<p>We present an enzyme engineering approach based solely on amino-acids sequence to convert glycoside hydrolases into transglycosylases. We demonstrate its effectiveness on enzymes form five different glycoside hydrolase families, synthesizing various oligosaccharides containing different α-/β-pyranosides or furanosides in one-step with high yields.</p>
Despite penicillin (pcV) treatment, tonsillopharyngitis caused by group A streptococci (GAS) is associated with bacterial failure rates as high as 25%. The reason for this rate of failure is not fully understood. One explanation might be that certain DNA profiles of GAS strains are responsible for treatment failures. Using arbitrarily primed polymerase chain reaction (AP-PCR), we compared the DNA profiles of GAS strains from 4 patients with several treatment failures following pcV treatment of tonsillopharyngitis with the profiles of strains of the same T type from patients who were clinically and bacteriologically cured after a single course of pcV. The isolates were obtained during the same time period and from the same geographic area. Thirty-seven strains of T types 4, 12, and R28 were investigated. Eleven different DNA profiles could be detected with the AP-PCR technique. Five DNA profiles were identified as T type 12, 3 as T type 4, and 3 as T type R28. The DNA profiles of the strains from the 4 patients with several treatment failures differed, but all isolates from each one of these patients exhibited the same or a very similar profile. The DNA profiles of the failure strains were also represented in nonfailure strains. Treatment failure in these 4 patients therefore seems to be due to insufficient eradication of GAS, rather than to reinfection with a new strain. The finding that the same DNA profile can be present in both failure and nonfailure strains suggests that the treatment failure may be to some extent host-related and not only due to bacterial factors.
Blood culture isolates (n = 880) collected during 2.5 years (period I n = 515, July 1988 to December 1989; period II n = 365, January 1992 to December 1992) were analysed with the agar dilution method to ascertain their sensitivity to 24 antibiotics. The susceptibility of bacteria was classified according to MIC values and susceptibility grouping used in the SIR system (sensitive-S, intermediate-I, resistant-R). Comparison of percentage S+I values for the 2 periods revealed no major development of resistance. Co-trimoxazole and some cephalosporins (cefpirom, cefepime and cefotaxime) were active (S+I) against 88-92% of the strains. Imipenem and the combination piperacillin-tazobaclam were active against 95% of the strains. A very large number of strains (98.2 to 98.6%) were inhibited (S+I) by the quinolones tested, ciprofloxacin and ofloxacin. Comparison of the present results with those of our 1980-81 study yielded no evidence of resistance development, except for an increase in betalactamase-producing S. aureus strains, from 67% to 85%.
With the elimination of Haemophilus influenzae type b through vaccination, it has been suggested that other types of H. influenzae strains might acquire virulence traits and emerge as important pathogens. The gene sequence IS1016 has been associated with an increased capacity to cause severe infections. It is usually present in encapsulated strains but is sometimes harbored by nontypeable H. influenzae strains. To explore this further, 118 H. influenzae isolates, collected from both patients and healthy carriers, were investigated with PCR with reference to this gene sequence. Isolates positive for the insertion element were bio- and serotyped. The presence of hmw genes for adherence, the genetic profile, and the ability to form biofilm in vitro were investigated. A total of 15 isolates were IS1016-positive, whereof 12 were nontypeable. All 12 nontypeable isolates were obtained from healthy carriers, and 92% of the isolates were biotype I. They cross-reacted to some extent with type-specific antisera or exhibited a restricted genetic diversity like encapsulated strains. Furthermore, they lacked hmw-genes, and their ability to form biofilms was comparable with a capsule-deficient type b strain. Although this subset of strains mimicked traits usually exhibited by encapsulated strains, the isolation frequency did not seem to have been affected by vaccination.
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