Epidermoid Cyst of the Brainstem in 3-Year-Old Child: A Rare Case Report

Epidermoid cysts are infrequent lesions occupying the intracranial space, comprising approximately 1-2% of all intracranial tumors. Brainstem epidermoids are exceptionally uncommon in children; up until now, only a few scattered case reports have been documented in the literature regarding this unique location. These cysts commonly arise from the inclusion of ectodermal elements during neural tube closure. Complete excision of these cysts is challenging due to their close proximity and adherence to the brainstem, which makes it difficult to achieve. As a result, recurrence of the cysts is not uncommon. We have reported a rare case of a 3-year-old with a 5-month history of progressive headache, imbalance while walking and progressive weakness in his right upper limb and lower limb along with difficulty in swallowing. On MRI Brain imaging study he had a pre-pontine epidermoid with intra-axial extension in the pons. The patient underwent retro-sigmoid/suboccipital craniotomy and microsurgical excision of the tumor, including the tumor capsule. After completing the surgery, the cavity was irrigated using a solution containing hydrocortisone and Ringer lactate to prevent the occurrence of aseptic meningitis. In the postoperative, the patient recovered without any complications, as all symptoms showed immediate improvement, and the lower cranial nerves returned to normal functioning.

Endoscopic Transnasal Navigation Guided Treatment of Clivus Abscess in Adult with Mucormycosis: A Rare Report

Osteomyelitis and abscess of the clivus are rare conditions thought to arise from contiguous spread of infection from the paranasal sinuses. Clival osteomyelitis is a rare potentially life-threatening skull base infection which is generally challenging to diagnose and treat. It is typically seen in the pediatric population and is very rare in the adult population. The exact pathophysiology of osteomyelitis of the clivus is relatively uncertain. Here, we describe a case of a 32-year-old immunocompetent female with a primary complaint of headache, with no significant medical history of diabetes, hypertension or rhinosinusitis or SARS COV-2 for the past 18 months. This case report demonstrates an image-guided and endoscopic approach to surgical localization and treatment of abscesses in the clival area.

Pituitary Apoplexy Presenting with Isolated Third Nerve Palsy: A Rare Case Report

A 46-year-old female came to neurosurgery outpatient department with sudden onset of drooping of RE upper eyelid and restriction of movements in adduction, depression and elevation in right eye. Patient was a known case of diabetes mellitus whose blood sugar levels were deranged. On examination, patient was diagnosed pituitary macroadenoma. Patient was treated for her uncontrolled diabetes mellitus following which she had underwent transsphenoidal pituitary macroadenoma removal. On treatment, patient's ptosis had subsided and restriction of movement has resolved.

Immediate postoperative resolution of syrinx post-C1/C2 fixation in an operated case of foramen magnum decompression for Chiari malformation: Is Goel's procedure a rescue surgery or a gold standard?

Chiari malformation (CM) is a common neurological disorder with foramen magnum decompression (FMD) as a commonly accepted treatment. The authors present a case of CM-1 wherein there was no radiological instability preoperatively and FMD was done as a treatment, after which the patient improved transiently only to deteriorate further. Atlantoaxial fixation was done as a second-stage procedure, after which the patient improved clinically and radiologically. The knowledge of this case and surgical entity should be borne in mind before the formulation of a treatment plan. It is important that the solution is to identify and treat the underlying pathology rather than to decompress and directly manipulate the tonsils.

A rare case of subependymal giant cell astrocytoma presenting with spontaneous intratumoral hemorrhage

ABSTRACT

Subependymal giant cell astrocytomas (SEGAs) are low-grade gliomas usually arising in the periventricular regions near the foramen of Monro seen exclusively with tuberous sclerosis complex. Incidence of hemorrhage in SEGA is less than 1% with only 10 cases reported in English literature. We present a similar case of SEGA with spontaneous intratumoral hemorrhage in a 35-year-old male with cutaneous manifestations of tuberous sclerosis complex and acute onset headache with convulsion.

