Efficacy of indefinite chronic oral antimicrobial suppression for prosthetic joint infection in the elderly: a comparative study

BACKGROUND

During prosthetic joint infection (PJI), surgical management is sometimes impossible and indefinite chronic oral antimicrobial suppression (ICOAS) may be the only option. The outcomes of elderly patients who benefited from ICOAS with strictly palliative intent were evaluated.

METHODS

A national retrospective cohort study was performed in France, involving patients aged >75 years with a PJI who were managed with planned life-long ICOAS from 2009 to 2014. Patients who experienced an event were compared to those who did not. An event was defined as a composite outcome in patients undergoing ICOAS, including local or systemic progression of the infection, death, or discontinuation of antimicrobial therapy because of an adverse drug reaction.

RESULTS

Twenty-one patients were included, with a median age of 85 years (interquartile range 81-88 years). Eight of the 21 patients experienced an event: one had an adverse drug reaction, three had systemic progression of sepsis, and two had local progression. Two of the 21 patients died. No death was related to ICOAS or infection. There was no significant difference between the population with an event and the population free of an event with regard to demographic, clinical, and microbiological characteristics (p>0.05).

CONCLUSIONS

ICOAS appeared to be an effective and safe option in this cohort.

Postoperative infections after excision of neurogenic heterotopic ossifications at the hip: Risk factors and causative organisms

BACKGROUND

Neurogenic heterotopic ossification (NHO) is usually treated by surgical excision. Postoperative infection (POI) is a possible complication, whose epidemiology, causative organisms, and risk factors are poorly known. We therefore conducted a case-control study to (1) identify the risk factors for POI after surgical excision of NHO at the hip, (2) determine the frequency of POI, (3) and identify the causative organisms.

HYPOTHESIS

Risk factors for POI after NHO excision at the hip can be identified.

MATERIAL AND METHODS

In this retrospective case-control study, the BANKHO database for patients with NHO at our centre was used to identify risk factors by comparing patients with and without POI after NHO excision at the hip. To this end, odds ratios (ORs) with their 95% confidence intervals (95%CIs) were computed for each main criterion. Postoperative follow-up was at least 6 months.

RESULTS

Between 1993 and 2013, 411 hip NHO excisions were performed. Among them, 42 (10%) were followed by POI. The American Society of Anesthesiologists (ASA) score was I in 2/42 (5%) patients with vs. 74/369 (20%) patients without POI, II in 30/42 (71%) patients with vs. 258/369 (70%) patients without POI, and III in 10/42 (24%) patients with vs. 37/369 (10%) patients without POI (P<0.01). Mean age was 31±11 years (range, 17-79years) in the group with POI and 39±14 years (range, 15-77years) in the group without POI (P<0.01). The NHO was related to spinal cord injury in 26/42 (62%) patients with POI compared to 92/369 (25%) patients without POI (P<0.01). ORs indicated a significant risk increase in patients with an ASA score of III (2.84; 95%CI, 1.28-6.31), age younger than 30 years (1.85; 95%CI, 1.03-3.32), and spinal cord injury as the cause of NHO (4.89; 95%CI, 2.67-8.98). The predominant organisms were staphylococci (skin flora) in the patients with spinal cord injury and bacteria commonly found in intensive care units in the other patients.

DISCUSSION

A higher ASA score, younger age, and spinal cord injury as the cause of NHO at the hip are risk factors for POI. The proportion of patients with POI after hip NHO excision was 10%, in accordance with previous reports. POI was more common among patients with spinal cord injury (22% vs. 5% in the other patients). Neither changes in prophylactic antibiotic therapy regimens nor the institution of a detailed skin preparation protocol affected the frequency of POI. Skin pH alterations may deserve to be investigated with the goal of diminishing the risk of POI, most notably in spinal cord injury patients.

LEVEL OF EVIDENCE

III, case-control study.

