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Concise Communication
Outbreak of postpartum group a Streptococcus infections on a labor
and delivery unit
Michael Haden MD1, Christina Liscynesky MD2
,
3, Nora Colburn MD2
,
3, Justin Smyer MPH3,
Kimberly Malcolm DNP3, Iahn Gonsenhauser MD4, Kara M. Rood MD5, Patrick Schneider MD5,
Michele Hardgrow BSN6, Preeti Pancholi PhD7, Keelie Thomas MPH8, Anita Cygnor MS9, Oluseun Aluko MBChB10,
Elizabeth Koch MD10, Naomi Tucker MPH10, Jade Mowery MPH11, Eric Brandt BS11, Katie Cibulskas BS12,
Marika Mohr MS12, Srinivas Nanduri MD13 , Sopio Chochua MD13 and Shandra R. Day MD2
,
3
1Department of Internal Medicine, Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Denver, CO, USA, 2Department of Internal
Medicine, Division of Infectious Diseases, The Ohio State University Wexner Medical Center, Columbus, OH, USA, 3Clinical Epidemiology, The Ohio State
University Wexner Medical Center, Columbus, OH, USA, 4Lee Memorial Health System, Fort Myers, FL, USA, 5Department of Obstetrics and Gynecology, The Ohio
State University Wexner Medical Center, Columbus, OH, USA, 6Occupational Health and Wellness, The Ohio State University Wexner Medical Center, Columbus,
OH, USA, 7Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH, USA, 8Clinical Microbiology, The Ohio State University
Wexner Medical Center, Columbus, OH, USA, 9Department of Women and Infants, The Ohio State University Wexner Medical Center, Columbus, OH, USA,
10Columbus Public Health, Columbus, OH, USA, 11The Ohio Department of Health Laboratory, Reynoldsburg, OH, USA, 12The Ohio Department of Health,
Columbus, OH, USA and 13Respiratory Diseases Branch, Division of Bacterial Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
Abstract
A healthcare-associated group A Streptococcus outbreak involving six patients, four healthcare workers, and one household contact occurred
in the labor and delivery unit of an academic medical center. Isolates were highly related by whole genome sequencing. Infection prevention
measures, healthcare worker screening, and chemoprophylaxis of those colonized halted further transmission.
(Received 27 December 2023; accepted 12 April 2024)
Introduction
Streptococcus pyogenes, also known as group A Streptococcus
(GAS), causes both noninvasive and invasive infections including
bacteremia, necrotizing fasciitis, and streptococcal toxic shock
syndrome. Although invasive GAS infections account for a small
proportion of total GAS disease, they can result in significant
morbidity and mortality with a case fatality rate of 11.7% based on
national epidemiologic data.1,2
Human skin and mucous membranes are the primary reservoir
for GAS, with colonization of the throat being the most common;
colonization of the skin, rectum, and vagina occurs to a lesser
extent.3–5While carriage rates are much higher in school-aged
children, adult colonization is of particular concern, especially
among healthcare workers (HCWs), given the risk for potential
healthcare-associated spread of infection.6Postpartum women
have a 20-fold increased incidence of invasive GAS infection
compared with nonpregnant women due to disruption of
cutaneous or mucosal barriers during delivery, with approximately
220 postpartum cases occurring annually in the United States.3,7
GAS can be community-acquired from exposure or colonization
with GAS prior to delivery or healthcare-acquired via transmission
from a colonized HCW. Given the risk for healthcare-acquired
infection and severity of disease for postpartum GAS infections, a
prompt epidemiological investigation is recommended once a
single case of postpartum GAS infection has been identified.
An epidemiological investigation was performed at a large
academic medical center beginning in June 2019 to investigate six
cases of invasive postpartum GAS infections occurring over four
months.
Methods
Case definition
According to the 2002 Centers for Disease Control and Prevention
(CDC) guidelines, postpartum invasive GAS is defined as isolation,
during the postpartum period, of GAS in association with a clinical
postpartum infection (e.g., endometritis) or from either a sterile
site or wound infection. The postpartum period of interest includes
all inpatient days and the first 7 days after discharge.3
Investigational methodology
Case patients were identified by clinical epidemiology following
notification of GAS from clinical cultures in the electronic medical
Corresponding author: Shandra R. Day; Email: shandra.day@osumc.edu
Cite this article: Haden M, Liscynesky C, Colburn N, et al. Outbreak of postpartum
group a Streptococcus infections on a labor and delivery unit. Infect Control Hosp
Epidemiol 2024. doi: 10.1017/ice.2024.82
© The Author(s), 2024. Published by Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America. This is an Open Access article, distributed under the
terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original
article is properly cited.