Single-level ossified ligamentum flavum causing a holocord syrinx: illustrative case

BACKGROUND

Syringomyelia is a neurological disorder that is caused by abnormal cerebrospinal fluid flow or circulation. It is an incidental finding in most cases, predominantly presenting with sensory symptoms of insensitivity to pain and temperature. Spinal ossified ligamentum flavum (OLF) leading to syringomyelia is one of the rare causes. The authors report an unusual case of syringomyelia due to a thoracic OLF.

OBSERVATIONS

A 54-year-old female presented with backache, difficulty walking, spasticity in the bilateral lower limbs, tingling sensation in the bilateral lower limbs, and paraparesis for 5 years. Her radiological investigations were suggestive of an OLF causing a syrinx. She underwent laminectomy, and her syrinx resolved on subsequent follow-up.

LESSONS

A syrinx due to a single-level OLF is rare, and this uncommon cause should be kept in mind while formulating treatment plans.

Unusual Presentation of Osteoid Osteoma of the Cervical Spine with Dysphagia: A Case Report

It is uncommon for bony cervical spine lesions to cause dysphagia. Middle-aged female presented in the outpatient clinic with complaints of dysphagia of insidious onset. Patient's medical history, clinical manifestation and imaging studies guided the diagnosis of spinal osteoid osteoma. The presentation and surgical management are discussed in this report.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03835-w.

Cirsoid Aneurysm of Occipital Artery-Rare of the Rarest

A case of 33 year old man diagnosed with a rare case of Cirsoid aneurysm of occipital artery was treated under general anaesthesia for surgical excision. An interdisciplinary approach of Neurosurgery and Oral and Maxillofacial team was made. Here we have discussed the clinical steps performed in the management of Cirsoid aneurysm of occipital artery. In-toto excision and thorough follow up has uneventfully lead to success in the outcome.

Contrecoup Extradural Hematoma: When Hematomas Do Not Follow Rules

Extradural hematoma (EDH) is a fairly common entity in neurosurgical practice but EDHt at a contrecoup site and crossing a cranial suture is rare. The authors present a case of EDH due to contrecoup injury in whom sutural diastases was noted and hematoma was seen to be crossing the adjacent suture. This was accompanied with subdural hematoma (SDH) at the coup site. According to the best of our knowledge, it makes the case only the 13^th such to be reported in adults. A 27-year-old male patient was brought by relatives with a history of fall from a height resulting in head trauma over the left posterior parietal region. The patient presented with headache at the site of impact. Computed tomography (CT) scan of the brain revealed an undisplaced fracture of parietal bone on the left side (coup site) along with a small concavo-convex hyperdense lesion suggestive of a SDH. Scan also revealed a large biconvex, hyperdense lesion in the right frontoparietal region (contrecoup site). The hematoma was seen to be evidently crossing the coronal suture. Sutural diastases of coronal suture was suspected and the same was noticed intraoperatively. Approximately 80cc of clot was removed and hemostasis was achieved through coagulation of the middle meningeal artery and via dural hitch sutures. Contrecoup EDH across the adjacent suture with sutural diastases is rare as it does not follow the set rules of hematomas. A high index of suspicion is central in arriving at a rapid diagnosis and an early surgery to achieve a favorable outcome. The authors recommend a CT scan along all three planes along with a three-dimensional reconstruction for ready diagnosis. Contrecoup EDH with sutural diastases is a distinct and potentially dangerous entity and neurosurgeons should be aware of the same.

A Rare Case of Primary Pituitary Tubercular Abscess Mimicking a Pituitary Adenoma

Primary pituitary tuberculosis (PTA) is a very rare disease. The clinical diagnosis is difficult as it is clinically radiologically indistinguishable from other sellar lesions. We present a case of PTA without any predisposing etiology and radiologically mimicking a pituitary macroadenoma. The patient underwent endoscopic transsphenoidal resection where pus admixed with mucoid was seen coming out of the lesion intraoperatively. Histology of the cyst wall was suspective of tuberculous etiology and QuantiFERON Tb Gold done for confirmation was positive. Postoperatively patient showed obvious improvement in visual symptoms. Patient developed diabetes insipidus and was put on desmopressin and was started with anti-tuberculosis medication for 18 months. Timely surgical intervention followed by anti-tubercular therapy and hormone replacement is the mainstay of treatment in these cases. For intraoperative management, we advise thorough wash with antibiotic and saline rather than curetting the walls of the abscess to decrease the postoperative incidence of endocrine abnormalities.

