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Adamecz Z, Nielsen KL, Kirkby NS, Frimodt-Møller N. Aminoglycoside resistance genes in Enterococcus faecium: mismatch with phenotype. J Antimicrob Chemother 2021; 76:2215-2217. [PMID: 33969403 DOI: 10.1093/jac/dkab137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 04/07/2021] [Indexed: 11/13/2022] Open
Affiliation(s)
- Zsuzsanna Adamecz
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Karen Leth Nielsen
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
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Karslake J, Maltas J, Brumm P, Wood KB. Population Density Modulates Drug Inhibition and Gives Rise to Potential Bistability of Treatment Outcomes for Bacterial Infections. PLoS Comput Biol 2016; 12:e1005098. [PMID: 27764095 PMCID: PMC5072716 DOI: 10.1371/journal.pcbi.1005098] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/10/2016] [Indexed: 11/19/2022] Open
Abstract
The inoculum effect (IE) is an increase in the minimum inhibitory concentration (MIC) of an antibiotic as a function of the initial size of a microbial population. The IE has been observed in a wide range of bacteria, implying that antibiotic efficacy may depend on population density. Such density dependence could have dramatic effects on bacterial population dynamics and potential treatment strategies, but explicit measures of per capita growth as a function of density are generally not available. Instead, the IE measures MIC as a function of initial population size, and population density changes by many orders of magnitude on the timescale of the experiment. Therefore, the functional relationship between population density and antibiotic inhibition is generally not known, leaving many questions about the impact of the IE on different treatment strategies unanswered. To address these questions, here we directly measured real-time per capita growth of Enterococcus faecalis populations exposed to antibiotic at fixed population densities using multiplexed computer-automated culture devices. We show that density-dependent growth inhibition is pervasive for commonly used antibiotics, with some drugs showing increased inhibition and others decreased inhibition at high densities. For several drugs, the density dependence is mediated by changes in extracellular pH, a community-level phenomenon not previously linked with the IE. Using a simple mathematical model, we demonstrate how this density dependence can modulate population dynamics in constant drug environments. Then, we illustrate how time-dependent dosing strategies can mitigate the negative effects of density-dependence. Finally, we show that these density effects lead to bistable treatment outcomes for a wide range of antibiotic concentrations in a pharmacological model of antibiotic treatment. As a result, infections exceeding a critical density often survive otherwise effective treatments.
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Affiliation(s)
- Jason Karslake
- Department of Biophysics, University of Michigan, Ann Arbor, MI
| | - Jeff Maltas
- Department of Biophysics, University of Michigan, Ann Arbor, MI
| | - Peter Brumm
- Department of Biophysics, University of Michigan, Ann Arbor, MI
| | - Kevin B. Wood
- Department of Biophysics, University of Michigan, Ann Arbor, MI
- Department of Physics, University of Michigan, Ann Arbor, MI
- * E-mail:
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Draft Genome Sequence of a vanA-Type Vancomycin-Resistant Reference Strain, Enterococcus faecium ATCC 51559. GENOME ANNOUNCEMENTS 2015; 3:3/5/e01053-15. [PMID: 26358609 PMCID: PMC4566191 DOI: 10.1128/genomea.01053-15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vancomycin-resistant Enterococcus faecium has emerged as a multidrug-resistant pathogen in hospital settings. Here, we present the draft genome sequence of a high-level vancomycin-resistant strain, E. faecium ATCC 51559, which is employed as a standard laboratory vanA genotype-positive control strain for clinical and laboratory studies.
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Khan SA, Sung K, Layton S, Nawaz MS. Heteroresistance to vancomycin and novel point mutations in Tn1546 of Enterococcus faecium ATCC 51559. Int J Antimicrob Agents 2008; 31:27-36. [DOI: 10.1016/j.ijantimicag.2007.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 07/18/2007] [Accepted: 08/10/2007] [Indexed: 11/24/2022]
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Jung WK, Lim JY, Kwon NH, Kim JM, Hong SK, Koo HC, Kim SH, Park YH. Vancomycin-resistant enterococci from animal sources in Korea. Int J Food Microbiol 2006; 113:102-7. [PMID: 17010464 DOI: 10.1016/j.ijfoodmicro.2006.07.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 04/10/2006] [Accepted: 07/06/2006] [Indexed: 11/25/2022]
Abstract
Enterococci for which the minimum inhibitory concentration (MIC) of vancomycin was >/=8 mg/l were isolated from meat, feces, and raw milk samples collected in Korea from March to November 2003. Among the 243 vancomycin-resistant enterococci (VRE) that were identified the vanA vancomycin resistance gene was carried by 51 Enterococcus faecium and one Enterococcus sp., vanC1 was carried by 151 Enterococcus gallinarum, vanC2 was carried by 39 Enterococcus casseliflavus, and one Enterococcus sp. carried no van genes. Of the isolated enterococci carrying vanA, 4% were found to be highly resistant to gentamicin and 11% were resistant to ampicillin. Further genotyping of the E. faecium isolates carrying vanA using pulsed-field gel electrophoresis (PFGE) revealed extensive heterogeneity. The vancomycin resistance transferability test revealed that only two of the 52 enterococci carrying the vanA gene were able to transfer vancomycin resistance to other enterococci. The VRE were recovered from various animal sources with a particularly high prevalence of E. faecium carrying the vanA gene being found in poultry meat.
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Affiliation(s)
- Woo Kyung Jung
- Department of Microbiology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul, 151-742, Republic of Korea
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Boost M, Lai L, O'Donoghue M. Drug resistance in fecal enterococci in Hong Kong. J Infect Chemother 2004; 10:326-30. [PMID: 15614455 DOI: 10.1007/s10156-004-0337-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Accepted: 09/06/2004] [Indexed: 11/27/2022]
Abstract
Our purpose was to estimate the rate of carriage of vancomycin-resistant enterococci (VRE) in hospitalized patients in a district hospital and in healthy subjects in the community in Hong Kong. Rectal swabs were collected from all patients admitted to the intensive care unit, and stool specimens were collected from all patients presenting with suspected antibiotic-associated diarrhea over a 2-month period. Stool specimens were also collected from healthy subjects in the community. Specimens were enriched and cultured on selective media for the isolation of enterococci. All isolates were identified, and their minimum inhibitory concentration for vancomycin was determined. Susceptibility to other antibiotics was investigated. Samples yielded 125 isolates of enterococci, the majority of isolates being Enterococcus faecalis (75) and E. faecium (35). Nine of 11 strains of E. gallinarum and 2 of 2 strains of E. casseliflavus isolated from hospitalized patients were intermediately resistant to vancomycin, but no strains highly resistant to vancomycin were isolated. Resistance to other drugs, including the fluoroquinolones, was present, and a high-level resistance to gentamicin and streptomycin was found in 37% and 46% of strains, respectively. Colonization with VRE remains low in Hong Kong. This result is supported by the low level of isolation of VRE from infections in the region and may be attributable to low levels of vancomycin use. High-level aminoglycoside resistance and fluoroquinolone resistance are common, and continued monitoring for VRE is suggested.
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Affiliation(s)
- Maureen Boost
- Biomedical Science Section, School of Nursing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
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8
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Nayak R, Khan SA, Watson RH, Cerniglia CE. Influence of growth media on vancomycin resistance of Enterococcus isolates and correlation with resistance gene determinants. FEMS Microbiol Lett 2002; 214:159-63. [PMID: 12351224 DOI: 10.1111/j.1574-6968.2002.tb11340.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The effect of Mueller-Hinton (MH), MH+blood or brain heart infusion medium (agar or broth) on 13 Enterococcus isolates was determined, when testing their antibiotic susceptibility. Disk diffusion and Vitek methods were used to determine vancomycin resistance, while broth dilution and E-test methods were used to measure the minimum inhibitory concentration. The data were correlated with the presence of vancomycin resistance genes. A definite correlation pattern could not be established between the presence of van genes and vancomycin resistance in any plating medium, when tested by the disk diffusion assay. The broth dilution, irrespective of the plating medium, and Vitek methods were more reliable than the E-test method in testing isolates with vanA or vanB genes. However, for vanC2/C3 genotypes, the E-test method, irrespective of the plating medium, tested better than the broth dilution assay.
