Haluk Vahaboglu

Genetic Environment and Expression of the Extended-Spectrum β-Lactamase blaPER-1 Gene in Gram-Negative Bacteria

ABSTRACT The genetic location of the gene coding for the expanded-spectrum β-lactamase PER-1 was analyzed in a series of gram-negative isolates. It was identified as part of a composite transposon bracketed by two novel insertion elements, ISPa12 and ISPa13, belonging to the IS4 family that possess transposases that share 63% amino acid identity and that are chromosomally located in Pseudomonas aeruginosa, Providencia stuartii, and Acinetobacter baumannii. On the contrary, the blaPER-1 gene was identified just downstream of an ISPa12 element but not within a composite transposon when it was located on a plasmid in Salmonella enterica serovar Typhimurium and A. baumannii isolates. In both cases, expression of the blaPER-1 gene was driven by promoter sequences located in ISPa12.

Resistance to extended-spectrum cephalosporins, caused by PER-1 beta-lactamase, in Salmonella typhimurium from Istanbul, Turkey.

Two Salmonella typhimurium isolates were studied, one as a representative from a series of neonatal meningitis cases treated at an Istanbul teaching hospital, the other from a gastro-enteritis case seen at a different Istanbul hospital. Both isolates were resistant to extended-spectrum cephalosporins, as well as penicillins, aminoglycosides and chloramphenicol. Cephalosporin resistance depended on production of PER-1 beta-lactamase, which is an extended-spectrum class A enzyme that is only distantly related to TEM and SHV enzymes, and which was previously known only from Pseudomonas aeruginosa isolates. The PER-1 gene was carried by an 81-MDa plasmid, which also determined resistance to aminoglycosides and chloramphenicol. Although it was not self-transmissible to Escherichia coli, this element did transfer if mobilised with plasmid pUZ8. The two S. typhimurium isolates gave indistinguishable DNA restriction patterns and, in addition to their 81-MDa plasmid, also contained 52- and 2.8-MDa plasmids, the last of these encoded TEM-1 enzyme. The two isolates were identical in serotype, antibiogram and plasmid-profile but nevertheless differed in phage type, and, therefore, represented distinct strains. The emergence of cefotaxime and ceftriaxone resistance in salmonellae is disturbing, since these agents are preferred therapy for neonatal meningitis caused by members of the genus.

Clinical importance of extended-spectrum beta-lactamase (PER-1-type)-producing Acinetobacter spp. and Pseudomonas aeruginosa strains.

Recently, an extended-spectrum beta-lactamase (PER-1) was found to be disseminated among Acinetobacter spp. and Pseudomonasaeruginosa isolates in Turkey. A population-based cohort study was conducted to elucidate predictive mortality factors in patients with nosocomial infections caused by Acinetobacter spp. and P. aeruginosa, with particular reference to PER-1-type extended-spectrum beta-lactamase (ESBL) production. The study group comprised 16 and 21 non-survivors and 82 and 126 survivors in cohorts infected with Acinetobacter and P. aeruginosa, respectively. In the Acinetobacter-infected cohort, nosocomial pneumonia, hypotension and infection with a PER-positive isolate were independent predictors of mortality. In the P. aeruginosa-infected cohort, impaired consciousness, a PER-positive isolate, male sex and (with a negative relative risk) urinary tract infection were independent predictors of death. This study demonstrated the relationship of PER-1-type ESBL-producing Acinetobacter spp. and P. aeruginosa with poor clinical outcome.

Efficacy of oral ribavirin treatment in Crimean-Congo haemorrhagic fever: a quasi-experimental study from Turkey.

OBJECTIVE The aim of this study was to evaluate the efficacy of oral ribavirin treatment in patients with Crimean-Congo haemorrhagic fever (CCHF). METHODS In 2004, all patients diagnosed with CCHF were treated with oral ribavirin, however in 2003 none of the CCHF patients had been given treatment due to lack of confirmatory diagnostic information at that time in Turkey. In this study, patients treated with ribavirin in 2004 (n=126) were compared with ribavirin-untreated CCHF patients (n=92) in 2003. Patients only with a definitive diagnosis of CCHF (clinical symptoms plus the presence of specific IgM antibodies against CCHF virus and presence of viral antigen) were included in this study. RESULTS There was no difference in the case-fatality rate between treated and untreated patients (7.1% vs. 11.9%; P>0.05). A Cox Proportional Hazards regression analysis revealed that altered sensorium and prolonged international normalized ratio were independent predictors of mortality. CONCLUSION Our results showed that oral ribavirin treatment did not improve the survival rate in CCHF patients. Ribavirin and supportive care are the only available choices for treatment of CCHF patients, but to ascertain the efficacy of ribavirin, more laboratory and observational studies are necessary and ultimately, to elucidate these conflicting results and evaluate the efficacy undoubtedly, a multicenter randomised controlled trial will be needed.

