[Reduced utilization of antibiotics in Swedish hospitals. Considerable variations between hospitals concerning choice and use of preparations]. / Antibiotikaförbrukningen har minskat på svenska sjukhus. Stora variationer i preparatval och förbrukning mellan sjukhusen.

Defined daily dose (DDD) consumption of antibiotics in 26 Swedish hospitals decreased by an average of 25% from 1990 to 1998, according to statistics from Apoteket AB. In one hospital, the decrease was 61%. Average consumption of tetracyclines and penicillins, expressed as percentage of total antibiotics consumption, decreased by 5% and 7% respectively, while quinolones and cephalosporins increased by 4% and 7% respectively. Consumption of tetracyclines and quinolones varied between individual hospitals by a factor of four.

A late exclusion of bacteriophage T4 can be suppressed by Escherichia coli GroEL or Rho.

A litCon mutation in Escherichia coli TU6 results in exclusion of bacteriophage T4 during the late, morphogenetic stage of its development at low temperatures. DNA was synthesized continuously in the infected cells, but less than 10% of the DNA made by 90 min after infection was packaged into DNAase-resistant particles, few viable phage were formed, and the cells lysed poorly. The exclusion could be relieved by conditions leading to elevated levels, determined immunologically, of the E. coli Rho protein (believed to be involved in regulation of T4 transcription), or chromosomally encoded E. coli GroEL (a chaperone known to be involved in phage assembly), or by supplying GroEL in trans from a plasmid. The two suppressing proteins appeared to act independently of each other. GroEL-suppression restored packaging to normal levels, perhaps by preventing GP23 from activating the host Lit protein; in addition DNA synthesis was delayed and reduced and cell lysis enhanced, demonstrating involvement of GroEL in both these processes. Rho suppression was less efficient. Since both transcription-termination-proficient and transcription-termination-deficient Rho suppressed, the results raise the possibility that Rho has a role during T4 development not directly involving transcription regulation.

Escherichia coli Rho factor is involved in lysis of bacteriophage T4-infected cells.

A Rid (Rho interaction deficient) phenotype of bacteriophage T4 mutants was defined by cold-sensitive restriction (lack of plaque formation) on rho+ hosts carrying additional polar mutations in unrelated genes, coupled to suppression (plaque formation) in otherwise isogenic strains carrying either a polarity-suppressing rho or a multicopy plasmid expressing the rho+ allele. This suggests that the restriction may be due to lower levels of Rho than what is available to T4 in the suppressing strains.--Rid394 X 4 was isolated upon hydroxylamine mutagenesis and mapped in the t gene; other t mutants (and mot, as well as dda dexA double mutants) also showed a Rid phenotype. In liquid culture in strains that restricted plaque formation Rid394 X 4 showed strong lysis inhibition (a known t- phenotype) but no prolonged phage production (another well-known t- phenotype). This implies that when Rho is limiting the t mutant shuts off phage production at the normal time. Lysis inhibition was partially relieved, and phage production prolonged to varying extents depending on growth conditions in strains that allowed plaque formation. No significant effect on early gene expression were found. Apparently, both mutant (polarity-suppressing) and wild-type Rho can function in prolonging phage production and partially relieving lysis inhibition of Rid394 X 4 when present at a sufficiently high level, and Rho may play other role(s) in T4 development than in early gene regulation.

Control of early gene expression of bacteriophage T4: involvement of the host rho factor and the mot gene of the bacteriophage.

Many early mRNA species of bacteriophage T4 are not synthesized after infection of Escherichia coli in the presence of chloramphenicol. This has been interpreted as a need for T4 protein(s) to be synthesized to allow expression of some early genes, e.g., those for deoxycytidinetriphosphatase, deoxynucleosidemonophosphate kinase and UDP-glucose-DNA beta-glucosyltransferase. In the experiments described here, early mRNA of bacteriophage T4 was allowed to accumulate during chloramphenicol treatment. After the addition of rifampin to inhibit further RNA synthesis, and subsequent removal of chloramphenicol, the accumulated mRNA was permitted to express itself into measured enzyme activities. It was shown that the early mRNA species coding for deoxycytidinetriphosphatase and UDP-glucose-DNA beta-glucosyltransferase could be formed in the presence of chloramphenicol if the E. coli host cell carried a mutation in the structural gene for the RNA chain termination factor rho. This was interpreted to mean that T4 protein(s) with anti-rho activity is normally required for the expression of these two early genes. An altered rho-factor could not, however, relieve the need of phage protein synthesis for the formation of another early mRNA, that coding for deoxynucleosidemonophosphate kinase. In this case the mot gene of T4 seemed to be involved, since the primary infection of E. coli cells with the mot gene mutant tsG1 did not allow subsequent deoxynucleoside monophosphate kinase mRNA synthesis after wild-type phage infection in the presence of chloramphenicol. In control experiments, deoxynucleoside monophosphate kinase mRNA synthesis induced by wild-type phage superinfecting in the presence of chloramphenicol was facilitated by the primary infection with T4 phage containing an unmutated mot gene.

Evidence for a diffusible T4 bacteriophage protein governing the initiation of delayed early RNA synthesis.

Two forms of prereplicative phage RNA can be discerned in Escherichia coli early after infection with bacteriophage T4, immediate early and delayed early RNA. The transition from immediate early to delayed early RNA synthesis is inhibited by chloramphenicol. The present work presents evidence for the existence of a phage-specific protein, which effects this transition. Delayed early RNA formation was measured by a cistron-specific enzyme-forming-capacity method, in which RNA synthesized in the presence of chloramphenicol was allowed to express itself into enzyme activity after (i) the addition of rifampin to inhibit further transcription and (ii) subsequent removal of chloramphenicol. As representatives of delayed early transcription, the two phage-specific enzymes dCTPase and deoxynucleotide kinase were chosen. Primary infection with a phage mutant defective in one of these two enzymes was found to induce a diffusible factor, which in the presence of chloramphenicol could effect the formation of delayed early RNA corresponding to the missing enzyme, upon superinfection with wild-type phage. The activity of this factor, acting in trans, was abolished by the amino acid analogue ethionine. Mutation in the suA gene of the host did not relieve phage of the apparent need for protein synthesis in the transition from immediate early to delayed early phage RNA synthesis.

Regulation of early mRNA synthesis after bacteriophage T4 infection of Escherichia coli.

Regulation of T4-specific mRNA synthesis was studied during leucine starvation of a leucine-requiring stringent Escherichia coli B strain. This was done by imposing starvation prior to T4 infection and then letting RNA synthesis proceed for different time periods. Rifampin or streptolydigin was added to stop further RNA synthesis, and protein synthesis was restored by addition of leucine. Samples were withdrawn at different times, and the enzyme-forming capacities found that, during conditions which elicit the stringent response in uninfected bacteria, immediate early mRNA is not stringently regulated. This conclusion contradicts the earlier conclusion of others, obtained by measuring incorporation of radioactive uracil; this is explained by the observation of Edlin and Neuhard (1967), confirmed and extended by us to the T4-infected cell, that the incorporation of uracil into RNA of a stringent strain is virtually blocked by amino acid starvation, whereas that of adenine continues at 30 to 50% of the rate seen in the presence of the required amino acid.