Amikacin Resistance Research Articles

Occurrence and mechanisms of amikacin resistance and its association with β-lactamases in Pseudomonas aeruginosa: a Korean nationwide study

We investigated the occurrence and mechanism of amikacin resistance and its association with various beta-lactamase genes in Pseudomonas aeruginosa isolates. Of the total 250 consecutive, non-duplicated isolates of P. aeruginosa, 55 isolates showed amikacin resistance. PCR amplification of genes for aminoglycoside (AG)-modifying enzymes [aac(3)-I, aac(3)-II/VI, aac(3)-III/IV, aac(6')-I, aac(6')-II, ant(2'')-I, ant(4')-II and aph(3')-VI], 16S rRNA methylases (rmtA, rmtB, rmtC and armA) and class 1 integrons was performed. In addition, we analysed the association of AG resistance genes with various beta-lactamase genes. In Korea, the amikacin resistance rate in P. aeruginosa was high (22%), and it varied among provinces (3.8% to 40%). Four types of AG-modifying enzyme genes [aph(3')-VI, ant(2'')-I, aac(6')-I and aac(3)-II/VI] were found in 48 isolates. Thirty-six strains harboured two or more types of enzymes, of which a combination of aph(3')-VI and ant(2'')-I was the most frequent (24/36 isolates, 66.7%). None harboured aac(3)-I, aac(3)-III/IV, aac(6')-II, ant(4')-II, rmtA, rmtB, rmtC or armA. Forty-two isolates co-harboured beta-lactamase genes (mostly bla(OXA-10)). A class 1 integron was detected in all but one, and all the ant(2'')-I and 26/29 bla(OXA-10) were found in it. In contrast, aph(3')-VI was not found to be associated with the class 1 integron. Considering the possibility of co-selection and dissemination, constant monitoring of resistance evolution is necessary.

Differential Correlation Between Rates of Antimicrobial Drug Consumption and Prevalence of Antimicrobial Resistance in a Tertiary Care Hospital in Greece

To investigate whether there is a correlation between the rates of antimicrobial drug consumption in hospital departments and the prevalence of antimicrobial resistance among clinically important bacteria recovered in the hospital. Retrospective study. Tertiary care hospital in Greece. Data on antimicrobial consumption (from January 2001 through December 2004) were expressed as defined daily doses per 100 bed-days. The prevalence of antimicrobial resistance among isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterococcus faecium recovered during the same time period were calculated by the microbiology department. We then performed the following analyses: (1) a comparison of the consumption rates for different antimicrobial groups in individual hospital departments, (2) a comparison of the prevalence of resistance to different antimicrobials, and (3) a correlation analysis of antimicrobial consumption rates and the prevalence of antimicrobial resistance. The rates of antimicrobial consumption and the prevalence of resistance varied substantially among the hospital's departments. The annual rate of consumption for carbapenems correlated with the rate of consumption for glycopeptides and third-generation cephalosporins (P < .05). Among P. aeruginosa isolates, the prevalence of imipenem resistance correlated with the prevalence of resistance to amikacin, ciprofloxacin, and ceftazidime (P < .05). The rate of carbapenem consumption correlated with the prevalence of imipenem resistance among P. aeruginosa and A. baumannii isolates (P < .05). The rate of aminoglycoside consumption correlated with the prevalence of amikacin resistance among P. aeruginosa, K. pneumoniae, and E. coli isolates (P < .05). However, the rate of consumption for fluoroquinolones and glycopeptides had no correlation with the prevalence of ciprofloxacin resistance among gram-negative bacteria or vancomycin resistance among E. faecium isolates. These data are suggestive of a differential relationship between antimicrobial consumption and the prevalence of antimicrobial resistance among various species and for various antimicrobial agents. These findings may help to optimize antimicrobial prescription policies in the hospital, especially in departments that have both high rates of antimicrobial consumption and a high prevalence of antimicrobial resistance.

