Prevalence and risk factors for secondary hyperparathyroidism (SHPT) in patients undergoing bariatric surgery

INTRODUCTION

Secondary hyperparathyroidism (SHPT) after bariatric surgery has significant adverse implications for bone metabolism, increasing the risk for osteoporosis and fracture. Our aim was to characterize prevalence and identify risk factors for SHPT in bariatric surgery patients.

METHODS

We performed a single-institution, retrospective chart review of patients who underwent bariatric surgery from June 2017 through December 2021. Demographic and clinical data were collected, including serum parathyroid hormone, calcium, and vitamin D3 at enrollment and 3, 6, and 12-months postoperatively. Chi-square or Fisher's exact tests were used to analyze categorical data and Mann-Whitney U test for continuous data. Multivariable analysis using binomial logistic regression assessed risk factors for SHPT. P-values ≤ 0.05 were considered significant.

RESULTS

350 patients were analyzed. SHPT prevalence at any time point was 72.9%. 65.8% had SHPT at enrollment; 45.9% resolved with intensive vitamin supplementation; and 19.7% had recurrent SHPT. New-onset SHPT occurred in 8.6%. Persistent SHPT was present in 42.4% at 1-year. Baseline SHPT correlated with black race and T2DM. SHPT at any time point correlated with T2DM and higher baseline BMI. 1-year SHPT correlated with RYGB, depression, and longer time in program. SHPT was not correlated with %TBWL at any time point. In patients with SHPT, vitamin D3 deficiency prevalence was significantly higher at baseline (77.0%) compared to all post-bariatric time points (16.7%, 17.3%, and 23.1%; P < 0.0001).

CONCLUSIONS

SHPT is highly prevalent in patients with obesity seeking weight loss surgery. 42% had persistent SHPT at 1-year despite appropriate vitamin supplementation. Current vitamin D3 and calcium supplementation protocols may not effectively prevent SHPT in many post-bariatric patients. Low prevalence of concomitant vitamin D3 deficiency with SHPT after bariatric surgery suggests that there may be alternative mechanisms in this population. Further studies are needed to develop effective treatment strategies to mitigate the adverse effects of bariatric surgery on bone metabolism.

Complications of Hip Hemiarthroplasty

Hip hemiarthroplasty is a commonly performed orthopedic surgery, used to treat proximal femur fractures in the elderly population. Although hip hemiarthroplasty is frequently successful in addressing these injuries, complications can occur. Commonly seen complications include dislocation, periprosthetic fracture, acetabular erosion, and leg-length inequality. Less frequently seen complications include neurovascular injury and capsular interposition. This article presents a comprehensive review of the complications associated with the management of hip hemiarthroplasty. [Orthopedics. 2023;46(4):e199-e209.].

Spontaneous Diffuse Pyoderma Gangrenosum after Polytrauma and Orthopedic Fixation: A Case Report with Brief Review of Literature

Introduction

Pyoderma gangrenosum (PG) is a skin condition driven by neutrophil activation resulting in painful ulcers with undermining borders and surrounding erythema. This can be seen, although rarely, post-traumatically. It has been reported in the setting of orthopedic trauma with only 31 cases reported in English literature after orthopedic surgery.

Case Report

A 20-year-old Caucasian female presented with multisystem trauma and multiple orthopedic injuries following motor vehicle collision. After fixation of orthopedic injuries, within 1 week post-operatively, the patient began to show signs of wound breakdown characterized by apparent purulence and skin necrosis at surgical sites and subsequently at additional non-surgical sites on bilateral lower extremities. After the failure of aggressive debridement and negative cultures, skin biopsy revealed post-traumatic PG. After diagnosis and treatment with corticosteroid therapy, the patient promptly recovered with the resolution of systemic and musculoskeletal manifestations.

Conclusion

Post-traumatic PG should be considered a potential etiology in non-healing wounds with negative cultures. A low threshold for skin biopsy and interdisciplinary involvement should be maintained to expedite diagnosis and guide treatment.

A Multidisciplinary Approach to the Nonambulatory Bariatric Patient With Bilateral Knee Osteoarthritis

Obesity and lower-extremity arthritis are challenging problems to address as they are often mutually exacerbating. Due to the known perioperative risk of morbid obesity, the modality and timing of weight loss prior to arthroplasty is debated. We present a case of a 55-year-old nonambulatory female patient with an initial body mass index of 80.3 kg/m². This individual underwent a staged bariatric and joint replacement surgical pathway employing personnel of differing treatment disciplines. Our patient successfully lost a substantial amount of weight and has been able to ambulate, exercise, and engage in new, strenuous physical activities. In the care of the nonambulatory bariatric patient, employing a multidisciplinary treatment plan can produce successful results.

