Trimethoprim-sulphamethoxazole treatment in staphylococcal endocarditis and gram-negative septicemia

A new strategy to fight antimicrobial resistance: the revival of old antibiotics

The increasing prevalence of hospital and community-acquired infections caused by multidrug-resistant (MDR) bacterial pathogens is limiting the options for effective antibiotic therapy. Moreover, this alarming spread of antimicrobial resistance has not been paralleled by the development of novel antimicrobials. Resistance to the scarce new antibiotics is also emerging. In this context, the rational use of older antibiotics could represent an alternative to the treatment of MDR bacterial pathogens. It would help to optimize the armamentarium of antibiotics in the way to preserve new antibiotics and avoid the prescription of molecules known to favor the spread of resistance (i.e., quinolones). Furthermore, in a global economical perspective, this could represent a useful public health orientation knowing that several of these cheapest “forgotten” antibiotics are not available in many countries. We will review here the successful treatment of MDR bacterial infections with the use of old antibiotics and discuss their place in current practice.

Revisiting "older" antimicrobials in the era of multidrug resistance

Infections due to multidrug-resistant (MDR) organisms continue to increase, and the antimicrobial pipeline remains unacceptably lean. Given this challenge, it is has become necessary to use older antimicrobials for treatment of MDR pathogens despite concerns regarding toxicity and the lack of clinical efficacy data. In some cases, older antimicrobials offer potential advantages compared with new agents, including lower cost and better in vitro activity. In this review, we focus on the pharmacology, in vitro activity, and clinical experience of older agents, including colistin, minocycline, trimethoprim-sulfamethoxazole, and fosfomycin. We also discuss some new antimicrobial agents that are used to treat MDR pathogens. As MDR pathogens continue to outpace the development of new antimicrobials, it will become imperative to develop strategies regarding the optimal use of older agents in terms of monotherapy versus combination therapy, dosing regimens, and treatment of invasive infections caused by these pathogens.

Co-trimoxazole versus vancomycin for the treatment of methicillin-resistant Staphylococcus aureus bacteraemia: a retrospective cohort study

OBJECTIVES

To evaluate the efficacy and safety of co-trimoxazole versus that of vancomycin in adults with methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia.

PATIENTS AND METHODS

Retrospective matched cohort study. Thirty-eight patients with MRSA bacteraemia, treated with co-trimoxazole as the main therapeutic agent, were matched with 76 patients treated with vancomycin as the main agent. The groups were matched for age, sex, functional status, endovascular source of infection, appropriateness of empirical antibiotic therapy, presence of a foreign body, sepsis severity and Charlson score. The outcomes collected were 30 day mortality, persistent bacteraemia [defined as positive blood culture (BC) >14 days after the first positive BC, but within 30 days], relapse (defined as recurrence of the same phenotype >30 days after the first positive BC within 12 months) and adverse events.

RESULTS

The groups were well matched. Thirty day mortality was not significantly different between the groups [co-trimoxazole 13/38 (34.2%); vancomycin 31/76 (40.8%); odds ratio 0.76, 95% confidence interval 0.34-1.7]. There was only one case of relapse in the co-trimoxazole group (2.6%) compared with nine cases in the vancomycin group (11.8%). Incidence of relapse or persistent bacteraemia was lower in the co-trimoxazole group (3/38, 7.9%) than in the vancomycin group (13/76, 17.1%), although the difference was not statistically significant (P = 0.182). Development of renal failure was similar [co-trimoxazole 11/38 (28.9%); vancomycin 21/76 (27.6%)].

CONCLUSIONS

Within the limitations of a small retrospective study, co-trimoxazole had a safety and efficacy profile similar to that of vancomycin and may offer an attractive additional therapeutic option for MRSA bacteraemia. A prospective, randomized controlled trial is warranted.

Trimethoprim-sulfamethoxazole as a viable treatment option for infections caused by methicillin-resistant Staphylococcus aureus

OBJECTIVE

To review available data regarding the efficacy of trimethoprim-sulfamethoxazole (TMP-SMX) for the treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA).

DATA SOURCES

A MEDLINE search was performed (January 1966-December 2003) using the search terms Staphylococcus aureus , sulfamethoxazole, trimethoprim, co-trimoxazole, and methicillin resistance. Abstracts from infectious diseases meetings also were reviewed.

DATA SYNTHESIS

The reported rate of TMP-SMX resistance in S. aureus is highly variable. From a mechanistic standpoint, TMP-SMX resistance among MRSA appears to be distinct from multidrug resistance, although some anecdotal reports suggest otherwise. Clonal outbreaks of MRSA resistant to TMP-SMX have been described; of these, the Brazilian clone has more often been resistant to TMP-SMX than the Iberian clone. Rates of TMP-SMX resistance are particularly high in institutions serving large numbers of patients infected by the human immunodeficiency virus, due to increased exposure for Pneumocystis prophylaxis. Limited studies and case reports have found TMP-SMX useful against infections caused by MRSA.

CONCLUSIONS

A large body of anecdotal data, but only one randomized clinical trial, indicates the effectiveness of TMP-SMX as a treatment for MRSA infections. Double-blind, randomized controlled trials are needed to compare the two available oral agents-TMP-SMX and linezolid-against MRSA.

Guidelines for the antibiotic treatment of endocarditis in adults: report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, Coxiella and Bartonella) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.

