16S rDNA PCR Improves Bacterial Pyomyositis Diagnosis

Using a broad-range polymerase chain reaction (PCR) technique targeting 16S ribosomal DNA may improve the diagnosis and treatment of bacterial pyomyositis, according to study results published in the Journal of Infection.

Bacterial pyomyositis is a rare infection of the skeletal muscle and diagnosing the disease is challenging due to nonspecific initial symptoms that may last for approximately 23 days before hospitalization is initiated. The current diagnostic gold standard for bacterial pyomyositis is aspiration of purulent material, which is cultured to identify the causative agent. Once the specific bacteriais identified, empirical treatment with broad-spectrum antibiotics is initiated. However, because the authentic epidemiology of pyomyositis is not known, empirical treatment is tenuous. Further, in most patients who receive antibiotics, the cultures obtained are often sterile, adding to the difficulty in diagnosing bacterial pyomyositis.

Broad-range PCR targeting 16S ribosomal DNA (16S rDNA PCR) is useful in patients who have been treated with antibiotics because it allows the identification of bacterial pathogens in culture-negative clinical samples. Using this tool for diagnosis may be more accurate and rapid than the gold standard culture. Therefore, this prospective study compared the results of using 16S rDNA PCR vs culture in patients with pyomyositis.

A total of 12 patients were included in the study due to the rarity of pyomyositis. All patients were admitted to the infectious disease unit of the Hôpital Bichat – Claude-Bernard, Hôpitaux Universitaires Paris Nord Val de Seine, France and underwent needle aspiration of pus from muscle for the microbiologic diagnosis of pyomyositis. The collected purulent material was distributed between 3 tubes for microscopic analysis, routine culture, and 16S rDNA PCR analysis using the SepsiTest kitTM (Molzym GmbH, Bremen, Germany), according to the manufacturer’s instructions. The PCR analysis was performed with blinding to the culture results.

Of the included patients, 7 were women, mean age was 58 years (range 34 to 89 years), and 7 had an underlying disease or condition: HIV infection (n=2), cancer (n-2), hemodialysis (n=2), and cirrhosis (n=1). Of the remaining 5 patients, 4 had no notable medical history and 1 had Streptococcus agalactiae endocarditis 6 months prior to admission. At the time of aspiration of purulent material, all patients were receiving a median 23 days of antibiotic treatment. Using 16S rDNA PCR, the bacteria was identified from the pus in all cases.

Results showed that the 16S rDNA PCR results were in agreement with those of routine culture in all culture-positive cases. In 5 patients, the bacteria from cultures of pus samples were identified and in agreement with those identified by 16S rDNA PCR. In 4 patients, pus cultures were sterile but concomitant cultures of blood or synovial fluid samples identified bacteria that were in agreement with those identified by 16S rDNA PCR. In the 3 remaining patients, the microbiologic analysis yielded in negative results, but the 16S rDNA PCR did not. The medical history of these patients correlated with the 16S rDNA PCR findings.Researchers therefore highlight that cases of negative culures, PCR may guide a switch from broad- to narrow-spectrum antibiotic treatment.

Overall, the study authors concluded that, “We suggest that 16S rDNA PCR be applied in all cases of pyomyositis, particularly when bacterial cultures are negative.”

Reference

Gabas T, Podglajen I, Cheminet G, Gagnard JC, Wyplosz. Diagnostic accuracy of 16S rDNA PCR in bacterial pyomyositis: a prospective study [published online August 17, 2019]. Journal of Infection. doi:10.1016/j.jinf.2019.08.008