Streptococcus pyogenes in Neonates and Postpartum Women: First Report on Prevalence, Resistance, emm Typing, and Risk Factors in Khyber Pakhtunkhwa

Streptococcus pyogenes (Group A Streptococcus, GAS) is a major human pathogen responsible for a broad spectrum of infections, ranging from mild conditions such as pharyngitis and impetigo to severe invasive diseases, including necrotizing fasciitis and toxic shock syndrome (Cohen-Poradosu and Kasper 2007). While global child mortality has declined significantly, from 9.8 million in 2000 to 5.2 million in 2019, infectious diseases remain a major burden, particularly in low- and middle-income countries (LMICs) (Fleischmann-Struzek et al. 2018). Sepsis alone accounts for approximately 3 million neonatal and 1.2 million childhood cases annually, leading to 2.3 million deaths, with maternal sepsis being the third leading cause of maternal mortality worldwide (Say et al. 2014; Hariri et al. 2021).

Postpartum women and neonates are particularly susceptible to S. pyogenes infections due to immunological susceptibility and potential vertical spread during childbirth (Sherwood et al. 2022). Despite developments in maternal and neonatal care, GAS remains one of the key causes of puerperal sepsis and neonatal infections, contributing to substantial morbidity and mortality, particularly in resource-limited settings in low-income countries (Donders et al. 2021). Postpartum women have a 20-fold increased risk of having invasive S. pyogenes infections in comparison to non-pregnant women (Hassan et al. 2011), with invasive GAS (iGAS) occurring in 1 in 50 postpartum cases, carrying a mortality rate of around 3.5%. However, the incidence of neonatal GAS infections is not well documented in developing countries. Recent studies have reported an increasing burden of GAS infections in children in India and Pakistan (Haggar et al. 2012; Zafar et al. 2016).

The emergence of multidrug-resistant S. pyogenes strains has become a growing concern globally. Resistance to β-lactams, macrolides, lincosamides, and tetracyclines usually complicates treatments and underscores ongoing surveillance (Assafi et al. 2023; Cortés-Penfield and Ryder 2023; Shah et al. 2023). Molecular epidemiology studies highlight significant genetic diversity among S. pyogenes strains, with emm typing serving as a key tool for tracking transmission dynamics and evaluation of virulence potential in vulnerable populations, including children (Bonomo et al. 2025; Hall et al. 2025). The predominance of specific emm types varies geographically and demands region-specific surveillance to guide public health interventions (Weerasekara et al. 2024).

Several factors contribute to the risk of S. pyogenes infections in postpartum women and neonates, including prolonged labor, premature rupture of membranes in postpartum women, inadequate prenatal care, and neonatal resuscitation in neonates (Song et al. 2024; Hazelhorst et al. 2025). However, data on the prevalence, antimicrobial resistance, and molecular characteristics of S. pyogenes in postpartum women and neonates in Pakistan remain inadequate. Khyber Pakhtunkhwa (KP), a remote province of Pakistan having significant maternal and neonatal health challenges, remains largely unexplored in this regard because of limited healthcare infrastructure, low socioeconomic conditions, and inadequate disease control practices.

Given the increasing burden of GAS infections and the lack of systematic investigations in maternal and neonatal health settings in Pakistan, this study aims to determine the prevalence, antibiotic susceptibility, and emm typing of S. pyogenes isolates from postpartum women and neonates in tertiary care hospitals in KP. Findings from this study will provide crucial insights into GAS’s epidemiology and resistance patterns, aiding in evidence-based clinical management and infection control strategies.

The present study explored the prevalence, antibiotic susceptibility, clinical manifestations, and risk factors associated with S. pyogenes infections in postpartum women and neonates in tertiary care hospitals in Khyber Pakhtunkhwa, Pakistan. The overall prevalence of S. pyogenes was found to be 14.3%, with postpartum women showing a slightly higher prevalence (16.7%) than neonates (11.9%). These findings are in accordance with previous studies reporting prevalence rates of S. pyogenes ranging from 2–18% in similar healthcare settings (Leonard et al. 2019; Sherwood et al. 2022), including rural India (12–15%) (Haggar et al. 2012) and Karachi, Pakistan (11.17%) (Zafar et al. 2022), suggesting a consistent burden in low-resource regions.

