Are clinical laboratories in California accurately reporting vancomycin-resistant enterococci?

In order to determine whether hospital-based clinical laboratories conducting active surveillance for vancomycin-resistant enterococci in three San Francisco Bay area counties (San Francisco, Alameda, and Contra Costa counties) were accurately reporting vancomycin resistance, five vancomycin-resistant enterococcal strains and one vancomycin-susceptible beta-lactamase-producing enterococcus were sent to 31 of 32 (97%) laboratories conducting surveillance. Each strain was tested by the laboratory's routine antimicrobial susceptibility testing method. An Enterococcus faecium strain with high-level resistance to vancomycin (MIC, 512 microg/ml) was correctly reported as resistant by 100% of laboratories; an E. faecium strain with moderate-level resistance (MIC, 64 microg/ml) was correctly reported as resistant by 91% of laboratories; two Enterococcus faecalis strains with low-level resistance (MICs, 32 microg/ml) were correctly reported as resistant by 97 and 56% of laboratories, respectively. An Enterococcus gallinarum strain with intrinsic low-level resistance (MIC, 8 microg/ml) was correctly reported as intermediate by 50% of laboratories. A beta-lactamase-producing E. faecalis isolate was correctly identified as susceptible to vancomycin by 100% of laboratories and as resistant to penicillin and ampicillin by 68 and 44% of laboratories, respectively; all 23 (74%) laboratories that tested for beta-lactamase recognized that it was a beta-lactamase producer. This survey indicated that for clinically significant enterococcal isolates, laboratories in the San Francisco Bay area have problems in detecting low- to moderate-level but not high-level vancomycin resistance. Increasing accuracy of detection and prompt reporting of these isolates and investigation of cases are the next steps in the battle for control of the spread of vancomycin resistance.     

Comparative antimicrobial activity of RP 59,500 (quinupristin-dalfopristin), the first semisynthetic injectable streptgramin, against gram-positive cocci and other recent clinical pathogens

RP 59,500 (Quinupristin-Dalfopristin) is the first semisynthetic injectable streptogramin antimicrobial agent, which is a combination of quinupristin and dalfopristin in a 30:70 ratio. The components of RP 59,500 act synergically to provide bactericidal activity through action at different sites on bacterial ribosomes. In the present study, the antimicrobial activity of RP 59,500 was compared with those of four macrolides (erythromycin, clarithromycin, azithromycin, roxithromycin). Susceptibility testing was carried out by microdilution method on 303 strains of 10 species, especially antibiotic-resistant Gram-positive cocci. RP 59,500 was active against a wide range of Gram-positive cocci including methicillin-resistant Staphylococci and penicillin-resistant Streptococcus pneumoniae. The MICs90 of RP 59,500 against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis were both 0.25 microgram/ml, although those of four macrolides were higher than 32 micrograms/ml. The MICs90 of RP 59,500 against penicillin-sensitive, -intermediate and -resistant S. pneumoniae were all 0.5 microgram/ml, although those of four macrolides against penicillin-resistant S. pneumoniae were higher than 32 micrograms/ml. RP 59,500 also exhibited equivalent activities to the four macrolides against strains of Streptococcus pyogenes. Streptococcus agalactiae and Moraxella catarrhalis. RP 59,500 exhibited the highest activities against Enterococcus faecalis, Enterococcus faecium and Enterococcus avium strains which are intrinsically resistant to most antimicrobial agents. No cross-resistance was observed between RP 59,500 and the four macrolides, which will merit attention in future clinical trials of the agent. The effect of human serum on the MIC of RP 59,500 was studied with strains of S. aureus, S. epidermidis and E. faecalis. The presence of 20% (V/V) serum had little or no effect on the MIC, although 50% (V/V) serum increased MICs by 4-8 folds. Laboratory-induced resistance to RP 59,500 occurred in a stepwise fashion in broth cultures of S. aureus, S. epidermidis and E. facalis strains and the induction rate was slow and no more than four fold increases were observed. Population analysis was performed on RP 59,500 and the reference macrolides against S. aureus ATCC 25,923 strain. Although low frequencies (less than 0.01%) of resistant sub-population were detected with EM, CAM, AZM and RXM, no RP 59,500-resistant sub-population was detected in this study.     

