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Biomedical subjects

Amanda J Leach

Publications and source records attributed to Amanda J Leach.

9 recordsLinked to original sources
PubMed2006

Indirect effects of childhood pneumococcal vaccination on pneumococcal carriage among adults and older children in Australian Aboriginal communities.

Nasopharyngeal carriage of Streptococcus pneumoniae in unimmunised adults and older children in three remote Australian Aboriginal communities was compared in 2002 and 2004. Universal childhood pneumococcal vaccination with a catch-up program was introduced in late 2001. Carriage prevalence across all age groups of pneumococcal serotypes included in the 7-valent vaccine was 10% in both 2002 and 2004 (12 and 30 months after introduction of vaccination). This carriage prevalence was lower than anticipated. It is likely that indirect effects of childhood vaccination occurred before the 2002 survey. To further assess indirect effects on carriage of childhood pneumococcal vaccination, data prior to 2002 are required. Between 12 and 30 months following introduction of conjugate pneumococcal vaccination, indirect effects on carriage were unchanged.

Adolescent↗
PubMed2006

Measuring nasal bacterial load and its association with otitis media.

BACKGROUND: Nasal colonisation with otitis media (OM) pathogens, particularly Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, is a precursor to the onset of OM. Many children experience asymptomatic nasal carriage of these pathogens whereas others will progress to otitis media with effusion (OME) or suppurative OM. We observed a disparity in the prevalence of suppurative OM between Aboriginal children living in remote communities and non-Aboriginal children attending child-care centres; up to 60% and <1%, respectively. This could not be explained by the less dramatic difference in rates of carriage of respiratory bacterial pathogens (80% vs 50%, respectively). In this study, we measured nasal bacterial load to help explain the different propensity for suppurative OM in these two populations. METHODS: Quantitative measures (colony counts and real-time quantitative PCR) of the respiratory pathogens S. pneumoniae, H. influenzae and M. catarrhalis, and total bacterial load were analysed in nasal swabs from Aboriginal children from remote communities, and non-Aboriginal children attending urban child-care centres. RESULTS: In both populations nearly all swabs were positive for at least one of these respiratory pathogens. Using either quantification method, positive correlations between bacterial load and ear state (no OM, OME, or suppurative OM) were observed. This relationship held for single and combined bacterial respiratory pathogens, total bacterial load, and the proportion of respiratory pathogens to total bacterial load. Comparison of Aboriginal and non-Aboriginal children, all with a diagnosis of OME, demonstrated significantly higher loads of S. pneumoniae and M. catarrhalis in the Aboriginal group. The increased bacterial load despite similar clinical condition may predict persistence of middle ear effusions and progression to suppurative OM in the Aboriginal population. Our data also demonstrated the presence of PCR-detectable non-cultivable respiratory pathogens in 36% of nasal swabs. This may have implications for the pathogenesis of OM including persistence of infection despite aggressive therapies. CONCLUSION: Nasal bacterial load was significantly higher among Aboriginal children and may explain their increased risk of suppurative OM. It was also positively correlated with ear state. We believe that a reduction in bacterial load in high-risk populations may be required before dramatic reductions in OM can be achieved.

Journal Article↗
PubMed2005

Otitis media in young Aboriginal children from remote communities in Northern and Central Australia: a cross-sectional survey.

BACKGROUND: Middle ear disease (otitis media) is common and frequently severe in Australian Aboriginal children. There have not been any recent large-scale surveys using clear definitions and a standardised middle ear assessment. The aim of the study was to determine the prevalence of middle ear disease (otitis media) in a high-risk population of young Aboriginal children from remote communities in Northern and Central Australia. METHODS: 709 Aboriginal children aged 6-30 months living in 29 communities from 4 health regions participated in the study between May and November 2001. Otitis media (OM) and perforation of the tympanic membrane (TM) were diagnosed by tympanometry, pneumatic otoscopy, and video-otoscopy. We used otoscopic criteria (bulging TM or recent perforation) to diagnose acute otitis media. RESULTS: 914 children were eligible to participate in the study and 709 were assessed (78%). Otitis media affected nearly all children (91%, 95%CI 88, 94). Overall prevalence estimates adjusted for clustering by community were: 10% (95%CI 8, 12) for unilateral otitis media with effusion (OME); 31% (95%CI 27, 34) for bilateral OME; 26% (95%CI 23, 30) for acute otitis media without perforation (AOM/woP); 7% (95%CI 4, 9) for AOM with perforation (AOM/wiP); 2% (95%CI 1, 3) for dry perforation; and 15% (95%CI 11, 19) for chronic suppurative otitis media (CSOM). The perforation prevalence ranged from 0-60% between communities and from 19-33% between regions. Perforations of the tympanic membrane affected 40% of children in their first 18 months of life. These were not always persistent. CONCLUSION: Overall, 1 in every 2 children examined had otoscopic signs consistent with suppurative ear disease and 1 in 4 children had a perforated tympanic membrane. Some of the children with intact tympanic membranes had experienced a perforation that healed before the survey. In this high-risk population, high rates of tympanic perforation were associated with high rates of bulging of the tympanic membrane.

