Streptococcus pneumoniae in human immunodeficiency virus type 1-infected children

Pneumococcal conjugate vaccine in HIV-infected and HIV-exposed, uninfected children

INTRODUCTION

Incidence of invasive pneumococcal disease (IPD) among HIV-infected children is 20-40 fold greater compared to HIV-uninfected children, including among HIV-infected children on antiretroviral therapy (ART). Also, HIV-exposed, uninfected children have 2.7-fold greater risk of IPD compared to HIV-unexposed children. Areas covered: We reviewed studies identified on Pubmed database with the terms 'PCV' and 'HIV'; studies involving adults only were excluded. Expert commentary: While ART and pneumococcal conjugate vaccines (PCV) have reduced IPD morbidity and mortality in HIV-infected children, ART-naïve and immunosuppressed children have inferior immunogenicity to most PCV serotypes; highlighting the need for concomitant use of ART with PCV. Furthermore, studies to determine optimal PCV dosing schedules, timing and number of doses, are urgently required to ensure sustained vaccine efficacy in HIV-infected children.

Humoral immune responses to Streptococcus pneumoniae in the setting of HIV-1 infection

Streptococcus pneumoniae (pneumococcus) remains one of the most commonly identified causes of bacterial infection in the general population, and the risk is 30-100 fold higher in HIV-infected individuals. Both innate and adaptive host immune responses to pneumococcal infection are important against pathogen invasion. Pneumococcal-specific IgA antibody (Ab) is key to control infection at the mucosal sites. Ab responses against pneumococcal infection by B cells can be generated through T cell-dependent or T cell-independent pathways. Depletion of CD4+ T cells is a hallmark of immunodeficiency in HIV infection and this defect also contributes to B cell dysfunction, which predisposes to infections such as the pneumococcus. Two pneumococcal vaccines have been demonstrated to have potential benefits for HIV-infected patients. One is a T cell dependent 13-valent pneumococcal conjugate vaccine (PCV13); the other is a T cell independent 23-valent pneumococcal polysaccharide vaccine (PPV23). However, many questions remain unknown regarding these two vaccines in the clinical setting in HIV disease. Here we review the latest research regarding B cell immune responses against pneumococcal antigens, whether derived from potentially invading pathogens or vaccinations, in the setting of HIV-1 infection.

Impact of cotrimoxazole on carriage and antibiotic resistance of Streptococcus pneumoniae and Haemophilus influenzae in HIV-infected children in Zambia

This is a substudy of a larger randomized controlled trial on HIV-infected Zambian children, which revealed that cotrimoxazole prophylaxis reduced morbidity and mortality despite a background of high cotrimoxazole resistance. The impact of cotrimoxazole on the carriage and antibiotic resistance of Streptococcus pneumoniae and Haemophilus influenzae as major causes of childhood mortality in HIV-infected children was investigated since these are unclear. Representative nasopharyngeal swabs were taken prior to randomization for 181 of 534 children (92 on cotrimoxazole and 89 on placebo). Bacterial identification and antibiotic susceptibility were performed by routine methods. Due to reduced mortality, prophylactic cotrimoxazole increased the median time from randomization to the last specimen from 48 to 56 months (P = 0.001). The carriage of H. influenzae was unaltered by cotrimoxazole. Carriage of S. pneumoniae increased slightly in both arms but was not statistically significant in the placebo arm. In S. pneumoniae switching between carriage and no carriage in consecutive pairs of samples was unaffected by cotrimoxazole (P = 0.18) with a suggestion that the probability of remaining carriage free was lower (P = 0.10). In H. influenzae cotrimoxazole decreased switching from carriage to no carriage (P = 0.02). Cotrimoxazole resistance levels were higher in postbaseline samples in the cotrimoxazole arm than in the placebo arm (S. pneumoniae, P < 0.0001; H. influenzae, P = 0.005). Cotrimoxazole decreased switching from cotrimoxazole resistance to cotrimoxazole sensitivity in S. pneumoniae (P = 0.002) and reduced the chance of H. influenzae remaining cotrimoxazole sensitive (P = 0.05). No associations were observed between the percentage of CD4 (CD4%), the change in CD4% from baseline, child age at date of specimen, child gender, or sampling month with carriage of either pathogen.

High prevalence of nasopharyngeal colonization by Staphylococcus aureus among children with HIV-1 infection in extreme southern Brazil

OBJECTIVES

To compare nasopharyngeal colonization between children with HIV-1 infection and those without HIV-1 infection, with special emphasis on nasopharyngeal carriage of Staphylococcus aureus.

