Routine use of the Gen-Probe MTD2 amplification test for detection of Mycobacterium tuberculosis in clinical specimens in a large public health mycobacteriology laboratory

The antimicrobial susceptibility of 239 coagulase-negative staphylococci (CNS) isolates consecutively collected from blood culture in patients admitted in a 600-bed teaching hospital was evaluated. The isolates were identified to the species level by conventional methods and the MicroScan Positive Combo Panel type 6 system, and their susceptibility to vancomycin, teicoplanin, and oxacillin were tested by agar dilution, disk diffusion, and MicroScan-WalkAway system. The species distribution was as follows: Staphylococcus epidermidis 120 (50.2%), S. hominis 29 (12.1%), S. haemolyticus 24 (10.0%), S. cohnii 14 (5.9%), and isolates from other CNS species 52 (21.8%). The percentage of resistance to oxacillin was 74.5% by agar dilution. The highest percentages of oxacillin resistance were found among S. haemolyticus (95.8%) and S. epidermidis (80.8%). Teicoplanin resistance (MIC > or = 32 micrograms/mL) was detected in five S. haemolyticus isolates, whereas intermediate resistance (MIC = 16 micrograms/mL) was detected in nine strains. These isolates with reduced susceptibility to teicoplanin were resistant to oxacillin, but remained susceptible to vancomycin (MIC < or = 4 micrograms/mL). Two isolates, one S. haemolyticus and one S. epidermidis, showed a vancomycin MIC of 8 micrograms/mL, and both MicroScan and disk diffusion methods classified these isolates as susceptible. Our results showed that glycopeptide resistance is emerging among CNS isolates in our institution and the disk diffusion method may not detect isolates with decreased susceptibility to these antimicrobial agents.     

Activities of daptomycin and teicoplanin against Staphylococcus haemolyticus and Staphylococcus epidermidis, including evaluation of susceptibility testing recommendations.

The in vitro activities of daptomycin, teicoplanin, and three other antimicrobial agents were determined against 105 strains of Staphylococcus haemolyticus and 92 strains of Staphylococcus epidermidis. The MICs for 90% of strains tested (MIC90s) of fusidic acid and rifampin were less than or equal to 0.25 microgram/ml. The MIC90s of daptomycin and vancomycin were less than or equal to 4 micrograms/ml. Teicoplanin had a comparable MIC90 of less than or equal to 4 micrograms/ml for isolates of S. epidermidis. However, MIC90s were 8 and 16 micrograms/ml for oxacillin-susceptible and oxacillin-resistant S. haemolyticus, respectively. Disk diffusion tests were evaluated for daptomycin and teicoplanin. Disks with 30 micrograms of teicoplanin performed satisfactorily when S. epidermidis was tested, but when S. haemolyticus was tested, there was a very major error rate of 10% and a minor error rate of 38%.     

Susceptibility of Staphylococcus species and subspecies to fleroxacin.

Twenty-four Staphylococcus species or subspecies were examined for their susceptibilities to the fluoroquinolone fleroxacin (Ro 23-6240) by disk diffusion (5-micrograms disk) and by agar dilution for the determination of MICs. Resistant strains were further tested for their susceptibilities to oxacillin and the fluoroquinolone ciprofloxacin. Reference strains of the novobiocin-resistant species (Staphylococcus saprophyticus, Staphylococcus cohnii, Staphylococcus xylosus, Staphylococcus arlettae, and Staphylococcus gallinarum) had an intrinsic intermediate susceptibility (MIC, 4 micrograms/ml) to fleroxacin. Fleroxacin resistance was not observed in the reference strains of the novobiocin-susceptible species (MIC, 0.5 to 2.0 micrograms/ml). Clinical isolates of coagulase-negative species were generally less susceptible to fleroxacin than were reference strains. Seven percent of the Staphylococcus epidermidis clinical strains were resistant (MIC, greater than or equal to 8 micrograms/ml) to fleroxacin. Of these strains, 77% were resistant to oxacillin and 50% were resistant to ciprofloxacin. Thirty-four percent of the Staphylococcus haemolyticus clinical strains were resistant to fleroxacin, and 9% had intermediate susceptibility. Of the resistant strains, 95% were resistant to oxacillin and 77% were resistant to ciprofloxacin, while 23% had intermediate susceptibility to ciprofloxacin. Fleroxacin is an effective antimicrobial agent against most staphylococci.     

