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   2011| July-September  | Volume 29 | Issue 3  
    Online since August 17, 2011

 
 
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REVIEW ARTICLES
Polymyxins: Antimicrobial susceptibility concerns and therapeutic options
V Balaji, SS Jeremiah, PR Baliga
July-September 2011, 29(3):230-242
DOI:10.4103/0255-0857.83905  PMID:21860102
The increasing prevalence of multidrug-resistant nosocomial pathogens such as Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae poses a great challenge to the treating physicians. The paucity of newer effective antimicrobials has led to renewed interest in the polymyxin group of drugs, as a last resort for treatment of gram-negative bacterial infections. There is a dearth of information on the pharmacological properties of colistin, leading to difficulties in selecting the right dose, dosing interval, and route of administration for treatment, especially in critically-ill patients. The increasing use of colistin over the last few years necessitates the need for accurate and reliable in vitro susceptibility testing methods. Development of heteroresistant strains as a result of colistin monotherapy is also a growing concern. There is a compelling need from the clinicians to provide options for probable and possible colistin combination therapy for multidrug-resistant bacterial infections in the ICU setting. Newer combination drug synergy determination tests are being developed and reported. There are no standardized recommendations from antimicrobial susceptibility testing reference agencies for the testing and interpretation of these drug combinations. Comparison and analysis of these reported methodologies may help to understand and assist the microbiologist to choose the best method that produces accurate results at the earliest. This will help clinicians to select the appropriate combination therapy. In this era of multidrug resistance it is important for the microbiology laboratory to be prepared, by default, to provide timely synergistic susceptibility results in addition to routine susceptibility, if warranted. Not as a favour or at request, but as a responsibility.
  9 13,286 873
Antimicrobial resistance in typhoidal salmonellae
BN Harish, GA Menezes
July-September 2011, 29(3):223-229
DOI:10.4103/0255-0857.83904  PMID:21860101
Infections with Salmonella are an important public health problem worldwide. On a global scale, it has been appraised that Salmonella is responsible for an estimated 3 billion human infections each year. The World Health Organization (WHO) has estimated that annually typhoid fever accounts for 21.7 million illnesses (217,000 deaths) and paratyphoid fever accounts for 5.4 million of these cases. Infants, children, and adolescents in south-central and South-eastern Asia experience the greatest burden of illness. In cases of enteric fever, including infections with S. Typhi and S. Paratyphi A and B, it is often necessary to commence treatment before the results of laboratory sensitivity tests are available. Hence, it is important to be aware of options and possible problems before beginning treatment. Ciprofloxacin has become the first-line drug of choice since the widespread emergence and spread of strains resistant to chloramphenicol, ampicillin, and trimethoprim. There is increase in the occurrence of strains resistant to ciprofloxacin. Reports of typhoidal salmonellae with increasing minimum inhibitory concentration (MIC) and resistance to newer quinolones raise the fear of potential treatment failures and necessitate the need for new, alternative antimicrobials. Extended-spectrum cephalosporins and azithromycin are the options available for the treatment of enteric fever. The emergence of broad spectrum β-lactamases in typhoidal salmonellae constitutes a new challenge. Already there are rare reports of azithromycin resistance in typhoidal salmonellae leading to treatment failure. This review is based on published research from our centre and literature from elsewhere in the world. This brief review tries to summarize the history and recent trends in antimicrobial resistance in typhoidal salmonellae.