[Splenic abscesses: From diagnosis to therapy]

Splenic abscess is septic collection which occurs after haematogenous spread or local dissemination. Splenic abscess is an uncommon and rare condition, more frequently affecting male and immunocompromised patients. There are no guidelines regarding its diagnosis and management. Computed tomography (CT) scan is highly sensitive and specific (95% and 92%, respectively) in the diagnosis of splenic abscess. Diagnosis is based on blood cultures which are positive in 24 to 80% of cases. Bacterial growth culture of abscess after drainage is more efficient (50-80%) and can be performed after surgery or percutaneous drainage under imaging, including CT scan. Microorganisms involved are frequently enterobacteriaceae, gram-positive cocci and anaerobes. This particular ecology leads to an empiric broad-spectrum antibiotic therapy, with a variable duration, from 10days to more than one month. Management remains very close to the one applied in case of liver abscesses. The role of splenectomy in the prevention of recurrence remains controversial. We reviewed the literature regarding splenic abscesses, from diagnosis to therapy.

Is faecal microbiota transplantation an option to eradicate highly drug-resistant enteric bacteria carriage?

Carbapenem-resistant Enterobacteriaceae (CRE) or vancomycin-resistant enterococci (VRE) carriage present a major public health challenge. Decolonization strategies are lacking. We aimed to evaluate the impact of faecal microbiota transplantation (FMT) on a cohort of patients with digestive tract colonization by CRE or VRE. Eight patients were included: six carrying CRE and two colonized by VRE. One month after FMT, two patients were free from CRE carriage, and another patient was free from VRE after three months. In our experience, this strategy is safe.

Implementation of a simple innovative system for postprescription antibiotic review based on computerized tools with shared access

BACKGROUND

Controlling antibiotic use in healthcare establishments limits their consumption and the emergence of bacterial resistance.

AIM

To evaluate the efficiency of an innovative antibiotic stewardship strategy implemented over three years in a university hospital.

METHODS

An antimicrobial multi-disciplinary team (AMT) [pharmacist, microbiologist and infectious disease specialist (IDS)] conducted a postprescription review. Specific coding of targeted antibiotics (including broad-spectrum β-lactams, glycopeptides, lipopeptides, fluoroquinolones and carbapenems) in the computerized physician order entry allowed recording of all new prescriptions. The data [patient, antibiotic(s), prescription start date, etc.] were registered on an AMT spreadsheet with shared access, where the microbiologist's opinion on the drug choice, based on available microbiology results, was entered. When the microbiologist and pharmacist did not approve the antibiotic prescribed, a same-day alert was generated and sent to the IDS. That alert led the IDS to re-evaluate the treatment.

FINDINGS

From 2012 to 2014, 2106 targeted antibiotic prescriptions were reviewed. Among them, 389 (18.5%) generated an alert and 293 (13.9%) were re-evaluated by the IDS. Recommendations (mostly de-escalation or discontinuation) were necessary for 136 (46.4%) and the prescribers' acceptance rate was 97%. The estimated intervention time was <30 min/day for each AMT member. This system allowed correct use of targeted antibiotics for 91.8% of prescriptions, but had no significant impact on targeted antibiotic consumption.

CONCLUSION

This computerized, shared access, antibiotic stewardship strategy seems to be time saving, and effectively limited misuse of broad-spectrum antibiotics.

Prospective evaluation of antibiotic treatment for urological procedure in patients presenting with neurogenic bladder

OBJECTIVES

Patients presenting with neurogenic bladder often require urological procedures (urodynamic testing and botulinum toxin injections) and a preventive antibiotic therapy. We aimed to assess the efficacy of this little known strategy in a cohort of patients.

PATIENTS AND METHODS

All patients presenting with neurogenic bladder who underwent urological procedure were included in the study. They received an antibiotic therapy in accordance with the urine cytobacteriological examination results. The antibiotic therapy was initiated two days before the procedure and prolonged up until two days after the procedure if the culture was positive. Patients were treated with a single dose of fosfomycin-trometamol in case of a negative culture. The main study outcome was the occurrence of urinary tract infection (UTI), defined by a positive urine culture and symptoms, up until 14 days after the procedure.

