Comparative in vitro activity of the new oral cephalosporin cefixime.

Cefixime was 8 to 10 times more active than cefaclor and augmentin against isolates of Escherichia coli, Klebsiella pneumoniae and Salmonella typhi, MIC90 values ranging from 0.06 to 0.25 micrograms/ml. However, none of these three drugs was particularly active against isolates of more resistant gram-negative bacilli such as Enterobacter, Serratia, Citrobacter, Acinetobacter, Providencia and Achromobacter spp. The lowest MIC values for gram-negative bacilli were seen with ciprofloxacin, except for isolates of Acinetobacter, where cotrimoxazole was the most active of the five drugs studied. Augmentin and ciprofloxacin exhibited the lowest MICs for isolates of streptococci and corynebacteria. Although cefixime may be among the most active oral beta-lactam drugs, it does not appear to be useful for treatment of infections caused by more resistant gram-negative bacilli.

Comparison of a novel trimethoprim-sulfamethoxazole-containing medium (XT80) with kanamycin agar for isolation of antibiotic-resistant organisms from stool and rectal cultures of marrow transplant patients.

A new medium (XT80) containing trimethoprim-sulfamethoxazole (TMP-SMZ) was characterized and compared with kanamycin-containing tryptic soy agar (KA) for the recovery of multiply resistant organisms (MRO) in rectal and stool cultures. Cultures from 151 patients hospitalized for bone marrow transplantation were screened for MRO. A total of 366 MRO were recovered from 702 cultures on 94 patients during a 6-month period. XT80 detected more gram-negative bacilli and Corynebacterium spp. than KA. Detection of Staphylococcus spp. was equivalent for the two media. Multiple-antibiotic resistance, defined as resistance to three or more classes of antibiotics, was confirmed by standard agar disk diffusion susceptibility testing. Growth on XT80 correctly identified heteroresistant strains of methicillin-resistant Staphylococcus spp. XT80 more rapidly detected thymidine-dependent mutants of Staphylococcus spp. and members of the family Enterobacteriaceae. Lipophilic Corynebacterium spp., including Corynebacterium group JK, also were more readily detected with XT80. TMP-SMZ given as prophylaxis against Pneumocystis carinii infection exerts a selective pressure on organisms that colonize immunocompromised patients and appears to select for colonization with MRO. Colonization with MRO preceded infection for 94% of 36 patients who developed bacteremia. XT80 is a useful screening tool; growth on this medium correlates closely with resistance to TMP-SMZ and is as accurate a predictor as KA for the carriage of MRO.