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D F Sahm

Publications and source records attributed to D F Sahm.

At least 37 records · Page 2Linked to original sources
PubMed2001

Multidrug-resistant urinary tract isolates of Escherichia coli: prevalence and patient demographics in the United States in 2000.

Concurrent resistance to antimicrobials of different structural classes has arisen in a multitude of bacterial species and may complicate the therapeutic management of infections, including those of the urinary tract. To assess the current breadth of multidrug resistance among urinary isolates of Escherichia coli, the most prevalent pathogen contributing to these infections, all pertinent results in The Surveillance Network Database-USA from 1 January to 30 September 2000 were analyzed. Results were available for 38,835 urinary isolates of E. coli that had been tested against ampicillin, cephalothin, ciprofloxacin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Of these isolates, 7.1% (2,763 of 38,835) were resistant to three or more agents and considered multidrug resistant. Among the multidrug-resistant isolates, 97.8% were resistant to ampicillin, 92.8% were resistant to trimethoprim-sulfamethoxazole, 86.6% were resistant to cephalothin, 38.8% were resistant to ciprofloxacin, and 7.7% were resistant to nitrofurantoin. The predominant phenotype among multidrug-resistant isolates (57.9%; 1,600 of 2,793) included resistance to ampicillin, cephalothin, and trimethoprim-sulfamethoxazole. This was the most common phenotype regardless of patient age, gender, or inpatient-outpatient status and in eight of the nine U.S. Bureau of the Census regions. Rates of multidrug resistance were demonstrated to be higher among males (10.4%) than females (6.6%), among patients > 65 years of age (8.7%) than patients < or = 17 (6.8%) and 18 to 65 (6.1%) years of age, and among inpatients (7.6%) than outpatients (6.9%). Regionally, the rates ranged from 4.3% in the West North Central region to 9.2% in the West South Central region. Given the current prevalence of multidrug resistance among urinary tract isolates of E. coli in the United States (7.1%), continued local, regional, and national surveillance is warranted.

Adolescent↗
PubMed2000

Benchmarking the in vitro activity of moxifloxacin against recent isolates of Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae. A European multi-centre study.

To benchmark the activity of moxifloxacin, a European study comprising 900 Streptococcus pneumoniae, 1051 Haemophilus influenzae, and 226 Moraxella catarrhalis referred from 30 institutions during 1998 is described. For S. pneumoniae, moxifloxacin and trovafloxacin MIC(90) and modal MICs values were 0.12 microg/ml and independent of susceptibility to other drug classes, geography, or site of infection. MIC(90)/modal MICs were, respectively, 0.25/0.12 microg/ml for grepafloxacin, 0.25/0.25 microg/ml for sparfloxacin, and 1.0/0.5 microg/ml for levofloxacin. The moxifloxacin C(max):MIC ratio of 20.8-26.3 is higher than comparator fluoroquinolones. Five isolates were intermediate or resistant to grepafloxacin, sparfloxacin, or levofloxacin of which four and three remained susceptible to trovafloxacin and moxifloxacin, respectively. For moxifloxacin, > 90% of S. pneumoniae isolates demonstrated MICs > or =3 dilutions below the susceptibility breakpoint used. Modal MICs and MIC(90) for M. catarrhalis (both 0.03 microg/ml) and H. influenzae (0.03 microg/ml and 0.06 microg/ml) were independent of beta-lactamase production. These data demonstrate the in vitro activity of moxifloxacin and establish a baseline for future surveillance studies that will be important for detecting and tracking any trends in changing activity of this fluoroquinolone.

Anti-Infective Agents↗
PubMed2000

Antimicrobial susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected from five centers in Brazil, 1997-98.

