H. A. Lilly

Hand disinfection: a comparison of various agents in laboratory and ward studies

The efficacy of 14 handwashing or disinfectant preparations was compared in laboratory tests on staff volunteers. The test organism, Escherichia coli, was applied to the fingertips and log reductions (LR) were measured following treatment with the test agent and control preparations (70% isopropanol and non-medicated bar soap). Alcoholic preparations, particularly n-propanol and isopropanol were the most effective showing LRs of 3.1-3.8. Chlorhexidine (LR 2.9) and povidone-iodine detergent preparations were significantly more effective than non-medicated soap (LR 2.1), but triclosan products were not. In addition the residual effect of several of these formulations was assessed after 10 applications by comparing the survival of E. coli on the fingertips over a 32-min period. This number of handwashes compares favourably with those recorded during an 8 h nursing shift. Chlorhexidine-detergent consistently showed the best residual activity. Alcoholic formulations showed little or no residual effect. The survival studies show that on the whole gram-positive organisms (Staphylococcus aureus and Candida albicans) survive better on the skin than Gram-negative bacilli (GNB). However, it would seem that GNB which are considered to be residents (Acinetobacter calcoaceticus and Enterobacter spp.) survive much better than many other GNB (Pseudomonas aeruginosa, E. coli and Proteus vulgaris). The Klebsiella species varied in survival times. Random sampling of ward staff hands showed that contamination with S. aureus and GNB was greater in dermatological and general wards than in an isolation unit, where handwashing or disinfection was carried out after every patient contact. No cross-infection occurred in the isolation ward during periods of study in which 70% alcohol, chlorhexidine-detergent and non-medicated soap were used.

SENSITIVITY OF PSEUDOMONAS ÆRUGINOSA TO ANTIBIOTICS: EMERGENCE OF STRAINS HIGHLY RESISTANT TO CARBENICILLIN

Abstract Sensitivity tests on 1452 strains of Pseudomonas œruginosa ( pyocyanea ) isolated from burns between 1966 and 1969 showed a slight increase in the proportion of strains highly sensitive to polymyxin and to gentamicin; resistance to carbenicillin, on the other hand, increased progressively, and in 1969 highly resistant carbenicillinase-producing strains suddenly appeared and quickly displaced all other Ps. œruginosa from the ward. The highly resistant strains were fully virulent for mice. Phage and serological typing showed that two distinct types acquired this form of resistance within 24 hours. Sensitive strains of the same types found in the same patients acquired a high degree of carbenicillin resistance, with carbenicillinase production, on growth in presence of carbenicillin; no increase in resistance to carbenicillin was found when the sensitive strains were grown in ampicillin or cloxacillin. The instability of the resistant strains and their enhanced reversion to sensitivity when exposed to acriflavine suggests that an extrachromosomal factor was responsible for resistance; the transfer of this factor to another strain could account for the nearly simultaneous emergence of carbenicillin resistance in two different types of Ps. œruginosa in the burns unit.

Ward floors and other surfaces as reservoirs of hospital infection.

Impression plates from initially clean horizontal surfaces and floor areas in surgical wards showed a rapid accumulation of bacteria, mainly micrococci, which reached a fluctuating equilibrium after about 24 h. A later increase in bacterial contamination (mainly with aerobic sporing bacilli) to a higher equilibrium level after about 14 days occurred on uncleaned areas. Walls, even if left unwashed, acquired very few bacteria, but many were deposited locally when the wall was touched by a subject whose skin carried large numbers of staphylococci; moist exposed plaster was also heavily contaminated. Regular use of a disinfectant (‘Sudol’ 1 in 100) in cleaning a ward floor did not reduce the equilibrium level of bacteria on the floor. The transfer of staphylococci from contaminated to clean areas on the soles of shoes was demonstrated; the use of tacky and disinfectant mats did not appreciably reduce the transfer of bacteria by this route. Staphylococci deposited on a wall by a disperser were shown to be transferred from the contaminated area of wall to the hands of another subject who did not previously carry the organism; this subject was shown to transfer the staphylo-coccus to a wall which he touched. Attempts to redisperse by air movement Staph. aureus which had been shed by a disperser or by a contaminated blanket on to the floor surfaces had little effect; neither blowing with a hair dryer nor brisk exercise appeared to lift any of the staphylococci from a vinyl surface, and only small numbers were lifted by these measures from a terrazzo surface. The hazards of infection from the inanimate environment are discussed.

DECLINE OF THE HOSPITAL STAPHYLOCOCCUS?: INCIDENCE OF MULTIRESISTANT STAPH. AUREUS IN THREE BIRMINGHAM HOSPITALS

The prevalance of antibiotic-resistant strains of Staphylococcus aureus was studied in three Birmingham hospitals. In a general hospital periodic surveys showed a progressive decline in the proportions of patients with Staph. aureus in their noses which were resistant to tetracycline, erythromycin, and kanamycin. This change was associated with a progressive reduction in the use of tetracycline without an overall reduction in the use of antibiotics. There was no similar decline in resistance of staphylococci isolated in a hospital for skin diseases. In a burns unit there was a sudden large reduction during September, 1978, in the proportions of Staph, aureus from burns which were resistant to tetracycline, methicillin, cephaloridine, erythromycin, lincomycin, novobiocin, gentamicin, and kanamycin, and in the proportions of multiresistant strains (resistant to penicillin, tetracycline, erythromycin, kanamycin, methicillin, novobiocin, cephaloridine, and lincomycin). This change was associated with a reduction in the number of patients and in the use of antibiotics; tetracycline was not in use except during one month of the study. Strains of Staph. aureus resistant to these antibiotics became common again in the burns unit when a larger number of patients were admitted and more antibiotics were used in the wards.

