Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Bhanu K Bhakhri

"The Journal of Clinical and Diagnostic Research (JCDR) has been in operation since almost a decade. It has contributed a huge number of peer reviewed articles, across a spectrum of medical disciplines, to the medical literature.
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Dr Bhanu K Bhakhri
Faculty, Pediatric Medicine
Super Speciality Paediatric Hospital and Post Graduate Teaching Institute, Noida
On Sep 2018




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Department of Dematolgy,
Believers Church Medical College,
Thiruvalla, Kerala
On Sep 2018




Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."



Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



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Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018




Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
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I wish JCDR a great success and I hope that journal will soar higher with the passing time."



Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




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Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata




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Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help ones reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journalsNo manuscriptsNo authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011

Important Notice

Original article / research
Year : 2009 | Month : December | Volume : 3 | Issue : 6 | Page : 1921 - 1927

Inducible AmpC Beta-Lactamase Producing Pseudomonas Aeruginosa Isolated In A Rural Hospital Of Central India

BASAK S *,KHODKE M** ,BOSE S***,MALLICK SK****

*(M.D)Professor of Microbiology, **search Assistant, Deptt of, Microbiology, ***(M.D)Professor of Microbiology,***(M.B.B.S)Tutor, Deptt. of Microbiology Jawaharlal Nehru Medical College,Wardha(M.S)

Correspondence Address :
Dr. S. Basak
Professor of Microbiology
J. N. Medical College
Sawangi (M), Wardha-442004 (M.S.)
E-mail: drsbasak1@yahoo.com.

Abstract

Pseudomonas aeruginosa, one of the most common pathogen causing nosocomial infections, shows increasing resistance to β-lactam antibiotics especially by producing AmpC β-lactamase. Hence, this study was undertaken to determine the prevalence of inducible AmpC β-lactamases producing Pseudomonas aeruginosa in our hospital and their antibiotic susceptibility pattern to newer antipseudomonal antibiotics.
Consecutive 244 Pseudomonas aeruginosa isolates were studied. Isolates showing blunting of ceftazidime zone of inhibition adjacent to cefoxitin disc were considered as screen positive and were selected for confirmation of inducible AmpC β-lactamases producing by modified three dimensional test and AmpC disc test. In vitro susceptibility pattern of antipseudomonal antibiotics were done by Kirby Bauer disc diffusion method.
Out of 244 Pseudomonas aeruginosa isolates 47 (19.3%) were screen positive, which were confirmed by modified three dimensional test and AmpC disc test. The highest sensitivity pattern observed was Imipenem, Amikacin and Ciprofloxacin.
We conclude that to avoid misuse of antibiotics and to start proper antibiotics to hospitalized patients, tests for AmpC β-lactamases should be done in Clinical Microbiology laboratories.

Keywords

Pseudomonas aeruginosa, Inducible AmpC β-lactamase,AmpC disc test.

Introduction
Pseudomonas aeruginosa is one of the most common pathogen causing nosocomial infection. It is intrinsically resistant to many antibiotics including newer β-lactam antibiotics or can develop resistance during treatment leading to high mortality and morbidity.

The commonest mechanism of β-lactam antibiotic resistance in Gram negative bacteria is predominantly due to the production of β-lactamases that cleave the structural β-lactam ring. According to molecular structure classification by Ambler 1980 the major classes of β-lactamases are A, C, D (1).

Pseudomonas aeruginosa can produce all major classes of β-lactamases (A, C, D) and also metallobetalactamases i.e. class B. Persistent exposure of Pseudomonas aeruginosa to β-lactam antibiotics leads to mutation and over production of AmpC or class C β-lactamases. These are cephalosporinases which were classified by Ambler in 1980 (1) as molecular class C and according to Bush et al (2) were classified as Group I. AmpC β-lactamases confer resistance to oxyiminocephalosporins,7α methoxycephalosporins ( cefoxitin and cefotetan).