Intra-diploic epidermoid cyst: An iceberg lesion

Introduction: Intraosseous epithelial inclusion cysts of the skull, presenting as lytic defects, constitute a very small percentage of the primary intracranial tumours. The case is presented by virtue of not only the rarity of the variant but also to highlight the importance of timely intervention by a neurosurgeon after adequate investigation and in a tertiary care setting. Case Report: A 45 year old female patient presented to the local Primary Healthcare Centre(PHC) with a small scalp swelling in the occipital region. . Intraoperative identification of intracranial extension was made by the surgeon as inferior margin of the swelling couldn’t be reached and also by palpation of the huge bone defect following which the procedure was abandoned midway and patient was referred to our centre for further management. Imaging: Contrast Enhanced Computerised Tomograhy(CECT) revealed a well defined, mixed density lesion with hypodense and an isodense component in right occipital region. Lesion was measuring 4.2(Cranio caudal) x 3.3(Antero posterior) x 3.6( transverse) cm. A sharp marginated bone defect was noted involving both the outer and inner tables of the occipital bone. Operative management: Lesion was approached through a right occipital craniotomy wherein the margins of bone defect were nibbled away to gain a wide access to the lesion. Pearly white, flaky contents of the lesion along with capsule were identified and excised completely. Discussuion: Intradiploic epidermoid cysts are very rare, accounting for <3% of all intracranial epidermoid cysts.(5) These cysts grow very slowly and usually present as painless bony swelling under the scalp. Conclusion: Cranial epidermoid is a fairly common entity and intradiploic variant of the same isnot uncommonly seen in neurosurgical practise. These lesions may present as a small scalp lesion which should not be judged based on its apparent size as these lesions are not infrequently known to have a bigger intracranial extension

Remote extradural hematoma after supratentorial brain tumor surgery: A rare complication of a routine surgery

Background: Hemorrhages in the surgical cavity post resection of tumor aren’t uncommon and neurosurgeons are well versed with this entity, however occurrence of an Extra Dural Hematoma(EDH), that too at a site remote to the surgical cavity, is rare. The study presents 3 cases of post operative remote site EDH after tumor resection with review of literature  and an attempt to define and discuss the variables which play a role in determining the occurrence, extent and prognosis of the same. Methods: The study investigated 601 patients who underwent tumor resection in the Department of Neurosurgery, Dr D Y Patil Hospital, from January 2017 to December 2019. All patients had a normal coagulation profile preoperatively. Postoperative remote EDH occurred in 3 patients whose data was examined closely in terms of age, sex, location, final diagnosis and treatment. Results: Of the 601 patients who underwent tumor resection from Jan 2017 to Dec 2019, a total of 3 patients in our study were found to have a post-operative remote site EDH. Two of these patients were male and 1 female. The age range was 35 to 46 years with a mean of 41 years. Neither did any of these patients have a pre-existing hydrocephalus nor were they subjected to a CSF diversion procedure preoperatively. All 3 patients developed EDH on the ipsilateral side wherein 2 of our patients had a hematoma in the ipsilateral frontal region anterior to the surgical cavity while 1 patient developed hematoma in ipsilateral parietal region posterior to surgical cavity. Hematomas were unilateral with no extension to opposite side. Two patients had to be re-operated in an emergency setting while one patient was conservatively managed.   Conclusion: In patients with an expected volume loss via large tumor size, excess blood and CSF loss and a large craniotomy, remote EDH may develop and the  neurosurgeon must have a high index of suspicion for this entity

Neuroophthalmic Manifestations of Intracranial Tumours in Children

BACKGROUND

All children between 0 and 16 years presenting with brain tumours confirmed by Magnetic Resonance Imaging (MRI) and treated surgically in our institute were included in this study.

OBJECTIVE

The aim of this study is to evaluate the neuroophthalmic and clinical characteristics of intracranial space occupying lesions in children.

