Identification of airborne dissemination of epidemic multiresistant strains of Pseudomonas aeruginosa at a CF centre during a cross infection outbreak

BACKGROUND

Chronic Pseudomonas aeruginosa infection is a major cause of morbidity and mortality for individuals with cystic fibrosis (CF). P aeruginosa cross infection outbreaks have recently been reported at CF holiday camps and specialist centres. The mechanism of cross infection is unknown. A study was performed to look for the presence of epidemic strains of P aeruginosa in the environment of a CF centre during a cross infection outbreak and to examine their potential modes of spread between patients.

METHODS

Microbiological sampling of the environment of the CF facility was performed, including room air sampling. Individual P aeruginosa strains were identified by bacterial fingerprinting. The typing patterns were compared with those of epidemic strains responsible for cross infection among the patients.

RESULTS

Epidemic P aeruginosa strains were isolated from room air when patients performed spirometric tests, nebulisation, and airway clearance, but were not present in other areas of the inanimate environment of the CF centre.

CONCLUSIONS

Aerosol dissemination may be the most important factor in patient-to-patient spread of epidemic strains of P aeruginosa during recent cross infection outbreaks at adult CF centres.

Spread of a multiresistant strain of Pseudomonas aeruginosa in an adult cystic fibrosis clinic

We initiated a prospective surveillance study to investigate possible Pseudomonas aeruginosa cross-infection in our cystic fibrosis centre. We characterised isolates by pyocin typing and pulsed-field gel electrophoresis. 22 (14%) of 154 patients with chronic P aeruginosa had isolates with similar and new pyocin and pulsed-field gel electrophoresis types. The shared isolates showed unusual phenotypic features: they were non-pigmented, non-motile, and resistant to a number of antipseudomonal antibiotics. Cross-infection by a multiresistant P aeruginosa strain has therefore occurred in patients attending our cystic fibrosis centre. We recommend microbiological surveillance in other cystic fibrosis centres.

Burkholderia gladioli: recurrent abscesses in a patient with cystic fibrosis

We describe a case of an adult patient with cystic fibrosis who developed chronic pulmonary infection and multiple episodes of soft tissue abscesses with Burkholderia gladioli; this organism should be added to the list of potential pathogens for individuals with cystic fibrosis.

Electron microscopy and serological features of a patient with Q fever prosthetic valve endocarditis

The clinical, serological and electron microscopic findings in a 47 year old woman with bioprosthetic valve coxiella endocarditis occurring 15 years after streptococcal endocarditis are described. The patient underwent valvular surgery a total of four times to control symptoms and remains well on medical therapy more than two years after her last operation.

A clinical trial using co-trimoxazole in an attempt to reduce wound infection rates in dog bite wounds

One hundred and thirteen patients were entered into a randomized, prospective double-blind, placebo controlled trial to assess the use of co-trimoxazole in reducing wound infections after dog bites. Although there was a reduction in the wound infection rate from 13.8% in the placebo group to 5.5% in the treatment group this did not reach statistical significance (P = 0.135). If hand wounds are considered separately, no infections occurred in the treatment group and a benefit seems likely.

Aspergillus niger endocarditis complicating aortic tissue valve replacement

Images

Netilmicin prophylaxis in open-heart surgery

Pericardial fluid, serum and atrial appendage concentrations of netilmicin and gentamicin were determined in 80 patients who received one or two pre-operative doses of either netilmicin 200 mg im or gentamicin 120 mg im. Mean atrial appendage concentrations of netilmicin and gentamicin after a single dose were 4.8 and 2.1 mg/kg; mean serum concentrations were 6.9 and 3.9 mg/l, and mean pericardial fluid concentrations 3.8 and 2.6 mg/l, respectively. After two doses apparent sequestration of the antibiotic in pericardial fluid was observed. A review of the cases of prosthetic valve endocarditis during the last decade suggests that aminoglycoside/isoxazolyl penicillin combinations provide good anti-staphylococcal prophylaxis. A change in the pattern of infections has been observed. The incidence of staphylococcal infection has fallen; early infections may be of fungal aetiology and late infections show a similar distribution of infecting organisms to that seen in native valve endocarditis.

Pneumonectomy for drug resistant mycobacterium malmoense

Images

Aneurysm of the mitral valve complicating Streptococcus milleri endocarditis

A case of Streptococcus milleri endocarditis which caused an aneurysm of the anterior leaflet of the mitral valve is reported. There is only one previous report of a mitral valve aneurysm secondary to infective endocarditis demonstrated by angiography. Streptococcus milleri normally causes endocarditis in an older age group than the patient we describe. Some salient features of this increasingly recognized human pathogen are emphasized.

Diphtheria carriers in Manchester: simultaneous infection with toxigenic and non-toxigenic mitis strains

A toxigenic strain of Corynebacterium diphtheriae mitis was isolated from a 10-week-old baby with membranous tonsillitis, and over the next 6 months thirty-nine symptom-free carriers of nitrate-positive mitis strains were found. All carriers were cleared by 14 days' treatment with erythromycin, though several relapsed after a 5-day course. Four contacts carried both toxigenic and non-toxigenic mitis strains; epidemiological evidence and phage studies suggest that these had a common origin. These findings have implications for the epidemiology of diphtheria and for the routine testing of isolates for toxigenicity.

