[Recurrent respiratory infection in children: its clinical and laboratory evaluation]

Respiratory infections comprise the main cause of medical consultations, and one of two of the first causes of morbidity and mortality in children under five in developing countries. Epidemiological studies have shown that preschool children contract between four and six respiratory infections in the course of a year without this causing any alarm as a deviation from "normality". Yet, the general practitioner and the pediatrician are frequently faced with the dilemma of deciding whether the child who is "always ill" the use of the recurrent infections is, normal or has predisposing conditions to the infections. Among the predisposing conditions for recurrent respiratory infections in children are several host factors, such as immune defense mechanisms and non-immune mechanisms as well as the infections agent and/or the environment. This article is an overview of the clinical and laboratory evaluation findings of children with recurrent respiratory infections.

Ceftizoxime disposition in neonates and infants during the first six months of life

The single-dose pharmacokinetics of ceftizoxime sodium were studied in 52 neonates and infants between 0.1 and 189 days of age. Subjects received ceftizoxime 25 or 50 mg/kg iv over 15-30 minutes. The drug was administered q8-12h for five days to permit tolerance evaluation on repetitive dosing. No differences were observed in ceftizoxime pharmacokinetic parameter estimates relative to dose. However, marked differences were observed in ceftizoxime pharmacokinetic characteristics relative to infant age; ceftizoxime half-life and mean residence time decreased, whereas body clearance increased with infant age. Ceftizoxime volume of distribution remained relatively constant over infant age. No adverse effects associated with ceftizoxime administration were observed. These data suggest that ceftizoxime 50 mg/kg q12h be used for infants less than or equal to 2 weeks of age (less than or equal to 40 weeks postconceptional age) and that 50 mg/kg q8h be administered for older infants.

[Neonatal meningitis: observations on its etiology, mortality and sequelae]

A retrospective study was carried out on all cases diagnosed with neonatal meningitis at the Hospital Infantil de México Federico Gómez. A rate of 9.6 cases per 1,000 discharged patients was found as well as 6.7% association with sepsis. In 50 of the cases analyzed, an etiologic agent was identified in 23 children; the main bacteria identified were Escherichia coli (24%), Klebsiella pneumoniae (14%), Enterobacter (4%), Proteus mirabilis and Pseudomonas sp (2%), respectively. The mortality rate was 60% and sequelae were seen in 13 of the surviving 20 patients. The unfavorable prognosis of neonates with meningitis forces us to establish an early diagnosis, make every effort to identify the causing agent and try new medications as well as co-adjuvant treatments.

[Guidelines for vaccination against measles in children]

After the introduction of massive immunization campaigns in Mexico, started in 1973, the measles mortality rate has been reduced in children under five years of age from 2.8% in 1989 to a level of 1.6% in 1985. Two epidemics occurred in 1985 and 1989 with 19,460 and 20,076 reported cases respectively. In the first quarter of 1990 a total of 22,906 cases were reported. The age distribution has been: patients greater than 1 year 26.3%; 1-4 years 24.8%; 5-14 years 35.5% and greater than 15 years 18.2%. The vaccination coverage, between 1987 and 1988, ranges from 34% to 75% in outbreaks studies and in the National Health Survey. The vaccine efficacy in those outbreaks has been estimated from 63% to 89%. The epidemics have been primary related to low vaccination coverage during the last 15 years. The conglomeration of a cumulative number of non vaccinated persons could explain the distribution of cases in all age groups. The strategy based on two doses as has been recommended in the US, is useful in programs addressed to eradicate measles, but the low resources and limited access to health services in rural communities of Mexico have made these control measures in feasible. The measles control in Mexico, must be based in vaccinate each child at the first anniversary, this strategy could be enough to take off the measles epidemics.

[Complications in children with measles]

Ongoing immunization campaigns have significantly reduced the incidence of measles. To evaluate the efficacy of vaccination policies, however, it is necessary to analyze disease indicators of mortality and of morbidity such as medical complications and sequelae. We reviewed the hospital experience at Hospital Infantil de Mexico regarding children with measles who necessitated hospitalization between January 1976 and December 1989. During this 14 year period, 176 patients with measles were hospitalized; the majority of the cases corresponded to the period between 1985 and 1989. Fifty five percent of the cases corresponded to children under one year of age. Of those older than 12 months, 81% lacked an immunization history. Eighty percent were from Mexico city or from the neighboring state of Mexico. The mayor complications included: respiratory tract infections such as pneumonia (50.8%), diarrhea (18.2%), and less frequent: laringotracheitis, otitis media, myocarditis and pyodermitis. More than 70% were significantly (grade II or III) malnourished. Twenty three patients died, for a mortality of 13%. The factors more likely related to measles mortality were; age less than two years, undernutrition, and more than two medical complications associated. This report emphasizes that medical complications and mortality are more likely to occur in very young unimmunized, malnourished children.