METHODS

This hospital-based cross-sectional study was carried out in the Paediatric Day Hospital of a teaching hospital. Nasopharyngeal swabs were collected in 93 children aged up to 18 years old born to HIV-positive mothers (31 children with HIV-1 infection and 62 age-matched non-infected children).

RESULTS

The prevalence of nasopharyngeal colonization by S. aureus was higher among children with HIV-1 infection compared with those without HIV-1 infection (45.16% vs. 12.9%, p = 0.001). After adjusting all potential confounders, HIV-1 infection was an independent risk factor for nasopharyngeal colonization by S. aureus, with a prevalence ratio of 4.29 (95% confidence interval: 1.72-10.70).

CONCLUSION

Children with HIV-1 infection had a higher prevalence of nasopharyngeal colonization by S. aureus than children without HIV-1 infection. Most of the isolated strains of S. aureus were methicillin-susceptible.

Invasive pneumococcal disease among human immunodeficiency virus-infected children, 1989-2006

OBJECTIVE

The heptavalent pneumococcal conjugate vaccine (PCV7) has decreased the incidence of pediatric invasive pneumococcal disease (IPD) in the United States. Few data exist on the changing IPD incidence in HIV-infected children.

METHODS

Diagnostic codes and clinical microbiology laboratory records identified cases of IPD from 1989 to 2006 in perinatally-infected children <18 years of age followed at an urban HIV clinic. IPD incidence was calculated and serotype distribution and antibiotic resistance were recorded.

RESULTS

Two-hundred fifty-six patients were followed for 1756 person-years (PY). The sample was 59% female, 76% black, 14% white, and 8% Hispanic. Of 21 episodes of IPD (1200/100,000 PY), 17 (81%) were female. IPD cases had a median age of 6.3 years (interquartile range [IQR]: 2.3-9.9 years), median CD4% of 17% (IQR: 11-28%), and median CD4 count of 415 cells/mm (range, 2-1699 cells/mm). Bacteremia was the commonest form of IPD (19 episodes; 1080/100,000 PY). After HAART introduction in 1996, the incidence of IPD decreased 84% from 1862/100,000 PY in 1989-1995 to 292/100,000 PY in 1997-1999 (incidence rate ratio [IRR]: 0.16, P = 0.03). After PCV7 introduction in 2000, IPD incidence showed a nonsignificant increase from 292 of 100,000 PY in 1997-1999 to 860 of 100,000 PY in 2001-2006 (IRR: 2.94; P = 0.16). The percentages of IPD isolates nonsusceptible to penicillin and trimethoprim-sulfamethoxazole were 19% and 33%, respectively. Vaccine serotypes accounted for 38% of isolates, vaccine-related 14%, nonvaccine 33%, and the serotype was unknown in 14%.

CONCLUSIONS

The incidence of IPD among perinatally HIV-infected children decreased after the introduction of HAART. Ongoing monitoring is required to determine the effect of PCV7 on IPD in this vulnerable population.

Impact of human immunodeficiency virus infection on Streptococcus pneumoniae colonization and seroepidemiology among Zambian women

Nasopharyngeal colonization with Streptococcus pneumoniae precedes invasive pneumococcal disease. Human immunodeficiency virus (HIV) infection increases rates of invasive pneumococcal disease, and its effect on colonization is unknown. In a longitudinal cohort of Zambian mothers with or without HIV infection, HIV infection increased the risk of colonization (risk ratio [RR], 1.9; 95% confidence interval [CI], 1.3-2.8) and repeat colonization (RR, 2.4; 95% CI, 1.1-5.3) and reduced the time to new colonization (P = .01). Repeat colonization with homologous sero/factor types occurred only among HIV-positive mothers. Pediatric serotypes 6, 19, and 23 accounted for excess colonization among HIV-positive mothers. HIV infection significantly increases the risk of pneumococcal colonization. Increased rates of colonization by pediatric serotypes suggest a potential role for the 7-valent pneumococcal vaccine in HIV-infected adults.