Influence of erythromycin resistance, inoculum growth phase, and incubation time on assessment of the bactericidal activity of RP 59500 (quinupristin-dalfopristin) against vancomycin-resistant Enterococcus faecium

RP 59500, a mixture of two semisynthetic streptogramin antibiotics (quinupristin and dalfopristin), is one of a few investigational agents currently in clinical trials with inhibitory activity against multiple-drug-resistant strains of Enterococcus faecium. We evaluated the bactericidal activity of this antimicrobial against 30 recent clinical isolates of vancomycin-resistant E. faecium, including 23 erythromycin-resistant (MIC, >256 microg/ml) and 7 erythromycin-intermediate (MIC, 2 to 4 microg/ml) strains. All isolates were inhibited by RP 59500 at 0.25 to 1.0 microg/ml. The bactericidal activity of RP 59500 was markedly influenced by the erythromycin susceptibility of the strains and by several technical factors, such as inoculum growth phase and time of incubation of counting plates. As determined by time-kill methods, RP 59500 at a concentration of 2 or 8 microg/ml failed to kill erythromycin-resistant organisms under any conditions. Bactericidal activity was observed against all seven erythromycin-intermediate isolates when log-phase inocula were used and the cells were counted after 48 h of incubation (mean reductions in viable bacteria for RP 59500 at concentrations of 2 and 8 microg/ml, 3.45 and 3.50 log10 CFU/ml, respectively), but killing was diminished when the plates were examined at 72 h (mean killing, 3.06 and 2.95 log10, CFU/ml, respectively). No bactericidal activity was observed when stationary-phase cultures were used. On the basis of these data, we expect that bactericidal activity of RP 59500 against the multiple-drug-resistant E. faecium strains currently encountered would be distinctly uncommon.     

Antimicrobial activity of quinupristin-dalfopristin (RP 59500, Synercid) tested against over 28,000 recent clinical isolates from 200 medical centers in the United States and Canada

A total of 200 medical center laboratories in the USA and Canada contributed results of testing quinupristin-dalfopristin, a streptogramin combination (formerly RP 59500 or Synercid), against 28,029 Gram-positive cocci. Standardized tests [disk diffusion, broth microdilution, Etest (AB BIODISK, Solna, Sweden)] were utilized and validated by concurrent quality control tests. Remarkable agreement was obtained between test method results for characterizing the collection by the important emerging resistances: 1) oxacillin resistance among Staphylococcus aureus (41.0 to 43.7%); 2) vancomycin resistance among Enterococcus faecium (50.0 to 52.0%); and 3) the penicillin nonsusceptible rate for pneumococci (31.1% overall, with 10.6% at MICs of > or = 2 micrograms/mL). The quinupristin-dalfopristin MIC90 for oxacillin-susceptible and -resistant S. aureus was 0.5 microgram/mL and 1 microgram/mL, respectively. The quinupristin-dalfopristin MIC90 for vancomycin-resistant E. faecium was 1 microgram/mL, and only 0.2% of isolates were resistant. Other Enterococcus species were generally not susceptible to the streptogramin combination but were usually inhibited by ampicillin (86 to 97% susceptible; MIC50, 1.0 microgram/mL) or vancomycin (86 to 95%; MIC50, 1.0 microgram/mL). Among all tested enterococci, the rate of vancomycin resistance was 16.2%. The quinupristin-dalfopristin MIC90 (0.75 microgram/mL) for 4,626 tested Streptococcus pneumoniae strains was not influenced by the penicillin or macrolide susceptibility patterns. When five regions in the USA and Canada were analyzed for significant streptogramin and other antimicrobial spectrum differences, only the Farwest region had lower numbers of streptogramin-susceptible E. faecium. Canadian strains were generally more susceptible to all drugs except chloramphenicol and doxycycline when tested against E. faecalis (73% and 89% susceptible, respectively). The U.S. Southeast region had S. pneumoniae strains less susceptible to macrolides (73%) but had more susceptibility among E. faecium isolates tested against vancomycin and ampicillin. The Northeast region of the USA had the greatest rate of vancomycin resistance among enterococci. Strains retested by the monitor because of quinupristin-dalfopristin resistance (MICs, > or = 4 micrograms/mL) were generally not confirmed (2.2% validation), and only 0.2% of E. faecium isolates were identified as truly resistant. The most common errors were: 1) species misidentification (28.0%); 2) incorrect susceptibility results (65.6%); and 3) mixed cultures (4.3%) tested by participants. Overall, quinupristin-dalfopristin was consistently active (> or = 90% susceptible) against major Gram-positive pathogens in North America, regardless of resistance patterns to other drug classes and geographic location of their isolation.     

Antipneumococcal activities of RP 59500 (quinupristin-dalfopristin), penicillin G, erythromycin, and sparfloxacin determined by MIC and rapid time-kill methodologies