[Nosocomial measles: a proposal for its control in hospitals]

The transmission of measles in medical settings has become increasingly recognized. Due to the lack of information on nosocomial measles in Mexico we performed a 14 year retrospective study at the Hospital Infantil de México Federico Gómez. The objectives of our study were: a) to determine the frequency of the disease in our hospital; b) to determine the association between nutritional status and risk of acquiring nosocomial measles and c) to establish the relationship between nutritional status and complications in morbidity and mortality due to nosocomial measles. Eighty nine children with nosocomial measles were identified. We observed that patients with severe malnutrition had a greater risk of acquiring nosocomial measles developing complication and dying. The most frequent complication was pneumonia.

[Educational and research program on diagnosis and treatment of otitis media in Latin America]

Otitis media in Latin America is an important cause of hearing impairment and infectious complications which can be prevented without an inordinate effort or investment of resources. The Latin American Otitis Media Research and Training Program is a multidisciplinary, international project designed to improve the detection an treatment of otitis media in Latin America. Over 200 health care providers have already participated in pilot seminars presented in Brazil, Costa Rica, and Mexico. These sessions were highlighted by audiovisual presentations emphasizing pneumatic otoscopy. We conclude that this focused program of medical education can significantly contribute to improve primary health care in the region.

[Capacity of opsonic recognition of polymorphonuclear neutrophils in malnourished children]

The opsonic recognition capacity of polymorphonuclear neutrophils (PMNs) was evaluated in 19 noninfected children (13 eutrophic and 6 malnourished) and 22 infected children (10 eutrophic and 12 malnourished) by determining the rosette-formation capacity of the PMNs with sheep erythrocytes. After evaluating the percentage of rosette-forming neutrophils (RFN), we did not observe significant differences between the PMNs from eutrophic children and those from noninfected malnourished children (70.2 +/- 5% vs 67 +/- 3% respectively, P greater than 0.5). In contrast, the opsonic recognition capacity of PMNs from children with acute bacterial infections was significantly lower in the eutrophic (54.4 +/- 5.8%, P less than 0.05) and even more accentuated in the malnourished children (42.8 +/- 5%, P less than 0.01) when compared to the noninfected children. These results indicate that the opsonic recognition capacity of the PMNs decreases during bacterial infections. Due to the critical role of the PMNs as a mechanism of defense against infection, the greater decrease of the opsonic recognition capacity of the PMNs observed in infected malnourished children could be yet another explanation for the greater morbidity and mortality from the infectious processes observed in malnourished children.

In vitro and in vivo effects of subinhibitory concentrations of clindamycin on experimental Klebsiella pneumoniae sepsis

We studied the effect of subinhibitory doses of clindamycin on the course of experimental Klebsiella pneumoniae sepsis. Wistar rats were injected intraperitoneally with an inoculum containing 5 x 10(6) colony-forming units of K. pneumoniae resistant to clindamycin (minimum inhibitory concentration greater than 128 micrograms/ml) and then distributed to receive clindamycin 10 mg/kg/day or placebo for 10 days. All animals were bacteremic at 3 h. When the magnitude of bacteremia was compared, no difference was seen during the first 24 h; however, by 72 h the clindamycin-treated group had a significant decrease in the number of colony-forming units per milliliter blood (p less than 0.01). The mortality rate showed a tendency to decrease in the treated group (0%) as compared with the control group (30%). By 120 h, 3 of the 9 (33%) surviving animals from the control group were still bacteremic versus 0 of 11 (0%) in the clindamycin-treated group. These results suggest that subinhibitory clindamycin therapy can improve bacterial clearance and survival during the course of experimental K. pneumoniae sepsis.

[Impact of infections on mortality in children with cancer]

A study of the role infections play in the death of 29 children with cancer was conducted from 1983 to 1988. An infection was the main cause of death in twelve patients and was associated with hemorrhage in nine. Five of the patients were free of infection at the time of their death. The most frequently found etiological agents found in hemocultures taken while still alive were: Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus viridans, Salmonella enteritidis, Escherichia coli, Enterobacter sp and Candida spp. A retrospective study on the role of infections in the death of children with cancer was conducted. The clinical and autopsy records of 29 children who died between 1983 and 1988 were reviewed. Infection was the main cause of death in twelve patients and was associated with hemorrhage in nine. Five of the patients were free of infection at the time of death. The most frequent etiologic agents found in blood cultures taken while still alive were: Staphylococcus epidermidis.

The in vitro effect of sulbactam on polymorphonuclear leukocyte function

The effects of sulbactam on polymorphonuclear leukocyte (PMN) chemotaxis, respiratory burst, and microbicidal activity against Staphylococcus aureus were evaluated in vitro. PMNs from normal adult volunteers were incubated with 0.5, 2, 5, 10, and 20 micrograms/ml of sulbactam for 30 min each. At concentrations of 5 and 10 micrograms/ml, sulbactam was found to enhance PMN bactericidal activity. No inhibitory effects on PMN function were noted at the concentrations of sulbactam that were tested. In addition, the in vitro inhibitory effect of ampicillin on PMN chemiluminescence was partially abrogated by the presence of sulbactam. These findings suggest that the microbicidal phagocytic response of human PMNs against S. aureus may be improved in vitro using concentrations of sulbactam that may be readily achieved with therapeutic doses of sulbactam/ampicillin.