The evidence for using conjugate vaccines to protect HIV-infected children against pneumococcal disease

Pneumococcal conjugate vaccines (PCVs) are a potentially useful complement to existing treatment strategies in HIV-infected children, for whom pneumococcal infections are common and serious. This Review summarises available data on the burden of pneumococcal disease and the safety and efficacy of PCVs in HIV-infected children. The data demonstrate that children with HIV have significantly increased risk of pneumococcal disease compared with uninfected children; the serotypes included in currently licensed or near-licensure conjugate vaccines include most serotypes that cause invasive pneumococcal disease (IPD) in HIV-infected children and adults; PCVs provide substantial protection against IPD and clinical pneumonia when given to HIV-infected infants; and HIV-infected adults gain an indirect benefit when children in the community are vaccinated. PCV should be considered as an important intervention for improving the lives of HIV-infected children.

Cellulitis in childhood invasive pneumococcal disease: a population-based study

AIM

There are few detailed data on the age-specific incidence and clinical pattern of pneumococcal cellulitis in children. We conducted a retrospective review of cellulitis as a subset of prospectively collected laboratory-identified invasive pneumococcal disease (IPD) and performed a systematic review of published literature.

METHODS

Prospective laboratory surveillance in urban regions of New South Wales, Australia, 1 June 1997-31 December 2001. Medical notes reviewed for each identified case and defined literature search strategy applied.

RESULTS

There were 1067 cases of IPD in children aged 0-17 years; 38 (3.3%) were cellulitis (32 periorbital, 6 buccal). Compared with other types of IPD, a greater proportion of cellulitis cases occur in children<2 years (30/38, 79% vs. 617/1029, 60.0%; P=0.004) in whom underlying illness was less common (0/30, 0% vs. 53/590, 9%; P=0.06). Initially, another diagnosis was made in 13 (34%) of cases; only five had a lumbar puncture, all normal. Of the 239 cases of pneumococcal cellulitis documented in the literature, 28 (11.7%) had the diagnosis made by means other than positive blood culture and 95% were facial or orbital with underlying illness (6%) and associated meningitis (1.9%) uncommon.

CONCLUSION

Cellulitis is an uncommon focus in IPD in children, and is almost always facial. Most cases occur under 2 years of age, are seldom associated with meningitis or other complications, and are frequently not recognised on admission.

Pneumonia in the long-term-care facility

Pneumonia is a common infection among residents of long-term-care facilities (LTCFs), with an incidence of 1.2 episodes per 1,000 patient-days. This rate is believed to be six- to tenfold higher than the rate of pneumonia among elderly individuals living in the community. The risk factors for pneumonia among residents of LTCFs are profound disability, bedridden state, urinary incontinence, difficulty swallowing, malnutrition, tube feedings, contractures, and use of benzodiazepines and anticholinergic medications. An elevated respiratory rate is often an early clue to pneumonia in this group of patients. Staphylococcus aureus (including methicillin-resistant S. aureus) and aerobic gram-negative bacilli (including multidrug-resistant isolates) are more frequent causes of pneumonia in this setting than in the community. Criteria have been developed that help identify patients for treatment in their LTCFs.

Failure of the conjugate pneumococcal vaccine to prevent recurrent bacteremia in a child with human immunodeficiency virus disease

Patients with advanced HIV disease have a poor response to some immunizations. A case is presented of a Class C1 HIV-infected child who suffered three episodes of Streptococcus pneumoniae serotype 6B bacteremia despite having received the heptavalent conjugate and 23-valent polysaccharide pneumococcal vaccines. Clinicians should expect some vaccine failures with the heptavalent conjugate vaccine in children with advanced HIV disease.

Colonization by Streptococcus penumoniae in human immunodeficiency virus-infected children

OBJECTIVE

Children with HIV infection are particularly susceptible to invasive pneumococcal disease, yet the effect of HIV infection and its medical management on colonization and resistance to antibiotics are poorly described. To provide a basis for medical practice, we determined the prevalence of nasopharyngeal colonization and antibiotic resistance of Streptococcus pneumoniae in children with HIV infection.

METHODS

Cross-sectional prevalence sample of children attending the pediatric HIV and pulmonary clinics to examine nasopharyngeal colonization with S. pneumoniae and antibiotic resistance to beta-lactams and trimethoprim-sulfamethoxazole (T/S). Subjects were matched by age and date of clinic visit.

RESULTS

The colonization rate with S. pneumoniae of HIV-infected and -indeterminate children was equal to that of controls (20% vs. 19%). HIV infection, CDC staging or receipt of oral antibiotic therapy did not affect colonization. Isolates from HIV-infected and -indeterminate children were less likely to be penicillin-resistant than those from controls (18% vs. 50%). There was no difference in pneumococcal resistance to T/S among isolates from subjects and controls, despite 72% T/S use in the HIV clinic.