Appearance of aac(6′)-Ib-cr gene among extended-spectrum β-lactamase-producing Enterobacteriaceae in a French hospital

The aac(6')-Ib gene encodes many variants of an aminoglycoside-acetyltransferase enzyme that is responsible for amikacin resistance. Recently, a new variant aac(6')-Ib-cr capable of modifying aminoglycosides and fluoroquinolones has been described. The aim of our study was to observe the appearance and the location of the aac(6')-Ib gene in extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae strains. Sixty-six and nine non-clonal ESBL-producing Enterobacteriaceae strains were isolated, respectively, for one 3-year period from 1999 to 2001 and one 2-month period in 2005 in a French Hospital (Paris, France). Among these isolates, 35 of them carried the aac(6')-Ib gene. Fourteen out of the aac(6')-Ib genes of the period 1 and two of the period 2 were genes cassette located within class 1 integrons, whereas 16 and 3, respectively, were outside integrons. One of these encoded an aminoglycoside-acetyltransferase enzyme leading to an acetyltransferase that confers resistance to all aminoglycosides. The new -cr variant of aac(6')-Ib was detected in three Escherichia coli isolates in 2005 always associated with CTX-M-15 enzyme. The aac(6')-Ib-cr gene, responsible for antibiotic resistance to two very different drugs, is emerging in ESBL-producing Enterobacteriaceae strains isolated in France especially in strains carrying the bla(CTx-M-15) gene.

Nocardia wallacei sp. nov. and Nocardia blacklockiae sp. nov., Human Pathogens and Members of the “ Nocardia transvalensis Complex”

Nocardia isolates that share the property of in vitro amikacin resistance are grouped together by some authors in the Nocardia transvalensis complex. Our examination of 13 isolates that are amikacin resistant has revealed the existence of three distinct species. Sequence analysis of the 16S rRNA, 65-kDa heat shock protein, and secA1 genes, coupled with DNA-DNA hybridization, indicated that "N. asteroides drug pattern IV," "N. transvalensis new taxon 1," and N. transvalensis sensu stricto should each be considered a distinct species. The phenotypic and molecular characteristics of the proposed new species Nocardia wallacei (N. asteroides drug pattern IV) and N. blacklockiae (N. transvalensis new taxon 1) are presented and compared with those of N. transvalensis sensu stricto. The relative genetic diversity of isolates best placed with the species N. blacklockiae is also discussed. Case studies demonstrating the pathogenicity of N. wallacei and N. blacklockiae are presented. The type strain of N. wallacei is ATCC 49873 (DSM 45136), and that of N. blacklockiae is ATCC 700035 (DSM 45135).

Distribution of Conjugative-Plasmid-Mediated 16S rRNA Methylase Genes among Amikacin-Resistant Enterobacteriaceae Isolates Collected in 1995 to 1998 and 2001 to 2006 at a University Hospital in South Korea and Identification of Conjugative Plasmids Mediating Dissemination of 16S rRNA Methylase

The distribution of conjugative-plasmid-mediated 16S rRNA methylase genes among amikacin-resistant Enterobacteriaceae collected between 1995 and 1998 and between 2001 and 2006 at a university hospital in South Korea was examined, and conjugative plasmids carrying the 16S rRNA methylase genes were characterized by PCR-based replicon typing and by determination of their antimicrobial resistance pattern. Among the 7,127 isolates, 463 isolates showed a high level of resistance to amikacin, and 218 of the 463 isolates transferred amikacin resistance by conjugation. Among the 218 isolates, armA was detected in 153 isolates (88 Klebsiella pneumoniae, 28 Escherichia coli, 19 Enterobacter cloacae, and 6 Serratia marcescens isolates and 12 isolates of other organisms), and rmtB was detected in 51 isolates (32 K. pneumoniae isolates, 18 E. coli isolates, and 1 Citrobacter freundii isolate). The first appearance of armA was in 1997. The armA gene was carried by conjugative plasmids of replicon groups IncL/M, IncFIIAs, IncF, IncA/C, IncHI2, and Inc(unidentified) in 38, 20, 7, 9, 4, and 75 strains, respectively. The rmtB gene was carried by conjugative plasmids of groups IncA/C, IncF, and IncI1-Igamma in 43 strains, 7 strains, and 1 strain, respectively. Transconjugants that received the IncL/M plasmid carrying armA or the IncA/C plasmid carrying rmtB showed an additional resistance to cefotaxime. Transconjugants that received the IncFIIA plasmid or Inc(unidentified) plasmid carrying the armA gene showed an additional resistance to cefoxitin and a high MIC(50) (0.25 mg/liter) of ciprofloxacin. In conclusion, this study demonstrated that the dissemination of 16S rRNA methylase genes among the Enterobacteriaceae is mediated by conjugative plasmids of various incompatibility groups that confer resistance to multiple drugs, including aminoglycosides, extended-spectrum beta-lactams, and/or quinolones.

