Molecular characterisation of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp. isolates at a tertiary-care centre in Lebanon.

The prevalence of bla CTX-M, bla TEM and bla SHV genes among extended-spectrum beta-lactamase (ESBL)-producing clinical isolates of Escherichia coli (n = 50) and Klebsiella spp. (n = 50) from Lebanon was 96%, 57% and 67%, and 40%, 82% and 84%, respectively. Genotyping revealed that the clonal diversity was unrelated to the presence of bla genes. Sequence analysis of 16 selected isolates identified the bla CTX-M-15, bla TEM-1, bla OXA-1 and six bla SHV genes, as well as the gene encoding the quinolone-modifying enzyme AAC(6')-Ib-cr. The genes encoding CTX-M-15 and AAC(6')-Ib-cr were carried on a 90-kb plasmid of the pC15-1a or pCTX-15 type, which transferred both ESBL production and quinolone resistance from donors to transconjugants.     

Prevalence and diversity of extended-spectrum β-lactamases in faecal Escherichia coli isolates from healthy humans in Spain

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates were detected in seven of 105 faecal samples from healthy humans, from two Spanish cities, during 2007. In these isolates, five ESBLs were detected, CTX-M-14 ( n  = 2), CTX-M-1 ( n  = 2), CTX-M-32 ( n  = 1), CTX-M-8 ( n  = 1) and TEM-52 ( n  = 1). Both bla _CTX-M-14a (surrounded by IS Ecp1 -IS 903 ) and bla _CTX-M-14b variants (included in an integron structure) were identified in this study. This is the first time that the bla _CTX-M-8 gene and ESBLs of the CTX-M-8 group have been found in Europe and Spain, respectively. Faecal E. coli of healthy humans therefore constitute a reservoir of bla _CTX-M genes with different surrounding genetic elements.     

Occurrence of extended-spectrum β-lactamase-producing Salmonella enterica in northern Spain with evidence of CTX-M-9 clonal spread among animals and humans

Among the 1233 Salmonella enterica isolates obtained in two Spanish hospitals, five isolates (0.4%) (serovars: Virchow, four; Livingstone, one) had the phenotype of an extended-spectrum β-lactamase (ESBL) producer. The genetic characterization of the ESBL of S. enterica Livingstone revealed a bla _SHV-2 gene. The bla _CTX-M-10 gene in a phage-related genetic environment was found in one S. enterica Virchow isolate, and the bla _CTX-M-9 gene within the In60 integron was found in the three remaining Virchow isolates. These three isolates presented indistinguishable or closely related pulsed-field gel electrophoresis patterns among themselves and also as compared with the two other bla _CTX-M-9-containing isolates previously obtained from animals. ESBL production is an emerging mechanism of resistance in S. enterica in the two studied hospitals.     

Prevalence and characterization of plasmid-mediated quinolone resistance genes in extended-spectrum β-lactamase-producing Enterobacteriaceae isolates in Mexico

The objectives of this study were to investigate the prevalence of plasmid-mediated quinolone resistance genes in a collection of 226 extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolates and characterize the qnr-positive isolates. The rate of qnr-positive isolates was 21.6% (49/226), 49.5% for aac(6')-Ib-cr (112/226), and 1.7% for qepA1 (4/226). Those isolates carried qnr genes corresponding to types qnrB (71.4%), qnrS1 (24.4%), and qnrA1 (18.3%). The distribution among bacterial species was as follows: 55.8% (19/34) to Enterobacter cloacae, 50% (28/56) to Klebsiella pneumoniae, and 1.4% (2/136) to Escherichia coli. The characterization of qnr-positive isolates indicated the ESBL SHV-types as the most prevalent (81.6%), including the ESBLs SHV-12, SHV-5, and SHV-2a, followed by CTX-M-15 (44.9%) and TLA-1 (8.1%). In addition, for qnr-positive isolates, the prevalence of aac(6')-Ib-cr was 55.1%, but qepA was not identified. Alterations at codons Ser-83 and Asp-87 in GyrA and at codons Ser-80 in ParC were observed in 69% and 80% of the qnr-positive isolates, respectively. The analysis of the transconjugants revealed a cotransmission of bla(CTX-M-15) with qepA1 or aac(6')-Ib-cr and/or qnrA1 and bla(SHV-type) with qnrB5 and qnrB6 genes. To conclude, these findings indicate a high prevalence of qnr and aac(6')-Ib-cr among ESBL-producing isolates from Mexican hospitals and point to the wide spread of qnr-like determinants associated to ESBLs SHV- and CTX-M-type in Mexican clinical isolates.     

