The clinical story began with symptoms that might easily have been mistaken for a routine ear problem. The young woman developed a headache, pain in the affected ear, and visible inflammation of the skin over the site where her cochlear implant had been placed. For most patients, such complaints would prompt a search for common bacterial culprits, typically organisms that colonize the skin or the external ear canal. But this patient’s medical history and her home environment pointed her care team toward a far less expected diagnosis, one that would only emerge after an extensive diagnostic work-up.

CHARGE syndrome is a rare genetic condition whose name is an acronym summarizing its hallmark features: coloboma of the eye, heart defects, choanal atresia, retardation of growth and development, genitourinary abnormalities, and ear abnormalities. The ear anomalies associated with the syndrome are among its most consistent features, and they frequently produce severe sensorineural hearing loss. Cochlear implants, which bypass damaged inner ear structures by converting sound into electrical signals delivered directly to the auditory nerve, are therefore a common and often transformative intervention for patients with CHARGE syndrome. Yet the same anatomical complexity that makes implantation necessary also makes these patients surgically challenging, with altered temporal bone anatomy and an increased likelihood of perioperative and postoperative complications.

When the teenager arrived with headache, ear pain and cellulitis over her implant site, her physicians pursued an aggressive and systematic evaluation. Imaging of the temporal bone with computed tomography using intravenous contrast allowed the team to assess the bony structures surrounding the implant and to look for evidence of bone involvement. Blood cultures were obtained to determine whether bacteria had entered the bloodstream, and cultures of the wound itself were sent to identify the organism responsible for the local infection. The results were striking: cultures grew Pasteurella multocida, and the imaging findings confirmed osteomyelitis, an infection of the bone adjacent to the implant. Blood cultures demonstrated a transient bacteremia, indicating that the organism had at least briefly circulated beyond the site of the wound.

Pasteurella multocida is a gram-negative coccobacillus, a small, rounded rod-shaped bacterium that occupies a distinctive ecological niche. It lives as part of the normal oral flora of many domestic animals, with cats being the most common carriers, and it is notorious among clinicians for producing rapidly developing cellulitis after bites and scratches. In typical zoonotic infections, the bacterium is introduced directly into the skin through a break in the epidermis, causing redness, swelling and pain within hours to days of the injury. What makes this case exceptional is the presumed route of inoculation and the destination of the infection: rather than a simple skin infection, the organism apparently colonized the surgical site of an implanted medical device and then invaded the underlying bone, a pattern of disease that has rarely been described in association with cochlear implants.

The exposure history proved to be the key that unlocked the diagnosis. The patient’s family had recently welcomed a new kitten into the home, and the teenager had sustained numerous excoriations, superficial scratches that break the skin, from the animal’s playful claws. In a patient with a permanently implanted device beneath the skin of the scalp and mastoid region, even minor scratches over the implant site can provide a pathway for oral bacteria from a pet to reach the device and the surrounding tissue. The authors of the report emphasize that a thorough exposure history, including questions about animal contact, should be part of the standard evaluation of any pediatric patient presenting with headache, ear pain and cellulitis, particularly when complicating factors such as a cochlear implant are present, so that zoonotic organisms are included in the differential diagnosis from the outset.

Management of the infection required both surgical and medical strategies, reflecting the seriousness of a device-related bone infection. The cochlear implant itself had to be removed, a difficult decision in any patient for whom the device represents their primary connection to the hearing world, but one that is often unavoidable when infection involves the implanted hardware. Biofilm formation, in which bacteria adhere to artificial surfaces and encase themselves in a protective matrix, makes device infections nearly impossible to eradicate with antibiotics alone. In addition to the explantation, the patient received four weeks of antibiotic therapy targeted at Pasteurella multocida, a duration consistent with the treatment of osteomyelitis, where prolonged therapy is needed to eliminate bacteria residing within bone tissue.