  7 12,962 1,433
ORIGINAL ARTICLES
Development of TaqMan real-time polymerase chain reaction for the detection of the newly emerging form of carbapenem resistance gene in clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii
V Manchanda, S Rai, S Gupta, RS Rautela, R Chopra, DS Rawat, N Verma, NP Singh, IR Kaur, P Bhalla
July-September 2011, 29(3):249-253
DOI:10.4103/0255-0857.83907  PMID:21860104
Purpose: The newly emerging form of the so-called New Delhi Metallo-beta-lactamases (NDM-1) has been reported recently from patients worldwide and broadly thought as a potential source for the major global health problem. Thus, it is important to study the epidemiology of the so-called NDM-1 harbouring bacteria to prevent its further spread and to place effective control measures. The present study describes the use of the real-time polymerase chain reaction (PCR) assay for the detection of the bla NDM-1 gene using TaqMan probes among clinical isolates. Materials and Methods: Clinical isolates of Escherichia coli (11 strains), Klebsiella pneumoniae (17 strains) and Acinetobacter baumannii (six strains) that were resistant to either of the carbapenems (meropenem or imipenem) were included in the study. The presence of carbapenemases in such strains was confirmed using the modified Hodge test. A real-time PCR assay was optimized for the detection of NDM-1 using a cloned synthetic gene fragment followed by testing of the clinical isolates. The findings were further confirmed using PCR and gene sequencing. Results: TaqMan probe assay displayed a good detection limit with analytical sensitivity of the assay up to 10 copies of bla NDM-1 gene per reaction. The isolates of E. coli and K. pneumoniae revealed narrow range crossing point values (Cp values) between (12-17) cycles (mean Cp value 14), indicating number of bla NDM-1 gene copies of 106-108. The wider range of Cp values (15-34) cycles with a higher mean Cp value (23.6) was observed in A. baumannii with number of bla NDM-1 gene copies of 103-108. Conclusions: The study demonstrates that real-time PCR assay based on TaqMan chemistry is a useful technique for the detection of bla NDM-1 harbouring clinical isolates of E. coli, K. pneumoniae and A. baumannii. The assay has great precision in measuring the number of bla NDM-1 gene copies per specimen of DNA.
  6 5,599 411
REVIEW ARTICLES
Drug resistance in malaria
SC Parija, I Praharaj
July-September 2011, 29(3):243-248
DOI:10.4103/0255-0857.83906  PMID:21860103
Antimalarial chemotherapy is an important component of all malaria control programmes throughout the world. This is especially so in light of the fact that there are no antimalarial vaccines which are available for clinical use at present. Emergence and spread of malaria parasites which are resistant to many of the available antimalarials today is, therefore, a major cause for concern. Till date, resistance to all groups of antimalarials excluding artemisinin has been reported. In recent years, in vitro resistance to even artemisinin has been described. While resistance to antibacterial agents has come to prominence as a clinical problem in recent years, antiparasitic resistance in general and antimalarial resistance in particular has not received much attention, especially in the Indian scenario. The present review deals with commonly used antimalarial drugs and the mechanisms of resistance to them. Various methods of detecting antimalarial resistance and avoiding the same have also been dealt with. Newer parasite targets which can be used in developing newer antimalarial agents and antimalarials obtained from plants have also been mentioned.
  6 7,796 917
Antibiotic resistance in ocular bacterial pathogens
S Sharma
July-September 2011, 29(3):218-222
DOI:10.4103/0255-0857.83903  PMID:21860100
Bacterial infections of the eye are common and ophthalmologists are spoilt for choice with a variety of antibiotics available in the market. Antibiotics can be administered in the eye by a number of routes; topical, subconjunctival, subtenon and intraocular. Apart from a gamut of eye drops available, ophthalmologists also have the option of preparing fortified eye drops from parenteral formulations, thereby, achieving high concentrations; often much above the minimum inhibitory concentration (MIC), of antibiotics in ocular tissues during therapy. Antibiotic resistance among ocular pathogens is increasing in parallel with the increase seen over the years in bacteria associated with systemic infections. Although it is believed that the rise in resistant ocular bacterial isolates is linked to the rise in resistant systemic pathogens, recent evidence has correlated the emergence of resistant bacteria in the eye to prior topical antibiotic therapy. One would like to believe that either of these contributes to the emergence of resistance to antibiotics among ocular pathogens. Until recently, ocular pathogens resistant to fluoroquinolones have been minimal but the pattern is currently alarming. The new 8-fluoroquinolone on the scene-besifloxacin, is developed exclusively for ophthalmic use and it is hoped that it will escape the selective pressure for resistance because of lack of systemic use. In addition to development of new antibacterial agents, the strategies to halt or control further development of resistant ocular pathogens should always include judicious use of antibiotics in the treatment of human, animal or plant diseases.
  5 7,184 561
BRIEF COMMUNICATIONS
Species distribution and anti-fungal susceptibility of Candidaemia at a multi super-specialty center in Southern India
R Adhikary, S Joshi
July-September 2011, 29(3):309-311
DOI:10.4103/0255-0857.83920  PMID:21860117
Candidaemia is one of the leading causes of nosocomial bloodstream infections. There is a rise in the incidence of non-albicans candidaemia and emergence of anti-fungal resistance. We performed a retrospective laboratory-based study over a period of 2 years (January 2009 to December 2010) at our quaternary care multi super-specialty hospital in Southern India. There had been 68 Candida isolates detected from the bloodstream of 55 patients during the study period. Overall, 74% of cases were due to non-albicans Candida. C. tropicalis was most commonly isolated (39.7%), followed by C. albicans (26.4%). All Candida isolates remain susceptible to voriconazole, whereas highest degree of resistance was observed for fluconazole.