OBJECTIVE: To assess the susceptibility of the key respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis to antimicrobial agents used to treat respiratory tract infections. METHODS: Isolates were collected from five centers in Brazil during 1997-98, and susceptibility testing was conducted at a central laboratory according to National Committee for Clinical Laboratory Standards criteria. RESULTS: Of the 359Streptococcus pneumoniae isolates tested, 77% were susceptible, 19% were intermediate and 4% were resistant to penicillin. The susceptibility of S. pneumoniae to other beta-lactams and macrolides was greater than 90%, but cotrimoxazole was active against only 48% of the isolates. The prevalence of susceptible isolates was 100.0% for vancomycin and 99.7% for levofloxacin. beta-Lactam, macrolide, and cotrimoxazole activities were negatively associated with penicillin resistance. Of the 219 isolates of Haemophilus influenzae tested, 11% produced beta-lactamase and 11% were not susceptible to ampicillin. Nearly all H. influenzae isolates were susceptible to all other drugs, except cotrimoxazole (47% susceptibility). Of the 52 Moraxella catarrhalis isolates, 98% produced beta-lactamase, and the MIC of all drugs was </=4 mg/L, with the exception of ampicillin, where the MIC90 was> 8 mg/L. CONCLUSIONS: When these data are compared with previous reports, our findings suggest that the prevalence of pneumococci that are resistant to agents such as penicillin and cotrimoxazole may be increasing in Brazil, which highlights the need to continue surveillance programs.

Anti-Bacterial Agents↗
PubMed2000

Resistance in respiratory tract pathogens: an international study 1997-1998.

Multiple antibiotic resistance threatens current treatment for community-acquired pneumonia (CAP). This paper presents a summary of resistance data for Streptococcus pneumoniae (6,223 isolates), Haemophilus influenzae (4,016) and Moraxella catarrhalis (1,263) collected from 153 centers throughout Japan, China, UK, Germany, Spain, France, Italy, Brazil and USA. Antiobiotics tested were: beta-lactams (penicillin, ampicillin, co-amoxiclav, cefuroxime, and ceftriaxone), macrolides (azithromycin and clarithromycin), sulphonamide (trimethoprim-sulfamethoxazole), glycopeptide (vancomycin) and fluoroquinolone (levofloxacin). S. pneumoniae with reduced susceptibility to penicillin were predominant in France, Spain and Japan (54-65%), ,beta-lactamase-producing H. influenzae most common in the USA, France and Spain (>25%) and most M. catarrhalis produced beta-lactamase irrespective of origin. S. pneumoniae susceptibility to azithromycin and clarithromycin varied widely. Levofloxacin was active against almost all isolates in all countries and none was resistant to vancomycin. Because of increasing resistance to older drugs, the newer fluoroquinolones have a role in the therapy of CAP and other respiratory infections, although surveillance studies must continue.

Bacterial Proteins↗
PubMed2000

Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolated in Asia and Europe, 1997-1998.

A multicentre, collaborative study was performed in Asia and Europe during the winter of 1997-1998 to determine the in vitro activity of selected antimicrobial agents against common respiratory pathogens. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolates were collected from 48 sites in China, France, Germany, Italy, Japan, Spain and the UK and tested in a central laboratory in the USA. Broth microdilution MICs were determined for beta-lactams (penicillin, amoxycillin/clavulanate, cefuroxime, ceftriaxone), macrolides (azithromycin, clarithromycin), sulphonamides (co-trimoxazole), glycopeptides (vancomycin) and fluoroquinolones (levofloxacin). The percentage of isolates susceptible to each antimicrobial class varied substantially by country. Penicillin susceptibility amongst pneumococci ranged from 34% in France and Spain to 92% in Germany, and macrolide susceptibility varied between 26% in China and 91% in the UK. In most countries beta-lactam, macrolide and cotrimoxazole resistance was more prevalent amongst penicillin-intermediate and -resistant S. pneumoniae isolates. However, little or no resistance was detected to levofloxacin (0.3% intermediate and resistant) or vancomycin (0% intermediate and resistant). For H. influenzae the prevalence of beta-lactamase production varied from 6% in China and Germany to 32% in Spain, and for M. catarrhalis, from 79% in Germany to 98% in Japan. With the exception of ampicillin, beta-lactamase production had a minimal effect on beta-lactam activity against H. influenzae or M. catarrhalis. Our findings demonstrate that antimicrobial resistance profiles of common respiratory isolates differ dramatically between countries in Asia and Europe.