RESULTS

A total of 80 urological procedures were performed. Mean patient age was 47±13.1 years (sex ratio 1.22); 59 (73.8%) presented with asymptomatic bacteriuria before the procedure. Nine (11.1%) UTIs were recorded on Day 14, of which one (1.2%) was febrile. Two patients required an additional curative antibiotic therapy. No patient was hospitalized. Overall, 77.8% of UTIs were cured without antibiotic therapy.

CONCLUSION

Screening and treating asymptomatic bacteriuria before urological procedures seems unnecessary and vainly exposes this population at high risk of infectious diseases to antibiotic therapies. This data should be confirmed by a randomized clinical trial.

Diagnostic delay of pyogenic vertebral osteomyelitis and its associated factors

OBJECTIVES

Pyogenic vertebral osteomyelitis (PVO) is a rare disease with possible severe complications (e.g. sepsis and spinal cord injury). In the 1990s, diagnostic delay (DD) was often extensive as PVO has a non-specific clinical spectrum, mostly afebrile with back pain, and access to magnetic resonance imaging (MRI) was not straightforward. Our aim was to perform a new study focusing on the clinical spectrum and DD of PVO and its associated factors.

METHOD

This study examined a prospective cohort of 88 patients having PVO with microbiological identification between 15 November 2006 and 15 November 2010.

RESULTS

The 88 patients included in the study (female:male ratio 1:8) had a mean age of 64.1 years. The mean (sd) DD was 45.5 (50.4) days (range 2-280), and 46 patients (52.2%) were febrile at diagnosis. The main microorganism involved was Staphylococcus (n = 45; 51.1%). In univariate and multivariate analyses, age > 75 years, antecedent back pain, involvement of bacteria, topography of PVO, and anti-inflammatory drug intake did not affect the DD, unlike a C-reactive protein (CRP) value > 63 mg/L or a positive blood culture (DD lowered from 73 to 17 days and from 90 to 30 days, respectively). Conversely, X-ray investigation was associated with a longer DD (from 14 to 34.7 days). Severity at diagnosis was not significantly different depending on the intake of anti-inflammatory drugs.

CONCLUSIONS

Despite easier access to MRI, the DD for PVO remains long. One shortening factor is a high CRP value, which could be a useful diagnostic tool in case of back pain. Anti-inflammatory drugs seem to have no impact on DD and severity at diagnosis.

Serum protein electrophoresis: an interesting diagnosis tool to distinguish viral from bacterial community-acquired pneumonia

29-69 % of pneumonias are microbiologically documented because it can be considered as an invasive procedure with variable test sensitivity. However, it drastically impacts therapeutic strategy in particular the use of antibiotics. Serum protein electrophoresis (SPEP) is a routine and non-invasive test commonly used to identify serum protein disorders. As virus and bacteria may induce different globulins production, we hypothesize that SPEP can be used as an etiological diagnosis test. Retrospective study conducted from 1/1/13 until 5/1/15 among patient hospitalized for an acute community-acquired pneumonia based on fever, crackles and radiological abnormalities. α/β, α/γ, β/γ globulins and albumin/globulin (A/G) ratio were calculated from SPEP. Data were analyzed in 3 groups: documented viral (DVP) or bacterial pneumonia (DBP) and supposedly bacterial pneumonia (SBP). We used ANOVA statistic test with multiple comparisons using CI95 and ROC curve to compare them. 109 patients included divided into DBP (n = 16), DVP (n = 26) and SBP (n = 67). Mean age was 62 ± 18 year-old with a sex ratio M/F of 1.3. Underlying conditions (e.g. COPD, diabetes) were comparable between groups in multivariate analysis. Means of A/G ratio were 0.80 [0.76-0.84], 0.96 [0.91-1.01], 1.08 [0.99-1.16] respectively for DBP, SBP and DVP (p = 0.0002). A/G ratio cut-off value of 0.845 has a sensitivity of 87.5 % and a specificity of 73.1 %. A/G ratio seems to be an easy diagnostic tool to differentiate bacterial from viral pneumonia. A/G ratio cut-off value below 0.845 seems to be predictable of a bacterial origin and support the use of antibiotics.