AmpC β-lactamases which are chromosomally mediated have been described in Acinetobacter sp, Morganella morganii, Citrobacter freundii, Enterobacter sp, Pseudomonas aeruginosa, Yersinia enterocolitica, Serratia marcescens, E.coli, Hafnia alvei etc. In most of these bacteria AmpC is inducible via a system involving ampD, ampG, ampR and intermediates in peptidoglycan recycling (3),(4). The ampC gene of E.coli is normally expressed at a low level but not induced as ampR is missing (5).

Plasmid mediated AmpC β-lactamases have arisen through the transfer of chromosomal genes of AmpC β-lactamases onto plasmids (6). Plasmid-mediated AmpC β-lactamases have been found in Klebsiella pneumoniae, Salmonella sp, Proteus mirabilis and even E. coli and were first reported in 1988 (7).

Presently, all plasmid mediated AmpC β-lactamases have similar substrate profile to chromosomal AmpC β-lactamases. But the only difference is chromosomal AmpC β-lactamases are inducible where as plasmid mediated AmpC β-lactamases are uninducible (8).

AmpC β-lactamases confer resistance to cephalosporins in the oxyiminogroup (ceftazidime, cefotaxime, ceftriaxone, ceftizoxime, cefuroxime) and the 7-α-methoxy group (cefoxitin, cefotetan, cefmetazole, moxalactam) and monobactum (azotrenam) and are not affected by available β-lactamase inhibitors i.e. clavulanic acid, sulbactum etc.

AmpC β-lactamases producing organisms are on the rise and leads to therapeutic failure if 3rd Generation cephalosporins are given empirically or not tested in the laboratory for AmpC β-lactamases production. Specially, inducible AmpC β-lactamases can be induced to several hundred folds higher in presence of clavulanic acid, where as clavulanic acid is commonly used as Extended spectrum β-lactamases (ESBL) inhibitor (9).

Aims & Objectives
The present study was undertaken:
1. To determine the prevalence of inducible AmpC β-lactamase producing Pseudomonas aeruginosa isolated in a rural hospital in Central India
2. To detect the antibiotic susceptibility pattern of Pseudomonas aeruginosa strains to newer antipseudomonal antibiotics.

Material and Methods

The study was conducted for a period of one year from 1st September 2006 to 31st August 2007. A total no of 244 Pseudomonas aeruginosa strains were isolated from different clinical specimens e.g. urine, pus, sputum, blood, endotracheal tube secretions and others in Microbiology laboratory of Jawaharlal Nehru Medical College, Wardha (M.S.) and were identified as per conventional methods (10). Other specimens include throat swab, ear discharge, catheter tips, peritoneal fluid, vaginal swab, swab from buccal mucosa etc. Antibiotic susceptibility pattern of Pseudomonas aeruginosa isolates to newer antipseudomonal antibiotics e.g. Meropenem(10µg), Imipenem(10µg), Amikacin(30µg), ciprofloxacin(5µg), Pipercillin/Tazobactum(100/10µg), Azotrenam(30µg), Cefepime(30µg), Ceftazidime(30µg), Netilmicin(30µg),was detected by Kirby-Bauer disc diffusion method (11). Antibiotics discs were procured from HiMedia Laboratories Pvt. Ltd, India. Screening of AmpC β-lactamase was done by disc antagonism test (12). Confirmation of AmpC β-lactamase production was done by modified three dimensional test (MTDT) (13) and AmpC disc test (14).

Disc Antiagonism Test
In this test, lawn culture of test isolate (0.5 Mc Farland) was put over Muller-Hinton agar plate (MHA) and ceftazidime (30µg) and Cefoxitin (30µg) disc were placed 20mm apart from centre to centre. Plates were incubated for 18-20 hours at 37o C. AmpC β-lactamase inducibility was recognized by isolates showing blunting of ceftazidime zone of inhibition adjacent to cefoxitin disc and were considered screen positive (12) (Table/Fig 1) .

Modified Three Dimensional Test (MTDT)
Confirmation of AmpC β-lactamase production was done by modified three dimensional test (MTDT) as described by Manchanda et al (13). 10-15mg fresh overnight growth from Muller Hinton agar (MHA) was taken in a sterile 200µl ependroff tube.50 µl peptone water was added and centrifuged at 800g for 15 minutes. Then by repeated freeze thawing for five to seven times, the crude enzyme extract was prepared. Lawn culture of E. coli ATCC 25922 was done in MHA plates and cefoxitin (30µg) disc was placed on the plate. A 3 cm linear slit was cut using a sterile scalpel blade 3 mm away from the cefoxitin disc. At the other end of the slit a well was cut. 30µl of crude enzyme extract was put in the well and plates were incubated.