METHODS

Neuroophthalmic manifestations along with location of the tumour by contrast-enhanced MRI, type of surgical intervention, and postoperative histopathological diagnosis were evaluated.

RESULTS

In pediatric brain tumours, male preponderance was seen and supratentorial location was more common in general, while in older children, infratentorial tumours were more common than supratentorial tumours. Headache, vomiting, and cerebellar signs were the commonest neurological features. Diminution of vision, diplopia, and strabismus were the commonest ophthalmic symptoms. Papilledema, ophthalmoparesis, and nystagmus were the most frequent ophthalmological signs. Neurological manifestations of seizures, altered sensorium and motor deficits were more frequently seen in supratentorial tumours, while cranial nerve involvement and ataxia were seen in infratentorial tumours. Ophthalmological manifestations including diplopia, strabismus, ophthalmoparesis, and nystagmus were more frequently seen in infratentorial tumours. Astrocytoma was the most frequent histopathological diagnosis followed by medulloblastoma.

CONCLUSION

Diagnosis of pediatric intracranial tumours is complex and requires a multidisciplinary approach for prompt management. An ophthalmologist should have a high index of suspicion for brain tumours especially in patients presenting with common ocular symptoms like diminution of vision, diplopia, and strabismus without any neurological symptoms.

A rare case of an aneurysmal bone cyst of the temporal bone

Aneurysmal bone cysts (ABCs) are benign bone lesions mainly occurring at the metaphyseal end of long bones and are a rarity in the calvarium. The reported incidence of this lesion in the skull is 1% of all the ABC. It is a benign condition that may extend intracranially. We report here a case of a 3½-year-old male child who presented with a bony hard, painless, and gradually enlarging swelling over his right temporal region. Radiological investigations and histology revealed that the lesion was an ABC. A total surgical excision was achieved despite its intracranial extension along with the involvement of dura. Prognosis is excellent with total removal as a total surgical removal of the lesion is considered curative. The rarity of the lesion along with a good surgical result despite an intracranial extension with dural involvement prompted this report.

A Rare Chronic Presentation of Schwannoma with Hemorrhage

Spinal schwannomas are slow-growing benign tumors arising from the nerves. In the spinal cord, they arise most commonly from cervical and lumbar levels. They are mostly intradural extramedullary (IDEM) accounting for 30% of intradural tumors showing a female preponderance. They are seen occurring between 25 and 50 years of age. Most of these cases show acute presentation as hemorrhage within the tumor with weakness. This is a rare presentation by itself reported by only 12 cases world over. It is even rarer to see them show chronic presentation. We are reporting one such case of a 61-year-old female who presented to us with chronic low backache for 3 years with radicular symptoms in the bilateral lower limbs following a fall on her back. Magnetic resonance imaging was done which showed a well-defined IDEM lesion from L3 to L5 vertebral level which was isointense on T1 and hyperintense on T2 with a peripheral rim and short inversion time inversion-recovery showed fluid-fluid level within. Gradient-recalled echo showed blooming with no suppression on fat-sat and no diffusion restriction. A computed tomography angiography was done which ruled out vascular malformation. Intraoperatively, a large feeding vessel with a tumor was visualized after laminectomy was done for the corresponding levels. Postoperatively, the patient showed a significant decrease in radicular symptoms and was discharged after 2 weeks with an uneventful postoperative period. HPE of the lesion showed sheets of fascicles of elongated spindle cells arranged in loose myxoid matrix with hyperchromatic nuclei and scanty hemorrhage and lymphocytic infiltrates suggestive of schwannoma with myxoid degeneration. Immunohistochemistry also confirmed a diagnosis of schwannoma. From this case, it is seen that the diagnosis of a spinal schwnnoma showing delayed presentation with atypical imaging findings is a challenge and must needs a high index of suspicion and appropriate surgical planning.

Microendoscopic discectomy for lumbar disc herniations

Introduction:

Lumbar disc herniation is one of the main causes of discogenic low back pain and reported to affect 60%–80% of people during their lifetime. The two main surgical modalities for intervertebral disc surgery are standard open discectomy and minimally invasive discectomy which include percutaneous endoscopic lumbar discectomy and microendoscopic discectomy (MED). We report our experience with the same technique of MED to evaluate the efficacy of MED for lumbar disc pathology.

