Distribution of capsular types and antibiotic susceptibility of invasive Streptococcus pneumoniae isolated from aborigines in central Australia

Evaluation of impact of 23 valent pneumococcal polysaccharide vaccine following 7 valent pneumococcal conjugate vaccine in Australian Indigenous children

BACKGROUND

High incidence and serotype diversity of invasive pneumococcal disease (IPD) in Indigenous children in remote Australia led to rapid introduction of 7-valent conjugate pneumococcal vaccine (7vPCV) at 2, 4 and 6 months in 2001, followed by 23-valent polysaccharide pneumococcal vaccine (23vPPV) in the second year of life. All other Australian children were offered 3 doses of 7vPCV without a booster from 2005. This study evaluated the impact of the unique pneumococcal vaccine schedule of 7vPCV followed by the 23vPPV booster among Indigenous Australian children.

METHODS

Changes in IPD incidence derived from population-based passive laboratory surveillance in Indigenous children <5 years eligible for 23vPPV were compared to non-Indigenous eligible for 7vPCV only from the pre-vaccine introduction period (Indigenous 1994-2000; non-Indigenous 2002-2004) to the post-vaccine period (2008-2010 in both groups) using incidence rate ratios (IRRs) stratified by age into serotype groupings of vaccine (7v and 13vPCV and 23vPPV) and non-vaccine types. Vaccine coverage was assessed from the Australian Childhood Immunisation Register.

RESULTS

At baseline, total IPD incidence per 100,000 was 216 (n=230) in Indigenous versus 55 (n=1993) in non-Indigenous children. In 2008-2010, IRRs for 7vPCV type IPD were 0.03 in both groups, but for 23v-non7v type IPD 1.2 (95% CI 0.8-1.8) in Indigenous versus 3.1 (95% CI 2.5-3.7) in non-Indigenous, difference driven primarily by serotype 19A IPD (IRR 0.6 in Indigenous versus 4.3 in non-Indigenous). For non-7vPCV type IPD overall, IRR was significantly higher in those age-eligible for 23vPPV booster compared to those younger, but in both age groups was lower than for non-Indigenous children.

CONCLUSION

These ecologic data suggest a possible "serotype replacement sparing" effect of 23vPPV following 7vPCV priming, especially for serotype 19A with supportive evidence from other immunogenicity and carriage studies. Applicability post 10vPCV or 13v PCV priming in similar settings would depend on local serotype distribution of IPD.

Invasive serotype 1 Streptococcus pneumoniae outbreaks in the South Pacific from 2000 to 2007

In New Caledonia, Wallis and Futuna, and French Polynesia, an active surveillance system was established to monitor pneumococcal serotype prevalence between 2000 and 2007. The most prevalent serotype was serotype 1, which belonged to the major clonal complex sequence type 306 (ST306) and was responsible for invasive pneumococcal disease outbreaks.

Antimicrobial resistance among respiratory pathogens collected in Thailand during 1999-2000

A multi-center surveillance study was conducted in Thailand during 1999-2000 to determine antimicrobial susceptibilities among the respiratory pathogens Streptococcus pneumoniae (n = 206), Haemophilus influenzae (n = 305), and Moraxella catarrhalis (n = 39). Of the S. pneumoniae isolates collected, 33.5% were penicillin-susceptible, 27.2% intermediate and 39.3% resistant. Expectedly, resistance rates to beta-lactams were higher among penicillin-resistant (ceftriaxone, 14.8%; amoxicillin-clavulanate, 42.0%; cefuroxime, 100%) than penicillin-susceptible (ceftriaxone, 0%; amoxicillin-clavulanate, 0%; cefuroxime, 0%) isolates. Likewise, azithromycin and clarithromycin resistances were 4.3% and 5.8% among penicillin-susceptible isolates, and 77.8% and 95.1% among penicillin-resistant isolates. All S. pneumoniae remained susceptible to vancomycin and 99.5% were susceptible to levofloxacin. Multidrug resistance (resistance to >3 antimicrobial classes) was present in 25.2% of pneumococcal isolates (n = 52), with resistance to azithromycin, penicillin and trimethoprim-sulfamethoxazole the most common phenotype (40/52 isolates; 77.0%). Among the isolates of H. influenzae, the prevalence of beta-lactamase production was 45.2%. All isolates of H. influenzae were susceptible to amoxicillin-clavulanate, azithromycin, ceftriaxone, cefuroxime and levofloxacin while 49.5% were resistant to trimethoprim-sulfamethoxazole. All 39 isolates of M. catarrhalis produced beta-lactamase. Azithromycin (MIC90, < or = 0.03 microg/ml) and levofloxacin (MIC90, 0.03 microg/ml) were the most active agents tested against M. catarrhalis. The results of this study may serve as a baseline for future studies to monitor antimicrobial susceptibilities among respiratory pathogens in Thailand.

