be responsible for the reaction. Physicians and other health professionals should be aware that neutropenia is a potential reaction of patients receiving prolonged vancomycin treatment.

Vancomycin-induced neutropenia during treatment of osteomyelitis in an outpatient

A case of vancomycin-associated neutropenia occurring during long-term outpatient therapy with vancomycin is described. Pharmacokinetic studies demonstrated that the patient's vancomycin serum levels were within an acceptable range during treatment. Eighteen other reported cases of vancomycin-associated leukopenia are discussed in brief. An immunologic mechanism has been proposed but a clear understanding is lacking. Patients receiving long-term vancomycin therapy should have their white blood cell counts periodically monitored.

Comparison of methicillin-resistant and methicillin-sensitive Staphylococcus aureus bacteremia

Methicillin-resistant Staphylococcus aureus (MRSA) has become endemic in Detroit, accounting for 50% of bacteremias in heroin abusers. To identify the salient epidemiologic and clinical features of MRSA bacteremia, case-control studies were performed comparing 28 cases of MRSA bacteremia to 28 cases of methicillin-sensitive S. aureus (MSSA) bacteremia in intravenous drug abusers. Infective endocarditis was diagnosed in 46.4% (13 of 28). In endocarditis and nonendocarditis bacteremia alike, the duration of fever, length of hospitalization, need for surgery, and mortality rates were similar. A history of recent antimicrobial therapy, especially cephalosporins, was more common in the MRSA group (p = 0.006). Complications including neurologic, renal, vascular, and musculoskeletal manifestations were more common in the MSSA endocarditis patients than MRSA endocarditis patients, although this difference was not significant. Complications related to antibiotic therapy were similar for both groups. The case-control studies indicate that MRSA and MSSA are similar in their virulence as measured by duration of hospitalization, duration of fever, complications, and mortality.

Culture negative infective endocarditis

Twenty cases of culture negative infective endocarditis admitted to the Cardiology Department of Green Lane Hospital from 1959 to 1980 out of a total of 265 cases (7.5%), were analysed retrospectively. Cases were included only when adequate proof of endocarditis was available at surgery or postmortem. Indiscriminate use of antibiotics before taking blood cultures was the most common association with failure to obtain positive cultures, seen in 16 of the 20 patients described. Failure to obtain positive cultures in four cases was attributed to inadequate bacteriologic techniques before 1967. Where no antibiotics were given prior to collecting blood cultures and bacteriologic techniques were adequate, proven culture negative endocarditis was virtually unknown. When antibiotics have been given, repeated blood cultures are recommended following withdrawal of antibiotic for at least four days.

Comparative in vitro activities of teichomycin and vancomycin alone and in combination with rifampin and aminoglycosides against staphylococci and enterococci

The activity of teichomycin A2 was compared with that of vancomycin in vitro against clinical isolates of staphylococci and enterococci. Teichomycin A2 was more active than vancomycin active against all isolates tested. Synergistic studies also demonstrated that teichomycin A2 combined with rifampin is more active than vancomycin combined with rifampin against Staphylococcus aureus and Staphylococcus epidermidis isolates. Teichomycin A2, either singly or in combination with an aminoglycoside, was more active against Streptococcus faecalis isolates.

Ototoxicity of oral neomycin and vancomycin

In contrast to parenteral neomycin, which may result in severe and progressive ototoxicity, oral neomycin has been widely used for 25 years, and its index of safety has been regarded as high. Ototoxicity is viewed as an uncommon complication of oral neomycin most likely to occur in patients with renal failure or gastrointestinal inflammation. Two cases of ototoxicity resulting from oral neomycin are presented. Serial audiometric and neomycin blood level testing are suggested as a means of auditory monitoring in patients receiving the drug. A review of experience with oral vancomycin indicates that this drug has not been shown to cause ototoxicity.

In vitro activity of teichomycin and vancomycin alone and in combination with rifampin

The antibacterial activity of teichomycin, a glycopeptide antibiotic similar to vancomycin, has been evaluated in vitro and compared with that of vancomycin. Test strains included 130 staphylococci and 132 streptococci, with representatives of the major currently recognized species or groups, and lesser numbers of clostridia, propionibacteria, and group JK bacteria. Teichomycin was found to be more active than vancomycin. Its minimum inhibitory concentration (MIC) was two- to fourfold lower than that of vancomycin with staphylococci and anaerobic bacteria, and two- to eightfold lower with streptococci. No significant differences were observed with group JK bacteria. For most strains tested, minimum bactericidal concentrations (MBCs) of both teichomycin and vancomycin either equalled or exceeded by twofold the respective MICs. Higher MBC-to-MIC ratios were obtained for enterococci and pneumococci with both antibiotics. Both teichomycin and vancomycin showed similar in vitro interactions with rifampin in combination tests. Neither antagonism nor (with very few exceptions) synergism occurred.

Diphtheroid prosthetic valve endocarditis. A study of clinical features and infecting organisms

The clinical features of 19 patients with prosthetic valve endocarditis due to diphtheroids were studied. Infection was noted within 60 days of cardiac surgery in 12 (63 percent) patients. Prosthetic dysfunction and infection of the valve annulus was common (74 percent). Agar dilution minimal inhibitory concentrations for 18 diphtheroids isolated from patients with prosthetic valve endocarditis indicated that 88 percent were susceptible to gentamicin, amikacin, streptomycin, erythromycin and tetracycline; all strains were susceptible to vancomycin. In time-kill studies vancomycin was highly bactericidal as was gentamicin for susceptible strains. For gentamicin-susceptible strains, penicillin-gentamicin combinations were synergistic regardless of the susceptibility of the strains to penicillin. Bactericidal synergy of penicillin-gentamicin combinations was not seen with gentamicin-resistant strains. The biochemical and physiologic features of 20 strains were studied; with the exception of colonial morphology, 18 strains were found to be similar. Four strains were classified as belonging to the group JK by the Center for Disease Control (CDC) and 14 other strains fulfilled CDC criteria for group JK diphtheroids. A technique and criteria for single disc diffusion susceptibility testing are suggested.

Effect of meningitis and probenecid on the penetration of vancomycin into cerebrospinal fluid in rabbits

This study examined the effects of experimental pneumococcal meningitis and probenecid administration on the penetration of parenterally administered vancomycin into cerebrospinal fluid in rabbits. Bacterial killing was also examined in infected animals. Meningitis was induced by intracisternal inoculation of Streptococcus pneumoniae. Vancomycin was administered in a loading dose followed by a continuous intravenous infusion for 6 h. Serum and cerebrospinal fluid samples were obtained at 0, 2, 4, and 6 h for antibiotic assays and quantitative cultures. Meningitis significantly enhanced the penetration of vancomycin into cerebrospinal fluid, but probenecid administration had no effect. In normal rabbits, at 6 h the mean percent penetration (cerebrospinal fluid concentration/serum concentration x 100%) +/- the standard deviation was 1.9 +/- 0.9% in the nonprobenecid group (n = 10) and 1.9 +/- 1.1% in the probenecid group (n = 9). In rabbits with experimental pneumococcal meningitis, the mean percent penetration at 6 h was 3.9 +/- 2.6% in the nonprobenecid group (n = 11) and 4.3 +/- 2.1% in the probenecid group (n = 9). Mean bacterial titers in the cerebrospinal fluid of infected animals decreased by more than 3.0 log 10 colony-forming units per ml in both the nonprobenecid and the probenecid groups.