Activity of cephalosporins against methicillin-susceptible and methicillin-resistant, coagulase-negative staphylococci: minimal effect of beta-lactamase

John, Jr Jf; McNeill, WF

doi:10.1128/aac.17.2.179

Cited by 41 publications

(12 citation statements)

References 10 publications

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“…Subpopulations of cells resistant to nafcillin and cephalothin have been found in every methicillin-resistant isolate but have not always been detectable by susceptibility testing (2). Although some authors have contended that such strains may be cephalothin susceptible based on MIC or inhibitory zone diameter criteria (7,15,28,48,52), our conclusion that PRP-resistant strains of S. epidermidis are also resistant to cephalothin has been supported by other studies which defined resistance based on the heteroresistant phenotype (2,21,23,36) as well as the clinical observation that patients with PRP-resistant S. epidermidis bacteremia did not respond well to treatment with cephalosporins (23,52). There were several possible exceptions to the generalization that PRP-resistant staphylococci are also cephalothin resistant, but these were atypical strains.…”

Section: Discussionsupporting

confidence: 72%

“…The results of oxacillin susceptibility testing should also apply to all the cephalosporins because staphylococci may also be heteroresistant to these drugs (2,3,21,23,32). If the heteroresistant phenotype defines resistance, susceptibility criteria cannot be based on MIC breakpoints selected by pharmacokinetic considerations or by inhibitory zone diameters determined by regression analysis.…”

Section: Discussionmentioning

confidence: 99%

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In vitro susceptibilities of four species of coagulase-negative staphylococci

Fass¹,

Helsel²,

Barnishan³

et al. 1986

Antimicrob Agents Chemother

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

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Section: Discussionsupporting

confidence: 72%

Section: Discussionmentioning

confidence: 99%

In vitro susceptibilities of four species of coagulase-negative staphylococci

Fass¹,

Helsel²,

Barnishan³

et al. 1986

Antimicrob Agents Chemother

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“…Different biotypes and epidemiological differences of the strains studied could explain the different results reported in the literature (3,5,11). Archer and Tenenbaum (3) report cefamandole resistance among MR S. epidermidis, but these strains could represent a selected population, being isolated from patients who received antibiotic prophylaxis.…”

mentioning

confidence: 51%

“…Our results suggest that the current concept that cephalothin is the cephalosporin with the highest activity against staphylococcal strains (2,5,16) …”

mentioning

confidence: 75%

Cross-resistance between methicillin and cephalosporins for staphylococci: a general assumption not true for cefamandole

Frongillo¹,

Bianchi²,

Moretti³

et al. 1984

Antimicrob Agents Chemother

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The antibacterial activity of cefamandole was evaluated against 120 methicillin-susceptible and methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococcal strains, using both large (108 CFU per ml) and small (104 CFU per ml) inocula. Cefamandole appeared superior to cephalothin against tnethicillin-resistant strains, displaying at 10 ,ug/ml a bacteriostatic and for some strains a bactericidal action against a large inoculum of bacteria.The cross-resistance reported between methicillin and cephalosporins for both coagulase-positive and coagulasenegative staphylococcal strains (1, 6, 10, 13, 15) represents a major therapeutic problem, as it precludes the use of cephalosporins in patients affected with methicillin-resistant (MR) strains. Hospital outbreaks of infection caused by multiplyresistant staphylococcus strains, even in countries where they have never been isolated previously (4,7,12,18), have renewed interest in this problem. Among the newer cephalosporins with a broadened spectrum of activity against gramnegative bacteria, only a few (e.g., cefamandole and cefazolin) maintain good antistaphylococcal activity comparable to that of cephalothin (2, 9, 11). We undertook to evaluate whether the generally observed cross-resistance between methicillin and cephalosporins is-valid for the second-generatlon cephalosporin cefamandole. For this purpose the bacteriostatic and bactericidal activities of cefamandole and cephalothin against methicillin-susceptible (MS) and MR staphylococci were studied.Sixty-six Staphylococcus aureus (36 MS and 30 MR) and 54 coagulase-negative staphylococci (18 MS and 36 MR) strains isolated from clinical specimens at the microbiology laboratory, Perugia University Medical School, Italy, were tested. Most of the isolates were fromn patients who had not received antibiotic prophylaxis or therapy.The Staphylococcus species were identified on the basis of conventional tests (8) visible growth after 24 h of incubation at 37°C, and then 0.1 ml was subcultured from wells containing the lower inoculum, and 0.001 ml was subcultured from wells containing the higher inoculum. After 48 h of incubation at 37°C, 99.9%killing was determined as the lowest antibiotic concentration yielding no growth on subculture of the wells containing the lower inoculum and 100 colonies or less from wells containing the higher inoculum.The results are reported in Table 1. Nearly all the MS strains were inhibited by the two antibiotics, which both lacked bactericidal activity at the large inoculum. The median MICs were two to three times higher for cefamandole, whereas the reverse was noted for the MBCs for S. aureus. For MR strains at the smiall inoculum, the median MICs were all in the therapeutic range, but 100% strains were susceptible to 10 ,ug of cefamandole per ml, whereas 13.3% S. aureus and 22.3% coagulase-negative staphylococci were resistant to 10 ,ug of cephalothin per ml.At the large inoculum, the median MICs of cephalothin were out of the therapeutic range (58.3 ,ug/ml for S. a...

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“…Much more data are available for S. aureus than for the other species of staphylococci (Barry and Badal, 1977;McDougal and Thornsberry, 1984;Sabath, 1977;Thornsberry et al, 1973;Thornsberry and McDougal, 1983). Staphylococcus aureus, which are clearly resistant to nafcillin (or oxacillin or methicillin), also show resistance to cephalosporins by in vitro bactericidal assays and in the clinical setting; it is, however, not clear from published data that the same statements can be made for the coagulase-negative staphylococci (Ein et al, 1979;Frongillo et al, 1984;Hansen, 1983;John and McNeill, 1980;Laverdiere et al, 1978).…”

Section: Discussionmentioning

confidence: 99%