  4 3,515 573
ORIGINAL ARTICLES
Identification of plasmid-mediated quinolone resistance genes qnrA1, qnrB1 and aac(6')-1b-cr in a multiple drug-resistant isolate of Klebsiella pneumoniae from Chennai
H Magesh, C Kamatchi, R Vaidyanathan, G Sumathi
July-September 2011, 29(3):262-268
DOI:10.4103/0255-0857.83910  PMID:21860107
Purpose: Resistance to fluoroquinolones, a commonly prescribed antimicrobial for Gram-negative and Gram-positive microorganisms, is of importance in therapy. The purpose of this study was to screen for the presence of Plasmid-Mediated Quinolone Resistance (PMQR) determinants in clinical isolates of Klebsiella pneumoniae. Materials and Methods: Extended-Spectrum Beta-Lactamase (ESBL) isolates of K. pneumoniae collected during October 2009 were screened by the antimicrobial susceptibility test. The plasmids from these isolates were analysed by specific Polymerase chain Reaction (PCR) for qnrA, qnrB and aac(6')-1b. The amplified products were sequenced to confirm the allele. Results: Our analysis showed that 61% out of the 23 ESBL K. pneumoniae isolates were resistant to ciprofloxacin and 56% to levofloxacin. The PMQR was demonstrated by transforming the plasmids from two isolates P12 and P13 into E. coli JM109. The PMQR gene qnrA was found in 16 isolates and qnrB in 11 isolates. The plasmid pKNMGR13 which conferred an minimum inhibitory concentration (MIC) of more than 240 ΅g/ml in sensitive E. coli was found to harbour the qnrA1 and qnrB1 allele. Furthermore, the gene aac(6')-1b-cr encoding a variant aminoglycoside 6'-N Acetyl transferase which confers resistance to fluoroquinolones was found in the same plasmid. Conclusions: Our report shows the prevalence of PMQR mediated by qnrA and qnrB in multidrug-resistant K. pneumoniae isolates from Chennai. A multidrug-resistant plasmid conferring high resistance to ciprofloxacin was found to harbour another PMQR gene, aac(6')-1b-cr mutant gene. This is the first report screening for PMQR in K. pneumoniae isolates from India.
  3 4,439 281
OXA beta-lactamase-mediated carbapenem resistance in Acinetobacter baumannii
SM Amudhan, U Sekar, K Arunagiri, B Sekar
July-September 2011, 29(3):269-274
DOI:10.4103/0255-0857.83911  PMID:21860108
Objectives: Acinetobacter baumannii is a significant pathogen in health care settings. In recent years, an increase in carbapenem resistance among A. baumannii due to Ambler class B metallo-beta-lactamases or class D OXA carbapenamases has been reported. In this study we detected the presence of OXA carbapenamases and coproduction of metallo-beta-lactamases (blaVIM and blaIMP ) by phenotypic and genotypic methods in carbapenem resistant clinical isolates of Acinetobacter baumannii. Materials and Methods: A total of 116 consecutive, non-duplicate carbapenem resistant A. baumannii isolated from various clinical specimens were included in the study. The modified Hodge test and inhibitor potentiated disk diffusion tests were done for the screening of carbapenamase and metallo-beta-lactamase production, respectively. Polymerase chain reaction (PCR) was performed for the detection of OXA (blaOXA 23 like, blaOXA 24 like, blaOXA-51 like and blaOXA-58 like genes) and metallo-beta-lactamases (blaVIM and blaIMP ) genes. Gene sequencing was performed for representative isolates. Results: Among 116 A. baumannii, OXA genes were detected in 106 isolates. BlaOXA 51 like (n = 99) and blaOXA -23 like (n = 95) were the most common and they coexisted in 89 isolates. blaOXA-24 like gene was detected in two isolates of which one also carried blaOXA-51 like and blaOXA-58 like genes. The modified Hodge test was positive in 113 isolates. The metallo-beta-lactamase screening test was positive in 92 isolates. blavim was detected in 54 isolates of which 1 also carried the blaIMP gene. Conclusions: blaOXA-23 like and bla OXA 51 like genes are the most common types of OXA carbapenamases while the blaVIM type is the most common type of metallo-beta-lactamase contributing to carbapenem resistance in clinical isolates of A. baumannii. The coproduction of OXA and metallo-beta-lactamases is not an uncommon phenomenon in A. baumannii.