The clinical course was further complicated by the development of facial nerve palsy, a weakness of the facial muscles caused by dysfunction of the facial nerve, which runs through the temporal bone in close proximity to the structures involved in cochlear implantation. Inflammation and infection within this confined bony space can compress or irritate the nerve, producing facial drooping and difficulty closing the eye on the affected side. The patient was treated with corticosteroids, the standard approach to reduce inflammation around the nerve, and the report documents this complication as part of the cascade of events set in motion by the infection. The episode underscores how infections of the temporal bone can threaten not only hearing but also the cranial nerves that control facial movement.

Beyond its microbiological novelty, the case carries a broader message about the care of medically complex patients. The authors highlight the importance of a multidisciplinary team in managing patients with intricate medical and surgical histories. In this single admission, expertise was required from otolaryngology, which managed the implant and the temporal bone; from pediatric infectious diseases, which selected and monitored the antibiotic regimen; and from pathology and laboratory medicine, which identified the organism through culture. The patient herself consented to the publication of her case, having been an adult at the time of her care, and the authors express their appreciation for her willingness to share her experience so that other clinicians might recognize similar presentations more quickly.

For the wider community of cochlear implant recipients and their families, the report offers practical lessons without cause for alarm. Device infections remain uncommon, and Pasteurella multocida is an unusual cause even among those that do occur. But the case illustrates a simple preventive principle: minor wounds over an implant site deserve attention, and households with implanted medical devices should be mindful of scratches from pets, particularly cats. For clinicians, the message is equally direct. When a patient with an implanted device presents with unexplained cellulitis, headache and ear pain, asking about animal exposure may reveal the diagnosis that routine thinking would miss, and early recognition of zoonotic pathogens can spare patients the prolonged and invasive course that this teenager endured.

Subject of Research: A case report of Pasteurella multocida cochlear implant infection in a teenager with CHARGE syndrome

Article Title: Cochlear implant infection in a teenager with CHARGE syndrome: a case report

Article References: Pereira, N. M., Tarun, S., Johnson, C. L., Neu, N., Green, D. A., Wang, R., & Golub, J. S. (2026). Cochlear implant infection in a teenager with CHARGE syndrome: a case report. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07624-6

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07624-6

Keywords: Pasteurella multocida, CHARGE syndrome, cochlear implant, zoonotic infection, osteomyelitis, bacteremia, facial nerve palsy, pediatric infectious disease, cat scratch, multidisciplinary care, antibiotic therapy, case report

The team’s methodology combined classical bacteriology with molecular confirmation, a dual approach that proved essential for accuracy. Of the 400 nasal swabs, 49 samples yielded colonies consistent with P. multocida on culture and biochemical screening, suggesting a presumptive prevalence of 12.25 percent. However, when the researchers applied polymerase chain reaction assays targeting species-specific genes, only 29 of those isolates were molecularly confirmed, yielding a PCR-confirmed prevalence of 7.25 percent. The discrepancy between the two methods underscores a persistent challenge in field microbiology: phenotypic identification can overestimate true prevalence because closely related commensal bacteria may mimic the colony morphology and biochemical profile of P. multocida, while PCR specificity comes at the cost of occasional sensitivity losses in samples with low bacterial DNA loads or inhibitory compounds.

Perhaps the most consequential molecular finding was capsular typing. Every PCR-positive isolate belonged to capsular type B, the serogroup associated with serotype B:2, one of the two strains—alongside E:2—responsible for devastating hemorrhagic septicemia outbreaks across Asia. Hemorrhagic septicemia is among the most lethal bacterial diseases of cattle and buffaloes in the region, producing fever, edema, respiratory distress, and rapid death. Because recovered and subclinically infected animals can harbor the organism in the lymphatic tissues of the upper respiratory tract and intermittently shed it in nasal secretions, the identification of type B organisms in nasal carriers carries significant epidemiological weight. Carrier animals act as a reservoir from which the bacterium can spread to susceptible herdmates and even to other indigenous species through aerosols, secretions, and direct contact.

