Emergence of a novel penicillin-nonsusceptible, invasive serotype 35B clone of Streptococcus pneumoniae within the United States.
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Monitoring antibiotic-resistant pneumococcal strains not covered by the 7-valent conjugate vaccine is an important priority. The Centers for Disease Control and Prevention's Active Bacterial Core Surveillance identified 68 invasive penicillin-nonsusceptible serotype 35B (PN35B) isolates recovered from 1995 to 2001 from patients residing in the states of California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon, Tennessee, and Texas. Nonsusceptible isolates accounted for 69% of all serotype 35B isolates recovered during this time. Twelve (18%) of the 68 PN35B isolates recovered since 1995 were obtained from pediatric patients. These 68 isolates exhibited penicillin MICs of 0.25-2 microg/mL and reduced susceptibility to cefotaxime. Representative PN35B isolates exhibited a common chromosomal macrorestriction profile and identical penicillin-binding-protein gene restriction profiles characteristic of penicillin-resistant strains, and they shared a unique 7-locus sequence type that included 3 new alleles. The mosaic pbp2b and divergent ddl sequences were suggestive of interspecies recombination at the ddl-pbp2b chromosomal region. (+info)
Antibiotic resistance of gram-negative bacteria in rivers, United States.
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Bacteria with intrinsic resistance to antibiotics are found in nature. Such organisms may acquire additional resistance genes from bacteria introduced into soil or water, and the resident bacteria may be the reservoir or source of widespread resistant organisms found in many environments. We isolated antibiotic-resistant bacteria in freshwater samples from 16 U.S. rivers at 22 sites and measured the prevalence of organisms resistant to beta-lactam and non-beta-lactam antibiotics. Over 40% of the bacteria resistant to more than one antibiotic had at least one plasmid. Ampicillin resistance genes, as well as other resistance traits, were identified in 70% of the plasmids. The most common resistant organisms belonged to the following genera: Acinetobacter, Alcaligenes, Citrobacter, Enterobacter, Pseudomonas, and Serratia. (+info)
Cross-reactivity of cefotetan and ceftriaxone antibodies, associated with hemolytic anemia, with other: cephalosporins and penicillin.
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Most drug-induced immune hemolytic anemias since the late 1980s have been caused by the second- and third-generation cephalosporins, cefotetan and ceftriaxone, respectively. Cross-reactivity of cefotetan and ceftriaxone antibodies with other cephalosporins or penicillin has been studied only minimally. We tested 7 serum samples previously identified to contain cefotetan antibodies and one serum sample previously identified to contain ceftriaxone antibodies against 9 other cephalosporins, penicillin, and 7-aminocephalosporanic acid in the presence of RBCs and also used hapten inhibition to indicate cross-reactivity. Serum samples containing cefotetan antibodies showed some cross-reactivity with cephalothin and cefoxitin (and to a much lesser extent with penicillin and ceftazidime). The ceftriaxone antibodies showed very weak cross-reactivity with cefotaxime, cefamandole, and cefoperazone. There was very little cross-reactivity between cefotetan antibodies and the drugs tested in the present study. We have no data to determine whether the in vitro data relate to in vivo reactivity. (+info)
Acyl-intermediate structures of the extended-spectrum class A beta-lactamase, Toho-1, in complex with cefotaxime, cephalothin, and benzylpenicillin.
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Bacterial resistance to beta-lactam antibiotics is a serious problem limiting current clinical therapy. The most common form of resistance is the production of beta-lactamases that inactivate beta-lactam antibiotics. Toho-1 is an extended-spectrum beta-lactamase that has acquired efficient activity not only to penicillins but also to cephalosporins including the expanded-spectrum cephalosporins that were developed to be stable in former beta-lactamases. We present the acyl-intermediate structures of Toho-1 in complex with cefotaxime (expanded-spectrum cephalosporin), cephalothin (non-expanded-spectrum cephalosporin), and benzylpenicillin at 1.8-, 2.0-, and 2.1-A resolutions, respectively. These structures reveal distinct features that can explain the ability of Toho-1 to hydrolyze expanded-spectrum cephalosporins. First, the Omega-loop of Toho-1 is displaced to avoid the steric contacts with the bulky side chain of cefotaxime. Second, the conserved residues Asn(104) and Asp(240) form unique interactions with the bulky side chain of cefotaxime to fix it tightly. Finally, the unique interaction between the conserved Ser(237) and cephalosporins probably helps to bring the beta-lactam carbonyl group to the suitable position in the oxyanion hole, thus increasing the cephalosporinase activity. (+info)
In vitro and in vivo activities of newer fluoroquinolones against Vibrio vulnificus.