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Affiliation(s)
- Rajesh Nayak
- US Food and Drug Administration, National Center for Toxicological Research, Division of Microbiology, Jefferson, AR 72079, USA
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Gavaldà J, López P, Martín T, Gomis X, Ramírez JL, Azuaje C, Almirante B, Pahissa A. Efficacy of ceftriaxone and gentamicin given once a day by using human-like pharmacokinetics in treatment of experimental staphylococcal endocarditis. Antimicrob Agents Chemother 2002; 46:378-84. [PMID: 11796345 PMCID: PMC127055 DOI: 10.1128/aac.46.2.378-384.2002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We compared the efficacy of ceftriaxone combined with gentamicin, both given once a day, with that of cloxacillin given every 4 h plus gentamicin given once a day or in three daily doses (t.i.d.) for the treatment of experimental methicillin-susceptible staphylococcal endocarditis. The antibiotics were administered by using human-like (H-L) pharmacokinetics that simulated the profiles of these drugs in human serum. Animals with catheter-induced endocarditis were infected intravenously with 10(5) CFU of Staphylococcus aureus S5 (MICs and minimal bactericidal concentrations of cloxacillin, ceftriaxone, and gentamicin, 0.5 and 2 microg/ml, 4 and 8 microg/ml, and 0.5 and 1 microg/ml, respectively). The animals were then treated for 24 h with cloxacillin at a dose of 2 g that simulated H-L pharmacokinetics (H-L 2 g) every 4 h alone or combined with gentamicin (administered at doses of H-L 1 mg/kg of body weight every 8 h or H-L 4.5 mg/kg every 24 h) or with ceftriaxone at H-L 2 g every 24 h alone or combined with gentamicin (administered at doses of H-L 1 mg/kg every 8 h or H-L 4.5 mg/kg every 24 h). The results of therapy for experimental endocarditis due to the S5 strain showed that (i) cloxacillin alone is more effective than ceftriaxone alone in reducing the bacterial load (P < 0.01), (ii) the combination of cloxacillin or ceftriaxone with gentamicin is more effective than each of these drugs alone (P < 0.01), and (iii) Ceftriaxone H-L plus gentamicin H-L 4.5 mg/kg, both administered every 24 h, showed efficacy similar to that of the "gold standard," cloxacillin H-L plus gentamicin H-L 1 mg/kg t.i.d. (P > 0.05). An increase in the interval of administration of gentamicin to once daily resulted in a reduction in the numbers of bacteria in the vegetations equivalent to that achieved with the recommended regimen of cloxacillin plus gentamicin t.i.d. in the treatment of experimental endocarditis due to methicillin-susceptible S. aureus. Ceftriaxone plus gentamicin, both administered once a day, may be useful for home-based therapy for selected cases of staphylococcal endocarditis.
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Affiliation(s)
- Joan Gavaldà
- Infectious Diseases Research Laboratory, Infectious Diseases Division, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
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10
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López P, Gavaldà J, Martin MT, Almirante B, Gomis X, Azuaje C, Borrell N, Pou L, Falcó V, Pigrau C, Pahissa A. Efficacy of teicoplanin-gentamicin given once a day on the basis of pharmacokinetics in humans for treatment of enterococcal experimental endocarditis. Antimicrob Agents Chemother 2001; 45:1387-93. [PMID: 11302800 PMCID: PMC90478 DOI: 10.1128/aac.45.5.1387-1393.2001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
With the aim of investigating home therapy for enterococcal endocarditis, we compared the efficacy of teicoplanin combined with gentamicin given once a day or in three daily doses (t.i.d.) with the standard treatment, ampicillin plus gentamicin administered t.i.d., for treating experimental enterococcal endocarditis. The antibiotics were administered by using "human-like pharmacokinetics" (H-L), i.e, pharmacokinetics like those in humans, that simulated the profiles of these drugs in human serum. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of Enterococcus faecalis EF91 (MICs and MBCs of ampicillin, gentamicin, and teicoplanin, 0.5 and 32, 16 and 32, and 0.5 and 1 microg/ml, respectively) and were treated for 3 days with ampicillin H-L at 2 g every 4 h plus gentamicin H-L at 1 mg/kg every 8 h, or teicoplanin H-L at 10 mg/kg every 24 h, alone or combined with gentamicin, administered at dose of H-L at 1 mg/kg every 8 h or H-L at 4.5 mg/kg every 24 h. The results of therapy for experimental endocarditis due to EF91 showed that teicoplanin alone was as effective as ampicillin alone in reducing the bacterial load (P > 0.05). The combination of ampicillin or teicoplanin with gentamicin was more effective than the administration of both drugs alone in reducing the log(10)CFU/gram of aortic vegetation (P < 0.01 and P < 0.05, respectively). Teicoplanin plus gentamicin H-L at 4.5 mg/kg, both administered every 24 h, showed an efficacy equal to the "gold standard," ampicillin plus gentamicin H-L at 1 mg/kg t.i.d. (P > 0.05). Increasing the interval of administration of gentamicin to a single daily dose combined with teicoplanin resulted in a reduction of bacteria in the vegetations equivalent to that achieved with the recommended regimen of ampicillin plus thrice-daily gentamicin in the treatment of experimental endocarditis due to E. faecalis. Teicoplanin plus gentamicin, both administered once a day, may be useful home therapy for selected cases of enterococcal endocarditis.
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Affiliation(s)
- P López
- Infectious Diseases Research Laboratory, Infectious Diseases Division, Universitat Autònoma de Barcelona, Barcelona, Spain
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11
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Descheemaeker PR, Chapelle S, Devriese LA, Butaye P, Vandamme P, Goossens H. Comparison of glycopeptide-resistant Enterococcus faecium isolates and glycopeptide resistance genes of human and animal origins. Antimicrob Agents Chemother 1999; 43:2032-7. [PMID: 10428931 PMCID: PMC89409 DOI: 10.1128/aac.43.8.2032] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One hundred thirty-two glycopeptide-resistant Enterococcus faecium (GREF) isolates from different hospitals and pig and poultry farms in Belgium were compared on the basis of (i) their antibiotic susceptibilities, (ii) their SmaI pulsed-field gel electrophoresis (PFGE) patterns, and (iii) the organization of their Tn1546 or related elements in order to detect possible phenotypic and genotypic relationships among both groups of isolates. Human and animal vanA-positive GREF isolates were found to have similar susceptibility patterns; they remained susceptible to gentamicin and were, in general, susceptible to ampicillin. PFGE demonstrated a very high degree of genomic heterogeneity in both groups of isolates. However, indistinguishable isolates were found within different farms or hospitals, and in two instances, epidemiologically unrelated pig and human isolates showed indistinguishable PFGE patterns. In total, eight different transposon types were identified, and all were related to the prototype transposon Tn1546. The two predominant types, Tn1546 and type 2 transposons, which differed at three band positions, were present in both human and animal isolates. Type 2 transposons were significantly associated with pig isolates. The other types were seldom detected. These data suggest a possible exchange of glycopeptide resistance markers between animals and humans.
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Affiliation(s)
- P R Descheemaeker
- Belgian Reference Centre for Enterococci, Department of Microbiology, University Hospital Antwerp, Universitaire Instelling Antwerpen, Antwerp, University of Ghent, Ghent, Belgium.
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12
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Ieven M, Vercauteren E, Descheemaeker P, van Laer F, Goossens H. Comparison of direct plating and broth enrichment culture for the detection of intestinal colonization by glycopeptide-resistant enterococci among hospitalized patients. J Clin Microbiol 1999; 37:1436-40. [PMID: 10203501 PMCID: PMC84795 DOI: 10.1128/jcm.37.5.1436-1440.1999] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The results of prevalence studies on glycopeptide-resistant enterococci (GRE) in the intestine may be influenced by the detection methods applied. In most studies different media, different concentrations of antibiotics, and different methods are used, and these differences result in differences in recovery rates. In this cross-sectional study on the carrier state of GRE among patients at the University Hospital Antwerp, Antwerp, Belgium, performed on 21 May 1996, direct plating and broth enrichment were compared by using the same media. Stool samples (n = 213) or rectal swabs (n = 122) were plated directly on Enterococcosel agar (bioMérieux) and after enrichment in Enterococcosel broth. The prevalence of GRE was 12.8%. Direct plating recovered 53.4% of the GRE isolates, and broth enrichment recovered an additional 46.5% of them; in the latter test the isolates were thus present at less than 10(3) CFU per g of feces. The prevalence of GRE among dialysis patients was higher than among the other patients, but the difference was not significant (P = 0.06), possibly as a result of the small numbers of dialysis patients examined. The GRE species isolated included 19 E. gallinarum (44.2%), 13 E. faecium (30.2%), 6 E. faecalis (13.9%), and 5 E. casseliflavus (11.6%) isolates. All E. faecalis and E. faecium strains isolated carried the vanA gene, and E. gallinarum and E. casseliflavus carried the vanC1 and vanC2 gene, respectively. The majority of isolates were polyclonal. Our data indicate that the rate of detection of GRE from both stool samples and rectal swabs is significantly increased with enrichment cultures.