Short-term effect of antibiotic control policy on the usage patterns and cost of antimicrobials, mortality, nosocomial infection rates and antibacterial resistance

In 2003 Turkish government released a new budget application instruction for regulating the usage of parenteral antibiotics inside and outside of the hospitals. In this study it was aimed to evaluate the effect of this instruction on the overall usage of restricted antibiotics, their cost, overall mortality, bacterial resistance patterns and nosocomial infection rates in intensive care units (ICUs) of our setting for March-October 2002 and March-October 2003 periods. Overall daily defined dose/1000 patients/day of restricted drugs decreased, whereas unrestricted drugs increased significantly after the instruction. The cost of all analysed drugs in 2003 period was 540,303USD (-19.6%) less than 2002 period. Nosocomial infection rates in ICUs decreased significantly (p<0.05). When all microbiologically confirmed nosocomial bacteremia cases during the study period were analysed, amoxycilline/clavulanate, ciprofloxacin, cefuroxime, cefotaxime, piperacilline/tazobactam resistance and ESBL rate in Klebsiella pneumoniae decreased significantly (p<0.05). Amikacin resistance in Escherichia coli and Acinetobacter baumannii increased significantly (p<0.05). Antibiotic control is one of the most important and significant ways to save money, and to prevent antibacterial resistance.

External Guide Sequences Targeting the aac(6′)-Ib mRNA Induce Inhibition of Amikacin Resistance

The dissemination of AAC(6')-I-type acetyltransferases have rendered amikacin and other aminoglycosides all but useless in some parts of the world. Antisense technologies could be an alternative to extend the life of these antibiotics. External guide sequences are short antisense oligoribonucleotides that induce RNase P-mediated cleavage of a target RNA by forming a precursor tRNA-like complex. Thirteen-nucleotide external guide sequences complementary to locations within five regions accessible for interaction with antisense oligonucleotides in the mRNA that encodes AAC(6')-Ib were analyzed. While small variations in the location targeted by different external guide sequences resulted in big changes in efficiency of binding to native aac(6')-Ib mRNA, most of them induced high levels of RNase P-mediated cleavage in vitro. Recombinant plasmids coding for selected external guide sequences were introduced into Escherichia coli harboring aac(6')-Ib, and the transformant strains were tested to determine their resistance to amikacin. The two external guide sequences that showed the strongest binding efficiency to the mRNA in vitro, EGSC3 and EGSA2, interfered with expression of the resistance phenotype at different degrees. Growth curve experiments showed that E. coli cells harboring a plasmid coding for EGSC3, the external guide sequence with the highest mRNA binding affinity in vitro, did not grow for at least 300 min in the presence of 15 mug of amikacin/ml. EGSA2, which had a lower mRNA-binding affinity in vitro than EGSC3, inhibited the expression of amikacin resistance at a lesser level; growth of E. coli harboring a plasmid coding for EGSA2, in the presence of 15 mug of amikacin/ml was undetectable for 200 min but reached an optical density at 600 nm of 0.5 after 5 h of incubation. Our results indicate that the use of external guide sequences could be a viable strategy to preserve the efficacy of amikacin.

Emergence of ArmA and RmtB aminoglycoside resistance 16S rRNA methylases in Belgium

16S rRNA methylase-mediated high-level resistance to aminoglycosides has been reported recently in clinical isolates of Gram-negative bacilli only from a limited number of countries. This study was conducted to investigate the occurrence of this type of resistance in clinical isolates of Enterobacteriaceae from two Belgian hospitals and the characteristics of the strains. We screened for high-level gentamicin, tobramycin and amikacin resistance in clinical isolates of Enterobacteriaceae consecutively collected between 2000 and 2005 at two laboratories by PCR for the armA, rmtA and rmtB 16S rRNA methylase genes. The beta-lactamase presence in the strains was also determined by phenotypic and genotypic methods. Overall armA genes were detected in 18 Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae and Citrobacter amalonaticus whereas rmtB was detected in a single E. coli isolate. The rmtA gene was not found. All 16S rRNA methylase-bearing strains produced extended-spectrum beta-lactamases (ESBLs), predominantly type CTX-M-3, as well as various types of beta-lactamases. In the majority of the strains, the armA gene was carried by conjugative plasmids of the IncL/M incompatibility group whereas rmtB was borne by an IncFI plasmid. This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Belgium. The rapid spread of multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases raises clinical concern and may become a major therapeutic threat in the future.