Worldwide prevalence of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the SENTRY Antimicrobial Surveillance Program, 1997-1999

The in vitro activities of numerous antimicrobials against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from patients with bloodstream and respiratory tract infections in the United States, Canada, Europe, Latin America, and the Asia-Pacific region were studied in the SENTRY Antimicrobial Surveillance Program. Penicillin resistance (minimum inhibitory concentration, > or =2 microg/mL) was noted in all 5 geographic regions, and a high and increasing rate of macrolide resistance among S. pneumoniae isolates was observed. Elevated rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline were seen. beta-Lactamase-mediated resistance in H. influenzae to amoxicillin and variable trimethoprim-sulfamethoxazole resistance by region were documented. Resistance to several drugs continues to emerge among pneumococci worldwide, but more stable resistance patterns have been noted for H. influenzae and M. catarrhalis. Continued surveillance of this pathogen group appears to be prudent.

Comparison of a classical phagocytosis assay and a flow cytometry assay for assessment of the phagocytic capacity of sera from adults vaccinated with a pneumococcal conjugate vaccine

Antibody- and complement-mediated phagocytosis is the main defense mechanism against Streptococcus pneumoniae. A standardized, easy to perform phagocytosis assay for pneumococci would be a great asset for the evaluation of the potential efficacy of (experimental) pneumococcal vaccines. Such an assay could replace the laborious phagocytosis assay of viable pneumococci (classical killing assay). Therefore, a newly developed phagocytosis assay based on flow cytometry (flow assay) was compared with the conventional killing assay and enzyme-linked immunosorbent assay (ELISA), using sera obtained from adults pre- and postvaccination with either a bivalent conjugate, a tetravalent conjugate, or the 23-valent polysaccharide vaccine. Highly significant correlations were observed between flow assay phagocytosis titers, killing assay phagocytosis titers, and ELISA antibody titers for serotype 6B and 23F as well. For serotype 19F, strong correlations were only observed between killing assay and ELISA titers. A potential drawback of the flow assay might be the low sensitivity compared with that of the killing assay. The choice of what assay to use, however, will depend on the objectives of the assay. When speed, easy performance, sample throughput, improved worker safety, absence of influence of antibiotics, and absence of false positives are the major criteria, the flow assay is the method of choice. When higher sensitivity is the major requirement, the classical killing assay should be used.

Conjugate pneumococcal vaccines for aboriginal children in Australia

Research indicates a high burden of pneumococcal disease and great potential benefits of conjugate vaccines in Indigenous Australian children, who should have high priority for delivery of these vaccines. Incidence of invasive pneumococcal disease in Indigenous people in central Australia is the highest reported in the world (2053 per 100,000 persons per year in those aged under two years). Acute respiratory infection is a major cause of morbidity in Indigenous children in rural and remote areas. Early pneumococcal colonisation of the nasopharynx and high rates of carriage are seen in Indigenous children, and are probably related to their high rates of ear disease. Current seven-valent conjugate vaccines are likely to cover about two-thirds of invasive isolates in Indigenous Australian children; 11-valent vaccines will cover a higher proportion. Questions remain about the best vaccine carrier protein and the likely impact of vaccine on ear disease, pneumococcal carriage and antibiotic resistance.

