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CORRESPONDENCE
Year : 2002  |  Volume : 20  |  Issue : 4  |  Page : 229-230
 

Isolation and identification of Aeromonas from patients with acute diarrhoea in Kolkata, India


Department of Microbiology, Sri Satya Sai Institute of Higher Medical Sciences, Prashanthigram - 515 134, Puttaparthi, Andhra Pradesh, India

Correspondence Address:
Department of Microbiology, Sri Satya Sai Institute of Higher Medical Sciences, Prashanthigram - 515 134, Puttaparthi, Andhra Pradesh, India



How to cite this article:
Bhat P. Isolation and identification of Aeromonas from patients with acute diarrhoea in Kolkata, India. Indian J Med Microbiol 2002;20:229-30


How to cite this URL:
Bhat P. Isolation and identification of Aeromonas from patients with acute diarrhoea in Kolkata, India. Indian J Med Microbiol [serial online] 2002 [cited 2020 Oct 28];20:229-30. Available from: https://www.ijmm.org/text.asp?2002/20/4/229/6969


Dear Editor,
After reading the article entitled “Isolation and identification of Aeromonas from patients with acute diarrhoea in Kolkata, India”, by S. Kannan et al in Indian Journal of Medical Microbiology (2001;19:190-192) I would like to make a few comments.
One of the major challenges in the diagnosis of gastrointestinal diseases is the recent increase in the number of probable aetiological agents. The common bacterial agents associated with acute diarrhoeal disease come under three groups: recognized enteropathogens, highly associated enteropathogens like Aeromonas and implicated organisms like Providencia alcalifaciens.[1]
Hence, in the laboratory diagnosis of acute bacterial diarrhoea, there is a standard recommended procedure[2] to recover the enteropathogens mentioned above. While reading this article, it gives the impression that the authors were concentrating only on Aeromonas. Plating of stool samples directly on primary inoculation media prior to enrichment is the usual procedure.[2] This gives an idea of the relative preponderance of the aetiological agent in the sample, more so in the case of “highly associated” enteropathogens or “implicated” organisms. Instead, the authors have directly resorted to enrichment method. Since the article deals with acute cases of diarrhoea, use of enrichment is subsequent to the primary inoculation media as in the case of Vibrios. Liquid enrichment like alkaline peptone water is not generally considered necessary in the isolation of Aeromonas except in the study of chronic cases or asymptomatic carriers.[3]
If the authors have processed the samples only for the isolation of Aeromonas without looking for recognized enteropathogens, then the study is biased, as mere demonstration of an organism does not necessarily establish its aetiological role in the clinical samples like stool. In how many samples out of the samples studied did Aeromonas occur as the sole pathogen? In how many cases did Aeromonas co-exist with other enteropathogens? In such a mixed aetiology, what criteria were followed to evaluate their significance? The authors also state that the source of infection might have been “contaminated drinking water or contaminated food” and emphasise “prevalence of Aeromonas in water”. In such a context, certain criteria should have been laid to bring out its aetiological role like a “case-control” study in different age groups, which would have established the aetiological significance statistically. This is important especially in the case of those agents which do not come under the recognized enteropathogens.
The authors have stated that “most of the Aeromonas were resistant to many commonly used antibiotics”. If so, why were the following antibiotics included: novobiocin, erythromycin, vancomycin, streptomycin, colistin, neomycin, polymixin as these are not the commonly used antibiotics against enteropathogens. Is it for selection of antibiotic for therapy or is it to characterize the isolates? It is well known that vancomycin is exclusively used for gram positive organisms especially MRSA, MRS, and multi-drug-resistant enterococci. That being the case, what was the rationale of testing vancomycin against Aeromonas?
Though ciprofloxacin was tested in the AST, it is not shown under results in Table:2. There is no mention of ciprofloxacin. While most cases of acute diarrhoea are self-limiting, in paediatric and geriatric populations, supportive therapy and antimicrobials are often indicated. In this context, information on fluoroquinolones like ciprofloxacin is very relevant and useful. In this article, Table:1 on isolation of Aeromonas with reference to age and sex shows that children below 2 years of age and patients above 61 of age were the largest groups affected.
While converting the percentage of isolates of Aeromonas belonging to various species, the number of isolates of A.shubertii,  A.jandaei   and A.trota were only 3, 2 and 2 respectively. On such small numbers, is it advisable to convert them into percentage and show a “% resistance pattern”. While in the abstract and results, the percentage of various Aeromonas species are shown in a descending order of frequency, this pattern should have been followed in [Table:2] as consistency in presentation is important. There is discrepancy in the number of isolates in the different species shown in results, and Table:3.
This paper needed a better presentation of methodology for processing stool samples and should have been considered for publication only after the discrepancies were corrected. Besides, the authors could have shown co-relation between different species and age groups as more than 50% isolates belonged to two species of Aeromonas (A.hydrophila and  A.caviae  ). To demonstrate A.shubertii (4 isolates) A.jandaei (2 isolates), and A.trota (2 isolates) as aetiological agents, one needs to know their presence in non-diarrhoeal healthy persons and in the environment. Is there a seasonality in the Aeromonas - associated diarrhoeal disease? 

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