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

Abstract

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.

Bacterial isolation and antibiotic susceptibility from diabetic foot ulcers in Kenya using microbiological tests and comparison with RT-PCR in detection of S. aureus and MRSA

“…PCR revealed pathogens that had not been recognized by culture-methods such as MRSA species. Previous research reveals a higher specificity for culture tests when compared to RT-PCR as a reference while a lower sensitivity, a slightly higher PPV and a higher NPV [8]. Similar to this earlier study, RT-PCR revealed more S. aureus than identified through culture-methods [8].…”

“…However, more accurate tests should be explored since culture-based methods have been reported to have a high number of false-negatives [8]. In the present study, molecular tests were more sensitive but less specific than culture-based methods.…”

Staphylococcus aureus Toxins and Diabetic Foot Ulcers: Role in Pathogenesis and Interest in Diagnosis

“…ST80 is the main PVL clone circulating in Europe and North Africa [ 147 , 148 , 149 ]. Rates of PVL-producing clones in DFI remain low in comparison to data concerning SSTIs [ 127 ] (e.g., the epidemic furuncles (42%), major abscesses (73%) and gold surgically-drained abscesses (89%)) [ 146 , 150 , 151 , 152 ]. Indeed, in DFI, a higher incidence of PVL-positive isolates among subjects with CA-MRSA could be observed (31.8% versus 5.7%; p = 0.004) [ 153 ].…”

“…The PVL-producing clones were rarely isolated from DFI ( Table 2 ) [ 48 , 110 , 122 , 144 , 145 ]. However, this prevalence varies between countries: France (~3%), Algeria and The Netherlands (~14%) [ 48 , 146 ]. The main PVL-producing strains isolated from DFI belong to ST80-MRSA (14/21 strains), followed by ST152 (6/21) and CC30 (1/21).…”

Association of soft tissue infection in the extremity with glucose and lipid metabolism and inflammatory factors

“…In addition, the elevated contents of carbohydrates and proteins in the exudates of injured soft tissues are beneficial to the survival and reproduction of bacteria, which extremely easily trigger soft tissue infection in the extremity, especially the feet ( 7 , 8 ). Large number of studies have demonstrated that the pathogens of infection are dominated by Gram-negative bacteria possessing strong drug resistance ( 9 ). Defects of the soft tissue in the extremity of DF patients heal more slowly than those in other parts because they are located far away from the heart and have less collateral circulation and blood supply than other parts.…”