The prevalence of staphylococcal resistance to penicillinase-resistant penicillins. A retrospective and prospective national surveillance trial of isolates from 40 medical centers

In a retrospective survey of resistance to penicillinase-resistant penicillins (PRPs) in 152,076 clinical staphylococcal strains isolated in 40 United States Hospitals in 1985 and 1986, rates of resistance to oxacillin were found to be 11 and 13%, respectively, among Staphylococcus aureus isolates. The rates were approximately four times higher among coagulase-negative staphylococcal strains. In a prospective study of 1,408 wound or bacteremia isolates from the participant hospitals, oxacillin and methicillin agar screening, disk diffusion, and broth microdilution testing were conducted at a single reference laboratory. These tests yielded PRP resistance rates of 15% among S. aureus, 75% among S. epidermidis, and 48% among other coagulase-negative strains. No major changes in the distribution of resistance rates among hospitals or by hospital type were observed. Dilution susceptibility testing of several antimicrobial agents against PRP-resistant isolates and species-matched susceptible isolates from the same hospital showed that teicoplanin and vancomycin were the most active drugs (100% of S. aureus isolates were susceptible). Teicoplanin and vancomycin disk diffusion testing of all PRP-resistant staphylococcal strains also showed that these isolates were susceptible to the glycopeptides. However, agar dilution screening and broth microdilution tests revealed that several coagulase-negative strains, predominantly S. haemolyticus, had teicoplanin MICs greater than or equal to 8 micrograms/ml. S. haemolyticus isolates represented a very small number of the total stains tested. Teicoplanin and vancomycin were also the most active drugs when tested against older (1962-82) clinical PRP-resistant S. aureus strains from the reference laboratory collection. The methods found to be superior in detecting PRP-resistant strains were the oxacillin 6 micrograms/ml agar screening test in 4% NaCl-supplemented Mueller-Hinton agar and the 1 microgram oxacillin disk test. By reference laboratory standards, participant laboratories were incorrect in only 2.3% of species identifications and 4.5% of oxacillin-susceptibility determinations, indicating acceptable contemporary agreement and accuracy.     

In vitro antistaphylococcal activities of two investigative fluoroquinolones, CI-960 and WIN 57273, compared with those of ciprofloxacin, mupirocin (pseudomonic acid), and peptide-class antimicrobial agents.

By using broth microdilution, 373 clinical isolates of staphylococci were studied to determine their susceptibilities to CI-960, WIN 57273, ciprofloxacin, mupirocin, vancomycin, teicoplanin, and ramoplanin. Test strains comprised 179 strains of Staphylococcus aureus and 194 strains of coagulase-negative species. Strains of S. aureus were susceptible to CI-960, which had a mode MIC of 0.032 micrograms/ml and an MIC for 90% of the strains of 2 micrograms/ml. CI-960 was equally active against methicillin-susceptible and -resistant S. aureus strains as well as ciprofloxacin-resistant strains. Similarly, WIN 57273 was highly active, with a mode MIC of 0.008 micrograms/ml and an MIC for 90% of the strains of 1 micrograms/ml. No cross-resistance to CI-960 and WIN 57273 among ciprofloxacin-resistant strains was detected. Mupirocin was four- to eightfold more active than ramoplanin, vancomycin, and teicoplanin. With regard to coagulase-negative staphylococci, CI-960 and WIN 57273 were the most active of the test compounds, inhibiting all strains at 0.5 and 1 micrograms/ml, respectively. Against the same strains, mupirocin was fourfold more active than ramoplanin and eightfold more active than vancomycin. Five strains of S. haemolyticus were found to be resistant to ciprofloxacin, while resistance to teicoplanin was found among strains of S. epidermidis, S. haemolyticus, S. hominis, S. saprophyticus, S. simulans, S. warneri, and S. xylosus.     

Comparative in vitro activity of teicoplanin and vancomycin against United States teicoplanin clinical trial isolates of gram-positive cocci.

