Zoonotic tuberculosis: on the decline

Mycobacterium bovis is a zoonotic member of the Mycobacterium tuberculosis complex responsible for a clinical syndrome indistinguishable from that due to M. tuberculosis. In Australia, infection with M. bovis has historically been associated with employment in the livestock industry or immigration from countries in which animal disease is endemic. It currently accounts for 0.2% of all human cases of tuberculosis within Australia. This paper describes a case of pulmonary M. bovis in a butcher and reviews factors responsible for the declining incidence of this disease in Australia.

Melioidosis in northern Australia, 2001-02

Melioidosis, caused by the gram negative bacterium Burkholderia pseudomallei, is endemic in northern Australia. Using data collated from centres in Western Australia, the Northern Territory and Queensland, this report describes the epidemiology of this disease between 1 November, 2001 and 31 October, 2002. There were 47 cases seen during this period with an average annual incidence of 5.8 cases per 100,000 population. In Indigenous Australians, an incidence of 25.5 cases per 100,000 population was seen. The timing and location of cases was generally correlated with rainfall across northern Australia. A case-cluster in a Queensland community was associated with post-cyclonic flooding. Risk factors included diabetes, alcohol-related problems and renal disease. Pneumonia (51%) was the most common clinical diagnosis. The mortality rate attributable to melioidosis was 21 per cent, although a number of other patients died of underlying disease. Despite improvements in recognition and treatment, melioidosis is still associated with a high morbidity and mortality, particularly in Indigenous Australians.

Case report: recovery from persistent septicemic melioidosis

Septicemic melioidosis is often fatal despite treatment with antibiotics such as ceftazidime to which Burkholderia pseudomallei, the causal pathogen, is sensitive in vitro. We report a near-fatal case of septicemic melioidosis with persistent B. pseudomallei bacteremia despite intravenous ceftazidime in which combination therapy with meropenem and ciprofloxacin, splenectomy and correction of metabolic acidosis allowed for hospital discharge. The choice of antibiotic agents was supported by intracellular minimum inhibitory concentration analysis using B. pseudomallei co-culture in Acanthamoeba trophozoites. The patient's B. pseudomallei isolates were indistinguishable by pulsed-field gel electrophoresis from clinical and environmental isolates previously analyzed during investigation of a Western Australian melioidosis outbreak. A combination of antibiotics known to possess intracellular activity against B. pseudomallei, surgery and supportive critical care may provide a means of improving the probability of survival in persistent septicemic melioidosis.

Molecular epidemiology of Scedosporium apiospermum infection determined by PCR amplification of ribosomal intergenic spacer sequences in patients with chronic lung disease

Respiratory tract colonization with Scedosporium apiospermum in patients with chronic suppurative lung disease is a significant concern for lung transplantation candidates, since Scedosporium infections occurring posttransplantation are usually untreatable. Up to 10% of patients with cystic fibrosis attending our respiratory medicine unit have had Scedosporium organisms isolated from sputum samples. We therefore developed a molecular typing method to examine these isolates. Typing by PCR amplification of ribosomal intergenic spacer sequences demonstrated 20 different types from 52 isolates collected from the respiratory medicine unit and elsewhere in Australia. A single common type was isolated from 11 respiratory medicine unit inpatients. Two other types were isolated from more than one source: one from two respiratory medicine unit inpatients and one from two epidemiologically linked nonhuman sources. Multiple isolates were obtained from nine patients. This method demonstrated persistent carriage of isolates of the same type in one patient for 7 months. Two patients showed carriage of isolates with multiple typing patterns within a 3-month period. The high rate of isolation and the predominance of isolates with a single typing pattern from respiratory medicine unit patients may suggest transmission to patients from a source in the unit. There was no epidemiological evidence of direct patient-to-patient spread, and Scedosporium organisms were not isolated from dust, soil, or air samples from the unit. The source and route of transmission have yet to be determined.