  3 9,879 614
Assessment of trends of ofloxacin resistance in Mycobacterium tuberculosis
JS Verma, D Nair, D Rawat, N Manzoor
July-September 2011, 29(3):280-282
DOI:10.4103/0255-0857.83913  PMID:21860110
Purpose: Ofloxacin (OFX) is one of the potent fluoroquinolone (FQ) recommended to treat MDR-TB. Over a decade, the preexposure of this drug for the treatment of other bacterial infections has resulted in acquisition of FQ resistance among Mycobacterium tuberculosis strains. Considering this possibility, a study was undertaken in a tertiary care center in the capital city (India) to assess the drug resistance trends of OFX among susceptible and multidrug resistant (MDR) strains of M. tuberculosis. Materials and Methods: A total of 102 M. tuberculosis isolates (47 susceptible to first-line drugs and 55 MDR isolates) were screened for susceptibility testing of OFX with a critical concentration of 2 μg/ml by Lowenstein Jensen (LJ) proportion method. Results: The results showed 40 (85.1%) isolates among 47 susceptible isolates and 34 (61.8%) isolates among 55 MDR isolates, were found to be susceptible to OFX. Fisher's exact test showed significant P-value (0.0136) demonstrating 1.377 fold (95% confidence interval) increased risk to become resistant to OFX than susceptible isolates. These finding shows decreased OFX susceptibility is not only limited to MDR isolates but also increasingly seen in susceptible strains as a result of drug abuse. Conclusions: Our finding were not alarming, but highlights the general risk of acquiring resistance to OFX, jeopardizing the potential for these drugs to be used as second-line anti-TB agents in the management of drug-resistant TB and creating incurable TB strains .
  2 2,523 253
BRIEF COMMUNICATIONS
CTX-M-9 group extended-spectrum β-lactamases in neonatal stool isolates: Emergence in India
S Roy, S Mukherjee, AK Singh, S Basu
July-September 2011, 29(3):305-308
DOI:10.4103/0255-0857.83919  PMID:21860116
The study reports for the first time the identification of CTX-M-14-like and CTX-M-27-like extended-spectrum β-lactamases (ESBLs) belonging to the CTX-M-9 group in Klebsiella pneumoniae and Escherichia coli isolated from the neonatal stool in India. The plasmid carrying the blaCTX-M-9 group in both the isolates was transferable. Till date, no other CTX-M group, except the CTX-M-1 group, has been reported from India. A total of 77% of the neonates had ESBL-producing K. pneumoniae or E. coli in their stool, and blaCTX-M-15 was the predominant ESBL gene. Although the CTX-M-9 group was found in the stool and did not cause infection, the detection of the CTX-M-9 group might be a prelude to future infections.
  1 3,459 201
CORRESPONDENCES
High oxacillin, vancomycin and fluoroquinolone resistance amongst biofilm forming Staphylococcus aureus isolates from ulcerative keratitis infections
S Singh, R Katiyar, SD Kaistha
July-September 2011, 29(3):312-313
DOI:10.4103/0255-0857.83921  PMID:21860118
  1 2,267 240
Linezolid-resistant Staphylococcus spp. at a tertiary care hospital of Andhra Pradesh
U Kalawat, KK Sharma, S Reddy
July-September 2011, 29(3):314-315
DOI:10.4103/0255-0857.83923  PMID:21860120
  1 2,405 279
ORIGINAL ARTICLES
Direct inoculation on Phoenix panels for identification and antimicrobial susceptibility from positive BACTEC cultures: First study from India
S Duggal, SK Jesaiwal, N Tandon, TD Chugh
July-September 2011, 29(3):283-287
DOI:10.4103/0255-0857.83914  PMID:21860111
Purpose: This was a prospective study planned in a super-specialty hospital in Delhi to reduce turnaround times of identification-susceptibility results of positive blood cultures. Materials and Methods: One hundred consecutive single morphology non-duplicate cultures were inoculated on Becton Dickinson Phoenix™ panels by growth recovered directly from liquid BACTEC™ media and after pure growth on solid media. Results: Complete concordance was observed in 72.4% of gram-negative and 45.8% of gram-positive isolates. For gram-negative isolates, categorical agreement (CA) was >83% and essential agreement (EA) was >96% among all antibiotics tested, very major errors (VME) were 0.13%, major errors (ME) 0.54%, and minor errors (MiE) were 3.01%. For gram-positive isolates, VME was 0.73%, 1.10% MiE and no ME. It was observed that average time from receipt of specimen to release of reports was 30:34 h and 32 h for gram-negative and gram-positive isolates if reports of "Direct" panels were to be released. Conclusions: By direct panel inoculation, a decrease of at least 18-20 h in turnaround time was observed compared with the standard method. This helps early change to effective antibiotic therapy and also reduces the expenditure incurred for a patient's hospital stay by average Rs 20,000 ($443) per day.
