The U.S. CDC revised GBS prevention and cure guideline in 2010 and advised to collect vaginal and rectal swab from all pregnant women with 35–37 weeks’ gestation for GBS screening. By screening for GBS colonization during childbirth and using antibiotics prophylactic medication for pregnant women in labor with GBS colonization, severe complications caused by early-onset neonatal GBS were greatly decreased [6, 34–36]. In recent years, GBS screening has been carried out in China, especially in developed regions such as Beijing and Shanghai where GBS screening policies are widely implemented. Notably, it was the big limitations on antibiotic range selected for infection prevention to those women who are high-risk and susceptible to Penicillin due to increased resistance to iMLSB GBS. CDC recommends using Vancomycin for such population, however, Vancomycin has a potential damage to animal embryos. GBS vaccines against non-pregnant adults can effectively prevent bacteremia, however, such research has not been applied to clinical treatment in China. Besides, as is known to all, China is a developing country with large population base. Now the two-child policy has been gradually liberalized and plenty of child-bearing age women are facing with the possibility of another pregnancy. Therefore, the drug resistance, MLST typing and drug resistance gene analysis of iMLSB GBS are of great significance in clinical diseases such as urogenital tract inflammation and unexplained abortion in Chinese women of reproductive age.
In this study, 1021 isolates collected from 31894 patients were received systematic analysis, of which 8.82% of GBS detection was found in Obstetrics of cervix secretion higher than the detection rate of other sample types, so in Obstetrics patients, GBS monitoring is extremely important and necessary in our country. The detection rate of 1021 strains of GBS among different ages in Gynecology & Obstetrics departments showed statistical significance (P༜0.01). Among the patients with obvious local clinical symptoms in this study, the detection rate of gynaecological GBS was 3.49% and that of obstetrical GBS was 2.68%, which was much lower than that of healthy women. The maximum number of GBS detection came from the group with Cervix secretion and Age 21–40. The highest rate of GBS detection came from the group with Cervix secretion and Age 41–60. This might be related to the features of GBS, the change of sex hormone levels and the decrease of immunity in these groups. With the China’s family planning policy opening, the increase of parturient women over Age 40 also may brought the growth of GBS detection in Obstetrics for Age 41–60 group compared with those in previous years.
For the resistance patterns of GBS in this study, none of the 1021 strains were resistant to Penicillin, Vancomycin or Linezolid, which was similar to the most of the other countries and regions[8, 39]. By statistically analyzing the resistance patterns of strains in this study, among 493 strains resistant to Erythromycin, 84% of them were resistant to Clindamycin and this was greater than the percentage in Italy (53%). The resistance to Erythromycin, Clindamycin and Levofloxacin conformed to bacterial resistance surveillance data published by Shanghai . The drug resistance rate of Erythromycin was higher than the reported data in Italy (15%), Brazil (19.3%) , the United States (38%-41.9%) , France (35.3%) , and South Korea (51.8%) etc. The resistance to Clindamycin was also larger than the values of most states & regions, for example, Brazil (13.3%) and Africa (17.2%) [40, 44]. However, it was a bit lower than the rate in South Korea (55.4%) and this may attribute to its social structure & medical level . There were 140 isolates susceptible or intermediate to Clindamycin, including 63 iMLSB GBS and positive rate of D-test reached 45.0%, which was greatly improved by comparing with the positive rate (21.7%) through D-test during 2009–2012 reported in Shanghai . It was much higher than the rate in Brazil (20%) and Africa (17.4%) [44, 46]. Understanding the distribution of GBS infection and drug resistance is of great significance for guiding rational drug use in clinical practice, especially for the rational drug use of iMLSB GBS strain. Therefore, it is imperative to strengthen the monitoring of GBS resistance.
In this study, largest number of iMLSB GBS isolates was CC19 and the maximum relating to inflammation of pregnancy women in Obstetrics was CC19. The highest incidence of cervical inflammation in Gynecology was CC19 and adverse pregnancy outcomes in Birth Control Department was ST12. In other states and regions, CC19, CC1, CC10 and CC17 were the most in Romania from Eastern Europe and CC23, CC19 and CC17 were mainly detected in Poland from Central Europe [47, 48]. Like Iran, the most common clonal complexes were CC19 and CC10 [39, 49]. CC17 was the main GBS strains to induce invasive diseases of newborn babies in Beijing, China . At the same time, CC17 was predominant in GBS neonatal infections in France [42, 50]. CC17 strains cause both neonatal and adult invasive infections which cluster tightly in a phylogenetic tree, signifying that they are derived from the same genetic pool in Canada . The research to capsular polysaccharide on virulent strain’s surface had important implications for the development of GBS vaccine .