Subtrochanteric femur fractures: current review of management

Subtrochanteric (ST) femur fractures are proximal femur fractures, which are often difficult to manage effectively because of their deforming anatomical forces.

Operative management of ST fractures is the mainstay of treatment, with the two primary surgical implant options being intramedullary (IM) nails and extramedullary plates.

Of these, IM nails have a biologic and biomechanical superiority, and have become the gold standard for ST femur fractures.

The orthopaedic surgeon should become familiar and facile with several reduction techniques to create anatomical alignment in all unique ST fracture patterns.

This article presents a comprehensive and current review of the epidemiology, anatomy, biomechanics, clinical presentation, diagnosis, and management of subtrochanteric femur fractures.

Cite this article: EFORT Open Rev 2021;6:145-151. DOI: 10.1302/2058-5241.6.200048

A high oxfendazole dose to control porcine cysticercosis: pharmacokinetics and tissue residue profiles

Oxfendazole (OFZ) is efficacious for porcine cysticercosis at 30 mg/kg. OFZ is not registered to be used at this dose. The assessment of the OFZ and metabolites [(fenbendazole sulphone (FBZSO2), fenbendazole (FBZ)] plasma pharmacokinetic and tissue residue profiles after its oral administration to pigs and the withdrawal period for human consumption were reported. Forty-eight pigs allocated into two groups received OFZ (30 mg/kg) orally as a commercial (CF) or as experimental formulation (SMF). Samples (blood, muscle, liver, kidney and fat) were collected over 30 days post-treatment and analyzed by HPLC. OFZ was the main compound recovered in plasma, followed by FBZSO2 and low FBZ concentrations. OFZ AUC0-LOQ (209.9±33.9 μg·h/ml) and Cmax (5.40±0.65 μg/ml) parameters for the CF tended to be higher than those for the SMF (AUC0-LOQ: 159.4±18.3 μg h/ml, Cmax: 3.80±0.35 μg/ml). The highest total residue (OFZ+FBZSO2+FBZ) concentrations were quantified in liver, followed by kidney, muscle and fat tissue. FBZSO2 residue levels were the highest found in muscle (0.68±0.39 μg/g) and fat (0.69±0.39 μg/g). In liver and kidney the highest residues corresponded to FBZ (5.29±4.36 μg/g) and OFZ (2.86±0.75 μg/g), respectively. A withdrawal time of 17 days post-treatment was established before tissues are delivered for human consumption.

Campylobacter spp. contamination of chicken carcasses during processing in relation to flock colonisation

The presence and numbers of campylobacters on chicken carcasses from 26 slaughter groups, originating from 22 single-house flocks and processed in four UK plants, were studied in relation to the level of flock colonisation determined by examining the caecal contents of at least ten birds per group. The prevalence of campylobacters on carcasses from five campylobacter-negative flocks processed just after other negative flocks was low (</=30%). Campylobacters were isolated from 90 to 100% of carcasses from three flocks which were partly colonised, with 5, 5 and 30% of caecal contents positive, and which were processed after fully colonised flocks. All carcasses from the remaining fully colonised flocks were contaminated with campylobacters, and they had significantly (P<0.001) higher numbers per carcass (average of 5.3 log(10) cfu; range: 1.3 to >8.0 log(10) cfu) than carcasses originating from low prevalence flocks (average of 2.3 log(10) cfu; range: <1.1 to 4.1 log(10) cfu). There was a reduction in the numbers of campylobacters on carcasses between plucking and chilling in eight of ten fully colonised flocks. In another eight flocks, a significant (P<0.001) decrease (0.8 log(10) cfu) in the number of campylobacters on carcasses from just before to after chilling was detected. Campylobacter spp. could be isolated from aerosols, particles and droplets in considerable numbers in the hanging-on, defeathering and evisceration areas but not in the chillers. This was the case even when campylobacters were not isolated from the target flock. Campylobacters on carcasses from two partly colonised flocks were either the same subtype, as determined by speciation, Multi-Locus Sequence Typing (MLST) and flaA Restricted Fragment Length Polymorphism (RFLP) typing, as those in the fully colonised flocks processed previously, although not necessarily the most prevalent ones; or were the same subtypes as those found in the caeca of the flock itself. The prevalences of the different campylobacter subtypes found on carcasses from two fully colonised flocks did not closely reflect those found in the caeca. MLST combined with flaA RFLP provided a good method for ascertaining the relatedness of strains isolated from carcasses and caecal contents. This study showed that carcass contamination is related to the within-flock prevalence of campylobacter colonisation, but that contamination from previously processed flocks was also significant, especially on carcasses from low prevalence flocks. Forced dry air cooling of carcasses reduced contamination levels.

