Diagnoses of acute lower respiratory tract infections in children in Rawalpindi and Islamabad, Pakistan

Pneumococcal and Haemophilus influenzae meningitis in a children's hospital in Ethiopia: serotypes and susceptibility patterns

Streptococcus pneumoniae and Haemophilus influenzae are responsible for most pyogenic meningitis cases in children in Ethiopia. Resistance of S. pneumoniae and H. influenzae to penicillin and chloramphenicol respectively has been reported globally. Resistance has been related to specific serotypes of S. pneumoniae or to beta-lactamase-producing H. influenzae strains. This study describes the serotypes/ serogroups and susceptibility pattern of the two organisms causing meningitis in Ethiopian children. There were 120 cases of meningitis caused by S. pneumoniae (46) and H. influenzae (74) over a period of 3 years (1993-95). Nineteen children died from pneumococcal and 28 from haemophilus meningitis. Penicillin-resistant pneumococcal meningitis (4/8 = 50%) caused a greater mortality rate than penicillin-susceptible pneumococcal meningitis (15/38 = 39%). Common serotypes accounting for 76% of S. pneumoniae were type 14, 19F, 20, 1, 18 and 5; and serotypes 14, 19F and 7 (accounting for 17% of strains) showed intermediate resistance to penicillin G. 97% of the H. influenzae isolates were type b, and in only two cases beta-lactamase-producing. 72% of isolates of the S. pneumoniae we identified belong to serotypes preventable by a 9-valent vaccine. Our study highlights the possibility of resistant pyogenic meningitis in children in Ethiopia due to emerging resistant strains of S. pneumoniae and H. influenzae isolates.

The epidemiology of pneumococcal infection in children in the developing world

Pneumonia causes about three million deaths a year in young children, nearly all of which are in developing countries. Streptococcus pneumoniae (the pneumococcus) is the most important bacterial cause of pneumonia in young children and so is likely to be responsible for a high proportion of these deaths. The pneumococcus is also responsible for a substantial proportion of the 100,000-500,000 deaths that occur from meningitis in children each year. The incidence of invasive pneumococcal disease in children in the developing world is several times higher than in industrialized countries. This discrepancy may, in part, be due to socio-economic differences but genetic factors may also play a role. Children with sickle cell disease have a substantially increased risk of invasive pneumococcal infection and a search is being made for other possible genetic risk factors. Infection with human immunodeficiency virus (HIV) also predisposes to invasive pneumococcal disease and so the incidence of this disease in young children is expected to rise as increasing numbers of African and Asian children are born with a perinatally acquired HIV infection. Until recently, pneumococcal infections could be treated effectively with penicillin, a cheap and safe antibiotic. However, pneumococci that are resistant to penicillin are becoming prevalent in many countries, necessitating a change to more costly antibiotics which may be beyond the reach of the health services of poor, developing countries. The spread of antibiotic resistance has provided an added stimulus to the development of vaccines that might be able to prevent pneumococcal disease in infants. Recently developed polysaccharide-protein conjugate vaccines show promise and are now undergoing field trials. How deployment of these vaccines will influence the balance between invasive pneumococcal infections and asymptomatic nasopharyngeal carriage of pneumococci is uncertain.

Fimbria-mediated enhanced attachment of nontypeable Haemophilus influenzae to respiratory syncytial virus-infected respiratory epithelial cells

Respiratory syncytial virus (RSV) infection is known to predispose children to otitis media and sinusitis due to bacteria such as nontypeable Haemophilus influenzae (NTHI). In this study, we investigated the role of NTHI surface outer membrane protein P5-homologous fimbriae (P5-fimbriae) in attachment to RSV-exposed A549 epithelial cells. Analysis by fluorescence flow cytometry showed that a live P5-fimbriated NTHI strain (NTHIF+) attached to a higher proportion of RSV-exposed A549 cells than to control cells (mean, 68% for RSV versus 29% for control; P = 0.008), while attachment of the P5-fimbriae-deficient isogenic mutant strain (NTHIF-) was significantly lower than in control cells and rose only slightly following RSV exposure (mean, 17% for RSV versus 10% for control, P = 0.229). Attachment of NTHIF+ did not correlate with the amount of RSV antigen expressed by A549 cells. Furthermore, paraformaldehyde-fixed NTHIF+ also demonstrated an enhanced binding to RSV-exposed cells. Observations by transmission electronic microscopy showed that the mean number of bacteria attached per 100 RSV-exposed A549 cells was higher for NTHIF+ than NTHIF- (99 versus 18; P < 0.001). No intracellular bacteria were identified. UV-irradiated conditioned supernatants collected from RSV-infected A549 cultures (UV-cRSV) also enhanced the attachment of NTHIF+ to A549, suggesting the presence of a preformed soluble mediator(s) in UV-cRSV that enhances the expression of receptors for P5-fimbriae on A549 cells. In summary, RSV infection significantly enhances NTHI attachment to respiratory epithelial cells. P5-fimbria is the critical appendage of NTHI that participates in this attachment. In clinical settings, blocking of the P5-fimbria-mediated attachment of NTHIF+ by passive or active immunity may reduce the morbidity due to NTHI during RSV infection.