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Affiliation(s)
- M Ieven
- Laboratory for Microbiology, University Hospital Antwerp, B-2650 Edegem, Belgium.
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13
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Gavaldà J, Torres C, Tenorio C, López P, Zaragoza M, Capdevila JA, Almirante B, Ruiz F, Borrell N, Gomis X, Pigrau C, Baquero F, Pahissa A. Efficacy of ampicillin plus ceftriaxone in treatment of experimental endocarditis due to Enterococcus faecalis strains highly resistant to aminoglycosides. Antimicrob Agents Chemother 1999; 43:639-46. [PMID: 10049280 PMCID: PMC89173 DOI: 10.1128/aac.43.3.639] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/1998] [Accepted: 12/30/1998] [Indexed: 11/20/2022] Open
Abstract
The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10 Enterococcus faecalis strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg E. faecalis. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 micrograms/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 micrograms of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 micrograms of ceftriaxone per ml showed a > or = 2 log10 reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10 E. faecalis strains studied. This effect was obtained for seven strains with the combination of 2 micrograms of ampicillin per ml plus 10 micrograms of ceftriaxone per ml and for six strains with 5 micrograms of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of E. faecalis V48 or 10(5) CFU of E. faecalis V45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by E. faecalis V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (P < 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAg E. faecalis.
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Affiliation(s)
- J Gavaldà
- Infectious Diseases Research Laboratory, Hospital General Vall d'Hebron, Universitat Autònoma de Barcelona, Spain.
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15
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Struwig MC, Botha PL, Chalkley LJ. In vitro activities of 15 antimicrobial agents against clinical isolates of South African enterococci. Antimicrob Agents Chemother 1998; 42:2752-5. [PMID: 9756791 PMCID: PMC105933 DOI: 10.1128/aac.42.10.2752] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The activities of a panel of currently available antibiotics and the investigational agents LY 333328, linezolid, CL 331,002, CL 329,998, moxifloxacin (BAY 12-8039), trovafloxacin, and quinupristin-dalfopristin against 274 clinical isolates of enterococci were determined. No vancomycin resistance or beta-lactamase production was observed. Except for 12 isolates (all non-Enterococcus faecalis) showing reduced susceptibility to quinupristin-dalfopristin (MIC, >/=4 microg/ml), the new agents exhibited promising in vitro antienterococcal activity.
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Affiliation(s)
- M C Struwig
- Department of Medical Microbiology, University of the Orange Free State, Bloemfontein 9300, South Africa.
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Li RC, Ma HH. Parameterization of inoculum effect via mathematical modeling: aminoglycosides against Staphylococcus aureus and Escherichia coli. J Chemother 1998; 10:203-7. [PMID: 9669644 DOI: 10.1179/joc.1998.10.3.203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Inoculum effect describes the inoculum size dependent changes in minimum inhibitory concentrations (MIC) exhibited by antibiotic-bacterium combinations demonstrating such effect. Traditionally, inoculum effect has been loosely defined based on the extent of increase in the MIC with respect to the increase in inoculum size. In most studies, assessment of MIC data has relied on the arbitrary selection of a point of reference for both baseline MIC and inoculum size. More importantly, this conventional method of assessment does not permit information conveyed in a complete MIC versus inoculum size profile to be fully explored. To undertake these issues, a mathematical model was developed for the description of the entire inoculum effect profile. With the employment of three key parameter estimates, i.e., the baseline MIC, the threshold inoculum size at which the increase in MIC commences, and the rate of increase in MIC with respect to inoculum size, both the shape and location of the profile could be adequately defined. To verify the application of this model, a series of four aminoglycosides were tested against standard strains of E. coli and S. aureus. Results showed a good degree of organism specificity and antibiotic-class dependency of the inoculum effect profiles. Analysis of the parameter estimates obtained provided further support for these observations. In conclusion, the mathematical model developed in the present study adequately described the inoculum effect exhibited by the various aminoglycoside-bacterium combinations tested. The parameter estimates generated by the modeling approach allowed comparison and quantitative analysis of the inoculum effect profiles with minimal difficulties.
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Affiliation(s)
- R C Li
- Department of Pharmacy, Faculty of Medicine, The Chinese University of Hong Kong, Shatin.
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Bhat KG, Paul C, Bhat MG. Neonatal bacteremia due to high level aminoglycoside resistant (HLAR) enterococci. Indian J Pediatr 1997; 64:537-9. [PMID: 10771884 DOI: 10.1007/bf02737764] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
A study was conducted to determine the drug resistance pattern of enterococci isolated from cases of neonatal bacteremia. A total of 41 strains of enterococci were isolated of which 35 (85.4%) were Enterococcus faecalis and 6 (14.6%) were Enterococcus faecium. A total of 3 (8.6%) strains of E. faecalis and 2 (33.3%) E. faecium strains showed high level aminoglycoside resistance (HLAR). None of the enterococci tested were vancomycin resistant. Drug resistance was more common among E. faecium strains. All clinically significant isolates of enterococci should be tested for their antibiotic sensitivity pattern including HLAR, and for treatment, antibiotics are selected based on in vitro antibiotic sensitivity test results.
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Affiliation(s)
- K G Bhat
- Department of Microbiology, Kasturba Medical College, Mangalore, Karnataka
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18
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Vandamme P, Vercauteren E, Lammens C, Pensart N, Ieven M, Pot B, Leclercq R, Goossens H. Survey of enterococcal susceptibility patterns in Belgium. J Clin Microbiol 1996; 34:2572-6. [PMID: 8880522 PMCID: PMC229320 DOI: 10.1128/jcm.34.10.2572-2576.1996] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A national surveillance study was performed in order to identify the enterococci causing important infections, to determine their susceptibilities to first-choice agents for treatment, and to characterize the phenotypes and genotypes of the glycopeptide-resistant strains. A total of 472 isolates were collected between 15 January and 15 April 1993. The ability of the API rapid ID 32 STREP gallery to identify enterococci was evaluated. The majority of the Belgian enterococci were identified as E. faecalis (89.4%). E. faecium and other enterococci were present in small percentages only (9.1 and 1.5%, respectively). The API rapid ID 32 STREP system identified 88.6% of the strains with an excellent or very good identification score. For the majority of the strains with uncertain identification scores, the results of a single test only were aberrant. Only 2.3% of the strains remained unidentified. High-level aminoglycoside resistance was widespread in E. faecalis (streptomycin, 50.8%; gentamicin, 8.7%), and the emergence of ciprofloxacin resistance was found to be associated with aminoglycoside resistance. E. faecium is generally more resistant to a wide range of antibiotics, but glycopeptide-resistant strains (1.5%) have not yet become widespread.
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Affiliation(s)
- P Vandamme
- Department of Microbiology, University Hospital UIA, Antwerp, Belgium.
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19
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Abstract
OBJECTIVE To review vancomycin resistance in enterococci (Enterococcus faecalis and Enterococcus faecium) with respect to history, epidemiology, mechanism of resistance, and management. DATA SOURCES A MEDLINE, IDIS, and current journal search of English-language articles on vancomycin-resistant enterococci (VRE) published between 1982 and 1994 was conducted. STUDY SELECTION Studies and reports pertaining to vancomycin-resistant E. faecalis and E. faecium were evaluated. Case reports, cohort, epidemiologic, in vitro and in vivo studies were evaluated. DATA EXTRACTION Reports in which vancomycin minimum inhibitory concentrations were 32 micrograms/mL or more were evaluated. DATA SYNTHESIS Large outbreaks of VRE infection have occurred as a result of nosocomial spread. Such outbreaks have required intensive infection control procedures to limit the spread of VRE. Vancomycin resistance in E. faecalis and E. faecium has been subdivided into phenotypes, VanA and VanB. The mechanism of vancomycin resistance is caused by the production of depsipeptide D-Ala-D-Lac, which replaces D-Ala-D-Ala in the peptidoglycan pathway, thereby preventing the binding of vancomycin to D-Ala-D-Ala in the peptidoglycan cell wall. The vanA gene is associated with a transpositional element (Tn1546) that can be transferred via conjugation while most data suggest that vanB has an endogenous origin. Education, aggressive infection control practices. surveillance programs, and appropriate use of vancomycin are necessary to respond to the VRE problem. CONCLUSIONS The prevalence of VRE has increased significantly in recent years and has become a worldwide problem. Several factors, such as prior exposure to vancomycin and antibotics (e.g., cephalosporins, antianaerobic agents), physical location in the hospital, immunosuppression, prolonged hospital stay, and VRE gastrointestinal colonization are associated with VRE infection and colonization. Antibiotic treatment of serious VRE infection depends on the phenotype. Optimal treatment of the VanA phenotype is unknown; the VanB phenotype may be treated with teicoplanin and an aminoglycoside.