Sources of Campylobacter spp. colonizing housed broiler flocks during rearing

The study aimed to identify sources of campylobacter in 10 housed broiler flocks from three United Kingdom poultry companies. Samples from (i) the breeder flocks, which supplied the broilers, (ii) cleaned and disinfected houses prior to chick placement, (iii) the chickens, and (iv) the environments inside and outside the broiler houses during rearing were examined. Samples were collected at frequent intervals and examined for Campylobacter spp. Characterization of the isolates using multilocus sequence typing (MLST), serotyping, phage typing, and flaA restriction fragment length polymorphism typing was performed. Seven flocks became colonized during the growing period. Campylobacter spp. were detected in the environment surrounding the broiler house, prior to as well as during flock colonization, for six of these flocks. On two occasions, isolates detected in a puddle just prior to the birds being placed were indistinguishable from those colonizing the birds. Once flocks were colonized, indistinguishable strains of campylobacter were found in the feed and water and in the air of the broiler house. Campylobacter spp. were also detected in the air up to 30 m downstream of the broiler house, which raises the issue of the role of airborne transmission in the spread of campylobacter. At any time during rearing, broiler flocks were colonized by only one or two types determined by MLST but these changed, with some strains superseding others. In conclusion, the study provided strong evidence for the environment as a source of campylobacters colonizing housed broiler flocks. It also demonstrated colonization by successive campylobacter types determined by MLST during the life of a flock.

DNA-based subtyping of verocytotoxin-producing Escherichia coli (VTEC) O128ab:H2 strains from human and raw meat sources

AIMS

To investigate subtyping methods for verocytotoxin-producing Escherichia coli (VTEC) O128ab:H2.

METHODS AND RESULTS

Eleven human and food strains isolated over a 15-year period were examined. All were intimin (eae)-negative, but all possessed enterohaemolysin and VT1-encoding sequences which in nine strains were vtx1c variant. Ten strains had VT2 genes which were all vtx2d. Plasmid profiles and randomly amplified polymorphic DNA-PCR were not discriminatory. Long-PCR restriction fragment length polymorphism of amplicons bound by the p gene and the VT2A subunit had screening potential. Pulsed field gel electrophoresis (PFGE) using XbaI gave fine discrimination although VT2 sequences were located on a 220 kbp fragment conserved in nine strains and on a 200 kbp fragment in the 10th.

CONCLUSIONS

As a result of apparent clonality, PFGE proved essential for differentiation. Long-PCR has promise for screening but requires further evaluation of inter-strain variable sequences.

SIGNIFICANCE AND IMPACT OF THE STUDY

A combined phenotypic and genotypic screen, and PFGE for selected strains was effective.

Impact of transport crate reuse and of catching and processing on Campylobacter and Salmonella contamination of broiler chickens

The influence of transport, catching, and processing on contamination of broiler chickens with Salmonella and Campylobacter was investigated. Transport crates were reused with high frequency and were often still contaminated with Salmonella and Campylobacter when they arrived at the farm despite the fact that they were washed at the factory, and thus they were a potential route of infection. These organisms contaminated the feathers of previously Campylobacter- and Salmonella-negative birds going to the processing plant and were isolated from processed carcasses, albeit at a low frequency. The Campylobacter types which were the predominant organisms on the live birds when they arrived at the processing plant were not necessarily the types that were most frequently isolated from processed carcasses. This finding may reflect cross-contamination that occurred during processing or differences in the tolerance of the strains to the hostile environments that the bacteria experienced. The process of catching and putting the birds in crates significantly increased the chance of contamination with Campylobacter (P < 0.001).