Asia↗
PubMed2000

Benchmarking the in vitro activities of moxifloxacin and comparator agents against recent respiratory isolates from 377 medical centers throughout the United States.

To benchmark the activity of moxifloxacin (a newer fluoroquinolone), a U.S. study comprising 16,141 contemporary isolates of Streptococcus pneumoniae (5,640), Haemophilus influenzae (6,583), and Moraxella catarrhalis (3,648) referred from 377 institutions during 1998 is described. For S. pneumoniae the modal MIC and MIC at which 90% of the isolates were inhibited (MIC(90)) for moxifloxacin were 0.12 and 0.25 microg/ml, respectively, independent of susceptibility to other drug classes, geography, or site of infection. Eleven isolates were intermediate or resistant to levofloxacin and grepafloxacin; of these isolates, 1 remained susceptible to sparfloxacin, 2 remained susceptible to moxifloxacin, and 4 remained susceptible to trovafloxacin. All 11 isolates possessed classic mutations in gyrA and/or parC known to confer reduced susceptibility to fluoroquinolones. Four isolates (originating from four separate states) belonging to a multidrug-resistant, fluoroquinolone-resistant clone were identified by pulsed-field gel electrophoresis. For moxifloxacin and trovafloxacin, at least 87% of isolates demonstrated MICs > or =3 twofold concentrations below the susceptibility breakpoints, in contrast to no more than 15% for levofloxacin, grepafloxacin, and sparfloxacin. Of the isolates that were multidrug resistant (7.4%), >98% remained susceptible to moxifloxacin. The modal MIC and MIC(90) for M. catarrhalis (both 0.06 microg/ml) and for H. influenzae (both 0.03 microg/ml) were independent of beta-lactamase production. These data demonstrate the in vitro activity of moxifloxacin and establish a baseline for future studies.

Anti-Infective Agents↗
PubMed2000

Prevalence of gyrA, gyrB, parC, and parE mutations in clinical isolates of Streptococcus pneumoniae with decreased susceptibilities to different fluoroquinolones and originating from Worldwide Surveillance Studies during the 1997-1998 respiratory season.

From 8,419 worldwide clinical isolates of Streptococcus pneumoniae obtained during 1997-1998, 69 isolates with reduced susceptibility or resistance to fluoroquinolones (FQs) were molecularly characterized. For the isolates in this prevalence study, only parC (Ser-79-->Tyr) and gyrA (Ser-81-->Phe or Tyr) mutations, especially in combination, were found to contribute significantly to resistance. These mutations influenced the FQ MICs to varying degrees, although the rank order of activity remains independent of mutation type, with ciprofloxacin the least active, followed by levofloxacin, gatifloxacin/grepafloxacin/moxifloxacin/sparfloxaci n/trovafloxacin, and clinafloxacin/sitafloxacin. Efflux likely plays a crucial role in reduced susceptibility for new hydrophilic FQs.

Anti-Infective Agents↗
PubMed2000

Analysis of ciprofloxacin activity against Streptococcus pneumoniae after 10 years of use in the United States.

As the most commonly used fluoroquinolone in the United States since 1987, ciprofloxacin has exerted the greatest selective pressure on S. pneumoniae and provides a valuable marker to evaluate the actual and potential emergence of fluoroquinolone resistance in this species. Analysis of susceptibility results obtained with 5,640 strains collected from throughout the United States showed that only 16 (0.3%) of the isolates demonstrated MICs of > or =4 microg/ml. The prevalence of this phenotype was significantly higher (P < 0.05) among penicillin-resistant populations, among isolates from patients >64 years old, and among respiratory isolates. However, >99% of strains had MICs of <4 microg/ml regardless of the risk group examined, and the MIC population distributions were the same for each risk group. These findings demonstrate that the phenotype of a MIC of > or =4 microg/ml remains uncommon after 10 years of ciprofloxacin use; however, these findings are no reason to become complacent with regard to appropriate use of fluoroquinolones and the need to carefully track resistance trends. Equally important is careful analysis of data that result from surveillance in terms of risk factors and other associated trends so that resistance and susceptibility, and their consequences, are neither over- nor underestimated.

Adolescent↗
PubMed2000

Relationships between enterococcal virulence and antimicrobial resistance.