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Affiliation(s)
- A S Gin
- Department of Pharmaceutical Services, Health Sciences Centre, Winnipeg, Manitoba, Canada
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20
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Swenson JM, Ferraro MJ, Sahm DF, Clark NC, Culver DH, Tenover FC. Multilaboratory evaluation of screening methods for detection of high-level aminoglycoside resistance in enterococci. National Committee for Clinical Laboratory Standards Study Group on Enterococci. J Clin Microbiol 1995; 33:3008-18. [PMID: 8576363 PMCID: PMC228624 DOI: 10.1128/jcm.33.11.3008-3018.1995] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Since the early 1970s, the synergistic activity of an aminoglycoside with a cell wall-active agent has been predicted by determining the ability of an enterococcus to grow in the presence of high levels of the aminoglycoside (usually > or = 2,000 micrograms/ml). However, a variety of media and concentrations of aminoglycosides has been used for this screening procedure. In the present study, we sought to optimize the agar dilution, broth microdilution, and disk diffusion tests used to detect high-level gentamicin and streptomycin resistance in enterococci. For dilution tests, brain heart infusion agar or broth gave the best growth and performance. For agar dilution, 500 micrograms of gentamicin per ml, 2,000 micrograms of streptomycin per ml, and an inoculum of 1 x 10(6) CFU/ml were optimal, while for broth microdilution, 500 micrograms of gentamicin per ml, 1,000 micrograms of streptomycin per ml, and an inoculum of 5 x 10(5) CFU/ml were best. Growth of more than one colony in the agar dilution test was determined to be the best indicator of high-level resistance. For disk diffusion, Mueller-Hinton agar, 120-micrograms gentamicin disks, and 300-micrograms streptomycin disks with breakpoints of no zone for resistance and > or = 10 mm for susceptibility gave the best sensitivity and specificity if results for strains with zones of 7 to 9 mm are considered inconclusive, indicating that a broth or agar test should be performed to determine susceptibility or resistance.
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Affiliation(s)
- J M Swenson
- Hospital Infections Program, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA
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21
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Torres C, Tenorio C, Lantero M, Zarazaga M, Baquero F. Detection of aminoglycoside-penicillin synergy against Enterococcus faecium using high-content aminoglycoside disks. Eur J Clin Microbiol Infect Dis 1995; 14:878-82. [PMID: 8605901 DOI: 10.1007/bf01691494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Thirty-seven Enterococcus faecium strains were screened for high-level aminoglycoside resistance with an agar diffusion test using high-content aminoglycoside disks (300 micrograms of streptomycin and 120 micrograms of gentamicin, tobramycin, kanamycin or amikacin). The inhibition zones obtained were correlated with results of time-kill penicillin-aminoglycoside synergy studies. An 11 mm breakpoint differentiated strains susceptible or resistant to the synergy of streptomycin plus penicillin. Irrespective of the inhibition zones obtained with tobramycin and kanamycin disks, Enterococcus faecium strains never showed synergy with penicillin in combination with these aminoglycosides. Penicillin-amikacin synergy cannot be predicted by the amikacin disks. Nevertheless, even though kanamycin disks do not predict penicillin-kanamycin synergy, they can be used to predict penicillin-amikacin synergy. In summary, high-content streptomycin, gentamicin and kanamycin disks can be used to predict the susceptibility of Enterococcus faecium strains to the synergistic combination of penicillin plus one of the aminoglycosides (streptomycin, gentamicin or amikacin, respectively).
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Affiliation(s)
- C Torres
- Area Bioquímica y Biología Molecular, Luis de Ulloa 20, Universidad de la Rioja, Logroño, Spain
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22
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Free L, Sahm DF. Investigation of the reformulated Remel Synergy Quad plate for detection of high-level aminoglycoside and vancomycin resistance among enterococci. J Clin Microbiol 1995; 33:1643-5. [PMID: 7650204 PMCID: PMC228234 DOI: 10.1128/jcm.33.6.1643-1645.1995] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We investigated the accuracy of the recently released Remel Synergy Quad plate, a commercially available agar screening method for detecting high-level aminoglycoside and vancomycin resistance among enterococci that is based on the National Committee for Clinical Laboratory Standards recommended guidelines (National Committee for Clinical Laboratory Standards, M7-A3, 1993). The Synergy Quad correctly determined the gentamicin and streptomycin resistance status for > or = 97% of 147 Enterococcus faecalis and Enterococcus faecium isolates tested. Detection of vancomycin resistance also was reliable, as no false susceptibility occurred with 36 vancomycin-resistant E. faecalis and E. faecium strains and false resistance occurred only once with the 47 susceptible strains tested. One strain each of Enterococcus gallinarum and Enterococcus casseliflavus failed to grow on the screen, but because the true nature and significance of resistance in such isolates is unknown the implication of their screen negativity is uncertain. In summary, the Remel Synergy Quad provides a highly accurate and convenient method for susceptibility testing of enterococci against gentamicin, streptomycin, and vancomycin.
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Affiliation(s)
- L Free
- Department of Pathology, Jewish Hospital of St. Louis, MO 63110, USA
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23
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Sahm DF. Emerging trends in antimicrobial resistance: a laboratory perspective. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 390:141-54. [PMID: 8718609 DOI: 10.1007/978-1-4757-9203-4_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- D F Sahm
- Department of Pathology, Washington University School of Medicine, St. Louis, MO, USA
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24
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Antony SJ, Matherin P, Stratton C. Increased bactericidal activity as documented by serum bactericidal titers for a triple combination of cell wall active agents against gentamicin-resistant enterococci. SCANDINAVIAN JOURNAL OF INFECTIOUS DISEASES 1995; 27:401-3. [PMID: 8658079 DOI: 10.3109/00365549509032740] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Infections caused by entercocci have become increasingly difficult to treat because these bacteria are becoming increasingly resistant to commonly used antibiotics such as ampicillin, gentamicin and vancomycin. A consensus for an optimal therapy of enterococcal infections caused by resistant isolates has not yet been determined. We present a patient with prolonged enterococcal sepsis in whom a combination of ampicillin, vancomycin and imipenem was ultimately successful in suppressing enterococcal bacteremia. The enhanced activity of this triple combination was documented by the results of serial serum bactericidal titers.
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Affiliation(s)
- S J Antony
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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25
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Al-Ballaa SR, Qadri SM, Al-Ballaa SR, Kambal AM, Saldin H, Al-Qatary K. High level resistance to aminoglycosides in enterococci from Riyadh. Ann Saudi Med 1994; 14:290-3. [PMID: 17586920 PMCID: PMC6363522 DOI: 10.5144/0256-4947.1994.290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Enterococci with high level of aminoglycosides resistance are being reported from different parts of the world with increasing frequency. Treatment of infections caused by such isolates is associated with a high incidence of failure or relapse. This is attributed to the loss of the synergetic effect of aminoglycosides and cell wall active agents against isolates exhibiting this type of resistance. To determine the prevalence of enterococci with high level resistance to aminoglycosides in Riyadh, Saudi Arabia, 241 distinct clinical isolates were examined by disk diffusion method using high content aminoglycosides disks. Seventy-four isolates (30%) were resistant to one or more of the aminoglycosides tested. The most common pattern of resistance was that to streptomycin and kanamycin. Of the 241 isolates tested, 29 (12%) were resistant to high levels of gentamicin, 35 (15%) to tobramycin, 65 (27%) to kanamycin and 53 (22%) to streptomycin. The highest rate of resistance to a high level of gentamicin was found among enterococcal blood isolates (30%). Eighteen of the isolates were identified as Enterococcus faecium, 13 (72%) of these showed high level resistance to two or more of the aminoglycosides tested.