Interaction between Burkholderia pseudomallei and Acanthamoeba species results in coiling phagocytosis, endamebic bacterial survival, and escape

Burkholderia pseudomallei causes melioidosis, a potentially fatal disease whose clinical outcomes include rapid-onset septicemia and relapsing and delayed-onset infections. Like other facultative intracellular bacterial pathogens, B. pseudomallei is capable of survival in human phagocytic cells, but unlike mycobacteria, Listeria monocytogenes, and Salmonella serovar Typhimurium, the species has not been reported to survive as an endosymbiont in free-living amebae. We investigated the consequences of exposing Acanthamoeba astronyxis, A. castellani, and A. polyphaga to B. pseudomallei NCTC 10276 in a series of coculture experiments. Bacterial endocytosis was observed in all three Acanthamoeba species. A more extensive range of cellular interactions including bacterial adhesion, incorporation into amebic vacuoles, and separation was observed with A. astronyxis in timed coculture experiments. Amebic trophozoites containing motile intravacuolar bacilli were found throughout 72 h of coculture. Confocal microscopy was used to confirm the intracellular location of endamebic B. pseudomallei cells. Transmission electron microscopy of coculture preparations revealed clusters of intact bacilli in membrane-lined vesicles inside the trophozoite cytoplasm; 5 x 10(2) CFU of bacteria per ml were recovered from lysed amebic trophozoites after 60 min of coculture. Demonstration of an interaction between B. pseudomallei and free-living acanthamebae in vitro raises the possibility that a similar interaction in vivo might affect environmental survival of B. pseudomallei and subsequent human exposure. Endamebic passage of B. pseudomallei warrants further investigation as a potential in vitro model of intracellular B. pseudomallei infection.

Burkholderia pseudomallei traced to water treatment plant in Australia

Burkholderia pseudomallei was isolated from environmental specimens 1 year after an outbreak of acute melioidosis in a remote coastal community in northwestern Australia. B. pseudomallei was isolated from a water storage tank and from spray formed in a pH-raising aerator unit. Pulsed-field gel electrophoresis confirmed the aerator and storage tank isolates were identical to the outbreak strain, WKo97.

Acute melioidosis outbreak in Western Australia

A cluster of acute melioidosis cases occurred in a remote, coastal community in tropical Western Australia. Molecular typing of Burkholderia pseudomallei isolates from culture-confirmed cases and suspected environmental sources by pulsed-field gel electrophoresis (PFGE) of XbaI chromosomal DNA digests showed that a single PFGE type was responsible for five cases of acute infection in a community of around 300 during a 5 week period. This temporal and geographical clustering of acute melioidosis cases provided a unique opportunity to investigate the environmental factors contributing to this disease. B. pseudomallei isolated from a domestic tap at the home of an asymptomatic seroconverter was indistinguishable by PFGE. Possible contributing environmental factors included an unusually acid communal water supply, unrecordable chlorine levels during the probable exposure period, a nearby earth tremor, and gusting winds during the installation of new water and electricity supplies. The possible role of the potable water supply as a source of B. pseudomallei was investigated further.

Dissemination of respiratory secretions during tracheal tube suctioning in an intensive care unit

Most intensive care patients require frequent tracheal toilet, a procedure usually performed by suctioning the tracheal tube. Such procedures often result in the production and dissemination of droplets. We measured the distance visible droplets disseminated during tracheal tube suctioning of patients in an adult surgical intensive care unit. Fifty consecutive suction procedures in 14 patients intubated with a cuffed tracheal tube were investigated. Visible droplets were scattered over a mean distance of 60 +/- 39 cm (range 25 to 168 cm) from the tracheal tube. Blood agar culture plates were placed at three fixed points from the tracheal tube to identify organisms resulting from environmental contamination (control plates). This was repeated during suctioning procedures (study plates) to look into the occurrence of bacteriological cultures that differ from the control plates. Nine of the 14 patients had tracheal tube aspirate cultures done as part of their work-up for sepsis. In more than 30% of the suctioning procedures on these 9 patients, study plates grew bacteria that were similar to those present in their tracheal tube aspirates. In view of these observations, greater care should be taken to avoid contamination of the patient's immediate environment during tracheal tube suctioning and in the design of the intensive care unit.