Growth of Salmonella enteritidis in artificially contaminated eggs: the effects of inoculum size and suspending media

Growth profiles of two isolates of Salmonella enteritidis phage type (PT) 4 inoculated into either the albumen of whole shell eggs or into separated albumen were found to be markedly affected by the size of the inoculum and the composition of the medium used to suspend the cells prior to inoculation. Using our model with an inoculum of two cells, multiplication of the Salmonella was not seen in 93% of eggs held at 20 degrees C for 8 days. In approximately 7% of eggs, however, growth occurred during the 8 days of storage. If the inoculum equaled or exceeded 25 cells per egg when eggs were subsequently stored at 20 degrees C, or 250 cells per egg when eggs were stored at 30 degrees C, high levels of growth of Salmonella in the egg occurred significantly more frequently than when the inoculum was two cells. High levels of growth were also seen more frequently if the inoculum was suspended in buffered peptone water or maximal recovery diluent rather than in phosphate buffered saline. Growth of Salmonella in separated albumen occurred very infrequently (1.1% of samples) at low inoculum levels and did not become significant until the inoculum was 250 cells or greater. Growth in the albumen was unaffected by the composition of the suspending medium. Provided that the inoculum was approximately 2 cells per egg and the bacteria were suspended in PBS, observed growth profiles of S. enteritidis inoculated into the albumen of whole eggs resembled those in naturally contaminated eggs.

Changes in the carriage of Campylobacter strains by poultry carcasses during processing in abattoirs

The recent development of simple, rapid genotyping techniques for Campylobacter species has enabled investigation of the determinative epidemiology of these organisms in a variety of situations. In this study we have used the technique of fla typing (PCR-restriction fragment length polymorphism analysis of the flaA and flaB genes) to identify the sources of strains contaminating the carcasses of five campylobacter-positive and two campylobacter-negative broiler flocks during abattoir processing. The results confirmed that, in the United Kingdom, individual broiler flocks are colonized by a limited number of subtypes of Campylobacter jejuni or C. coli. In some but not all cases, the same subtypes, isolated from the ceca, contaminated the end product as observed in carcass washes. However, the culture methodology, i.e, use of direct plating or enrichment, affected this subtype distribution. Moreover, the number of isolates analyzed per sample was limited. fla typing also indicated that some campylobacter subtypes survive poultry processing better than others. The extent of resistance to the environmental stresses during processing varied between strains. The more robust subtypes appeared to contaminate the abattoir environment, surviving through carcass chilling, and even carrying over onto subsequent flocks. From these studies it is confirmed that some campylobacter-negative flocks reach the abattoir but the carcasses from such flocks are rapidly contaminated by various campylobacter subtypes during processing. However, only some of these contaminating subtypes appeared to survive processing. The sources of this contamination are not clear, but in both negative flocks, campylobacters of the same subtypes as those recovered from the carcasses were isolated from the crates used to transport the birds. In one case, this crate contamination was shown to be present before the birds were loaded.

Transmission of Vero cytotoxin producing Escherichia coli O157 infection from farm animals to humans in Cornwall and west Devon

A study of Vero cytotoxin producing Escherichia coli (VTEC) O157 infections in Cornwall and West Devon was conducted to identify associations between human infection and contact with farm animals. In three years from November 1994 to October 1997, 63,000 stool specimens were submitted to four participating microbiology laboratories and screened for E. coli O157. Sixty-nine confirmed cases were interviewed to assess the extent of any direct or indirect contact with farm animals. Nine out of 22 investigations conducted on farms--in which animal rectal swabs, faecal specimens, fore-stream milk samples (first draw-off from teats), and various environmental samples were tested--yielded VTEC O157. In seven incidents one or more isolates from animals were indistinguishable from the isolate(s) from the human case(s) using phenotypic and genotypic subtyping. Cases associated with animal contact included farm visitors, holidaymakers, and members of farming families and farm workers.

Bacterial doubling time modulates the effects of opsonisation and available iron upon interactions between Staphylococcus aureus and human neutrophils

Staphylococcus aureus was grown exponentially at two doubling times (DT), one related to in vivo (DT 60 min) and one typical of laboratory conditions (DT 24 min), and under iron-poor and iron-rich conditions. Relative to the fast-grown phenotypes, both slow-grown phenotypes exhibited low surface hydrophobicity and low protein A expression, induced poorly in non-opsonised and opsonised chemiluminescence, and survived well in whole blood killing. In particular, slow-grown, iron-poor cocci demonstrated enhanced survival in whole blood killing which correlated with significant reduction in their association with polymorphonuclear leukocytes, compared to the three other phenotypes; iron sufficiency increased the ability to stimulate polymorphonuclear leukocytes irrespective of opsonisation status. Staphylococcal DT may, by influencing surface hydrophobicity, modify interactions with immune system components.

