In vitro activity of linezolid against multiply resistant Gram-positive clinical isolates

The in vitro activity of the oxazolidinone linezolid was compared with the activities of vancomycin and teicoplanin against 450 Gram-positive clinical isolates, including a variety of multiply resistant strains. Linezolid inhibited all microorganisms tested at < or = 4 mg/L, including methicillin- and teicoplanin-resistant staphylococci, glycopeptide-resistant enterococci, penicillin- and multiply resistant pneumococci and viridans streptococci, and erythromycin-resistant beta-haemolytic streptococci. The MIC(90) of linezolid for all isolates was 2 mg/L.     

The in vitro activity of daptomycin against 514 Gram-positive aerobic clinical isolates

The in vitro activity of daptomycin was assessed in comparison with that of vancomycin and penicillin against a wide range of Gram-positive aerobic clinical isolates. MICs were determined by an agar dilution method on Mueller-Hinton agar (NCCLS/EUCAST) and on Isotonic agar adjusted to contain 50 mg/L free calcium (BSAC). Both media were enriched with 5% horse blood for fastidious organisms. Daptomycin MICs for all 172 staphylococci, including methicillin-susceptible and methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus haemolyticus, were 0.03-0.5 mg/L. For 99 of the 100 enterococci (Enterococcus faecalis, n = 50; Enterococcus faecium, n = 50), including 37 vancomycin-resistant isolates, they were 0.25-2 mg/L. For all 108 beta-haemolytic streptococci, including Streptococcus pyogenes and Streptococcus agalactiae, daptomycin MICs were 0.016- 0.25 mg/L; for 101 alpha-haemolytic streptococci, including Streptococcus pneumoniae and 'viridans' streptococci, they were 0.016-2 mg/L. For miscellaneous vancomycin-resistant isolates including Lactobacillus spp., Lactococcus spp., Leuconostoc spp., Pediococcus spp. and isolates of Enterococcus casseliflavus and Enterococcus gallinarum, daptomycin MICs were 0.03-2 mg/L; MICs for the seven isolates of Listeria monocytogenes were 0.25-4 mg/L. There was little difference between the results on Mueller-Hinton agar and on supplemented Isotonic agar The discrepant results occasionally obtained tended to be one dilution higher on supplemented Isotonic agar. Daptomycin was active (MICs < or = 2 mg/L) against all the isolates tested with the exception of one isolate each of E. faecium and L. monocytogenes (MICs = 4 mg/L). Our results indicate that daptomycin MICs are independent of methicillin and vancomycin MICs.     

Comparative in vitro activity of ceftriaxone against clinical bacterial isolates in Nigeria

The in vitro activity of ceftriaxone, a cephalosporin derivative, recently introduced in Nigeria was compared with the activities of other related beta-lactam antibiotics such as cefotaxime, cefuroxime, cephaloridine, cloxacillin/ampicillin and ampicillin against 530 local clinical isolates of gram-negative and gram-positive bacteria. The spectra of activity and potency of ceftriaxone and cefotaxime were generally similar against the Enterobacteriaceae, Pseudomonas aeruginosa, Serratia spp., Streptococcus spp. and Neisseria gonorrhoeae, but less active against Staphylococcus aureus and Staphylococcus epidermidis when compared to cefotaxime. All the other beta-lactam antibiotics tested were less active than ceftriaxone. The action of ceftriaxone was bactericidal and the minimum inhibitory concentration values observed with R-plasmid beta-lactamase mediated resistant Escherichia coli, Klebsiella spp., Proteus spp. and N. gonorrhoeae strains did not exceed the maximum value obtained with the beta-lactamase-negative strains.     

