Pneumococcal bacteraemia: 325 episodes diagnosed at St Thomas's Hospital.

Three hundred and twenty five episodes of pneumococcal bacteraemia occurred at St Thomas''s Hospital during 1970-84, accounting for 13.3% of all episodes of bacteraemia. Twice as many cases occurred in male as in female patients, and common predisposing factors included chronic chest disease, alcoholism, haematological malignancies, cirrhosis, and sickle cell anaemia. Mortality was 28.6% overall but only 11.8% among patients who received antibiotic treatment for at least 24 hours. Most patients (261) had pneumonia, 26 had meningitis, and eight were children with occult bacteraemia. The commonest serotype of pneumococcus in adults was type 3 (39 episodes), and these strains were associated with a high mortality. Other factors determining a fatal outcome included underlying disease (such as cirrhosis, malignancy, and chronic chest disease) and extrapulmonary infection. Almost half the survivors were treated for 10 days or less and became afebrile within 48 hours.     

Fusidic acid: new opportunities with an old antibiotic.

The extensive foreign experience with fusidic acid prior to its belated introduction to Canada is reviewed. Fusidic acid is a steroid antibiotic with minimal toxic and hormonal effects that is mainly excreted through the liver. It has a predominantly bactericidal action and does not shown cross-resistance with other antibiotics. Since organisms resistant to this drug form easily in vitro when exposed to low concentrations, complementary treatment with another antibiotic may be required in some clinical situations. Although fusidic acid is active in vitro against a number of organisms, to date it has mainly been used to treat serious infections due to Staphylococcus aureus. The agent appears to be particularly valuable in the treatment of bone and joint infections and in pediatric practice. Fusidic acid will soon be available in Canada for both oral and intravenous administration. Attainable antibiotic levels in many tissues and body fluids greatly exceed the minimum inhibitory concentrations.     

Staphylococcal bacteraemia,fusidic acid,and jaundice.

Fusidic acid was used to treat 131 out of 250 patients with staphylococcal bacteraemia over 10 years. Other antimicrobial agents were given to the 119 remaining patients. Thirty-seven patients were already jaundiced before antibiotic treatment was started. Jaundice developed during treatment in 38 out of 112 patients given fusidic acid (34%) and in two out of 101 patients given other antimicrobials. The incidence of jaundice was higher in patients given fusidic acid intravenously (48%) rather than by mouth (13%). Jaundice appeared within 48 hours after the administration of fusidic acid in 93% of these cases. When the drug was stopped serum bilirubin concentrations fell to normal values within four days in those patients in whom they had been previously normal and who survived the bacteraemic episode. Fusidic acid was associated with increasing jaundice in 13 of 19 patients (68%) already jaundiced before it was given. In six out of 32 patients who developed jaundice while receiving intravenous fusidic acid serum alkaline phosphatase activity was raised suggestive of cholestatic jaundice. The mechanism in the remaining patients was unknown. Fusidic acid, particularly the intravenous preparation, in invaluable in treating severe staphylococcal infection but should be used with caution in patients with abnormal liver function. Patients receiving intravenous fusidic acid should be given the oral form of the drug as soon as their clinical condition permits.     

Molecular analysis of fusidic acid resistance in Staphylococcus aureus

Fusidic acid is a potent antibiotic against severe Gram-positive infections that interferes with the function of elongation factor G (EF-G), thereby leading to the inhibition of bacterial protein synthesis. In this study, we demonstrate that fusidic acid resistance in Staphylococcus aureus results from point mutations within the chromosomal fusA gene encoding EF-G. Sequence analysis of fusA revealed mutational changes that cause amino acid substitutions in 10 fusidic acid-resistant clinical S. aureus strains as well as in 10 fusidic acid-resistant S. aureus mutants isolated under fusidic acid selective pressure in vitro. Fourteen different amino acid exchanges were identified that were restricted to 13 amino acid residues within EF-G. To confirm the importance of observed amino acid exchanges in EF-G for the generation of fusidic acid resistance in S. aureus, three mutant fusA alleles encoding EF-G derivatives with the exchanges P406L, H457Y and L461K were constructed by site-directed mutagenesis. In each case, introduction of the mutant fusA alleles on plasmids into the fusidic acid-susceptible S. aureus strain RN4220 caused a fusidic acid-resistant phenotype. The elevated minimal inhibitory concentrations of fusidic acid determined for the recombinant bacteria were analogous to those observed for the fusidic acid-resistant clinical S. aureus isolates and the in vitro mutants containing the same chromosomal mutations. Thus, the data presented provide evidence for the crucial importance of individual amino acid exchanges within EF-G for the generation of fusidic acid resistance in S. aureus.     