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Affiliation(s)
- S R Al-Ballaa
- Departments of Medicine, Pathology and Microbiology, King Saud University, and Department of Pathology, Section of Clinical Microbiology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
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26
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Sahm DF, Gilmore MS. Transferability and genetic relatedness of high-level gentamicin resistance among enterococci. Antimicrob Agents Chemother 1994; 38:1194-6. [PMID: 8067764 PMCID: PMC188178 DOI: 10.1128/aac.38.5.1194] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Gentamicin resistance in six enterococcal species was investigated. Transfer of resistance was observed for the donors E. faecium UC 79, E. avium CC 54, and E. gallinarum B 51, but not for E. raffinosus UC 78 or E. casseliflavus UC 73. Except for E. casseliflavus UC 73, homology was observed between the E. faecalis aac6'-aph2" gene and DNA from other species. Whereas 2.6-kb HindIII fragments encoded resistance in E. faecalis UC 244, its transconjugant, and E. raffinosus UC 78, 3.4-kb fragments encoded resistance in E. faecium UC 79, E. gallinarum B 51, and their transconjugants. A 3.4-kb fragment encoded resistance in E. avium CC 54, but 2.6-kb fragments encoded resistance in the transconjugants. Although many similarities were found among the strains, the heterogeneity in gentamicin resistance exhibited by some isolates indicates diversity among these determinants.
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Affiliation(s)
- D F Sahm
- Division of Microbiology and Serology, Jewish Hospital, Washington University Medical Center, St. Louis, Missouri 63110
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27
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Wiland AM, Plaisance KI, Schwalbe RS. In vitro evaluation of high-level, gentamicin-resistant enterococci isolated from bacteremic patients. Pharmacotherapy 1994; 14:89-94. [PMID: 8159604 DOI: 10.1002/j.1875-9114.1994.tb02791.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We attempted to characterize the susceptibility of high-level, gentamicin-resistant (HLGR, minimum inhibitory concentration [MIC] > 2000 micrograms/ml) enterococcal blood isolates and evaluated a small subset of these isolates for bactericidal synergy. Thirteen Enterococcus faecalis and three Enterococcus faecium isolates that were HLGR were prospectively collected. Standard broth macrodilution techniques were used to determine the MICs and minimum bactericidal concentrations to a variety of antibiotics. Two isolates were evaluated for synergy by time-kill curve methods using combinations of penicillin and streptomycin, teicoplanin and rifampin, and vancomycin and ciprofloxacin. Teicoplanin was the most active antibiotic tested, with all isolates exhibiting susceptibility to this agent. Four E. faecalis isolates and one E. faecium isolate expressed only low-level resistance to streptomycin (LLSR, MICs 32-64 micrograms/ml). Penicillin and streptomycin produced bactericidal synergy in the LLSR isolate. The other antibiotic combinations did not result in bactericidal synergy in the two isolates tested. For HLGR enterococci that are only LLSR, the combination of penicillin-streptomycin appears to provide adequate bactericidal activity. Teicoplanin may potentially be useful for streptomycin-resistant HLGR isolates.
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Affiliation(s)
- A M Wiland
- University of Maryland Medical System, Baltimore
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28
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Torres C, Tenorio C, Lantero M, Gastañares MJ, Baquero F. High-level penicillin resistance and penicillin-gentamicin synergy in Enterococcus faecium. Antimicrob Agents Chemother 1993; 37:2427-31. [PMID: 8285628 PMCID: PMC192403 DOI: 10.1128/aac.37.11.2427] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Thirty-seven Enterococcus faecium strains with different levels of penicillin susceptibility were studied in time-kill experiments with a fixed concentration (5 micrograms/ml) of gentamicin combined with different penicillin concentrations (6 to 600 micrograms/ml). Synergy was defined as a relative decrease in counts of greater than 2 log10 CFU per milliliter after 24 h of incubation when the combination of the antibiotics was compared with its most active component alone. The minimal synergistic penicillin concentrations found were 6 micrograms/ml for 16 of 16 strains for which penicillin MICs were < or = 25 micrograms/ml, 20 to 100 micrograms/ml for 14 of 17 strains for which penicillin MICs were 50 to 200 micrograms/ml, and 200 to 500 micrograms/ml for 4 of 4 strains for which MICs penicillin were > 200 micrograms/ml. Penicillin-gentamicin synergy was observed even in high-level penicillin-resistant E. faecium strains at penicillin concentrations close to one-half the penicillin MIC. The possibility of treating infections caused by high-level penicillin-resistant E. faecium strains with penicillin-gentamicin combinations in particular cases may depend on the penicillin levels attainable in vivo.
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Affiliation(s)
- C Torres
- Area de Bioquímica y Biología Molecular, Universidad de la Rioja, Madrid, Spain
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29
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Chiew YF, Lim SW, Kuah BG, Liew HY. Prevalence in Singapore of enterococci with high-level resistance to aminoglycosides and comparison of three methods for their detection. J Infect 1993; 27:125-31. [PMID: 8228292 DOI: 10.1016/0163-4453(93)94593-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The first study of the prevalence in Singapore of enterococci with high-level resistance to aminoglycosides has been made in the National University Hospital. From March to June 1992, 225 isolates were studied by means of three methods: (1) use of brain-heart infusion (BHI) agar incorporating the antibiotic; (2) microdilution of the antibiotic in broth; and (3) use of high content antibiotic discs. The BHI agar was the reference method. Of the total, 49 (22%) isolates were resistant to gentamicin, 86 (38%) to streptomycin, 82 (36%) to kanamycin and 93 (41%) to one or more of the agents. Results of the disc diffusion method correlated completely with the BHI agar method. The broth microdilution method showed a 100, 90 and 96% sensitivity in relation to gentamicin, streptomycin and kanamycin, respectively, and a specificity of 100% for all three aminoglycosides. Statistical significance (P < 0.01 to P < 0.001) was demonstrated in (1) a greater incidence of enterococci with high-level resistance to aminoglycosides among blood isolates; (2) gentamicin resistance predicting kanamycin high-level resistance; and (3) more resistance to gentamicin, streptomycin and kanamycin among Enterococcus faecium isolates compared to those of Enterococcus faecalis. Beta-lactamase activity was not detected.
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Affiliation(s)
- Y F Chiew
- Department of Laboratory Medicine, National University Hospital, Singapore
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30
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Torres C, Torres JM, Tenorio C, Baquero F. Synergistic activity of tobramycin-netilmicin against Enterococcus faecalis producing 6'-aminoglycoside-acetyltransferase, 2''-aminoglycoside-phosphotransferase enzyme. Eur J Clin Microbiol Infect Dis 1993; 12:646-8. [PMID: 8223671 DOI: 10.1007/bf01973652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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31
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Bantar CE, Micucci M, Fernandez Canigia L, Smayevsky J, Bianchini HM. Synergy characterization for Enterococcus faecalis strains displaying moderately high-level gentamicin and streptomycin resistance. J Clin Microbiol 1993; 31:1921-3. [PMID: 8349776 PMCID: PMC265661 DOI: 10.1128/jcm.31.7.1921-1923.1993] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Synergy of 14 Enterococcus faecalis strains displaying moderately high-level aminoglycoside resistance (MICs, 500 and 256 to 1,000 micrograms/ml for gentamicin and streptomycin, respectively) was characterized by time-kill studies. All strains proved resistant to penicillin plus the respective aminoglycoside. Strains with moderately high-level aminoglycoside resistance should be considered to exhibit high-level resistance in severe infections.
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Affiliation(s)
- C E Bantar
- Laboratorio de Bacteriología Clínica, Centro de Educación Médica e Investigaciones Clínicas, Buenos Aires, Argentina
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32
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Venditti M, Tarasi A, Gelfusa V, Nicastri E, Penni A, Martino P. Antimicrobial susceptibilities of enterococci isolated from hospitalized patients. Antimicrob Agents Chemother 1993; 37:1190-2. [PMID: 8517714 PMCID: PMC187931 DOI: 10.1128/aac.37.5.1190] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
One hundred and one isolates of Enterococcus species isolated recently from hospitalized patients were evaluated in vitro for antibiotic susceptibility. Teicoplanin and mideplanin were the most active agents, followed by ramoplanin, vancomycin, ciprofloxacin, ampicillin, and imipenem. High-level resistance to gentamicin (MIC > 500 micrograms/ml) and/or streptomycin (MIC > 2,000 micrograms/ml) was found in 60 isolates. High-level resistance to ampicillin (MIC > or = 16 micrograms/ml) was found in 17 isolates. MBC studies revealed that ramoplanin possesses significant bactericidal activity.