  1 2,387 184
Investigation of Ureaplasma urealyticum biovars and their relationship with antimicrobial resistance
Zhu Chang-tai, Hu Zhong-yi, Dong Chun-lei, Zhang Chang-song, Wan Mei-zhen, Ling Yang
July-September 2011, 29(3):288-292
DOI:10.4103/0255-0857.83915  PMID:21860112
Purpose: To develop Taqman fluorescence quantitative polymerase chain reaction (PCR) method for investigating the characteristics of the distributions of Ureaplasma urealyticum (UU) biovars and to explore the relationship between UU biovars and antimicrobial resistance. Materials and Methods: By the method of culture, Ureaplasma species were detected. Taqman fluorescence quantitative PCR for detecting UU biovars were developed and UU clinical isolates were detected to distinguish biovars. The broth micro-dilution susceptibility testing methods were used to determine UU susceptibility. Results: By Taqman PCR method, UU biovars was successfully detected. Of 126 samples, biovar 1 was found in 73 (57.94%). There was a statistical difference between genital-urinary tract infection group and asymptomatic group (P<0.05). In the region, UU biovar 1 to 9 kinds of agents kept higher susceptibility rates, but biovar 2 maintained higher susceptibility rates only to tetracyclines. Compared with biovar 1, UU biovar 2 resistance rates to 7 kinds of agents were higher (P<0.05). Conclusions: (1) Our new established Taqman PCR method is a useful tool for screening UU biovars. (2) UU biovar 1 predominated in asymptomatic population; whereas in genital-urinary tract infection population UU biovar 2 had a higher proportion. (3) The characteristics of drug resistance were different between UU biovars. Overall, both two biovars remained higher susceptibility rates to tetracyclines. A majority of biovor 1 strains were sensitive to macrolides and quinolones; while only a small number of biovar 2 strains kept sensitive to roxithromycin and quinolones, a large proportion of biovar 2 strains were found in intermediate ranges.
  1 4,165 126
First detection of TEM-116 extended-spectrum β-lactamase in a Providencia stuartii isolate from a Tunisian hospital
H Lahlaoui, S Dahmen, MB Moussa, B Omrane
July-September 2011, 29(3):258-261
DOI:10.4103/0255-0857.83909  PMID:21860106
Purpose: To study the resistance to third-generation cephalosporins in Providencia stuartii strain isolated from hospitalized patient in Tunisia and to identify the responsible genes Materials and Methods: This strain was analysed by PCR and sequencing to identify the genes responsible for the β-lactamase resistance phenotypes. The transferability of the phenotypes was tested by conjugation to Escherichia coli J53. The isoelectric point was determinate by isoelectrofocalisation. Results: This resistance was carried by a 60 kb plasmid that encoded a β-lactamase with a pI of 5.4. This β-lactamase revealed identity with the blaTEM-1 gene encoding the TEM-1 β-lactamase, except for a replacement of the Val residue at position 84 by Ile, and the Ala residue at position 184 by Val. These two mutations were encountered in TEM-116 β-lactamase. Conclusion: This study demonstrates the first description of TEM-116 in the P. stuartii species in the world and the first one in a Tunisian hospital.
