Bacterial endocarditis over prosthetic valves treated with trimethoprim-sulphamethoxazole combination

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.

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 for Treatment of Severe Staphylococcus aureus Infections

OBJECTIVE

To evaluate the role of trimethoprim/sulfamethoxazole (TMP/SMX) as an alternative to vancomycin for the treatment of severe Staphylococcus aureus infections.

DATA SOURCES

Clinical literature was accessed through MEDLINE (1966–February 2003) and EMBASE (1980–February 2003). Key search terms included trimethoprim/sulfamethoxazole combination and Staphylococcus aureus.

DATA SYNTHESIS

An evaluation of case reports, case series, and clinical studies focusing on the use of TMP/SMX for treatment of severe S. aureus infections was conducted. The majority of the reports indicate that TMP/SMX may be effective for the treatment of infections due to low bacterial burdens of susceptible strains of S. aureus.

CONCLUSIONS

In select infections, TMP/SMX may be a useful alternative to vancomycin for treatment of severe S. aureus infections. Additional randomized studies should be conducted comparing this agent with vancomycin and linezolid.

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.

Opportunistic endocarditis following open-heart surgery

The incidence of endocarditis following open-heart operations is declining, but the relative incidence of endocarditis by the opportunistic organisms, both bacterial and fungal, has increased. These "opportunists" require careful identification and sensitivity testing so that appropriate therapy can be planned. In cases of candida endocarditis, a positive precipitin test and elevated candida antibody titer may provide an earlier means of diagnosis than blood cultures. These patients should be treated promptly with adequate dosages of specific antimicrobial or antifungal agents. Reoperation should be considered early if there is evidence of valve dehiscence or embolic phenomena or if drug therapy fails to control the infection.