Our findings confirmed that S. pyogenes remains susceptible to β-lactam antibiotics, with penicillin showing ≥ 95% and ampicillin ≥ 91% susceptibility rates. However, the detection of penicillin-resistant isolates, although infrequent, is a growing concern. These findings agree with reports from neighboring India, where Berwal et al. (2019) reported 8% penicillin resistance. Similarly, Ahmad et al. (2024) and Zafar et al. (2016) documented increasing minimum inhibitory concentrations (MICs) in Pakistan, raising early warning signals despite apparent laboratory susceptibility. Akram et al. (2021) also reported a 13.1% resistance rate to amoxicillin. These findings suggest that while pbp2x mutations remain rare in KP (potentially due to restrictive penicillin use in obstetric practice). Regional surveillance for this emerging resistance is imperative to maintain penicillin’s clinical utility as first-line therapy. Nonetheless, as reported by Musser et al. (2020) from Europe, the spread of pbp2x-associated reduced β-lactam susceptibility across different regions highlights the critical need for ongoing molecular surveillance in our area.

In addition to β-lactams, our study identified moderate resistance levels to cephalosporins – 12.0% among postpartum women and 13.1% among neonates. While not alarmingly high, these figures urge caution when selecting empirical therapies, particularly for vulnerable populations. Our results align with regional data, including reports of up to 49.3% cefixime resistance in Pakistan (Rizwan et al. 2016), cefixime (17.6%) and ceftriaxone (8.1%) resistance in Iran (Khademi et al. 2021). In the US, Vannice et al. (2020) reported GAS clinical isolates with elevated ampicillin, amoxicillin, and cefotaxime MICs conferred by a pbp2x mutation. A resistance rate of 1.5 % to penicillin has been reported from China (Li et al. 2016). Together, these patterns emphasize the urgent need for robust antimicrobial stewardship programs, especially in maternal and neonatal healthcare settings, to safeguard the efficacy of these critical antibiotics in maternal-neonatal care.

In the present study, macrolide resistance among S. pyogenes isolates to erythromycin was observed in 23.5% of postpartum women and 29% of neonates, and azithromycin resistance rates were 20% and 25%, respectively. Although concerning, these rates are slightly lower than the 30.5% erythromycin resistance previously reported from Mardan, Pakistan (Akram et al. 2021). Our findings are broadly comparable to resistance levels documented in India (18.1%; Khandekar and Dangre-Mudey 2019) and somewhat higher than those reported in Turkey (9.4%; Ünübol et al. 2025) but lower than the 31.8% resistance described in Ethiopia (Gebre et al. 2024). Macrolide resistance in S. pyogenes primarily arises through the macrolide-lincosamide-streptogramin B resistance mechanism, typically mediated by erm genes (leading to methylation of the 23S rRNA target site) or mef genes (resulting in active efflux of the drug) (Leclercq and Courvalin 1991). These genetic mechanisms confer resistance to macrolides and may impact susceptibility to lincosamides and streptogramins, complicating therapeutic options. Importantly, the widespread and empirical misuse of macrolides, particularly azithromycin, for treating respiratory infections and pharyngitis in both adults and children in Pakistan (Bilal et al. 2021). This likely exerts significant selective pressure favoring the emergence and spread of resistant strains. Based on the studies of resistance rates using the ermB and mefA genes, resistance rates have been reported in other regions, such as Brazil (15.4%; Arêas et al. 2014), Spain (8.7%; Villalón et al. 2023), and the US (up to 19%; Li et al. 2023), showing the global relevance of this trend.

