A team at the Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, has reported a significant rise in infections caused by a lesser-known bacterium Bordetella holmesii that mimics whooping cough in north India.

About Bordetella holmesii
Bordetella holmesii is a Gram-negative bacterium that can cause pertussis-like respiratory symptoms (whooping cough) and serious invasive infections like bacteremia (bloodstream infection), primarily in asplenic or immunocompromised individuals. It was first recognized as a distinct species in 1995. 

Key Characteristics and Infections

• Gram-negative coccobacillus: Describes the shape and cell wall type of the bacterium.
• Asaccharolytic and nonmotile: It does not use sugar for energy and is not mobile.
• Produces a brown pigment: A key distinguishing feature in laboratory cultures.
• Invasive infections: In susceptible individuals (especially those with sickle cell disease or without a functional spleen), it can cause severe illnesses beyond respiratory issues, including:
  • Bacteremia (most common in asplenic patients)
  • Pneumonia
  • Meningitis
  • Endocarditis (heart valve infection)
  • Suppurative arthritis (joint infection)
  • Cellulitis (skin infection)
  • Pyelonephritis (kidney infection)

• Respiratory illness: It can cause symptoms similar to Bordetella pertussis (whooping cough), including a severe, paroxysmal cough, a "whoop" sound when breathing in, and post-tussive vomiting. These symptoms are often milder in adults and teens. 

Diagnosis and Treatment Considerations

• Misdiagnosis is common: Routine diagnostic tests for B. pertussis often cannot differentiate it from B. holmesii because they are not species-specific (e.g., PCR assays targeting the IS481 insertion sequence). This has led to an underestimation of its prevalence.
• Fastidious growth: The bacterium is slow-growing in lab cultures, requiring specific conditions and time (up to 48 hours or more to visualize colonies), which can delay identification.
• Treatment: There are no universally accepted treatment guidelines. B. holmesii has lower susceptibility to macrolides and third-generation cephalosporins (common empirical antibiotics for B. pertussis and other infections). Fluoroquinolones and carbapenems may be more effective options. Clinical recovery is often favorable with appropriate treatment.
• Vaccination: The existing pertussis vaccine (DTaP/Tdap) does not offer cross-protection against B. holmesii. 

Bordetella holmesii is an emerging and under-recognized pathogen, and awareness of its existence and appropriate diagnostic methods are important for accurate epidemiological surveillance and clinical management. 

What is Whooping cough?
Whooping cough, also known as pertussis or the "100-day cough," is a highly contagious respiratory tract infection caused by the bacterium Bordetella pertussis. The illness is known for characteristic severe, uncontrollable coughing fits that can make breathing difficult and often end with a high-pitched "whooping" sound when the person gasps for air. 

Symptoms
Symptoms typically appear 5 to 10 days after exposure and progress in stages: 

• Initial Stage (1-2 weeks): Symptoms resemble a common cold, including a runny or stuffy nose, sneezing, mild fever, and a mild, occasional cough. During this stage, the infected person is most contagious.
• Severe Stage (1-6 weeks, sometimes longer): The cough worsens into violent, rapid coughing fits (paroxysms) due to thick mucus buildup in the airways. These fits can cause the face to turn red or blue, vomiting, and extreme exhaustion. Infants may not cough or "whoop" at all; instead, they may gag, struggle to breathe, or experience life-threatening pauses in breathing called apnea.
• Recovery Stage (weeks to months): Coughing fits gradually become less frequent and severe, but a lingering cough can continue for a long time. 

Causes and Transmission
The bacteria are spread easily from person to person through tiny droplets in the air when an infected person coughs, sneezes, or talks. Humans are the only known host for the bacteria. 

Risk and Complications
Anyone can get whooping cough, but it is most dangerous for infants, especially those younger than 6 months who are too young to be fully vaccinated. Complications in infants can be severe and include pneumonia, slowed or stopped breathing, seizures, and in rare cases, brain damage or death. In adults and older children, complications tend to be less severe but can include bruised or cracked ribs, broken blood vessels in the eyes, or hernias from intense coughing. 

Treatment and Prevention

• Treatment: Antibiotics are used to treat the infection. They are most effective when started early in the illness to reduce its severity and can shorten the contagious period.
• Prevention: Vaccination is the most effective preventive measure. Vaccines (DTaP for children, Tdap boosters for adolescents and adults) are recommended for all age groups to provide protection, although immunity can fade over time. Pregnant women are advised to get vaccinated during each pregnancy to pass some immunity to their newborns. 

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