Multiple resistance isolates severely threaten the public health due to the pressure selection of antibiotics. Among 63 iMLSB GBS isolates, the drug resistance rate of ST19 to Levofloxacin (75.0%) was higher than that of other types, while ST12 was susceptible to Levofloxacin. Similarly, the predominant genotype of the levofloxacin-resistant isolates was ST19 in Taiwan . This rate was close to that of ST19 from non-genitourinary tract specimens reported in Shanghai (76.9%). and lower than III/ ST19 resistance to Levofloxacin in Beijing (> 90%) . What's different is that ST19 was reported as the isolates with lower susceptibility to Penicillin in Japan . Those strains not susceptible to Penicillin were usually resistant to macrolides and fluoroquinolone antibiotics. The drug resistance rate of CC10 to Levofloxacin (7.69%) was obviously lower than Korean . We found the distinct gaps and genetic diversity exist in the drug resistance and relevant resistance genes with different ST types. These data suggested that the epidemiological investigation of GBS MLST in Shanghai has important clinical reference.
Resistance to erythromycin in neonatal invasive GBS has been reported worldwide, and the resistance to erythromycin from GBS strains was mostly mediated by ermB, ermA and mef. In the 63 erythromycin resistant strains, 26.98% of the strains contained the mefA gene, and 41.27% of the strains contained the mefB resistance gene, while only 6.34% shared the mefA and mefB genes together. This was close to ermB relevance ratio for Erythromycin resistant GBS strains in Suzhou (47.1%), and similar to the result of the relevance ratio of mefA in Beijing (27%), while the rate of ermB in Beijing (94.6%). In Africa, the relevance ratio of mefA was merely 3.4% but ermB was 55%. In South Korea, there was low relevance ratio of mefA (3.4%) and high rate of ermB (82.8%). A high ratio of ermB (83.1%) also existed in strains not susceptible to Erythromycin in Taiwan. In Portugal, the relevance ratio of ermB was 25.9% in GBS resistant to Erythromycin. According to the statistics reported by Federal University of Brazil, no mefA was found and only few ermB (27.8%) were detected in GBS resistant to Erythromycin .
The relevance ratio of mefA and ermB was 27.0% and 41.3% respectively in this study and only 4 strains included the both genetypes, which was close to ermB relevance ratio (47.1%) and largely different to mefA relevance ratio (0%) for Erythromycin resistant GBS strains separated from urine specimen in Suzhou, China[57, 58]. In general, Erythromycin resistance induced by efflux pump was negative in D-test. However, 27% of induced resistant strains included mefA and was mostly concentrated on CC19 in this research. These isolates might spontaneously mutate from induced resistance to structural resistance and continue to show high resistance to Erythromycin. Treatment with clindamycin may induce antibiotic strain resistance, even leading to treatment failure. Therefore, the further study of CC19 spontaneously-mutated isolates could be regarded as the important supplement to GBS resistance system and gave the guidance on rational use of antibiotics for clinicians to avoid the occurrence of drug resistance.
In general, Erythromycin resistance induced by efflux pump was negative in D-test. However, induced resistant strains included mefA and ermB were mostly concentrated on CC19 in this research. Such isolates might spontaneously mutate from induced resistance into structural resistance during the course of treatment and continually expressed high resistance to Erythromycin. Previous research indicated that resistance induced by Clindamycin was almost caused by ribosomal RNA methylation modification. By detecting gene ermB related to ribosome methylation commonly found in China, 18 strains of 19 GBS isolates with ST12 were detected to contain ermB and 16 strains with ST19 cannot be verified to contain ermB. 58.7% of such isolates did not include ermB and most of them still concentrated on CC19 in this study. In additions, only 3 of 7 alleles were different and there was close affinity between the new genotype ST1072 and ST19. Therefore, the further study of CC19 spontaneously-mutated isolates could be regarded as the important supplement to GBS resistance system and gave the guidance on rational use of antibiotics for clinicians to avoid the occurrence of drug resistance. So it should explore more methods and researches about CC19 gene group of induced resistant isolates in local region. It may provide a key piece of information about the GBS resistance system study in China.