Infection Control & Hospital Epidemiology (2024), 1–3
doi:10.1017/ice.2024.82
https://doi.org/10.1017/ice.2024.82 Published online by Cambridge University Press
record (EMR) prompting further investigation for postpartum
patients. The EMR was utilized to compile a list of HCWs who had
contact with case patients up to the date GAS infection was identified.
HCWs with case-patient contact were evaluated for GAS colonization
risk factors (recent illnesses, sick contacts, skin or soft tissue infections,
or open draining wounds). Occupational health collected screening
cultures from HCWs throat, vagina, peri-rectal area, and any open
skin wounds; vaginal and peri-rectal cultures were self-collected.
Household contacts from HCWs associated with multiple cases
underwent this same screening process. We defined a carrier as an
asymptomatic individual whose screening culture grew GAS. GAS
isolates from case patients and HCW carriers or their close contacts
were sent to the Streptococcus Laboratory at CDC for emm typing and
whole genome sequencing (WGS) (Supplemental Material). The
investigation was completed under the authority of the Quality
Department and is exempt from Institutional Review Board (IRB)
review.
Results
During a period of 119 days, a total of 6 patients developed
healthcare-acquired postpartum invasive GAS infection (Figure 1).
The case-patients all had a spontaneous vaginal delivery within the
preceding 7 days of symptoms onset. Six patients had endometritis
with GAS from vaginal cultures, 4 patients also had GAS
bacteremia and 1 patient developed toxic shock syndrome. All
patients survived and were discharged in good condition.
A total of 43 HCWs were screened following patients 1 and 2,
with a single HCW (HCW A) found to have GAS colonization
(Figure 1) which was successfully eradicated with chemoprophy-
laxis. Following case 2, new requirements for personal protective
equipment (PPE) were implemented including facemask, gown,
and gloves for all HCWs present during delivery.
Patient 3 occurred 96 days into the outbreak. An additional 9
HCWs were screened following this case, with another HCW
(HCW B) found to have GAS colonization (Figure 1), which was
successfully eradicated with chemoprophylaxis.
The outbreak persisted with 3 additional patients (patients 4, 5,
6) identified 119 days into the outbreak. At this time mass
screening of all HCWs involved in the labor and delivery unit was
instituted. A total of 681 HCWs completed screening and 12 were
found to be colonized with GAS. Three of the colonized HCWs
(HCW A, C, D) were identified with the outbreak strain including
HCW A, which prompted screening of their household contacts.
One household contact of HCW A was found to be colonized with
the outbreak strain (Figure 1). All received chemoprophylaxis and
were successfully eradicated.
Laboratory investigation
All clinical GAS isolates from the 6 invasive GAS case patients,
13 colonized HCWs, and 1 household contact were sent to the CDC
Streptococcus Laboratory for WGS. The outbreak strain was
identified as emm28 type, with all 6 isolates from case patients
belonging to this type. Across the different rounds of screening,
4 HCWs (HCW A screened positive twice) and 1 HCW household
contact were colonized with the outbreak GAS strain belonging
to emm28 type. All outbreak-associated isolates clustered on a
single branch of the phylogenetic tree and were highly related
with a pairwise difference of 0–2 Single Nucleotide
Polymorphisms (SNPs).
Figure 1. Outbreak epidemiologic curve and interventions.
2 Michael Haden et al.
https://doi.org/10.1017/ice.2024.82 Published online by Cambridge University Press
Discussion
The outbreak described here involved 6 patients who developed
healthcare-acquired invasive postpartum GAS infection acquired
from 4 asymptomatic HCWs who were colonized with the outbreak
strain. WGS of GAS isolates identified the outbreak strain as emm28
type, which is of particular significance as emm28 type GAS is a
commoncauseofinfectioninpregnantandpostpartumwomenand
is significantly associated with puerperal sepsis.7,8This is thought to be
due to a mobile genetic element of apparent group B Streptococcus
origin leading to increased tropism for vaginal tissue.9
Asymptomatic GAS colonization among adults is much less
than that of children. In one study among military trainees the
baseline colonization rate was 2.4%, though notably increased to
4.8% in part due to close quarters living conditions.10 During our
unit-wide screening the overall colonization rate among staff was
1.8% (12/681).