Molecular epidemiology of clinical and carrier strains of methicillin resistant Staphylococcus aureus (MRSA) in the hospital settings of north India.

BackgroundThe study was conducted between 2000 and 2003 on 750 human subjects, yielding 850 strains of staphylococci from clinical specimens (575), nasal cultures of hospitalized patients (100) and eye & nasal sources of hospital workers (50 & 125 respectively) in order to determine their epidemiology, acquisition and dissemination of resistance genes.MethodsOrganisms from clinical samples were isolated, cultured and identified as per the standard routine procedures. Susceptibility was measured by the agar diffusion method, as recommended by the Nat ional Committee for Clinical Laboratory Standards (NCCLS). The modified method of Birnboin and Takahashi was used for isolation of plasmids from staphylococci. Pulsed-field gel electrophoresis (PFGE) typing of clinical and carrier Methicillin resistant Staphylococcus aureus (MRSA) strains isolated during our study was performed as described previously.ResultsIt was shown that 35.1% of Staphylococcus aureus and 22.5% of coagulase-negative staphylococcal isolates were resistant to methicillin. Highest percentage of MRSA (35.5%) was found in pus specimens (n = 151). The multiple drug resistance of all MRSA (n = 180) and Methicillin resistant Coagulase-negative Staphylococcus aureus (MRCNS) (n = 76) isolates was detected. In case of both methicillin-resistant as well as methicillin-sensitive Saphylococcal isolates zero resistance was found to vancomycin where as highest resistance was found to penicillin G followed by ampicillin. It was shown that the major reservoir of methicillin resistant staphylococci in hospitals are colonized/infected inpatients and colonized hospital workers, with carriers at risk for developing endogenous infection or transmitting infection to health care workers and patients. The results were confirmed by molecular typing using PFGE by SmaI-digestion.It was shown that the resistant markers G and T got transferred from clinical S. aureus (JS-105) to carrier S. aureus (JN-49) and the ciprofloxacin (Cf) and erythromycin (E) resistance seemed to be chromosomal mediated. In one of the experiments, plasmid pJMR1O from Staphylococcus aureus coding for ampicillin (A), gentamicin (G) and amikacin (Ak) resistance was transformed into Escherichia coli. The minimal inhibitory concentrations (MICs) for A and G were lower in E. coli than in S. aureus. However, the MIC for Ak was higher in E. coli transformants than in S. aureus.ConclusionThere is a progressive increase in MRSA prevalence and multi-drug resistance in staphylococci. Vancomycin is still the drug of choice for MRSA infections. The major reservoir of methicillin resistant staphylococci in hospitals is colonized/infected inpatients and colonized hospital workers. Resistance transfer from staphylococci to E. coli as well as from clinical to carrier staphylococci due to antibiotic stress seemed to be an alarming threat to antimicrobial chemotherapy.

Detection and Typing of Integrons in Epidemic Strains of Acinetobacter baumannii Found in the United Kingdom

Integrons were sought in Acinetobacter isolates from hospitals in the United Kingdom by integrase gene PCR. Isolates were compared by pulsed-field gel electrophoresis, and most belonged to a small number of outbreak strains or clones of A. baumannii, which are highly successful in the United Kingdom. Class 1 integrons were found in all of the outbreak isolates but in none of the sporadic isolates. No class 2 integrons were found. Three integrons were identified among the main outbreak strains and clones. While a particular integron was usually associated with a strain or clone, some members carried a different integron. Some integrons were associated with more than one strain. The cassette arrays of two of the integrons were very similar, both containing gene aacC1, which confers resistance to gentamicin, two open reading frames coding for unknown products (orfX, orfX'), and gene aadA1a, which confers resistance to spectinomycin and streptomycin. The larger of these integrons had two copies of the first (orfX) of the gene cassettes coding for unknown products. The third integron, with a cassette array containing gene aacA4, which codes for amikacin, netilmicin, and tobramycin resistance; a chloramphenicol acetyltransferase, catB8; and gene aadA1, conferring resistance to spectinomycin and streptomycin, was associated with an OXA-23 carbapenemase-producing clone, which has spread rapidly in hospitals in the United Kingdom during 2003 and 2004. These integron cassette arrays have been found in other outbreak strains of A. baumannii from other countries. We conclude that integrons are useful markers for epidemic strains of A. baumannii and that integron typing provides valuable information for epidemiological studies.

