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Diagnostic Microbiology

The laboratory receives clinical specimens from the wards at the reception area or in the laboratory. Processing of the specimens starts at real time, specifically for cerebrospinal fluid (CSF) and blood culture. Other specimens, if not processed instantly, are kept in the cool box or refrigerator to minimize the impact of time gap.

In this department, improvement of laboratory procedures and techniques is a continuous process. The advancements in processing the specimens and improvement of diagnostic capacity are coming from the experiments and findings of this laboratory, and published literature from the other laboratories.

Once the specimens arrive in the Department of Microbiology, they are handled with care following standard operation procedure (SOP), depending on type of specimens.

Specimens like cerebrospinal fluid (CSF) are handled with high priority. cytology, Gram stain and antigen detection tests are done and reported at real time.

Bacteriological culture is the main service of the whole department. The specimens are processed in aerobic and micro-aerophilic conditions. Since 2001 to April 2007, 58,900 specimens have been cultured and 52% of them were from paying patients.

Among the cultures, blood (31%), CSF (24%) and urine (24%) were the most predominant specimens followed by pus (7%) and throat swab (2%).

In the recent years, the department introduced enriched blood culture media with the support from GAVI's PneumoADIP, and that has lead to progressive increase in blood culture and higher rate of isolation. All the blood culture media, irrespective to the enrolment of the cases in the study, are provided by PneumoADIP of Johns Hopkins University.

Over all Hib is the predominant cause of pyogenic meningitis followed by S. pneumoniae. However, most of the CSF specimens are culture negative due to prior antibiotic use. Etiology of these cases is detected by detection of antigen either by latex agglutination test and / or by Immuno-chromatographic test. Both the tests, for antigen detection, are available in the microbiology laboratory, through PneumoADIP of Johns Hopkins University.

Salmonella typhi is the most common organism among the culture positive cases. Predominance of this organism is more conspicuous in the 2-59 months age group. Other organisms like Klebsiella pneumoniae, Acinetobacter and Serratia are mostly isolated from neonates.

This department is one of the few laboratories in the country and the region that does cultures routinely and isolates and characterizes the fastidious organisms like Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. This capacity is known to the whole world, through the publications and presentations, and thus the department is functioning as the reference laboratory of seven hospitals of Bangladesh and ICDDR,B for surveillance of invasive Pneumococcal diseases in children.

Serological tests

In addition to bacteriological culture, serological tests, mostly relevant to the paediatric age group, are also done in this department. As with the culture, increase in trend is noted here too. On an average, based on last 5 year-data, the department deals with 7479, 4733, 1652, 400, 320 specimens for CRP, Widal, febrile antigen respectively.

Communication between ward and Laboratory:

Microbiology Department maintains a constant communication with the wards for collation and interpretation of the results.

This helps the department to provide better service to the patients and to improve the knowledge. Communication helps us to i) inform about the contaminated specimen and request for a fresh one; ii) get additional information about the patient and/or iii) inform about any urgent report like KLB or any growth from CSF, etc.

Capacity to Identify the Organisms:

In the last several years, the capacity of the laboratory has substantially increased to precisely identify the most of the bacterial isolates upto the species level. Identification is done based on the standard procedures. Primarily the organisms identified based on growth requirements, biochemical tests, analytical profile index (API) and agglutination with specific antisera. Specific antisera are available to confirm the identification and typing of the organisms, like Salmonella, Haemophilus, Pneumococcus and Meningococcus.

Preparation of Reports

The department uses software, developed by a graduate of Johns Hopkins University, which automatically interprets the antibiotic susceptibility results from the measured zone of inhibition, based on the Clinical Laboratory Standard Institute (CLSI) guidelines. Computer generated reports are then delivered to the wards.
Availability of Data

The test results of the department of microbiology are stored in the computer for any future reference. These data can be analysed to find the prevalence and the trend of the infection causing organisms, and their susceptibility pattern. Data are accessible to our clinical colleagues, if they want to look at the trend of infections among their own patients. These are useful for the treatment policy in the wards and the hospital as a whole.
Delivery of Reports

The Department of Microbiology volunteer to deliver the reports to the respective wards. This facilitates the availability of test results within a short time. The results are also communicated to the doctor of the respective unit over telephone. However, this mostly occurs when the duty doctor or the consultant calls the department and enquires about the test results.

Specimens from other hospitals/clinicians: In addition to in house specimens, microbiology laboratory also receives specimens from other hospitals and private practitioners. These specimens are processed in the same way, and sometime with higher care, to attract more specimens from outside.
Waste disposal

With the continuous improvement in the diagnostic capacity, the staffs are also committed to conserve the environment by following the safe waste disposal strategies. Although complete safe waste disposal depends on national program, the department puts its effort to discard the sharps and infectious materials in a safe way, so that environment does not get affected.
Media preparation and Quality Control

The department has separate sections for media preparation which is well equipped with laminar hood, autoclave, distilled water plant and dispensers. Media are prepared following the standard procedures and labelled with date and batch numbers. All these media are then checked for quality, using reference strains from American Type Collection Centre (ATCC), by a person who is not involved in media preparation. Specimens are processed on these media only if they are approved by the quality control (QC) person. Failure of any batch to pass through QC is reviewed and discussed about to find the cause, and appropriate measures are taken to avoid the future mistakes.

 

 

   
 
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