Biomedical subjects

D F Sahm

Publications and source records attributed to D F Sahm.

84 records · Page 5Linked to original sources

PubMed1988

High-content aminoglycoside disks for determining aminoglycoside-penicillin synergy against Enterococcus faecalis.

We investigated the use of high-content aminoglycoside disks for determining Enterococcus faecalis susceptibility to aminoglycoside-penicillin synergy. The susceptibility of the organisms to synergy was established by 24-h time-kill studies performed with streptomycin, kanamycin, amikacin, gentamicin, and tobramycin, alone and in combination with penicillin. A total of 20 isolates that were susceptible to all drug combinations and 20 strains that were resistant to each aminoglycoside-penicillin combination were selected for testing against high-content disks. Disk-agar diffusion was performed on Mueller-Hinton agar, with and without 5% sheep blood, by using disks that contained either 300 or 2,000 micrograms of streptomycin and either 120 or 2,000 micrograms of kanamycin, amikacin, tobramycin, or gentamicin. Zone size results obtained for each aminoglycoside, except amikacin, could be used to differentiate between synergy-susceptible and -resistant isolates. No overlap occurred between the zone sizes of susceptible and resistant strains. Susceptibility to amikacin-penicillin synergy could reliably be tested with kanamycin, but not amikacin, disks. When the disks containing 120 micrograms were tested, a narrow zone size range of 6 to 7 mm could be used to identify all resistant strains. In contrast, when the disks containing 2,000 micrograms were used, the zone size ranges for resistant isolates varied widely with the aminoglycoside being tested. The presence of blood in the medium did not appreciably affect the disk test results. To detect resistance to every aminoglycoside-penicillin combination that may be considered for therapy, E. faecalis isolates need to be tested against a maximum of three different high-content disks (i.e., streptomycin, gentamicin, kanamycin). The disk-agar diffusion test performed with high-content aminoglycoside disks can provide laboratories with a convenient and reliable method for detecting E. faecalis isolates that are resistant to aminoglycoside-penicillin synergy.

Amikacin↗

PubMed1987

Direct susceptibility testing of blood culture isolates with the AutoMicrobic System (AMS).

To decrease the time needed to obtain preliminary antimicrobial susceptibility results with blood culture isolates, we inoculated a suspension of centrifuged organisms from blood culture broth directly into the AutoMicrobic System Gram-Positive (GPS) and Gram-Negative (GSC+) susceptibility cards (AMS, Vitek Systems Inc., Hazelwood, MO). Interpretive category results (susceptible, moderately susceptible, resistant) obtained by this direct method (DAMS) were then compared with results obtained by conventional inoculation (i.e., using 18-hr subcultures) of both AMS cards (CAMS method) and broth microdilution panels (MIC method, Micro-Media Systems Inc., Potomac, MD). Ninety-six Gram-positive cocci (951 antimicrobial agent--organism combinations) and 112 Gram-negative bacilli (1006 antimicrobial agent-organism combinations) were tested. When only very major (false susceptible DAMS results) and major (false resistant DAMS results) discrepancies were considered, 95% of the DAMS results for Gram-positive cocci agreed with CAMS results and 93% agreed with MIC results. Most discrepancies were observed when staphylococci were tested against oxacillin and when enterococci were tested against several antimicrobial agents. For Gram-negative bacilli, 94% of DAMS results agreed with CAMS results and 93% agreed with MIC results. Most discrepancies occurred when Enterobacter spp. and Serratia marcescens were tested against ampicillin and cefamandole. The DAMS method provides accurate and rapid preliminary susceptibility test results, usually within 6 to 7 hr of the time a positive blood culture is first detected.

Anti-Bacterial Agents↗

PubMed1986

Organisms associated with gram-negative folliculitis: in vitro growth in the presence of isotretinoin.

Isotretinoin has been found to be effective in the treatment of Gram-negative folliculitis. We investigated the direct in vitro antibacterial activity of isotretinoin against Gram-negative species. The concentrations of isotretinoin tested were two and ten times greater than the maximal levels attained in the sera of patients receiving oral isotretinoin. Regardless of the inoculum size, each organism tested grew as well in isotretinoin-containing media as it did in the control medium. These findings suggest that the efficacy of isotretinoin in patients with Gram-negative folliculitis is due to mechanisms other than direct antimicrobial action.

Bacterial Infections↗

PubMed1986

Modification of the Sceptor system for rapid detection of methicillin-resistant staphylococci.

The 24-h Sceptor MIC system (Johnston Laboratories, Inc., Towson, Md.) was modified to allow rapid (6 h) detection of methicillin-resistant staphylococci. For 105 methicillin-resistant staphylococci tested, 90% of the results obtained by the 6-h method agreed with those obtained by disk agar diffusion. In comparison, 88 and 93% of the results obtained by the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.) and the 24-h conventional Sceptor system, respectively, agreed with disk agar diffusion results. No false-resistant results were observed with 52 methicillin-susceptible staphylococci tested by any of the three methods.

Humans↗

PubMed1986

Clostridium difficile culture-positive toxin-negative diarrhea.