Potential misidentification of Burkholderia pseudomallei by API 20NE

Biochemical confirmation of the identity of Burkholderia pseudomallei in Singapore previously relied on the API 20NE panel of tests. After introducing an alternative proprietary biochemical panel, the Microbact 24E (MedVet, Adelaide, Australia), we noted that the API panel identified some presumptive B. pseudomallei isolates as other species. We therefore compared the performance of the API 20NE against the Microbact 24E with 50 distinct clinical isolates of B. pseudomallei, after 24 hours and after five days incubation of primary cultures. The API panel correctly identified 40 isolates. Four results were unacceptable or uninterpretable. Six isolates were misidentified as other species; the commonest being Chromobacterium violaceum. One of these was again identified as C. violaceum by the repeat API panel. Fourteen isolates, including the six misidentified isolates and four isolate pairs from separate sources in four separate patients, were typed using PCR amplification of repetitive extragenic palindromic sequences (REPS). The isolates identified as C. violaceum appeared to have identical REPS patterns, suggesting that some of the errant API results may be due to a single locally prevalent strain of B. pseudomallei. A previous suggestion that C. violaceum may produce a melioidosis-like illness may therefore be due to laboratory misidentification of B. pseudomallei with the API 20NE biochemical test panel.

Endogenous source of bacteria in tracheal tube and proximal ventilator breathing system in intensive care patients

Although bacteria from both the ventilator breathing system and the gastrointestinal tract have been implicated in the pathogenesis of ventilator-associated pneumonia, an endogenous source of bacteria in the proximal respiratory breathing system has yet to be demonstrated conclusively. We investigated a potential route of bacterial colonization from the stomach contents to the efferent limb of the ventilator breathing system by bacterial culture of daily specimens from six sites in 20 surgical intensive care patients. Gram-negative bacilli were isolated in a progressively increasing proportion of samples at successive sampling points, consistent with an endogenous-to-external route of spread (patients, chi-square = 14.12, P < 0.02; samples, chi-square = 106.15, P < 0.001). Identical strains of gram-negative bacilli, confirmed by REPS typing, were found at two or more sites in seven patients. In all seven, gram-negative bacilli were first isolated from a site in the patient. In none of the 20 patients was there evidence of a sequence of colonization from the ventilator tubing or Y-piece connector towards the patient. Probable colonization sequences plotted from the time of first isolation supported the proposed sequence in six patients, and in five began with the stomach contents. Isolation sequences contrary to the proposed direction of colonization involved four bacterial species and two patients, and did not extend beyond two sample sites. These findings imply that the retrograde route of bacterial colonization of the ventilated lung extends into the proximal respiratory breathing system and may help to identify additional targets for preventive intervention.

Fungal colonisation in digital silicone rubber prostheses

The fungal discolouration of silicone rubber prostheses is reported in four cases. In two of the cases, the discolouration was caused by the fungus Candida tropicalis. In the other two cases, two different fungal organisms, namely Trichoderma sp. and Scedosporium prolificans were incriminated. The non-porous silicone rubber layers create an enclosed environment in the suction cup of the prosthesis and preclude ventilation at the prosthesis-stump interface. The moisture as a result of sweat and body warmth in the stump assists fungal growth. Residual salts from the sweat, sebum from sebaceous glands and the residues from petroleum jelly (Vaseline) applied to facilitate donning, can adhere to the surfaces of the prosthesis and provide the nutrients for fungal growth. Prolonged continuous usages of the prosthesis, the presence of sweaty palms in the users, donning the prosthesis during manual physical activities which induce perspiration, washing of hands with the prosthesis on and warm humid climatic conditions have been identified as factors predisposing the prosthesis to fungal colonisation. The fungal growth caused a black discolouration and marred the aesthetic quality of the prostheses. As a preventative measure, daily immersion of the prostheses in denture cleaner such as benzalkonium chloride, or water at 60 degrees C for 15 minutes, or decontamination with 70% alcohol is recommended. Prior cleaning to remove organic matter before decontamination is emphasised.