Treatment of experimental endocarditis due to methicillin-susceptible or methicillin-resistant Staphylococcus aureus with trimethoprim-sulfamethoxazole and antibiotics that inhibit cell wall synthesis

Using two strains of Staphylococcus aureus, one susceptible and one heterogeneously resistant to methicillin, for which MICs and MBCs of trimethoprim-sulfamethoxazole (TMP-SMX) were 0.06 and 0.06 micrograms/ml and 0.06 and 0.25 microgram/ml, respectively (concentrations are those of TMP), we studied the efficacies of TMP-SMX and cloxacillin, teicoplanin, and vancomycin for treatment of experimental staphylococcal endocarditis. Rabbits were treated with dosages of TMP-SMX selected to achieve concentrations in serum equivalent to that obtained in humans treated for Pneumocystis carinii pneumonia. The overall mortality rate of rabbits treated with TMP-SMX was 84% at day 3, not different from that of the control groups (P > 0.1). No sterile vegetations were observed to be present in control groups or in animals treated with TMP-SMX. However, 26, 60, and 75% of rabbits treated with teicoplanin, cloxacillin, and vancomycin, respectively, showed sterile vegetations. For methicillin-susceptible S. aureus (MSSA), the mean vegetation counts were not significantly different between the control group and the group treated with TMP-SMX (P > 0.1). For methicillin-resistant S. aureus (MRSA), treatment with TMP-SMX was more effective than no therapy, decreasing the number of organisms in vegetations (P < 0.01). For both strains, therapy with cloxacillin and therapy with teicoplanin or vancomycin were significantly more effective than therapy with TMP-SMX. Despite high concentrations of teicoplanin in serum which exceeded MBCs for staphylococci more than 50 times at the peak and 10 times at the trough, therapy with cloxacillin or vancomycin was superior to therapy with teicoplanin against both MSSA and MRSA. These data do not support the use of TMP-SMX in treatment of endocarditis and other severe staphylococcal infections with high bacterial counts.

In vitro and in vivo efficacy of the combination trimethoprim-sulfamethoxazole against clinical isolates of methicillin-resistant Staphylococcus aureus

The in vitro susceptibilities of 16 independent, geographically distinct clinical isolates of methicillin-resistant Staphylococcus aureus to trimethoprim (TMP) in combination with sulfamethoxazole (SMX) were evaluated. Although methicillin-resistant S. aureus strains appear to be universally resistant to SMX, the combination TMP-SMX was found to be synergistic in vitro (in combination, the MICs of both drugs decreased 6- to 25-fold) as well as in vivo (5- to 6-fold reduction in TMP at 50% effective doses).

Prosthetic valve endocarditis due to methicillin-resistant Staphylococcus epidermidis and Micrococcus species successfully treated with rifampicin combined with other antibiotics

Two patients with prosthetic valve endocarditis due to methicillin-resistant Gram-positive cocci (Staphylococcus epidermidis and Micrococcus spp.) are described. They were successfully treated with rifampicin combined first with an aminoglycoside and later with co-trimoxazole or co-trimoxazole plus vancomycin. The addition of rifampicin to these antibiotics resulted in enhanced serum bactericidal activity. High doses of rifampicin (1200-1800 mg) for 7-8 weeks did not cause any serious side-effect. Surgery was not required. During surveillance for more than 2 years endocarditis did not recur.

Trimethoprim-sulfamethoxazole treatment of multiantibiotic-resistant staphylococcal endocarditis and meningitis

The successful treatment of a multiantibiotic-resistant Staphylococcus aureus endocarditis and meningitis with oral trimethoprim-sulfamethoxazole is reported.

Intravenous trimethoprim-sulfamethoxazole alone or combined with tobramycin for infections in cancer patients

A total of 120 episodes of infection in 113 cancer patients were treated with intravenous trimethoprim-sulfamethoxazole (TMP-SMX) alone (92 episodes) or with TMP-SMX plus continuous infusion tobramycin (28 episodes). The overall response rates were 47% and 75%, respectively. The majority of episodes had failed to respond to prior antibiotics. Pneumonia was the most common infection, and Klebsiella pneumoniae was the most common pathogen. TMP-SMX plus tobramycin cured 86% of episodes of septicemia and 76% of episodes of pneumonia, whereas TMP-SMX alone cured 20% and 42%, respectively. The initial neutrophil count did not appear critical in determining the outcome of infection. It was the change in the neutrophil count during the infection that appeared important. The outcome of infection was less favorable where abnormal renal and/or hepatic functions were documented. The sensitivity of the organism in vitro to TMP-SMX and/or tobramycin correlated well with the in vivo response. Intravenous TMP-SMX was well tolerated with a 4% incidence of reversible toxicity. A 15% incidence of renal toxicity was attributable to tobramycin. Intravenous TMP-SMX appears to be useful antimicrobial regimen for the therapy of infections caused by susceptible organisms in cancer patients.

Bacterial endocarditis. II. A prospective study with clinical, laboratory and therapeutic observations

In a prospective study 31 cases of proved and 10 of highly suspected bacterial endocarditis were analysed. Valve incompetence was the usual consequence but stenosis occurred in 3 cases, all fatal. Congestive heart failure developed in two-thirds. Secondary manifestations were common and as often caused by alpha-streptococci as by other bacteria. Initial antibiotic treatment was mainly applied according to a fixed schedule, generally with continuous intravenous infusion, followed by oral therapy. In 10 patients, the infection was still active after 6 weeks of therapy. Therefore, we now use intermittent injections or infusions for at least 4--6 weeks. Within a year, 9 patients died from uncontrolled infection together with congestive heart failure, and 1 from heart failure and active chronic endocarditis. In 4, myocardial abscesses or inflammations were found. All 10 had underlying factors or advanced stages of the disease. Of 18 patients with alpha-streptococci or enterococci none died from endocarditis, as against 10 of 23 with other or unknown bacteria. Follow-up yielded valuable information on one-third of the patients. The mortality during the initial hospital stay was 22%, after 1 year 24% and after 5 years 39%.