Inhaled corticosteroid aerosols and candidiasis

A three-month controlled study was performed to assess the cumulative incidence of oral Candida carriage and thrush in patients starting to take betamethasone valerate aerosol (800 microgram/day) for control of their asthma. Four of 41 patients on the corticosteroid aerosol developed thrush compared with none of 40 in the control group. However, the number of cumulative saliva culture positives for C. albicans rose by a similar amount (approximately 20%) in each group. A simple mouthwash procedure was shown to have no prophylactic benefit in the aerosol group. Oral candidiasis was not, however, clinically important.

Bacterial septicaemia with multiple organisms complicating influenzal pneumonia

Images

Mouse or man? Which are pertussis vaccines to protect?

Type 1 strains of Bordetella pertussis can infect mouse brain and have been recovered as type 1 organisms after death. When introduced into the naso-pharynx of the marmoset, they immediately acquired agglutinogen 2 or 3, and the resulting type 1,2 or 1,3 infection persisted for many weeks. As in the child, agglutinogens 2 and/or 3 appear to be essential for infection of the marmoset, whereas they are quite unnecessary in mouse brain. A vaccine (extract or whole cell) containing agglutinogen 1 may be sufficient to pass the mouse protection test but it may fail to immunize children. The mouse test is inadequate even for the screening of such extracts.

Variation of serotype in strains of Bordetella pertussis

The four main serotypes of Bordetella pertussis (1, 2, 3; 1, 2; 1, 3; 1) undergo spontaneous variation involving loss or gain of antigen 2 or antigen 3. By serial subculture from single colonies on charcoal-blood-agar medium, we have detected loss-mutations from type 1, 2, 3 to 1, 2 or 1, 3, and from type 1, 2 to type 1. Likewise we have found gain-mutations from type 1 to 1, 2 or 1, 3, and from 1, 2 to 1, 2, 3.These mutations apparently occur with a high frequency in some strains. Other strains have a lower mutation-rate and are more stable antigenically. We have not detected, by this method, either gain- or loss-mutations from the type 1, 3 strains that we have tested.These findings offer an explanation for the changes in serotype that occur during the course of a pertussis infection in the child and in the marmoset. They also constitute a warning on the possible antigenic instability of laboratory strains, especially relevant in the production, absorption and testing of diagnostic antisera and in the preparation of pertussis vaccine.

Experimental pertussis infection in the marmoset: type specificity of active immunity

ALTHOUGH WE HAVE FAILED TO PRODUCE EITHER PAROXYSMAL COUGH OR VOMITING IN RHESUS MONKEYS, CYNOMOLGUS MONKEYS AND MARMOSETS, WE HAVE FOUND IN MARMOSETS SEVERAL FEATURES OF PERTUSSIS INFECTION SIMILAR TO THOSE SEEN IN CHILDREN WITH WHOOPING COUGH: catarrh, persistence of colonization of the naso-pharynx with Bordetella pertussis for 4-11 weeks, change of serotype during colonization and inability of type 1 organisms to establish themselves as the predominant serotype.As in children, we have found that intramuscular vaccine of type 1,2,3 was more effective than type 1,2 in preventing persistent infection with the currently prevalent serotypes 1,2,3 and 1,3. A mixed vaccine (1,2,3 and 1,3) seemed to produce agglutinin 3 in the serum more consistently than a pure type 1,2,3 vaccine. The duration of colonization, after naso-pharyngeal challenge, was greatly reduced in animals with agglutinin 3.Local immunity, resulting from previous infection, was even more effective than a good vaccine in preventing subsequent persistent colonization. Marmosets may be useful in studying the possible development of aerosol pertussis vaccine for human use.

Efficacy of pertussis vaccines: a brighter horizon

A study of pertussis infections in 186 children under 11 years of age in the Manchester region during 1969-71 suggests that recently-manufactured vaccines have been more effective than those made before 1967. The earlier vaccines were effective mainly against the serotypes of Bordetella pertussis possessing antigen 2, while those made from 1967 are more nearly equal in their effectiveness against thedi fferent serotypes. A booster dose of the earlier vaccines did not prevent infection with type 1,3 organisms, but we obtained a positive culture from only one child who had received four doses of recent vaccine.Simultaneous infection of a child with two or more serotypes was frequently seen. The predominant serotype in a patient was usually type 1,3; less often it was type 1,2,3 or type 1,2; it was never type 1. A change of serotype sometimes occurs during the course of the illness and is probably directed by the vaccination status of the patient in relation to the serotype of the initial infection.Our findings emphasize the need for vaccines to contain adequate amounts of all three pertussis agglutinogens, and for satisfactory immunization schedules to be used in their administration.