Interpretation of MTDT:
Isolates showing clear distortion of zone of inhibition was taken as AmpC producers (Table/Fig 2). Isolates with no distortion of zone of inhibition was taken as AmpC nonproducers. Isolates with minimal distortion was taken as indeterminate strains.

AmpC Disc Test
AmpC β-lactamase production was further confirmed by AmpC disc test as described by Black et al (14).

Tris EDTA was used to permeabilize the bacterial cell and release of β-lactamase into external environment. AmpC discs were prepared in house. 20µl of 1:1 mixture of sterile saline and 100X Tris-EDTA was applied to sterile filter paper disc. The discs were allowed to dry and stored at 2-8o C. Before use, the AmpC discs were rehydrated with 20 µl of sterile saline and 8-10 colonies of test strains was applied to a disc. A lawn culture of E. coli ATCC 25922 was done on Muller Hinton agar (MHA) plate. A Cefoxitin (30µg) disc placed on this inoculated MHA plate. The inoculated AmpC disc was placed almost touching the cefoxitin disc with inoculated disc surface in contact with agar surface. The plates were then incubated overnight at 37o C.

Interpretation Of AmpC Disc Test
Isolates showing either an indentation or a flattering of the zone of inhibition indicating enzymatic inactivation of cefoxitin were taken as positive for AmpC production (Table/Fig 3),(Table/Fig 4).Isolates showing no distortion indicating no significant inactivation of cefoxitin were taken as negative for AmpC production (14).

Results

Out of 244 Pseudomonas aeruginosa strains studied for inducible AmpC β-lactamase production 47 (19.3%) were positive by all the three methods used i.e. Disc antagonism test, (12) MTDT (13) and AmpC disc test (14)(Table/Fig 5) .These 47 Pseudomonas aeruginosa strains were positive by disc antagonism test i.e. screen positive, (Table/Fig 1) which were further confirmed by MTDT (Table/Fig 2) and AmpC disc test (Table/Fig 3),(Table/Fig 4). By MTDT 42 strains showed clear distortion of zone of inhibition and was taken as AmpC β-lactamase producer. 5 strains showed minimal distortion of zone of inhibition and was taken as indeterminate strains (Table/Fig 6) By AmpC disc test 39 strains showed indentation and 8 strains showed flattering of zone of inhibition. All 47 strains were taken as AmpC β-lactamase producer by AmpC disc test. The 5 indeterminate strains showing minimal distortion also showed flattening in AmpC disc test indicating weak AmpC production (Table/Fig 6).

Out of these 244 Pseudomonas aeruginosa strains 218 (89.3%) were isolated from Indoor patients department (IPD) and 26 (10.7%) were from ICU patients. No Pseudomonas aeruginosa strain was isolated from Outdoor patients department (OPD) patients. Out of 47 AmpC β-lactamase producing Pseudomonas aeruginosa strains 2 (4.3%) were from ICU patients. Amongst these 2 ICU patients, from 1 (2.1%) patient, isolated Pseudomonas aeruginosa strain was resistant to all anti-pseudomonal antibiotics studied. Another Pseudomonas aeruginosa strain isolated from ICU patient was also resistant to ciprofloxacin, piperacillin/ tazobactam, aztreonam, cefepime, ceftazidime and netilmicin.

The Pseudomonas aeruginosa strains isolated from different specimens were urine 82 (33.6%), pus 63 (25.9%), sputum 37 (15.1%), blood 12 (5%), endotracheal tube secretion 7 (2.9%), and others 43 (17.6%). Out of 47 AmpC β-lactamase producing Pseudomonas aeruginosa strains 21 (44.7%) strains were isolated from urine followed by 12 (25.5%) from pus and 8 (17%) from sputum respectively (Table/Fig 7).A total number of 225 (92.2%) Pseudomonas aeruginosa strains were sensitive to meropenem and imipenem, followed by 201 (82.4%) strains sensitive to amikacin and 184 (75.4%) strains sensitive to ciprofloxacin(Table/Fig 8).The highest sensitivity pattern observed was Imipenem, Amikacin, and Ciprofloxacin. 19 (7.8%) Pseudomonas aeruginosa strains were resistant to all 9 newer antipseudomonal antibiotics studied, of which 3 (15.8%) strains were AmpC β-lactamase producer.

