Microbiological and clinical characteristics of Streptococcus gallolyticus subsp. pasteurianus infection in China

Abstract

Background: Infections by Streptococcus gallolyticus subsp. pasteurianus (SGSP) is often underestimated. Herein, the epidemiological features and resistant characteristics of SGSP in mainland China are characterized to enable a better understanding of its role in clinical infections.

Methods: In the present work, 45 SGSP isolates were collected from the samples of bloodstream, urine, aseptic body fluid, and fetal membrane/placenta from patients in 8 tertiary general hospitals of 6 cities/provinces in China from 2011 to 2017. The identification of all isolates was performed using traditional biochemical methods, 16S rRNA and gyrB sequencing, followed by the characterization of their antibiotic resistance profiling and involved genes.

Results: Among 34 non-pregnancy-related patients, 4 (4/34,11.8%) patients had gastrointestinal cancer, 10 (10/34, 29.4%) patients had diabetes, and one patient had infective endocarditis. Moreover, 11 cases of pregnant women were associated with intrauterine infection (9/11, 81.2%) and urinary tract infection (1/11, 9.1%), respectively. Except one, all other SGSP isolates were correctly identified by the BD Phoenix automated system. We found that all SGSP isolates were phenotypically susceptible to penicillin, ampicillin, cefotaxime, meropenem, and vancomycin. Forty strains (40/45, 88.9%) were both erythromycin and clindamycin-resistant, belonging to the cMLS_B phenotype, and the majority of them carried erm(B) gene (39/40, 97.5%). Although the cMLS_B/erm(B) constituted the most frequently identified phenotype/genotype combination (25/40, 62.5%) among all erythromycin-resistant cMLS_B isolates, erm(B)/erm(A), erm(B)/mef(A/E), and erm(B)/erm(T) was detected in 7, 4, and 3 isolates, respectively. Furthermore, 43 strains (43/45, 95.6%) were tetracycline-resistant, and out of these, 39 strains (39/45, 86.7%) carried tet(L), 27(27/45, 60.0%) strains carried tet(O), and 7 (7/45, 15.6%) strains carried tet(M), alone or combined, respectively. All erythromycin-resistant isolates were also resistant to tetracycline.

Conclusions: It is important to study and draw attention on SGSP, an underreported opportunistic pathogen targeting immunodeficient populations, notably elderly subjects, pregnant women and neonates.

Keywords: Antibiotic resistance; Intrauterine infection; Streptococcus gallolyticus subsp. pasteurianus.

Fig. 1

Geographical locations and numbers of Streptococcus gallolyticus subsp. pasteurianus (SGSP) isolates. The colored provinces represent where SGSP strains were isolated, with the number of isolates shown in brackets

Fig. 2

Distribution of the 45 strains of Streptococcus gallolyticus subsp. pasteurianus (SGSP) in different infections

Fig. 3

Relationship between infection sources and ages in 34 cases of non-pregnancy-related infections caused by Streptococcus gallolyticus subsp. pasteurianus (SGSP)

Fig. 4

Phylogenetic tree constructed by the neighbour-joining method based on the nucleotide sequences of the 16S rRNA genes of 45 clinical Streptococcus gallolyticus subsp. pasteurianus (SGSP) strains and one reference strain AJ297216.1