  1 2,766 140
BRIEF COMMUNICATIONS
Metallo beta lactamase producing Pseudomonas aeruginosa and Acinetobacter baumannii
S John, R Balagurunathan
July-September 2011, 29(3):302-304
DOI:10.4103/0255-0857.83918  PMID:21860115
This study aims in identifying MBLs particularly Zn requiring Molecular Class B enzymes produced by Pseudomonas aeruginosa and Acinetobacter baumannii .The resistance by these organisms are in a rise against all antibiotics including carbapenems and no prescribed CLSI guidelines is available for detecting them. Clinical isolates antibiotic susceptibility was determined by number of phenotypic tests by addition of 50mM of 10 μl zinc as cofactor for metallo beta lactamase production along with 0.5M ETDA of 5μl (930 μg per disk) plain disks. Increase in zone size of the meropenem -EDTA disk compared to the meropenem disk without EDTA was recorded positive. For Zn requiring MBLs zone towards both disks of EDTA and Zn along with meropenem is detected by DDST.
  - 7,603 687
CORRESPONDENCES
Glycopeptides-Important treatment option for methicillin-resistant Staphylococcus aureus
S Arora, U Arora
July-September 2011, 29(3):313-314
DOI:10.4103/0255-0857.83922  PMID:21860119
  - 1,721 197
Newer β-lactam and β-lactamase inhibitor combinations available in India: Consensus and controversies
B Veeraraghavan
July-September 2011, 29(3):315-316
DOI:10.4103/0255-0857.83924  PMID:21860121
  - 1,984 272
Penicillin resistant Streptococcus pneumoniae in India: Effects of new clinical laboratory standards institute breakpoint and implications
B Veeraraghavan, T Kurien
July-September 2011, 29(3):317-318
DOI:10.4103/0255-0857.83925  PMID:21860122
  - 2,681 273
Antibiotic resistance and molecular subtypes of clinical methicillin-resistant Staphylococcus aureus in a teaching hospital
E Zeinali, R Moniri, GH Musavi
July-September 2011, 29(3):318-319
DOI:10.4103/0255-0857.83926  PMID:21860123
  - 2,009 294
EDITORIAL
Antimicrobial resistance: Action by laboratories today for a cure tomorrow
R Kanungo
July-September 2011, 29(3):205-206
DOI:10.4103/0255-0857.83899  PMID:21860096
  - 2,866 540
GUEST EDITORIAL
Antimicrobial resistance and extinction
P Desikan
July-September 2011, 29(3):207-208
DOI:10.4103/0255-0857.83900  PMID:21860097
  - 2,397 345
ORIGINAL ARTICLES
Molecular characterization of CTX-M β-lactamases among Klebsiella pneumoniae isolated from patients at Tehran hospitals
N Shoeib, S Fereshteh, FM Mehdi, NV Sadat, N Leila
July-September 2011, 29(3):254-257
DOI:10.4103/0255-0857.83908  PMID:21860105
Purpose: Plasmid-encoded CTX-M-group of extended-spectrum β-lactamases (ESBLs) represent a significant and rapidly emerging problem in most part of the world. The aim of the present study was to describe the prevalence of CTX-M producing Klebsiella pneumoniae at Tehran hospitals. Materials and Methods: Clinical isolates of K. pneumoniae (n=250) were collected from 10 hospitals of Tehran. Susceptibility to antimicrobial agents, MIC of cefotaxime and ESBLs production of collected isolates were detected. All ESBL-producing isolates were screened for bla CTX-M genes using PCR and DNA sequencing. Molecular typing of bla CTX-M harboring isolates was performed by Pulsed-field gel electrophoresis assay. Results: Of 250 K. pneumoniae clinical isolates, 102 isolates revealed ESBLs - phenotype. PCR assay and sequencing detected bla CTX-M genes in 71.5% (n= 73) of ESBL-producing isolates. The prevalence of CTX-M -I and CTX-M-III clusters among these isolates was 35.61% (n=26) and 21.9 % (n=16) respectively. Coexistence of CTX-M -I and CTX-M-III clusters was found among 42.5% (n= 31) of isolates. Of 102 isolates that were positive in the phenotypic confirmatory test (PCT), 29 isolates (28.4%) did not produce any amplicons in PCR for bla CTX-M gene. The results of PCR for CTX-M -II and CTX-M-IV clusters were also negative. Analysis of the 31 CTX-M producing K. pneumoniae isolates by PFGE typing showed 26 distinct patterns. Conclusions: The bla CTX-M genes are widespread among Iranian isolates of K. pneumoniae. PFGE demonstrated the high diversity of K. pneumoniae harboring bla CTX-M in our study.