Rapid genotypic confirmation of methicillin resistance

Detection of phenotypic methicillin resistance in Staphylococcus aureus clinical strains by conventional disk diffusion testing is fraught with problems. We used gene amplification of the mecA locus by polymerase chain reaction (PCR), in conjunction with a capillary/air thermal cycler, to overcome both the inaccuracy of phenotypic methods and the lengthy processing times required for previous genotypic methods. The rapid PCR method correctly identified methicillin resistance in a consecutive series of 30 S. aureus isolates when compared with routine and reference phenotypic methods. The shorter processing time and smaller reagent volumes required for the air thermal cycler make same-day determination of methicillin resistance in clinical isolates feasible for diagnostic laboratories.

Teaching microbiology with hypertext: first steps towards a virtual textbook

Computer-assisted learning materials for medical microbiology were developed using hypertext-authoring software (Folio 3.1). Two versions of a text-only introductory tutorial (detailed, read only, and read-write noteform) were then evaluated in a prospective, randomized trial. Evaluation was by pre- and post-exposure multiple choice questions, and by self-administered questionnaire. There was a small difference in outcome between the two groups; the read-write group scoring higher, and students who used either software performed better than those who did not (P = 0.014). Responses to the post-test questionnaires showed that many students regarded the read-only software as an electronic handout, more frequent users requesting the addition of illustrations, self-assessment questions, and greater interactivity. A small group of students made use of the read-write version of the tutorial as a 'virtual textbook' by adding extra material to the starter file. Our experience suggests that the low-cost option of text-only hypermedia produces only modest learning gains for medical undergraduates.

Structural features of tracheal tube biofilm formed during prolonged mechanical ventilation

The dissemination of tracheal tube biofilm into the mechanically ventilated lung has been proposed as a contributory factor in the pathogenesis of ventilator-associated pneumonia. In the present study, conventional light microscopy, confocal laser scanning microscopy, and scanning electron microscopy were used to examine luminal tracheal tube biofilm in tubes from ten consecutive medical intensive care patients. Biofilms also were cultured. No tube contained a predominantly microbial aggregate. Microorganisms were either dispersed throughout the biofilm or restricted to the most superficial layer. Neutrophil polymorphonuclear cells were present in all biofilms in a pattern suggesting that a layering or stratification had taken place. The distribution of neutrophils and microorganisms was consistent with a progressive accretion of respiratory secretions, rather than formation of a predominantly microbial biofilm.

New insights into the pathogenesis of ventilator-associated pneumonia

Colonization of the lower respiratory tract of critically ill patients with Gram-negative bacilli is an early stage in the pathogenesis of ventilator-associated pneumonia. Recent studies have emphasized the endogenous source of these bacteria and have pointed to the upper gastrointestinal tract as a major source. Gastric bacterial overgrowth is known to be promoted by raised intragastric pH. Further evidence suggests that duodenal reflux is just as important in gastric bacterial overgrowth and subsequent colonization of the mechanically ventilated lung. Work on the biomaterials lining the inside of the tracheal tube in critically ill patients has shown that this biofilm can be scattered many centimetres as a result of ventilator gasflow. In vitro and in vivo evidence has been found to support a fluid dynamic process that results in dissemination of tracheal tube biofilm, which also contains neutrophils and their contents. The dissemination of combined bacteria, effete neutrophils and their breakdown products into already compromised lungs may explain the complexity of the clinical condition known as ventilator-associated pneumonia. It may thus be more correct to refer to the condition as 'ventilator-induced pneumonitis'.