Antibiotic-associated colitis (AAC) is confirmed by the isolation of Clostridium difficile cytotoxin from stool in patients with diarrhea. Culture of the organism has not been required to confirm the diagnosis. A review of cases of C. difficile culture-positive patients was performed in an attempt to clarify the significance of culture-positive toxin-negative (CPTN) compared to culture-positive toxin-positive (CPTP) disease. During an 11-month period, 45 patients were identified who had stool cultures positive for C. difficile. Sixteen of the patients studied were CPTP and 29 were CPTN. There were no major differences between the two groups for underlying diseases, antibiotic exposure, or diagnostic testing. Of the CPTP patients, 10 were treated for AAC and all responded. Two untreated patients resolved spontaneously. Of the CPTN patients, none was given specific antibiotic therapy, symptoms spontaneously resolved in 17, and symptoms were unresolved in five (colectomy or expired before resolution). A prospective analysis was performed of all C. difficile isolated from stool samples by the microbiology laboratory. Isolates were incubated in vitro and cytotoxin production was measured. Of isolates from CPTP patients 97% produced cytotoxin compared to 67% of isolates from CPTN patients (p less than 0.005). The results suggest that C. difficile, despite the absence of cytotoxin, may be an etiological factor in certain diarrheal syndromes. Until a randomized therapeutic trial for CPTN patients is conclusive, a positive culture should be considered evidence for treatment of patients with persistent diarrhea.

Anti-Bacterial Agents↗

PubMed1984

Influence of growth medium on the in vitro activities of second- and third-generation cephalosporins against Streptococcus faecalis.

The influence of culture medium of the MICs of eight cephalosporins for 45 strains of Streptococcus faecalis was investigated. The MICs of cephalothin, cefamandole, and cefoperazone were not substantially influenced by the type of culture medium used. In contrast, MICs of cefuroxime, ceftizoxime, cefotaxime, cefmenoxime, and ceftriaxone varied markedly with both the commercial brand and the blood content of the broth used. The use of Mueller-Hinton broths (from Oxoid Ltd., GIBCO Diagnostics, and Difco Laboratories) supplemented with 5% lysed sheep blood frequently resulted in MICs that were greater than or equal to 16 times lower than the MICs obtained with these same broths without blood. Similar, but less marked, patterns were observed when supplemented and unsupplemented brain heart infusion and Sceptor broths were used. The influence of the broth on MICs suggests a complex interaction between some cephalosporins, medium components, and organisms. The cephalosporins that were affected by media share an identical moiety at the 7-acyl position (cefuroxime is slightly different), but this structure is not shared by those cephalosporins that were not affected. This commonality in structure at the 7-acyl position may be partially responsible for the observed results.

Animals↗

PubMed1984

Effect of media and blood on the antimicrobial activity of cephalosporins on serogroup D streptococci: a review.

The influence of culture medium on in vitro of selected cephalosporins on on group D streptococci was investigated by agar diffusion and broth dilution methods. The activity of cephalothin, cefamandole, and cefoperazone were not substantially influenced by the type of culture medium used, but cefuroxime, ceftizoxime, cefotaxime (CTX), cefmenoxime, and ceftriaxone varied markedly with both the commercial brand and the blood content of the broth used. The differences were more likely to occur in some Mueller-Hinton media, particularly when supplemented with 5% lysed sheep blood, and resulted in susceptible results instead of the resistant results that were obtained with these same media without blood. Some strains of Streptococcus faecalis showed these discrepancies, but S. bovis did not. The influence of the media on in vitro activity suggests a complex interaction between some cephalosporins, media components, and organisms. The cephalosporins that were affected by media share an identical moiety at the 7-acyl position (cefuroxime is slightly different); this structure is not shared by those cephalosporins that were not affected, however. It is possible that this structure may play a part in the phenomenon.

Animals↗

PubMed1983

Gamma-glutamyltranspeptidase levels as an aid in the management of human cancer.

Plasma gamma-glutamyltranspeptidase (GGTP) levels were measured in 435 cancer patients, 120 healthy controls, 15 patients with systemic lupus erythematosis, and 10 patients with rheumatoid arthritis. The mean GGTP activity of all cancer patients studied, with the exception of malignant lymphoma, was significantly elevated compared to control values. Several patient groups were retrospectively analyzed to determine whether GGTP levels correlated with clinical status. Patients who were disease-free had GGTP levels in the normal range, whereas patients with metastases had elevated levels. Serially increasing GGTP levels were associated with disease progression and death. Persons who remained free of disease had serial GGTP levels within the normal range. Furthermore, decreasing levels were associated with response to therapy. These results indicate that GGTP levels may have prognostic value in various human malignancies.

Arthritis, Rheumatoid↗

PubMed1983

Medium-dependent zone size discrepancies associated with susceptibility testing of group D streptococci against various cephalosporins.