Prevalence of the plasmid-mediated quinolone resistance genes, aac(6')-Ib-cr, qepA, and oqxAB in clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in Korea

In this study, we sought to determine the prevalence of the plasmid-mediated quinolone resistance (PMQR) genes aac(6')-Ib-cr, qepA, and oqxAB in extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates in South Korea. In total, 104 isolates (63 E. coli and 41 K. pneumoniae) were collected. We found that 23 of the 63 (36.5%) E. coli and nine of the 41 (22.0%) K. pneumoniae isolates were positive for aac(6')-Ib-cr. No isolate was positive for qepA, while transferable oqxAB was detected only in 10 (24.4%) K. pneumoniae isolates. Among the 32 aac(6')-Ib-cr-positive isolates, 30 (93.8%) were positive for both aac(6')-Ib-cr and bla(CTX-M) (CTX-M-15, -14, and -57). Our results suggest that PMQR determinants are highly prevalent in ESBL-producing E. coli and K. pneumoniae isolates in Korea.     

Characterization of Acinetobacter baumannii carrying blaOXA-23, blaPER-1 and armA in a Korean hospital

Forty-two multidrug-resistant (MDR) Acinetobacter baumannii isolates were obtained during outbreaks in a Korean hospital. The co-carriage of bla _OXA-23, bla _OXA-51, bla _PER-1 and armA was observed in 23 isolates, and they were susceptible only to colistin and minocycline. The MDR A. baumannii isolates were found to belong to sequence group 1 using sequence-based typing.     

Prevalence of plasmid-mediated quinolone resistance genes in uropathogenic Escherichia coli isolated in a teaching hospital of northern Italy

A retrospective study was conducted to determine the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in uropathogenic Escherichia coli isolated from inpatients and outpatients in a teaching hospital of northern Italy. The presence of qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA was evaluated in 76 and 72 nalidixic acid-resistant E. coli, isolated in 2004 and 2006, respectively. Positivity for the aac(6')-Ib-cr gene was demonstrated in 3 of 76 (3.9%) and 8 of 72 (11%) isolates, respectively; no other PMQR determinant was found. All aac(6')-Ib-cr-positive strains also showed two point mutations in the gyrA and parC genes. Most aac(6')-Ib-cr-positive isolates demonstrated the contemporary presence of bla(CTX-M-15), bla(OXA-1/30), and bla(TEM-1) genes and 4/11 harbored a class 1 integron with a dfrA17-aadA5 gene cassette arrangement. Interestingly, all aac(6')-Ib-cr-positive isolates belonged to B2 phylogenetic group, O25b antigen type, multi locus sequence type 131, and to a cluster of approximately 70% similarity level by pulsed-field gel electrophoresis (PFGE). These findings suggest the circulation of the previously described intercontinentally spreading E. coli O25:H4-ST131 clone in our geographical area since 2004. Hybridization studies of the PFGE profiles showed the aac(6')-Ib-cr gene to be associated with different molecular weight bands (40-350 kb) and interestingly aac(6')-Ib-cr chromosomal integration was demonstrated in one strain by I-Ceu I method. This represents the first report to investigate the presence and diffusion of PMQR determinants in northern Italy and to describe aac(6')-Ib-cr chromosomal integration in E. coli.     