Multiple antibiotic resistance in Klebsiella spp. and other Enterobacteriaceae isolated in Singapore

A common pattern of multiple antibiotic resistance has been noted in bacteria isolated from Singaporean patients. The resistance pattern includes: ampicillin, cefuroxime, ceftazidime and other third generation cephalosporins, aztreonam, gentamicin and other aminoglycosides. The bacterial species implicated are Klebsiellas and other members of the Enterobacteriaceae. Preliminary laboratory investigation with a disk-diffusion augmentation test suggests the presence of extended-spectrum beta-lactamases. A retrospective study of laboratory blood culture records shows a rising incidence of resistance in Klebsiella spp. since 1985. Antimicrobial susceptibility results suggest a high degree of co-transfer of aminoglycoside resistance. The high frequency of this type of multiple antibiotic resistance should result in greater caution in the selection of presumptive antibiotic therapy for septicaemia, in order to avoid treatment failure and further selection of resistant strains.

A multicentre survey of hand hygiene practice in intensive care units

A detailed survey of hand hygiene in 16 intensive care units (ICUs) in Yorkshire was undertaken with the aim of following up the results of a national survey of infection control policies and practices which had been conducted in 1990 (Inglis et al., Br J Anaesthesia 1992; 68, 216-220). The main problems associated with infection control were identified as: the limited relevance of some infection control policies to the specialist nature of intensive care, poor compliance by nurses to local infection control policies, sub-optimal hand hygiene by all healthcare professionals and a need for more effective communication of research-based infection control recommendations in the ICU. Our results suggest that hand hygiene practice in the ICU is sub-optimal as a consequence of ineffective communication of infection control recommendations, insufficient promotion and enforcement of agreed research-based infection control practices, and a deficiency in infection control education. The current methods of communicating infection control recommendations have a limited effect on compliance rates in the ICU and are not evaluated adequately. Recommendations for further development in this field are to prioritise surveillance of infection rates in ICUs and to feedback infection rates to intensive care staff, to identify local priorities for infection control and to introduce continuous infection control education for all healthcare professionals. Further research is required to investigate and understand why educated health professionals are not complying with recommended research-based infection control practices.

Antibacterial activity of sucralfate against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in batch and continuous culture

The antibacterial effect of varying concentrations of sucralfate was studied on Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus grown in both agitated batch and continuous culture. The minimum inhibitory concentrations estimated with the two methods were in close agreement, ranging from 5 to 15 mg sucralfate/ml, concentrations easily attainable in gastric juice after a standard adult dose. Batch culture results indicated a dose-dependent effect. This study provides further evidence for an antibacterial effect by sucralfate against a range of species associated with respiratory tract infection in ventilated patients.

Staphylococcal pneumonia in ventilated patients: a twelve-month review of cases in an intensive care unit

We reviewed staphylococcal lower respiratory tract infections in our intensive care unit over a 12-month period. Staphylococcus aureus was isolated from tracheal aspirates more commonly in patients with intracranial trauma (P < 0.001), between one and six days (mean = 3) after admission to the intensive care unit. Bacteriophage typing of all S. aureus lower respiratory tract isolates from the 17 patients with head injury did not provide evidence for a common external source of infection or patient-to-patient transmission.

Penetration of an aerosol, produced by film atomization, through the carinal bifurcation

We have measured the size of spots produced by atomization of simulated biofilm particles from a tracheal tube. Draughtsman's ink was atomized from 8.5-mm i.d. Portex tracheal tubes, using an airflow of 1 litre s-1, and trapped on vertical acetate sheets. The spots produced by these particles were compared with the spot size after entrainment and dissemination from an ink-lined tracheal tube through a bifurcating tracheobronchial tube towards a glass plate. Spot dimensions were measured by computer-assisted image analysis of a video image. The smallest particles observed on the acetate sheets were 4-17 microns in size. In the bifurcating tube experiment, large particles were deposited around the carinal bifurcation, but smaller particles traversed the bend. The smallest spot size observed (7 microns minimum; 17 microns median) corresponds to particles small enough to penetrate further into the lower respiratory tract. Travel via a tube similar to the carinal bifurcation suggests that fragments of biofilm entrained in the tracheal tube could be propelled deeper into the respiratory tract during the inspiratory phase of mechanical ventilation.