Intrathecal colistin for treatment of highly resistant Pseudomonas ventriculitis

Nosocomial infections with organisms resistant to multiple antibiotic agents represent an evolving challenge in the intensive care setting, particularly in patients requiring surgical diversion of cerebrospinal fluid. The authors present the case of a 51-year-old woman who endured protracted hospitalization and required multiple surgeries including placement of a ventriculoperitoneal shunt. The shunt subsequently became colonized with Pseudomonas aeruginosa, which demonstrated intermediate sensitivity to amikacin and full resistance to all other antibiotics tested 'After failing to respond to intravenous imipenem as well as intravenous and intrathecal amikacin, the patient was successfully treated with intravenous and intrathecal colistin. Colistin is a polymyxin-type antibiotic, rarely used outside of topical application because of reported nephrotoxicity associated with parenteral administration. With activity limited to Gram-negative organisms, colistin is bactericidal by directly disrupting the structure of cell membranes. Authors of a few case reports in the literature have described successful treatment of various ventriculitis with the intrathecal administration of colistin. With bacterial resistances outpacing the pharmaceutical industry's ability to develop novel antibiotics, colistin represents an important alternative in situations involving multidrug-resistant organisms.

Colonización fecal por cepas de Klebsiella pneumoniae productoras de betalactamasas de espectro extendido en una Unidad Neonatal de Cuidados Intensivos

Fecal colonization by multiresistant bacteria can be a source of nosocomial infections. The aim of this work was to study fecal colonization by Klebsiella pneumoniae in neonatal intensive care unit (NICU) patients and investigate the resistance profiles of the strains. From May to October 2001, 11 stool specimens were collected from each patient hospitalized in the NICU during this period (425 specimens). Antimicrobial susceptibility was determined in K. pneumoniae isolates, and 30 strains resistant to third-generation cephalosporins were tested by polymerase chain reaction (PCR) to detect the blaCTX-M-2 gene. K. pneumoniae grew in the 66% of the samples. Extended-spectrum b-lactamases (ESBL) were detected in 82.5% of these strains (ESBL-K. pneumoniae), 54.3% of all the strains studied. Among the neonates colonized by ESBL-K. pneumoniae (56% of patients), significant differences in colonization rates were observed according to gestational age, but not according to the mode of delivery or sex. ESBL-K. pneumoniae strains showed a high frequency of gentamicin resistance (97.3%) and amikacin resistance (71.4%). Nevertheless, they were all susceptible to cefoxitin and imipenem, and more than 90% were also susceptible to ciprofloxacin and piperacillin-tazobactam. In all the cefotaxime-resistant strains, an amplicon consistent with a CTX-M-type beta -lactamase was found by PCR. A high percentage of NICU patients were colonized with ESBL-K. pneumoniae strains belonging to the CTX-M family, with elevated rates of aminoglycoside resistance. Gestational age was the only variable associated with significant differences in colonization rates.

Spread of novel aminoglycoside resistance gene aac(6')-Iad among Acinetobacter clinical isolates in Japan.

A novel aminoglycoside resistance gene, aac(6')-Iad, encoding aminoglycoside 6'-N-acetyltransferase, was identified in Acinetobacter genospecies 3 strain A-51. The gene encoded a 144-amino-acid protein, which shared modest identity (up to 36.7%) with some of the aminoglycoside 6'-N-acetyltransferases. The results of high-pressure liquid chromatography assays confirmed that the protein is a functional aminoglycoside 6'-N-acetyltransferase. The enzyme conferred resistance to amikacin, tobramycin, sisomicin, and isepamicin but not to gentamicin. The prevalence of this gene among Acinetobacter clinical isolates in Japan was then investigated. Of 264 Acinetobacter sp. strains isolated from geographically diverse areas in Japan in 2002, 16 were not susceptible to amikacin, and aac(6')-Iad was detected in 7. Five of the producers of aminoglycoside 6'-N-acetyltransferase type Iad were identified as Acinetobacter baumannii, and two were identified as Acinetobacter genospecies 3. These results suggest that aac(6')-Iad plays a substantial role in amikacin resistance among Acinetobacter spp. in Japan.