In vitro activity of linezolid, clarithromycin and moxifloxacin against clinical isolates of Mycobacterium kansasii

OBJECTIVES: To compare the activity of linezolid with a range of drugs used in the treatment of Mycobacterium kansasii infections. RESULTS: The percentages of resistant isolates against isoniazid, rifampicin and ethambutol were 2.9%, 1.9% and 2.9%, respectively. All isolates were susceptible to clarithromycin and moxifloxacin both with MIC(90) values of 0.125 mg/L. Linezolid was active against all isolates with MIC(50) and MIC(90) values of 0.5 and 1 mg/L, respectively, both below the susceptibility breakpoint established for mycobacteria. CONCLUSION: Linezolid, clarithromycin or moxifloxacin, could be used as alternative drugs for treatment of infections due to rifampicin-resistant isolates as well as short-course or intermittent therapy of M. kansasii lung disease.     

米诺环素、替加环素对多重耐药菌的体外抗菌活性比较

目的评价米诺环素、替加环素对多重耐药的耐甲氧西林金葡菌(MRSA)、肠球菌和鲍曼不动杆菌的体外抗菌活性。方法采用微量肉汤稀释法测定临床分离的多重耐药细菌对米诺环素、替加环素的敏感性。结果多重耐药的1 55株鲍曼不动杆菌,99株(63.9%)对米诺环素敏感,39株(25.2%)对米诺环素耐药,17株(11.0%)对米诺环素中介。75株多重耐药MRSA,50株(66.7%)对米诺环素敏感,20株(26.7%)对米诺环素中介,5株(6.7%)为耐药株。93株多重耐药屎肠球菌中36株(38.7%)对米诺环素敏感,57株(61.3%)对米诺环素耐药。39株粪肠球菌中25株(64.1%)对米诺环素敏感。75株MRSA对替加环素100%敏感,132株肠球菌100%敏感。5株耐万古霉素屎肠球菌和4株产新德里金属β内酰胺酶不动杆菌全部对替加环素敏感,MRSA和肠球菌对替加环素敏感性为100%。结论替加环素对米诺环素耐药的肠球菌和MRSA有很好的体外抗菌活性,替加环素对米诺环素耐药的鲍曼不动杆菌的抗菌活性也不理想。     

Comparative in vitro activity of levofloxacin and ofloxacin against Gram-positive bacteria

The in vitro activity of levofloxacin against 506 Gram-positive bacteria was compared with those of D(−)-ofloxacin, ofloxacin, ciprofloxacin, and sparfloxacin. Levofloxacin was generally twice as active as ofloxacin against these organisms (range, 0–3 twofold dilutions). Sparfloxacin appeared to have the greatest activity overall, but for several groups of organisms minimum inhibitory concentrations (MIC₉₀s) of this com pound were within one twofold dilution of those of levofloxacin. Resistance to levofloxacin (MIC⩾8 μg/ml) was not encountered among streptococcal species, was rare in methicillin-susceptible staphylococci (1.7%), and was infrequent in vancomycin-susceptible Enterococcus faecalis and Enterococcus faecium (8.7%). Resistance was more common among vancomycin-resistant enterococci and methicillin-resistant staphylococci.     

Comparative in vitro activity of three fluoroquinolones against clinical isolates by E test

The in vitro susceptibility of levofloxacin, ciprofloxacin and moxifloxacin against several gram-positive and gram-negative clinical isolates was tested by E test. We found that the MIC(50) and MIC(90) values against all members of the Enterobacteriaceae family except Serratia were <0.5 mg/l for ciprofloxacin and levofloxacin (MIC range 0.006-32 mg/l) based on the in vitro susceptibility data. The susceptibility rates for ciprofloxacin and levofloxacin were more than 85% for Escherichia coli, citrobacter, enterobacter cloacae, enterobacter aerogenes and Klebsiella pneumoniae, although Serratia and Acinetobacter exhibited more or less similar susceptibility rates (about 80%). Pseudomonas aeruginosa demonstrated significant resistance to fluoroquinolones (MIC(90) >32 mg/l) and decreased bactericidal rates (<65%) to levofloxacin and ciprofloxacin. Respiratory pathogens such as Streptococcus pneumoniae and Haemophilus influenzae were highly susceptible (100%) to levofloxacin and moxifloxacin. The ineffectiveness of fluoroquinolones for treating coagulase-positive Staphylococcus aureus was demonstrated by poor in vitro susceptibility rates with levofloxacin (52%) and moxifloxacin (57%). Coagulase-negative staphylococci demonstrated significantly decreased bactericidal rates to levofloxacin (21%), while the in vitro susceptibility to moxifloxacin was higher (66%) than that to levofloxacin. We propose that the beneficial effect of inclusion of any of these three fluoroquinolones in treating Enterococcus infections is marginal, as demonstrated by significantly reduced susceptibility rates (<32%). These data demonstrate the utility of fluoroquinoles to treat several gram-negative bacterial infections (with the exception of Acinetobacter and P. aeruginosa), as well as S. pneumoniae and H. influenzae.     

