Robert C. Spencer

Direct sequencing of the amplified structural gene and promoter for the extended-broad-spectrum β-lactamase TEM-9 (RHH-1) of Klebsiella pneumoniae

Extended-broad-spectrum beta-lactamase TEM-9, detected in a clinical isolate of Klebsiella pneumoniae, confers high-level resistance to recent cephalosporins, in particular ceftazidime, and to the monobactam aztreonam. Using oligonucleotide probes, we found that the plasmid gene blaT-9 encoding TEM-9 differs from characterized blaT genes by a new combination of already known mutations. Gene blaT-9 was further studied by direct sequencing of an amplified 1.1-kb DNA fragment which contained the open reading frame and its promoter. Analysis of the nucleotide and of the deduced amino acid sequence confirmed the hybridization results and indicated that TEM-9 differs from TEM-1 by four amino acid substitutions: Phe at position 19 and Met at position 261, which have been found in TEM-4 and are known not to expand the enzyme substrate range; Lys 102, detected in TEM-3 and TEM-4, and Ser 162, present in TEM-5 and TEM-7. Each of the latter substitutions enlarges the substrate spectrum of the enzymes and they are found associated for the first time in TEM-9.

Evaluation of three methods for culturing long intravascular catheters

During a one-year period, 236 intravascular catheter tips were investigated by culturing the outside by rolling the tips on the surface of blood agar plates, the inside by flushing with nutrient broth, and finally by culture after ultrasonication. Clinical information was collected prospectively by visiting the ward and symptoms and signs of catheter infection were correlated with the results of the catheter cultures. Coagulase-negative staphylococci were the organisms that were most frequently isolated from the catheters. The results of culture showed a clear bimodal distribution, and counts of 100 colony-forming units (cfus) and culture from the inside of the catheters were the best predictors of infection. Almost all infected catheters were colonized both on the inside and outside.

The emergence of bacterial resistance in hospitals—a need for continuous surveillance

The antibiotic sensitivities of a total of 220,000 isolates from 44 hospitals collected over 2.5 years were monitored by computer. Gram-negative organisms account for 63% of the total, the most common being Escherichia coli (43%). Staphylococcus aureus was the most frequently isolated Gram-positive organism (44%). The organism most commonly isolated from blood was E. coli; this organism was susceptible to ceftazidime (100%), ampicillin (47%), gentamicin (99%) and co-trimoxazole (85%). The organism most frequently isolated from sputum was Haemophilus influenzae; this organism was susceptible to ceftazidime (99%), cefuroxime (99%), ampicillin (89%) and erythromycin (78%). A 15-fold increase in the use of ceftazidime over the past 4 years has not been accompanied by increased resistance in common pathogens. Analysis shows that the susceptibility of E. coli and Pseudomonas aeruginosa to ceftazidime has remained constant throughout the duration of this survey. The data collected from this type of survey can be used to determine local trends in antibiotic susceptibility and hence aid the rational use of antibiotics in hospitals.

Septicaemia in a renal transplant patient due to Mycoplasma hominis.

Opportunistic infections are an important cause of mortality in transplant patients. Here we report a case of Mycoplasma hominis septicaemia in a renal transplant patient that was successfully treated with doxycycline.

Survival of Salmonella species in eggs poached using a microwave oven

The use of microwave ovens is becoming increasingly popular, but there is little data on the bactericidal effect of this mode of cooking. Following a family outbreak of gastroenteritis due to Salmonella enteritidis PT4, where eggs poached in a microwave oven were the suspected source, we investigated the survival of Salmonella spp. in artificially contaminated eggs cooked in a microwave oven. The survival of six serotypes of Salmonella at various inocula were studied, after cooking the eggs using two recognized poaching methods. Salmonellae were readily recovered after cooking if the yolk was still soft, whichever serotype, inoculum or cooking method was used. The survival of organisms was related to the number of organisms present in the raw eggs. The advice regarding eating lightly cooked eggs should be the same whether microwave or more conventional cooking techniques are used.

A re-evaluation of the pour plate blood culture method for the detection of candida and other septicaemias

Over a 1-year period the use of a pour plate in detecting significant septicaemias due to bacteria and fungi was evaluated and compared with a conventional broth blood culture system. Of 207 significant bacterial blood culture isolates only 113 (56%) were detected by the pour plate. However, three out of four candidaemias were detected by the pour plate method alone. Despite its low positivity rate, the pour plate is cheap and allows for early detection of bacteraemia and candidaemia.

In vitro activity of roxithromycin against Moraxella catarrhalis

The in vitro activity of roxithromycin was compared with that of the other antimicrobial agents (erythromycin, tetracycline, ampicillin, and cotrimoxazole) against 188 distinct clinical isolates of Moraxella catarrhalis. Of these, 106 strains (66%) produced beta-lactamase. The MIC90 of roxithromycin was 0.25 micrograms/ml compared with values of 0.5, 1, greater than 8, greater than 8:0.4 micrograms/ml for erythromycin, tetracycline, ampicillin, and sulfamethoxazole-trimethoprim, respectively. These results, allied with its improved pharmacokinetic properties, suggest that roxithromycin should be an effective treatment in children and adults for upper and lower respiratory tract infections caused by M. catarrhalis.

Enumeration of bacteria in clinically significant blood cultures in neutropenic and non-neutropenic patients using a pour plate method

A 3-year review of clinically significant positive blood cultures was undertaken to assess any differences in the blood bacterial count between haematological neutropenic and other non-neutropenic patients. The pour-plate method was used. In Gram-positive infections the pour plate contained colonies in 61% of haematological patients and in 41% of others. In Gram-negative infection the figures were 54% and 25% respectively. The mean numbers of bacteria per ml of blood were increased in haematological patients compared with the others for both groups of organisms.

The use of aztreonam in the treatment of uncomplicated gonorrhoea

A total of 57 men and 26 women with uncomplicated gonorrhoea was treated with 1 g aztreonam intramuscularly. The cure rate was 96% and included successful treatment of 4 infections due to beta-lactamase producing organisms and 8 patients with pharyngeal involvement. The minimum inhibitory concentrations of aztreonam in vitro were lower than those of penicillin and similar to cefuroxime, and side-effects were minimal. It is concluded that aztreonam is effective against Neisseria gonorrhoeae in vivo and in vitro.

Antibiotic dependence in a strain of Neisseria pharyngis

A strain of Neisseria pharyngis was isolated in pure culture from a specimen of sputum. Growth was markedly enhanced by sub-lethal concentrations of rifampicin, spectinomycin, erythromycin and clindamycin. The effect was temporary with tetracycline. The possible mechanisms of this phenomenon are discussed.