In this study, the in vitro activity of teicoplanin and vancomycin was directly compared against 503 Gram-positive cocci isolated during the U.S. teicoplanin clinical trials. Both antibiotics were equally active against oxacillin-sensitive Staphylococcus aureus, oxacillin-sensitive and oxacillin-resistant Staphylococcus epidermidis, and other coagulase-negative staphylococci, except Staphylococcus haemolyticus. Teicoplanin was fourfold more active than vancomycin against oxacillin-resistant S. aureus (MIC90, 0.5 vs. 2.0 micrograms/ml), whereas vancomycin was more active than teicoplanin (MIC90, 2.0 vs. 8.0 micrograms/ml) against oxacillin-resistant S. haemolyticus. Teicoplanin was two- to eightfold more active than vancomycin against the streptococci and enterococci tested.     

Activities of two new teicoplanin amide derivatives (MDL 62211 and MDL 62873) compared with activities of teicoplanin and vancomycin against 800 recent staphylococcal isolates from France and the United States.

MDL 62211 is the amide derivative of the teicoplanin complex and MDL 62873 is a more focused amide derivative of the teicoplanin A2-2 peak. Each investigational compound had nearly identical activity and was 2- to 16-fold more active than teicoplanin or vancomycin. The MDL 62873 MICs for 90% of the strains tested were as follows: Staphylococcus aureus, oxacillin susceptible, 0.12 micrograms/ml; S. aureus, oxacillin resistant, 0.25 micrograms/ml; coagulase-negative staphylococci (CNS), oxacillin susceptible, 0.25 micrograms/ml; and CNS, oxacillin resistant, 2 micrograms/ml. CNS isolates from France were generally more susceptible than those tested in the United States. Teicoplanin-resistant U.S. isolates were usually Staphylococcus haemolyticus (1.8% of all tested strains), for which MICs ranged from 32 to greater than 128 micrograms/ml. MDL 62873 was not active against the Bacteroides fragilis group but was generally effective against gram-positive anaerobic strains.     

In vitro activity of LY264826, a new glycopeptide antibiotic, against gram-positive bacteria isolated from patients with cancer.

The in vitro activity of LY264826, a novel glycopeptide antibiotic produced by Amycolatopsis orientalis, was compared with those of vancomycin, teicoplanin, and oxacillin against 311 gram-positive clinical isolates from patients with cancer, LY264826 had lower MICs for 90% of isolates (MIC90) than vancomycin for all species tested. It was active against oxacillin-resistant isolates including Staphylococcus aureus (MIC90, 0.5 micrograms/ml), Staphylococcus haemolyticus (MIC90, 2.0 micrograms/ml), Enterococcus spp. (MIC90, 0.5 micrograms/ml), Bacillus cereus (MIC90, 0.25 micrograms/ml), and Corynebacterium jeikeium (MIC90, 0.12 micrograms/ml). For S. aureus, including oxacillin-resistant isolates, the MICs of LY264826 were similar to those of teicoplanin. For coagulase-negative staphylococci, however, LY264826 had MICs that were 4- to 32-fold lower than those of teicoplanin. Against most streptococcal species the activities of LY264826 and teicoplanin were similar. Bactericidal activity against Staphylococcus spp. and most Streptococcus pyogenes isolates was less than or equal to 1 dilution of the MIC. One isolate of S. pyogenes and all Enterococcus faecalis strains tested were tolerant of LY264826, with MBCs greater than or equal to 32-fold greater than the MICs. The addition of 50% human serum resulted in a significant increase in activity only against Staphylococcus epidermidis. Variations in pH from 6.4 to 8.4 and in inoculum from 10(3) to 10(7) CFU/ml did not significantly affect the activity of LY264826.     

In vitro susceptibilities of four species of coagulase-negative staphylococci.