The rationale for population-based surveillance for Haemophilus influenzae type b meningitis

Although Haemophilus influenzae type b (Hib) conjugate vaccines have been spectacularly successful, nearly eradicating Hib disease in countries where used routinely, they are relatively expensive. In many countries the incidence of Haemophilus influenzae type b (Hib) disease is uncertain, and it is unclear whether the local burden of Hib disease warrants the costs of adding Hib vaccine to the routine immunization program. Population-based surveillance to assess the local burden of Hib disease can help decision makers with this process. Although pneumonia is more common than meningitis, surveillance for Hib meningitis and invasive disease is likely to be more feasible and efficient than surveillance for Hib pneumonia. Standardization of laboratory methods for the isolation and identification of H. influenzae from CSF specimens is essential to successful surveillance. Should a country decide to introduce Hib conjugate vaccine as a routine immunization, population-based surveillance data collected before and after the introduction of vaccine can be used to monitor its impact. Finally population-based surveillance for bacterial meningitis also can provide information on the incidence of pneumococcal and meningococcal infections and on serogroup or serotype distributions that will be important when evaluating the new vaccines for those pathogens that are being developed.

Antimicrobial resistance and clinical effectiveness of co-trimoxazole versus amoxycillin for pneumonia among children in Pakistan: randomised controlled trial. Pakistan Co-trimoxazole Study Group

BACKGROUND

Co-trimoxazole is widely used in treatment of paediatric pneumonia in developing countries, but drug resistance may decrease its effectiveness. We studied the effectiveness of co-trimoxazole compared with that of amoxycillin in pneumonia therapy, and assessed the clinical impact of co-trimoxazole resistance.

METHODS

We recruited 595 children, aged 2-59 months, with non-severe or severe pneumonia (WHO criteria) diagnosed in the outpatient wards of two urban Pakistan hospitals. Patients were randomly assigned on a 2:1 basis co-trimoxazole (n=398) or amoxycillin (n=197) in standard WHO doses and dosing schedules, and were monitored in study wards. The primary outcome was inpatient therapy failure (clinical criteria) or clinical evidence of pneumonia at outpatient follow-up examination.

FINDINGS

There were 92 (23%) therapy failures in the co-trimoxazole group and 30 (15%) in the amoxycillin group (p=0.03)-26 (13%) versus 12 (12%) among children with non-severe pneumonia (p=0.856) and 66 (33%) versus 18 (18%) among those with severe pneumonia (p=0.009). For patients with severe pneumonia, age under 1 year (p=0.056) and positive chest radiographs (p=0.005) also predicted therapy failure. There was no significant association between antimicrobial minimum inhibitory concentration and outcome among bacteraemic children treated with co-trimoxazole.

INTERPRETATION

Co-trimoxazole provided effective therapy in non-severe pneumonia. For severe, life-threatening pneumonia, however, co-trimoxazole is less likely than amoxycillin to be effective.

Nontypeable Haemophilus influenzae: pathogenesis and prevention

In this paper, we describe the ability of nontypeable Haemophilus influenzae (NTHi) to coexist with the human host and the devastating results associated with disruption of the delicate state of balanced pathogenesis, resulting in both acute and chronic respiratory tract infections. It has been seen that the strains of NTHi causing disease show a marked genetic and phenotypic diversity but that changes in the lipooligosaccharide (LOS) and protein size and antigenicity in chronically infected individuals indicate that individual strains of NTHi can remain and adapt themselves to avoid expulsion from their infective niche. The lack of reliance of NTHi on a single mechanism of attachment and its ability to interact with the host with rapid responses to its environment confirmed the success of this organism as both a colonizer and a pathogen. In vitro experiments on cell and organ cultures, combined with otitis media and pulmonary models in chinchillas, rats, and mice, have allowed investigations into individual interactions between NTHi and the mammalian host. The host-organism interaction appears to be a two-way process, with NTHi using cell surface structures to directly interact with the mammalian host and using secreted proteins and LOS to change the mammalian host in order to pave the way for colonization and invasion. Many experiments have also noted that immune system evasion through antigenic variation, secretion of enzymes and epithelial cell invasion allowed NTHi to survive for longer periods despite a specific immune response being mounted to infection. Several outer membrane proteins and LOS derivatives are discussed in relation to their efficacy in preventing pulmonary infections and otitis media in animals. General host responses with respect to age, genetic makeup, and vaccine delivery routes are considered, and a mucosal vaccine strategy is suggested.

