Martin Steinbakk

Effects of Phenotype and Genotype on Methods for Detection of Extended-Spectrum-β-Lactamase-Producing Clinical Isolates of Escherichia coli and Klebsiella pneumoniae in Norway

ABSTRACT 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 blaTEM/SHV/CTX-M extended-spectrum-β-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-β-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.

Comparison of broad range 16S rDNA PCR and conventional blood culture for diagnosis of sepsis in the newborn: a case control study

BackgroundEarly onset bacterial sepsis is a feared complication of the newborn. A large proportion of infants admitted to the Neonatal Intensive Care Unit (NICU) for suspected sepsis receive treatment with potent systemic antibiotics while a diagnostic workup is in progress. The gold standard for detecting bacterial sepsis is blood culture. However, as pathogens in blood cultures are only detected in approximately 25% of patients, the sensitivity of blood culture is suspected to be low. Therefore, the diagnosis of sepsis is often based on the development of clinical signs, in combination with laboratory tests such as a rise in C – reactive protein (CRP). Molecular assays for the detection of bacterial DNA in the blood represent possible new diagnostic tools for early identification of a bacterial cause.MethodsA broad range 16S rDNA polymerase chain reaction (PCR) without preincubation was compared to conventional diagnostic work up for clinical sepsis, including BACTEC blood culture, for early determination of bacterial sepsis in the newborn. In addition, the relationship between known risk factors, clinical signs, and laboratory parameters considered in clinical sepsis in the newborn were explored.ResultsForty-eight infants with suspected sepsis were included in this study. Thirty-one patients were diagnosed with sepsis, only 6 of these had a positive blood culture. 16S rDNA PCR analysis of blinded blood samples from the 48 infants revealed 10 samples positive for the presence of bacterial DNA. PCR failed to be positive in 2 samples from blood culture positive infants, and was positive in 1 sample where a diagnosis of a non-septic condition was established. Compared to blood culture the diagnosis of bacterial proven sepsis by PCR revealed a 66.7% sensitivity, 87.5% specificity, 95.4% positive and 75% negative predictive value. PCR combined with blood culture revealed bacteria in 35.1% of the patients diagnosed with sepsis. Irritability and feeding difficulties were the clinical signs most often observed in sepsis. CRP increased in the presence of bacterial infection.ConclusionThere is a need for PCR as a method to quickly point out the infants with sepsis. However, uncertainty about a bacterial cause of sepsis was not reduced by the PCR result, reflecting that methodological improvements are required in order for DNA detection to replace or supplement traditional blood culture in diagnosis of bacterial sepsis.

Performance of Human Papillomavirus DNA and mRNA Testing Strategies for Women with and without Cervical Neoplasia

ABSTRACT In the present study we investigated the cross-sectional positivity for DNA and E6/E7 mRNA from high-risk human papillomavirus (HPV) types in 643 women with high-grade cervical neoplasia (135 cases of cervical intraepithelial neoplasia grade 2 [CIN2], 495 cases of CIN3/adenocarcinoma in situ [ACIS], and 13 cases of invasive carcinoma) and in 736 women with normal cytology by using the Amplicor and PreTect HPV-Proofer assays. In addition, genotyping was performed using Linear Array for women with normal cytology and a positive HPV test and in all women with histologically confirmed CIN2+. In women with normal cytology, 8.3% (61/736) were Amplicor positive and 3.3% (24/736) were PreTect HPV-Proofer positive (P < 0.001). Concordant results between the Amplicor and PreTect HPV-Proofer tests were present in 90.3% (665/736). In women with CIN2+ lesions 96.4% (620/643) were positive by Amplicor, 98.4% (633/643) by linear array, and 64.1% (412/643) by PreTect HPV-Proofer. Concordant results for the three HPV assays were present in 63.8%. The genotype profile detected by linear array and PreTect HPV-Proofer showed substantial agreement for HPV types 16, 18, 33, and 45. HPV type 16 and/or 18 was detected in 58.8% (378/643) of the women with high-grade neoplasia. Detection of E6/E7 mRNA by PreTect HPV-Proofer increased with severity of the cervical lesion. Detection of HPV DNA, however, was not associated with histology grade. In conclusion, the detection of HPV varied according to the assay used, and the concordance between the tests was poor. Our results indicate that mRNA testing may be a biomarker for progression of cervical neoplasia, but the optimal genotype mix remains to be determined.

HPV genotype distribution according to severity of cervical neoplasia

OBJECTIVE To analyse the HPV genotype profile and the presence of multiple HPV infections according to severity of cervical intraepithelial neoplasia. METHODS From a population of 424,143 women in Norway, we included all women (n=643) with histologically confirmed cervical intraepithelial neoplasia grade 2 or higher (CIN2+) and evaluable HPV test during 2005 and 2006. Histology revealed CIN2 in 135 women, CIN3/ACIS in 495, and invasive carcinoma in 13 women. HPV genotyping was performed on cell suspensions from cervix by linear array which differentiates 37 HPV genotypes. RESULTS HPV was detected in 98.4% (633/643) of the women, of whom 52.5% (338/643) were infected with more than one HPV genotype. HPV16 was most common, being detected in 51.2% (329/643) of all cases, followed by HPV31, 33, 52, 18, and 51. Overall, HPV 16 or 18 were detected in 58.0% (373/643), with 34.7% (223/643) without concurrence of other high-risk genotypes. HPV16 and HPV33 as single infections were more common in women with CIN3+ as compared to CIN2 (age-adjusted odds ratio=5.93, 95% CI=2.73-12.87, and age-adjusted odds ratio=4.53, 95% CI=1.42-14.46, respectively). Concurrent infection with other HPV genotypes did not significantly alter the associations to CIN3+ for HPV16 or HPV33. A single HPV infection, other than HPV16, 18, 31, or 33, was used as the reference. HPV18 or multiple HPV infections not including HPV16 or HPV33 were not associated with the severity of cervical neoplasia. CONCLUSION HPV16 and HPV33 appear to have a higher oncogenic potential than other HPV genotypes.

Infectious tenosynovitis and osteomyelitis caused by Mycobacterium nonchromogenicum

Infections due to Mycobacterium terrae complex are rare. We report a severe case of chronic tenosynovitis and osteomyelitis of the hand caused by Mycobacterium nonchromogenicum requiring second ray finger amputation.

Mycobacterium interjectum: a new pathogen in humans?

Molecular genetic techniques have increased the number of species recognized within the genus Mycobacterium. The clinical significance of these is uncertain and their pathogenic potential has still to be proven. We describe here a case of mycobacterial lymphadenitis in a Swedish boy, which supports the role of M. interjectum as a human pathogen.Molecular genetic techniques have increased the number of species recognized within the genus Mycobacterium. The clinical significance of these is uncertain and their pathogenic potential has still to be proven. We describe here a case of mycobacterial lymphadenitis in a Swedish boy, which supports the role of M. interjectum as a human pathogen.

Antibiotikaresistens må bekjempes globalt

MARTIN STEINBAKK Martin Steinbakk (f. 1951) er spesialist i medisinsk mikrobiologi og overlege ved Folkehelseinstituttet. Forfatter har fylt ut ICMJE-skjemaet og oppgir følgende interessekonflikter: Han har forelest ved noen kurs i regi av Legeforeningen og Universitetet i Oslo. Han er medlem i en ekspertgruppe for seksuelt overførbare sykdommer ved European Centre for Disease Prevention and Control.