The in vitro susceptibilities of 260 strains of coagulase-negative staphylococci to penicillin G, oxacillin, nafcillin, methicillin, cephalothin, and seven non-beta-lactam antimicrobial agents were determined and compared with the susceptibilities of 54 strains of Staphylococcus aureus with known patterns of susceptibility. Penicillin G susceptibility for S. aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis was readily determined by using beta-lactamase tests with induced cells and with a standardized microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to the coagulase-negative species. Percentages of organisms susceptible were as follows: S. epidermidis, 7%; S. haemolyticus, 5%; and S. hominis, 47%. Oxacillin susceptibility for these four species was readily determined by using a modification of the microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to S. haemolyticus and S. hominis, but alternate criteria were necessary for S. epidermidis. Percentages of organisms susceptible were as follows: S. epidermidis, 29%; S. haemolyticus, 36%; and S. hominis, 97%. Staphylococcus saprophyticus differed from the other staphylococcal species; all strains were beta-lactamase negative and were penicillin susceptible but had higher penicillin G MICs than did susceptible strains of the other species. There was total cross resistance among the penicillinase-resistant penicillins and cephalothin for the coagulase-negative staphylococci as well as for S. aureus; oxacillin MICs were more reliable than MICs of the other drugs or a standardized disk diffusion test for distinguishing resistant from susceptible strains. Vancomycin, rifampin, and ciprofloxacin were consistently active against all staphylococci. Erythromycin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole were more active against oxacillin-susceptible staphylococci than against oxacillin-resistant staphylococci.     

Bactericidal activity and killing rate of serum in volunteers receiving vancomycin or teicoplanin with and without amikacin given intravenously

We have studied the interaction between vancomycin or teicoplanin and amikacin in two groups of five volunteers randomized to receive either (a) vacomycin, amikacin, vancomycin+amikacin, or (b) teicoplanin, amikacin, teicoplanin+amikacin. Each administration was given on separate days, in random order with a 48 hours washout period between each infusion. The serum concentrations measured microbiologically at time 0, 1 and 6 h were: 42.6, 11.4 and 4.1 mg/l respectively for teicoplanin; 27.6, 13.9, and 4.2 mg/l for vancomycin, and 44.9, 17.8, and 1.9 mg/l for amikacin. Teicoplanin was also measured using a solid-phase enzyme-receptor assay (SPERA). The serum bactericidal titres and the rate of killing in serum were measured 1 and 6 h after infusion against Staphylococcus aureus susceptible or resistant to oxacillin (5 strains each), S. epidermidis susceptible and resistant to oxacillin (5 strains each), Corynebacterium JK (5 strains), Listeria monocytogenes (5 strains), and Mycobacterium fortuitum (3 strains). The addition of amikacin to either teicoplanin or vancomycin increased the serum bactericidal titres against staphylococci with the exception of oxacillin-resistant S. epidermidis. Teicoplanin+amikacin was the most active regimen against L. monocytogenes and was equivalent to vancomycin+amikacin against M. fortuitum. Teicoplanin alone and teicoplanin+amikacin had a significantly lower killing rate against staphylococci than amikacin alone.     

Glycopeptide susceptibility profiles of Staphylococcus haemolyticus bloodstream isolates

Twelve clinical strains of Staphylococcus haemolyticus (eight methicillin resistant and three methicillin susceptible), isolated from blood cultures between 1982 and 1997, were investigated for teicoplanin and vancomycin susceptibility profiles. On the basis of conventional MIC tests and breakpoints, four isolates were susceptible (MICs, 1 to 8 microgram/ml) and eight were resistant (MICs, 32 to 64 microgram/ml) to teicoplanin while all were susceptible to vancomycin (MICs, 1 to 2 microgram/ml). All four strains for which the conventional teicoplanin MICs were within the range of susceptibility expressed heterogeneous resistance to teicoplanin and homogeneous vancomycin susceptibility. Of the eight strains for which the conventional teicoplanin MICs were within the range of resistance, six expressed heterogeneous and two expressed homogeneous teicoplanin resistance while seven showed heterogeneous vancomycin resistance profiles (with subpopulations growing on 8 microgram of the drug per ml at frequencies of >/=10(-6) for six strains and 10(-7) for one) and one demonstrated homogeneous vancomycin susceptibility. Of six bloodstream isolates of other staphylococcal species (S. aureus, S. epidermidis, and S. simulans), for all of which the conventional teicoplanin MICs were >/=4 microgram/ml and the vancomycin MICs were 相似文献   

Revised interpretation of oxacillin MICs for Staphylococcus epidermidis based on mecA detection.

