Dah Hsi Ho

Susceptibility surveillance among gram-negative bacilli at a cancer center

We conducted a survey of susceptibility among 758 gram-negative bacilli (GNB; collected from cancer patients over a 3-month period) to commonly used antibiotics. The overall resistance among GNB was least for piperacillin/tazobactam and meropenem (5 and 6%, respectively) followed by cefepime (8%), imipenem (9%), amikacin (12%), ofloxacin (13%), ciprofloxacin, ceftazidime and ticarcillin/clavulanate (14% each), aztreonam (18%) and tobramycin (24%). In comparison to data on antibiotic resistance to ceftazidime, imipenem, ciprofloxacin and aztreonam in similar studies in 1985 and 1994, resistance has significantly increased to all four antibiotic classes. Based on our current study, meropenem, cefepime, imipenem and piperacillin/tazobactam would be the most appropriate choices in our institution for empiric therapy of GNB infections in febrile neutropenic patients.

Survey of antibiotic susceptibility among gram-negative bacilli at a cancer hospital

A survey was conducted of the susceptibility of gram-negative bacilli to selected broad-spectrum antibiotics. The organisms were isolated from all patient specimens submitted to the routine microbiology laboratory during two three-month periods. Overall, the least resistance was observed against imipenem and ciprofloxacin. Considering all of the gram-negative bacilli, differences in susceptibilities to the other antibiotics (aztreonam, cefoperazone, ceftazidime, piperacillin) were minimal. Significant increases in resistance to some antibiotics occurred during the latter period.

In vitro studies of BMY-28142, a new broad-spectrum cephalosporin.

BMY-28142 was compared with other broad-spectrum antibiotics against gram-positive cocci and gram-negative bacilli. BMY-28142 was highly active against all gram-negative bacilli and especially against Enterobacter cloacae, Serratia marcescens, and Morganella morganii. Its in vitro activity suggests that BMY-28142 should prove to be useful for the treatment of gram-negative bacillary infections.

Susceptibilities of bacterial isolates from patients with cancer to levofloxacin and other quinolones.

The antibacterial activity of levofloxacin was compared with those of ofloxacin and ciprofloxacin against bacterial isolates from patients with cancer. In general, levofloxacin was as active or was twofold more active than ofloxacin and was two- to fourfold less active than ciprofloxacin against most gram-negative pathogens. Against Pseudomonas aeruginosa, ciprofloxacin was the most active agent tested (MIC for 90% of isolates tested, 1.0 microgram/ml). Overall, all three agents had similar activities against gram-positive organisms and were moderately active against methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci, Streptococcus species, and Enterococcus species.

In vitro antimicrobial activity of moxifloxacin compared to other quinolones against recent clinical bacterial isolates from hospitalized and community-based cancer patients.

The in vitro spectrum of moxifloxacin (a C-8-methoxyquinolone) was compared to that of ciprofloxacin and levofloxacin against 924 recent clinical isolates from cancer patients. Moxifloxacin was more active than the comparator agents against Gram-positive pathogens, with potent activity against Aerococcus spp., Listeria monocytogenes, Micrococcus spp., Rhodococcus equi, and Stomatococcus mucilaginous, methicillin-susceptible Staphylococcus spp., all beta hemolytic streptococci, viridans streptococci and Streptococcus pneumoniae. It also had good to moderate activity against Bacillus spp., Corynebacterium spp., Enterococcus faecalis, and methicillin-resistant staphylococci. Although ciprofloxacin was the most active agent tested against the Enterobacteriaceae, moxifloxacin inhibited the majority of these isolates at < or =2.0 microg/ml. Moxifloxacin was the least active of the three agents tested against Pseudomonas aeruginosa, but had significant activity against other non-fermentative Gram-negative bacilli including Acinetobacter spp., Flavobacterium spp., Pseudomonas spp. other than P. aeruginosa, and Stenotrophomonas maltophilia. The overall broad spectrum of moxifloxacin, and its availability for both oral and parenteral administration, warrants its evaluation for the prevention and treatment of infections in cancer patients.