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Affiliation(s)
- M Venditti
- Servizio Aggregato di Consulenze Infettivologiche, Policlinico Umberto I, Rome, Italy
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33
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Venditti M, Tarasi A, Visco Comandini U, Gentile G, Girmenia C, Micozzi A, Martino P. Enterococcal septicemia in patients with hematological malignancies. Eur J Clin Microbiol Infect Dis 1993; 12:241-7. [PMID: 8513811 DOI: 10.1007/bf01967253] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Thirty-six cases of enterococcal septicemia in patients with hematological malignancies were reviewed retrospectively and categorized according to their clinical significance using strict previously described definitions. Overall, most of the infected patients were males (77%), had acute leukemia (64%), had recently received cytotoxic drug therapy (86%), were granulocytopenic at the onset of septicemia (77%), and acquired the infection during hospitalization (77%). The source of septicemia was unknown in 18 (50%) patients, intestinal in 15 (42%) and intravascular in three (8%). Mortality was 19% among 21 inpatients who had clinically significant septicemia and 30% among patients with septicemia of uncertain clinical significance. The fatal outcome could be definitively attributed to enterococcal septicemia in only one of the nine inpatients who died. Clinically significant septicemia appeared somewhat more frequently to be polymicrobial (p = 0.06), whereas septicemia of unknown significance presented more frequently as breakthrough septicemia (p = 0.013). Unless associated with intravascular infection, enterococcal septicemia in patients with hematological malignancies seems to represent a marker of cytotoxic drug damage of the intestinal mucosa rather than a truly invasive infection.
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Affiliation(s)
- M Venditti
- Servizio Aggregato di Consulenze Infettivologiche, Università La Sapienza, Rome, Italy
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34
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Chiew YF, Tosaka M, Yamane N. Prevalence of enterococcal high-level aminoglycoside resistance in Japan. Comparative detection by three methods. Diagn Microbiol Infect Dis 1993; 16:145-8. [PMID: 8467628 DOI: 10.1016/0732-8893(93)90011-u] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A total of 250 strains of enterococci isolated in Kumamoto University Hospital, Japan, during the period from January to March 1992 were tested for high-level aminoglycoside resistance. Brain-heart infusion (BHI) agar plates supplemented with 1000 micrograms/ml of gentamicin or 2000 micrograms/ml of streptomycin detected 164 (66%) isolates resistant to either gentamicin or streptomycin alone, or both, and consisted of 107 (43%) resistant to gentamicin and 96 (38%) resistant to streptomycin. The Vitek Gram-Positive Susceptibility card (GPS-TA) revealed high correlations with those by agar screens, the results indicating a sensitivity of 100% and 99% to gentamicin and streptomycin, respectively, and 100% specificity to both. Also, the microdilution tests of the National Committee for Clinical Laboratory Standards (NCCLS) showed 100% and 92% sensitivity to gentamicin and streptomycin, respectively, and no false resistance (100% specificity) when compared with the results by agar screens.
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Affiliation(s)
- Y F Chiew
- Department of Laboratory Medicine, Kumamoto University Medical School, Japan
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35
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Hindler J, Sahm D. Controversies and confusion regarding antimicrobial susceptibility testing of enterococci. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0738-1751(92)90012-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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36
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Harvey BS, Baker CJ, Edwards MS. Contributions of complement and immunoglobulin to neutrophil-mediated killing of enterococci. Infect Immun 1992; 60:3635-40. [PMID: 1500172 PMCID: PMC257371 DOI: 10.1128/iai.60.9.3635-3640.1992] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Enterococci have become a frequent causative agent in neonatal sepsis. The relative contributions of antibody and complement and their interactions in the neutrophil-mediated bacterial killing of 11 Enterococcus strains from neonates were investigated. Polymorphonuclear leukocytes (PMNL) from adult and term newborn infants were tested with normal human serum, adult hypogammaglobulinemic serum, and normal newborn serum in a neutrophil bactericidal assay. Neutrophil bactericidal activity for enterococci was not influenced by the serum source but was essentially ablated after heat inactivation of complement in all sera. No differences were observed in the killing capacity of healthy newborn versus adult PMNL regardless of serum source. Representative Enterococcus strains were then tested with agammaglobulinemic serum or C4-deficient serum, resulting in neutrophil bactericidal activities consistently exceeding 90%. A neutrophil bactericidal assay performed with normal rabbit serum and hyperimmune rabbit serum against enterococci showed that antibodies to enterococci enhanced neutrophil-mediated killing of this organism. Thus, neutrophil killing of enterococci appears to be mediated primarily by complement, with antibody playing a less essential but potentially important role. PMNL from adult and healthy term infants functioned with equal efficiency in the neutrophil killing of enterococci.
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Affiliation(s)
- B S Harvey
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030
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37
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Leclercq R, Bismuth R, Duval J. New high-content disks for determination of high-level aminoglycoside resistance in clinical isolates of Enterococcus faecalis. Eur J Clin Microbiol Infect Dis 1992; 11:356-60. [PMID: 1396758 DOI: 10.1007/bf01962078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Disks impregnated with 500 and 1000 micrograms of streptomycin, 1000 micrograms of kanamycin and 250 and 500 micrograms of gentamicin were used for detection of high-level resistance to aminoglycosides in 120 clinical isolates of Enterococcus faecalis. Fifty-seven strains were highly resistant to streptomycin, 80 to kanamycin and 41 to gentamicin. Using disks containing 500 micrograms of streptomycin, 1000 micrograms of kanamycin and 500 micrograms of gentamicin strains resistant to high levels of these drugs (97.9%, 100% and 100%, respectively) were accurately detected. Better discrimination between high-level and low-level resistance was achieved with a 500 micrograms streptomycin or gentamicin disk. Zone-size breakpoints are proposed for detection of high-level resistance by disk diffusion.
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Affiliation(s)
- R Leclercq
- Service de Bactériologie-Virologie-Hygiène, Hôpital Henri Mondor, Université Paris, France
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38
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Nicastri E, Tarasi A, Visco Comandini U, Gelfusa V, Di Rosa R, Di Rosa E, Venditti M, Serra P. High-level aminoglycoside resistance among enterococci: evaluation of an agar screen susceptibility test. J Chemother 1992; 4:9-11. [PMID: 1403074 DOI: 10.1080/1120009x.1992.11739130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Seventy-five enterococci from infected (63 isolates) and colonized (12 isolates) patients hospitalized in various divisions of the Policlinico Umberto I, University of Rome, were in vitro studied for high-level resistance (HLR) to gentamicin (HLRG) and streptomycin (HLRS) with adoption of a standard broth dilution and an agar screen test. The employed procedures provided equal results for 100% of the 75 isolates. Of these, 21 (28%) showed HLRG and 43 (57%) HLRS. Combined HLRG and HLRS were found in 18 (24%) isolates, whereas HLRS or HLRG alone were found in 25 (33%) and 3 (4%) isolates respectively. It is concluded that HLR to aminoglycosides may represent a major problem in Italian institutions. Along with other established procedures, the agar screen test employed in the study may be used to detect this antibiotic resistance in enterococci.
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Affiliation(s)
- E Nicastri
- Patologia Medica II, Policlinico Umberto I, Università degli Studi, La Sapienza, Roma, Italy
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39
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Metchock B, McGowan JE. Evaluation of the Vitek GPS-TA card for laboratory detection of high-level gentamicin and streptomycin resistance in enterococci. J Clin Microbiol 1991; 29:2870-2. [PMID: 1757562 PMCID: PMC270450 DOI: 10.1128/jcm.29.12.2870-2872.1991] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Vitek GPS-TA card (Vitek Systems, Hazelwood, Mo.) was compared with single-concentration broth microdilution and disk diffusion methods using high-content disks for the detection of high-level resistance to gentamicin and streptomycin in 99 isolates of enterococci (81 Enterococcus faecalis isolates and 18 Enterococcus faecium isolates). The GPS-TA card accurately detected high-level resistance to gentamicin, but not streptomycin, in E. faecalis. When streptomycin is being considered for therapy, either disk diffusion or time-kill studies should be used to confirm susceptible results obtained by Vitek testing. Additional studies are needed to determine the best method for testing E. faecium isolates.