Susceptibility of strains of Streptococcus agalactiae to macrolides and lincosamides, phenotype patterns and resistance genes

The Group B streptococcus ( Streptococcus agalactiae ) is a pathogen of increasing importance in human disease. We therefore studied the susceptibility of clinical isolates of S. agalactiae to penicillin G, erythromycin, azithromycin and clindamycin using National Committee for Clinical Laboratory Standards methodology, and we also determined the phenotypes of macrolide-lincosamide susceptibility and the resistance genes implicated in a group of selected isolates of the different phenotypes. We used 221 isolates collected between 1997 and 1999 in two Health Authority Areas in Móstoles and Granada, Spain. The minimal concentration for 90% inhibition (MIC₉₀) for penicillin G was 0.12 mg/L and all the isolates tested were susceptible. One hundred and eighty-five (83.7%) were susceptible to erythromycin and azithromycin and 191 (86.4%) were susceptible to miocamycin and clindamycin. Twenty-three isolates (10.4%) had a constitutive MLS_B phenotype, seven (3.2%) an inducible phenotype, and six (2.7%) an M phenotype. All except one of the MLS_B phenotype isolates tested ( n  = 23) carried erm genes; in two strains with the mef (A) gene, all the M phenotype ( n  = 6) isolates tested carried mef genes, while erm and mef (A) genes were absent in all the macrolide-lincosamide-susceptible ( n  = 12) isolates tested. In our environment, resistance to macrolide and lincosamide in S. agalactiae was present in 10–16% of the isolates. The majority of resistant strains had the MLS_B phenotype.     

Using nucleic acid microarrays to perform molecular epidemiology and detect novel β-lactamases: a snapshot of extended-spectrum β-lactamases throughout the world

The worldwide dissemination of extended-spectrum-β-lactamase (ESBL)- and carbapenemase-producing Enterobacteriaceae is a major concern in both hospital and community settings. Rapid identification of these resistant pathogens and the genetic determinants they possess is needed to assist in clinical practice and epidemiological studies. A collection of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis isolates, including phenotypically ESBL-positive (n = 1,093) and ESBL-negative isolates (n = 59), obtained in 2008-2009 from a longitudinal surveillance study (SMART) was examined using an in vitro nucleic acid-based microarray. This approach was used to detect and identify bla(ESBL) (bla(SHV), bla(TEM), and bla(CTX-M) genes of groups 1, 2, 9, and 8/25) and bla(KPC) genes and was combined with selective PCR amplification and DNA sequencing for complete characterization of the bla(ESBL) and bla(KPC) genes. Of the 1,093 phenotypically ESBL-positive isolates, 1,041 were identified as possessing at least one bla(ESBL) gene (95.2% concordance), and 59 phenotypically ESBL-negative isolates, used as negative controls, were negative. Several ESBL variants of bla(TEM) (n = 5), bla(SHV) (n = 11), bla(CTX-M) (n = 19), and bla(KPC) (n = 3) were detected. A new bla(SHV) variant, bla(SHV-129), and a new bla(KPC) variant, bla(KPC-11), were also identified. The most common bla genes found in this study were bla(CTX-M-15), bla(CTX-M-14), and bla(SHV-12). Using nucleic acid microarrays, we obtained a "molecular snapshot" of bla(ESBL) genes in a current global population; we report that CTX-M-15 is still the dominant ESBL and provide the first report of the new β-lactamase variants bla(SHV-129) and bla(KPC-11).     