In 1992 and 1993, at The Ohio State University Medical Center, a larger proportion of Staphylococcus epidermidis strains required oxacillin MICs of 1 to 2 micrograms/ml than did Staphylococcus aureus strains. mecA genotype was correlated with antimicrobial susceptibility for selected clinical S. epidermidis strains. All 14 strains that required oxacillin MICs of < or = 0.25 microgram/ml and 2 of 5 strains that required oxacillin MICs of 0.5 microgram/ml were susceptible by 1-microgram oxacillin disk test and were mecA negative. Three of 5 strains that required oxacillin MICs of 0.5 microgram/ml and all 18 strains that required oxacillin MICs of > or = 1.0 microgram/ml were resistant by oxacillin disk test and were mecA positive. Current National Committee for Clinical Laboratory Standards MIC interpretive criteria may underestimate methicillin resistance among S. epidermidis strains.     

Percentages and distributions of teicoplanin- and vancomycin-resistant strains among coagulase-negative staphylococci.

The activities of teicoplanin and vancomycin against 362 coagulase-negative staphylococci were determined by an agar dilution method. At the 4- and 32-micrograms/ml breakpoint levels of the National Committee for Clinical Laboratory Standards, 23.2% of the strains were intermediate and 1.7% were resistant to teicoplanin, in contrast to less than 0.3% intermediate to vancomycin. Resistant strains belonged to the species Staphylococcus epidermidis (74%) and S. haemolyticus (19%).     

In vitro antistaphylococcal activity of pefloxacin alone and in combination with other antistaphylococcal drugs.

MICs of pefloxacin and nine antistaphylococcal drugs were determined for 200 isolates of Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, and Staphylococcus saprophyticus. All the strains were susceptible to pefloxacin, vancomycin, and rifampin. Oxacillin-resistant strains were uniformly resistant to cephalothin and were more likely to be resistant to gentamicin, erythromycin, clindamycin, doxycycline, and trimethoprim-sulfamethoxazole than were oxacillin-susceptible strains. Time-kill studies with 23 strains of S. aureus, S. epidermidis, and S. haemolyticus indicated that the relative order of bactericidal activities was gentamicin greater than or equal to pefloxacin greater than oxacillin greater than vancomycin greater than rifampin. Pefloxacin combined with oxacillin or vancomycin killed staphylococci more rapidly than oxacillin or vancomycin alone but less rapidly than pefloxacin alone. Gentamicin combined with oxacillin, vancomycin, or pefloxacin resulted in the most rapid killing of gentamicin-susceptible strains. Rifampin combined with oxacillin, vancomycin, or pefloxacin reduced the bactericidal activities of those drugs, but rifampin resistance was not observed as it was with rifampin alone. Pefloxacin is a potentially useful antistaphylococcal agent.     

Development of in-vitro resistance to glycopeptide antibiotics: assessment in staphylococci of different species.

Forty-two clinical isolates belonging to ten species of staphylococci were studied for their ability to develop single-step resistance, in vitro, to glycopeptide antibiotics. Selection was attempted through separate exposure to four glycopeptides (vancomycin, teicoplanin, and two investigational semisynthetic derivatives of the latter, TD-A3 and CTA-A1) on agar containing 10 mg/l of the test drug. No survivors from any test strain were recovered after exposure to TD-A3 or CTA-A1. After exposure to vancomycin or teicoplanin, surviving clones were only recovered from strains of three species, Staphylococcus aureus, S. epidermidis, and S. haemolyticus. Emergence of resistant clones was easier to observe from strains of S. haemolyticus exposed to teicoplanin. When tested for susceptibility, many survivors exhibited vancomycin and teicoplanin MICs below the drug concentration used for in-vitro selection, probably due to an inoculum effect in the plating procedure. In particular, the vancomycin MICs did not exceed 8 mg/l for S. aureus and S. epidermidis clones, and reached 16 mg/l for some clones from a S. haemolyticus strain. Teicoplanin MICs did not exceed 8 mg/l for S. aureus clones, but reached 64 mg/l for some clones of S. epidermidis, and were particularly high (64 to greater than or equal to 128 mg/l) for most clones of S. haemolyticus. In contrast, against all clones selected from all three species, the MICs of TD-A3 and CTA-A1 did not exceed 2 and 4 mg/l, respectively. Morphological investigations indicated that the colonies of a highly resistant S. haemolyticus clone were smaller and more butyraceous in consistency than those of the parent strain. In transmission and scanning electron microscopy studies, this same S. haemolyticus clone showed a more irregular cell wall than the parent strain.     