Mueller-Hinton (MH) agar media from various commercial sources, either supplemented or not supplemented with 5% sheep blood, were studied to determine their effect on disk diffusion susceptibility testing results obtained with 90 strains of group D streptococci and four cephalosporins. The cephalosporins investigated included cephalothin, cefamandole, moxalactam, and cefotaxime. Results showed that a number of Streptococcus faecalis and Streptococcus faecium strains were susceptible to cephalothin, cefamandole, and cefotaxime, but the number varied with both the commercial source and blood content of the MH medium used. Regardless of the MH medium used, none of the S. faecalis or S. faecium strains were found to be susceptible to moxalactam. The apparently medium-associated variations in the number of strains susceptible to cephalothin, cefamandole, and cefotaxime were largely due to minor discrepancies (one result being intermediate) among the various types of MH media used. However, major discrepancies (one result being resistant and the other susceptible or vice versa) were observed when S. faecalis strains were tested against cefotaxime. These major discrepancies were associated with both the commercial source of the MH medium and the blood content of the medium.

Cephalosporins↗

PubMedDate not supplied

In vitro activity of grepafloxacin and 25 other antimicrobial agents against Streptococcus pneumoniae: correlation with penicillin resistance.

Strains of Streptococcus pneumoniae from the United States that were susceptible, intermediately resistant, or highly resistant to penicillin were tested for susceptibility to 26 antimicrobial agents that have been used or considered for the treatment of patients with pneumococcal infections. The drugs tested included penicillins, one penicillin/beta-lactamase inhibitor combination, cephalosporins, macrolides, a lincosamide, fluoroquinolones, and four miscellaneous drugs (vancomycin, rifampin, tetracycline, and trimethoprim-sulfamethoxazole). The activities of the penicillins and macrolide agents were similar, but the activities within the cephalosporin and fluoroquinolone classes were often dissimilar. For the fluoroquinolones, the order of in vitro activity, from most to least active, was grepafloxacin, sparfloxacin, levofloxacin, ciprofloxacin, and ofloxacin. Increased resistance to penicillin in the pneumococcal isolates studied correlated with increased resistance to other penicillins, cephalosporins, macrolides, clindamycin, tetracycline, and trimethoprim-sulfamethoxazole but did not correlate with increased resistance to the fluoroquinolones, rifampin, or vancomycin. These findings may be helpful to health professionals selecting empiric therapy for respiratory tract infections involving S. pneumoniae.

Anti-Infective Agents↗

PubMedDate not supplied

Comparative activity of cefditoren and other oral beta-lactams against nonpneumococcal streptococci.

BACKGROUND: In vitro studies of cefditoren activity have focused primarily on Streptococcus pneumoniae and other bacterial species isolated from patients with respiratory infections, but relatively few reports have been published describing the activity of cefditoren against clinical isolates of nonpneumococcal streptococci. METHODS: Cefditoren activity was determined by broth microdilution (M7-A5, NCCLS, 2000) for 450 viridans group streptococci, 917 Streptococcus pyogenes and 800 other beta-hemolytic streptococci collected throughout the US during 1999-2000. RESULTS: Against viridans group streptococci, cefditoren (MIC(90), 0.5 microg/ml) was 4- to 32-fold more active than the other beta-lactams tested (penicillin ampicillin, amoxicillin-clavulanate, cefprozil and cefuroxime). The difference in activity between cefditoren and the other beta-lactams was greater for penicillin-nonsusceptible isolates (MIC(90s), 1 microg/ml versus 8-32 microg/ml) than among penicillin-susceptible isolates (MIC(90s), 0.12 versus 0.25- 1 microg/ml). Cefditoren also demonstrated potent activity against S. pyogenes (MIC(90), 0.015 microg/ml) and other beta-hemolytic streptococci (MIC(90), 0.06 microg/ml), comparable to that of the other beta-lactams. CONCLUSIONS: The activity demonstrated by cefditoren against nonpneumococcal streptococci, including beta-lactam- and macrolide-resistant isolates, suggests that this agent holds promise as therapy for infections caused by all clinically significant species of streptococci.

Administration, Oral↗

PubMedDate not supplied

Multiple-drug resistant enterococci: the nature of the problem and an agenda for the future.

Enterococci, leading causes of nosocomial bacteremia, surgical wound infection, and urinary tract infection, are becoming resistant to many and sometimes all standard therapies. New rapid surveillance methods are highlighting the importance of examining enterococcal isolates at the species level. Most enterococcal infections are caused by Enterococcus faecalis, which are more likely to express traits related to overt virulence but--for the moment--also more likely to retain sensitivity to at least one effective antibiotic. The remaining infections are mostly caused by E. faecium, a species virtually devoid of known overt pathogenic traits but more likely to be resistant to even antibiotics of last resort. Effective control of multiple-drug resistant enterococci will require 1) better understanding of the interaction between enterococci, the hospital environment, and humans, 2) prudent antibiotic use, 3) better contact isolation in hospitals and other patient care environments, and 4) improved surveillance. Equally important is renewed vigor in the search for additional drugs, accompanied by the evolution of new therapeutic paradigms less vulnerable to the cycle of drug introduction and drug resistance.

Anti-Bacterial Agents↗