Differing serologic responses to an haemophilus influenzae type b polysaccharide-neisseria meningitidis outer membrane protein conjugate (PRP-OMPC) vaccine in australian aboriginal and caucasian infants - implications for disease epidemiology

This study compared Hib antibody responses to a single lot of PRP-OMPC vaccine given at 2, 4 and 12 months to 57 Aboriginal infants in rural areas of the Northern Territory and 56 Caucasian infants in Sydney, Australia. The Aboriginal infants had lower levels of antibody in cord blood (P>0.05), which were significantly lower (P<0.02) by 2 months of age. Antibody responses to one or two doses of vaccine, measured at 4 and 12 months of age, were similar but the geometric mean titre following the booster dose in Aboriginal infants was significantly lower (1.98 vs. 6.04 mcg/ml, P = 0.002). Low preimmunisation antibody is consistent with the early onset of Hib disease in Aboriginal infants before immunisation. Lower responses to boosting could correlate with persistence of Hib colonisation in indigenous populations.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.

Etiology of acute lower respiratory tract infection in Central Australian Aboriginal children

BACKGROUND

Aboriginal children in central Australia have attack rates for acute lower respiratory tract infection (ALRI) that are similar to those in developing countries. Although mortality rates are much lower than in developing countries, morbidity is high and ALRI is still the leading cause of hospitalization. However, there are no data on the etiology of ALRI in this population.

METHODS

We prospectively studied 322 cases of ALRI in 280 Aboriginal children admitted to the hospital. Blood, urine and nasopharyngeal aspirate samples were examined for evidence of bacterial, viral and chlamydial infection.

RESULTS

The combination of blood culture, viral studies and chlamydial serology provided at least 1 etiologic agent in 170 of 322 (52.5%) cases. Assays for pneumolysin immune complex and pneumolysin antibody increased etiologic diagnosis to 219 (68.0%). Blood cultures were positive in 6% but pneumolysin immune complex and pneumolysin antibody studies were positive in one-third of cases. Evidence of viral infection was present in 155 (48%) of cases compared with 12% in controls (P < 001). There were only 7 possible cases and 2 definite cases of Chlamydia trachomatis and 3 cases of Chlamydia pneumoniae. Coinfection was common in these children.

CONCLUSION

These findings have implications for both standard treatment protocols and vaccine strategies. The high rate of coinfection may make it difficult to develop simple clinical predictors of bacterial infection. In the setting of a developed country with efficient patient evacuation services, management algorithms that focus on disease severity and need for hospital referral will be most useful to health staff in remote communities. Pneumococcal conjugate vaccines will be required to reduce the high attack rate of pneumococcal disease.

Penicillin resistance in laboratory isolates of Streptococcus pneumoniae, in Western Australia, 1990-1994

Increasing frequency of penicillin resistance in Streptococcus pneumoniae has been reported worldwide. We report on clinical isolates of penicillin-resistant pneumococci (PRP) in Western Australia (WA) from 1990-1994. A retrospective survey of laboratories performing susceptibility testing, or receiving isolates referred from rural areas found resistant on oxacillin disc screening, was undertaken. Four of 11 laboratories could provide data for the five year time period inclusive. Information was provided on susceptibility to penicillin, type of specimen, date of isolation and; age, sex and race of individuals with PRP. Penicillin resistance increased from 1.3% to 9.0% over the five year period. PRP were rarely invasive. Highest age specific rates per 100,000 were found in children < 5 years (19.4) and adults > or = 60 years (5.1). Aboriginal ethnicity was associated with resistance. The increasing frequency of PRP in WA indicates the need for surveillance systems for their detection.