Epidemiology of invasive pneumococcal infections in infants and young children in Metropolitan Santiago, Chile, a newly industrializing country

AIM

To study the epidemiology of invasive pneumococcal infections in infants and young children in Santiago, Chile, as a representative pediatric population in a newly industrializing country where pneumococcal conjugate vaccines may be used in the future.

METHODS

A 5-year retrospective laboratory-based review (1989 to 1993) was followed by a 3-year prospective laboratory and hospital surveillance study in two of the six health administrative areas of Santiago to detect all hospitalized cases of invasive pneumococcal disease (defined as Streptococcus pneumoniae isolated from blood, cerebrospinal fluid or another normally sterile site) among infants and children (0 to 23 months of age in the retrospective and 0 to 59 months of age in the prospective study).

RESULTS

During the 5-year retrospective survey the incidence of invasive pneumococcal disease was 90.6 cases per 10(5) infants 0 to 11 months old and 18.5 cases per 10(5) toddlers 12 to 23 months old. Similar rates (60.2 per 10(5) infants and 18.1 per 10(5) toddlers) were recorded during the 3 years of prospective surveillance. Among the 110 cases in children 0 to 59 months of age detected during the 3-year prospective surveillance, 2 clinical forms, pneumonia and meningitis, accounted for 87.2% of all cases; 13 of the 49 pneumonia patients (26%) had empyema as a complication. Notably 40 of the 110 cases (36.4%) occurred before 6 months of age (63.4% of the 63 infant cases). Serotypes 1, 14, 5 and 6B were the most prevalent. Overall 76 and 69%, respectively, of S. pneumoniae isolates were antigenic types that would be covered by the 11- or 9-valent conjugate vaccines under development.

CONCLUSIONS

Invasive pneumococcal infections in Santiago, Chile, exhibit an epidemiologic pattern intermediate between that of developing and industrialized countries. The high burden of disease in early infancy dictates that an accelerated immunization schedule (beginning in the perinatal period) or maternal immunization with pneumococcal vaccines should be explored.

Respiratory syncytial virus infection in tropical and developing countries

Little is known about the epidemiology of respiratory syncytial virus (RSV) infection in tropical and developing countries; the data currently available have been reviewed. In most studies, RSV was found to be the predominant viral cause of acute lower respiratory tract infections (ALRI) in childhood, being responsible for 27-96% of hospitalised cases (mean 65%) in which a virus was found. RSV infection is seasonal in most countries; outbreaks occur most frequently in the cold season in areas with temperate and Mediterranean climates and in the wet season in tropical countries with seasonal rainfall. The situation on islands and in areas of the inner tropics with perennial high rainfall is less clear-cut. The age group mainly affected by RSV in developing countries is children under 6 months of age (mean 39% of hospital patients with RSV). RSV-ALRI is slightly more common in boys than in girls. Very little information is available about the mortality of children infected with RSV, the frequency of bacterial co-infection, or the incidence of further wheezing after RSV. Further studies on RSV should address these questions in more detail. RSV is an important pathogen ill young children in tropical and developing countries and a frequent cause of hospital admission. Prevention of RSV infection by vaccination would have a significant impact on the incidence of ALRI in children in developing countries.

The clinical spectrum of respiratory syncytial virus disease in The Gambia

BACKGROUND

Respiratory syncytial virus (RSV) is a well-recognized cause of lower respiratory tract infections in early childhood in industrialized countries, but less is known about RSV infection in developing countries.

METHODS

Four outbreaks of RSV infection that occurred between 1993 and 1996 in The Gambia, West Africa, were studied. RSV was sought by immunofluorescent staining of nasopharyngeal aspirate samples among young children who presented with respiratory infections at three hospitals in the Western Region of the country.

RESULTS

Five hundred seventy-four children with RSV infection were identified. The median ages of children seen in 1993 through 1996 were 3, 7, 8 and 5 months, respectively. Sixty-two percent of children <6 months old were boys. Thirteen children (2.4%) had conditions considered to increase the risk of severe RSV infection. On physical examination crepitations were heard in 80% of the children admitted to hospital, whereas wheezes were heard in only 39%. Eighty (16%) children received oxygen because of hypoxemia. Nine of 255 blood cultures (3.5%) were positive: 4 Streptococcus pneumoniae; 2 Haemophilus influenzae type b; 2 Staphylococcus aureus; and 1 Enterobacter agglomerans. Thirteen children died (2.4%). During the 4 study years 90, 25, 75 and 95% of isolates typed were RSV Subgroup A, respectively.