European glycopeptide susceptibility survey of Gram-positive bacteria for 1995

In the European Glycopeptide Susceptibility Survey 7078 Gram-positive isolates collected in 1995 from 70 centers in 9 countries of Western Europe were examined, using a standardized, quantitative susceptibility testing method. Of the 7078 isolates, 6824 (96.4%) were tested by the national coordinating centers. Teicoplanin (mode MIC 0.5 μg/mL) was generally twice as active as vancomycin (mode MIC 1 μg/mL) against Staphylococcus aureus (n = 2852). All isolates were susceptible to vancomycin (MIC ≤4 μg/mL) and all but four to teicoplanin (MIC ≤8 μg/mL); these four isolates were of intermediate susceptibility (MIC 16 μg/mL). With coagulase-negative staphylococci (n = 1444), the distribution of MIC of teicoplanin was wider than for vancomycin. Two and two-tenths percent of coagulase-negative staphylococci excluding Staphylococcus haemolyticus required 16 μg/mL teicoplanin for inhibition (intermediate) and 0.4% ≥32 μg/mL (resistant). Among isolates of S. haemolyticus, 4.4% were of intermediate susceptibility (MIC 16 μg/mL) and 3.3% were resistant (MIC ≥32 μg/mL) to teicoplanin. However, this species represented only 6.3% of the isolates of coagulase-negative Staphylococcus spp. Generally, teicoplanin (mode MIC ≤0.12 μg/mL) was four to eight times more active than vancomycin (mode MIC ≤0.5 μg/mL) against the 770 streptococcal isolates. Glycopeptide-susceptible Enterococcus spp. (n = 1695) were generally four times more susceptible to teicoplanin (mode MIC 0.25 μg/mL) than to vancomycin (mode MIC 1 μg/mL). Combined vancomycin and teicoplanin (VanA phenotype) resistance was observed more frequently (9.3%) in isolates of Enterococcus faecium than in Enterococcus faecalis (0.8%). Four isolates of unspeciated enterococci (1.4%) also expressed this resistance phenotype. Four isolates of E. faecium and four of E. faecalis expressed the VanB-type (low-level, vancomycin only) resistance. Spain was the only country not to submit resistant E. faecium strains while resistant E. faecalis isolates came only from Spain and Italy.     

In vitro activity of the semisynthetic glycopeptide amide MDL 63,246.

The in vitro activity of the semisynthetic glycopeptide amide MDL 63,246 against 293 U.S. clinical isolates of gram-positive cocci was determined by the broth microdilution method. When compared with teicoplanin, MDL 63,246 had improved activity against Staphylococcus epidermidis (MICs that inhibited 90% strains tested [MIC90s], 0.25 versus 8 micrograms/ml, respectively). Staphylococcus haemolyticus (MIC90s, 1 versus 32 micrograms/ml, respectively), and VanA Enterococcus faecium (MIC90s, 32 versus > or = 1,024 micrograms/ml, respectively).     

Novel membrane proteins present in teicoplanin-resistant, vancomycin-sensitive, coagulase-negative Staphylococcus spp.

Clinical isolates of Staphylococcus epidermidis and Staphylococcus haemolyticus resistant to teicoplanin (MIC 64 mg/L) and sensitive to vancomycin (MIC 2 mg/L), were compared with vancomycin- and teicoplanin-sensitive isolates (MICs 1 mg/L) of the same species. No apparent differences between the sensitive and resistant strains of either pair were found with respect to binding of teicoplanin to the bacteria, or to the amino acid content or degree of cross-linkage of purified peptidoglycan. The resistant strains did not inactivate teicoplanin in the surrounding medium. Analysis of the membrane proteins of the resistant S. epidermidis strain grown in the presence or absence of sub-inhibitory levels of teicoplanin (4 mg/L), showed the presence of a 39 kDa protein which was either absent, or present in considerably reduced amounts, in the sensitive strain. Fractionation of cell components after lysis of protoplasts showed that the 39 kDa protein was present predominantly in the membrane fraction but also in small amounts in the wall fraction. Similar investigations with S. haemolyticus revealed the presence of a 35 kDa protein in membranes of the resistant strain: the amount was increased substantially by growth in sub-inhibitory levels of teicoplanin. Membranes prepared by mechanical disintegration of bacteria or by osmotic lysis of protoplasts showed large apparent differences in the amounts of the 39 kDa protein.     