The geographic distribution of positive samples varied considerably across the study sites, hinting at the influence of local husbandry and hygiene practices. Zakiganj recorded the highest detection rates, with 19.64 percent culture positivity and 14.29 percent molecular confirmation, followed closely by Fenchuganj. At the other extreme, no PCR-positive samples were recovered from Companiganj despite a small number of culture-positive swabs there, and Golapganj showed the lowest confirmed prevalence at 1.89 percent. The researchers did not find a statistically significant association between study area and infection status, but the spatial heterogeneity they observed aligns with the idea that management intensity, biosecurity, and animal movement patterns shape local reservoirs of infection in resource-limited farming systems.

Animal-level risk factors told a clearer story. Buffaloes aged between one and three years carried significantly higher odds of infection than calves under one year of age, with an odds ratio of 3.94. The researchers attribute this pattern to the confluence of immunological and management stressors that young adult animals face: weaning, increased movement and mixing with other animals, the onset of draught work or fattening regimens, and dietary and environmental changes that can suppress immune defenses. Meanwhile, calves may retain protection from maternally derived antibodies acquired through colostrum in areas where dams have been vaccinated or exposed, and older adults in endemic regions may have developed acquired immunity that reduces detectable carriage. Sex showed no significant effect, with males at 8.79 percent and females at 5.96 percent prevalence, suggesting that biological sex is far less determinative than age, stress, and management context.

The single strongest predictor of nasal carriage was clinical status. Buffaloes presenting with respiratory symptoms were 8.88 times more likely to test positive for P. multocida than apparently healthy animals, with a prevalence of 18.48 percent among symptomatic animals compared with just 2.49 percent among healthy ones. This association, highly significant statistically, reinforces the pathophysiological role of P. multocida as both a primary and an opportunistic respiratory pathogen. Under conditions of stress—poor nutrition, transport, adverse weather, or concurrent infections—the bacterium proliferates in the upper respiratory tract and can descend into the lower airways, initiating pneumonia or the systemic catastrophe of hemorrhagic septicemia. Once clinical signs appear, treatment is often ineffective, which is why the carrier state identified in this study represents such a critical intervention point.

The antimicrobial susceptibility results are where the study delivers its most alarming message. Among the 29 confirmed isolates, resistance to ampicillin reached 96.55 percent, oxytetracycline 93.10 percent, and penicillin-G 89.65 percent—three drugs that constitute the backbone of empirical treatment in many Bangladeshi livestock systems. Resistance to streptomycin, sulfamethoxazole-trimethoprim, gentamicin, and chloramphenicol also exceeded 50 percent. Only cefixime, a third-generation cephalosporin to which 93.10 percent of isolates remained susceptible, and azithromycin, with 68.96 percent susceptibility, retained meaningful activity. The researchers link the resistance patterns to decades of indiscriminate antibiotic use in a country where veterinary oversight is limited, informal animal health providers are widespread, and farmers frequently administer drugs without susceptibility testing, imposing relentless selective pressure on bacterial populations.

Correlation analysis of the resistance profiles revealed patterns that point to shared underlying mechanisms. Penicillin-G and ampicillin resistance were strongly and positively correlated, consistent with class-wide β-lactam resistance driven by β-lactamase production or altered penicillin-binding proteins. Gentamicin resistance correlated strongly with oxytetracycline resistance, and ampicillin resistance likewise tracked with tetracycline resistance, a pattern the authors interpret as evidence of co-selection: tetracycline and aminoglycoside resistance determinants are commonly carried together on mobile genetic elements such as plasmids and transposons, so selection pressure from one drug class can maintain resistance to another. The lone notable negative correlation, between cefixime and gentamicin, fits the observation that cephalosporins, rarely used in veterinary medicine, have escaped the co-resistance cascade that has eroded the utility of older drugs.