Our findings of moderate clindamycin resistance (15.6% in postpartum women and 21.7% in neonates) further pose therapeutic challenges, as clindamycin is often considered an alternative agent for macrolide-resistant infections. Overall, these results emphasize the urgent need for antimicrobial stewardship efforts focused on rational macrolide use and ongoing surveillance of resistance patterns to preserve the efficacy of these critical agents.

We observed high resistance rates to fluoroquinolones (ciprofloxacin: 38.7% in postpartum women, 43.5% in neonates) and tetracycline (32.1% in postpartum women, 37.5% in neonates). These findings align with the increasing resistance trends reported across South Asia, where tetracycline resistance has reached 51% and levofloxacin resistance 8.9% (Khandekar and Dangre-Mudey 2019), and in Europe, with Greece reporting 40.8% resistance to tetracycline, 18.8% to clindamycin, and 2% to levofloxacin (Meletis et al. 2023).

All isolates in our study were fully susceptible to carbapenems (meropenem) and glycopeptides (vancomycin), supporting their continued reliability for managing severe or multidrug-resistant S. pyogenes infections. Our findings are in agreement with Camara et al. (2013), who also reported 100% susceptibility to vancomycin, while Gashaw et al. (2025) from Ethiopia noted slightly lower sensitivity (93.87%). Additionally, Sakata et al. (2013) demonstrated potent in vitro activity of carbapenems against S. pyogenes, with minimal inhibitory concentrations of 0.008 μg/ml for meropenem, highlighting their superior antimicrobial profiles. The regional differences in susceptibility could partly be attributed to antibiotic usage patterns; in Pakistan, vancomycin is infrequently used in pediatric practice, and carbapenems are typically reserved for only the most severe infections, potentially preserving their efficacy.

To our knowledge, this is the first study in KP to characterize emm type distribution patterns in neonates and postpartum women. Among the 30 emm types identified in the study, predominant types (emm44, emm77, emm12) differ from Karachi, Pakistan (emm68/104/1/39; Khan et al. 2020) and Chinese (emm1/12; Yu et al. 2021) strains, suggesting geographic variability. These geographical differences in emm types could be due to variations in host immunity, climate, healthcare infrastructure and practices, or regional antibiotic usage patterns (Xiang et al. 2023). The distribution of emm types among both neonates and postpartum women, particularly the overlapping prevalence of emm44 (48% in neonates, 52% in mothers) followed by emm77, emm 12, emm1, emm3, emm28, and emm27 with varying frequencies, suggests the possibility of vertical transmission during delivery, a route supported by previous studies linking with invasive neonatal infections and toxic shock-like syndrome (Bonomo et al. 2025). The vertical transmission pattern was not directly evaluated in the present study. Future molecular analyses comparing mother-infant transmission could explain transmission dynamics. In this study, emm types common in both groups indicate a highly virulent feature of these types affecting any age group as reported previously (Gergova et al. 2024). Notably, emm12 and reported in the study are linked to pharyngitis disease in both pediatric and adult populations including women as reported previously (Koutouzi et al. 2015). emm12 and emm1 are found to be commonly associated with both pharyngitis and severe infections in the pediatric population in Spain and China (Yu et al. 2021; Ramírez de Arellano et al. 2024). The presence of emm3 and emm28 in the present study, which are recognized for their association with streptococcal toxic shock syndrome and necrotizing fasciitis, suggests a high pathogenic potential in the regional strains (Imöhl et al. 2010). The immature pediatric immune system and the epidemiological differences in the emm-types detected between the age groups may explain the differences (Zachariadou et al. 2014).

The predominance of emm44, emm77, and emm12 in our study suggests potential links to pathogenicity and transmission dynamics in our region. Notably, emm44 and emm77 isolates exhibited higher resistance to macrolides, tetracyclines, and ciprofloxacin than other emm types. This aligns with global reports associating specific emm types with resistance genes (ermB, mefA) (Meletis et al. 2023; Ramírez de Arellano et al. 2024). Co-resistance to tetracyclines and macrolides in S. pyogenes often results from horizontally transferred genetic elements such as phages, transposons, and plasmids encoding resistance genes (tetM, tetO, tetK, tetL) (Villalón et al. 2023). Previous studies have shown that tetracycline resistance is associated with the ermB and tetM genes (Villalón et al. 2023). Fluoroquinolone resistance has been reported to increase in S. pyogenes in different countries post-2020, primarily due to mutations in the parC and gyrA topoisomerase genes (Gergova et al. 2024). Neonatal emm77 isolates showed higher fluoroquinolone resistance (43.5%) than postpartum women (38.7%), possibly reflecting NICU antibiotic use (Song et al. 2024).

