The association between corticosteroid use (and the resulting immunosuppression) and risk of infection
with Legionella is also apparent in the large population of children with asthma who receive corticosteroid
therapy. Boldur and colleagues (1986) compared Legionella-seropositive rates among 184 asthmatic children
(ages 2-15 years) with 80 age- and sex-matched controls. The number of seropositive children (titers 1:256)
was significantly higher (p<0.001) in the asthmatic group, although no association was found between
corticosteroid treatment and antibody titer. The authors also noted that the apparent susceptibility of asthmatic
children to legionnaires’ disease may also be attributable in part to the children’s increased contact with hospital
environments and their use of respiratory equipment including medication nebulizers.
Another population that could be at particularly high risk for Legionella infection and legionnaires’
disease is neonates due to their underdeveloped lung and immune defenses, as well as the intensive medical
treatments (including ventilation assistance and humidified incubators) and corticosteroid therapy they may
receive. Only a small number of cases of legionnaires’ disease have been reported in neonates (Horie et al. 1992,
Holmberg et al. 1993, Famiglietti et al. 1997, Levy and Rubin 1998). Nevertheless, these sporadic cases have
served to bring Legionella to the attention of neonatologists and other medical personnel.
Children whose cellular immune systems have been compromised by AIDS could be at increased risk for
developing infections caused by opportunistic intracellular pathogens such as Legionella. The incidence ofpneumonia caused by Legionella, however, is extremely low in this population (Chaisson 1998, Stout and Yu
1997). This low incidence may be due in part to increased infection control vigilance when these children are
hospitalized. Another factor may be the likelihood that children with AIDS are receiving prophylactic antibiotic
treatment (e.g., trimethoprim-sulfamethoxazole) to reduce their risk of Pneumocystis carinii pneumonia, as
recommended by the American Academy of Pediatrics (1997). These antibiotics are also effective against
Legionella.
Pediatric cases of community-acquired legionnaires’ disease have also been reported in the published
literature (Stout and Yu 1997), but these cases typically entail scenarios in which both adults and children were
exposed to Legionella and a small percentage of the exposed adults and children contract legionnaires’ disease.
For example, Jernigan et al. (1996) reported an outbreak of legionnaires’ disease in adults and children that was
associated with an improperly maintained whirlpool spa filter on a cruise ship (Jernigan et al. 1996). No reports
were located concerning outbreaks that were apparently restricted to children, and the sporadic occurrence of
this disease in the community does not allow discernment of risk factors that are specific to children.
The environments in which children spend the majority of their day -- at home, in daycare, in school, or
playing outside -- have not been associated with increased risk of exposure to Legionella. While scientists have
determined that Legionella may be present in home and small building water supply systems (Straus et al.
1996), the vast majority of environmental research and available literature on Legionella has focused on this
organism’s presence in complex water systems and cooling towers of large buildings, especially hospitals. No
information was located concerning the occurrence of Legionella in association with disease outbreaks in
schools, day care centers, or recreational areas.
Certain behaviors in children (e.g., hand-to-mouth or fingers-to-eyes/nose contact, or playing in close
proximity to each other) place them at increased risk for many infectious diseases that are transmitted from
person-to-person. Because Legionella are not transmitted person-to-person as are many other bacterial and viral
agents causing pediatric pneumonia, children’s play behavior is not expected to increase their risk of exposure
to Legionella. There are no available reports that have compared the occurrence of Legionella (or the incidence
of legionnaires’ disease) in areas with poor sanitation to areas with adequate sanitation. No information was
located regarding the influence of socioeconomic factors on the risk of legionnaires’ disease, although poor
nutritional status that compromises a child’s immune defenses (e.g., severe vitamin D or zinc deficiencies) or
limitations in access to health care could influence a child’s prognosis. There was no information located
regarding the influence of a country’s economy (i.e., developed or developing) on this disease. 6. Conclusions
Considerable knowledge gaps persist in the literature with regard to potential risk factors specific to the
pediatric population. Based on the literature reviewed in this report, there appear to be no specific factors that
place children at increased risk for diseases caused by Legionella, and there is no evidence that children are
more likely to be exposed to these bacteria. It is widely agreed that Legionella have a very low virulence in the
general population, which is apparently true for children based on the very low numbers of reported cases of
legionellosis in children. There are also knowledge gaps regarding the behavior of Legionella in the
environment and inside the human body (e.g., the infective dose). Thus, the available literature does not support
a formal risk assessment on this group of microbial pathogens. However, compared to the general population,
children and infants do not appear to be an especially vulnerable population in terms of either the risk of
exposure or the risk of developing clinical disease from Legionella.
7. Research Recommendations
The available literature suggests that children and infants are not at increased risk of exposure to
Legionella or developing legionellosis; however, considerable knowledge gaps exist regarding the effects of
Legionella in this subpopulation. Research should focus on improved diagnostic testing so that we may better
understand the spectrum of pediatric disease and the risk factors associated with Legionella infection. An
additional research need is prospective studies of the incidence of legionnaires’ disease in children hospitalized
with either community-acquired pneumonia or nosocomial pneumonia.
đang được dịch, vui lòng đợi..