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The MICs of six fluoroquinolones as well as minocycline and cefotaxime for 46 clinical isolates of Vibrio vulnificus were determined by the agar dilution method. All the drugs tested had good activities against all isolates, with the MICs at which 90% of the isolates tested were inhibited (MIC(90)s) by five of the fluoroquinolones ranging between 0.03 and 0.06 micro g/ml. The MIC(90) of lomefloxacin, on the other hand, was 0.12 micro g/ml. Time-kill studies were conducted with these agents and a clinical strain of V. vulnificus, VV5823. When approximately 5 x 10(5) CFU of V. vulnificus/ml was incubated with any one of the above-mentioned six fluoroquinolones at concentrations of two times the MIC, there was an inhibitory effect on V. vulnificus that persisted for more than 48 h with no noted regrowth. The efficacies of the fluoroquinolones were further evaluated in vivo in the mouse model of experimental V. vulnificus infection and compared to the efficacy of a combination therapy using cefotaxime plus minocycline. With an inoculum of 1.5 x 10(7) CFU, 28 (87.5%) of 32 mice in the cefotaxime-minocycline-treated group survived and 29 (91%) of the 32 mice in the moxifloxacin-treated group survived while none of the 32 mice in the control group did. With an inoculum of 3.5 x 10(7) CFU, the difference in survival rates among groups of 15 mice treated with levofloxacin (13 of 15), moxifloxacin (10 of 15), gatifloxacin (10 of 15), sparfloxacin (11 of 15), ciprofloxacin (12 of 15), or lomefloxacin (10 of 15) was not statistically significant while none of the 15 mice treated with saline survived. We concluded that the newer fluoroquinolones as single agents are as effective as the cefotaxime-minocycline combination in inhibiting V. vulnificus both in vitro and in vivo. (+info)
Combining computational and experimental screening for rapid optimization of protein properties.
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We present a combined computational and experimental method for the rapid optimization of proteins. Using beta-lactamase as a test case, we redesigned the active site region using our Protein Design Automation technology as a computational screen to search the entire sequence space. By eliminating sequences incompatible with the protein fold, Protein Design Automation rapidly reduced the number of sequences to a size amenable to experimental screening, resulting in a library of approximately equal 200,000 mutants. These were then constructed and experimentally screened to select for variants with improved resistance to the antibiotic cefotaxime. In a single round, we obtained variants exhibiting a 1,280-fold increase in resistance. To our knowledge, all of the mutations were novel, i.e., they have not been identified as beneficial by random mutagenesis or DNA shuffling or seen in any of the naturally occurring TEM beta-lactamases, the most prevalent type of Gram-negative beta-lactamases. This combined approach allows for the rapid improvement of any property that can be screened experimentally and provides a powerful broadly applicable tool for protein engineering. (+info)
Phenytoin pharmacokinetics and clinical effects in African children following fosphenytoin and chloramphenicol coadministration.
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AIMS: Some children with malaria and convulsions also have concurrent bacterial meningitis. Chloramphenicol is used to treat the latter whereas phenytoin is used for convulsions. Since chloramphenicol inhibits the metabolism of phenytoin in vivo, we studied the effects of chloramphenicol on phenytoin pharmacokinetics in children with malaria. METHODS: Multiple intravenous (i.v.) doses of chloramphenicol succinate (CAP) (25 mg kg-1 6 hourly for 72 h) and a single intramuscular (i.m.) seizure prophylactic dose of fosphenytoin (18 mg kg-1 phenytoin sodium equivalents) were concomitantly administered to 15 African children with malaria. Control children (n = 13) with malaria received a similar dose of fosphenytoin and multiple i.v. doses (25 mg kg-1 8 hourly for 72 h) of cefotaxime (CEF). Blood pressure, heart rate, respiratory rate, oxygen saturation, level of consciousness and convulsion episodes were monitored. Cerebrospinal fluid (CSF) and plasma phenytoin concentrations were determined. RESULTS: The area under the plasma unbound phenytoin concentration-time curve (AUC(0, infinity ); means (CAP, CEF): 58.5, 47.6 micro g ml-1 h; 95% CI for difference between means: -35.0, 11.4), the peak unbound phenytoin concentrations (Cmax; medians: 1.12, 1.29 micro g ml-1; 95% CI: -0.5, 0.04), the times to Cmax (tmax; medians: 4.0, 4.0 h; 95% CI: -2.0, 3.7), the CSF:plasma phenytoin ratios (means: 0.21, 0.22; 95% CI: -0.8, 0.10), the fraction of phenytoin unbound (means: 0.06, 0.09; 95% CI: -0.01, 0.07) and the cardiovascular parameters were not significantly different between CAP and CEF groups. However, mean terminal elimination half-life (t1/2,z) was significantly longer (23.7, 15.5 h; 95% CI: 1.71, 14.98) in the CAP group compared with the CEF group. Seventy per cent of the children had no convulsions during the study period. CONCLUSIONS: Concomitant administration of chloramphenicol and a single i.m. dose of fosphenytoin alters the t1/2,z but not the other pharmacokinetic parameters or clinical effects of phenytoin in African children with severe malaria. Moreover, a single i.m. dose of fosphenytoin provides anticonvulsant prophylaxis in the majority of the children over 72 h. However, a larger study would be needed to investigate the effect of concomitant administration of multiple doses of the two drugs in this population of patients. (+info)
Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae isolated in Algiers, Algeria.
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There are few data on antibiotic resistance of Streptococcus pneumoniae in Algeria. Among 309 strains, 34.6% were penicillin G-nonsusceptible S. pneumoniae strains (25.2% were intermediate and 9.4% were resistant). Serotypes 1, 5, 14, and 6 were the most frequent in invasive child infections. A multicenter study to standardize the national guidelines is needed. (+info)