Antibiotic management of pneumococcal infections in an era of increased resistance

Pneumococci are a leading cause of bacterial meningitis and bacteraemia, as well as pneumonia, otitis media and sinusitis in childhood. These organisms recently have shown a dramatic increase in antibiotic resistance. Penicillin-resistant pneumococci are of special concern as they are often resistant to other unrelated antibiotics. This is of particular significance to Aboriginal children who have among the highest rates of pneumococcal infection in the world. Laboratories should now test all invasive pneumococcal isolates for penicillin and third generation cephalosporin resistance. Local treatment guidelines are required for pneumococcal infections, especially for meningitis, taking into account the prevalence of resistant strains within the community. At present, penicillin and amoxycillin remain the drugs of choice for pneumococcal infections, with the exception of meningitis where initial empirical therapy must be with a third generation cephalosporin. Judicious antibiotic use, which avoids over-prescribing and unnecessary use of broad-spectrum agents, improved living standards in underprivileged communities and introduction of an effective conjugate vaccine, able to reduce the rates of pneumococcal infection and hopefully colonization, may limit the spread of resistant strains.

Pneumococcal vaccination: an important strategy to prevent pneumonia in Aboriginal and Torres Strait Island adults

The objective of the study was to examine the appropriateness of the National Health and Medical Research Council (NHMRC) recommendations concerning pneumococcal vaccination for Aboriginal and Torres Strait Island adults. Laboratory surveillance of invasive pneumococcal disease identified 95 cases acquired by adults 15 years of age and over in Far North Queensland from 1992 to 1995. The most common diagnosis was pneumonia (77 per cent). Sixty-one cases (64 per cent) occurred in Aboriginal and Torres Strait Island adults, who acquired the disease at a younger age (mean 40 years) than did other adults (mean 50 years). Most (93 per cent) of the Aboriginal and Torres Strait Island adults had at least one of the pre-existing medical conditions in the NHMRC criteria for pneumococcal vaccination. The most common was 'alcohol abuse' (62 per cent). Fifty-three (93 per cent) of the pneumococcal isolates from the Aboriginal and Torres Strait Island adults who had pre-existing conditions were serotyped. Fifty (94 per cent) belonged to types included in the currently available pneumococcal vaccine. We conclude that the NHMRC recommendations for pneumococcal vaccination are appropriate, considering the pattern of invasive pneumococcal disease that occurs in Aboriginal and Torres Strait Island adults in Far North Queensland. Because pneumococcal vaccination can reduce the pneumonia-associated morbidity and premature mortality experienced by Aboriginal and Torres Strait Island adults, the vaccine should be offered routinely to those considered to be at risk, particularly young men who have recently begun to consume hazardous amounts of alcohol, and recently diagnosed diabetics.

Susceptibility of pneumococcal carriage isolates to penicillin provides a conservative estimate of susceptibility of invasive pneumococci

OBJECTIVE

Because of its practical importance for public health monitoring in developing countries, we aimed to determine whether susceptibility to penicillin of pneumococci isolated from the upper respiratory tract (URT) is representative of the susceptibility of pneumococci causing pneumonia in children.

METHOD

The serogroup distribution and minimum inhibitory concentration of penicillin for 56 and 90 isolates from blood and cerebrospinal fluid, respectively, were compared with those of 833 pneumococcal carriage isolates from Papua New Guinean children. These included 154 and 98 strains from bacteremic and nonbacteremic hospitalized patients with pneumonia, respectively, 350 from outpatients with respiratory infections and 176 and 55, respectively, from children in a community-based study who were healthy or sick with pneumonia.

RESULTS

Proportions of pneumococci intermediately resistant to penicillin were comparable in the URT and blood (60%) in 1985 through 1987 when serogroup distributions in the two sites were similar. However, penicillin resistance was higher in the URT (75%) than blood (44%) in 1980 through 1984 when the less frequently carried, less resistant serogroups (1 to 5, 7 to 12, 45 and 46) accounted for a high proportion of bacteremic strains.

CONCLUSIONS

URT isolates from any group of sick or healthy children could provide a conservative estimate of antimicrobial susceptibility of invasive strains and is a practical way of monitoring susceptibility as well as evaluating the continued effectiveness of standard antibiotic therapy. If there was cause for concern, it would then be necessary to examine invasive isolates.