Serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive disease in Thai children younger than 5 years old, 2000-2005

In order to predict the potential benefit of pneumococcal conjugate vaccines (PCV), we evaluated the serotype coverage of the 7-, 9-, 11- and 13-valent PCV over the isolates causing invasive pneumococcal disease (IPD) in Thai children. One hundred and fifteen Streptococcus pneumoniae isolates from sterile sites in children younger than 5 years old between 2000 and 2005 were serotyped. The coverages of 7-, 9-, 11-, and 13-valent PCV were 69%, 73.8%, 73.8% and 85.7% in children younger than 2 years, and 73.9%, 77.4%, 77.4% and 87.8% in children younger than 5 years of age, respectively. 69.6% and 22.6% of the isolates were non-susceptible to penicillin and cefotaxime. 7-valent PCV covered 89% and 100% of penicillin and cefotaxime non-susceptible isolates.     

Catch-up vaccination against Haemophilus influenzae type b in human immunodeficiency virus-infected Thai children older than 2 years old

Although most of Thai children older than 2 years are immune against Haemophilus influenzae type b (Hib) without prior vaccination, it may not be the case in HIV-infected children. Of 44 HIV-infected children tested before vaccination at the mean age of 36 months (range 24-84 months), 32 (73%) were susceptible (anti-PRP <0.15 microg/ml). At 6 months after a single dose of tetanus-conjugated Hib vaccination, 67% developed anti-PRP >/=0.15 microg/ml, however, only 33% developed titer of >/=1 microg/ml. Four of seven (57%) with anti-PRP 0.15-0.99 microg/ml at baseline were boosted to the titer of >/=1 microg/ml after vaccination. Seroconversion rate and geometric mean titer (GMT) level in response to the vaccination did not correlate with HIV stage, but did correlate with viral load level of 100,000 copies/ml. HIV-infected children older than 2 years would benefit from Hib vaccination, although, one dose catch-up schedule is not sufficient in a third of these children. A second dose is needed in these children especially those with viral load of level of >100,000 copies/ml.     

Effect of reference electrode position on the compound muscle action potential (CMAP) onset latency

Compound muscle action potential (CMAP) onset latency is interpreted to reflect the arrival time at the muscle of impulses in the fastest-conducting motor nerve fiber. However, we have observed that the position of the reference or indifferent electrode (E2) affects CMAP onset latency. Motor nerve conduction studies (NCS) of the median, ulnar, and deep ulnar motor (DUM) nerves on 20 normal hands were performed using both traditional bipolar and experimental monopolar (referenced to the contralateral hand) montages. As the position of E2 was altered, the CMAP onset latency varied 0.1-0.5 ms for the median NCS, 0.1-0.3 ms for the ulnar NCS, and 0.1-1.5 ms for the DUM NCS. This study demonstrates that E2 recorded potentials are significant and vary with positioning, affecting motor onset latency. This has implications both for reference values and the physiologic interpretation of the CMAP waveform.     

Quantitative electromyography

Quantitative EMG is an MUAP analysis technique providing objective information on the NEE. The concept and techniques are not new; however, with the advancement of computer technology, quantitative EMG is now more easily performed. The study requires solid knowledge of basic neurophysiology and access to the appropriate instrument to provide smooth technique and accurate interpretation. Despite recent technical advances, the original MUAP parameters defined by Buchthal are still widely used today as reference values. It is increasingly recognized that many factors can influence the obtained parameters. The ability to measure something does not mean that it is fully understood. The future of quantitative EMG will depend on increased understanding of the physiologic and pathophysiologic significance of the detailed numeric parameters that are generated.     

Immunogenicity and safety of monovalent influenza A (H1N1) 2009 in HIV-infected Thai children

To evaluate the immunogenicity and safety of the monovalent pandemic influenza A (H1N1) 2009 (pH1N1) vaccine in HIV-infected Thai children, 2 doses, 28 days apart, of non-adjuvant monovalent pH1N1 vaccine (Panenza^® by Sanofi Pasteur, 15 μg/dose) provided by the National Health Promotion Program of the Thai Ministry of Public Health were given to HIV-infected children. Immunogenicity was measured by hemagglutination inhibition test (HAI) using two antigens, pH1N1 (A/Thailand/104/09) and seasonal influenza A H1N1 (A/Brisbane/59/07-like), at baseline, and 28 days after each dose. Serologic response was defined as four-fold rising of HAI titer or HAI titer ≥1:40 for those with baseline titer ≤1:10. Adverse events were recorded for 7 days after each vaccination. Of the 119 HIV-infected children enrolled, 60 (50.4%) were female with a median (IQR) age of 10.4 (7.2-13.7) years. All but 2 (98.3%) children were receiving antiretroviral therapy. At baseline, the median CD4 cell count was 782 (570-1149) cells/mm³, 91 (80.5%) children had HIV RNA level <40 copies/ml. The baseline HAI titer ≥1:40 for pH1N1 and seasonal H1N1 were 45.4%, and 39.5%, respectively. At 28 days after doses 1 and 2, the serologic response rates for pH1N1 were 54.2% and 67.8% with the geometric mean titer of 109.9 and 141.8; and serologic response rate when tested with seasonal H1N1 were 2.5% and 3.5%, respectively. The presence of baseline HAI titer for pH1N1 or seasonal H1N1 was found to be associated with serologic response. The vaccine was well tolerated. The results suggested that monovalent pH1N1 vaccine was immunogenic and safe in well controlled HIV-infected children with low level of cross reacting antibody to seasonal H1N1.