Gastroduodenal dysfunction and bacterial colonisation of the ventilated lung

The source of ventilator-associated pneumonia (gastric or oropharyngeal flora) remains controversial. We investigated the source of bacterial colonisation of the ventilated lung in 100 consecutive intensive-care patients. Gram-negative bacilli were isolated from the lower respiratory tract in 19 patients. Bacteria isolated from the stomach contents either previously or at the same time were identical to lower respiratory isolates in 11 patients. No gram-negative oropharyngeal isolate was identical to a lower respiratory tract isolate. Gastric bacterial overgrowth with gram-negative bacilli was associated with the presence of bilirubin in the stomach contents. Detectable bilirubin was also associated with subsequent acquisition of gram-negative bacilli in the lower respiratory tract. Only 5 gastric aspirate specimens with pH < 3.5 contained gram-negative bacilli. These results establish a relation between duodenal reflux and subsequent bacterial colonisation of the lower respiratory tract. Restoration of normal gastroduodenal motility might help prevent pneumonia in intensive-care patients.

Evidence for dynamic phenomena in residual tracheal tube biofilm

It has been proposed recently that a dynamic physical process occurring in the tracheal tube might account for the dissemination of bacteria and biofilm fragments into the lungs during mechanical ventilation, and the subsequent development of ventilator-associated pneumonia. In this study of tracheal tubes from consecutive adult intensive care patients, biofilms were detected radiographically in 45 of 50 tubes, and were found at the lower end of the tube more often than at the upper end (P < 0.005). In 37 of 50 tracheal tubes, the maximum biofilm thickness was equal to or greater than the 0.5 mm required for gas-liquid interaction in a tube with an i.d. of 8.5 mm. In 23 of 50 tubes, wave-like patterns were found. Five tubes had no biofilm inside the bevelled tip and another six showed evidence of biofilm loss for a greater distance from the tip. These observations suggest that the distribution of tracheal tube biofilm is caused at least in part by dynamic phenomena in the tracheal tube.

Gastroduodenal dysfunction as a cause of gastric bacterial overgrowth in patients undergoing mechanical ventilation of the lungs

We have studied 15 patients undergoing mechanical ventilation of the lungs for evidence of a relationship between gastroduodenal dysfunction and gastric bacterial overgrowth. Duodenal reflux was detected by quantitative measurement of conjugated bilirubin in gastric aspirate specimens. The pH and bacterial content of these specimens were analysed. A minority of specimens with pH less than 3.5 contained measurable numbers of viable bacteria. The total bacterial count and the count of Gram negative bacteria correlated significantly with specimen pH in both cases (P less than 0.001, in both). In the 72 specimens of gastric aspirate with pH greater than 3.5, the presence of Gram negative bacteria was associated significantly with detectable bilirubin (P less than 0.001). The total bacterial count was greater also in specimens containing bilirubin (P = 0.009). These results suggest that gastroduodenal dysfunction may promote gastric bacterial overgrowth, contributing to the development of ventilator-associated pneumonia.

Infection control in intensive care units: U.K. national survey

A completed questionnaire was returned by 246 (85%) intensive care units participating in a national survey of infection control practice in intensive care. Thirty-three units had no provision for isolating patients in single side wards. Sixty percent of responding ICU had fewer than one washbasin per bedspace. Several units reported using ventilator filters or tubing more frequently than is currently recommended. Excessive numbers of catheter urine specimens were sent for laboratory examination by some units. A small number of units used open urinary drainage systems. A significant proportion of ICU had no formally recognized policy on the management of intravascular cannulae. Only 8% of ICU in the U.K. were using a selective decontamination regimen, and nine of these (50%) had no full time consultant microbiologist available to supervise the recommended microbiological management. The majority of ICU received a regular visit (greater than or equal to one per week) from a microbiologist. Proposals are made on the development of a specialized infection control service in order to reduce the risk of nosocomial infection in intensive care, and to improve on existing resource management.

