Streptococcal ecthyma. Treatment with benzathine pencillin G

Mitochondrial Genome Sequence of the Scabies Mite Provides Insight into the Genetic Diversity of Individual Scabies Infections

The scabies mite, Sarcoptes scabiei, is an obligate parasite of the skin that infects humans and other animal species, causing scabies, a contagious disease characterized by extreme itching. Scabies infections are a major health problem, particularly in remote Indigenous communities in Australia, where co-infection of epidermal scabies lesions by Group A Streptococci or Staphylococcus aureus is thought to be responsible for the high rate of rheumatic heart disease and chronic kidney disease. We collected and separately sequenced mite DNA from several pools of thousands of whole mites from a porcine model of scabies (S. scabiei var. suis) and two human patients (S. scabiei var. hominis) living in different regions of northern Australia. Our sequencing samples the mite and its metagenome, including the mite gut flora and the wound micro-environment. Here, we describe the mitochondrial genome of the scabies mite. We developed a new de novo assembly pipeline based on a bait-and-reassemble strategy, which produced a 14 kilobase mitochondrial genome sequence assembly. We also annotated 35 genes and have compared these to other Acari mites. We identified single nucleotide polymorphisms (SNPs) and used these to infer the presence of six haplogroups in our samples, Remarkably, these fall into two closely-related clades with one clade including both human and pig varieties. This supports earlier findings that only limited genetic differences may separate some human and animal varieties, and raises the possibility of cross-host infections. Finally, we used these mitochondrial haplotypes to show that the genetic diversity of individual infections is typically small with 1-3 distinct haplotypes per infestation.

Skin infection, housing and social circumstances in children living in remote Indigenous communities: testing conceptual and methodological approaches

BACKGROUND

Poor housing conditions in remote Indigenous communities in Australia are a major underlying factor in poor child health, including high rates of skin infections. The aim of this study is to test approaches to data collection, analysis and feedback for a follow-up study of the impact of housing conditions on child health.

METHODS

Participation was negotiated in three communities with community councils and individual participants. Data were collected by survey of dwelling condition, interviews, and audit health centre records of children aged under seven years. Community feedback comprised immediate report of items requiring urgent repair followed by a summary descriptive report. Multivariate models were developed to calculate adjusted incidence rate ratios (IRR) for skin infections and their association with aspects of household infrastructure.

RESULTS

There was a high level of participation in all communities. Health centre records were inadequate for audit in one community. The records of 138 children were available for development of multivariate analytic models. Rates of skin infection in dwellings that lacked functioning facilities for removing faeces or which had concrete floors may be up to twice as high as for other dwellings, and the latter association appears to be exacerbated by crowding. Younger children living in older dwellings may also be at approximately two-fold higher risk. A number of socioeconomic and socio-demographic variables also appear to be directly associated with high rates of skin infections.

CONCLUSION

The methods used in the pilot study were generally feasible, and the analytic approach provides meaningful results. The study provides some evidence that new and modern housing is contributing to a reduction in skin infections in Aboriginal children in remote communities, particularly when this housing leads to a reduction in crowding and the effective removal of human waste.

Skin infections and infestations in Aboriginal communities in northern Australia

The most important skin infections in Aboriginal communities in central and northern Australia are scabies and streptococcal pyoderma. Scabies is endemic in many remote Aboriginal communities, with prevalences in children up to 50%. The cycles of scabies transmission underlie much of the pyoderma. Up to 70% of children have skin sores, with group A streptococcus (GAS) the major pathogen. Group A streptococcus is responsible for the continuing outbreaks of post-streptococcal glomerulonephritis and acute rheumatic fever (ARF). The cycles of scabies transmission in dogs and humans do not appear to significantly overlap. Guidelines have been developed for community control of scabies and skin sores and successful community initiated coordinated programmes have occurred. The anthropophilic dermatophyte Trichophyton rubrum is ubiquitous in many communities, again reflecting living conditions. Other skin infections related to the tropical environment include melioidosis, nocardiosis, Chromobacterium violaceum and chromoblastomycosis. Sustainable and long-term improvements in scabies, skin sores and GAS-related disease and tinea require fundamental changes that address social and economic inequities and, in particular, living conditions and overcrowding.

Practical aspects of bacterial skin infections in children

Bacterial skin infections are a common reason for children to be examined by a pediatrician. Streptococci and staphylococci are responsible for the great majority of the infections. Because of the variety of lesions produced by these bacteria, there is support for dividing impetigo into "traditional" crusted and bullous forms. Two important forms of cellulitis--facial and periorbital--have potential for serious systemic consequences. The bacterial etiology and treatment of cellulitis, animal bites, and puncture wounds of the foot require special attention for successful outcome.

Necrotizing fasciitis-a disease of temperate and warm climates

Necrotizing fasciitis is a distinct clinical entity. It is usually due to Streptococcus pyogenes but may occasionally be caused by Staphylococcus aureus. It needs to be considered in relationship to other infections due to Streptococcus pyogenes, in which the clinical disease that occurs may be associated with the depth of inoculation of the coccus. Mild cases have been identified that are self-limiting as well as serious cases which would have succumbed without surgical debridement. It is likely that some cases of necrotic tropical ulcer are due to necrotizing fasciitis.

Value of desiccated swabs for streptococcal epidemiology in the field

Streptococcal surveys in foreign countries or remote areas may be greatly enhanced by the use of calcium alginate swabs desiccated in sterile silica gel. Delays of up to 4 weeks before return to a base laboratory are feasible, and the need for fresh media or laboratory facilities in the field may be eliminated. Comparison of direct plating on crystal violet blood agar versus delayed silica gel preservation during surveys in Uganda, Haiti, Colombia, and Miami, Fla., showed no significant loss of positive cultures from skin lesions and suggests that desiccated swabs increase the recovery of bacitracin-sensitive Streptococcus pyogenes (presumptive group A) from throats.