Multidrug-resistant Pseudomonas aeruginosa strains harbouring R-plasmids and AmpC β-lactamases isolated from hospitalised burn patients in a tertiary care hospital of North India

The present study was designed to determine resistance rates and patterns in Pseudomonas aeruginosa isolates obtained from hospitalised burn patients in an Indian tertiary care hospital. To that end, we isolated plasmid(s) from the multidrug-resistant isolates, demonstrated the plasmid-mediated resistance by curing and transformation experiments, and screened all the isolates for the occurrence of AmpC β-lactamases. Thirty isolates of P. aeruginosa were analysed for the presence of antibiotic resistance. Plasmid-curing experiments and AmpC β-lactamase detection were performed on all the isolates and seven isolates showing the most common antibiotic resistance pattern were selected for plasmid isolation and transformation experiments. All 30 isolates were multidrug-resistant and the majority (83.3%) of isolates were resistant to seven or more antibiotics, out of 11 antibiotics tested including anti-pseudomonal and non-anti-pseudomonal antimicrobial drugs. The most striking feature was the presence of resistance to amikacin. A 48.5-kb plasmid was isolated from the isolates. Curing and transformation experiments showed that resistance to amikacin was plasmid-mediated. Phenotypic screening for the occurrence of AmpC β-lactamases showed that 20% of isolates were AmpC producers whereas 10% of isolates were characterised as ‘indeterminate’ for AmpC enzyme. In conclusion, a markedly high (56.7%) resistance to amikacin was noted in the present study. Amikacin resistance was determined to be plasmid-encoded and the presence of an AmpC β-lactamase was inferred in 20% of isolates. This is among the first reports regarding the emergence of plasmid-mediated resistance to amikacin and the occurrence of AmpC β-lactamases in P. aeruginosa strains from India.

Inhibition of aminoglycoside 6'-N-acetyltransferase type Ib-mediated amikacin resistance by antisense oligodeoxynucleotides.

Amikacin has been very useful in the treatment of infections caused by multiresistant bacteria because it is refractory to the actions of most modifying enzymes. However, the spread of AAC(6')-I-type acetyltransferases, enzymes capable of catalyzing inactivation of amikacin, has rendered this antibiotic all but useless in some parts of the world. The aminoglycoside 6'-N-acetyltransferase type Ib, which is coded for by the aac(6')-Ib gene, mediates resistance to amikacin and other aminoglycosides. RNase H mapping and computer prediction of the secondary structure led to the identification of five regions accessible for interaction with antisense oligodeoxynucleotides in the aac(6')-Ib mRNA. Oligodeoxynucleotides targeting these regions could bind to native mRNA with different efficiencies and mediated RNase H digestion. Selected oligodeoxynucleotides inhibited AAC(6')-Ib synthesis in cell-free coupled transcription-translation assays. After their introduction into an Escherichia coli strain harboring aac(6')-Ib by electroporation, some of these oligodeoxynucleotides decreased the level of resistance to amikacin. Our results indicate that use of antisense compounds could be a viable strategy to preserve the efficacies of existing antibiotics to which bacteria are becoming increasingly resistant.

Outbreak of infection with high-level gentamicin-resistant Enterococcus faecalis (HLGRE) in a Norwegian hospital

To examine and characterize a suspected outbreak of high-level gentamicin-resistant Enterococcus (HLGRE) infection. Eighty-nine patients with clinical infection diagnosed during hospital stay or within 30 days after discharge in the period from June 1995 to 31 December 1999 were included in the study. One control patient was assigned for each HLGRE patient according to localization in the hospital (same ward), time of admission (+/-3 months), and age (+/-10 years). Unadjusted risk analysis and multivariate logistic regression analysis were performed. Sixty-nine HLGRE strains were subjected to PCR amplification of the genes coding for aminoglycoside-3'-O-phosphoryltransferase-III (APH(3')-III) and aminoglycoside-6'-N-acetyltransferase/2"-O-phosphoryltransferase-III (AAC(6')/APH(2")). The gene aacA/aphD, associated with HLGRE, was detected by PCR in all isolates, and the gene aphA3, associated with high-level streptomycin, kanamycin and amikacin resistance, was detected in 56 of the 69 isolates. None of the 69 isolates was resistant to glycopeptides or ampicillin. Resistance to ciprofloxacin was found in 57 (82.6%). Pulsed-field gel electrophoresis analysis revealed 12 different genotypes, among which two major clusters dominated. Both clonal expansion and the emergence of unique strains contributed to the increased number of infections caused by HLGRE. Urinary catheterization, duration of hospital stay and antibiotic therapy were significant risk factors for HLGRE infection.

