Experimental Group B Streptococcal Endocarditis Treated with Penicillin G versus Ceftizoxime

Bayer, Arnold S.; Morrison, Joan O.; Kim, Kwang Sik

doi:10.1159/000238219

Cited by 6 publications

(1 citation statement)

References 19 publications

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“…Our findings that a relative lack of agreement exists between the checkerboard and time-kill methods are consistent with those of other investigators (2)(3)(4)(5). There is significant evidence that time-kill studies more aptly reflect the clinical outcome (3,35).…”

Section: Discussionsupporting

confidence: 87%

In vitro activities of antimicrobial combinations against Stenotrophomonas (Xanthomonas) maltophilia

Poulos

Matsumura

Willey

et al. 1995

Antimicrob Agents Chemother

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Stenotrophomonas (Xanthomonas) maltophilia is inherently resistant to multiple antimicrobial agents. In order to investigate the in vitro potential of combinations of antimicrobial agents, we obtained 230 epidemiologically unrelated clinical isolates from seven hospitals across Canada and from Northwestern Memorial Hospital in Chicago. Ticarcillin-clavulanate combined with ciprofloxacin or trimethoprim-sulfamethoxazole were assayed for synergy against 31 ticarcillin-resistant strains of S. maltophilia by using microtiter checkerboard panels and against 20 strains by using time-kill methodology. The combination of ciprofloxacin with ceftazidime was also evaluated by time-kill studies. Ticarcillin-clavulanate plus trimethoprim-sulfamethoxazole demonstrated synergy by checkerboard panels, with fractional inhibitory concentration indices ranging from 0.033 to 0.49, and by time-kill studies for all 20 strains tested. Synergy between ticarcillin-clavulanate plus ciprofloxacin was found by the checkerboard method for 24 of 31 strains (77%), with fractional inhibitory concentration indices ranging from 0.188 to 0.75. A correlation between synergy by the checkerboard method and the reference time-kill study method was not observed for ticarcillin-clavulanate plus ciprofloxacin, with results for 3 of 10 strains being nonconcordant. Synergy with both ticarcillin-clavulanate plus ciprofloxacin and ceftazidime plus ciprofloxacin by the time-kill method was found to correlate with ciprofloxacin MICs of <32 g/ml and zone diameters of >15 mm on Mueller-Hinton agar. Evaluation of these combinations in vivo may be warranted.Stenotrophomonas (Xanthomonas) maltophilia is an aerobic, gram-negative bacillus which has been isolated from humans, animals, food, pharmaceuticals, and various environmental sources. Because of the low level of pathogenicity and limited invasiveness of S. maltophilia, serious community-acquired infection is infrequent (12, 18). However, significant morbidity and mortality are widely recognized among neutropenic, immunocompromised, and debilitated patients, in whom this organism may become disseminated and result in life-threatening disease (12,18,23,27,37).The antimicrobial resistance of S. maltophilia is attributed to low outer membrane permeability (9,14,15,20,21,39) and the unusual production of multiple chromosomally mediated, broad-spectrum ␤-lactamases, among which are L1 and L2 (1,10,14,15,29,30,32,33). L1 and related ␤-lactamases are group 3 metallopenicillinases and carbapenemases (1,7,15,20,30,33), while L2 and related ␤-lactamases are group 2e cephalosporinases capable of hydrolyzing penicillins and monobactams (1,7,15,20,29,32). All ␤-lactamases are induced synchronously, indicating an apparent overlap of regulatory systems (1,22,30).In vitro susceptibility testing of S. maltophilia is problematic, and results obtained by such tests should be interpreted with caution (1,6,10,13,16,21,38). The National Committee for Clinical Laboratory Standards (NCCLS) (26) currently recommends broth or agar dilu...

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Section: Discussionsupporting

confidence: 87%

In vitro activities of antimicrobial combinations against Stenotrophomonas (Xanthomonas) maltophilia

Poulos

Matsumura

Willey

et al. 1995

Antimicrob Agents Chemother

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Group B Streptococcal Endocarditis: Report of Seven Cases and Review of the Literature, 1962-1985

Gallagher

Watanakunakorn

1986

Clinical Infectious Diseases

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Significance of in-vitro penicillin tolerance in experimental enterococcal endocarditis

Kim

Bayer

1987

J Antimicrob Chemother

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Although penicillin tolerance has been increasingly recognized among clinical isolates of many Gram-positive organisms, the significance of this phenomenon in vivo is not clear. The present study was performed to characterize penicillin-tolerant enterococci by several in-vitro parameters and to examine the significance in vivo in a rabbit model of infective endocarditis. Tolerant enterococci exhibited several characteristics which distinguished them from non-tolerant bacteria: significantly greater ratios of MIC to MBC of penicillin, resistance to penicillin-induced lysis and killing, and growth in areas of superinhibitory concentrations of penicillin upon transfer from penicillin gradient to penicillin-free plates. In-vivo studies of aortic valve endocarditis in rabbits treated with procaine penicillin G (300 mg/kg/day) revealed strikingly different responses between infections due to one tolerant and one non-tolerant strain. Animals infected with a tolerant enterococcus showed consistently greater bacterial counts in vegetations during ten days of therapy and significantly lower rates of vegetation sterilization. Serum penicillin levels were not significantly different between the two groups, but serum bactericidal titres were significantly lower for the tolerant than for the non-tolerant strains. These findings indicate that penicillin tolerance identified by several in-vitro criteria is a significant determinant of the in-vivo response of enterococci to penicillin therapy.

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Experimental Group B Streptococcal Endocarditis Treated with Penicillin G versus Ceftizoxime

Cited by 6 publications

References 19 publications

In vitro activities of antimicrobial combinations against Stenotrophomonas (Xanthomonas) maltophilia

In vitro activities of antimicrobial combinations against Stenotrophomonas (Xanthomonas) maltophilia

Group B Streptococcal Endocarditis: Report of Seven Cases and Review of the Literature, 1962-1985

Significance of in-vitro penicillin tolerance in experimental enterococcal endocarditis

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