[A bilateral and symmetric anatomic variation of a lombrical muscle causing a trigger finger]

Trigger finger is a very common disease. The vast majority of trigger fingers are primary idiopathic trigger fingers. We report the case of a bilateral and symmetric triggering of the fifth finger secondary to an anatomical variation of the lumbrical muscle. This lumbrical muscle arose from the flexor digitorum superficialis instead of the flexor digitorum profundus as is usual. To our knowledge, this is the third published case of trigger finger caused by an anatomical abnormality of a lumbrical muscle.

[Scaphotriquetral capsulodesis for scapholunate instability]

OBJECTIVES

Scapholunate ligament injuries may lead to scapholunate instability and wrist osteoarthritis. Many surgical techniques have been described to repair these injuries. The goal of our study is to assess the clinical results after capsulodesis with the scaphotriquetral ligament for scapholunate instabilities.

METHODS

Twenty-eight patients, 22 men and six women, were operated for scapholunate instability between January 2006 and December 2008. The average age was 37.8 years, and the average time between trauma and surgery was 9.9 months. The scaphoid shift test was present in 26 patients. All patients underwent static and dynamic X-rays of the wrist and scan. A capsulodesis with scaphotriquetral ligament was performed in all patients.

RESULTS

At 24 months follow-up, a 13° significant decreased of wrist range-of-motion was noted. The strength was significantly improved after surgery. The wrist stability was improved in 26 patients. Concerning pain, a significant reduction was noted with Analogical Visual Scale after surgery (p<0.005). Twenty-one patients returned to their previous work. Complications were reflex dystrophy in one patient and wrist infection in one patient.

CONCLUSION

Many techniques were described for treatment of scapholunate injuries, from the simple scapholunate ligament suture to partial wrist arthrodesis. Capsulodesis with scaphotriquetral ligament improves grip strength, decreases wrist instability and pain with a slight lost of range-of-motion.

Data acquisition system using six degree-of-freedom inertia sensor and ZigBee wireless link for fall detection and prevention

Fall detection and prevention require logged physiological activity data of a patient for a long period of time. This work develops a data acquisition system to collect motion data from multiple patients and store in a data base. A wireless sensor network is built using high precision inertia sensors and low power Zigbee wireless transceivers. Testing results prove the system function properly. Researchers and physicians can now retrieve and analyze the accurate data of the patient movement with ease.

Efficacy of a long-term antibiotic treatment in patients with a chronic Tick Associated Poly-organic Syndrome (TAPOS)

SETTINGS

Despite a now codified antibiotic treatment for Lyme disease, a significant proportion of patients treated according to recommendations complain of persistent signs and symptoms. The pathophysiological mechanisms which underlie this syndrome of post-treatment chronic systemic illness remain unclear. For some physicians post-treatment symptoms indicate a persistent infection requiring prolonged antibiotic therapy. For others, there is no benefit from antimicrobial therapy. The difficulty of assessment encountered in studies is significant because many symptoms are subjective. We think that the term "chronic Lyme disease" is not appropriate and should be replaced by chronic "tick associated poly-organic syndrome" (TAPOS).

OBJECTIVE

This open-label prospective study was made on a group of 100 patients having followed a medical treatment for a chronic TAPOS and to evaluate their evolution under prolonged antibiotic treatment.

RESULTS

The medical management was found to be effective for symptoms, especially for patients with a high probability of chronic TAPOS (NEJM score). Patients with post tick-bite symptoms, which often worsens their quality of life, deserve particular attention.