Previous time-kill studies have shown that RP 59500 is rapidly bactericidal against pneumococci. To extend these findings, the activities of RP 59500, its two components RP 57669 RP 54476, penicillin G, erythromycin and sparfloxacin against 26 penicillin-susceptible, 25 penicillin-intermediate, and 25 penicillin-intermediate, and 25 penicillin-resistant pneumococci were determined by the agar dilution MIC and the time-kill testing methodologies within 10 min (ca. 0.2 h) and at 1 and 2 h. Respective agar dilution MICs at which 90% of isolates are inhibited for penicillin-susceptible, -intermediate, and -resistant strains were as follows: penicillin G, 0.03, 1, and 4 micrograms/ml;RP 59500, 1, 1, and 1 microgram/ml; RP 57669, 8, 32, and 16 micrograms/ml; RP 54476, > 128, > 128, and > 128 micrograms/ml; erythromycin, 0.06, 2, and > 128 micrograms/ml; and sparfloxacin, 1, 0.5, and 0.5 microgram/ml. RP 59500 was equally active (MIC at which 90% of isolates are inhibited, 1.0 microgram/ml) against erythromycin-susceptible and -resistant strains. Time-kill testing results showed that only RP 59500 at one to four times the MIC killed pneumococci at 0.2 h; RP 59500 was also the most active compound at 1 and 2 h. By comparison, penicillin and sparfloxacin at one, two, and four times the MICs reduced the original inoculum by > or = 1 log at 2 h for 46, 80, and 95% and for 50, 72, and 86% of strains, respectively. The killing activity of RP 59500 was the same against erythromycin-susceptible and -resistant strains. RP 57669, RP 54479, and erythromycin were either inactive or bacteriostatic at 2 h. Of all drugs tested, RP 59500 yielded the most rapid killing.     

Glycopeptide susceptibility among Danish Enterococcus faecium and Enterococcus faecalis isolates of animal and human origin and PCR identification of genes within the VanA cluster

The MICs of vancomycin and avoparcin were determined for isolates of Enterococcus faecium and isolates of Enterococcus faecalis recovered from the feces of humans and animals in Denmark. Two hundred twenty-one of 376 (59%) isolates of E. faecium and 2 of 133 (1.5%) isolates of E. faecalis were resistant to vancomycin (MICs, 128 to > or = 256 micrograms/ml), and all vancomycin-resistant isolates were resistant to avoparcin (MICs, 64 to > or = 256 micrograms/ml). All vancomycin-resistant isolates examined carried the vanA, vanX, and vanR genes, suggesting that a gene cluster similar to that of the transposon Tn1546 was responsible for the resistance.     

MIC and time-kill study of antipneumococcal activities of RPR 106972 (a new oral streptogramin), RP 59500 (quinupristin-dalfopristin), pyostacine (RP 7293), penicillin G, cefotaxime, erythromycin, and clarithromycin against 10 penicillin-susceptible and -resistant pneumococci

Broth MICs and time-kill studies were used to test the activity of RP 59500 (quinupristin-dalfopristin), RPR 106972, pyostacine (RP 7293), erythromycin, clarithromycin, and cefotaxime for four penicillin-susceptible (MICs of 0.008 to 0.03 microgram/ml), two penicillin-intermediate (MIC of 0.25 microgram/ml), and four penicillin-resistant (MIC of 2.0 to 4.0 micrograms/ml) strains of pneumococci: 6 of 10 strains were resistant to macrolides (MICs of > or = 0.5 microgram/ml). MICs of RP 59500 (0.5 to 1.0 microgram/ml), RPR 106972 (0.125 to 0.25 microgram/ml), and pyostacine (0.125 to 0.25 microgram/ml) did not alter with the strain's penicillin or macrolide susceptibility status. Three penicillin-susceptible strains and one penicillin-intermediate strain were susceptible to macrolides (MICs of < or = 0.25 microgram/ml); the macrolide MICs for the remaining strains were > or = 4.0 micrograms/ml. Cefotaxime MICs rose with those of penicillin G, but all strains were inhibited at MICs of < or = 2.0 micrograms/ml. RP 59500 was bactericidal for all strains after 24 h at 2 x MIC and yielded 90% killing of all strains at 6 h at 2 x MIC; at 8 x MIC, RP 59500 showed 90% killing of six strains within 10 min (approximately 0.2 h). In comparison, RPR 106972 was bactericidal for 9 of 10 strains at 2 x MIC after 24 h and yielded 90% killing of all strains at 2 x MIC after 6 h; 90% killing of six strains was found at 8 x MIC at 0.2 h. Results for pyostacine were similar to those of RPR 106972. Erythromycin and clarithromycin were bactericidal for three of four macrolide-susceptible strains after 24 h at 4 x MIC. Clarithromycin yielded 90% killing of three strains at 8 x MIC after 12 h. Cefotaxime was bactericidal for all strains after 24 h at 4 x MIC, yielding 90% killing of all strains after 6 h at 4 x MIC. All three streptogramins yielded rapid killing of penicillin- and erythromycin-susceptible and -resistant pneumococci and were the only compounds which killed significant numbers of strains at 0.2 h.     

