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Christopher H Heath

Publications and source records attributed to Christopher H Heath.

11 recordsLinked to original sources
PubMed2005

Experimental evidence for internal structure in aqueous-organic nanodroplets.

The spatial distribution of species within an aerosol droplet influences how it interacts with its environment. Despite the ubiquity of multicomponent nanodroplets in natural and technological aerosols, there are no published measurements of their internal structure. Here, we report the first experimental results for structure in aqueous organic nanodroplets based on small angle neutron scattering by high number density aerosols. For H(2)O-n-butanol droplets, fitting of the diffraction patterns confirms the picture of an aqueous core containing approximately 3 mol% alcohol covered by a shell of densely packed alcohol molecules.

Aerosols↗
PubMed2005

Legionellosis from Legionella pneumophila serogroup 13.

We describe 4 cases of Legionella pneumophila serogroup 13-associated pneumonia. These cases originate from a broad geographic range that includes Scotland, Australia, and New Zealand. L. pneumophila serogroup 13 pneumonia has a clinically diverse spectrum that ranges from relatively mild, community-acquired pneumonia to potentially fatal severe pneumonia with multisystem organ failure. All cases were confirmed by culture and direct fluorescent antibody staining or indirect immunofluorescent antibody tests. Proven or putative sources of L. pneumophila serogroup 13 infections in 2 patients included a contaminated whirlpool spa filter and river water. An environmental source was not found in the remaining 2 cases; environmental cultures yielded only other L. pneumophila serogroups or nonpneumophila Legionella species. We describe the clinical and laboratory features of L. pneumophila serogroup 13 infections. L. pneumophila serogroup 13 pneumonia is rarely reported, but it may be an underrecognized pathogenic serogroup of L. pneumophila.

Adult↗
PubMed2004

Eradication of a large outbreak of a single strain of vanB vancomycin-resistant Enterococcus faecium at a major Australian teaching hospital.

OBJECTIVE: To demonstrate that nosocomial transmission of vancomycin-resistant enterococci (VRE) can be terminated and endemicity prevented despite widespread dissemination of an epidemic strain in a large tertiary-care referral hospital. INTERVENTIONS: Two months after the index case was detected in the intensive care unit, 68 patients became either infected or colonized with an epidemic strain of vanB vancomycin-resistant Enterococcus faecium despite standard infection control procedures. The following additional interventions were then introduced to control the outbreak: (1) formation of a VRE executive group; (2) rapid laboratory identification (30 to 48 hours) using culture and polymerase chain reaction detection of vanA and vanB resistance genes; (3) mass screening of all hospitalized patients with isolation of carriers and cohorting of contacts; (4) environmental screening and increased cleaning; (5) electronic flagging of medical records of contacts; and (6) antibiotic restrictions (third-generation cephalosporins and vancomycin). RESULTS: A total of 19,658 patient and 24,396 environmental swabs were processed between July and December 2001. One hundred sixty-nine patients in 23 wards were colonized with a single strain of vanB vancomycin-resistant E. faecium. Introducing additional control measures rapidly brought the outbreak under control. Hospital-wide screening found 39 previously unidentified colonized patients, with only 7 more nonsegregated patients being detected in the next 2 months. The outbreak was terminated within 3 months at a cost of dollar 2.7 million (Australian dollars). CONCLUSION: Despite widespread dissemination of VRE in a large acute care facility, eradication was achievable by a well-resourced, coordinated, multifaceted approach and was in accordance with good clinical governance.

Cohort Studies↗
PubMed2003

Real-time automated polymerase chain reaction (PCR) to detect Candida albicans and Aspergillus fumigatus DNA in whole blood from high-risk patients.

We report the development and evaluation of a real-time PCR assay using the LightCycler instrument for the detection of C. albicans and A. fumigatus DNA in whole blood. Recently published consensus criteria for the diagnosis of invasive fungal infection (IFI) were used for all patient samples. Unique and published primer pairs were developed and assessed for sensitivity, specificity, and reproducibility to detect C. albicans and A. fumigatus DNA in samples spiked with purified DNA, and whole blood samples from 8 high-risk patients and 45 negative controls. The real-time assay demonstrated an analytical sensitivity of 10 fg of purified C. albicans and A. fumigatus DNA and was found to be specific for each species. The standardized approach was highly reproducible and detected C. albicans and A. fumigatus DNA in two patients with proven IFI and in one patient with a possible IFI. In addition, we report for the first time the use of recently published international consensus criteria for the diagnosis of IFI in the evaluation of a mildly invasive fungal diagnostic assay. Standardized clinical criteria and a more standardized approach to detect fungal DNA in less invasive patient samples, may permit a more reliable comparison of future studies. A rapid real-time detection of fungal DNA in whole blood, combined with standard clinical markers of response, may be more useful for monitoring patients at risk of developing IFI than other diagnostic methods currently available.