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Affiliation(s)
- B Metchock
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia
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40
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Sahm DF, Boonlayangoor S, Schulz JE. Detection of high-level aminoglycoside resistance in enterococci other than Enterococcus faecalis. J Clin Microbiol 1991; 29:2595-8. [PMID: 1774267 PMCID: PMC270379 DOI: 10.1128/jcm.29.11.2595-2598.1991] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The ability of six screening methods to detect high-level aminoglycoside resistance in enterococcal species other than Enterococcus faecalis was investigated. The 85 Enterococcus isolates, which included 55 E. faecium, 11 E. gallinarum, 9 E. casseliflavus, 5 E. raffinosus, 4 E. avium, and 1 E. mundtii, were tested by using aminoglycoside-supplemented brain heart infusion agar (BHI), Remel EF Synergy Quad plates, high-content aminoglycoside diffusion disks, standard (prepared in-house) microdilution panels, Pasco MIC Gram Positive microdilution panels, and Vitek GPS-TA cards. When tested on BHI, 32 and 35 strains showed resistance to gentamicin and streptomycin, respectively. Resistance profiles obtained with Remel EF Synergy Quad plates were in complete agreement with those obtained on BHI. However, growth on Mueller-Hinton agar-based plates was not as heavy. Some isolates showed only weak growth and required 48 h for resistance to become evident, especially with swab inoculation of quadrants containing 2,000 micrograms of gentamicin per ml. Profiles obtained by use of the agar-based screens were used as the basis for evaluating the other methods. Disk diffusion showed complete agreement. No false resistance occurred by either microdilution method, but 48 h of incubation was needed for detection of some gentamicin-resistant isolates, and 14% of the streptomycin-resistant strains were not detected by standard microdilution. The Vitek GPS-TA card detected 81 and 100% of the gentamicin- and streptomycin-resistant isolates, respectively. In general, most methods used to detect high-level aminoglycoside resistance in E. faecalis appear to be reliable for the testing of the other enterococcal species. However, further investigations with a greater number of resistant E. raffinosus, E. avium, and E. mundtii isolates, when they are available, will be useful for establishing the full range of enterococci that can reliably be tested by the various methods.
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Affiliation(s)
- D F Sahm
- Clinical Microbiology Laboratories, University of Chicago Medical Center, Illinois 60637
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Sahm DF, Boonlayangoor S, Iwen PC, Baade JL, Woods GL. Factors influencing determination of high-level aminoglycoside resistance in Enterococcus faecalis. J Clin Microbiol 1991; 29:1934-9. [PMID: 1774318 PMCID: PMC270238 DOI: 10.1128/jcm.29.9.1934-1939.1991] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The ability of seven methods to detect high-level gentamicin (58 strains) and streptomycin resistance (56 strains) among 107 Enterococcus faecalis isolates was investigated at the University of Chicago Medical Center and the University of Nebraska Medical Center. Methods included a standard agar screen plate, high-content disk diffusion, Remel (Lenexa, Kans.) EF Synergy Quad plates, standard microdilution panels prepared in house, Pasco MIC Gram-Positive panels (Difco Laboratories, Detroit, Mich.), MicroScan MIC Type 5 dry panels (Baxter Healthcare Corp., MicroScan Div., West Sacramento, Calif.), and Vitek GPS-TA cards (Vitek Systems Inc., Hazelwood, Mo.). Results indicating false resistance were not obtained by any method, and there was 100% agreement between the results of the disk diffusion and standard agar screen methods. Prolonging incubation from 24 to 48 h increased resistance detection for both agar and microdilution screens. EF Synergy Quad plates inoculated with micropipettes detected 100% of the streptomycin- and gentamicin-resistant isolates. Resistance detection for streptomycin and gentamicin, respectively, was 93 and 96% by standard microdilution, 93 and 98% by Pasco panels, 88 and 89% by MicroScan panels, and 88 and 91% by Vitek GPS-TA cards. False susceptibility occurred more frequently with streptomycin-resistant isolates than it did with gentamicin-resistant strains and appeared to be strain related in some instances. The use of an increased inoculum size enhanced resistance detection with these strains, but it complicated interpretation of results and led to the selection of streptomycin-resistant mutants. Until results of further studies delineate optimum test conditions, a delay in the final interpretation of agar and microdilution screen results until 48 h for isolates showing no or light growth at 24 h may help to minimize the occurrence of false susceptibility reporting.
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Affiliation(s)
- D F Sahm
- Clinical Microbiology Laboratories, University of Chicago Medical Center, Illinois 60637
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42
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Szeto S, Louie M, Low DE, Patel M, Simor AE. Comparison of the new MicroScan Pos MIC Type 6 panel and AMS-Vitek Gram Positive Susceptibility Card (GPS-TA) for detection of high-level aminoglycoside resistance in Enterococcus species. J Clin Microbiol 1991; 29:1258-9. [PMID: 1907610 PMCID: PMC271972 DOI: 10.1128/jcm.29.6.1258-1259.1991] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We compared the MicroScan Pos MIC Type 6 panel and AMS-Vitek Gram Positive Susceptibility Card (GPS-TA) to agar dilution screen plates for the detection of high-level aminoglycoside resistance in 182 enterococcal isolates. The specificity of the two commercial systems was 100%, with the exception of one susceptible isolate found to be streptomycin resistant by the Vitek system. The MicroScan and Vitek systems had comparable sensitivities for the detection of gentamicin resistance (90 and 95% respectively) and streptomycin resistance (85 and 78%, respectively). These results suggest that screening tests such as agar dilution screen plates, broth dilution, or disk diffusion should continue to be used to detect high-level gentamicin and streptomycin resistance.
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Affiliation(s)
- S Szeto
- Department of Microbiology, Mount Sinai Hospital, University of Toronto, Ontario, Canada
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Weissmann D, Spargo J, Wennersten C, Ferraro MJ. Detection of enterococcal high-level aminoglycoside resistance with MicroScan freeze-dried panels containing newly modified medium and Vitek Gram-Positive Susceptibility cards. J Clin Microbiol 1991; 29:1232-5. [PMID: 1907609 PMCID: PMC269975 DOI: 10.1128/jcm.29.6.1232-1235.1991] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Both conventional and modified MicroScan Type 5 panels and Vitek Gram-Positive Susceptibility cards were compared with agar dilution screen plates for their abilities to detect high-level resistance to gentamicin and streptomycin in 235 enterococcal isolates, including 167 Enterococcus faecalis and 63 E. faecium isolates. The modified Type 5 panels contained dextrose-phosphate broth instead of Mueller-Hinton broth in their high-level-resistance screen wells. The sensitivities for detection of gentamicin and streptomycin high-level resistance were 100 and 100% (E. faecalis) and 100 and 94% (E. faecium) for the modified MicroScan panels, 100 and 89% (E. faecalis) and 100 and 98% (E. faecium) for the conventional MicroScan panels, and 81 and 86% (E. faecalis) and 85 and 94% (E. faecium) for the Vitek cards. All specificities were 100% except for the Vitek cards with streptomycin, where it was 96%. Isolates that showed resistance on the streptomycin agar screen plates were rescreened on plates containing 32,000 micrograms/ml to detect ribosomally mediated resistance. For all three systems, every failure to detect streptomycin high-level resistance occurred in isolates with enzymatic, not ribosomal, resistance. The modified MicroScan Type 5 panels are a suitable method for detecting enterococcal high-level resistance to gentamicin and streptomycin. The Vitek cards are too insensitive for this purpose.