Antimicrobial activity of RU-66647, a new ketolide

A new macrolide subclass called ketolides, possess a mode of action similar to the macrolide-lincosamide-streptogramin (MLS) compounds. Utilizing reference in vitro tests, the in vitro activity of RU-66647 (a ketolide) was compared to other MLS compounds against 376 Gram-positive organisms and over 400 representative strains of Gram-negative bacilli. The ketolide's spectrum was most similar to clindamycin and an earlier drug in the series (RU-64004 or RU-004) against staphylococci and streptococci. However, RU-66647 was more active than erythromycin and azithromycin against oxacillin-resistant Staphylococcus spp. and vancomycin-resistant enterococci. Ketolide activity was more potent than other MLS drugs against vancomycin-susceptible enterococci (MIC90, 0.25-4 micrograms/ml) and all streptococci (MICs, < or = 0.25 microgram/ml). Erythromycin-resistant (constitutive) strains were generally inhibited by < or = 2 micrograms RU-66647/ml (staphylococci, 31 to 36%; streptococci, 100%; enterococci, 72%). RU-66647 was active against Haemophilus influenzae (MIC90, 2 micrograms/ml), Moraxella catarrhalis (MIC90, 0.12 microgram/ml), and pathogenic Neisseria spp. (MIC90 0.5 microgram/ml). The ketolide failed to inhibit Enterobacteriaceae, nonfermentative Gram-negative bacilli, and Bacteriodes fragilis group strains. RU-66647 was observed to be a promising new compound directed toward some organisms resistant to other MLS-class drugs.     

Antimicrobial characteristics of quinupristin/dalfopristin (Synercid at 30:70 ratio) compared to alternative ratios for in vitro testing

Quinupristin/dalfopristin is a new streptogramin combination that occurs at a natural ratio and formulation of 30:70. Rapid metabolism of the dalfopristin component to RP 12536 in vivo puts in question the validity of in vitro test of spectrum with the parent combination. In studies of quinupristin with both dalfopristin and RP 12536, a wide range of ratios (30:70, 50:50, 70:30) were tested by reference MIC and MBC tests. No significant potency differences were observed between combination ratios or metabolic components when testing 256 bacterial strains. Quinupristin/dalfopristin or quinupristin/RP 12536 remained active, by bactericidal action against many staphylococci and Streptococcus ssp. Enterococcus faecium strains were susceptible (MIC90, 2 micrograms/ml; static effect only) to the streptogramin, but E. faecalis, Pasteurella multocida, Pediococcus ssp., Haemophilus influenzae, and Bacteroides fragilis were generally less susceptible (MIC90, > or = 8 micrograms/ml). The log phase inoculum was preferred for MBC and kill-curve tests with this combination. The 30:70 ratio in vitro susceptibility test of quinupristin/dalfopristin as used to date, seems to predict the potency and spectrum of this streptogramin accurately and all clinically important in vivo ratios of the injectable form or its major metabolites. Quinupristin/dalfopristin should be further investigated for clinical use against emerging resistant Gram-positive infections, especially penicillin-resistant streptococci and glycopeptide-resistant E. faecium that exhibit susceptibility in this investigation.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1996). I. Susceptibility distribution

