What are the routes of entry for Group B Streptococcus in adult patients?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: September 29, 2026 • View editorial policy

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question

B群連鎖球菌の成人における侵入経路

成人におけるB群連鎖球菌（GBS）の主要な侵入経路は、消化管からの定着と二次的な泌尿生殖器への拡散であり、そこから血行性播種または直接侵襲によって全身感染を引き起こします。1

主要な侵入経路と病態生理

1. 消化管リザーバーからの経路

消化管がGBSの最も重要なヒト保菌部位であり、泌尿生殖器への二次的拡散の主要な供給源となります。1, 2 この経路は以下のように進行します：

  • 消化管での無症候性定着（成人の10-30%が保菌）1
  • 腸管から泌尿生殖器への細菌の移行
  • 局所感染または血行性播種への進展

最近の研究では、GBSが腸管上皮細胞に選択的に付着し、カベオラ依存性およびリピッドラフト依存性のエンドサイトーシスを介して侵入することが示されています3。また、GBSは細胞間接合部を一過性に開放させることで、傍細胞経路を通じて上皮バリアを通過することも確認されています4。

2. 臨床的侵入部位

成人における具体的な感染経路は以下の通りです：

皮膚・軟部組織感染

  • 最も一般的な臨床症状1, 5, 6
  • 直接的な皮膚バリアの破綻から侵入

泌尿生殖器感染

  • 消化管からの定着後に発生1, 5, 6
  • 尿路感染症として顕在化し、菌血症への門戸となる

血行性播種

  • 菌血症は成人GBS感染の主要な臨床像1, 5, 6
  • 血液培養陽性率は78.7%7
  • 遠隔部位への播種により肺炎、髄膜炎、心内膜炎、骨髄炎を引き起こす

院内感染経路

  • 静脈カテーテル留置に関連した感染が頻繁に発生6
  • 医療器具を介した直接的な血管内侵入

高リスク患者における特徴

成人GBS感染の86%は基礎疾患を有する患者で発生します7：

  • 糖尿病：最も重要なリスク因子1, 5, 6
  • 悪性腫瘍5
  • 肝疾患5
  • 神経学的障害6
  • 高齢者（60歳以上で発生率が最も高い）5

臨床的注意点

致死率は成人で15-32%と高く1、特に高齢者と合併症を有する患者で予後不良です7。 髄膜炎の場合、致死率は34.4%に達し、高齢（平均61.5歳）と入院時の合併症が予後不良因子となります7。

重要な落とし穴：

  • 血液培養陽性患者の50%に遠隔感染巣が存在するため7、菌血症が確認された場合は全身的な感染源検索が必須
  • 再発率は4.3%であり6、初回治療後も注意深い経過観察が必要
  • 院内感染と多菌性菌血症が有意な割合で発生するため5、複数の病原体を考慮した治療戦略が必要

References

6
Research

Group B streptococcal disease in nonpregnant adults.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2001

7
Research

Group B streptococcal meningitis in adults: report of twelve cases and review.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 1997

Related Questions

How should I locate the source of a Group B Streptococcus infection in an adult patient?
What are the routes of entry for Group B Streptococcus (Streptococcus agalactiae)?
Does streptococcal pharyngitis present differently in elderly patients?
Does a urine culture with 10,000-25,000 CFU/mL of Beta-hemolytic Streptococcus, group B require antibiotic treatment?
What is the recommended treatment for a 67-year-old female with a mild, symptomatic urinary tract infection due to Group B Streptococcus?
In irritable bowel syndrome, does abdominal pain typically improve markedly after a bowel movement?
What are the roles and recommended doses of N‑acetylcysteine, taurine, enalapril, telmisartan, and alpha‑ketoanalogues in a patient with stage 1 chronic kidney disease?
What are the routes of entry for Group B Streptococcus (Streptococcus agalactiae)?
In a 52-year-old obese man with hypertension, hyperlipidemia, atrial fibrillation on apixaban, an angiotensin receptor blocker (ARB), and atorvastatin, who has daytime sleepiness (Epworth Sleepiness Scale 16), loud snoring, witnessed breathing pauses, and an in‑home sleep test showing fewer than three events per hour, what is the next best step in management?
In a 66-year-old male (88.6 kg, creatinine 1.29 mg/dL, eGFR 61 mL/min/1.73 m²) on continuous tube feeding (232 g carbohydrate per 24 h) who received 30 units of NPH insulin at 2100 h with an insulin‑sensitivity factor of 25 mg/dL per unit and blood glucose readings of 146 mg/dL at 2100 h, 97 mg/dL at midnight, and 70 mg/dL at 0320 h, what should his morning NPH insulin dose be at 8 am and what should his insulin‑sensitivity factor be?
How should I locate the source of a Group B Streptococcus infection in an adult patient?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.