CONCLUSIONS

RSV is a significant cause of lower respiratory tract infection in young children in The Gambia, causing epidemics of bronchiolitis. It poses a significant burden on the health system, especially through the demand for supplementary oxygen. The clinical spectrum of RSV disease in The Gambia is similar to that seen in developed countries; concomitant bacterial infections are uncommon.

Aerobic bacteria, Chlamydia trachomatis, Pneumocystis carinii and Cytomegalovirus as agents of severe pneumonia in small infants

The authors studied 58 infants hospitalized for pneumonia in a semi-intensive care unit. Age ranged from 1 complete to 6 incomplete months. The infants were sent from another hospital in 20 cases and from home in a further 38. Pulmonary involvement, which was alveolar in 46 cases and interstitial in 12, was bilateral in 31 children. The investigation was carried out prospectively on the etiological agents associated with respiratory infection to look for evidence of aerobic bacteria (blood cultures), Chlamydia trachomatis and Cytomegalovirus (serology), and Pneumocystis carinii (direct microscopy of tracheal aspirated material). The following infectious agents were diagnosed in 21 children (36.2%): Aerobic bacteria (8), Chlamydia trachomatis (5), Pneumocystis carinii (3), Cytomegalovirus (3), Cytomegalovirus and Chlamydia trachomatis (1), Aerobic bacteria and Cytomegalovirus (1). Seven cases of infection by Chlamydia trachomatis and/or Cytomegalovirus were diagnosed out of the 12 cases with pulmonary interstitial involvement.

Serum, breast milk, and infant antibody after maternal immunisation with pneumococcal vaccine

Pneumococci are a leading cause of severe bacterial disease in infants and children world wide. A possible means of protecting infants in the first few months of life is immunisation of the mother during pregnancy. We prospectively assessed pneumococcal immunisation of pregnant women to determine the amount of pneumococcal antibody transmitted to the infants in serum and milk and the half-life of the passively acquired antibody. Healthy pregnant women in Dhaka, Bangladesh, were randomised to receive pneumococcal or meningococcal vaccine with routine prenatal tetanus immunisation at 30-34 weeks of gestation. Serum and breast milk specimens from the mothers and sera from infants were collected up to 22 weeks of age and assayed for specific serum IgG, IgG1, and IgG2 and for milk IgA antibodies to pneumococcal serotypes 6B and 19F. 55 mothers and 56 infants were followed from birth to five months. Women who received pneumococcal vaccine had geometric mean antibody increases of 2.6 and 3.4 to types 6B and 19F, respectively. The mean infant/maternal antibody ratios were 0.56 and 0.59 (range 0.11-1.46) for these serotypes. Infant cord antibody titres correlated with maternal titres. Infant/maternal IgG ratios correlated with the interval between immunisation and birth and were higher for specific IgG1 than for IgG2. Infants of pneumococcal vaccine recipients had geometric mean antibody concentrations of 6.8 and 7.5 micrograms/mL to serotypes 6B and 19F in cord blood; in cord blood and in all subsequent serum specimens the concentrations were 2-3 fold higher than in control infants. The median half-life of passive antibody was about 35 days; at five months of age 63-71% of infants of pneumococcal vaccine recipients had antibody concentrations greater than 0.15 micrograms/mL. Breast milk IgA antibodies for pneumococcal serotype 19F, but not for type 6B, were significantly higher in vaccine recipients up to five months after delivery. If maternal pneumococcal polysaccharide antibodies do not interfere with active immunisation of the infant with new glycoprotein conjugate pneumococcal vaccines, passive-active immunisation of infants can be a feasible strategy for developing regions.

Respiratory syncytial virus infection: clinical presentation and management

RSV infection continues to be a major cause of morbidity and mortality throughout the world. Despite advances in the understanding of its pathogenesis, limited progress has been made in prevention and treatment of RSV infection. Based on the experiences thus far it seems that control of RSV infection will be a difficult and complex task.