CONCLUSION

This study had methodological limitations but could help in terms of feasibility, choice of inclusion criteria, and design of follow-up for a future randomized, double blind study to test for an optimal management of TAPOS.

[Results of a prospective standardized study of 30 patients with chronic neurological and cognitive disorders after tick bites]

OBJECTIVE

Patients with chronic neurological disorders and cognitive impairment after tick bites are difficult to manage despite standard antibiotic therapy for Lyme disease. We wanted to correctly assess the disorders.

METHODS

Thirty patients were hospitalized for a standardized evaluation of their disorders: clinical examination, biological and serological studies, cerebral MRI, CSF study, neurophysiological exams, and neuropsychological evaluation of cognitive functions.

RESULTS

Clinical and biological results were non informative. We observed significant CSF abnormalities (64%), MRI Flair pictures (41%), neurophysiological exams (47%), and cognitive evaluation (100%).

CONCLUSIONS

A large and standardized evaluation should be made for each patient to improve the management and probably the treatment of these complex chronic symptoms observed after tick bites.

[Antiretroviral therapy in critically ill patients: a French national study]

SETTINGS

The HIV-positive population is still increasing because the incidence of the disease remains high while the effectiveness of highly active antiretroviral therapy (HAART) has dramatically reduced mortality. HIV infected patients have an increased life expectancy and are more readily admitted to intensive care units.

METHOD

We conducted a nation-wide comparative study in France of how these patients are managed by ICU specialists, on one hand, and HIV specialists, on the other, to better understand the use of antiretroviral therapy in critically ill patients.

RESULTS

The results show heterogeneous responses of ICU specialists with an important proportion of non decisive answers. The answers of HIV specialists are more homogeneous. There appears to be little or no cooperation between the two specialties. The CISIH (French centers for the information and care of human immunodeficiency) are rarely consulted.

CONCLUSIONS

ICU specialists must be better informed on this rapidly evolving disease. Access to updated information or to an HIV specialists must be made easier. Studies should also be made on how HAART is employed in ICUs (pharmacology, pharmacodynamics...).

[A new cause for iatrogenic lesion of the ulnar nerve at the arm: contraceptive hormonal implant. Report of two cases]

The authors describe two cases of iatrogenic lesions of the ulnar nerve at the arm level after insertion of contraceptive hormonal implants. The presence of only a thin subcutaneous fat layer on the medial side of the arm in slim women, exposes the ulnar nerve to danger during the insertion or withdrawal of the implant. We therefore advise the insertion of such implants on the medial side of the thigh in slim women. We equally recommend that withdrawal of non-tangible devices implanted on the medial side of the arm or in case of neurologic symptoms, even transitory, be done by a trained microsurgeon.

[The VB system: a new modular osteosynthesis material involving both screws and wires]

VB is an osteosynthesis system for the stabilisation of small fragments, which combines the benefits of both wires and screws. It is a modular system comprising a threaded pin and a ring. The threaded pin is first positioned. Then a ring is grasped and opened by the progressive angulation of a screwdriver. Still anchored on the screwdriver, the ring slides easily on the pin. It is clamped on the pin by simply removing the screwdriver and the pin is then cut. This modular system includes 1.8 and 1.1 mm pins and different types of rings (threaded or non threaded, with or without collars). The system is easy to handle and can be introduced using an open or percutaneous technique, allowing compression or distraction. Our preliminary series, performed in accordance with National clinical trial protocol (Huriet) consisted of 50 cases in 24 patients (five women and 19 men) with an average age of 48 years, and a follow-up of more than six months. Fourteen cases of fractures (28 implants) were treated as emergencies (two radial heads, one capitellum, one trochlea of the humerus, seven distal radius fractures, one trapezium, two metacarpals) and 12 cases (22 implants) were elective cases: arthrodesis (one trapezo-metacarpal, one intermetacarpal, two interphalangeal, two carpal), non-union (six scaphoids, one phalangeal) and one phalangeal malunion. Hardware removal was performed in 16 cases. No implant failure has been detected. One case, a DIP arthrodesis, had a suspicion of sepsis which led to the removal of the implants at six weeks. The results of this study have convinced us of the merits of the system, which combines the advantages of both wires and screws. The system allows the user to perform either distraction or compression, and to adjust the force by hand. Compared to the fixed amount of compression produced by lag screws, this feature seems to be a real step forward.