Susceptibility to and resistance determinants of fusidic acid in Staphylococcus aureus isolated from Chinese children with skin and soft tissue infections

This study aims to determine the resistance rates and determinants of fusidic acid among Staphylococcus aureus isolates collected from Chinese pediatric patients with skin and soft tissue infections (SSTIs). Between 2008 and 2009, a total of 186 clinical S. aureus isolates were collected from the pediatric patients with SSTIs, abscess (44.6%) was the most common SSTI in children 0-16 years old. Four clinical isolates (4/186, 2.2%) were resistant to fusidic acid. Two of these isolates were methicillin-resistant S. aureus (MRSA) that carry the fusC gene. The other two isolates were methicillin-sensitive S. aureus (MSSA) that carry the fusB gene. In the two fusB-positive clinical isolates, the fusB gene was located in a transposon-like element that has 99% identity with a pUB101 fragment from S. aureus. The four fusidic acid-resistant clinical isolates were ST1-MRSA-SCCmecV-t127, ST93-MRSA-SCCmecIII-t202, ST680-MSSA-t5415, and ST680-MSSA-t377. The fusidic acid resistance rate of S. aureus isolated from Chinese pediatric patients with SSTIs was low, and the genes fusB and fusC were the main resistance determinants. The transposon-like element that contains the fusB gene might participate in the transmission of fusidic acid resistance genes. This is the first report regarding the emergence of fusidic acid-resistant clinical S. aureus isolates in mainland China.     

First synthesis of racemic saphenamycin and its enantiomers. investigation of biological activity

The natural antibiotic saphenamycin, 6-[1-(2-hydroxy-6-methyl-benzoyloxy)-ethyl]-phenazine-1-carboxylic acid, was synthesized from saphenic acid using temporary allyl protection of carboxy and phenoxy functionalities. Resolution of racemic saphenic acid was performed by crystallization of the corresponding (-)-brucine diastereomeric salts and the absolute configuration of (-)-brucinium (-)-saphenate was determined by X-ray crystallography to have R-configuration. This also proved to be the configuration of natural saphenic acid. Enantiomers of saphenamycin were obtained from resolved saphenic acid and screened against a range of skin flora and resistant Staphylococcus aureus strains. Biological activities of saphenamycin enantiomers were compared with that of the synthetic racemate as well as earlier reported activities of saphenamycin isolated from natural sources. No significant difference was observed in activity of the enantiomers of saphenamycin, which revealed that the chirality of saphenamycin has no consequences for the antibiotic activity. Saphenamycin proved to be a potent antibiotic against fusidic acid and rifampicin resistant S. aureus strains showing MIC of 0.1-0.2 microg/mL.     

Mutations in the G-domain of elongation factor G from Thermus thermophilus affect both its interaction with GTP and fusidic acid

Two hypersensitive and two resistant variants of elongation factor-G (EF-G) toward fusidic acid are studied in comparison with the wild type factor. All mutated proteins are active in a cell-free translation system and ribosome-dependent GTP hydrolysis. The EF-G variants with the Thr-84-->Ala or Asp-109-->Lys mutations bring about a strong resistance of EF-G to the antibiotic, whereas the EF-Gs with substitutions Gly-16-->Val or Glu-119-->Lys are the first examples of fusidic acid-hypersensitive factors. A correlation between fusidic acid resistance of EF-G mutants and their affinity to GTP are revealed in this study, although their interactions with GDP are not changed. Thus, fusidic acid-hypersensitive mutants have the high affinity to an uncleavable GTP analog, but the association of resistant mutants with GTP is decreased. The effects of either fusidic acid-sensitive or resistant mutations can be explained by the conformational changes in the EF-G molecule, which influence its GTP-binding center. The results presented in this paper indicate that fusidic acid-sensitive mutant factors have a conformation favorable for GTP binding and subsequent interaction with the ribosomes.     

Morphological stages of Bacillus subtilis sporulation and resistance to fusidic acid.