Discussion

AmpC β-lactamase producing bacteria can cause major therapeutic failure if they remain undetected because in routine Kirby-Bauer Disc diffusion test for antibiotic sensitivity, they may show false sensitivity zone. But the facts is AmpC β-lactamase producing organisms particularly Pseudomonas aeruginosa is on the rise and poses a major therapeutic challenge due to treatment failure (15), and have been responsible for several nosocomial outbreak. The major threat is that E.coli, Klebsiella pneumoniae, Klebsiella oxytoca, Salmonella species can produce plasmid mediated AmpC β-lactamase making most bacterial strains resistant to cefoxitin and other cephalosporins, But most Clinical laboratories and Physicians remain unware of the clinical importance of AmpC β-lactamase producing organism (16). The detection of Extended spectrum β-lactamases (ESBL) in AmpC producing species of Gram negative bacteria is another major problematic area. High level expression of AmpC may prevent recognition of an ESBL specially if inhibitor based approach i.e. clavulanic acid is taken to detect ESBL. The reason is— clavulanic acid may acts as inducer of high level AmpC production in those organisms e.g. Pseudomonas aeruginosa, Serratia, Enterobacter sp. etc, which can produce chromosomally encoded inducible AmpC β-lactamase (9).

But there is a paucity of data regarding inducible AmpC β-lactamase producing Pseudomonas aeruginosa, not only in India but Worldwide also. No Clinical & Laboratory Standards Institute (CLSI) recommendation exists for phenotypic screening or confirmatory tests for inducible AmpC β-lactamase producing bacteria (17). Current detection methods for detecting AmpC β-lactamase producing organisms are technically demanding. Though multiplex PCR has been done, it is not yet available for routine use (16). In the present study we had 19.3% of our Pseudomonas aeruginosa strains which produce AmpC β-lactamase. Our study correlated well with reports from Aligarh by Shahid et al. in 2004 as 20% (17) and from Kolkata by Arora et al. in 2005 as 17.3% (15) and from Varanasi as 22% (18). Bhattacharjee et al. from IMS, BHU has reported that 94% of their Pseudomonas aeruginosa strains were sensitive to Piperacillin/ Tazobactum (18) but in our study only 71.7% strains were sensitive to piperacillin / Tazobactum. In the present study maximum no of strains (92.2%) were sensitive to Meropenem and Imipenem compared to only 86% sensitivity to imipenem in the study conducted in BHU (18).

Amongst the 19 Pseudomonas aeruginosa strains resistant to all newer antipseudomonal antibiotic studied, 3 (15.8%) strains were AmpC β-lactamase producer, and 16 (84.2%) were resistant to all antipseudomonal antibiotics but AmpC β-lactamase negative.

Modified three dimensional test (MTDT) is not feasible to do routinely as it is cumbersome for confirmation of AmpC β-lactamase producer. Compared to MTDT, all (100%) Pseudomonas aeruginosa strains producing AmpC β-lactamase could be detected by AmpC disc test in our study. It should be clarified here that though AmpC disc test was originally introduced to detect plasmid mediated AmpC β-lactamase, Black et al. reported that AmpC disc test detect high level production of chromosomally mediated inducible AmpC β-lactamase in Pseudomonas aeruginosa, Acinetobacter species, Enterobacter cloacae etc (14).

Conclusion

Though specific CLSI guideline is till not available for detection of AmpC β-lactamase, clinical Microbiologists should start screening of AmpC β-lactamase producing bacterial strains to prevent misuse of antibiotics and therapeutic failure. Amongst the different methods available, AmpC disc test is quite easy which can be routinely done to detect AmpC β-lactamase production in any Microbiology Laboratory set up.

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