Reduced penicillin susceptibility of group B Streptococcus: an assessment of emergence in Grampian, Scotland

Streptococcus agalactiae: Identification methods, antimicrobial susceptibility, and resistance genes in pregnant women

BACKGROUND

Group B Streptococcus (GBS) is a normal component of the gastrointestinal and genital microbiota in humans and can lead to important infections in newborns.

AIM

To compare GBS isolation and identification methods as well as to assess the antibiotic susceptibility and to identify resistance genes in GBS strains from pregnant women attended in healthcare services from the city of Vitória da Conquista, in Bahia State, Brazil.

METHODS

From January 2017 to February 2018, vaginorectal swabs were obtained from 186 participants and the samples were seeded onto chromogenic agar for GBS before and after inoculation in selective broth. Confirmatory identification using 3 CAMP and latex tests was performed in samples with GBS-suggestive colonies. Then, disk diffusion antibiograms were performed in GBS-positive samples, and the detection of the resistance genes ermB, ermTR, mefA, and linB in the clindamycin and/or erythromycin-resistant samples was carried out.

RESULTS

Thirty-two samples (17.2%) were GBS-positive. The culture in chromogenic agar after sample incubation in selective broth was the most sensitive method (96.9%) for GBS detection. All isolates were susceptible to penicillin, ampicillin, cefotaxime, and vancomycin. Clindamycin resistance was observed in 6 samples (18.8%), while 8 samples (25%) were erythromycin-resistant. All erythromycin and/or clindamycin-resistant GBS strains had negative D-tests. Two strains (25%) presented an M phenotype and 6 isolates (75%) presented a cMLSB phenotype. The ermB gene was identified in 4 samples (44.4%), the mefA gene was also found in 4 samples (44.4%), the ermTR gene was identified in 1 isolate (11.1%), and the linB gene was not found in any isolate.

CONCLUSION

This study evidenced that the screening for SGB can be performed by means of various methods, including chromogenic media, and that the chemoprophylaxis for pregnant women who cannot use penicillin must be susceptibility-guided.

Streptococcus agalactiae in pregnant women: serotype and antimicrobial susceptibility patterns over five years in Eastern Sicily (Italy)

Streptococcus agalactiae (also known Group B Streptococcus or GBS) represents the main pathogen responsible for early- and late-onset infections in newborns. The present study aimed to determine the antimicrobial susceptibility pattern and the capsular serotypes of GBS isolated in Eastern Sicily over 5 years, from January 2015 to December 2019. A total of 3494 GBS were isolated from vaginal swabs of pregnant women (37–39 weeks), as recommended by the Centers for Disease Control and Prevention. Capsular polysaccharide’s typing of GBS was determined by a commercial latex agglutination test containing reagents to serotypes I–IX. The antimicrobial resistance pattern of GBS was determined through the disk diffusion method (Kirby-Bauer) and the double-disk diffusion test on Mueller-Hinton agar plates supplemented with 5% defibrinated sheep blood, according to the guidelines of the Clinical and Laboratory Standards Institute. Serotypes III (1218, 34.9%) and V (1069, 30.6%) were the prevalent colonizers, followed by not typable (570, 16.3%) and serotypes Ia (548, 15.7%), Ib (47, 1.3%), II (40, 1.1%), and IV (2, 0.1%). All 3494 clinical isolates were susceptible to cefditoren and vancomycin. Resistance to penicillin, ampicillin, levofloxacin, clindamycin, and erythromycin was observed in 6 (0.2%), 5 (0.1%), 161 (4.6%), 1090 (31.2%), and 1402 (40.1%) of the strains, respectively. Most of erythromycin-resistant GBS (1090/1402) showed the cMLS_B phenotype, 276 the M phenotype, and 36 the iMLS_B phenotype. Our findings revealed a higher prevalence of serotype III and a relevant resistance rate, among GBS strains, to the most frequently used antibiotics in antenatal screening.

A Case Report of Cerebral Meningitis Caused by Penicillin-Non-Susceptible Group B Streptococcus in an Immunocompromised Adult Patient

Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is the leading cause of bacteremia and meningitis in neonates; however, it also causes meningitis in adults, although much less frequently. After the detection of penicillin-non-susceptible GBS (PRGBS) for the first time in 2008 by Japanese researchers, clinical PRGBS isolates have been reported worldwide. These isolates need to be given due attention for being non-susceptible to multiple drugs. Herein, we present the first clinical report of meningitis caused by PRGBS. A 41-year-old Japanese male receiving an immunosuppressant visited hospital complaining of fever. Although he did not have meningitis-related symptoms or physical findings, determination of the cause of fever by Gram-staining of the spinal fluid revealed gram-positive cocci in pairs and chains. Initially, he was hospitalized on the diagnosis of cerebral meningitis caused by Streptococcus pneumoniae. However, culture of the spinal fluid revealed the β-hemolytic colonies on blood agar. Biochemical testing and mass spectrometry revealed the isolated organism as GBS (serotype Ib). The minimum inhibitory concentration (MIC) of penicillin G for the isolated strain was 0.5 μg/mL, which is greater than the MIC criteria for “susceptibility” to penicillin G for beta-hemolytic streptococci according to Clinical and Laboratory Standards Institute standards. The isolated strain was also resistant to macrolide (MIC ≥ 8 μg/mL) and fluoroquinolone (MIC ≥ 8 μg/mL). The patient recovered without neurologic sequelae upon treatment with ceftriaxone, vancomycin, and corticosteroids for 4 days, and subsequently with ampicillin for 17 days. The rate of isolation of PRGBS in the clinics has gradually increased, particularly in Japan. Although PRGBS isolated in the present case was susceptible to ampicillin and cephalosporins, strains not susceptible to ampicillin, cefotaxime, and ceftriaxone have already been isolated, indicating the prospects for limited range of effective antibiotics against PRGBS infections, including meningitis, in the near future.

Cross-resistance to lincosamides, streptogramins A and pleuromutilins in Streptococcus agalactiae isolates from the USA

Background

Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading cause of meningitis, sepsis and pneumonia in neonates in the United States. GBS also causes invasive disease in older infants, pregnant women, children and young adults with underlying medical conditions, and older adults. Resistance to lincosamides in the absence of erythromycin resistance is rare in GBS, but has been previously reported in clinical isolates, both on its own or in combination with resistance to streptogramins A and pleuromutilins (L/LSA/LSAP phenotypes).

Objectives

To retrospectively screen the Active Bacterial Core surveillance (ABCs) GBS isolate collection for these phenotypes in order to identify the causal genetic determinants and determine whether their frequency is increasing.

Methods

Based on MIC data, 65 (0.31%) isolates susceptible to erythromycin (MIC ≤0.25 mg/L) and non-susceptible to clindamycin (MIC ≥0.5 mg/L) were identified among 21 186 GBS isolates. Genomic DNA was extracted and WGS was performed. The presence of 10 genes previously associated with LSA resistance was investigated by read mapping.

Results

Forty-nine (75%) isolates carried the lsa (C) gene and expressed the LSAP phenotype, and 12 (18%) carried both the lnu (B) and lsa (E) genes and expressed the LSAP phenotype. The four remaining isolates were negative for all determinants investigated.

Conclusions

While the overall observed frequency of these phenotypes among our GBS isolates was quite low (0.31%), this frequency has increased in recent years. To the best of our knowledge, this is the first time the LSAP phenotype has been reported among GBS isolates from the USA.