Aims and Objectives:

The aims and objectives were to study the efficacy, advantages, and associated limitations and complications of MED in lumbar disc herniations.

Materials and Methods:

This study was carried out on 300 patients who had single-level herniated disc. The procedure was done by Microscopic Endoscopic Tubular Retraction System. Preoperative assessment of Visual Analog Scale (VAS) and modified Suezawa and Schreiber (MSS) clinical scoring system was documented 1 day prior to surgery. Postoperative results were determined to be excellent, good, fair, or poor according to MacNab criteria and also evaluated by MSS clinical scoring system on postoperative day 7 and after 6 months.

Results:

A total of 187 patients were males and 113 patients were females and a majority of patients were in the age group of 31–40 years. A total of 192 patients had disc herniations at L4–L5 level. The mean operative time was 82 min and the mean hospital stay was 5.3 days. Eighteen cases (6%) developed postoperative complications including discitis, dysesthesia, recurrent prolapsed intervertebral disc, residual disc, dural tear, and nerve root injury. Mean preoperative VAS score was 8.7 and the mean postoperative VAS scores at postoperative day 7 and at 6 months were 2.25 and 1.12, respectively. The mean preoperative MSS score was 3.27 and the MSS scores at postoperative day 7 and at 6 months were 7.42 and 8.2, respectively. The overall successful outcome of the endoscopic discectomy after 6-month follow-up on the basis of VAS improvement percentage was 87.6%, MSS scoring percentage was 91.6%, and MacNab scoring percentage was 92.67%.

Conclusion:

MED is a safe and effective technique. It offers decreased blood loss, shorter operative time, shorter in-hospital stay, decreased need for pain medication, decreased rate of infection, and a shorter return to work time. Limitations of this technique include a learning curve which is related to surgery time, complications, conversion to open procedures, and recurrent disc herniation.

Abnormal Migration and Extrusion of Abdominal End of Ventriculoperitoneal Shunt: An Experience of Eight Cases

Background:

Ventriculoperitoneal (VP) shunt is commonly used in the treatment of hydrocephalus. Migration and extrusion of the distal end of the VP shunt are relatively rarely occurring complications.

Aim:

To retrospectively analyze patients with extrusion of the abdominal end of ventriculoperitoneal shunts and evaluate the possible etiology and outcome.

Settings and Design:

All patients presenting with extrusion of lower end of the shunt were included. The variables collected were age, sex, site of extrusion, time duration of extrusion, presence of local infection, meningitis, shunt dependency, and treatment received. Contrast-enhanced computed tomography of brain was carried out in all patients to rule out retrograde migration of infection in the cranial cavity.

Materials and Methods:

Eight patients of abnormal migration and extrusion of lower end of VP shunt were included.

Results:

The distal end of VP shunt was extruded from the anus (n = 3), vagina (n = 2), and anterior abdominal wall (n = 3). In five of these patients, shunt catheter was draining cerebrospinal fluid (CSF), the children were afebrile and CSF was sterile. In three children with extrusion of the shunt through the abdominal wall, the shunt tract was infected. Two of these patients had abscess in the shunt tract, which required incision and drainage. Both these patients had meningitis with a growth of Streptococcus species from CSF. Seven patients required further CSF diversion such as endoscopic third ventriculostomy (n = 3) or placement of VP shunt (n = 4).

Conclusion:

Distal tip migration of VP shunt may prove to have potentially serious complications such as meningitis. A prompt and aggressive protocol of management is recommended.

The role of transforaminal percutaneous endoscopic discectomy in lumbar disc herniations

OBJECTIVES

To study 1)the efficacy of transforaminal percutaneous endoscopic lumbar discectomy in lumbar disc herniations.2) limitations and advantages of the surgical procedure. 3)morbidity and complications associated with the procedure.

MATERIALS AND METHODS

This study was carried out on 120 patients who had single level herniated disc Pre-operative assessment of VAS and MSS scoring systems were documented one day prior to surgery. Post operative results were determined by MacNab criteria and by modified Suezawa and Schreiber clinical scoring system (MSS score).