Molecular characterization and antimicrobial susceptibility testing of Escherichia coli isolates from patients with urinary tract infections in 20 Chinese hospitals

A total of 222 urinary Escherichia coli isolates from 20 tertiary hospitals in 15 different provinces and 4 municipalities in mainland China were characterized by antimicrobial susceptibility, phylogrouping, and the presence of plasmid-mediated quinolone resistance genes. A subset of 138 suspected extended-spectrum cephalosporinase (ESC) producers were examined for genes encoding cephalosporin resistance. Forty-three isolates harboring bla(CTX-M-14) or bla(CTX-M-15) were analyzed by pulsed-field gel electrophoresis (PFGE), and plasmids containing these genes were typed using PCR-based replicon typing (PBRT). Thirteen phylogroup B2 bla(CTX-M-14)- and bla(CTX-M-15)-positive isolates were analyzed by multilocus sequence typing (MLST). A frequent occurrence of resistance (>46%) was observed toward cephalosporins, gentamicin, and fluoroquinolones. Among the 222 isolates, 4 qnrS1, 4 qepA, and 16 aac(6')-Ib-cr genes were confirmed. Four major phylogroups (A, B1, B2, and D) and nontypeable isolates (NTs) were found among the isolates, with phylogroup D (54%) being the most common phylogroup. A total of 110 (80%) of the 138 screened isolates harbored bla(CTX-M) genes, with bla(CTX-M-14) (71%) and bla(CTX-M-15) (24%) being the most prevalent of these genes. Nine of the 13 CTX-M-15- or CTX-M-14-containing B2 isolates belonged to ST131. PFGE typing showed a high level of diversity, and plasmid analysis indicated a very large pool of different resistance plasmids mediating the spread of bla(CTX-M) genes in mainland China. An equally very high frequency of resistance and equally high levels of diversity in phylogroups, PFGE types, and plasmids were observed among community- and hospital-acquired E. coli isolates, indicating the presence of a large reservoir in the community and a long-term spread of cephalosporin resistance in China.     

Carbapenem-resistant and OXA-23-producing Acinetobacter baumannii isolates in the United Arab Emirates

Five carbapenem-resistant Acinetobacter baumannii isolates, collected from the United Arab Emirates in 2006, were investigated to identify the mechanism(s) responsible for carbapenem resistance. Genotyping was performed by pulsed-field gel electrophoresis, and the location of the bla _OXA-23 gene was determined by using the endonuclease I Ceu I technique and mating-out assays. The four isolates in which the bla _OXA-23 gene was located on the chromosome within a Tn 2006 composite transposon were clonally related. The single non-clonally related isolate harboured the bla _OXA-23 gene on a 70-kb transferable plasmid. This study reports on the dissemination of OXA-23-producing A. baumannii isolates in the Middle East.     

Interferon gamma receptor 1 gene polymorphism in patients with tuberculosis in China

The aim of the study was to examine the influence of the CA microsatellite polymorphisms of interferon gamma receptor 1 on patients with tuberculosis (TB) in the south-eastern Chinese population. Genomic DNA from patients with TB ( n  = 155) and ethnically matched controls ( n  = 89) were genotyped by short tandem repeat-PCR method. The allele frequency of (CA)₂₅ was 1.70-fold higher among patients than that among controls (95% CI 1.07–2.70) ( P  = 0.025). Compared with the non-(CA)₂₅/non-(CA)₂₅ reference group, the risk to TB of the carriers of (CA)₂₅/(CA)₂₅ genotypes were 6.46-fold (95% CI 1.40–29.74) ( P  = 0.0017) higher. On the contrary, the allele frequency of (CA)₂₆ was 0.29-fold lower in patients than that in controls (95% CI 0.11–0.76) ( P  = 0.012). Genotypes with (CA)₂₆ allele were at 0.35-fold (95% CI 0.13–0.98) ( P  = 0.045) lower to the risk of TB, compared with that of the non-(CA)₂₆/non-(CA)₂₆ in the reference group. The above results indicated that the allele (CA)₂₅ appeared to be susceptible to TB, while the allele (CA)₂₆ to be protective towards TB. Our data also suggest that the CA repeat was a highly polymorphic marker and could be used for linkage and association analysis.     