Survey of Antibiotic Susceptibility among Gram-Negative Bacilli at a Cancer Center

A survey of the susceptibility of gram-negative bacilli isolated from cancer patients to broad-spectrum antimicrobial agents was conducted. The organisms were isolated from all patient specimens submitted to the microbiology laboratory during a 3-month study period. Overall, the least resistance was observed against cefoperazone/sulbactam, ciprofloxacin, and imipenem. Of these, cefoperazone/sulbactam has had limited usage at our institution. Drugs used more frequently (piperacillin, aztreonam, cefoperazone, ceftazidime) were associated with greater levels of resistance. Imipenem and ciprofloxacin have enjoyed wide usage but the level of resistance remains low.

In vitro activities of antimicrobial agents against clinical isolates of Flavimonas oryzihabitans obtained from patients with cancer.

We evaluated the in vitro activities of 21 different antimicrobial agents against nine clinical isolates of Flavimonas oryzihabitans obtained from patients with cancer. The organisms were susceptible to most agents commonly used for the empiric therapy (aminoglycosides, ureidopenicillins, extended-spectrum cephalosporins, monobactams, and carbapenems) and prevention of infections (quinolones and trimethoprim-sulfamethoxazole) in this patient population.

In vitro assessment of sulbactam plus cefoperazone in the treatment of bacteria isolated from cancer patients

Cefoperazone is a broad-spectrum cephalosporin that has been used extensively to treat infections in cancer patients. A recent survey demonstrated only a 6% resistance to this drug among Gram-negative bacteria. The combination of cefoperazone plus sulbactam was studied in vitro against consecutive isolates causing bacteremia in cancer patients as well as those selected for resistance to cefoperazone. Both a fixed ratio of sulbactam/cefoperazone (2:1 w/w) and selected concentrations of sulbactam (2, 4, 8, and 16 micrograms/ml) were studied. Sulbactam was shown to increase the susceptibility of various unselected Gram-negative bacilli; this effect increased with larger concentrations of sulbactam. The addition of sulbactam at optimum concentration levels made 29 of 65 cefoperazone-resistant Gram-negative bacilli susceptible. This effect was seen most markedly for Acinetobacter spp.

In vitro activity of WIN 49375 compared with those of other antibiotics in isolates from cancer patients.

The activity of WIN 49375 [6-fluoro-1, 4-dihydro-1-(methylamino)-7-(4-methyl-1-piperazinyl)-4-oxo-3- quinolinecarboxylic acid], a new synthetic quinolone, was tested in vitro against 587 clinical isolates. The MICs for 90% of isolates of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were 0.20, 1.56, and 0.39 microgram/ml, respectively. The MICs for 90% of isolates of Pseudomonas aeruginosa and Serratia marcescens were both 3.12 micrograms/ml. WIN 49375 was minimally active against gram-positive cocci. Its in vitro activity suggests that it may be useful for the treatment of gram-negative bacillary infections.

In vitro activity of fleroxacin (Ro23-6240), a new fluorinated 4-quinolone against isolates from cancer patients

The in vitro activity of Fleroxacin (Ro23-6240; AM 833), a new fluorinated 4-quinolone, was compared to that of ciprofloxacin, enoxacin and A-56620, against 747 isolates from cancer patients. Fleroxacin inhibited more than 90% of Enterobacteriacea isolates at a concentration of less than or equal to 0.25 micrograms/ml. It was also extremely active against Aeromonas hydrophila and Haemophilus influenzae isolates with MIC90 values of 0.12 and 0.06 micrograms/ml, respectively. The MIC90 for Acinetobacter spp. was 1.0 micrograms/ml, for Pseudomonas aeruginosa and Pseudomonas fluorescens 4.0 micrograms/ml, and for other Pseudomonas spp., 8.0 micrograms/ml. Staphylococcus aureus isolates including methicillin-resistant strains were inhibited by less than or equal to 1.0 microgram/ml. The MIC90 for three different species of coagulase-negative Staphylococci was 1.0 microgram/ml. Streptococcal species required 8-16 micrograms/ml for inhibition. Fleroxacin was also active against group JK-diphtheroids and Bacillus cereus. The overall activity of fleroxacin was similar to that of enoxacin and less than that of A-56620 and ciprofloxacin.