Retrospective analysis of antibiotic susceptibility patterns of respiratory isolates of Pseudomonas aeruginosa in a Turkish University Hospital

BackgroundLower respiratory tract infections due to Pseudomonas aeruginosa have a high mortality rate. Antibacterial activity of various antibiotics against P. aeruginosa isolated from each hospital depends on the variety or amount of antibiotics used in each hospital.MethodA total of 249 respiratory isolates of Pseudomonas aeruginosa in Sivas (Turkey) were included between January-1999 and January-2002. Isolates were tested against 14 different antibiotics by a disc diffusion method or standardized microdilution technique.ResultsOrganisms were cultured from the following specimens: sputum (31.3%), transtracheal/endotracheal aspirates (37.8%), and bronchial lavage (30.9%). Isolates in bronchial lavage were highly susceptible to cefoperazone and aminoglycosides. Resistance to ampicillin/sulbactam was 98.8%, ticarcillin 40.1%, ticarcillin/clavulanic acid 11.2%, piperacillin 21.8%, aztreonam 66.6%, cefotaxim 75.4%, ceftriaxone 84.2%, cefoperazone 39.0%, ceftazidime 50.8%, gentamicin 57.5%, tobramycin 58.4%, amikacin 25.4%, ciprofloxacin 16.1%, and imipenem/cilastatin 21.6%. The term multidrug-resistant P. aeruginosa covered resistance to imipenem, ciprofloxacin, ceftazidime, gentamicin, and piperacillin. 1.2% of isolates were multidrug-resistant.ConclusionsThese findings suggest that amikacin resistance increases progressively in Turkey. Piperacillin and ticarcillin/clavulanate were the most active agents against both imipenem- and ciprofloxacin-resistant isolates in our region.

BACTERIOLOGY OF NEONATAL SEPTICAEMIA IN A TERTIARY CARE HOSPITAL OF NORTHERN INDIA

To study the bacteriology of neonatal septicaemia in a tertiary care hospital of Northern India we prospectively enrolled all the suspected cases of neonatal septicaemia, which were not on antimicrobials. One to two millilitre of blood from these neonates was cultured in brain heart infusion broth. Out of 728 cases, 346 (47.5%) were positive on blood culture. The most frequent offender was Klebsiella spp. (24.5%) followed by Enterobacter spp. (22.8%). There was an overall predominance of gram negative organisms. Coagulase negative staphylococci (CONS) were more frequently isolated (16.5%) than Staphylococcus aureus (14%). More than 89% of the Staphylococci isolated were resistant to penicillin. None were resistant to vancomycin or teicoplanin. More than 95% of enterobacteria were resistant to anti gram negative penicillin group of drugs and more than 40% were resistant to extended spectrum cephalosporins. Ciprofloxacin and amikacin resistance was infrequent. Thus, initial therapy in our hospital may be aimed at Gram negative organisms and amikacin and ciprofloxacin may be used as first line drugs.

Making sense of antimicrobial use and resistance surveillance data: application of ARIMA and transfer function models

Making sense of antimicrobial use and resistance surveillance data: application of ARIMA and transfer function models

High-level amikacin resistance in Pseudomonas aeruginosa associated with a 3′-phosphotransferase with high affinity for amikacin

This work describes the characterization of the phosphotransferase enzymatic activity responsible for amikacin resistance in two clinical Pseudomona aeruginosa strains, isolated from a hospital that used amikacin as first-line aminoglycoside. Amikacin-resistant P. aeruginosa PA40 and PA43 (MIC: 128 mg/l) were shown to have APH activity with a substrate profile similar to that of APH(3′)-VI. The enzyme from P. aeruginosa PA40 was purified to >70% homogeneity. The K m of amikacin for this enzyme was 1.4 μM, the V max/ K m ratio for amikacin was higher than for the other aminoglycosides tested and PCR and DNA sequencing ruled out the presence of aph(3′ )-IIps. Amikacin resistance in this strain was, therefore, associated with APH(3′)-VI and the high affinity of this enzyme for amikacin could explain the high-level resistance that we observed.