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Anti-Bacterial Agents↗
PubMed2000

Rapid automated antimicrobial susceptibility testing of Streptococcus pneumoniae by use of the bioMerieux VITEK 2.

The VITEK 2 is a new automated instrument for rapid organism identification and susceptibility testing. It has the capability of performing rapid susceptibility testing of Streptococcus pneumoniae with specially configured cards that contain enriched growth medium and antimicrobial agents relevant for this organism. The present study compared the results of testing of a group of 53 challenge strains of pneumococci with known resistance properties and a collection of clinical isolates examined in two study phases with a total of 402 and 416 isolates, respectively, with a prototype of the VITEK 2. Testing was conducted in three geographically separate laboratories; the challenge collection was tested by all three laboratories, and the unique clinical isolates were tested separately by the individual laboratories. The VITEK 2 results of tests with 10 antimicrobial agents were compared to the results generated by the National Committee for Clinical Laboratory Standards reference broth microdilution MIC test method. Excellent interlaboratory agreement was observed with the challenge strains. The overall agreement within a single twofold dilution of MICs defined by the VITEK 2 and reference method with the clinical isolates was 96.3%, although there were a number of off-scale MICs that could not be compared. The best agreement with the clinical isolates was achieved with ofloxacin and chloramphenicol (100%), and the lowest level of agreement among those drugs with sufficient on-scale MICs occurred with trimethoprim-sulfamethoxazole (89.7%). Overall there were 1.3% very major, 6.6% minor, and no major interpretive category errors encountered with the clinical isolates, although >80% of the minor interpretive errors involved only a single log(2) dilution difference. The mean time for generation of susceptibility results with the clinical isolates was 8.1 h. The VITEK 2 provided rapid, reliable susceptibility category determinations with both the challenge and clinical isolates examined in this study.

Anti-Bacterial Agents↗
PubMed2000

Antimicrobial resistance in respiratory tract pathogens: results of an international surveillance study.

An international surveillance study was performed to assess the resistance patterns among respiratory tract pathogens during the winter of 1997-1998. The pathogens studied included Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. The antibiotics tested included five beta-lactams (penicillin, ampicillin, amoxicillin, amoxicillin-clavulanic acid, cefuroxime axetil and ceftriaxone), two macrolides (azithromycin and clarithromycin), one sulfonamide (trimethoprim-sulfamethoxazole), one glycopeptide (vancomycin) and one fluoroquinolone (levofloxacin). A total of 11,502 isolates were tested from nine countries, using microdilution susceptibility tests as recommended by National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The susceptibility rates varied greatly around the world. Ninety percent of M. catarrhalis isolates produced beta-lactamase, making them resistant to ampicillin. beta-Lactamase production by H. influenzae ranged from 5% in Germany to 34% in the USA (mean 17.5%). Of the S. pneumoniae isolates, 32.8% had some resistance to penicillin, but this ranged greatly from 7.8% in Germany to 66.5% in France. Penicillin resistance in S. pneumoniae was associated with resistance to other beta-lactams, macrolides and sulfonamides, but not to levofloxacin or vancomycin. All isolates of H. influenzae and M. catarrhalis were susceptible to levofloxacin. Results of this study support the conclusion that these three respiratory tract pathogens are becoming more resistant to selected antimicrobials, and that the level of resistance in these isolates to the antimicrobials varies greatly from one country to another.

Drug Resistance, Microbial↗
PubMed1999

Antimicrobial resistance in key bloodstream bacterial isolates: electronic surveillance with the Surveillance Network Database--USA.

To assess the prevalence of antimicrobial-resistant pathogens among the most common bloodstream isolates, we examined antimicrobial susceptibility data from The Surveillance Network Database-USA, an electronic surveillance system that collects data from 118 clinical microbiology laboratories across the United States. Between 1995 and 1997, resistance to both vancomycin and ampicillin was much more prevalent among Enterococcus faecium than Enterococcus faecalis, suggesting the need for laboratories to identify to species. When staphylococcal isolates were examined for reduced susceptibility to vancomycin (minimum inhibitory concentration = 4 microg/mL), the frequency was highest in methicillin-resistant coagulase-negative staphylococci. We also learned that nonsusceptibility to ceftazidime in Klebsiella pneumoniae was more prevalent among isolates from blood (12.7%) than among isolates from urine (7.1%) or respiratory sources (9.3%). Although antimicrobial resistance is low overall for isolates of Escherichia coli from blood, the prevalence of cefoxitin resistance among ceftazidime-resistant strains (61.9%) suggests the action of mechanisms other than extended-spectrum beta-lactamase.