Ribavirin for patients with Crimean–Congo haemorrhagic fever: a systematic review and meta-analysis

BACKGROUND Crimean-Congo haemorrhagic fever (CCHF) is a potentially fatal tick-borne infection. The virus is widely distributed around the world and reports of sporadic cases and outbreaks have recently increased significantly. Some authors have proposed that ribavirin improves survival in CCHF and this view appears to be widely accepted. METHODS We evaluated the efficacy of ribavirin in reducing mortality by conducting a systematic review and meta-analysis. We included randomized controlled trials and observational studies that compared the outcomes of CCHF patients who were treated with ribavirin with those of patients that were not treated. The main endpoint we assessed was survival. We also evaluated secondary endpoints, i.e. adverse events, length of stay in the hospital, time taken for laboratory values to return to normal and requirement for blood products. A pooled estimate of the relative risks for survival from each study was obtained by using random effects models. RESULTS One randomized controlled trial and seven observational studies met our inclusion criteria. Most observational studies suffered from different types of bias due to inappropriate selection of controls. Compilation of data from all included studies showed that ribavirin did not improve survival in CCHF (relative risk 1.06, 95% confidence interval 0.97-1.16). Analysis of secondary endpoints did not suggest a clinically significant beneficial effect either. CONCLUSIONS Our systematic review and meta-analysis revealed that the available data in the literature are inadequate to support a claim of efficacy of ribavirin in CCHF. We believe a real uncertainty exists over the benefit of ribavirin in the treatment of CCHF, which necessitates the urgent conduct of a randomized placebo-controlled trial.

Salmonella enterica Serovar Typhimurium blaPER-1-Carrying Plasmid pSTI1 Encodes an Extended-Spectrum Aminoglycoside 6′-N-Acetyltransferase of Type Ib

ABSTRACT We have studied the aminoglycoside resistance gene, which confers high levels of resistance to both amikacin and gentamicin, that is carried by plasmid pSTI1 in the PER-1 β-lactamase-producing strain of Salmonella enterica serovar Typhimurium previously isolated in Turkey. This gene, called aac(6′)-Ib11, was found in a class 1 integron and codes for a protein of 188 amino acids, a fusion product between the N-terminal moiety (8 amino acids) of the signal peptide of the β-lactamase OXA-1 and the acetyltransferase. The gene lacked a plausible Shine-Dalgarno (SD) sequence and was located 45 nucleotides downstream from a small open reading frame, ORF-18, with a coding capacity of 18 amino acids and a properly spaced SD sequence likely to direct the initiation of aac(6′)-Ib11 translation. AAC(6′)-Ib11 had Leu118 and Ser119 as opposed to Gln and Leu or Gln and Ser, respectively, which were observed in all previously described enzymes of this type. We have evaluated the effect of Leu or Gln at position 118 by site-directed mutagenesis of aac(6′)-Ib11 and two other acetyltransferase gene variants, aac(6′)-Ib7 and -Ib8, which naturally encode Gln118. Our results show that the combination of Leu118 and Ser119 confers an extended-spectrum aminoglycoside resistance, with the MICs of all aminoglycosides in clinical use, including gentamicin, being two to eight times higher for strains with Leu118 and Ser119 than for those with Gln118 and Ser119.

Characterization of ESBL (SHV-12) producing clinical isolate of Enterobacter aerogenes from a tertiary care hospital in Nigeria

BackgroundWe studied the beta-lactamases of an E. aerogenes isolate recovered from the blood of a two-year-old patient. The isolate demonstrated a disk-diffusion phenotype typical for an AmpC-ESBL co-producer.MethodsMicrobiology studies were performed according to standard protocols. The resistance gene was identified by transconjugation and cloning experiments.ResultsBy transconjugation only a narrow spectrum beta-lactamase (TEM-1) encoded on a small plasmid was transmitted. The ESBL was cloned and expressed in an E. coli host. Sequence analysis of the recombinant plasmid revealed blaSHV-12 associated to the insertion sequence, IS26.ConclusionThis is the first study demonstrated the occurrence of SHV-12 in Nigeria.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii strains in intensive care units of multiple Mediterranean hospitals

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Outbreak of tularaemia in Golcuk, Turkey in 2005: Report of 5 cases and an overview of the literature from Turkey

Tularaemia was diagnosed by TaqMan RT-PCR and microagglutination tests in 5 patients, all from a new settlement constructed after the earthquake of 1999. During the follow-up, 129 more cases were found in this settlement (data from the local Health Care Authority). In this study, clinical features of 5 cases are presented briefly, and the Turkish literature on past outbreaks of tularaemia is reviewed.

Genetic and Enzymatic Properties of Metallo-β-Lactamase VIM-5 from a Clinical Isolate of Enterobacter cloacae

ABSTRACT A VIM-5-producing Enterobacter cloacae isolate (EDV/1) was identified in a collection of clinical strains stored before 2002. The gene, blaVIM-5, was located on a 2,712-bp BamHI-HindIII fragment of a 23-kbp (approximately) nonconjugative plasmid (pEDV5) in a class 1 integron as a single gene cassette.