During spore development of Bacillus subtilis both protein synthesis and sporulation become resistant to the antibiotic fusidic acid. This resistance develops at the time when asymmetric prespore septa are formed. Simultaneously ribosomes lose their ability to bind fusidic acid, as demonstrated by their affinity chromatography with the immobilized drug. Mutants resistant to fusidic acid during growth are oligosporogenous; their sporulation development is blocked before septum formation. These results indicate that normal ribosomes are needed for prespore septation sporulation; only after septation can protein synthesis be maintained, throughout the development period, by fusidate resistant ribosomes.     

Antibiotic treatment of abscesses of the central nervous system.

Samples of intracranial pus and serum from 32 patients were assayed to determine the concentrations reached in them of penicillin, ampicillin, cloxacillin, cephaloridine, gentamicin, chloramphenicol, fusidic acid, and lincomycin. Metronidazole had not been given. Penicillin penetrated abscesses reasonably well, but other beta-lactam antibiotics did not. The penetration of chloramphenicol was erratic. Aminoglycosides penetrated poorly, but lincomycin and fusidic acid penetrated well. Assay of sulphonamides and co-trimoxazole in pus was unreliable. These studies indicate that treatment of abscesses of the central nervous system should be considered according to the site and the likely antecedent cause. Abscesses of sinusitic origin, usually in the frontal lobe, yield penicillin-sensitive streptococci. Penicillin is the drug of choice. Abscesses of otitic origin, usually in the temporal lobe, yield a mixed flora, often including anaerobic bacteria. Multiple antibiotic therapy is indicated. Abscesses of metastatic or cryptogenic origin yield streptococci or mixed cultures, and multiple therapy is appropriate while awaiting the bacteriological results. Spinal and post-traumatic abscesses yield Staphylococcus aureus, and fusidic acid is the drug of choice.     

Biological cost and compensatory evolution in fusidic acid-resistant Staphylococcus aureus

Fusidic acid resistance resulting from mutations in elongation factor G (EF-G) of Staphylococcus aureus is associated with fitness costs during growth in vivo and in vitro. In both environments, these costs can be partly or fully compensated by the acquisition of secondary intragenic mutations. Among clinical isolates of S. aureus, fusidic acid-resistant strains have been identified that carry multiple mutations in EF-G at positions similar to those shown experimentally to cause resistance and fitness compensation. This observation suggests that fitness-compensatory mutations may be an important aspect of the evolution of antibiotic resistance in the clinical environment, and may contribute to a stabilization of the resistant bacteria present in a bacterial population.     

Susceptibility to selected chemotherapeutics of Staphylococcus aureus strains resistant to methycyline isolated from clinical materials in the years 1991-1992 and 1997

The susceptibility to selected chemotherapeutic agents was determined in 100 strains of Staphylococcus aureus methicillin-resistant (MRSA) isolated from clinical materials in 1991-1992 (50 strains) and in 1997 (50 strains). Two methods were used for the determination: disc method and antibiotic dilution in agar. The minimal inhibitory concentration (MIC) was determined for vancomycin, teicoplanin, furazolidone, nitrofurantoin, ofloxacin, gentamicin, netilmicin and trimethoprim. The concentrations of the chemotherapeutics in the substrate ranged from 0.125 to 512 mg/l. The obtained results served for drawing of the following conclusions: all studied MRSA strains isolated in 1991-1992 and in 1997 were sensitive to glycopeptide antibiotics: vancomycin and teicoplanin, to nitrofurans: nitrofurantoin and furazolidone, and to fusidic acid. MRSA strains isolated in 1991-1992 were sensitive to ofloxacin, but in 1997 about 80% of the strains were resistant to that antibiotic, and this resistance was noted in S. aureus strains with homogeneous resistance to methicillin. Increasing frequency of resistance to mupirocin was found, in 1991-1992 4% of the strains were resistant, and in 1997 the resistance of MRSA to that antibiotic was found in 12%. No changes occurred in the sensitivity of staphylococci to trimethoprim/sulfamethoxazole (cotrimoxazole). About 94% of strains in 1991-1992 and 1997 were sensitive to that drug. The sensitivity to cotrimoxazole is connected with one of its components (trimethoprim), with 94% of MRSA strains sensitive to it.     

Microbiological Activities of Lysostaphin and Penicillins Against Bacteriophage 80/81 Strains of Staphylococcus aureus

Using 20 clinical isolates of S. aureus (all bacteriophage 80/81 type), we found that lysostaphin inhibits the growth of all cultures at concentrations significantly lower than those observed with any of eight penicillins, a penicillin-like compound (cephalothin), or fusidic acid (a steroid antibiotic). All test cultures were shown to be resistant to penicillin G, ampicillin, and propicillin. Of the remaining penicillins (all penicillinase-insensitive), oxacillin, nafcillin, cloxacillin, and cephalothin were approximately equal in antimicrobial activity. Ancillin was slightly less active, and methicillin was even lower in potency. Cultures varied more widely in susceptibility to fusidic acid. None of the clinical isolates tested was found to be resistant to lysostaphin.     