CONCLUSION

Colonization with S. pneumoniae in HIV disease is no different from that of comparable children. The high incidence of pneumococcal disease and prophylaxis with T/S are not related to nasopharyngeal colonization. Antibiotic prophylaxis of HIV-infected children does not necessarily lead to increased resistance of S. pneumoniae.

Pneumococcal bacteremia during a decade in children in Soweto, South Africa

OBJECTIVES

To monitor for a decade the incidence and the clinical and microbiologic characteristics of pneumococcal bacteremia in children in Soweto and to assess the influence of HIV infection on any changes.

METHODS

Case records of children with pneumococcal bacteremia at Chris Hani Baragwanath Hospital from July, 1986, to June, 1987 (1986/ 1987), and from July, 1996, to June, 1997 (1996/ 1997), were retrospectively reviewed.

RESULTS

There were 194 episodes, 62 in 19861 1987 and 132 in 1996/1997. The minimum annual incidence for children younger than 5 years of age increased from 61 per 100000 (179 per 100000 for those <12 months old) in 1986/1987 to 130 per 100000 (349 per 100000 for those <12 months old) in 1996/1997. Sixty-seven (60%) of 111 patients tested in 1996/1997 were HIV-seropositive; none were tested in 1986/1987. The HIV-infected compared with HIV-noninfected were more likely to be malnourished (61% vs. 36%, P = 0.02), less likely to have other underlying disease (12% vs. 50%, P = 0.00001) and more frequently used antibiotics recently (69% vs. 43%, P = 0.008). Penicillin-nonsusceptible isolates were found in 22 (35%) patients in 1986/1987 and 52 (39%) in 1996/1997. There was no significant change in antimicrobial susceptibility during the decade or by HIV serostatus.

CONCLUSIONS

Children in Soweto had a high incidence of pneumococcal bacteremia which doubled during the decade mainly as a result of the impact of the HIV epidemic. There has been no significant change in antimicrobial susceptibility for the decade.

Invasive pneumococcal disease in the immunocompromised host

A normal constituent of the human upper respiratory flora, Streptococcus pneumoniae also produces respiratory tract infections that progress to invasive disease at high rates in specific risk groups. The individual factors that contribute to the development of invasive pneumococcal disease in this distinct minority of persons, include immune (both specific and innate), genetic, and environmental elements. Specific defects in host responses may involve age, deficiencies in levels of antibodies and complement factors, and splenic dysfunction. Combinations of these immune defects contribute to the increased rates of invasive pneumococcal disease in patients with sickle cell disease, nephrotic syndrome, neoplasms, and underlying medical conditions such as diabetes and alcoholic liver disease. The number of risk factors are greatest and the rates of invasive disease are highest in patients with HIV-1 infection, which has emerged as a major risk factor for serious S. pneumoniae infection worldwide.

Opportunistic infections and other clinical manifestations of HIV disease in children

As the decade draws to a close, physicians can be cautiously optimistic about the prevention and treatment of opportunistic infections in children with HIV disease. As more children receive therapy with powerful antiretroviral regimens, fewer are likely to be at risk for opportunistic pathogens. The widespread use of protease inhibitor combination therapies has already resulted in a dramatic decrease in morbidity and mortality in the population of HIV-infected adults. The same effect has been seen at pediatric care centers throughout the United States. Clinicians caring for HIV-infected children are now considering the safety of discontinuing prophylactic therapies for children with sustained immunologic improvement on antiretroviral therapy. For children who remain at risk, prophylactic regimens for PCP and MAC have been shown to decrease the risk for these infections. Preventive regimens for several other opportunistic infections are also available. The understanding of the pathogenesis of HIV and many of the opportunistic pathogens has led to the development of a variety of efficacious therapies for these infections. Despite these advances, physicians can anticipate that HIV-infected children will continue to develop opportunistic infections and other related complications. Some children fail to respond to antiretroviral therapies, whereas others are unable to tolerate the complex medication regimens. Prophylactic therapies are not 100% protective and, despite improved treatments, few opportunistic infections are cured. Most require lifelong maintenance therapy in the absence of immune reconstitution. Drug interactions, complex dosing schedules, adverse side effects, and high costs further limit the efficacy of these therapies. The prophylaxis, diagnosis, and treatment of opportunistic infections are likely to remain integral components of HIV care for the near and distant future.