  - 3,316 235
Zinc-dependent carbapenemases in clinical isolates of family Enterobacteriaceae
S Rai, V Manchanda, NP Singh, IR Kaur
July-September 2011, 29(3):275-279
DOI:10.4103/0255-0857.83912  PMID:21860109
Purpose: The emergence and spread of zinc-dependent carbapenem resistance has become a diagnostic challenge for clinical microbiologists. The objective of the present study was to screen zinc-dependent carbapenemase activity in clinical isolates of family Enterobacteriaceae. Materials and Methods: A total of 102 multidrug-resistant organisms (MDROs), non-repeat clinical isolates of family Enterobacteriaceae from two tertiary care centres in Delhi, were screened for carbapenemase production by a modified Hodge test (MHT) and additionally by a re-modified Hodge test, EDTA double disc synergy test, and combined disc test (or disc enhancement test) to determine zinc dependence of carbapenemases harbouring bacteria. Results: Of the total 102 clinical isolates (June through November 2010), 91 were from urine and 11 were from blood specimens. The isolates were obtained from patients visiting the outpatient department (18 isolates), admitted in non-ICU inpatient care units (74 isolates) and patients admitted in ICUs (4 isolates). MHT identified 92 (90.2%) isolates as carbapenemases producers. Among those found negative for MHT (n=10), metallo-beta-lactamases (MBLs) activity was demonstrated through the EDTA disc diffusion synergy test and the combined disc test in 8 and 9 isolates respectively. A total of 63 (61.7%) isolates demonstrated MBL activity despite in vitro sensitivity to Imipenem. Conclusions: The study demonstrated that supplementing the MHT with at least one of the screening methods increases the likelihood of picking up such isolates that may be missed by the MHT. The study also demonstrates the wide-spread presence of MBLs in Enterobacteriaceae members from patients visiting hospitals in east Delhi.
  - 7,363 616
Comparison between the two-step and the three-step algorithms for the detection of toxigenic Clostridium difficile
MO Qutub, N AlBaz, P Hawken, A Anoos
July-September 2011, 29(3):293-296
DOI:10.4103/0255-0857.83916  PMID:21860113
Purpose: To evaluate usefulness of applying either the two-step algorithm (Ag-EIAs and CCNA) or the three-step algorithm (all three assays) for better confirmation of toxigenic Clostridium difficile. The antigen enzyme immunoassays (Ag-EIAs) can accurately identify the glutamate dehydrogenase antigen of toxigenic and nontoxigenic Clostridium difficile. Therefore, it is used in combination with a toxin-detecting assay [cell line culture neutralization assay (CCNA), or the enzyme immunoassays for toxins A and B (TOX-A/BII EIA)] to provide specific evidence of Clostridium difficile-associated diarrhoea. Materials and Methods: A total of 151 nonformed stool specimens were tested by Ag-EIAs, TOX-A/BII EIA, and CCNA. All tests were performed according to the manufacturer's instructions and the results of Ag-EIAs and TOX-A/BII EIA were read using a spectrophotometer at a wavelength of 450 nm. Results: A total of 61 (40.7%), 38 (25.3%), and 52 (34.7%) specimens tested positive with Ag-EIA, TOX-A/BII EIA, and CCNA, respectively. Overall, the sensitivity, specificity, negative predictive value, and positive predictive value for Ag-EIA were 94%, 87%, 96.6%, and 80.3%, respectively. Whereas for TOX-A/BII EIA, the sensitivity, specificity, negative predictive value, and positive predictive value were 73.1%, 100%, 87.5%, and 100%, respectively. With the two-step algorithm, all 61 Ag-EIAs-positive cases required 2 days for confirmation. With the three-step algorithm, 37 (60.7%) cases were reported immediately, and the remaining 24 (39.3%) required further testing by CCNA. By applying the two-step algorithm, the workload and cost could be reduced by 28.2% compared with the three-step algorithm. Conclusions: The two-step algorithm is the most practical for accurately detecting toxigenic Clostridium difficile, but it is time-consuming.