Molecular epidemiology of ciprofloxacin-resistant extended-spectrum β-lactamase-producing Klebsiella pneumoniae in Taiwan

Fluoroquinolone resistance in extended-spectrum β-lactamases (ESBL)-producing isolates results in very few antimicrobial treatment options. In Taiwan's Surveillance of Antimicrobial Resistance (TSAR) III program, 124 (52.8%) cases of ESBL-producing Klebsiella pneumoniae (ESBL-KP) were resistant to ciprofloxacin. The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and chromosomal quinolone resistance-determining regions (QRDR) of gyrA and parC genes among ESBL-KP isolates was assessed via PCR sequencing. Chromosomal QRDR mutations were present in most of the 123 (96.8%) cases of ciprofloxacin-resistant ESBL-KP isolates. Sixty-six (53.2%) isolates had at least one PMQR gene. qnrB2, qnrB4, and qnrS1 were detected in 26, 19, and 13 isolates, respectively, whereas qnrA, qnrC, and qnrD were not detected. ESBL genes were transferable via conjugation with either aac(6')Ib-cr or qnrB in 63.6% of the isolates carrying PMQR genes. QnrB was associated with either CTX-M-15 or SHV-12, and aac(6')Ib-cr was linked to CTX-M-3 or CTX-M-14 in plasmids. qnrS did not co-transfer with ESBL genes. Clonal spread of PMQR genes harboring ESBL-KP isolates was observed in three hospitals. QnrA, which is common in Asia, was unexpectedly absent in ESBL-KP in Taiwan. Aside from transmission via clonal spread for ciprofloxacin-resistant ESBL-KP, concomitant transference of PMQR genes with either bla(CTX-M) or bla(SHV) via plasmid was common.     

Identification of SHV-type extended spectrum beta-lactamase genes in Pseudomonas aeruginosa by PCR-restriction fragment length polymorphism and insertion site restriction-PCR

We propose a simple and rapid method to discriminate SHV-type extended spectrum beta-lactamase (ESBL) genes in P. aeruginosa based on PCR techniques (PCR-RFLP and RSI-PCR). We studied 22 producing ESBL P. aeruginosa strains isolated from seven immunocompromised patients (19 isolates) and from environmental swabs (three isolates) at the Bone Marrow Transplantation Center of Tunis. Screening PCR with primer pairs designed to detect gene encoding TEM, SHV, OXA group I, OXA group II, OXA-18 and PER-1 ESBL was positive for bla(OXA18) and bla(SHV) genes in all isolates. Pulsed field gel electrophoresis using SpeI endonuclease defined five genotypic groups. For at least one isolate corresponding to each genotype observed, restriction of PCR products by DdeI and BsrI revealed the same restriction pattern that the bla(SHV-1) negative control; in the same way, RSI-PCR products digestion by NruI, thus excluding 35, 238 and 240 mutations characterizing reported ESBL in P. aeruginosa (SHV-2a, SHV5 et SHV12), and suggesting that studied bla(SHV) genes were not ESBL ones. Genomic DNA hybridization by southern blot with probe consisting in bla(SHV-1) gene was positive in these isolates. Sequencing the full-length open reading frame revealed nucleotide sequence of the bla(SHV-1). PCR-RFLP and RSI-PCR results were then confirmed. This approach is effective for screening P. aeruginosa for ESBL genes carriage in epidemiological studies and for detecting new variants.     

Effects of phenotype and genotype on methods for detection of extended-spectrum-beta-lactamase-producing clinical isolates of Escherichia coli and Klebsiella pneumoniae in Norway