The clinical presentations of S. pyogenes infections observed in this cohort align with the patterns reported in global literature, reflecting local healthcare infrastructure. Fever, sepsis, respiratory distress, and bacteremia (confirmed by positive blood cultures) were the important features among both postpartum women and neonates, which are consistent with findings from Sherwood et al. (2022) and Sokou et al. (2023), who emphasized the rapid progression and severity of invasive infections. Among the neonates, lethargy and hypoglycemia were prominent clinical signs, and this finding is consistent with Sokou et al. (2023), who reported lethargy, respiratory distress, and poor feeding as early clinical indicators of neonatal GAS infection. The hypoglycemia observed likely reflects systemic inflammatory disturbances, particularly IL-6-mediated gluconeogenesis suppression, as Wynn and Wong described (2010).

Our study identified significant predictors of GAS infection in KP province. Among postpartum women, prolonged labor (> 18 hours; p = 0.030), premature rupture of membranes (p = 0.039), poor socioeconomic status (p = 0.027), home deliveries without skilled attendants (34.4% of cases), and limited prenatal care (< 3 visits; p = 0.036) were strongly associated with infection. These findings align with global studies highlighting social determinants and delayed obstetric care as major contributors to puerperal sepsis (Say et al. 2014; Harris et al. 2023). Notably, while Cooper et al. (2023) reported healthcare-associated outbreaks in high-resource settings, our infections were predominantly community-acquired, reflecting systemic gaps in KP’s maternal healthcare infrastructure. In neonates, preterm birth (< 37 weeks; p = 0.013) and resuscitation needs (p = 0.028) emerged as critical risk factors, consistent with the heightened vulnerability of preterm infants documented by Sokou et al. (2023) and Birrie et al. (2022). The frequent requirement for resuscitation in our cohort almost reflects perinatal care deficiencies, which are common in low-resource areas like KP.

Blood culture positivity (bacteremia) for S. pyogenes showed borderline significance (p = 0.054), emphasizing its diagnostic utility for invasive GAS infections (Sherwood et al. 2022). Elevated CRP, leukocytosis, thrombocytopenia, and anemia, but not statistically significant, and supported clinical suspicion of invasive bacterial disease. Early empirical antibiotic use may have tempered these laboratory responses.

Clinically, postpartum women presented with fever (> 38°C; 75%), sepsis (50%), and bacteremia (58.3%), while neonates exhibited respiratory distress (55.6%), lethargy (50%), and bacteremia (66.7%). These manifestations correlated strongly with the pathogenic emm types identified (emm1, emm3, emm28), which are historically linked to severe invasive disease (Creti et al. 2007)

The present study, conducted for the very first time in KP, showed a high burden of serious S. pyogenes infections affecting postpartum mothers and newborns, demonstrating the necessity to improve infection prevention strategies in perinatal healthcare units in low-resource settings. Continuous antibiotic surveillance and antibiotic stewardship operations are required to observe resistance patterns and modify treatment regimens. β-Lactams act as the primary first-line empirical treatment, yet medical staff should cautiously choose antibiotics due to macrolide resistance. Preventing S. pyogenes infections among high-risk populations requires strategic measures that combine enhanced prenatal healthcare with early diagnosis systems and infection prevention protocols inside hospitals. Large-scale surveillance, including community-based sampling in other cities of KP, is recommended for a more precise assessment of the disease burden. Future studies incorporating genomic analysis are critical to identifying the specific resistance causes and possible transmission dynamics.