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Affiliation(s)
- D Weissmann
- Department of Pathology, Massachusetts General Hospital, Boston 02114
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Herman DJ, Gerding DN. Screening and treatment of infections caused by resistant enterococci. Antimicrob Agents Chemother 1991; 35:215-9. [PMID: 2024952 PMCID: PMC244979 DOI: 10.1128/aac.35.2.215] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- D J Herman
- Department of Medicine, Veterans Affairs Medical Center, Minneapolis, Minnesota
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Affiliation(s)
- D J Herman
- Department of Medicine, Veterans Affairs Medical Center, Minneapolis, Minnesota
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46
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Yagupsky P, Petry S, Menegus MA. Comparison of four methods for testing high-level aminoglycoside resistance in enterococci. Eur J Clin Microbiol Infect Dis 1990; 9:133-5. [PMID: 2318217 DOI: 10.1007/bf01963639] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In a prospective study the prevalence of high-level aminoglycoside resistance (MIC greater than or equal to 2,000 micrograms/ml) among 62 clinically significant enterococci was investigated. A total of 10(5) organisms were inoculated a) onto a plate containing 2,000 micrograms/ml of gentamicin or streptomycin; b) into a microtube for dilution MIC determinations for gentamicin, amikacin, tobramycin and streptomycin; and c) into a single tube containing 500 micrograms/ml of gentamicin, amikacin, tobramycin or streptomycin in supplemented Mueller-Hinton broth. In addition, tubes containing 500 micrograms/ml of gentamicin, amikacin, tobramycin or streptomycin were inoculated with five enterococcal colonies ("crude" method). For 45 of the 62 isolates, MICs of gentamicin, amikacin and tobramycin were less than or equal to 500 micrograms/ml, while 17 (27%) showed high-level resistance. The MICs of streptomycin were less than or equal to 500 micrograms/ml for 42 of 62 isolates, and greater than or equal to 2,000 micrograms/ml for 20 (32.3%). For 8 of the 17 (47%) isolates showing high-level gentamicin resistance, MICs of streptomycin were less than or equal to 500 micrograms/ml. There was complete agreement between the results of the plate method, the microtube dilution MIC and the tube inoculated with 10(5) CFU, but the crude method gave discordant results for two isolates. It is concluded that a tube containing 500 micrograms/ml of aminoglycoside is a simple, accurate and inexpensive method for determining high-level aminoglycoside resistance.
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Affiliation(s)
- P Yagupsky
- Department of Clinical Microbiology, University of Rochester Medical Center, New York 14642
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Abstract
Enterococci are important human pathogens that are increasingly resistant to antimicrobial agents. These organisms were previously considered part of the genus Streptococcus but have recently been reclassified into their own genus, called Enterococcus. To date, 12 species pathogenic for humans have been described, including the most common human isolates, Enterococcus faecalis and E. faecium. Enterococci cause between 5 and 15% of cases of endocarditis, which is best treated by the combination of a cell wall-active agent (such as penicillin or vancomycin, neither of which alone is usually bactericidal) and an aminoglycoside to which the organism is not highly resistant; this characteristically results in a synergistic bactericidal effect. High-level resistance (MIC, greater than or equal to 2,000 micrograms/ml) to the aminoglycoside eliminates the expected bactericidal effect, and such resistance has now been described for all aminoglycosides. Enterococci can also cause urinary tract infections; intraabdominal, pelvic, and wound infections; superinfections (particularly in patients receiving expanded-spectrum cephalosporins); and bacteremias (often together with other organisms). They are now the third most common organism seen in nosocomial infections. For most of these infections, single-drug therapy, most often with penicillin, ampicillin, or vancomycin, is adequate. Enterococci have a large number of both inherent and acquired resistance traits, including resistance to cephalosporins, clindamycin, tetracycline, and penicillinase-resistant penicillins such as oxacillin, among others. The most recent resistance traits reported are penicillinase resistance (apparently acquired from staphylococci) and vancomycin resistance, both of which can be transferred to other enterococci. It appears likely that we will soon be faced with increasing numbers of enterococci for which there is no adequate therapy.
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Sahm DF, Kissinger J, Gilmore MS, Murray PR, Mulder R, Solliday J, Clarke B. In vitro susceptibility studies of vancomycin-resistant Enterococcus faecalis. Antimicrob Agents Chemother 1989; 33:1588-91. [PMID: 2554802 PMCID: PMC172707 DOI: 10.1128/aac.33.9.1588] [Citation(s) in RCA: 418] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Vancomycin resistance exhibited by Enterococcus faecalis isolates V583, V586, and V587 is described. The vancomycin MICs ranged from 32 to 64 micrograms/ml. Although resistant to vancomycin, the isolates were susceptible to teicoplanin (MIC, less than or equal to 0.5 micrograms/ml). Such a glycopeptide susceptibility profile has not been previously described for E. faecalis. Time kill studies showed that vancomycin resistance adversely affected the synergistic activity that vancomycin and aminoglycoside combinations usually demonstrate against enterococci. However, the ability to detect vancomycin resistance varied with the susceptibility testing method used. Whereas broth microdilution, broth macrodilution, and agar dilution methods detected resistance, disk-agar diffusion and the AutoMicrobic system Gram-Positive GPS-A susceptibility card (Vitek Systems Inc., Hazelwood, Mo.) did not. To detect vancomycin resistance reliably and establish the incidence of such E. faecalis isolates, adjustments in some susceptibility testing methods may be necessary.
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Affiliation(s)
- D F Sahm
- Clinical Microbiology Laboratory, University of Chicago, Illinois 60637-1463
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Sahm DF, Koburov GT. In vitro activities of quinolones against enterococci resistant to penicillin-aminoglycoside synergy. Antimicrob Agents Chemother 1989; 33:71-7. [PMID: 2496659 PMCID: PMC171423 DOI: 10.1128/aac.33.1.71] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The MICs and MBCs of CI-934, ciprofloxacin, difloxacin (A-56619), A-56620, norfloxacin, enoxacin, amifloxacin, and coumermycin were determined for 43 clinical isolates of Enterococcus faecalis known to be resistant to penicillin-aminoglycoside synergy. Results were compared with those obtained for 37 synergy-susceptible E. faecalis and 22 Enterococcus faecium strains. Although no substantial differences in quinolone activities were observed between synergy-resistant and -susceptible E. faecalis strains, CI-934 and ciprofloxacin were the drugs that demonstrated the greatest bactericidal activity against both types of E. faecalis. The MBCs of the other quinolones were generally within a single twofold dilution of the MICs, but their antienterococcal activity did not approach that of CI-934 or ciprofloxacin. The MBCs for 90% of the isolates of CI-934 for synergy-resistant and -susceptible E. faecalis strains were 1 and less than or equal to 0.5 microgram/ml, respectively. The ciprofloxacin MBC for 90% of the E. faecalis strains tested was 1 microgram/ml. For E. faecium isolates the CI-934 and ciprofloxacin MBCs for 90% of the isolates were 8 and 4 micrograms/ml, respectively. Time-kill assays performed with synergy-susceptible enterococcal strains showed that the bactericidal activities of both CI-934 and ciprofloxacin were less than those of the penicillin-aminoglycoside combinations tested. However, against synergy-resistant isolates the activities of these two quinolones were comparable with and sometimes greater than those of penicillin-aminoglycoside combinations.
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Affiliation(s)
- D F Sahm
- Clinical Microbiology Laboratories, University of Chicago Medical Center, Illinois 60637
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50
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Spiegel CA. Laboratory detection of high-level aminoglycoside-aminocyclitol resistance in Enterococcus spp. J Clin Microbiol 1988; 26:2270-4. [PMID: 3148633 PMCID: PMC266874 DOI: 10.1128/jcm.26.11.2270-2274.1988] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Methods for detection of high-level resistance to aminoglycoside-aminocyclitol antibiotics were evaluated using 104 blood isolates of enterococci (97 Enterococcus faecalis and 7 Enterococcus faecium). Kanamycin was used to predict resistance to amikacin. Discrepancies between methods were resolved by time-kill studies. Four methods (MicroScan, macrotube, microtiter, and disk diffusion) for detecting resistance to gentamicin and streptomycin were compared, using 51 consecutive strains. There were 13 gentamicin-resistant strains, all of which were detected by macrotube, microtiter, and disk diffusion. MicroScan detected 2 (15%) of the 13. Of the 18 streptomycin-resistant strains, 17 (93%) were detected by disk diffusion, 16 (89%) by microtiter, 9 (50%) by macrotube, and 6 (33%) by MicroScan. An additional 53 consecutive strains were examined only by disk diffusion and microtiter for resistance to gentamicin, streptomycin, and kanamycin. The entire population of 104 strains contained 35 gentamicin-, 22 streptomycin-, and 54 kanamycin-resistant enterococcal isolates. All 35 gentamicin-resistant strains were detected by both methods. Of the 22 streptomycin-resistant strains, 1 was detected only by microtiter, 2 only by disk diffusion, and 19 by both methods. Of the 54 kanamycin-resistant strains, 1 was detected only by microtiter, 2 only by disk diffusion, and 51 by both methods. One additional strain which was resistant only by disk diffusion was susceptible to amikacin plus penicillin by time-kill studies. Disk diffusion is a suitable method for detection of high-level aminoglycoside-aminocyclitol resistance in E. faecalis and is well suited for sporadic testing. Additional data are necessary to determine the suitability of these tests for E. faecium.
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Affiliation(s)
- C A Spiegel
- University of Wisconsin Hospital and Clinics, Clinical Science Center, Madison 53791-9452
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