Delayed antimicrobial effects of skin disinfection by alcohol

Aqueous suspensions of Staphylococcus aureus were deposited on a Millipore filter and then exposed for a few seconds to 70% ethyl alcohol. Viable counts of bacteria extracted from the filter immediately after exposure to alcohol, and, in replicate experiments, after a further period of 3 h, showed that the mean immediate reduction of 97.6% in viable counts after treatment with alcohol was followed by a further mean reduction of 67.1% in the further 3 h holding time; the same bacterial suspensions allowed to dry on Millipore filters without exposure to alcohol showed a significantly smaller mean reduction in viable counts (34.3%) during a further 3 h holding time. These findings support the view that the reported further fall in numbers of bacteria on hands while wearing gloves for 3 h after alcohol disinfection can be explained by sublethal damage to some of the bacteria, from which they can recover only if promptly inoculated on culture medium.

The sources of hospital infection of wounds with Clostridium welchii.

Although gas gangrene is a rare disease in peace time, the organisms responsible for the condition are widely distributed, Clostridtum welchfi in particular being found commonly in soil, faeces, dust, air, milk and various foods (Weinberg, Nativelle & Prevot, 1937; Colebrook & Cawston, 1948; Smith, 1955); C7l. wetchii often colonizes open wounds without causing gas gangrene (McLennan, 1943; Williams & Miles, 1945). This variety of habitat is of particular importance in relation to the much dreaded post-operative incidence of gas gangrene (e.g. Meleney, 1948; Sevitt, 1953). In the study reported here we have used a selective medium (Lowbury & Lilly, 1955) to obtain some quantitative data on the presence of 01. welchii in the air of operating theatres, of an air-conditioned dressing station and of other parts of the hospital. We have also examined the distribution of the organism in burns and other wounds, and obtained some evidence from these and other studies on the relative importance of self-infection and of infection from the environment.

Staphylococcal sepsis in a burns unit

An outbreak of staphylococcal sepsis in a burns unit occurred between January 1976 and May 1978. Many patients and members of staff had boils, and a number of patients also developed septicaemia. Most of the boils in the early period of the trial and a large proportion of boils in patients during the later period yielded Staphylococcus aureus resistant to penicillin, tetracycline and erythromycin only (PTE), and were shown to be of phage type 95 in the early period while strains were phage typed. From blood cultures, most strains in the early period were of resistance pattern PTE and phage type 95, but in the later period other resistance patterns were predominant. Strains from burns were usually multiresistant (PTEKNML) and of the phage pattern 29/77, which had been endemic in the Unit, but during the early period of the outbreak there was an increased proportion of strains in burns with the resistance pattern PTE and of phage type 95. Staphylococcal sepsis has for many years been very infrequent in the burns unit. This outbreak seems to have been initiated by a strain of phage type 95 and resistance pattern PTE, but during the course of the outbreak the endemic strain of type 29/77 and some other staphylococci seem to have developed enhanced ability to cause clinical infections, conceivably by transduction from the epidemic strain of phage type 95.

Evaluation of a portable air purifier

A portable air purifier significantly reduced mal odour in a small room. If the atmosphere was deliberately contaminated with Serratia marcescens the unit rapidly removed this organism. However, if incorrectly sited, the purifier could disperse organisms into the atmosphere.

CLEANING OF HOSPITAL FLOORS WITH OILED MOPS.

A comparison was made of three methods for the removal of dust from a hospital ward floor. The viable bacterial counts of impression plates from the floor showed a mean reduction of 51 % after cleaning with fresh oiled mops, 40 % after cleaning with a tank model vacuum cleaner and 5 % after sweeping with a broom. The mean proportions of airborne bacteria, compared with viable counts before cleaning, were 192 % during and 194 % after cleaning with a broom; 128 % during and 103 % after cleaning with an oiled mop, and 82 % during and 48 % after cleaning with a vacuum cleaner. On repeated use the oiled mop dispersed almost as much dust as a broom, but this settled rapidly from the air. The effects of these cleaning methods on counts of presumptive Staph. aureus on the floor and in the air were similar to those found in counts of total organisms. We wish to thank Mr M. D. Wilkins for valuable assistance, the Domestic Superintendent and staff and the nursing staff for their co-operation, and Messrs Leeming Brothers Limited for supplies of ‘Kex’ mops and equipment.

Prophylaxis against tetanus in non-immune patients with wounds: the role of antibiotics and of human antitetanus globulin.

The potential value of oral erythromycin for antitetanus prophylaxis in non-immune patients with open wounds was assessed. Serum obtained by venepuncture from health persons 2 h after an oral dose of an erythromycin preparation was used as a culture medium rendered anaerobic by addition of cooked meat. Strains of Clostridium tetani inoculated into these sera failed to multiply when the donor had taken 500 mg of erythromycin estolate before a meal; other erythromycin preparations and the estolate at a dosage of 250 mg were ineffective or inconsistent in their inhibition of the growth of Cl. tetani. Human antitetanus globulin (ATG) was given to 12 patients, 9 with severe injuries and 3 with extensive burns, all of whom were judged, from their history, to be non-immune (or with expired immunity); all except one had received large intravenous infusions of blood and/or other fluids. Serum antitoxin assays by a mouse protection technique on days 0, 1--2, 3--5, 6--10 and 14+ showed no detectable antitoxin (less than 0.01) unit/ml) in the initial (pre-ATG) sample from three patients with severe injuries and in one with extensive burns. All the patients in the severely injured group showed an early appearance or increase in tetanus antitoxin to protective titres. Two of the three severely burned patients showed, respectively, a delayed appearance or an increase in antitoxin; the other burned patients showed a reduction from the initial pre-ATG titre, followed by a return to that titre after day 5.