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Research of the Department
For more than 10 years the laboratory is conducting the surveillance on prevalence and drug resistance of Salmonella typhi. The work, published in the British Antimicrobial Society Journal, showed the emergence of multidrug (Amoxicillin, Cotrimoxazole and Chloramphenicol) resistant S. typhi. Continued monitoring on trend of drug resistance revealed a decrease in drug resistance, and a marked difference between the strains isolated from hospital and community.
All these research outcome have paramount implications in typhoid treatment policy in Bangladesh and beyond. The department is still continuing the surveillance to monitor the trend of drug resistance of S. typhi.
Recently, we found ciprofloxacin resistant strains of S. typhi and this was reported in the American Society of Microbiology (ASM) Journal. This was the first report ever, with molecular aspects of resistance showing the evidence of double mutation by PCR-RFLP done in our department.
In addition to that we did molecular finger printing of these strains is also done and found that all of them are identical, indicating that the same clone is circulating in the country.
The department did the pioneering work to determine the value of widal test in diagnosing typhoid fever. This finding on cut-off value in this report is still used as the only reference for sero-diagnosis of typhoid in children of Bangladesh.
In addition to drug resistance, the Department of Microbiology has also been monitoring the prevalence of typhoid fever in different age groups for last several years. This part of work revealed the fact that the present concept of typhoid fever is misleading for immunization policy and that the existing typhoid vaccines are not appropriate to protect the most vulnerable children. This finding from our department was published in the Pediatric Infectious Disease Journal of USA. Publication of this report from our group has contributed to change the typhoid vaccination policy. Further, few multinational research companies are now working to produce an appropriate vaccine for young infants, which is suitable to be incorporated in the national immunization program.
Pneumonia and Meningitis
Streptococcus pneumoniae and Haemophilus influenzae are the most common cause pneumonia and meningitis, and are globally responsible for more than 1.5 million deaths of children every year. Department of Microbiology of Dhaka Shishu Hospital is working on these organisms, isolated form pneumonia and meningitis cases, since 1990.
This laboratory did a pioneering and ground breaking work for diagnosis of culture negative pneumococcal meningitis cases. The immuno-chromatographic test (ICT) developed for testing the pneumococcal antigen in urine was successfully used to detect the antigen in CSF with 100% sensitivity and specificity. This result was well taken by the pneumococcal research group, and now it is in use in a multicountry study. This department is also monitoring the drug resistance and serotype distribution of this organism.
Reports from the department showed that most of the S. pneumoniae strains are sensitive to penicillin and other drugs, except cotrimoxazole. About 70% of the strains are resistant to cotrimoxazole [Figure: Susceptibility pattern of S. pneumoane], which is recommended by WHO as the drug of choice at community level. The reports are further strengthened by the similar findings from other countries in the region. These reports were enough influential to convince WHO to consider the modification of recommendation from contrimoxazole to amoxicillin.
S. pneumoniae has 90 different serotypes and the types vary from population to population and from country to country. Information about serotype distribution is very important for appropriate vaccine formulation. However, there are only few laboratories in the world that has the expertise to doserotyping of Pneumococcus. These studies on prevalence of pneumococcal serotype revealed that the serotypes of Bangladesh are different from those of other countries, and the existing 7 valent vaccine (Pravner), which are in use in the USA, will cover only 23% and 22% of pneumococcal pneumonia and meningitis cases respectively. On the other hand the coverage with the upcoming vaccine can be as high as 59% for the pneumococcal pneumonia cases of Bangladesh.
These studies and capacities in the field of pneumococcal diseases are being documented through publications of results in reputed international journals. In the recent years the department established a surveillance for invasive pneumococcal diseases that includes 7 hospitals and ICDDR,B. It can be mentioned that the contribution in the field pneumococcal diseases has helped to establish the department as the reference laboratory for 7 hospitals and also ICDDR,B. All these work have placed the laboratory among the leading laboratories in the field of pneumococcus. Findings on distribution of pneumococcal serotype have influenced the initiation of research groups of the multinational
vaccine companies to work on new formulation of pneumococcal vaccine(s), and the new generation of vaccines will contain the predominant serotypes of the country.
This is another important cause of meningitis and pneumonia. The department has reported the prevalence of this organism in causing meningitis with gradual increase, in 1997.
Since then we are continuing our work with this organism specifically on prevalence and drug resistance. Age distribution of Hib cases in Bangladesh was found to be different from those of the developed part of the world in pre-vaccine era. This has a significant implication in the vaccination policy for the population of Bangladesh.
In the recent years, a progressive increase of multidrug resistance in Haemophilus influenzae is observed. The department also found that the cases with multidrug resistance have a significant relation with disability and death. All these data have implications on treatment policy for meningitis, and for the argument in favour of introducing Hib vaccine in national immunization program.
The department is now working on direct detection of MDR gene of Hib in the specimens, which will facilitate the detection of drug resistance in the cases where bacteria will not grow due to prior antibiotic therapy.
Preliminary data showed that the MDR gene of Hib can be detected from culture negetive CSF specimen.
Vericella-zoster virus (VZV)
Infections with VZV, commonly known as chicken pox, are usually self limiting. However, the infection may be severe if it occurs in older age group or neonates. Our sero-prevalence study showed the trend of sero-protection in different age groups. About 80% of the adults have seroprotection and this antibody is successfully transmited from mother to newborns. Hoewever, the protection declines to almost baseline by the 2nd year of life. So, a “U” shaped trend of sero-protection. Until now this is the only available data on sero-prevalence of VZV.
Hepatitis A virus (HAV)
HAV infection in childhood mostly remains asymptomatic, however, severity of infection increases with age. Improvement of hygiene contributes to a shifting in age pattern of HAV infection. We did a sero-prevalence study in different age groups of different socio-economic status to see the sero-protection in different groups.
The study revealed that population of higher socioeconomic group, are lacking protective antibody. This has an implication in vaccination policy to protect the susceptible group of children.
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