The study’s limitations are acknowledged by its authors. Molecular characterization was confined to species confirmation and capsular typing; more granular tools such as virulence gene profiling, multi-locus sequence typing, and whole-genome sequencing were not applied, and resistance was assessed phenotypically rather than by identifying the specific genes or mobile elements involved. Even so, the practical implications are immediate. The findings argue for routine susceptibility testing before treatment, targeted vaccination programs, improved biosecurity and husbandry to reduce stress in high-risk young adult animals, and strengthened national antimicrobial stewardship. Because cefixime and azithromycin remain effective but are considered critically important antimicrocrobials for human medicine, the authors caution that their use in animals must be judicious to preserve that efficacy.

For Bangladesh, where buffaloes supply milk, meat, and draught power to rural communities operating with limited veterinary infrastructure, the study provides the first systematic molecular characterization of nasal P. multocida carriage in the species. It demonstrates that the reservoir for hemorrhagic septicemia extends beyond visibly sick animals into the herds themselves, and that the bacteria circulating in that reservoir have accumulated resistance to the drugs farmers reach for first. Integrating molecular diagnostics with antimicrobial resistance monitoring, the researchers conclude, will be essential to controlling pasteurellosis and preventing resistant strains from spreading further through buffalo production systems—and, by extension, through the food animal populations on which millions of livelihoods depend.

Subject of Research: Prevalence and antimicrobial resistance of Pasteurella multocida carried in the nasal cavity of buffaloes in Bangladesh

Article Title: Prevalence, Molecular Identification, and Antimicrobial Resistance Traits of Pasteurella multocida Isolated From Nasal Swabs of Buffaloes in Bangladesh

Article References: Ghosh, P. K., Rahman, A., Roy, M., Sakib, M. A. N., Tuha, M. M.-E.-A., Ali, M., Chowdhury, M. S. R., Uddin, M. B., Rahman, M. M., & Hossain, M. M. (2026). Prevalence, Molecular Identification, and Antimicrobial Resistance Traits of Pasteurella multocida Isolated From Nasal Swabs of Buffaloes in Bangladesh. MicrobiologyOpen, 15(5), Article e70432. https://doi.org/10.1002/mbo3.70432

Image Credits: AI Generated

DOI: 10.1002/mbo3.70432

Keywords: Pasteurella multocida, buffalo, Bangladesh, hemorrhagic septicemia, antimicrobial resistance, nasal swabs, capsular type B, PCR, respiratory disease, livestock, multidrug resistance, veterinary microbiology

The urgency of the problem is underscored by events beyond the farm gate. In 2015, an outbreak in Kazakhstan’s Betpak-Dala region killed nearly 200,000 Saiga antelopes within weeks, wiping out more than sixty percent of the regional population and pushing the species closer to extinction. The review notes that haemorrhagic septicemia, with its peracute course and capacity to trigger mass mortality events, bears an epidemiological resemblance to historical scourges such as plague and pneumococcal disease. Because the disease can kill susceptible animals within 24 to 72 hours, therapeutic intervention is rarely feasible, making vaccination the only realistic preventive strategy. The pathogen is also a central player in the bovine respiratory disease complex, the leading cause of morbidity and mortality in feedlot and dairy cattle, which further complicates disease management in production systems.

Conventional vaccines remain the backbone of control programs in endemic countries, and the review evaluates them in meticulous technical detail. Plain bacterins, the earliest whole-cell preparations, offered protection lasting only around six weeks and carried a risk of endotoxin-associated shock, and have now been largely abandoned. Alum-precipitated vaccines, produced by formalin inactivation followed by precipitation with potash alum, remain the most widely used formulations in Asia and Africa because of their simplicity and low cost; the electrostatic binding of antigens to alum promotes uptake by antigen-presenting cells and drives a strong Th2-polarized antibody response, but protective immunity typically lasts only four to six months and post-vaccination shock occurs in some animals. Aluminium hydroxide gel vaccines, which bind antigen ionically to the adjuvant, extend immunity to roughly six months, although one study found protection did not persist beyond 90 days even with immunomodulators such as levamisole and vitamin E.