Vitamin A supplementation improves macrophage function and bacterial clearance during experimental salmonella infection

The effects of additional but nontoxic amounts of vitamin A on susceptibility to salmonella infection was studied by comparing rates of bacterial clearance and phagocytosis. Forty-eight male Lewis rats were divided into a treatment group receiving a total of 6000 units of vitamin A palmitate weekly for 5 weeks and a control group was given an equal volume of saline. After completion of the treatment regimen, one-half from each group were infected intraperitoneally with 10(5) Salmonella typhimurium; the other half received intraperitoneal injection of saline. At this time no differences in weight gain were noted and all animals were sacrificed within 2 weeks. At 72 hr after bacterial challenge, all saline-treated control animals displayed bacteremia. Cultures of liver and splenic homogenates were positive in 89 and 100% of infected control animals vs 0 and 44% for treated animals during the first week of infection. Kupffer cell, peritoneal, and splenic macrophages of the vitamin A-treated group had greater phagocytic activity than controls as assessed by the percentage of cells ingesting yeast particles and by the number of particles ingested (phagocytic index). These results suggest that vitamin A in moderate amounts may benefit the host's response to infection by enhancing phagocytic cell function.

Antimicrobial susceptibility of selected bacterial enteropathogens in Latin America and worldwide

We conducted an in vitro susceptibility study of bacterial pathogens to various antimicrobials. Strains of Shigella, Salmonella, Escherichia coli, and Klebsiella pneumoniae collected in the 1960s, 1970s, and 1980s at the Hospital Infantil de Mexico Federico Gomez were tested against ampicillin, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, amikacin, gentamicin, and furazolidone. Over the 3-decade period, the resistance of enteropathogens to furazolidone showed the least overall increase. Klebsiella susceptibility to the aminoglycosides decreased during the same period. Worldwide reports of enteropathogenic resistance to antimicrobials are also reviewed. In comparing the results of these worldwide studies with our own, we conclude that there is a need for periodic surveillance and testing of bacterial resistance to antimicrobials.

Nutritional implications and physiologic response to pediatric diarrhea

As depicted in Figure 1 acute diarrhea causes the host to undergo a sequence of hormonal, metabolic and immunologic responses, all of which have a nutritional cost. The impact will be more significant in the debilitated or marginally nourished child. From a nutritional point of view this process of nutrient loss and redistribution has the potential for being exploited to the benefit of the host. Two treatment techniques could be used to improve the host response to infection. Nutrients which are essential for optimal immune function and which are rapidly being metabolized may be selectively replaced, while nutrients that the offending organism needs may be withdrawn or temporarily withheld. A better understanding of the physiologic response and nutritional consequences of diarrhea should permit us to further improve the outcome of this and other infectious diseases.

Newborn sepsis following antepartum group B streptococcal maternal infection in rats

Group B streptococcus is an important pathogen in man and infection due to this bacteria is responsible for significant mortality and morbidity in neonates. An animal model of neonatal infection caused by group B streptococcus that results from vertical transmission is described. Nine pregnant Sprague-Dawley rats received intraperitoneal inoculation of 10(9)-10(10) colony forming units of group B streptococcus on day 20 or 21 of gestation. Four of nine rats died following inoculation. A total of 51 pups was born to the surviving five mothers. Pups were sacrificed at 4- to 8-h intervals and cultures of blood, brain, liver, and spleen were obtained. Nineteen of 51 pups (37%) had group B streptococcus isolated from blood or tissues within the first 48 h of life. Results suggest that antepartum systemic infection in rats can result in vertical transmission of disease. This animal model can be used to further study the mechanisms of transmission of group B streptococcus and the pathogenesis and treatment of neonatal sepsis caused by this pathogen.

Assessment of the virulence factors of group B streptococci: correlation with sialic acid content

Previous studies demonstrated strain-specific differences in opsonic requirements and virulence in neonatal rats among organisms of the same serotype of group B streptococci. The present study investigated the role of sialic acid cell-surface determinants in differences in virulence. Serotype III strains resistant to opsonization by antibody-containing sera had a higher percentage of cellular sialic acid than other organisms (1.02% sialic acid for four type III resistant strains versus 0.59% for three type III sensitive strains; P less than 0.01). Neuraminidase removed up to 70% of the extractable sialic acid from serotype III strains, markedly decreased their virulence, and made them more sensitive to the effects of protective antibody. No differences in sialic acid content were detected between sensitive and resistant strains of serotype II, and neuraminidase did not significantly remove sialic acid or affect their virulence. The present studies suggest differences in the nature or mode of attachment of virulence factors between types II and III of group B streptococci.