GBS Screening Test at Chughtai Lab

GBS (Group-B Streptococcus) Screening at Chughtai Lab

Group-B Streptococcus (GBS), scientifically classified as Streptococcus agalactiae, is a Gram-positive, beta-hemolytic bacterium that commonly colonizes the human gastrointestinal and genitourinary tracts. While GBS colonization is typically asymptomatic and harmless in healthy adults, it poses a significant clinical risk during pregnancy. If a pregnant woman is colonized with GBS, the bacterium can be vertically transmitted to the newborn during vaginal delivery. This transmission can lead to severe, life-threatening neonatal infections, including neonatal sepsis, pneumonia, and meningitis. To mitigate this risk, clinical guidelines worldwide recommend routine GBS screening for all pregnant women. GBS screening at Chughtai Lab is a highly reliable, evidence-based diagnostic service designed to identify maternal colonization, enabling timely intrapartum antibiotic prophylaxis (IAP) to protect the newborn.

Chughtai Lab, a premier diagnostic network in Pakistan, utilizes state-of-the-art microbiological techniques to perform GBS screening. The test is performed using a rectovaginal culture, which is the gold standard method for detecting GBS colonization. By analyzing samples collected from both the lower vagina and the rectum, the laboratory can highly accurately determine the presence of the bacterium. This screening is typically performed during the late third trimester of pregnancy, specifically between 36 and 37 weeks of gestation. Identifying GBS-positive mothers before labor is crucial, as it allows healthcare providers to administer intravenous antibiotics during delivery, reducing the risk of early-onset neonatal GBS disease by over 80 percent.

The clinical importance of GBS screening cannot be overstated. Neonatal GBS infection is categorized into early-onset disease (occurring within the first seven days of life) and late-onset disease (occurring from seven days to three months of life). Early-onset GBS disease is directly linked to intrapartum transmission from a colonized mother. Symptoms in newborns can progress rapidly from mild respiratory distress to severe septic shock. By choosing Chughtai Lab for GBS screening, expectant mothers receive accurate, timely, and clinically actionable results, ensuring a safer delivery process and safeguarding the health of their newborns.

Clinical Procedure: What to Expect

Patient Preparation

Proper patient preparation is essential to ensure the accuracy of the GBS screening culture and to prevent false-negative or false-positive results. Patients are advised to adhere to the following guidelines prior to sample collection:

• Avoid Vaginal Medications and Products: Do not use any vaginal creams, ointments, suppositories, douching products, or feminine hygiene sprays for at least 24 to 48 hours before the test, as these substances can inhibit bacterial growth in the culture.
• Avoid Vaginal Lubricants and Contraceptive Gels: Refrain from using lubricants or contraceptive gels prior to the procedure, as they may contain antimicrobial agents that interfere with the viability of the GBS bacteria.
• Disclose Recent Antibiotic Use: Inform your healthcare provider and the laboratory staff if you have taken any oral or systemic antibiotics within the last two weeks. Antibiotics can temporarily suppress GBS levels, leading to a false-negative culture result.
• No Fasting Required: There are no dietary restrictions or fasting requirements for this test. You may eat and drink normally before your appointment.
• Maintain Personal Hygiene: Clean the external genital area with water only. Avoid using harsh soaps or antiseptic washes immediately before the sample collection.

During the Procedure

The GBS screening procedure is simple, quick, and minimally invasive. It is performed by a trained healthcare professional or can be self-collected under specific clinical guidance. The process involves the following steps:

• Patient Positioning: The patient is asked to lie on an examination table, typically in a comfortable supine position with knees bent, similar to a routine prenatal examination.
• Vaginal Swab Collection: The healthcare provider uses a sterile, non-toxic dacron or rayon swab. The swab is gently inserted into the lower vagina (vaginal introitus) without using a speculum. The swab is rotated to collect adequate mucosal secretions.
• Rectal Swab Collection: The same swab (or a second sterile swab) is then gently inserted through the anal sphincter into the rectum (approximately 1 to 2 centimeters) and rotated to collect fecal material, which is a primary reservoir for GBS.
• Sample Preservation: The swab is immediately placed into a specialized transport medium (such as Amies or Stuart transport medium) to maintain bacterial viability during transit to the microbiology laboratory.
• Duration and Sensation: The entire collection process takes less than one minute. Patients may feel a mild pressure or tickling sensation, but the procedure is completely painless and safe for both the mother and the fetus.