Aspergillosis↗
PubMed2003

Screening and electronic labelling of ward contacts of vancomycin-resistant Enterococcus faecium vanB carriers during a single-strain hospital outbreak and after discharge from hospital.

A large single-strain outbreak of vancomycin-resistant Enterococcus faecium (VREF) vanB occurred in Royal Perth Hospital from July to December 2001. When a VREF-carrying patient was discovered on a ward, all patients on the ward were screened with rectal swabs. A total of 172 patients were colonised, four with infections, but no deaths were attributable to VREF. The number of rectal swabs required to detect each carrier was recorded. On average four rectal swabs, each collected on separate days, were needed to detect more than 90 per cent of the 172 VREF carriers who were epidemiologically linked to the Royal Perth Hospital outbreak. An electronic alert system (Micro-Alert) was used to identify ward contacts of VREF carriers and enabled those who had not been screened before discharge to be followed-up and screened. Ninety-six contacts were actively followed-up in October 2001 and 32 (33.3%) were found to be VREF carriers. From 28 September 2001 to 30 April 2002, a total of 1,977 ward contacts were screened after discharge from hospital and 54 (2.73%) were found to be carrying VREF. We conclude that during single-strain outbreaks of vancomycin-resistant enterococci in hospitals, patient contacts need to be screened on more than three occasions in order to detect most of the carriers and control the outbreak. Secondly, electronic labelling and active follow-up of ward contacts of VREF carriers resulted in a significant number of carriers being detected who otherwise posed a risk of initiating further outbreaks in hospitals if they were readmitted.

Carrier State↗
PubMed2002

Prevention of tunneled hemodialysis catheter-related infections using catheter-restricted filling with gentamicin and citrate: a randomized controlled study.

Tunneled catheters are widely used for the provision of hemodialysis. Long-term catheter survival is limited by tunneled catheter-related infections (CRI). This study assesses the efficacy of catheter-restricted filling with gentamicin and citrate in preventing CRI in hemodialysis patients. A double-blind randomized study was conducted to compare heparin (5000 U/ml) with gentamicin/citrate (40 mg/ml and 3.13% citrate; ratio 2:1) as catheter-lock solutions. A total of 112 tunneled catheters in 83 patients were enrolled at the time of catheter insertion for commencement or maintenance of hemodialysis. The primary end point was CRI. Catheter malfunction, defined as blood flow rate of <200 ml/min for three consecutive dialyses and/or the use of urokinase, was also assessed as a secondary end point. Infection rates per 100 catheter-days were 0.03 in the gentamicin group versus 0.42 in the heparin group (P = 0.003). Kaplan-Meier survival analyses showed mean infection-free catheter survival of 282 d (95% CI, 272 to 293 d) in the gentamicin group versus 181 d (95% CI, 124 to 237 d) in the heparin group (log rank, 9.58; P = 0.002). Cox regression analyses showed a relative risk for infection-free catheter survival of 0.10 (95% CI, 0.01 to 0.92) in the gentamicin group when adjusted for gender, race, diabetes mellitus, catheter malfunction, and hemoglobin (P = 0.042). The incidence of catheter malfunction was not significantly different between groups. Predialysis gentamicin levels were significantly higher in patients randomized to gentamicin (gentamicin/citrate: median 2.8 mg/L [range, 0.6 to 3.5 mg/L], n = 5; heparin: median <0.2 mg/L [range <0.2 to 0.2 mg/L], n = 5; P = 0.008). Tunneled hemodialysis catheter-restricted filling with gentamicin and citrate is a highly effective strategy for prevention of CRI. Although citrate as a catheter-lock solution provides adequate anticoagulation for the interdialytic period, gentamicin levels suggest significant risk for chronic aminoglycoside exposure and associated ototoxicity. Before this technique is adopted, these preliminary observations warrant replication in future studies that will examine the efficacy and safety of lower doses of gentamicin or alternative agents with a reduced potential for toxicity.

