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| Journal of the New Zealand Medical Association,
23-April-2004, Vol 117 No 1192
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Skin infections of the limbs of Polynesian children
Florian Finger, Melissa Rossaak, Richard Umstaetter, Udo
Reulbach, and Rocco Pitto
Soft tissue infections, and particularly infections of the
skin, are a well-known problem in the South Pacific
area.7 Polynesian children are prone to
bacterial infections, but little is known about the epidemiology of cellulitis
and cutaneous abscess of the limbs in this high-risk
population.1 Cellulitis is a diffuse spreading
infection of the skin involving deeper tissues than erysipelas
3—and characterised by pain, erythema,
swelling, and heat. Severe forms of skin infections can be limb- or even life
threatening.9 Infection may start from
superficial lesions of the skin providing a portal of entry, but in some
patients the cause remains unidentified. The most common causative pathogens are
Staphylococcus aureus and group A
streptococci.2,4,9
Common complications of soft-tissue infections are
bacteraemia, lymphangitis, local abscess formation (or superinfection) with
Gram-negative or gas-forming organisms, necrotising fasciitis, myonecrosis, and
osteomyelitis2,3,11
The objective of this retrospective audit was to calculate
the incidence and the relative risk of skin infections among Polynesian children
versus children of European origin.
MethodsIn this study, all children
aged from 1 to 14 years, and with a soft-tissue infection requiring inpatient
treatment at Middlemore Hospital in the period between 1 January.2000 and 31
December.2000 were included—and reviewed using the Plato® computerised
audit system.
The following data was recorded for each patient
involved: age, gender, ethnic group, and duration of hospital stay. The
following diagnoses (listed in International Classification of Diagnoses
[ICD]10) were used for selection: cellulitis of face (L03.2), cellulitis of
lower limb (L03.10), cellulitis of toe (L03.0), cellulitis of upper limb
(L03.10), cutaneous abscess (L02.0-L02.9), and local infection of skin (L08.8).
Fever
(>37.5ºC), white blood cell
count (WBC), serial erythrocyte sedimentation rate (ESRs), and C-reactive
protein (CRP) were recorded from all patients. In addition, diagnostic specimens
for laboratory evaluation included swab samples from wounds and aspirates.
Tissue specimens were Gram-stained.
The method of treatment was noted either as
conservative or surgical. The surgical procedure included incision and drainage
with washout. Demographic and epidemiological data of the population under the
care of our institution were obtained from the Health Profile of Counties
Manukau, Auckland.12
For statistical evaluation, current software was used
to calculate baseline data (SAS 8.02, SAS Institute Inc., Cary, NC, USA). The
relative risk interval has been calculated using the Mantel and Haenszel-Method,
with asymptotic 95% confidence interval.
ResultsNinety-one cases of skin infection
in 91 children were recorded. The most common diagnosis was cutaneous abscess,
and the most common site of infection was the lower limb (Table 1). Fifty-three
of 91 cases (58.2%) were diagnosed with swab-samples or abscess
aspirates.
Table 1. Demographic data and diagnoses of 91 children
with skin infection
The most common causative pathogen was
Staphylococcus aureus (33 of 53 cases,
62.2%), followed by Streptococcus
pyogenes (12 of 53 cases, 22.6%). Methicillin-resistant
Staphylococcus aureus (MRSA) was
identified in 5 cases (9.4%). Gram-negative or sporing organism caused infection
in the remaining 3 cases (5.7%). In 38 cases (41.8%), antibiotic therapy was
started before admission to hospital, and the diagnosis of soft-tissue infection
was made on the basis of clinical evaluation and laboratory investigation. Fever
on admission was noted in 16 of 91 patients (17, 58%) and there were 75 of 91
cases (82, 4%) with an abnormal white blood cell (WBC) count (mean value 13, 31
x 109 cells/L). Fifty of 91 cases (54, 9%) had
a raised serial erythrocyte sedimentation rate (ESR) with a mean value of 28 mm
in 1 hour.
Only 25 of 91 patients (27,5%) were tested using C-reactive
protein (CRP)—with the mean value being 52 mg/L (range: 5 to 123 mg/L).
Forty-eight of 91 cases (52, 7%) underwent surgical treatment (incision and
drainage) followed by antibiotic therapy. In 43 cases (47, 3%), conservative
therapy was employed using antibiotics. The infection resolved uneventfully in
90 children. Osteomyelitis (requiring surgical treatment and prolonged
antibiotic therapy) occurred in 1 case (1.1%).
During the observation period, Middlemore Hospital was
responsible for the healthcare of a total of 103,900
children.12 The ratio of Polynesian children to
New Zealand European children was 1.04. During the study period, 8251 children
required inpatient treatment. 2096 of 4885 Polynesian children (42.3%) were of
New Zealand Maori ethnicity. The ratio of Polynesian children to New Zealand
European children was 1.45.