When is a GBS Screening Performed?

Routine Prenatal Screening at 36-37 Weeks

The primary clinical indication for GBS screening is routine prenatal care for all pregnant women between 36 0/7 and 37 6/7 weeks of gestation. This specific window is selected because GBS colonization can be transient, meaning the bacterium may colonize the genitourinary tract temporarily and then disappear, or vice versa. Testing during this late stage of pregnancy provides the most accurate reflection of the mother’s colonization status at the estimated time of delivery, allowing for appropriate planning of intrapartum antibiotic prophylaxis.

History of Previous GBS-Infected Infant

Physicians will closely monitor pregnant women who have a history of delivering a previous infant diagnosed with invasive GBS disease. In these cases, the risk of transmission in subsequent pregnancies is significantly elevated. While clinical guidelines often recommend that these women receive automatic intrapartum antibiotic prophylaxis without the absolute need for screening, performing a GBS culture helps clinicians understand the current colonization status and guide comprehensive neonatal management plans.

GBS Bacteriuria During the Current Pregnancy

If a pregnant woman is diagnosed with GBS bacteriuria (the presence of Group-B Streptococcus in the urine) at any point during her current pregnancy, it indicates a high level of maternal colonization. While these patients require immediate treatment for urinary tract infection (UTI) during pregnancy, they also automatically qualify for intrapartum antibiotic prophylaxis during labor. GBS screening may still be performed to monitor colonization density and assess antibiotic susceptibility profiles.

Preterm Labor or Premature Rupture of Membranes (PROM)

In cases of threatened preterm labor or premature rupture of membranes (PROM) occurring before 37 weeks of gestation, the risk of ascending GBS infection increases dramatically. If the mother’s GBS status is unknown, clinicians will perform an immediate GBS screening culture. This helps determine whether to initiate prophylactic antibiotics to protect the premature infant, who is highly vulnerable to severe GBS-related complications due to an immature immune system.

Maternal Risk Factors During Labor

When a pregnant woman presents in labor with an unknown GBS status, physicians evaluate specific clinical risk factors to determine the necessity of empirical antibiotic prophylaxis. These risk factors include intrapartum fever (temperature of 38 degrees Celsius or higher), rupture of membranes lasting 18 hours or longer, or labor onset before 37 weeks. Performing a rapid GBS screening or culture upon admission can assist in confirming the diagnosis and optimizing antibiotic stewardship.

What Does a GBS Screening Detect?

GBS screening at Chughtai Lab is designed to detect and evaluate several microbiological and clinical parameters to guide obstetric care. The analysis includes:

• Presence of Streptococcus agalactiae: The primary objective is to detect the viable growth of Group-B Streptococcus from the rectovaginal sample.
• Absence of GBS Colonization: Confirming a negative status, indicating that the patient is not a carrier of GBS at the time of testing.
• Gram-Positive Cocci in Chains: Microscopic identification of the characteristic morphology of streptococcal bacteria.
• Beta-Hemolytic Colony Growth: Observation of clear zones of hemolysis around bacterial colonies on sheep blood agar plates.
• Non-Hemolytic GBS Variants: Identification of rare, non-hemolytic strains of GBS that still pose a clinical risk to newborns.
• Catalase-Negative Status: Biochemical differentiation of GBS from catalase-positive organisms like Staphylococcus.
• Positive CAMP Test Reaction: Confirmation of GBS based on its synergistic hemolytic reaction with Staphylococcus aureus.
• Positive Latex Agglutination: Definitive serological identification of the Lancefield Group B antigen.
• Penicillin Susceptibility Profile: Testing to confirm that the isolated GBS strain is sensitive to penicillin, the first-line treatment.
• Ampicillin Susceptibility: Evaluation of sensitivity to ampicillin as an alternative first-line intrapartum agent.
• Erythromycin Resistance Patterns: Critical testing for penicillin-allergic patients to determine alternative therapeutic options.
• Clindamycin Resistance Patterns: Testing for clindamycin susceptibility, including the detection of inducible clindamycin resistance (D-zone test).
• Presence of Normal Vaginal Flora: Assessment of healthy vaginal bacteria, such as Lactobacillus species, which maintain a balanced environment.
• Overgrowth of Gardnerella vaginalis: Detection of co-existing bacterial vaginosis, which may require separate clinical attention.
• Presence of Candida Species: Identification of concurrent yeast colonization or infection in the vaginal tract.
• Co-colonization with Pathogenic Bacteria: Detection of other potential pathogens, such as Staphylococcus aureus or Enterobacteriaceae.
• Presence of Fecal Flora Contaminants: Monitoring for Escherichia coli or other enteric bacteria to ensure accurate culture differentiation.
• Semi-Quantitative Assessment: Evaluation of the density of GBS colonization (heavy versus light growth).
• Specimen Adequacy: Verification that the swab contains sufficient cellular and mucous material for a valid culture.
• Absence of Inhibitory Substances: Ensuring that no external contaminants or topical products have compromised the bacterial culture.
• Differential Diagnosis of Other Streptococci: Distinguishing GBS from Group A, C, or G Streptococci.
• Alternative Antibiotic Recommendations: Providing guidance on alternative antibiotics in cases of multi-drug resistant GBS strains.