Purification and characterization of a novel extracellular Streptomyces lividans 66 enzyme inactivating fusidic acid.

The wild-type strain Streptomyces lividans 66 is resistant against the steroid-like antibiotic fusidic acid. Comparative studies of the wild-type strain and a fusidic acid-sensitive mutant allowed the identification of an extracellular enzyme which inactivates fusidic acid. With the help of a combination of ultrafiltration and chromatographies with Phenyl-Sepharose and an anion exchanger, the enzyme was highly purified. Its apparent molecular mass is 48 kDa, its optimal activity ranges between 45 and 55 degrees C, and its optimal pH is 6.0 to 9.0. It is stimulated by neither monovalent nor divalent ions. The enzyme acts as a specific esterase which removes the acetyl group at C-16 from fusidic acid. The resulting intermediate is unstable, and spontaneous lactonization between C-21 and C-16 occurs rapidly.     

Are bloodstream leukocytes Trojan Horses for the metastasis of Staphylococcus aureus?

Staphylococcus aureus bacteraemia remains very difficult to treat, and a large proportion of cases result in potentially lethal metastatic infection. Unpredictable and persistent bacteraemia in the face of highly active, usually bactericidal antibiotics is the strongest predictor of death or disseminated disease. Although S. aureus has conventionally been considered an extracellular pathogen, much evidence demonstrates that it can survive intracellularly. In this Opinion article, we propose that phagocytes, and specifically neutrophils, represent a privileged site for S. aureus in the bloodstream, offering protection from most antibiotics and providing a mechanism by which the bacterium can travel to and infect distant sites. Furthermore, we suggest how this can be experimentally confirmed and how it may prompt a change in the current paradigm of S. aureus bacteraemia and identify better treatment options for improved clinical outcomes.     

Combinations of Clavulanic Acid and other β-lactam Antibiotics against Strains of Pseudomonas aeruginosa, Serratia marcescens and other Bacteria

Combinations of clavulanic acid, a new β-lactamase inhibitor, with five cephalosporins and one cephamycin were tested against cell-free β-lactamases obtained from Serratia marcescens, Pseudomonas aeruginosa and an Enterobacter strain, 265A. Cefotaxime was the most resistant antibiotic and cephalothin the most sensitive antibiotic to β-lactamases. Low concentrations of clavulanic acid gave some protection against the Serratia and Pseudomonas enzymes. The most active source of β-lactamase was the 265A strain, against which only cefotaxime was highly resistant. Clavulanic acid had only a slight inhibitory effect on this enzyme, which was confirmed by an agar method, and potentiated slightly the activity of cephalothin and cefoxitin against two β-lactamase producing strains of Staphylococcus aureus. Lysis by cephalothin of one strain of S. marcescens was potentiated in the presence of clavulanic acid.     

Disappearance of differences in antibiotic resistance of Staphylococcus aureus strains isolated in hospitals and in general practice

There is general opinion that Staphylococcus aureus strains isolated in hospitals are more frequently resistant to antibiotics than community strains, however, the increasing resemblance between hospital and community strains has been recently reported. The aim of the study was to compare the antibiotic resistance and phage-type pattern of S. aureus strains isolated from patients treated either in hospitals or in general practice in northern part of Poland. The study was conducted on 771 S. aureus strains isolated from different specimens. Phage typing was performed according to the method of Blair and Williams. The drug susceptibility was determined by the disc-diffusion method. There were no significant differences in antibiotic resistance or phage-type pattern when hospital and community methicillin-sensitive S. aureus (MSSA) strains were compared. The most MSSA were resistant to penicillin (84.6% and 82.1% respectively) and doxycycline (49.3% and 50.4% respectively) whereas they were rarely resistant to other antibiotics. The predominance of phage group II was found in both hospitals (28.0%) and general practice (29.9%). Phage group III, usually associated with hospitals, occurred in small percentage (12.9% and 9.4% respectively) while to this group predominantly (76.6%) multiresistant methicillin resistant S. aureus (MRSA) isolated in hospitals belonged. These results suggest, that there is only slight difference in antibiotic resistance between hospital and community S. aureus strains. Antibiotic resistance pattern mainly results from frequency of appearance of MRSA, mostly occurring in hospitals.     