Mothers' perceptions of severe pneumonia in their own children: a controlled study in Pakistan

In 1992, 320 mothers were interviewed in a Rawalpindi hospital to identify which of the signs and symptoms they saw in their own children were most consistently linked with a clinical diagnosis of pneumonia as opposed to common cold. A related goal was to determine whether mothers could correctly judge the actual presence or absence of two major pneumonia signs--fast breathing and chest indrawing. The mothers were predominantly poor and 43% were illiterate. The study sample was composed of four matched groups: (1) mothers of 80 children with pneumonia, most with severe disease, interviewed after the child was referred to the ward; (2) mothers of 80 such children interviewed in the outpatient clinic prior to any discussion of the pneumonia diagnosis; (3) mothers of 80 children with common cold; and (4) mothers of 80 'well' children. Results showed that when mothers were interviewed in the clinic, their perception that a child had fast breathing and/or chest indrawing was highly correlated with pneumonia (sensitivity 64%, specificity 90%). Mothers were even more likely to say that a child had these signs after the pneumonia diagnosis had been conveyed, suggesting that interaction with doctors influenced their views. Fast breathing was better recognized than chest indrawing, and accurate diagnosis of both signs was better among mothers having prior experience with childhood pneumonia. The data suggest that even in the absence of formal ARI education, a majority of Pakistani mothers attending hospitals in indigent areas can recognize these two signs in their own children. However, the seriousness of the signs and their connection with pneumonia should be stressed in education campaigns since a high percentage of children had chest indrawing (a late sign of severe disease) by the time they were brought to the hospital.

Mixed viral infections: detection and management

An analysis was done of the incidence and nature of mixed virus infections diagnosed in the same clinical specimen from immunocompetent patients; respiratory viruses were emphasized. Few studies have addressed mixed viral infections in any systematic fashion. The relevant studies reviewed focused on clinical relationships or diagnostic methods. Data relating to multiple infections were usually derived incidentally to the purpose of the investigations. Sixty-three percent of the reports with data on mixed infections identified them in < 5% of the total number of viral infections. Respiratory syncytial virus was the most common coinfecting virus, and respiratory syncytial virus and influenza virus were the most common virus pair identified. In considering rapid diagnostic techniques, in 87% of the reports with available data a virus was diagnosed in > 10% of specimens that were negative for the virus targeted by one method. There was no indication that mixed infections were associated with increased disease in immunocompetent patients or in certain immunocompromised patients. Immunocompromised patients, however, appeared to have a greater incidence of multiple infections. Mixed infections of single cells also occur and may have important clinical implications relative to reactivation of latent viruses and enhanced disease. The requirement for a comprehensive strategy for viral diagnosis involving multiple techniques was indicated by these findings.

Oral versus nebulized albuterol in the management of bronchiolitis in Egypt

The efficacy of albuterol in the management of infants with first-time wheezing is controversial. This double-blind, placebo-controlled trial involved 128 Egyptian infants with first-time wheezing (mean age 5.9 months) who were randomly separated into four equivalent therapy groups: nebulized albuterol, nebulized saline solution, orally administered albuterol, and orally administered placebo. The nebulized therapy groups received two treatments 30 minutes apart; the oral therapy groups received one treatment. In addition, 41 infants with recurrent wheezing comprised an open-label control group who received two albuterol nebulizations. Chest radiographs, leukocyte counts, blood culture specimens, and nasal aspirate for viral antigen detection were obtained to confirm the clinical diagnosis of viral bronchiolitis. Respiratory and heart rates, clinical score, and oxygen saturation were recorded at baseline and 30 and 60 minutes after treatment. There was no difference among the four randomized groups in any of the outcomes except for an increase in heart rate of 10 beats/min in the nebulized albuterol group compared with a decrease in heart rate of 8 beats/min in the oral placebo group. No differences in the need for additional treatment were observed. Nebulized albuterol significantly improved the clinical score and reduced the respiratory rate of those with recurrent wheezing relative to those in the randomized groups. We conclude that nebulized albuterol is effective in the treatment of infants with recurrent wheezing, but there was no demonstrable efficacy of orally administered or nebulized albuterol in relieving the respiratory distress of infants with bronchiolitis in Egypt.

A community study of the application of WHO ARI management guidelines in Pakistan

During a community-based study in four rural villages in Pakistan, 617 cases of acute respiratory infections (ARI) in children younger than 5 years of age were assessed, classified and managed according to the WHO ARI case management guidelines. Of these, 509 (82.5%) had 'cough and cold' without clinical evidence of pneumonia, 95 pneumonia, two severe pneumonia and 11 otitis media. Of the 509 without clinical evidence of pneumonia but with cough and cold, 491 (96.5%) were successfully treated without antibiotics and only 18 (3.5%) of these children needed antimicrobial therapy on follow-up. Of the 95 cases of pneumonia, 87 (91.4%) showed a satisfactory clinical response to oral cotrimoxazole and only eight (8.4%) required a change of antibiotic.