Archive for September 6, 2015

Direct molecular versus culture-based assessment of Gram-positive cocci in biopsies of patients with major abscesses and diabetic foot infections

European J of Clinical Microb & Inf Diseases SEPT 2015 V.34 N.9 P.1885-1892

  1. H. T. Stappers, F. Hagen, P. Reimnitz…
  2. Department of Internal Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
  3. Department of Medical Microbiology and Infectious Diseases, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands
  4. Hasselt University, Hasselt, Belgium
  5. Bayer Healthcare Pharmaceuticals, Wuppertal, Germany
  6. Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
  7. Department of Medical Microbiology and Infectious Diseases, Erasmus MC, Rotterdam, The Netherlands

Major abscesses and diabetic foot infections (DFIs) are predominant subtypes of complicated skin and skin structure infections (cSSSIs), and are mainly caused by Staphylococcus aureus and β-hemolytic streptococci.

This study evaluates the potential benefit of direct pathogen-specific real-time polymerase chain reaction (PCR) assays in the identification of causative organisms of cSSSIs.

One-hundred and fifty major abscess and 128 DFI biopsy samples were collected and microbial DNA was extracted by using the Universal Microbe Detection kit for tissue samples.

Pathogen-specific PCRs were developed for S. aureus and its virulence factor Panton–Valentine leukocidin (PVL), Streptococcus pyogenes, S. agalactiae, S. dysgalactiae, and the S. anginosus group.

Identification by pathogen-specific PCRs was compared to routine culture and both methods were considered as the gold standard for determination of the sensitivity and specificity of each assay.

Direct real-time PCR assays of biopsy samples resulted in a 34 % higher detection of S. aureus, 37 % higher detection of S. pyogenes, 18 % higher detection of S. agalactiae, 4 % higher detection of S. dysgalactiae subspecies equisimilis, and 7 % higher detection of the S. anginosus group, compared to routine bacterial culture.

The presence of PVL was mainly confined to S. aureus isolated from major abscess but not DFI biopsy samples.

In conclusion, our pathogen-specific real-time PCR assays had a higher yield than culture methods and could be an additional method for the detection of relevant causative pathogens in biopsies.





September 6, 2015 at 6:58 pm

Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy

European J of Clinical Microb & Inf Diseases SEPT 2015 V.34 N.9 P.1797-1802

  1. Gherardi, D. Petrelli, M. C. Di Luca…
  2. University Campus Bio-Medico, 00128, Roma, Italy
  3. School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
  4. Department of Microbiology and Infection Control, University Hospital of North Norway, 9038, Tromsø, Norway
  5. Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
  6. Unit of Microbiology, Bambino Gesù Children’s Hospital, Roma, Italy
  7. Azienda Ospedaliera di Perugia, Struttura Complessa di Microbiologia, Santa Maria della Misericordia Hospital Perugia, Perugia, Italy
  8. Azienda Ospedaliera di Macerata, Macerata, Italy
  9. School of Pharmacy, Microbiology Unit, University of Camerino, via Gentile III da Varano, 62032, Camerino, MC, Italy

Macrolides are often used to treat group A streptococcus (GAS) infections, but their resistance rates reached high proportions worldwide.

The aim of the present study was to give an update on the characteristics and contemporary prevalence of macrolide-resistant pharyngeal GAS in Central Italy.

A total of 592 isolates causing pharyngitis in children were collected in the period 2012–2013. Clonality was assessed by emm typing and pulsed-field gel electrophoresis (PFGE) for all macrolide-resistant strains and for selected susceptible isolates.

Genetic determinants of resistance were screened by polymerase chain reaction (PCR). Forty-four GAS were erythromycin-resistant (7.4 %).

Among them, 52.3 % and 50 % were clindamycin- and tetracycline-resistant, respectively. erm(B)-positive isolates (52.3 %) expressed the constitutive cMLSB phenotype. mef(A) and its associated M phenotype were recorded in 40.9 % of the cases.

The remaining erm(A)-positive isolates expressed the iMLSB phenotype. Seventeen tetracycline-resistant isolates carried tet(M) and five isolates carried tet(O). Twenty-five emm types were found among all strains, with the predominance of emm types 12, 89, 1, and 4.

Eleven emm types and 12 PFGE clusters characterized macrolide-resistant strains, with almost two-thirds belonging to emm12, emm4, and emm11. Macrolide-susceptible and -resistant emm types 12, 89, 11, and 4 shared related PFGE profiles.

There was a dramatic decline in macrolide resistance in Central Italy among pharyngeal GAS isolates in 2012–2013 when compared to previous studies from the same region (p<0.05), although macrolide consumption remained stable over the past 15 years.

We observed a decrease in the proportion of macrolide-resistant strains within emm types commonly associated with macrolide resistance in the past, namely emm12, 1, and 89.





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September 6, 2015 at 6:55 pm


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