Comparative in vitro activity of gemifloxacin against gram-positive and gram-negative clinical isolates in Argentina

The in vitro activity of gemifloxacin against 1,000 clinical isolates of 147 Streptococcus pneumoniae (115, penicilin susceptible; 26, intermediate penicillin-resistant and 6, penicillin-resistant), 127 Hemophilus influenzae (109, β lactamasa non-producer; 18, β lactamase producers), 95 Streptococcus pyogenes (6, azytromycin-resistant), 84 Moraxella catarrhalis (79, β lactamase producers), 110 Staphilococcus aureus (89, methicillin-susceptible; 21, methicilin-resistant), 98 Eenterococcus faecalis and 339 Enterobacteriacea, (recovered from patients with respiratory tract infection; skin and soft tissue infection and urinary tract infection), was compared with the activities of four fluorquinolones and five other antimicrobial agents. Of the quinolones tested, gemifloxacin was the most potent against Streptococcus pneumoniae, including penicillin intermediate and resistant strains. Mic₉₀ values obtained for gemifloxacin, ciprofloxacin, ofloxacin, levofloxacin and trvafloxacin were 0.03, 2, 2, 1 and 0.25 mg/L respectively. Gemifloxacin was 16 fold more potent than ciprofloxacin against methicillin-susceptible Staphylococcus aureus and 32 fold more potent than ciprofloxacin against Streptococcus pyogenes. When tested against Hemophilus influenzae, Moraxella catarrhalis and Enterobacteriaceae, all the quinolones showed similar activity. Our results demonstrate that gemifloxacin has similar activity than the other quinolones tested against Gram-negative organisms and is considerably more potent against Gram-positive organisms.     

Multicenter in vitro comparative study of fluoroquinolones against 25,129 Gram-positive and Gram-negative clinical isolates

In vitro activities of fleroxacin, ciprofloxacin, ofloxacin, and lomefloxacin were evaluated against 25,129 fresh bacterial isolates from 51 US hospital or medical center laboratories, beginning in October of 1990. Susceptibility rates were ⩾85% against most species of Gram-negative bacteria. Notable exceptions were Pseudomonas, Acinetobacter, Xanthomonas, and Providencia. The study drugs displayed similar activity against most Gram-negative species. At least 90% of oxacillin-susceptible staphylococci were susceptible but, of oxacillin-resistant strains, only approximately 60% of Staphylococcus epidermidis and 25% of Staphylococcus aureus were susceptible to the quinolones tested. Staphylococcus saprophyticus strains were less susceptible to fleroxacin (42%) than to the other compounds (79%–97%). Ofloxacin and ciprofloxacin were more active against streptococci, and none of the compounds demonstrated appreciable activity against enterococci. Thus, the spectra of activity of fluoroquinolones illustrate that they remain effective agents for the treatment of many types of infections caused by Gram-negative pathogens.     

Comparative in vitro activity of seven quinolones against 100 clinical isolates of Clostridium difficile.