Our investigation initially identified a single HCW (HCW A)
with GAS colonization identified in oral, vaginal, and rectal
cultures. Despite being heavily colonized, they were decolonized
successfully per CDC guidelines including negative follow-up
testing.4The other HCWs colonized with the outbreak strain were
positive in oral cultures only and all had negative testing following
completion of chemoprophylaxis. Despite adhering to CDC
guidelines for GAS investigation the outbreak continued, spanning
119 days. It is notable that all HCWs colonized with the outbreak
strain worked the same shift; therefore, we speculate GAS spread
persisted due to two factors: among HCWs in the workplace due to
close contact in common areas and reacquisition of GAS
colonization in HCW A following successful chemoprophylaxis
due to a GAS positive household contact. Transmission to patients
was only halted following mass screening of all HCWs and
household contacts of HCW A, and chemoprophylaxis of those
colonized, in addition to continued infection prevention measures,
including PPE for all HCWs who entered patient rooms during
delivery and regular audits for PPE and hand hygiene compliance.
Mass screening was done over a short period of time, which
allowed for identification and interruption of the ongoing
transmission of the outbreak strain.
Our investigation highlights the importance of prompt
identification of potential postpartum GAS outbreaks, along with
strong lines of communication between patient care teams,
hospital leadership, infection control, and the microbiology lab
as well as coordination with local and state health departments.
Supplementary material. The supplementary material for this article can be
found at https://doi.org/10.1017/ice.2024.82.
Financial support. None reported.
Competing of interest. All authors report no conflicts of interest relevant to
this article.
Disclaimer. The findings and conclusions in this report are those of the authors
and do not necessarily represent the official position of the Centers for Disease
Control and Prevention.
References
1. O’Brien KL, Beall B, Barrett NL, et al. Epidemiology of invasive group a
Streptococcus disease in the United States, 1995–1999. Clin Infect Dis.
2002;35:268–276.
2. Nelson GE, Pondo T, Toews KA, et al. Epidemiology of invasive group a
streptococcal infections in the United States, 2005–2012. Clin Infect Dis.
2016;63:478–486.
3. The Prevention of Invasive Group A Streptococcal Infections Workshop
Participants. Prevention of Invasive Group A Streptococcal Disease among
Household Contacts of Case Patients and among Postpartum and
Postsurgical Patients: Recommendations from the Centers for Disease
Control and Prevention. Clin Infect Dis. 2002;35:950–959.
4. Anderson BL. Puerperal group a streptococcal infection: beyond semmel-
weis. Obstet Gynecol. 2014;122:874–882.
5. Bessen DE. Population biology of the human restricted pathogen,
Streptococcus pyogenes. Infect Genet Evol. 2009;9:581–593.
6. Rimawi BH, Soper DE, Eschenbach DA. Group a streptococcal infections in
obstetrics and gynecology. Clin Obstet Gynecol. 2012;55:864–874.
7. Chuang I, Van Beneden C, Beall B, Schuchat A. The active bacterial core
surveillance/emerging infections program network. Population-based
surveillance for postpartum invasive group a Streptococcus infections,
1995–2000. Clin Infect Dis. 2002;35:665–670.
8. Deutscher M, Lewis M, Zell ER, et al. Incidence and severity of invasive
Streptococcus pneumoniae, group a Streptococcus, and group b Streptococcus
infections among pregnant and postpartum women. Clin Infect Dis.
2011;53:114–123.
9. Jain I, Sarkar P, Danger JL, et al. A mobile genetic element promotes the
association between serotype M28 group a Streptococcus isolates and cases
of puerperal sepsis. J Infect Dis. 2019;220:882–891.
10. Putnam SD, Gray GC, Biedenbach DJ, Jones RN. Pharyngeal colonization
prevalence rates for Streptococcus pyogenes and Streptococcus pneumoniae
in a respiratory chemoprophylaxis intervention study using azithromycin.
Clin Microbiol Infect. 2000;6:2–8.
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