The frequencies of isolation and susceptibilities to antimicrobial agents were investigated on 680 bacterial strains isolated from patients with urinary tract infections (UTIs) in 10 hospitals during the period of June 1996 to May 1997. Of the above bacterial isolates, Gram-positive bacteria accounted for 30.4% and a majority of them were Enterococcus faecalis. Gram-negative bacteria accounted for 69.6% and most of them were Escherichia coli. Susceptabilities of several isolated bacteria to antimicrobial agents were as followed; 1. Enterococcus faecalis Ampicillin (ABPC) showed the highest activity against E. faecalis isolated from patients with UTIs. Its MIC90 was 1 microgram/ml. Imipenem (IPM) and vancomycin (VCM) were also active with the MIC90S of 2 micrograms/ml. The others had low activities with the MIC90S of 16 micrograms/ml or above. 2. Staphylococcus aureus including MRSA Arbekacin (ABK) and VCM showed the highest activities against both S. aureus and MRSA isolated from patients with UTIs. The MIC90S of them were 1 or 2 micrograms/ml. The others except minocycline (MINO) had low activities with the MIC90S of 32 micrograms/ml or above. 3. Staphylococcus epidermidis ABK and VCM showed the strongest activities against S. epidermis isolated from patients with UTIs. The MICs for all strains were equal to or lower than 2 micrograms/ml. Cefazolin (CEZ), cefotiam (CTM) and cefozopran (CZOP) were also active with the MIC90S of 4 micrograms/ml. Compared with antimicrobial activities of cephems is 1995, the MIC90S of them had changed into a better state. They ranged from 4 micrograms/ml 16 micrograms/ml in 1996. 4. Streptococcus agalactiae All drugs except MINO were active against S. agalactiae. ABPC, CZOP, IPM, and clarithromycin (CAM) showed the highest activities. The MICs for all strains were equal to or lower than 0.125 micromilligrams. Tosufloxacin (TFLX) and VCM were also active with the MIC90S of 0.5 micromilligrams. 5. Citrobacter freundii Gentamicin (GM) showed the highest activity against C. freundii isolated from patients with UTIs. Its MIC90 was 0.5 micrograms/ml. IPM and amikacin (AMK) were also active with the MIC90S of 1 microgram/ml and 2 micrograms/ml, respectively. Cefpirome (CPR) and CZOP were also active with the MIC90S of 8 micrograms/ml. The MIC90S of the others were 16 micrograms/ml or above. 6. Enterobacter cloacae IPM showed the highest activity against E. cloacae. The MICs for all strains were equal to or lower than 0.5 microgram/ml. The MIC90S of ciprofloxacin (CPFX) and TFLX were 1 microgram/ml, the MIC90 of AMK was 2 micrograms/ml, the MIC90S of CZOP, GM and ofloxacin (OFLX) were 4 micrograms/ml. The MIC50S of cephems except CEZ, cefmetazole (CMZ) and cefaclor (CCL) had changed into a better state in 1996, compared with those in 1995. 7. Escherichia coli All drugs except penicillins and MINO were active against E. coli. Particularly CPR, CZOP and IPM showed the highest activities against E. coli. The MIC90S of them were 0.125 microgram/ml or below. Among E. coli strains, those with low susceptibilities to cephems except CEZ, cefoperazone (CPZ), latamoxef (LMOX) and CCL have increased in 1996, compared with those in 1995. 8. Klebsiella pneumoniae K. pneumoniae was susceptible to all drugs except penicillins, with the MIC90S of 2 micrograms/ml or below. CPR had the strongest activity, the MICs for all strains were equal to or lower than 0.25 microgram/ml. Flomoxef (FMOX), cefixime (CFIX), CZOP and carumonam (CRMN) were also active with the MIC90S of 0.125 microgram/ml or below. 9. Pseudomonas aeruginosa All drugs except quinolones were not so active against P. aeruginosa with the MIC90S were 32 micrograms/ml or above. Quinolones were more active in 1996 than 1995. The MIC90S of them were between 4 micrograms/ml and 8 micrograms/ml, and the MIC50S of them were between 1 microgram/ml and 2 micrograms/ml. 10. Serratia marcescens GM showed the highest activity against S. marcescens. Its MIC90 was 1 micro     

Enterococcus faecium: in vitro activity of antimicrobial drugs, singly and combined, with and without defibrinated human blood, against multiple-antibiotic-resistant strains

The minimal inhibitory (MICs) and bactericidal concentrations of 14 antimicrobial drugs were determined against 17 clinical isolates of Enterococcus faecium, including 4 glycopeptide-resistant strains. Both teicoplanin and vancomycin lacked bactericidal activity against all 13 susceptible isolates. Time-kill experiments served to test various antibiotic combinations chiefly against glycopeptide-resistant strains in Mueller-Hinton broth (MHB) and in MHB supplemented with 65% (v/v) fresh defibrinated human blood. Co-trimoxazole, fusidic acid, and novobiocin yielded bacteriostatic effects. Rifampin was bactericidally active against rifampin-susceptible strains (MICs = 0.125 micrograms/ml), but less so against low-level-rifampin-resistant (MICs = 2-8 micrograms/ml) strains in MHB. However, in the presence of human blood, rifampin (2 micrograms/ml) combined with co-trimoxazole (0.25/4.75 micrograms/ml) killed rifampin-susceptible and low-level-rifampin-resistant, but not moderate-level-rifampin-resistant (MICs = 16-32 micrograms/ml) strains of E. faecium. Of two topical drugs examined, mupirocin merely inhibited strains of E. faecium; conversely, taurolidine at 2,000 micrograms/ml was efficacious against all strains examined, although the kinetics of bactericidal activity were retarded somewhat in the presence of 65 vol% human blood.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1995). I. Susceptibility distribution]