Oil-adjuvanted vaccines emerge as the benchmark among conventional platforms. Formalin-inactivated organisms emulsified with mineral oil and lanolin induce higher and more sustained antibody titers than alum-based formulations, with field and experimental studies reporting protection lasting eight to twelve months and, in some cases, up to eighteen to twenty-six months. Their thermal stability is a major practical advantage in tropical settings, where cold-chain capacity is limited. Modern commercial adjuvants such as Montanide ISA-50, ISA-70 and ISA-206 reduce reactogenicity while preserving immunogenicity, and comparative field work has shown that formulation choice matters even within this class, with different emulsions performing better in calves than in adult animals. Yet even the best oil-adjuvanted products suffer from injection-site swelling, high viscosity, occasional shock reactions and a continuing dependence on booster doses. Multiple emulsion vaccines, created by re-emulsifying oil-adjuvanted preparations with Tween 80, were developed to ease these drawbacks and have protected buffalo calves for up to nine months and cross-bred calves for up to a year, but they have achieved limited commercial uptake and lack robust head-to-head field comparisons.

The review then turns to modified whole-cell approaches. Digested bacterial lysates, including potassium thiocyanate extracts and bacteriophage-lysed preparations of P. multocida B:2 grown under iron-limited conditions, broaden antigenic exposure and have elicited cross-protective responses in chickens, turkeys, mice and rabbits, with calves showing elevated antibody titers peaking at 90 days, but manufacturing heterogeneity has prevented standardization. Autogenous vaccines, formulated from isolates taken directly from infected herds, offer strain-specific outbreak control but only against homologous serovars and with a delayed onset of immunity. Live attenuated vaccines, which mimic natural infection, have been revitalized by molecular genetics: disruption of the aroA gene, which cripples aromatic amino acid biosynthesis, and of gdhA, which impairs glutamate dehydrogenase activity, produces strains that are attenuated yet immunogenic and protective in calves. Complementary defined mutants targeting lipopolysaccharide biosynthesis genes such as waaQ, capsule genes such as cexA and bcbH, and fimbrial genes including pfhaB1, pfhaB2 and pfhaC have all shown protective potential in experimental models. A recent finding by the lead author adds a novel target: field isolates of P. multocida produce hyaluronidase and can utilize host hyaluronic acid as a nutrient, implicating this metabolic pathway in virulence and opening a new avenue for rational attenuation. Chemically altered live vaccines, such as streptomycin-dependent mutants, have shown variable results across serotypes, underscoring the unpredictability of the approach.

Immunostimulatory and adjuvant-based strategies occupy a middle ground between whole-cell and defined-antigen vaccines. Bacterial DNA enriched with immunostimulatory CpG motifs, when used as an adjuvant for iron-inactivated P. multocida preparations, protected chickens against lethal challenge and raised antibody levels in mice above those achieved with conventional alum-adjuvanted vaccines. Dietary supplementation offers a surprising complementary lever: mice fed arginine-enriched diets alongside a formalin-inactivated vaccine achieved complete protection against challenge, while L-proline and L-glutamine similarly fortified vaccine-induced immunity. The authors stress that such nutritional immunomodulators should be viewed as adjuncts rather than substitutes for antigen-specific vaccination, and that their mechanisms and field efficacy in livestock remain uncharacterized.