Australia↗
PubMed2005

The clinical course of acute otitis media in high-risk Australian Aboriginal children: a longitudinal study.

BACKGROUND: It is unclear why some children with acute otitis media (AOM) have poor outcomes. Our aim was to describe the clinical course of AOM and the associated bacterial nasopharyngeal colonisation in a high-risk population of Australian Aboriginal children. METHODS: We examined Aboriginal children younger than eight years who had a clinical diagnosis of AOM. Pneumatic otoscopy and video-otoscopy of the tympanic membrane (TM) and tympanometry was done every weekday if possible. We followed children for either two weeks (AOM without perforation), or three weeks (AOM with perforation), or for longer periods if the infection persisted. Nasopharyngeal swabs were taken at study entry and then weekly. RESULTS: We enrolled 31 children and conducted a total of 219 assessments. Most children had bulging of the TM or recent middle ear discharge at diagnosis. Persistent signs of suppurative OM (without ear pain) were present in most children 7 days (23/30, 77%), and 14 days (20/26, 77%) later. Episodes of AOM did not usually have a sudden onset or short duration. Six of the 14 children with fresh discharge in their ear canal had an intact or functionally intact TM. Perforation size generally remained very small (<2% of the TM). Healing followed by re-perforation was common. Ninety-three nasophyngeal swabs were taken. Most swabs cultured Streptococcus pneumoniae (82%), Haemophilus influenzae (71%), and Moraxella catarrhalis (95%); 63% of swabs cultured all three pathogens. CONCLUSION: In this high-risk population, AOM was generally painless and persistent. These infections were associated with persistent bacterial colonisation of the nasopharynx and any benefits of antibiotics were modest at best. Systematic follow up with careful examination and review of treatment are required and clinical resolution cannot be assumed.

Acute Disease↗
PubMed2002

Impact of single dose azithromycin on group A streptococci in the upper respiratory tract and skin of Aboriginal children.

BACKGROUND: Aboriginal children living in remote Australia experience high rates of bacterial infection such as trachoma, otitis media and streptococcal skin infection, which often progress to associated chronic diseases in later life. METHODS: In February, 1995, single dose azithromycin was given to 130 Aboriginal children with trachoma and their contacts. The impact of this program on respiratory and skin group A Streptococcus pyogenes carriage and infection was also monitored. RESULTS: Immediately before treatment 90% of children had skin sores, 38% of sores had pus and 74% of sores with pus had group A Streptococcus (GAS). Overall 57% of children had GAS skin infections. At 2 to 3 weeks and 2 and 6 months after treatment, this proportion was 10, 32 and 51%, respectively. For the upper respiratory tract GAS recovery rates were 8% before treatment and 0, 11 and 15% at the 2- to 3-week, 2-month and 6-month posttreatment visits, respectively. Multiple types occurred concurrently in individuals, particularly after treatment. Identical types were sometimes recovered simultaneously from the upper respiratory tract and skin, suggesting that the high rates of acute rheumatic fever in this population in the absence of high rates of detectable throat GAS carriage could be related to high rates of skin GAS infection. CONCLUSIONS: There is an urgent need for education, adequate housing, scabies eradication and improved hygiene to reduce skin trauma and subsequent GAS infection in this population. Clinical trials are needed to determine how these measures can best be integrated with the trachoma eradication program to maximize health outcomes.

Adolescent↗
PubMed2002

In vivo penicillin MIC drift to extremely high resistance in Serotype 14 Streptococcus pneumoniae persistently colonizing the nasopharynx of an infant with chronic suppurative lung disease: a case study.

This is the first report of in vivo pneumococcal penicillin MIC drift from 4.0 to 16.0 mg/liter, possibly associated with alterations in the pbp1a gene. The case presented here is of an infant with early onset recurrent pneumonia and chronic bronchitis requiring repeated antibiotics.

Bronchitis↗