[The DASH questionnaire. French translation of a trans-cultural adaptation]

The DASH (Disability of Arm-Shoulder-Hand) is a self-administered questionnaire developed in 1994 by representatives of the Institute for Work & Health (IWH) and the American Academy of Orthopaedic Surgeons (AAOS). It measures the physical disability and symptoms for all upper limb disorders in a heterogeneous population and for acute as well as chronic disorders. The original american version has been already tested for reliability and validity. Interest in the DASH was raised by several European publications. It appeared that the DASH could provide a common measure for upper extremity physical disability in Northern America and European countries. For this cross-cultural adaptation, we followed the guidelines developed by the Institute for Work & Health and American Academy of Orthopaedic Surgeons. Five translations and two "back-translations" were compared, aiming to semantic, idiomatic, experimental and conceptual equivalence. The final version has been tested in 223 patients presenting a variety of traumatic or non traumatic disorders. 208 questionnaires (93%) were valid because there was less than 4 missing answers. This final version has been proposed to American Academy of Orthopaedic Surgeons in order to be endorsed as an official translation. This could improve assessment for international studies by establishing standard measures.

A 1000-fold overdose of clonidine caused by a compounding error in a 5-year-old child with attention-deficit/hyperactivity disorder

A 5-year-old child who weighed 17.5 kg received 50 mg of clonidine. The amount ingested was confirmed by analysis of the suspension administered (clonidine HCl 9.78 mg/mL). To our knowledge, this represents the largest ingestion in a child and the largest ingestion on a milligram per kilogram basis in the medical literature. The child's initial presentation included hyperventilation, an unusual feature of clonidine toxicity. The child was discharged without sequela 42 hours after admission. A serum concentration of clonidine 17 hours postingestion was 64 ng/mL, the highest reported to date in a pediatric patient. The intoxication was traced to a pharmacy compounding error in which milligrams were substituted for micrograms. Increased prescribing of clonidine in young children coupled with the requirement to compound clonidine in a suspension and the narrow therapeutic index suggests that the frequency of severe ingestions in children will increase in the future.

[Partial replantation following proximal limb injury]

PURPOSE OF THE STUDY

Proximal replantation is a technically feasible but life-threatening procedure. Indications must be restricted to patients in good condition with a good functional prognosis. The goal of replantation must be focused not only on reimplanting the amputated limb but also on achieving a good functional outcome. For the lower limb, simple terminalization remains the best choice in many cases. When a proximal amputation is not suitable for replantation, the main aim of the surgical procedure must be to reconstruct a stump long enough to permit fitting a prosthesis preserving the function of the adjacent joint. If the proximal stump beyond the last joint is very short, it may be possible to restore some length by partial replantation of spared tissues from the amputated part. We present here the results we obtained following this policy.

MATERIALS AND METHODS

This series included 16 cases of partial replantations, 14 involving the lower limb and 2 the upper limb. All were osteocutaneous microsurgical transfers. For the lower limb, all transfers recovered protective sensitivity following tibial nerve repair. The functional calcaeoplantar unit was used in 13 cases. The transfer of this specialized weight bearing tissue provided a stable distal surface making higher support unnecessary. In one case, we raised a 13-cm vascularized tibial segment covered with foot skin for additional length. For the upper limb, the osteocutaneous transfer, based on the radial artery, was not reinnervated, but this lack of sensitivity did not impair prosthesis fitting.

