Persistent staphylococcal bacteremia in an intravenous drug abuser.

A patient with methicillin-resistant Staphylococcus aureus bacteremia received vancomycin (MIC = 0.8 microgram/ml, MBC = 15 micrograms/ml) and heparin simultaneously through the same intravenous line to treat a septic deep venous thrombosis. Bacteremia persisted for 7 days. Bacteremia terminated when the simultaneous infusion of heparin and vancomycin through the same line was stopped. This suggested that an interaction between vancomycin and heparin may have occurred, which resulted in a reduction in vancomycin activity. To test for such an interaction, mixtures of heparin and vancomycin in various concentrations were made and tested for antimicrobial activity against the organisms in the patient. A precipitate formed at the concentrations achieved in the intravenous lines, and when the vancomycin concentrations were measured by bioassay, a 50 to 60% reduction in activity was noted. In contrast, when these solutions were prepared and mixed at microgram concentrations, a precipitate was no longer observed, and antimicrobial activity was not reduced. Heparin appeared to interact unfavorably with vancomycin at the concentrations in the intravenous lines when these drugs were administered simultaneously to patients. This may be the cause of poor therapeutic responses to vancomycin in some patients, especially those infected with tolerant organisms.

Group A streptococcal bacteremia in intravenous drug abusers.

The clinical and microbiologic features of group A streptococcal bacteremia are described in 40 patients, all of whom were seen between January 1982 and June 1983 and all of whom were intravenous drug abusers. Eleven patients had endocarditis (two with left-sided and nine with right-sided), and 29 patients had bacteremia without endocardial involvement. Twenty-seven of the 29 patients without endocarditis had soft tissue infections, primarily groin abscesses. Constitutional symptoms were more severe in patients with endocarditis. The two patients with left-sided endocarditis died despite antimicrobial therapy; all nine patients with right-sided endocarditis and all 29 patients without endocarditis were cured of their infection. A predominant strain of group A streptococcus was identified by serologic typing, suggesting a common source for these cases.

Effect of therapy with latamoxef (moxalactam) on carriage of Clostridium difficile.

Twenty-seven patients receiving latamoxef (moxalactam) as a single antimicrobial agent were studied prospectively for Clostridium difficile carriage and development of diarrhoea or colitis. Stools were available prior to therapy from only seven patients, one of whom (14.3%) was an asymptomatic carrier. None of twelve patients studied during therapy were carriers. Seven of 27 patients (25.9%) were colonized with Cl. difficile after completion of latamoxef therapy, and three patients had cytotoxin positive stools. Two patients with cytotoxin grew Cl difficile from stools and one patient was culture negative. Only one patient, who had both culture and cytotoxin positive stools, had profuse diarrhoea. Cl. difficile clinical isolates were only moderately susceptible to latamoxef in vitro. Hamsters given moxalactam developed caecitis. Patients receiving latamoxef, or third generation cephalosporins, may be at increased risk of development of Cl. difficile associated diarrhoea and should be followed closely for this complication, especially after therapy has been discontinued.

Case report. Brucella canis bacteremia: a case with negative B canis agglutinins.

Naturally acquired Brucella canis infection is believed to be uncommon, but is not readily diagnosed. A 55-year-old woman developed fever, abdominal pain, malaise, weakness, and anorexia eight weeks after her dog delivered stillborn pups. Blood cultures yielded B canis. Specific B canis agglutinins were negative initially and remained negative during convalescence. Therapy with tetracycline and streptomycin was successful but was associated with a probable Jarisch-Herxheimer reaction.