Anti-Bacterial Agents↗
PubMedDate not supplied

Outpatient treatment of malaria in recently arrived African migrants.

OBJECTIVE: To describe the clinical features and management of African migrants recently arrived in Western Australia and subsequently diagnosed with malaria. DESIGN, PARTICIPANTS AND SETTING: Retrospective case record analysis of African migrants aged > or = 16 years with malaria referred to Royal Perth Hospital (RPH) from the WA Migrant Health Unit (MHU) between 1 March 2003 and 30 September 2005. MAIN OUTCOME MEASURES: Demographic variables; clinical and laboratory variables; Plasmodium species; antimalarial medications used and their efficacy. RESULTS: 57 (3.5%) of 1609 adult African migrants screened at the MHU were diagnosed with malaria and referred for treatment. 52 were infected with P. falciparum, two with P. ovale, one with P. malariae, and one with both P. falciparum and P. malariae; the malaria parasite could not be identified in one individual. No patients had severe malaria by World Health Organization criteria. Most patients (53/57) were treated as outpatients with oral antimalarial therapy; four patients without severe malaria were admitted to hospital for treatment and observation. Atovaquone-proguanil was the antimalarial medication most commonly used (in 52/57), and treatment was well tolerated in most patients. Post-treatment follow-up was possible in 50 patients; all 27 of those who were followed for 4 weeks or longer were cured. Cure could not be concluded in patients with shorter follow-up periods. All follow-up blood films were negative for malarial parasites. CONCLUSIONS: Outpatient treatment of malaria in recently arrived adult African migrants appeared to be safe and efficacious in our cohort.

Adolescent↗
PubMedDate not supplied

A 12-month review of peritoneal dialysis-related peritonitis in Western Australia: is empiric vancomycin still indicated for some patients?

BACKGROUND: The International Society for Peritoneal Dialysis (ISPD) guidelines recommend empiric therapy with cefazolin and ceftazidime for peritoneal dialysis (PD)-related peritonitis. Empiric cefazolin therapy may have diminishing efficacy because of emerging methicillin resistance in gram-positive bacteria (GPB). Western Australia also has large numbers of Aboriginal and isolated regional patients, where giving these antimicrobials can be impractical. OBJECTIVES: To evaluate, based on local antimicrobial resistance patterns, the feasibility of following ISPD guidelines in Western Australia and to identify any subgroups of PD peritonitis patients that may benefit from alternative empiric intraperitoneal antibiotics (e.g., vancomycin). STUDY DESIGN: Retrospective study of all PD peritonitis episodes in Western Australia from 1 February 2000 to 31 January 2001. SETTING: Three adult tertiary referral university hospitals and their PD patients in metropolitan Perth and regional Western Australia. PATIENTS: All adults on PD in Western Australia. MAIN OUTCOME MEASURE: Isolates and antibiograms were analyzed versus patient characteristics, including race and patient demographics. RESULTS: 293 patients (28% Aborigines, 32% regional patients) received PD. 145 episodes of PD peritonitis occurred during the study. The overall PD peritonitis rate was 1 episode/16 patient months, with Aborigines having 1 episode/10.5 patient months versus non-Aborigines having 1 episode/17 patient months (p < 0.001). 36% of isolates from PD peritonitis episodes were resistant to cefazolin or ceftazidime. 22% were methicillin-resistant GPB (MR-GPB) [18% coagulase-negative staphylococci (CoNS), 1.6% MR Staphylococcus aureus]; 2.5% were multidrug-resistant gram-negative bacteria (MDR-GNB); 5.7% were polymicrobial (MR-GPB and/or MDR-GNB); and 5.7% were fungal. 63% of CoNS were methicillin resistant. Non-Aboriginal patients yielded MR-GPB in 22% of isolates versus 23% in Aborigines (p = 0.9). Six of seven cases of fungal peritonitis occurred in Aboriginal patients (p < 0.001). CONCLUSIONS: In our study population the ISPD guidelines were appropriate for 64% of patients with PD peritonitis. We could not identify specific patient subgroups where empiric cefazolin use could be more effective. High proportions of MR-GPB PD peritonitis episodes, along with local factors, make empiric cefazolin unsuitable for many regional PD patients in Western Australia.

Adult↗