Antibiotic resistance dynamics and isolation rate of staphylococci and enterococci from patients of reconstructive surgery units

The dynamics of isolation of staphylococci and enterococci from clinical material of patients and their antibiotic susceptibility within a 5-year period (2005-2009) was analysed. 5990 isolates were tested: 1250 isolates of Staphylococcus aureus, 3268 isolates of S. epidermidis, 1005 isolates of Enterococcus faecalis and 467 isolates of E. faecium. Grampositive infections were shown to be prevailing within the last 2-3 years, the nosocomial epidermal staphylococci more and more replacing S. aureus (the ratio of S. epidermidis and S. aureus in 2009 was 3.3). The isolation rate of E. faecalis significantly increased (by 3.5 times) and the ratio of E. faecalis and E. faecium in 2009 was 4.3. The microflora composition with respect to the isolation source was analysed and its clinical significance was estimated. The study of the antibiotic susceptibility showed that oxacillin had its own specific niche, while antibiotics active against resistant grampositive cocci, such as rifampicin, fusidic acid, fluoroquinolones (moxifloxacin), cefoxitin, as well as amoxicillin/clavulane in infections due to E. faecalis, might be considered as the drugs of choice. In the treatment of nosocomial infections, when the etiological role of MRSA or VRE is suspected or confirmed, the complex therapy should obligatory include the most active antibiotics (vancomycin or linezolid among them).     

Randomised controlled trial of antibiotics in patients with cough and purulent sputum.

Two hundred and twelve adults with cough and purulent sputum of up to one week''s duration were allocated randomly to treatment with doxycycline or placebo capsules for up to 10 days. Cough, purulent sputum, feeling "off colour," and time off work lasted as long in treatment and control groups, but running nose persisted for a shorter time in the doxycycline group. The number of new episodes of lower respiratory tract infections, vaginal infections, gastrointestinal upsets, and otitis media over the next six months were the same in both groups, but fewer new upper respiratory infections were experienced by the doxycycline-treated patients. There is no consensus among doctors about using antibiotics in patients with cough and purulent sputum, and these results indicate that otherwise healthy people with these symptoms will usually get better without antibiotic treatment.     

Decreased resistance to antibiotics and plasmid loss in plasmid-carrying strains of Staphylococcus aureus treated with ascorbic acid

The effect of ascorbic acid on plasmid-coded antibiotic resistance in Staphylococcus aureus was investigated. Several strains of S. aureus were cultured in the presence of 1 mM ascorbate for 6 h. This treatment induced an increased loss of resistance markers in 4 of 6 strains tested, and agarose gel electrophoresis showed this disappearance of plasmid DNA in ascorbate-induced susceptible colonies. The presence of ascorbate induced a 50-75% decrease in minimal inhibitory concentrations of different antibiotics for resistant strains. When ascorbate is added, formerly subinhibitory concentrations of penicillin or tetracycline have an increased inhibitory effect on resistant strains and even induced the death of 25-93% of the initial population. These results suggest that ascorbate can induce the loss of several plasmids of S. aureus, and that the levels of antibiotic resistance are also affected by the presence of this compound.     

Biliary tract disease as a risk factor for Plesiomonas shigelloides bacteraemia: a nine-year experience in a Hong Kong hospital and review of the literature

We report the epidemiology, clinical disease spectrum, treatment, and outcome of Plesiomonas shigelloides bacteraemia in our hospital over a nine-year period and compare the characteristics of patients with P. shigelloides bacteraemia in our hospital with those reported in the literature. During the nine-year period (1995--2003), a total of seven patients developed P. shigelloides bacteraemia. All cases occurred during the late spring, summer, and early autumn (May-October). All patients were over 75 and had underlying diseases (biliary tract diseases in four and malignancies in three). Six had acute cholangitis and five had polymicrobial bacteraemia. Overall two patients died. Compared with patients with P. shigelloides bacteraemia reported in the literature, patients with P. shigelloides bacteraemia in our hospital were associated with old age (P<0.001), underlying biliary tract diseases (P<0.001), acute cholangitis (P<0.001), and polymicrobial bacteraemia (P<0.001). There are major geographical differences of disease association in P. shigelloides bacteraemia. The sources of P. shigelloides in our patients were probably in the gastrointestinal tract.