Anti-Bacterial Agents↗
PubMed1999

Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolated in the United States, 1997-1998.

A national antimicrobial resistance surveillance study was conducted from December 1997 to May 1998 to determine the prevalence of antimicrobial resistance in 6620 clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. In this centralized study, which involved 163 institutions located in 43 states, we determined MICs for representatives of five antimicrobial classes: beta-lactams (penicillin, co-amoxiclav, cefuroxime, ceftriaxone), macrolides (azithromycin, clarithromycin), co-trimoxazole, glycopeptides (vancomycin) and fluoroquinolones (levofloxacin). In most S. pneumoniae isolates, all antimicrobials were to be found active, but amongst penicillin-resistant isolates (MICs > or = 2 mg/L), resistance to other beta-lactams, macrolides and co-trimoxazole was common. For vancomycin and levofloxacin, however, activity was not associated with penicillin resistance. The prevalence of penicillin-nonsusceptible (intermediate and resistant) pneumococci was highest in the South Atlantic (44%) and East South Central (43%) regions and lowest in the Mid-Atlantic (28%) and New England (28%) regions. Resistance to beta-lactams, macrolides and co-trimoxazole was more commonly found amongst respiratory isolates than blood isolates and in strains from patients < or = 12 years old than from older patients. beta-lactamase, which was detected in 33% of H. influenzae and 92% of M. catarrhalis strains, did not affect the activity of the beta-lactams under study other than ampicillin. Certain agents, such as vancomycin and the fluoroquinolones, remain highly active, and well-designed surveillance systems that monitor MIC distributions would be needed to detect a potential for reduced susceptibility. In addition, surveillance programmes should be designed to collect information about associated resistance as well as differences in prevalence associated with region, specimen source and patient age.

Adolescent↗
PubMed1999

Survey of susceptibilities of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolates to 26 antimicrobial agents: a prospective U.S. study.

An antimicrobial susceptibility surveillance study of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolates was performed during the winter of 1996-1997 in order to determine their susceptibilities to 5 fluoroquinolones and 21 other antimicrobial agents. Broth microdilution MICs were determined for 2, 752 isolates from 51 U.S. medical centers. Of the 1,276 S. pneumoniae isolates, 64% were susceptible, 17% were intermediate, and 19% were highly resistant to penicillin. On the basis of the MICs at which 90% of isolates are inhibited and modal MICs, the hierarchy of the five fluoroquinolones from most to least active was grepafloxacin > sparfloxacin > levofloxacin = ciprofloxacin > ofloxacin. For S. pneumoniae isolates for which penicillin MICs were elevated, the MICs of the cephalosporins, macrolides, clindamycin, tetracycline, and trimethoprim-sulfamethoxazole were also elevated, but the MICs of the fluoroquinolones, vancomycin, and rifampin were not. The prevalence of penicillin-susceptible pneumococci varied by U.S. Bureau of the Census region (range, 44% in the East South Central region to 75% in the Pacific region). In addition, S. pneumoniae isolates from blood were significantly more susceptible to penicillin than those from respiratory, ear, or eye specimens, and pneumococci from patients </=2 years old were significantly more resistant to penicillin than those from older patients (by chi-square analysis, P < 0.05). beta-Lactamase was produced by 35% of H. influenzae isolates and 93% of M. catarrhalis isolates, resulting in increased MICs of amoxicillin and certain cephalosporins. We noted that the antimicrobial resistance patterns of S. pneumoniae isolates, which correlate with the penicillin susceptibility phenotype, vary by site of infection, age group of the patient, and geographic source of the isolate.

Adolescent↗