Postoperative autologous transfusion in cardiac surgery. A prospective, randomised study

To investigate the safety and efficacy of postoperative autologous blood transfusion (AT) using the Shiley hardshell venous reservoir, a prospective, randomised, controlled study was carried out in two matched groups of twenty patients undergoing elective coronary artery bypass surgery. The mean volume of shed mediastinal blood reinfused in the first 6 h postoperatively was 371.7 +/- 63.23 ml. Use of homologous blood was reduced from 760.5 +/- 108.37 ml in the control patients to 466.25 +/- 87.44 ml in the AT patients, a reduction of 38.7% (p less than 0.05). There was no statistically significant difference in the clinical outcome, overall blood loss, use of platelets, fresh frozen plasma and colloids, haematological indices, renal and hepatic functions, or clotting mechanism, although there was a reduction in the fibrinogen level in the patients who received AT (p less than 0.05). Mediastinal blood did not clot and was defibrinogenated. It contained significant levels of haemoglobin (8.175 +/- 0.506 g/dl), platelets (96.55 +/- 10.39 per mm3 10(3)), protein (42.5 +/- 1.13 g/l), calcium (2.385 +/- 0.054 mmol/l) and was well oxygenated (PO2 = 20.46 +/- 0.81 kPa). No patients developed bacteraemia or had any AT-related infections. We conclude that postoperative autologous transfusion using the Shiley hardshell venous reservoir is a safe and efficient method for reducing postoperative homologous blood requirement after coronary artery bypass surgery.

Tracheal tube biofilm as a source of bacterial colonization of the lung

Biofilm formation in tracheal tubes, its bacterial content, and its interaction with ventilator gas flow were investigated. At least 50 mg (dry weight) of biofilm was found in 30 of 40 tracheal tubes used in intensive care patients for 2 h to 10 days. Electron microscopy showed bacteria in this layer, and quantitative studies showed that bacterial counts could reach up to 10(6)/cm of tube length. Bacteria were cultured from the patient side of 18 of 78 heat and moisture exchanger-microbiological filter units removed from ventilator circuits. Particles were shown to detach from tracheal tube luminal biofilm and were projected up to 45 cm from the tracheal tube tip. Following contamination of the tracheal tube biofilm with a patient's own gastrointestinal flora, entrainment of bacteria in the inspiratory gas flow provides a mechanism for initial and repeated lung colonization.

Cialit preserved cartilage: failure to guarantee sterility

Homograft cartilage preserved in Cialit solution became contaminated with Pseudomonas fluorescens, making it unsuitable for reconstructive surgery. Cialit solution has no virucidal activity, and the risk of viral infections such as AIDS and hepatitis is a further reason not to use it as a storage solution for cartilage.

Properties of methicillin-resistant Staphylococcus aureus colonizing patients in a burns unit

One hundred cultures of methicillin-resistant Staphylococcus aureus (MRSA) were isolated from patients in a Regional Burns Unit between December 1984 and May 1985. These organisms produced large amounts of beta-lactamase which readily hydrolyzed flucloxacillin but they were sensitive to teicoplanin, dicloxacillin and cephalothin at 37.5 degrees C. The MRSA strains did not differ from methicillin-sensitive isolates in sensitivity to unsaturated fatty acids, survival in serum and plasma or desiccation. However, each culture of this strain was negative or only weakly-positive for bound coagulase and cell bound protein A. Few (eight out of 44) cultures contained plasmids and the resistance to four antibacterials was not transferable in mixed cultures. No attempt was made to isolate patients colonized with MRSA which were rarely isolated elsewhere in the hospital.