The frequencies of isolation and susceptibilities to antimicrobial agents were investigated on 704 bacterial strains isolated from patients with urinary tract infections (UTIs) in 11 hospitals during the period of June 1995 to May 1996. Of the above bacterial isolates, Gram-positive bacteria accounted for 29.8% and a majority of them were Enterococcus faecalis. Gram-negative bacteria accounted for 70.2% and most of them were Escherichia coli. Susceptibilities of several isolated bacteria to antimicrobial agents were as followed; 1. Enterococcus faecalis Ampicillin (ABPC) and imipenem (IPM) showed the highest activities against E. faecalis isolated from patients with UTIs. The MIC90S of them were 1 microgram/ml. Vancomycin (VCM) and piperacillin (PIPC) were also active with the MIC90S of 2 micrograms/ml and 4 micrograms/ml, respectively. The others had low activities with the MIC90S of 16 micrograms/ml or above. 2. Staphylococcus aureus including MRSA VCM showed the highest activities against S. aureus isolated from patients with UTIs. Its MIC90 was 1 microgram/ml against both S. aureus and MRSA. Arbekacin (ABK) was also active with the MIC90 of 2 micrograms/ml. The other except minocycline (MINO) had very low activities with the MIC90S of 64 micrograms/ml or above. 3. Staphylococcus epidermidis ABK and MINO showed the strongest activities against S. epidermidis isolated from patients with UTIs. The MIC90S of them were 0.25 microgram/ml. VCM was also active with the MIC90 of 1 microgram/ml. The MIC90S of cephems ranged from 2 micrograms/ml to 16 micrograms/ml in 1994, but they ranged from 8 micrograms/ml to 128 micrograms/ml in 1995. These results indicated that some resistances existed among S. epidermidis to cephems. 4. Streptococcus agalactiae All drugs except gentamicin (GM) were active against S. agalactiae. ABPC, cefmenoxime (CMX), IPM, erythromycin (EM), clindamycin (CLDM) and clarithromycin (CAM) showed the highest activities. The MICs for all strains were lower than 0.125 microgram/ml. The MIC90S of the others were 2 micrograms/ml or below. 5. Citrobacter freundii IPM showed the highest activity against C. freundii isolated from patients UTIs. Its MIC90 was 1 microgram/ml. GM was also active with the MIC90 of 2 micrograms/ml. Cefpirome (CPR), cefozopran (CZOP) and amikacin (AMK) were also active with the MIC90S of 4 micrograms/ml. Penicillins and cephems except CMX, CPR and CZOP showed low activities with MIC90S of 256 micrograms/ml or above. 6. Enterobacter cloacae IPM showed the highest activity against E. cloacae. The MICs for all strains were equal to or lower than 1 microgram/ml. MINO and tosufloxacin (TFLX) were also active with the MIC90S of 8 micrograms/ml. Penicillins and cephems except CPR and CZOP showed lower activities with the MIC90S of 256 micrograms/ml or above. 7. Escherichia coli. Most of the antimicrobial agents were active against E. coli. Particularly CPR, CZOP and IPM showed the highest activities against E. coli. The MICs for all strains were equal to or lower than 0.5 microgram/ml. CMX and TFLX were also active with the MIC90S of 0.125 microgram/ml or below. Penicillins were slightly active with MIC90S of 128 micrograms/ml or above. 8. Klebsiella pneumoniae K. pneumoniae was susceptible to all drugs except penicillins, with MIC90S of 2 micrograms/ml or below. Carumonam (CRMN) had the strongest activity against K. pneumoniae, the MICs for all strains were equal to or lower than 0.125 microgram/ml. Comparing with the result of 1994, the sensitivities of K. pneumoniae against all drugs had obviously changed into a better state. For example, the MIC90S of cephems ranged from 0.25 microgram/ml to 16 micrograms/ml in 1994, but they were all lower than 2 micrograms/ml in 1995. 9. Proteus mirabilis P. mirabilis was susceptible to a majority of drugs. CMX, ceftazidime (CAZ), cefixime (CFIX), and CRMN showed the highest activities against P. mirabilis isolated from patients with UTIs. MICs of CRMN for all     

Successful treatment of persistent bacteremia due to vancomycin-resistant, ampicillin-resistant Enterococcus faecium

Emergence of vancomycin-resistant enterococci has become an increasing problem in many medical centers. We report a liver transplant recipient with vancomycin-resistant Enterococcus faecium bacteremia who was successfully treated using very high dose continuous infusion ampicillin/sulbactam, plus gentamicin after he remained bacteremic on high dose ampicillin and gentamicin. At our institution, 83% of E. faecium isolates from 1994 were inhibited by ampicillin/sulbactam compared to 66% for ampicillin at an MIC < or = 64 micrograms/ml. None of these strains produced beta-lactamase, suggesting sulbactam may have an unexplained beneficial effect against some enterococci. Although an MIC of < or = 8 micrograms/ml is required for ampicillin to be considered active against enterococci, much higher levels of ampicillin or ampicillin/sulbactam are safely achievable. The response of our patient and the reported in vivo data have implications for future treatment of this pathogen, and may necessitate a reevaluation of susceptibility interpretation guidelines by clinical laboratories, and therapeutic drug dosing by clinicians.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from urinary tract infections (1993). I. Susceptibility distribution