Comparison of ethnical group distribution is depicted in
Table 2. There was a statistically significant higher number of Polynesian
children suffering from cellulitis and skin abscess (73 of 91 children, p
<0.05). Thirty-eight (41.8%) of these 73 children were of New Zealand Maori
ethnicity. The estimated incidence of skin infection in the Polynesian
population was 137.7 per 100,000 (73 out of 53,000). In contrast, the estimated
incidence of infection in European children was 35.4 per 100,000 (18 out of
50,900).
Table 2. Admissions according to ethnicity of children
living in the urban and suburban area served by Middlemore Hospital
*The difference is statistically significant (p
<0.05).
The calculated relative risk (referring to the total
population of children under the healthcare of the hospital) was 3.89 (95%
confidence interval of 2.33 to 6.52, p <0.05). The calculated relative risk
(referring to the total number of children requiring in-patient treatment) was
2.79 (95% confidence interval of 1.67 to 4.67, p <0.05).
DiscussionThe aim of this study was to obtain
data regarding the incidence of skin infections in Polynesian children
(including New Zealand Maori), and to calculate the relative risk increase
versus children of other ethnicities.
Hill et al6,7 have shown
that people from Pacific Island countries frequently suffer from bacteraemia
caused by Staphylococcus aureus, and
consequently are at a higher risk of developing bone and joint infections.
Moreover, children of Polynesian ethnicity (including New Zealand Maori) show a
higher incidence of meningitis and pneumonia—the reasons remain unclear,
but it has been hypothesised that the high infection rate could be attributed to
genetic disposition. Social circumstances are also likely to be
involved.1
In the present study, the incidence of skin infection of the
limb in the Polynesian children was rated 137.7 per 100,000. In contrast, the
incidence in European children was rated 35.4 per 100,000. We calculated that
the relative risk of acquiring skin infections in Polynesian children was 3.89
times greater than European children. This value refers to the whole population
of children under the healthcare of a tertiary hospital. The calculated relative
risk increase (referring to the number of all children requiring inpatient
treatment) was 2.79. The discrepancy of the values (3.89 versus 2.79) is related
to the higher ratio of Polynesian children versus New Zealand European children
requiring inpatient treatment (ratio = 1.45:1), when compared to the ratio of
the whole population of children under the healthcare of the hospital
(ratio=1.04:1).
Two different scenarios could explain this discrepancy: i)
the general health condition of Polynesian children is poorer than that of
European-ethnicity children, and consequently they require more inpatient
treatment, and ii) some children of European ethnicity are also treated in other
hospitals. In our opinion, the reality is probably a combination of both
scenarios. From the statistical point of view, both calculated relative risk
values in this study are correct (with respect to the data they are generated
from)—ie, children with cutaneous infection versus all children requiring
inpatient treatment, or versus total children population under healthcare in one
hospital. Nevertheless, data regarding children ethnicity under hospital care
are estimated. In contrast, data of inpatient children ethnicity are
accurate.
Cutaneous abscess was the most frequent soft-tissue
infection (64%). Specifically, the lower limb appeared to be the most common
site of infection, which is supported by findings of other
authors.3-9 It can be assumed that the skin of
lower limbs is more often injured during daily life, especially the foot and
knee area, thereby providing portals of entry. In our patients, the most
frequent pathogens were Staphylococcus
aureus and Streptococcus
pyogenes; this finding is also supported by other
authors.4,9
The low rates of infection caused by Gram-negative bacteria
can be explained by the young age of the population
studied.8 Cellulitis is expected to occur more
often in association with systemic diseases like diabetes or other
immunodeficiencies.4 Surprisingly, only one
child on steroid medication was found in our patient population.
This is the first study showing (in detail) the increased
relative risk of skin infections that Polynesian children experience (versus
children of other ethnicities). However, the present study has some major
disadvantages. Firstly, this is a retrospective audit regarding a
single-hospital experience. Secondly, the observation period was too short to
pull together all potential complications following the skin infection,
particularly regarding bone and joint involvement. Thirdly, diagnosis of
infection has been given without microbiology testing in 42% of
children.
In conclusion, this study shows that there is a marked
difference in incidence and relative risk between Polynesian and European
children in how they suffer from skin infections. Further research is required
to identify whether genetic disposition or social and environmental
circumstances are involved in this
phenomenon.13
Author information:
Florian Finger, Overseas Trainee Intern; Melissa Rossaak, Registrar,
Department of Orthopaedic Surgery, Middlemore Hospital—and South Auckland
Clinical School, University of Auckland, Auckland; Richard Umstaetter,
Statistician; Udo Reulbach, Statistician, Department of Medical Informatics,
Biometry and Epidemiology, University of Erlangen, Nuremberg, Germany; Rocco
Pitto, Associate Professor, Department of Orthopaedic Surgery, Middlemore
Hospital—and South Auckland Clinical School, University of Auckland,
Auckland
Correspondence:
Associate Professor Rocco Pitto, South Auckland Clinical School, University of
Auckland, Middlemore Hospital, Private Bag 93311, Auckland. Fax: (09) 276 0288;
email: RPitto@middlemore.co.nz
References:
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