RESULTS

One vascular failure was finally amputated. This was the only unsuccessful result. For all other patients, the surgical procedure facilitated prosthesis fitting and preserved the proximal joint function despite an initially very proximal amputation.

DISCUSSION

The advantages of partial replantation are obvious compared with simple terminalization or secondary reconstruction. There is no secondary donor site and, because there is no major muscle mass in the distal fragment, the overall risk is very low compared with the risk of total proximal leg replantation.

Very distal finger amputations: replantation or "reposition-flap" repair?

Management of very distal finger amputations is still controversial. Successful replantation results in an almost normal finger but is not without problems, such as technical difficulty, risk of failure and cost. "Reposition-flap" repair is a simpler procedure: it consists of distal bone and nail bed "graft-reposition" and pulp reconstruction by a flap. We compare ten successful replantations and six reposition-flap reconstructions. Replantation has several advantages over reposition-flap repair in terms of less finger shortening, longitudinal nail curvature, absence of PIP flexion contracture and shorter time off work. The results of reposition-flap repair are less satisfactory, but it is nevertheless a useful alternative when replantation is impossible or has failed.

[Laparoscopic cholecystectomy in elderly patients. Apropos of 115 cases]

We report a retrospective analysis of 115 elderly patients over 70 years of age who underwent laparoscopic cholecystectomy for symptomatic lithiasis between January 1990 and January 1996. This technique is perfectly adapted to elderly patients. Complications are less frequent and better tolerated than for conventional open surgery. In this series, the success rate was 97.39% with technique-related complications at 2.7%. None of these complications required reoperation.

[Cancellous grafting to the fibula in the treatment of type III open fractures]

An alternative to the preceding treatments is to put cancellous graft onto the fibula (14 cases). The first stage is excision and fixation by external fixator and the second stage is filling the tibial/fibula interspace with cancellous graft. The indications for this technique are limited by the quantity of cancellous bone available in the iliac crests and thus a fairly short bony defect, the presence of skin loss over the bony defect and the absence of major vascular lesions. In spite of not using flaps for skin cover healing occurred on average 7.9 months after carrying out several repeated bone grafts and skin grafting.

On the functional overlap between two Drosophila POU homeo domain genes and the cell fate specification of a CNS neural precursor

The approximately 200 distinct neurons comprising each hemisegment of the Drosophila embryonic CNS are derived from a stereotypic array of approximately 30 progenitor stem cells, called neuroblasts (NBs). Each NB undergoes repeated asymmetric divisions to produce several smaller ganglion mother cells (GMCs), each of which, in turn, divides to produce two neurons and/or glia cells. To understand the process by which cell type diversity is generated in the CNS, we are focusing on identifying genes that affect cell identity in the NB4-2 lineage from which the RP2 motoneuron is derived. We show here that within the early part of the NB4-2 lineage, two closely linked and structurally related POU homeo domain genes, pdm-2 (dPOU28) and pdm-1 (dPOU19), both encode proteins that accumulate to high levels only in the first GMC (GMC4-2a) and not in its progeny, the RP2 motoneuron. Our results from the genetic and developmental analysis of pdm-1 and pdm-2 demonstrate that these genes are not required for the birth of GMC4-2a; however, they are both involved in specifying the identity of GMC4-2a and, ultimately, in the genesis of RP2 neurons, with pdm-2 being the more dominant player in this process. In mutant animals where both pdm-1 and pdm-2 functions are removed, GMC4-2a fails to express markers consistent with a GMC4-2a identity and no mature (Eve protein expressing) RP2 neurons are produced. We demonstrate that in some mutant combinations in which no mature RP2 neurons are produced, some GMC4-2a cells can nevertheless divide. Hence, the failure of the POU mutants to produce mature RP2 neurons is not attributable to a block in GMC4-2a cell division per se but, rather, because the GMC4-2a cells fail to acquire their correct cellular identity.