The in vitro activity of seven quinolone derivatives against 100 clinical isolates of Clostridium difficile was determined. CI934 was the most active, inhibiting 90% of the strains at 4 micrograms/ml and 100% at 8 micrograms/ml. Ofloxacin and ciprofloxacin had moderate activity (16 and 32 micrograms/ml) whereas enoxacin, pefloxacin, norfloxacin, and nalidixic acid had poor activity (128 micrograms/ml).     

In vitro activity of the new quinolone moxifloxacin (Bay 12-8039) against resistant gram-positive clinical isolates

The novel 8-methoxyquinolone, moxifloxacin (Bay 12-8039), was compared with ciprofloxacin and eight other antimicrobials for activity against 425 strains Gram-positive clinical isolates, including 73 methicillin-resistant staphylococci, 35 vancomycin-resistant enterococci, and 80 penicillin- or eythromycin-resistant streptococci. Overall, 82% of the strains were inhibited at ≤2 μg/mL. Moxifloxacin was more active than ciprofloxacin against staphylococci (8- to 32-fold), enterococci (0- to 16-fold), pneumococci (16-fold) and other streptococci (4- to 16-fold) when MIC₉₀ results were compared. Moxifloxacin demonstrated good activity against all Gram-positive isolates tested except for ciprofloxacin-resistant enterococci (MIC₉₀, 32 μg/mL) and methicillin-resistant staphylococci (MIC₉₀, 8 μg/mL). Clinical trials should be initiated to define the role of this new quinolone.     

阿莫西林-双氯西林的体外抗菌作用研究

目的评价阿莫西林-双氯西林对常见感染临床分离菌的体外抗菌作用.方法收集临床分离菌按CLSI/NCCLS推荐的琼脂对倍稀释法测定阿莫西林-双氯西林的最低抑菌浓度（MIC）,并与相关抗菌药物进行比较.结果收集临床分离菌共513株,其中需氧革兰阳性菌248株,需氧革兰阴性菌265株.阿莫西林-双氯西林对受试的需氧革兰阳性球菌,包括肺炎链球菌、化脓性链球菌等链球菌属、甲氧西林敏感葡萄球菌、粪肠球菌具有高度抗菌活性,大多与阿莫西林-克拉维酸相仿,亦优于其他受试药,该药对卡他莫拉菌、流感嗜血杆菌抗菌作用强,其中对流感嗜血杆菌的产酶株作用略差;对伤寒沙门菌具有良好抗菌作用,对大肠埃希菌、肺炎克雷伯菌、奇异变形杆菌和志贺菌的抗菌作用较差.结论阿莫西林-双氯西林对社区获得的上、下呼吸道感染和单纯性皮肤软组织感染的常见病原菌具有良好抗菌作用,对伤寒沙门菌作用亦强,提示该药为治疗上述感染的适宜选用药物之一.     

头孢地尼对临床分离菌的体外抗菌活性

目的:测定头孢地尼体外抗菌活性并与其他抗菌药比较。方法:采用琼脂稀释法测定抗生素最低抑菌浓度(MIC)。结果:651株细菌测定结果表明,头孢地尼对甲氧西林敏感金黄色葡萄球菌、表皮葡萄球菌(MSSA、MSSE)抗菌作用与头孢唑林、头孢呋辛相似,较头孢他啶强;对 MSSA、MSSE的 MIC90分别为 1、0.5 mg/L,细菌敏感率分别为 97%、100%。耐甲氧西林金黄色葡萄球菌、表皮葡萄球菌(MRSA、MRSE)、肠球菌对本药耐药,MIC90分别为＞128mg/L、8mg/L、＞128mg/L。头孢地尼对革兰阴性菌抗菌活性与头孢他啶相似,对大肠埃希菌、肺炎克雷伯菌、伤寒杆菌、痢疾杆菌、奇异变形杆菌MIC90分别为 2、4、1、0.25与 2 mg/L,敏感率分别为 85%、88%、100%、100%、88%,对部分细菌抗菌活性较阿米卡星、左氧氟沙星、司帕沙星强。聚团肠杆菌、阴沟肠杆菌、粘质沙雷菌、醋酸钙不动杆菌、铜绿假单胞菌对本药耐药,MIC90均＞128 mg/L。结论:头孢地尼对甲氧西林敏感葡萄球菌属、常见肠杆菌科细菌具强大的抗菌作用。     

Comparative in vitro activity of sanguinarine against oral microbial isolates.