Acellular and subunit vaccines represent the shift toward precision design. Candidates focus on the capsule, fimbriae, lipopolysaccharides and outer membrane proteins, whose surface-exposed loops drive antigenic diversity yet also carry conserved epitopes. Immunization with outer membrane proteins, particularly from bacteria cultured under iron-restricted conditions, has elicited cross-protective antibodies across serotypes, and buffalo calves vaccinated intramuscularly with B:2 outer membrane proteins reached peak ELISA antibody titers 21 days after vaccination. Recombinant subunit candidates under investigation include the type 4 fimbrial protein PtfA, the porin OmpH, outer membrane protein OMP87, the lipoprotein PlpE, which induced 80 to 100 percent protection in mice, and iron-regulated heme-binding proteins such as HasR, HemR and HgbA. Synthetic peptides derived from OmpH loop structures have also protected against homologous challenge. Bacterial ghosts, empty envelopes generated through controlled expression of the PhiX174 lysis gene E that preserve native surface architecture without cytoplasmic content, achieved complete protection in laboratory models, while anti-idiotype vaccines mimicking lipopolysaccharide or outer membrane protein epitopes have produced strong protective responses in mice and rabbits. None of these platforms has yet reached commercial application, however, because no universally cross-protective antigen has been identified and most efficacy data come from laboratory animals rather than cattle and buffalo.

Delivery technology emerges as a decisive frontier. Because P. multocida enters through the respiratory tract, intranasal vaccination targeting nasopharyngeal and bronchus-associated lymphoid tissue can stimulate mucosal IgA alongside systemic IgG, placing immunity at the site of pathogen entry. Evidence is compelling: intranasal potassium thiocyanate extract outperformed intramuscular administration, and intranasal delivery of a live attenuated B:2 derivative in buffalo raised antibody levels even in non-vaccinated in-contact animals through secondary transmission, suggesting herd-level protection. A live intranasal aerosol vaccine based on P. multocida B:3,4 was deployed at scale in Myanmar between 1992 and 1995, reaching nearly one million cattle and buffalo. Intradermal vaccination, exploiting the dense antigen-presenting cell network of the skin, offers dose-sparing potential demonstrated for influenza, rabies, poliovirus, yellow fever and hepatitis A vaccines, though some adjuvants provoke unacceptable local reactogenicity by this route. Formulation matters too: particulate carriers and mucosal adjuvants such as MF59, chitosan, Toll-like receptor agonists and mutant enterotoxins can amplify nasal responses, but toxin-based adjuvants have been linked to Bell’s palsy in human intranasal use, demanding caution.

The review’s final assessment is that the deepest unresolved gap is immunological: no validated correlate of protection exists for haemorrhagic septicemia in cattle or buffalo. Serum IgG titers are widely used as surrogate markers, yet no protective threshold has ever been established, and the roles of mucosal IgA, T cells, memory B cells and innate activation remain unmapped in target species. The authors call for standardized endpoints, including serum bactericidal and opsonophagocytic killing assays and IFN-γ ELISpot, harmonized challenge protocols and longitudinal field validation. They further argue that wildlife must enter the equation: no current vaccine has been evaluated in wild ruminants, and the remoteness of outbreak sites, cold-chain limits and the impossibility of repeated handling demand thermostable, oral-bait or aerosol formulations for free-ranging populations. Bridging these translational gaps, the authors conclude, will require coordinated work among immunologists, molecular biologists, veterinarians, wildlife specialists and regulators to convert a century and a half of vaccine innovation into durable, broad-spectrum and economically sustainable control of one of livestock’s most devastating diseases.

Subject of Research: Vaccine development against haemorrhagic septicemia caused by Pasteurella multocida in livestock and wildlife

Article Title: Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia

Article References: Raj, R., & Sharma, A. K. (2026). Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia. Discover Animals, 3(1), Article 86. https://doi.org/10.1007/s44338-026-00244-5

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00244-5

Keywords: haemorrhagic septicemia, Pasteurella multocida, vaccine development, livestock, mucosal vaccination, outer membrane proteins, oil-adjuvanted vaccines, recombinant subunit vaccines, intranasal delivery, wildlife, correlates of protection, cattle and buffalo