Consecutive clinical isolates of Escherichia coli (n = 87) and Klebsiella pneumoniae (n = 25) with reduced susceptibilities to oxyimino-cephalosporins (MICs > 1 mg/liter) from 18 Norwegian laboratories during March through October 2003 were examined for bla(TEM/SHV/CTX-M) extended-spectrum-beta-lactamase (ESBL) genes, oxyimino-cephalosporin MIC profiles, ESBL phenotypes (determined by the ESBL Etest and the combined disk and double-disk synergy [DDS] methods), and susceptibility to non-beta-lactam antibiotics. Multidrug-resistant CTX-M-15-like (n = 23) and CTX-M-9-like (n = 15) ESBLs dominated among the 50 ESBL-positive E. coli isolates. SHV-5-like (n = 9) and SHV-2-like (n = 4) ESBLs were the most prevalent in 19 ESBL-positive K. pneumoniae isolates. Discrepant ESBL phenotype test results were observed for one major (CTX-M-9) and several minor (TEM-128 and SHV-2/-28) ESBL groups and in SHV-1/-11-hyperproducing isolates. Negative or borderline ESBL results were observed when low-MIC oxyimino-cephalosporin substrates were used to detect clavulanic acid (CLA) synergy. CLA synergy was detected by the ESBL Etest and the DDS method but not by the combined disk method in SHV-1/-11-hyperproducing strains. The DDS method revealed unexplained CLA synergy in combination with aztreonam and cefpirome in three E. coli strains. The relatively high proportion of ESBL-producing E. coli organisms with a low ceftazidime MIC in Norway emphasizes that cefpodoxime alone or both cefotaxime and ceftazidime should be used as substrates for ESBL detection.     

Transferable plasmid mediating resistance to multiple antimicrobial agents in Klebsiella pneumoniae isolates in Greece

Objective   To investigate the underlying resistance mechanisms in 10 Klebsiella pneumoniae isolates.
Methods   Ten K. pneumoniae strains according to distinct bacteriocin typing and REP-PCR, were examined for their plasmid content, their ability to transfer their resistance to aminoglycosides and third-generation cephalosporins, and their production of aminoglycoside-modifying enzymes and β -lactamases.
Results   Transfer of resistance to the above-mentioned antibiotics as well as to co-trimoxazole and tetracycline in Escherichia coli strain RC 85 at a frequency of 5–10⁶ was achieved for all strains by conjugation. Similar strains harbor a self-transferable multiresistant plasmid (80 kb) with similar Eco RI and Hind III restriction patterns. This plasmid encodes an extended-spectrum β -lactamase which confers high-level resistance to third-generation cephalosporins and aztreonam. It produces SHV-5 β -lactamase, as demonstrated by isoelectric focusing and DNA sequencing. Aminoglycoside resistance was co-transferred, and AAC(6')-I, mediating resistance to gentamicin, tobramycin, netilmicin and amikacin, and AAC(3)-I, mediating resistance to gentamicin and sisomycin, were encoded in all isolates and their transconjugants, while APH(3')-I, mediating resistance to kanamycin and neomycin, was encoded in seven strains.
Conclusions   It appears that a multiresistant transferable plasmid encoding the SHV-5 β -lactamase, causing unusually high resistance to ceftazidime and aztreonam, and the combination AAC(6')-I + AAC(3)-I of acetylating enzymes causing, also resistance to all clinically available aminoglycosides, is established in K. pneumoniae in Greece.     

Pharyngeal colonization prevalence rates for Streptococcus pyogenes and Streptococcus pneumoniae in a respiratory chemoprophylaxis intervention study using azithromycin