RESULTS

Maximum patients were in the age group of 31 to 40 years and 83.43% of the patients were males. 80% patients had lumbar disc herniation at L4-L5 level, The mean operative time of endoscopic discectomy was 52.28 minutes and the mean hospital stay was 2.1days.8 cases of L5-S I were abandoned due to high iliac bone and hence their disc could not be accessed. Out of 112 patients who underwent operation, 2 patients developed discitis and 1 was found to have dysesthesia. Also recurrent prolapsed intervertebral disc was seen in 6 cases The mean preoperative and 6 months follow-up VAS score was 8.4 and 1.89 respectively. Mean preoperative and 6 months follow-up Modified Suezawa And Schreiber Clinical Scoring System(MSS Score) was 3.47 and 7.92 respectively. MSS score showed excellent and good outcome in 82.12% patients and Modified Macnab Criteria showed excellent and good outcome in 89.3% patients at 6months follow-up.

CONCLUSION

TPELD can be a reasonable alternative to conventional microscopic discectomy for the treatment of patients with LDH. We also conclude that TPELD is not an effective procedure for L5-S 1 disc and an open procedure should be opted for better outcomes.

Giant intradural intramedullary epidermoid cyst Report of two cases with varied presentations

We report two cases with giant intramedullary epidermoid cysts in the thoracolumbosacral and lumbosacral regions with varied presentations. Magnetic resonance (MR) imaging of the thoraco lumbar spine in case 1revealed an intramedullary elongated mass extending from T10 to S2 level causing significant widening of the spinal canal while MR imaging of lumbosacral spine in case 2 showed straightening of the lumbar spine and spina bifida at L5 level with conus at L3 and a lobulated long segment intramedullary solid cystic lesion extending from L2 to S2 veterbrae. The lesion was surgically resected and the pathology revealed an epidermoid cyst. Epidermoid cysts of the spinal cord are rare tumours in the adult population which may be congenital or acquired. Symptoms arising from epidermoid cysts vary with the level of involvement. The treatment of epidermoid cysts is surgical and if possible, complete removal is the goal.

Beta-hemolytic streptococcal infections in trauma patients

PURPOSE

β-hemolytic streptococci (βHS) causes a diverse array of human infections. The molecular epidemiology of β-hemolytic streptococcal infections in trauma patients has not been studied. This study reports the molecular and clinical epidemiology of β-hemolytic streptococcal infections at a level 1 trauma centre of India.

METHODS

A total of 117 isolates of βHS were recovered from clinical samples of trauma patients. The isolates were identified to species level and subjected to antimicrobial susceptibility testing. Polymerase chain reaction (PCR) assay was done to detect exotoxin virulence genes. The M protein gene (emm gene) types of GAS strains were ascertained by sequencing.

RESULTS

Group A Streptococcus (GAS) was the most common isolate (64 %), followed by group G Streptococcus (23 %). A large proportion of GAS produced speB (99 %), smeZ (91 %), speF (95 %) and speG (87 %). smeZ was produced by 22 % of GGS. A total of 25 different emm types/subtypes were seen in GAS, with emm 11 being the most common. Resistance to tetracycline (69 %) and erythromycin (33 %) was commonly seen in GAS.

CONCLUSIONS

β-hemolytic streptococcal infections in Indian trauma patients are caused by GAS and non-GAS strains alike. A high diversity of emm types was seen in GAS isolates, with high macrolide and tetracycline resistance. SpeA was less commonly seen in Indian GAS isolates. There was no association between disease severity and exotoxin gene production.

Pulsed-field electrophoretic fingerprinting of Salmonella indiana and its epidemiological applicability

Eight Xba I-generated pulsed-field profile (PFP) types and four subtypes within one of the most common PFP types have been identified in Salmonella indiana from patients, poultry and human food in England and Wales in the three-year period from January 1994 to December 1996. Two PFP types have predominated, PFP X1 and PFP X2. Although the PFP X1 type was identified throughout the study period, the PFP X2 type was not identified until late 1995, subsequently becoming the most common PFP type in humans in the first six months of 1996 with a significant distribution in elderly patients. It is concluded that PFGE can be used in support of epidemiological investigations for the subdivision of Salm. indiana. Furthermore, as both conditions and interpretation criteria can be easily standardized, it is suggested that for many salmonella serotypes, PFGE can provide the basis for a definitive scheme of genotypic subtyping suitable for epidemiological investigations at both a national and international level.