The frequencies of isolation and susceptibilities to antimicrobial agents were investigated on 657 bacterial strains isolated from patients with urinary tract infections in 10 hospitals during the period of June 1993 to May 1994. Of the above total bacterial isolates, Gram-positive bacteria accounted for 28.3% and a majority of them were Enterococcus faecalis. Gram-negative bacteria accounted for 71.7% and most of them were Escherichia coli. 1. Enterococcus faecalis Ampicillin (ABPC), imipenem (IPM) and vancomycin (VCM) showed the highest activities against E. faecalis isolated from patients with urinary tract infections. The MIC90s of them were 2 micrograms/ml. Piperacillin (PIPC) was also active with the MIC90 of 8 micrograms/ml. The others were not so active with the MIC90s of 32 micrograms/ml or above. 2. Staphylococcus aureus including MRSA VCM showed the highest activities against S. aureus isolated from patients with urinary tract infections. Its MIC90 was 1 microgram/ml. Arbekacin (ABK) was also active with the MIC90 of 2 micrograms/ml. The others were not so active with the MIC90s of 32 micrograms/ml or above. 3. Staphylococcus epidermidis VCM showed the strongest activity against S. epidermidis isolated from patients with urinary tract infections. Its MIC90 was 1 microgram/ml. ABK was also active with the MIC90 of 4 micrograms/ml. The others except ABPC were not so active with the MIC90s of 32 micrograms/ml or above. 4. Streptococcus agalactiae Most of the agents were active against S. agalactiae isolated from patients with urinary tract infections. Penicillins, cephems, erythromycin (EM), and clindamycin (CLDM) showed the highest activities. The MIC90s of them were 0.25 microgram/ml or below. Amikacin (AMK) and minocycline (MINO) showed somewhat low activities with the MIC90s of 16 micrograms/ml. 5. Citrobacter freundii IPM showed the highest activities against C. freundii isolated from patients with urinary tract infections. Its MIC90 was 2 micrograms/ml. Cefozopran (CZOP) and gentamicin (GM) were also active with the MIC90s of 8 micrograms/ml. Penicillins and cephems generally were not so active. 6. Enterobacter cloacae IPM and GM showed the highest activities against E. cloacae. The MIC90s of them were 1 microgram/ml. CZOP and tosufloxacin (TFLX) were also active with the MIC90s of 8 micrograms/ml. Penicillins and cephems except CZOP showed lower activities with the MIC90s of 64 micrograms/ml or above. 7. Escherichia coli Most of antimicrobial agents were active against E. coli. Flomoxef (FMOX), CZOP, IPM, CPFX and TFLX showed the highest activities against E. coli. The MIC90s of them were 0.125 microgram/ml or below. Cefmenoxime (CMX), ceftazidime (CAZ), cefuzonam (CZON), latamoxef (LMOX), carumonam (CRMN), norfloxacin (NFLX) and ofloxacin (OFLX) were also active with the MIC90s of 0.25 microgram/ml. Penicillins and MINO were not so active with the MIC90s of 32 micrograms/ml or above. 8. Klebsiella pneumoniae CZOP, IPM and CRMN showed the highest activities against K. pneumoniae. The MIC90s of them were 0.125 microgram/ml or below. CAZ, CZON, CFIX, CPFX and TFLX were also active the MIC90s of 0.25 microgram/ml. Penicillins were not so active with the MIC90s of 128 micrograms/ml or above. 9. Proteus mirabilis P. mirabilis was susceptible to a majority of drugs. CMX, CAZ, CZON, LMOX, CFIX, CRMN and CPFX showed the highest activities against P. mirabilis isolated from patients with urinary tract infections. The MIC90s of them were 0.125 microgram/ml or below. MINO was not so active with the MIC90 of 256 micrograms/ml or above. 10. Pseudomonas aeruginosa Most of the agents were not so active against P. aeruginosa. IPM showed MIC90 of 8 micrograms/ml.     

Activity of HMR 3647 compared to those of six compounds against 235 strains of Enterococcus faecalis

Agar dilution was used to test the activities of HMR 3647, erythromycin A, azithromycin, clarithromycin, roxithromycin, clindamycin, and quinupristin-dalfopristin against 235 strains of Enterococcus faecalis. HMR 3647 was the most active compound (MICs at which 50 and 90% of the isolates are inhibited [MIC50 and MIC90, respectively] of 0.06 and 4.0 microg/ml, respectively). The MIC50 and MIC90 (with the MIC50 given first and the MIC90 given second; both in micrograms per milliliter) for other compounds were as follows: 4.0 and >32.0 for erythromycin A, 16.0 and >32.0 for azithromycin, 2.0 and >32 for clarithromycin, 32.0 and >32.0 for roxithromycin, 32.0 and >32.0 for clindamycin, and 8.0 and 16.0 for quinupristin-dalfopristin. All compounds were only bacteriostatic.     

Survival of vancomycin-resistant and vancomycin-susceptible enterococci on dry surfaces

We compared the abilities of Enterococcus faecium strains (three vancomycin-resistant enterococci [VRE] and five vancomycin-susceptible enterococci [VSE]) and Enterococcus faecalis strains (one VRE and 10 VSE) to survive under dry conditions. Bacterial suspensions of the strains were inoculated onto polyvinyl chloride and stored under defined conditions for up to 16 weeks. All strains survived for at least 1 week, and two strains survived for 4 months. A statistical model was used to distribute the 19 resulting survival curves between two types of survival curves. The type of survival curve was not associated with the species (E. faecalis versus E. faecium), the source of isolation (patient versus environment), or the susceptibility to vancomycin (VRE versus VSE). Resistance to dry conditions may promote the transmissibility of a strain, but VRE have no advantages over VSE with respect to their ability to survive under dry conditions.     