Nasopharyngeal carriage of multidrug-resistant Streptococcus pneumoniae in institutionalized HIV-infected and HIV-negative children in northeastern Romania

OBJECTIVES

The study compared nasopharyngeal carriage of resistant pneumoniae in human immunodeficiency virus (HIV)-seropositive and -seronegative children.

METHODS

Nasopharyngeal colonization with Streptococcus pneumoniae was investigated during May 1996 in 162 HIV-negative infants and children (age range, 1-38 mo) and 40 HIV-infected children (age range, 39-106 mo) living in an orphanage in Iasi, northeastern Romania. The HIV-infected children lived separated from the other children and were cared for by a different staff. Streptococcus pneumoniae was isolated from 12 of 40 (30%) HIV-infected and from 81 of 160 (50%) HIV-negative children. Antimicrobial susceptibility to penicillin and ceftriaxone was determined by E-test, and to another five antibiotics by disk diffusion. Serotyping was performed by the Quellung method on 81 of 93 (87%) isolates.

RESULTS

Serotypes 6A, 6B, 19A, and 23F together represented 98% of all isolates. Ninety-nine percent of S. pneumoniae isolates were resistant to penicillin, and 74% were highly resistant to penicillin (minimum inhibitory concentration [MIC] > 1 mg/mL); MIC50 and MIC90 to penicillin of the isolates were 2 mg/mL and 8 mg/mL, respectively. Eighty-nine of ninety-one isolates were susceptible to ceftriaxone; 99%, 87%, 87%, 48%, and 21% of the isolates were resistant to trimethoprim-sulphamethoxazole, erythromycin, clindamycin, tetracycline, and chloramphenicol, respectively. Eighty-two (89%) isolates were multidrug resistant (resistant to =/>3 antibiotic classes); 37 of 92 (40%) isolates were resistant to 5 or more antibiotic classes, and 16 of these 37 (43%) belonged to serotype 19A. All serotype 19 isolates were highly resistant to penicillin.

CONCLUSIONS

No significant differences were observed in the resistance rates of S. pneumoniae in HIV-infected children compared to HIV-negative children. Multidrug-resistant pneumococci were highly prevalent in this Romanian orphanage in both HIV-negative and older HIV-infected children. The observed high prevalence of multidrug-resistant pneumococci (coupled with high penicillin resistance) with a limited number of circulating serotypes emphasizes the need to further evaluate the conjugate vaccines in children at risk for invasive pneumococcal infection.

Nasopharyngeal pneumococcal colonization among Kenyan children: antibiotic resistance, strain types and associations with human immunodeficiency virus type 1 infection

OBJECTIVES

To compare pneumococcal nasopharyngeal colonization rates among HIV-1-infected children with those of uninfected children born to seropositive mothers and those of seronegative controls. To determine the predominant serotypes and antimicrobial susceptibility among pneumococcal isolates in Kenya.

METHODS

Nasopharyngeal pneumococcal colonization was examined in 207 children recruited from the Perinatal HIV-1 Transmission Study conducted in Nairobi, Kenya. Colonization was compared among HIV-1-infected children, uninfected children born to seropositive mothers and control seronegative children. Isolates were serotyped and tested for antibiotic susceptibility to penicillin, tetracycline, erythromycin, chloramphenicol, clindamycin and rifampin.

RESULTS

Colonization was higher among HIV-1-infected and uninfected children than among controls only when associated with respiratory illnesses (86% of 7 and 60% of 20 vs. 29% of 31, P = 0.004). No differences were observed when children were asymptomatic (20% of 35, 35% of 94 and 22% of 101). Intermediate penicillin resistance was found in 60% of 94 isolates, 28% were resistant to tetracycline and all isolates were susceptible to the other antibiotics tested. Sixteen serotypes were identified, with 13, 15, 14, 6B and 19F comprising 73% of isolates. Serotype 13 was found in 31% of colonized children. This serotype and 2 others isolated are not found in the current 23-valent polysaccharide vaccine. Overall 41% of colonized children harbored nonvaccine strains.

CONCLUSIONS

Although nasopharyngeal pneumococcal colonization was high among children with respiratory illness born to HIV-1-seropositive mothers, increased asymptomatic colonization did not explain the increased risk of invasive pneumococcal disease associated with HIV-1 infection. Intermediate penicillin resistance was common but high level penicillin and multiple antibiotic resistance were not seen. The prevalence of the unique strains circulating in this region will need to be considered in the design of effective pneumococcal vaccines for use in East Africa.