The heteroduplex mobility assay (HMA) as a pre-sequencing screen for Norwalk-like viruses

Molecular epidemiological studies of Norwalk-like viruses (NLVs), previously known as small round structured viruses (SRSVs), are dependant currently on DNA sequencing of PCR amplicons, which is expensive and time consuming. The Heteroduplex Mobility assay (HMA) was evaluated as a method for identification of PCR amplicons from the commonly circulating NLV strains without DNA sequencing. The procedure was developed for use with two reference strains, a Mexico virus-like strain (MXV-like; Hu¿NLV¿RBH¿1993¿UK) and the Grimsby virus strain (Hu¿NLV¿Gimsby¿1995¿UK), and was optimised with regards to the annealing and electrophoresis conditions and the electrophoresis gel matrix. Using the optimised conditions, amplicons of less than 90% sequence identity formed visible heteroduplexes, allowing the strains to be placed into three categories; Mexico-like, Grimsby-like and non-Mexico virus/non-Grimsby virus strains. Outbreak strains 'genotyped' previously by DNA sequencing as Mexico virus or Grimsby virus were identified correctly by the heteroduplex mobility assay. The procedure was applied prospectively to strains from 130 outbreaks occurring in the UK between 1997 and 1998. Heteroduplex mobility assay was successful on 120 (92%) strains of which 68 (57%) were GRV-like strains, three (2.5%) were Mexico virus-like strains and 49 (41%) were categorised as non- Mexico/non-Grimsby virus strains. Amplicons from 50 of the 120 strains were sequenced and there was perfect correlation between the heteroduplex mobility assay categorisation and phylogenetic analysis. HMA offers a rapid, robust and far cheaper alternative to sequencing for the identification of prevalent Norwalk-like virus genotypes for molecular epidemiological studies.

National outbreak of Salmonella senftenberg associated with infant food

Eight cases of Salmonella senftenberg infection in infants were identified in the first half of 1995 in England, five were indistinguishable S. senftenberg strains. A case-control study showed an association between illness and consumption of one brand of baby cereal (P = 0.03). The cereal manufacturer reported isolating S. senftenberg in June 1994 from an undistributed cereal batch. Outbreak strains and the cereal strain were all plasmid-free in contrast to other human isolates of S. senftenberg in the same period. Changes in the production process were implemented to prevent further contamination. Surveillance centres should strengthen the detection and investigation of outbreaks of gastrointestinal infection in susceptible groups, especially young children. In this outbreak, the study of only five cases led to identification of the vehicle of infection. Even when few cases are reported, epidemiological investigation in conjunction with molecular typing may lead to public health action which prevents continuing or future outbreaks.

Plasmid characterization and pulsed-field electrophoretic analysis demonstrate that ampicillin-resistant strains of Salmonella enteritidis phage type 6a are derived from Salm. enteritidis phage type 4

Plasmid incompatibility studies have demonstrated that strains of Salmonella enteritidis phage type (PT) 6a resistant to ampicillin possess a 36 megadalton incompatibility group (Inc) X plasmid coding for resistance to ampicillin which is capable of converting strains of Salm. enteritidis belonging to PTs 1 and 4 to PT 6a, and PT 8 to PT 13. However, pulsed-field gel electrophoresis (PFGE) has demonstrated that all clinical isolates of PT 6a have a characteristic XbaI pulsed-field profile which is distinct from that of PT 1 and which can only be differentiated from that of PT 4 by the presence of plasmid-associated fragments of less than 45 kb. It is concluded that ampicillin-resistant strains of Salm. enteritidis PT 6a are derived from strains of Salm. enteritidis PT 4 by acquisition of an Inc X ampicillin resistance plasmid.