  - 2,714 195
Comparison of the boronic acid disk potentiation test and cefepime-clavulanic acid method for the detection of ESBL among AmpC-producing Enterobacteriaceae
RM Shoorashetty, T Nagarathnamma, J Prathibha
July-September 2011, 29(3):297-301
DOI:10.4103/0255-0857.83917  PMID:21860114
Purpose: Extended spectrum β-lactamase (ESBL) and AmpC β-lactamase are important mechanisms of betalactam resistance among Enterobacteriaceae . The ESBL confirmation test described by Clinical Laboratory Standards Institute (CLSI) is in routine use. This method fails to detect ESBL in the presence of AmpC. Therefore, we compared two different ESBL detection methods against the CLSI confirmatory test. Materials and Methods: A total 200 consecutive clinical isolates of Enterobacteriaceae from various clinical samples were tested for ESBL production using (i) CLSI described phenotypic confirmatory test (PCT), (ii) boronic acid disk potentiation test and (iii) cefepime-CA disk potentiation method. AmpC confirmation was done by a modified three-dimensional test. Results: Among total 200 Enterobacteriaceae isolates, 82 were only ESBL producers, 12 were only AmpC producers, 55 were combined ESBL and AmpC producers, 14 were inducible AmpC producers and 37 isolates did not harboured any enzymes. The CLSI described PCT detected ESBL-producing organisms correctly but failed to detect 36.3% of ESBLs among combined enzyme producers. The boronic acid disk potentiation test reliably detected all ESBL, AmpC, and combined enzyme producers correctly. The cefepime-CA method detected all ESBLs correctly but another method of AmpC detection has to be adopted. Conclusion: The use of boronic acid in disk diffusion testing along with the CLSI described PCT enhances ESBL detection in the presence of AmpC betalactamases.
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RESEARCH SNIPPETS
Snippets
P Desikan
July-September 2011, 29(3):320-321
  - 1,227 118
REVIEW ARTICLES
Is screening patients for antibiotic-resistant bacteria justified in the Indian context?
S Bhattacharya
July-September 2011, 29(3):213-217
DOI:10.4103/0255-0857.83902  PMID:21860099
Infection with multi-antibiotic-resistant bacteria is a common clinical problem in India. In some countries and centres, screening patients to detect colonisation by these organisms is used to determine specific interventions such as decolonisation treatment, prophylactic antibiotics prior to surgical interventions or for selection of empirical antibiotic therapy, and to isolate patients so that transmission of these difficult to treat organisms to other patients could be prevented. In India, there is no national guideline or recommendation for screening patients for multi-drug-resistant (MDR) bacteria such as MRSA (methicillin-resistant Staphylococcus aureus), VRE (vancomycin-resistant enterococcus), ESBL (extended spectrum beta-lactamase) or MBL (metallo-beta-lactamase) producers. The present article discusses the relevance of screening patients for multi-antibiotic-resistant bacteria in the Indian context. Literature has been reviewed about antibiotic resistance in India, screening methodology, economic debate about screening. The percentages of strains from various hospitals in India which were reported to be MRSA was between 8 and 71%, those for ESBL between 19 and 60% and carbapenem-resistant Gram-negative bacilli between 5.3 and 59%. There exists culture-based technology for the detection of these resistant organisms from patient samples. For some pathogens, such as MRSA and VRE Polymerase chain reaction-based tests are also becoming available. Screening for MDR bacteria is an option which may be used after appraisal of the resources available, and after exploring possibility of implementing the interventions that may be required after a positive screening test result.
  - 4,825 617
SPECIAL ARTICLE
Towards a rational antimicrobial testing policy in the laboratory
N Banaji, S Oommen
July-September 2011, 29(3):209-212
DOI:10.4103/0255-0857.83901  PMID:21860098
Antimicrobial policy for prophylactic and therapeutic use of antimicrobials in a tertiary care setting has gained importance. A hospital's antimicrobial policy as laid down by its hospital infection control team needs to include inputs from the microbiology laboratory, besides the pharmacy and therapeutic committee. Therefore, it is of utmost importance that clinical microbiologists across India follow international guidelines and also take into account local settings, especially detection and presence of resistance enzymes. This article draws a framework for rational antimicrobial testing in our laboratories in tertiary care centers, from the Clinical and Laboratory Standards Institute guidelines. It does not address testing methodologies but suggests ways and means by which antimicrobial susceptibility reporting can be rendered meaningful not only to the treating physician but also to the resistance monitoring epidemiologist. It hopes to initiate some standardization in rational choice of antimicrobial testing in laboratories in the country pertaining to nonfastidious bacteria.
  - 3,294 585

2004 - Indian Journal of Medical Microbiology
Published by Wolters Kluwer - Medknow

Online since April 2001, new site since 1st August '04