MICs of sanguinarine were determined for 52 oral reference strains and 129 fresh isolates from human dental plaque. Sanguinarine was found to completely inhibit the growth of 98% of the isolates at a concentration of 16 micrograms/ml.     

In vitro activity of daptomycin against clinical isolates ofGram-positive bacteria

We determined the activity of daptomycin, a recently FDA-approved antimicrobial agent, against clinical isolates of Gram-positive bacteria, including viridans group streptococci (16 Streptococcus mitis species group, 12 S. mutans species group, 9 S. anginosus species group, 8 S. sanguinis species group, 5 S. salivarius species group) from patients with infective endocarditis, 32 methicillin-resistant Staphylococcus aureus, 32 high-level penicillin-resistant Streptococcus pneumoniae, 38 vancomycin-resistant enterococci (including 1 linezolid-resistant isolate), and thefollowing unusual Gram-positive bacteria: 3 Listeria monocytogenes, 4 Erysipelothrix rhusiopathiae, 9 Corynebacterium species, 10 Abiotrophia/Granulicatella species, 2 Rothia (Stomatococcus) mucilaginosus, and 4 Gemella morbillorum. Daptomycin minimum inhibitory concentration (MIC)₉₀ values for the viridans group streptococci, methicillin-resistant S. aureus, penicillin-resistant S. pneumoniae, and Enterococcus species were 0.5, 0.5, ≤0.125, and 4 µg/ml, respectively. The daptomycin MIC range for the unusual Gram-postitive bacteria was ≤0.125–2 µg/ml. We conclude that daptomycin has in vitro activity against viridans group streptococci associated with endocarditis as well as against several types of unusual Gram-positive bacteria that can cause endocarditis.Presented in part at the 13^th European Congress of Clinical Microbiology and Infectious Diseases, Glasgow, 2003 and at the 44^th ICAAC, Washington, DC, 2004     

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.     

Comparative in vitro activity of PGE 9262932 and fluoroquinolones against Canadian clinical Streptococcus pneumoniae isolates, including molecularly characterized ciprofloxacin-resistant isolates

OBJECTIVES: The aim of this study was to assess the in vitro activity of the non-fluorinated quinolone PGE 9262932 against Streptococcus pneumoniae isolates with various resistance phenotypes: ciprofloxacin-resistant, macrolide-resistant, penicillin-resistant and trimethoprim/sulfamethoxazole-resistant. METHODS: The in vitro activity of PGE 9262932 against 2585 recent Canadian S. pneumoniae isolates with various resistance phenotypes was determined and compared with that of gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin. In particular, the activity of PGE 9262932 against ciprofloxacin-resistant isolates with defined parC and gyrA mutations was assessed. RESULTS: PGE 9262932 MIC90s were < or = 0.015 mg/L for all S. pneumoniae and 0.12 mg/L for the ciprofloxacin-resistant isolates. Resistance to penicillin, macrolides or trimethoprim/sulfamethoxazole had little effect on the PGE 9262932 MICs. The quinolone MIC50/90s were only slightly affected by the presence of one parC or gyrA mutation, but increased 2- to 16-fold in the presence of mutations in both parC and gyrA, depending on the specific quinolone. With each quinolone resistance genotype, the order of activity, based on MIC90, against the ciprofloxacin-resistant isolates was PGE 9262932, gemifloxacin, moxifloxacin, gatifloxacin and levofloxacin. CONCLUSIONS: PGE 9262932 was the most active quinolone against all S. pneumoniae isolates, regardless of resistance phenotype.