Turnaround Time and Report Access at Chughtai Lab

Chughtai Lab is committed to providing rapid, highly accurate diagnostic reports. For GBS screening, the standard turnaround time is typically 24 to 48 hours. This timeframe is necessary because the culture process requires incubating the rectovaginal swab in selective enrichment broth and agar plates to allow for bacterial colony growth, followed by biochemical and serological confirmation of Streptococcus agalactiae.

Patients and referring physicians can easily access reports through multiple convenient digital channels. Once the results are finalized and verified by a consultant pathologist, an SMS notification is sent to the patient’s registered mobile number. Reports can be downloaded directly from the official Chughtai Lab website or via the user-friendly Chughtai Lab mobile application. Additionally, printed copies of the reports can be collected from any of the numerous Chughtai Lab collection centers located nationwide, or delivered directly to the patient’s home through their dedicated delivery service.

GBS Screening Findings Overview

Structure / Parameter Evaluated	Normal Findings	Possible Abnormal Findings
Streptococcus agalactiae Culture	No growth of Group B Streptococcus	Growth of Streptococcus agalactiae (Group B Streptococcus) detected
Gram Stain Morphology	Dominant Gram-positive bacilli (Lactobacillus species consistent with normal flora)	Gram-positive cocci arranged in pairs and chains, indicating GBS colonization
Hemolysis on Blood Agar	No beta-hemolytic colonies isolated	Presence of beta-hemolytic colonies, characteristic of Streptococcus agalactiae
CAMP Test Reaction	Negative reaction	Positive reaction (enhanced zone of hemolysis), confirming GBS presence
Latex Agglutination	Negative for Group B Lancefield antigen	Positive for Group B Lancefield antigen, providing definitive identification
Antibiotic Susceptibility Testing	Not applicable (no bacterial growth isolated)	Susceptibility or resistance to Penicillin, Ampicillin, Erythromycin, and Clindamycin
Co-existing Pathogens	No significant pathogenic organisms isolated	Isolation of Candida species, Gardnerella vaginalis, or other urogenital pathogens

Note: Diagnostic findings should always be interpreted by a qualified healthcare professional together with the patient’s symptoms, medical history, physical examination, laboratory investigations, previous imaging studies, and other relevant clinical information. Additional investigations or specialist consultation may be recommended depending on the findings.

Why Choose Chughtai Lab for GBS Screening?

• Experienced Pathologists and Microbiologists: Your samples are processed and analyzed under the supervision of highly qualified consultant pathologists and microbiologists.
• Advanced Microbiology Department: Chughtai Lab utilizes state-of-the-art culture media, automated identification systems, and strict quality control protocols for accurate bacterial detection.
• ISO 15189 Certified Standards: The laboratory adheres to international quality management standards, ensuring reliable and reproducible diagnostic results.
• Convenient Home Sample Collection: Pregnant patients can schedule a professional phlebotomist or nurse to collect the rectovaginal swab in the comfort and privacy of their homes.
• Nationwide Network: With hundreds of collection centers across Pakistan, Chughtai Lab offers easily accessible diagnostic services close to your home.
• Secure Online Report Access: Instantly view, download, and share your diagnostic reports via the Chughtai Lab website or mobile app.
• Strict Specimen Handling Protocols: Samples are transported in specialized temperature-controlled environments to maintain bacterial viability and prevent contamination.
• Patient-Focused Care: Chughtai Lab prioritizes patient comfort, confidentiality, and professional support throughout the diagnostic journey.