Objectives   A prospective assessment of the pharyngeal colonization prevalence rates for Streptococcus pyogenes and Streptococcus pneumoniae before and after an azithromycin chemoprophylaxis intervention clinical trial in a cohort of US Marine Corps trainees. In addition, the minimum inhibitory concentrations (MICs) for all streptococcal isolates, for azithromycin, penicillin, erythromycin and cefotaxime are reported.
Methods   Between November 1994 and March 1995, 1108 asymptomatic male US Marine Corps trainees, located in Southern California, were randomly assigned to one of three intervention groups: (1) weekly oral azithromycin, 500 mg ( n  = 362); (2) 1.2 MU benzathine penicillin G, intramuscularly once ( n  = 374); or (3) no chemoprophylaxis ( n  = 372). Subjects provided both a pre- and post-training pharyngeal culture and microbial analysis was conducted to determine the colonization status of each study subject.
Results   The pretraining colonization prevalence was 1.2% for S. pneumoniae and 2.4% for S. pyogenes . There was no statistical difference in pretraining prevalence between the three treatment groups for either organism. Post-training pharyngeal cultures revealed an overall prevalence of 1.1% with no difference between treatment arms. However, the overall post-training prevalence of S. pyogenes colonization increased to 4.8%, with the azithromycin group having significant evidence of protection (0.7%) in comparison with the no-treatment group (8.2%). The Etest method demonstrated no significant difference in the MIC₅₀, MIC₉₀, and MIC ranges between pre- and post-training isolates for any of the tested drugs.
Conclusion The use of azithromycin as a chemoprophylactic agent to reduce the colonization and subsequent infection of streptococcal respiratory disease among healthy adult male military recruits may be beneficial.     

Fecal colonization of Enterobacteriaceae carrying plasmid-mediated quinolone resistance determinants in Korea

The aims of the current study were to investigate the prevalence and molecular characteristics of plasmid-mediated quinolone resistance (PMQR) genes from colonizing fecal organisms and to compare the incidence and subtype of these genes according to bacterial species and hospital at five tertiary-care hospitals in Korea. A total of 500 nonduplicated clinical isolates of Enterobacteriaceae were obtained from fecal specimens at five tertiary-care hospitals between March and May 2008. The PMQR genes (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) were amplified by PCR and confirmed by direct sequencing of the PCR products. A total of 83 (16.6%) qnr-positive isolates were detected. The prevalence rates of qnrA, qnrB, and qnrS were 1.4%, 13.6%, and 1.6%, respectively. The species distributions of qnrB-positive isolates were Klebsiella pneumoniae (37/109; 33.9%), Citrobacter freundii (10/34; 29.4%), Citrobacter braakii (8/13; 61.5%), and Escherichia coli (8/275; 2.9%). Sixteen subtypes of qnrB were detected, including seven novel variants. The prevalences of aac(6')-Ib-cr and qepA were 15.6% (n=78) and 0.6% (n=3), respectively. The aac(6')-Ib-cr gene was detected in 39 (47.0%) of 83 qnr-positive isolates and 39 (9.4%) of 417 qnr-negative isolates There was one qepA variant containing a novel mutation (Ala231Val). The prevalence of PMQR genes was high in Enterobacteriaceae from stool specimens in Korea, and there was a close relation between qnr and aac(6')-Ib-cr.     

The effect of low protein diet in pregnancy on the development of brain metabolism in rat offspring

The effect of maternal low protein diet in pregnancy on the function of offspring cerebral cytochrome c oxidase (CcO) was investigated in vitro immediately before and after birth, using fetal and neonatal rat pup forebrain tissue. Pregnant rat dams were fed either a control (C, 18% casein n = 22) or low protein (LP, 9% casein n = 14) diet. Cerebral tissues were harvested from pups the day before (E21) and after (P1) birth. A Clarke electrode chamber was used to determine O₂ consumption in brain tissue homogenate, under baseline conditions with and without the mitochondrial electron transport chain inhibitor myxothiazol and in the presence of incremental doses of the electron donor N ', N ', N ', N '-tetramethyl- p -phenylenediamide (TMPD) with myxothiazol. Maximal stimulated CcO activity     was less in LP versus C pups at both E21 (P < 0.001) and P1 ( P < 0.05). At E21 only, sensitivity to electron flux (pEC₅₀) was greater ( P < 0.001) in LP compared to C offspring. In addition,     was reduced and pEC₅₀ was greater after birth (i.e. P1 versus E21) in C ( P < 0.001) but not in LP pups. This is the first report of the effects of maternal dietary imbalance in pregnancy on offspring cerebral metabolic function. The effects may form part of a developmental adaptive response to reduce energy consumption and promote perinatal survival, or to confer advantage in a postnatal environment predicted to be nutritionally poor.