Selective isolation of vancomycin-resistant enterococci

Broth formulations of two media selective for enterococci, Enterococcel, M-Enterococcosel broths were supplemented with 6 micrograms of vancomycin per ml and evaluated for isolation of vancomycin-resistant enterococci (VRE). Each broth was challenged with various concentrations of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and vancomycin-susceptible and vancomycin-resistant enterococci and with 193 perianal specimens obtained from patients at risk in our institution for VRE colonization. Both the Enterococcosel and M-Enterococcus broths with vancomycin detected as few as 1 to 9 CFU of VRE while inhibiting growth of the other organisms tested. Enterococcus faecium organisms (MIC, > 256 micrograms/ml) were recovered from 66 perianal swab cultures in the enterococcosel-vancomycin broth, and VRE were recovered from 62 perianal swab cultures in the M-Enterococcus-vancomycin broth. Enterococcosel-vancomycin broth detected VRE in perianal specimens 48 h earlier than did M-Enterococcus-vancomycin broth. Enterococcosel broth with 6 micrograms of vancomycin per ml can be used for the rapid and selective isolation of VRE from surveillance specimens.     

Vancomycin-resistant Enterococcus faecium infections in the ICU and quinupristin/dalfopristin

The incidence of vancomycin resistance among enterococci, and Enterococcus faecium in particular, has increased sharply in the last few years. This shift toward infection with resistant Gram-positive organisms is thought to be the consequence of certain features specific to the intensive care setting: a high concentration of severely compromised patients; continued use of indwelling devices and invasive procedures; and widespread, empiric use of antimicrobial agents directed against Gram-negative bacilli. Measures that can be taken to prevent the development of bacterial resistance in the ICU include strict adherence to infection control policies and asepsis, and rational use of antibiotics. Current antimicrobial regimens for serious enterococcal infections consist of a combination of ampicillin, penicillin G, or vancomycin plus streptomycin or gentamicin. High levels of resistances among some enterococcal isolates, however, may render these strategies ineffective. A new agent, quinupristin/dalfopristin (RP 59500), has demonstrated encouraging in vitro activity against vancomycin-resistant E. faecium. Initial clinical reports, though limited, are similarly promising. Although phase III clinical trials with RP 59500 are not completed, the agent is available through an emergency-use program for patients with severe Gram-positive infections who cannot tolerate or do not respond to all other clinically appropriate antibiotics.     

Preferential hydrolysis of oxidized phosphatidylcholine in cholesterol-containing phosphatidylcholine liposome by phospholipase A2

From 125 separate cloacal cultures from three turkey flocks fed virginiamycin, 104 Enterococcus faecium and 186 Enterococcus faecalis isolates were obtained. As the turkeys aged, there was a higher percentage of quinupristin-dalfopristin-resistant E. faecium isolates, with isolates from the oldest flock being 100% resistant. There were no vancomycin-resistant enterococci. Results of pulsed-field gel electrophoresis (PFGE) indicated there were 11 PFGE types of E. faecalis and 7 PFGE types of E. faecium that were in more than one group of flock cultures.     

Cytokine autoantibodies in multiple sclerosis, aseptic meningitis and stroke

BACKGROUND AND OBJECTIVE: To determine and then compare the time-kill profiles of Enterococcus to antibiotics used for intravitreal therapy. PATIENTS AND METHODS: The time-kill profiles of four endophthalmitis isolates of Enterococcus faecalis, one vancomycin-resistant E. faecalis isolate, and three vancomycin-resistant isolates of E. faecium were determined against vancomycin, amikacin, cefazolin, gentamicin, ampicillin, ciprofloxacin, ceftazidime, clindamycin, and the combinations of vancomycin and amikacin, vancomycin and ceftazidime, vancomycin and gentamicin, vancomycin and ampicillin, cefazolin and gentamicin, and ampicillin and gentamicin. RESULTS: No single antibiotic or combination was bactericidal (defined as 99.9% kill) to all isolates of Enterococcus. Gentamicin was bactericidal to all E. faecalis isolates. None of the tested antibiotics were bactericidal to vancomycin-resistant E. faecium. CONCLUSIONS: The time-kill profiles demonstrated that vancomycin and ceftazidime did not produce a 99.9% kill for E. faecalis in this small study. Gentamicin combined with either cefazolin or ampicillin had somewhat better bactericidal activity and should be considered as an alternative therapy. Novel therapy may be necessary to treat endophthalmitis because of vancomycin-resistant Enterococcus, depending on the susceptibility patterns of the individual isolate and the response to initial therapy.