Pseudomonas aeruginosa and antibiotics

Pseudomonas aeruginosa and antibiotics

324 INJURY: THE BRITISH JOURNAL OF ACCIDENT SURGERY Variants of Staphylococcus Aureus Dwarf-colony variants of Staphylococcus aureus resistant to am...

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Variants of Staphylococcus Aureus Dwarf-colony variants of Staphylococcus aureus resistant to aminoglucoside antibiotics (streptomycin, neomycin, framycetin, paromomycin, kanamycin and gentamicin) were obtained by growth of strains isolated from wounds or skin in the presence of one of these antibiotics or of linoleic acid. These strains survived better on the normal skin, presumably because of increased resistance to unsaturated fatty acids. It is argued that the use of aminoglucoside antibiotics might, for this reason, encourage the survival of staphylococci on the skin. Highly pigmented dwarf colony forms of Staph. aureus have been found in pathological material, and may be missed on routine bacteriological examination of wounds or pus. They revert readily to normal colony forms which are sensitive to aminoglucoside antibiotics. LACEY, R. W. (1969), ' Dwarf-colony Variants of Staphylococcus aureus, Resistant to Aminoglucoside Antibiotics and to a Fatty Acid ", J. med. Microbiol., 2, 187.

A Capsulate Staphylococcus Aureus A capsulate Staphylococcus aureus isolated from an infected hand laceration was found to differ from modal strains of Staph. ato'eus in a number of respects. The colonies were mucoid, they were not lysed by any of the standard typing phages, and they failed to ' clump ' in plasma. Non-capsulated variants were obtained on prolonged subculture in nutrient broth. The capsulated strain showed greater virulence for mice than modal strains of non-capsulated variants. SCOTT, A. C. (1969), ' A Capsulate Staphylococcus aureus ', J. reed. Microbiol., 2, 253.

Pseudomonas Aeruginosa and Antibiotics One thousand four hundred and fifty-two strains of Pseudomonas aeruginosa were studied in 1966-9. It was found that the proportion of strains resistant to polymyxin and gentamicin increased slightly during this time whereas there was for most of the period of the study a steady rise in the proportion resistant to carbenicillin. Towards the end of the study, however, there was a sudden rise in the proportion of strains resistant to carbenicillin and they displaced all the sensitive strains. Resistance could be acquired within 24 hours of exposure to this antibiotic and in some cases resistant strains appeared in persons that had not received carbenicillin. The evidence suggested that resistance could be transferred from one bacterial population to another. The most important part of the article for most clinicians is the final warning against the use of powerful antibacterial drugs for no more reason than that a demonstrably sensitive organism can be cultured from a patient. LOWBURY, E. J. L., KIDSON, A., WILLEY, H. A., AYLIFFE, G. A. J., and JONES, R. J., (1969), ' Sensitivity of Pseudomonas aeruginosa to Antibiotics: Emergence of Strains highly Resistant to Carbenicillin ', Lancet, 2, 448.

Bacteria and Ward Ventilation Eight hundred surgical patients treated in a subdivided ward with mechanical ventilation (7-8 air changes per hour) were compared with 926 patients in 2 open-plan wards. The incidence of nasal acquisition of Staphylococcus aureus was slightly lower in the mechanically ventilated than in the open-plan

Injury April 1970

wards when patients were in the ward for 2 weeks or less; in those who stayed longer than 2 weeks, the nasal acquisition rates were approximately the same in the mechanically ventilated subdivided and in the open type wards. The incidence of postoperative sepsis was approximately the same in both groups of patients. WHYTE, W., HowxE, J. G. R., and EAKIN, J. E. (1969), 'Bacteriological Observations in a mechanically ventilated Experimental Ward and in Two Openplan Wards ", J. reed. Microbiol., 2, 335.

Aseptic Practice in Hospital Wards The team of 2 doctors, a nurse, and a laboratory technician visited 140 wards in 14 hospitals in order to study and record what they have indulgently referred to as 'aseptic practice'. They found that 26 per cent of the patients were receiving at least one antibiotic for reasons that they were often unable to determine. Twenty-three different disinfectants were found to be in use, usually in the wrong concentration. • Contamination of equipment was more often closely related to the use of inadequate concentrations of disinfectant than to the type of disinfectant used '. Nearly half the floor mops tested were found to be contaminated, most often by Gram-negative organisms. Even when they were kept in disinfectant, a quarter of the mops were contaminated. Baths, lockers, and wash-bowls often yielded Gramnegative organisms and some holders of disposable bed pans went untreated and were heavily contaminated with faecal organisms. Jars of hand cream, antiseptic detergent creams, and liquid soaps containing hexachlorophane were often contaminated by Gram-negative organisms but hand cream dispensed from tubes was usually not. Lavatory and nail brushes were no less contaminated after being kept in disinfectant solution than when they were kept dry. The team recommended that when nail brushes are required they should be issued sterile. Dirty and foul linen were liable to be handled without regard for their bacterial population and to be mixed with ' clean ' linen. Facilities for isolating infected patients were inadequate more often than not and even when adequate facilities were available they went unused in about a quarter of the cases. Ancillary staff were particularly liable to carry pathogenic organisms from one patient to another. Most dressings were done in the wards and resulted in heavy contamination of bed linen. The team also showed clearly that the success of issuing materials from a central sterilizing department depended upon the understanding by the users of elementary bacteriological facts; indeed, the likely bacteriological value of any of the practices they studied was often nullified by carelessness or ignorance that was doubtless bolstered in some cases by the comfortable but misguided assumption that modern methods and materials of themselves made sure that all was well. AYLIFFE, G. A. J., BRIGHTWELL, K. M., COLLINS, B. J., and LOWBURY, E. J. L. (1969), 'Varieties of Aseptic Practice in Hospital Wards ', Lancet, 2, 1117.

Postoperative Clostridial Infections It may come as a shock to many readers that 85 cases of clostridial infection, of which 56 were frank gas gangrene, were recorded in 2 years in Britain.