Prevalence of antibiotic resistance and serotypes in pneumococci in England and Wales: results of observational surveys in 1990 and 1995

OBJECTIVE

To assess the prevalence of antibiotic resistance and serotype distribution among pneumococci in England and Wales in 1990 and 1995.

DESIGN

Observational surveys in March 1990 and March 1995. During two weeks in each survey period all pneumococci isolated in public health laboratories in England and Wales were collected and assessed for sensitivity to antibiotics and the distribution of serogroups or serotypes.

SETTING

The network of public health laboratories throughout England and Wales.

SUBJECTS

1127 individual patient isolates of Streptococcus pneumoniae obtained during the two surveys.

MAIN OUTCOME MEASURES

Sensitivity or resistance to a range of antibiotics; serogroup or serotype.

RESULTS

The prevalence of intermediate or full resistance to penicillin increased from 1.5% in 1990 to 3.9% in 1995 and resistance to erythromycin increased from 2.8% to 8.6%. About 92% of isolates belonged to serogroups or serotypes included in the currently available pneumococcal vaccine.

CONCLUSION

Resistance to penicillin and erythromycin has increased among pneumococci in England and Wales. Continued surveillance to assess further increases in the prevalence of pneumococcal resistance to antibiotics is essential.

Testing antimicrobial susceptibilities of adherent bacteria by a method that incorporates guidelines of the National Committee for Clinical Laboratory Standards

Membrane filters (0.22-microns pore size) were colonized with 10(4) CFU of logarithmic-phase bacteria per filter under laminar flow conditions in a Modified Robbins Device. Colonized filters were then placed upon agar dilution plates for MIC determinations. Subsequently, filters were transferred to control plates and incubated to obtain MBCs.

Immunology of pyelonephritis in the primate model. VI. Effect of complement depletion

The inflammatory response has been shown to be responsible for the renal damage from bacterial infection. Phagocytic events are responsible for damage to the host as well as the pathogen. In this study we evaluated the effect of complement depletion, in an attempt to decrease chemotaxis and opsonization and thus decrease phagocytosis. Acute renal damage was decreased from both a decrease in inflammatory cells and phagocytic events in the areas of bacterial inoculation.

Immunology of pyelonephritis in the primate model. V. Effect of superoxide dismutase

Ascending acute pyelonephritis was produced in monkeys by infusion of bacteria through a ureteral catheter to the point of intrarenal reflux. This led to a significant inflammatory response with death of renal tubular cells in the area of the tubular granulocytes and bacteria. We gave superoxide dismutase, and found that the inflammatory response was decreased and fewer tubular cells were killed. Ultrastructural change was also decreased in tubular cells adjoining phagocytosing neutrophils. This suggests that renal damage following a bacterial infection may be due to the production and release of superoxide into the tubular lumen during phagocytosis. We believe that it is the initial event which may lead to the eventual loss of renal tissue and function called chronic pyelonephritis.

Studies on sperm antigenicity, 5. In vivo and in vitro cellular reactivity in guinea pigs sensitized with fractions of human spermatozoa

In vitro delayed type hypersensitivity was demonstrated with peritoneal exudate cells from guinea pigs immunized with different preparations of human and guinea pig seminal components emulsified with complete Freund's adjuvant-H37Ra. The seminal components were intact human spermatozoa (HuSp); intact guinea pig spermatozoa (GPSp); human seminal plasma (HuSePlFr); and fractions of human spermatozoa obtained by centrifugation of the homogenate at 5,000 X g (5S30 and 5p30), at 20,000 X g (20S30 and 20p30), and at 144,000 X g (144p120). Cellular sensitivity was demonstrated in vivo by skin testing and in vitro by the macrophage inhibition technique. Peritoneal exudate cells from guinea pigs sensitized with fractions 5p30 and 20p30 elicited a delayed hypersensitivity reaction which could be detected only with intact human spermatozoa. Other human spermatozoal fractions (5S30, 20S30, and 144p120) were weak immunogens. Sensitization of guinea pigs with fractions of human spermatozoa, in addition to causing delayed hypersensitivity reactions, elicited low titers of spermatoxic antibodies. Antibodies to human spermatozoal fractions 5S30, 5p30, 20S30, and 20p30 cross-reacted with intact human spermatozoa and intact guinea pig spermatozoa. It is postulated that the existence of "spermatozoa-specific" coating antigen(s) derived from other components of the reproductive tract might be responsible for human spermatozoal antigenicity.