In vitro antibacterial activity of LY333328, a new semisynthetic glycopeptide.

LY333328 is a semisynthetic N-alkyl derivative of LY264826, a naturally occurring structural analog of vancomycin. LY333328 was evaluated for its in vitro inhibitory and bactericidal activities in comparison with those of the two currently available glycopeptides (vancomycin and teicoplanin). Glycopeptide-susceptible test strains included a total of 311 isolates (most of clinical origin) from the genera Staphylococcus, Enterococcus, Streptococcus, Aerococcus, Gemella, Lactococcus, Listeria, Corynebacterium, and Clostridium. Test strains resistant or intermediate to vancomycin and/or teicoplanin included 56 clinical isolates of Enterococcus (of the VanA, VanB, and VanC phenotypes) and 32 clinical isolates of Staphylococcus (S. haemolyticus, S. epidermidis, and S. aureus), 31 strains of gram-positive genera outside the spectrum of activity of vancomycin (Leuconostoc, Pediococcus, Lactobacillus, and Erysipelothrix), and laboratory-derived organisms obtained after exposure of susceptible Staphylococcus isolates to teicoplanin (6 strains) or laboratory-derived organisms with resistance determinants received from VanA enterococci (2 Enterococcus and 25 Listeria transconjugants). LY333328 was highly active against staphylococci, enterococci, and listeriae (whether they were clinical or laboratory-derived strains) resistant to the currently available glycopeptides. In particular, the MICs of LY333328 did not vary substantially between teicoplanin-susceptible and teicoplanin-resistant staphylococci and between vancomycin-susceptible and vancomycin-resistant enterococci. LY333328 demonstrated fairly good inhibitory activity even against most strains of Leuconostoc, Pediococcus, and Erysipelothrix (MIC range, 1 to 8 microg/ml), whereas it proved less active (although much more active than vancomycin or teicoplanin) against Lactobacillus strains. In minimal bactericidal concentration (MBC) and time-kill studies, LY333328 demonstrated excellent bactericidal activity; enterococci, in particular, which were largely tolerant of vancomycin and teicoplanin, were uniformly killed by LY333328, with MBC-to-MIC ratios of 4 to 8 for most vancomycin-susceptible and vancomycin-resistant strains. In attempts to select for resistant clones, no survivors stably growing in the presence of 10 microg of LY333328 per ml were obtained from the Staphylococcus and Enterococcus test strains exposed to the drug.     

Activity of cephalosporins against coagulase-negative staphylococci

Staphylococcus epidermidis has become an increasingly important pathogen as the cause of serious postoperative infection after heart and orthopedic surgery. We studied the susceptibilities of 80 blood, sternotomy, and hip isolates to vancomycin, cefazolin, cefuroxime, oxacillin, erythromycin, ciprofloxacin, and ofloxacin. The MIC90 of methicillin-susceptible isolates was 4 micrograms/ml for cefazolin and cefamandole, 8 micrograms/ml for cefuroxime, and 4 micrograms/ml for vancomycin. At 48 hr the MIC90 rose to 32 micrograms/ml for cefazolin and greater than 128 micrograms/ml for cefuroxime, and remained at 4 micrograms/ml for cefamandole and vancomycin. The MIC90 of methicillin-resistant isolates at 48 hr was 16 micrograms/ml cefamandole, 64 micrograms/ml cefazolin, greater than 128 micrograms/ml cefuroxime, and 4 micrograms/ml vancomycin. Ciprofloxacin and ofloxacin inhibited the majority of isolates at 1 microgram/ml, and vancomycin at 4 micrograms/ml. The new peptolide, daptomycin, also inhibited S. epidermidis at less than or equal to 1 microgram/ml.