Demonstration of the phenomena of microbial persistence and reversion with bacterial L-forms in human embryonic kidney cells

A series of experiments was undertaken in which human embryonic kidney (HEK) fibroblasts were infected with either relatively stable or stable L-forms of Streptococcus faecalis. The infected cells were maintained by splitting over long periods (1 to 2 months) while samples were withdrawn for culture and electron microscopic studies. Relatively stable S. faecalis L-forms could be cultured from infected cells only during the first week after infection, although L-form-like material was frequently detected at later periods by electron microscopy. HEK cells continued to proliferate and showed no gross histopathology until reversion occurred. At reversion, electron microscopy revealed the presence of intracellular L-forms, transitional variants, and intra- and extracellular bacterial forms. Unlike relatively stable L-forms, stable L-forms were culturable throughout the experimental period. These experiments demonstrate the phenomena of persistence and reversion in vitro. Electron microscopy indicated that the L-forms entered the HEK cells, where they underwent morphological changes. Observations suggested that these altered L-forms (elementary bodies) persisted in the cell until reversion to the parent bacterial form was triggered. Infected cells, when treated with L-form antiserum and stained with fluorescein-conjugated goat anti-rabbit serum, were consistently positive regardless of cultural findings.

Proposed reproductive cycle for a relatively stable L-phase variant of Streptococcus faecalis

Based on electron microscopic observations, the reproductive cycle of a relatively stable L-phase variant of Streptococcus faecalis was proposed. The small, dense, nonvesiculated L-form is envisioned as the central (core) element. It was seen to divide and bud rapidly. In addition, the dense forms appeared to be capable of growth and development within vesicles of mature mother forms. When these forms were released from the vesicles into the surrounding fluid medium, further growth occurred, resulting in the development of immature and ultimately mature mother forms. Under conditions unfavorable for L-form growth, these dense forms developed first into transitional forms and then into the bacterial form. These dense forms might therefore be considered as undifferentiated "stem cells' with the capacity to develop along several different routes, depending upon the stimulus received.

Prevention of Experimental Hematogenous and Retrograde Pyelonephritis by Antibodies Against Enterobacterial Common Antigen

Rabbits were immunized with common antigen (CA) derived from Salmonella typhimurium . Animals with CA hemagglutinin titers of 1-320 to 1-81,920 were injected with 10 7 viable Proteus mirabilis via the retrograde and hematogenous routes. Nonimmune control groups were challenged similarly. From the retrogradely challenged groups sacrificed at 4 weeks, pyelonephritis was found in 89% of the control animals but not in those immunized. Bacteriuria was present in 89% of the controls but in only 61% of the immunized group. Hematogenously challenged, immune animals sacrificed at 6 weeks did not show histological evidence of renal pathology, and only 6% had bacteriuria. Eighty-six per cent of the nonimmune controls showed both pyelonephritis and bacteriuria. The protective effect is specific because of the following. (i) Active and passive CA immunization did not prevent pyelonephritis due to Pseudomonas aeruginosa which does not produce this antigen. (ii) Passive immunization with a CA antiserum conferred protection against a P. mirabilis challenge. (iii) Passive administration of an antiserum from which CA antibodies had been differentially absorbed abolished the protective activity.

The plaque test for the demonstration of antibodies against the enterobacterial common antigen produced by spleen and lymph node cells

The observations that enteric bacteria other than Escherichia coli O14, although containing a common antigen (CA), failed to give rise to the corresponding antibodies upon intravenous injection in rabbits and that the O antigen (endotoxin, lipopolysaccharide) was responsible for this suppression prompted the study of CA antibody forming cells in spleen and lymph nodes by means of the haemolytic plaque technique of Jerne. It was shown that intravenous injection of supernates of Salmonella typhimurium, containing both CA and O antigen, does not result in an increase in the number of splenic cells producing antibodies against CA. In contrast, injection of partially purified CA (ethanol soluble fraction), which contains only traces of the O antigen, leads to a marked increase in the number of CA antibody forming cells. The largest number of CA antibody forming cells was present in rabbits injected first with a mixture of CA and O antigen for priming and then with small amounts of CA for booster purposes. Administration into one footpad of CA resulted in a substantial increase in antibody forming cells in the corresponding lymph node and only a small increase in those of the contralateral lymph node.