Assessment of fetal renal reserve in low level obstructive uropathy

Systematic review of accuracy of fetal urine analysis to predict poor postnatal renal function in cases of congenital urinary tract obstruction

OBJECTIVE

To evaluate the clinical usefulness of analysis of fetal urine in the prediction of poor postnatal renal function in cases of congenital urinary tract obstruction.

METHODS

A systematic review was performed. We conducted extensive electronic searches (database inception-2006). The reference lists of articles obtained were searched for any further articles. Two reviewers independently selected the articles in which the accuracy of fetal urinalysis was evaluated to predict poor postnatal renal function. There were no language restrictions. Data were extracted on study characteristics, quality and results, to construct 2 x 2 tables. Likelihood ratios for positive (LR+) and negative (LR-) test results were generated for the different fetal urinary analytes at various thresholds.

RESULTS

There were 23 articles that met the selection criteria, including a total of 572 women and 63 2 x 2 tables. The two most accurate tests were calcium > 95th centile for gestation (LR + 6.65, 0.23-190.96; LR - 0.19, 0.05-0.74) and sodium > 95th centile for gestation (LR + 4.46, 1.71-11.6; LR - 0.39, 0.17-0.88). beta(2)-microglobulin was found to be less accurate (LR + 2.92, 1.28-6.69; LR - 0.53, 0.24-1.17).

CONCLUSION

The current evidence demonstrates that none of the analytes of fetal urine investigated so far can be shown to yield clinically significant accuracy to predict poor postnatal renal function.

Syndrome d’insuffisance rénale fœtale

Some anomalies of the kidney and urinary tract evolving in utero may compromise the renal function in the newborn. Early therapeutic options do exist, especially in obstructive nephropathies. The decision depends on a correct evaluation of the foetal enal function and prognosis, which is based on a range of methods: ultrasound echography, biochemical analysis of foetal urine, and, more recently, foetal serum markers such a beta-2 micro globulin. These methods are reviewed.

Invasive assessment of fetal renal abnormalities: urinalysis, fetal blood sampling and biopsy

There are a number of potential biochemical markers that may have some role in predicting renal function postnatally. These include urinary sodium, calcium and beta2-microglobulin. The latter may also be measured in fetal serum. However, the accuracy of these parameters at a point in time is far from perfect as urinary tract obstruction is a progressive disease which may be best defined by repeated observations throughout pregnancy.

Fetal renal biopsies in obstructive uropathy: feasibility and clinical correlations--preliminary results

Final assessment on the outcome of fetal obstructive uropathy is a challenging matter. Ultrasonography, fetal urine electrolytes, and beta 2 microglobulin are postulated as being useful in many cases. For cases in which renal function remains unclear, ultrasound-guided fetal kidney biopsy may be used in order to detect histologic features distinctive of renal dysplasia. We present preliminary results aimed at studying the feasibility and possible risks. Biopsies were initially performed in 11 severely malformed fetuses, three of them with associated renal abnormalities. The success rate in obtaining renal material was 63.6 per cent with no maternal complications. In the next phase of this study, ten biopsies and urine collections were performed in fetuses with bilateral obstructive uropathy. The success rate was 50 per cent with no complications. Normal fetal renal histology was seen in 80 per cent of cases. In one case, although electrolytes were normal, a histologic diagnosis of renal dysplasia was made, showing a good correlation with outcome. In conclusion, fetal kidney biopsies for obstructive uropathy are feasible and further studies are needed to show their clinical relevance and risks.

Serum beta 2-microglobulin in fetuses with urinary tract anomalies

OBJECTIVE

Our purpose was to establish a reference range of fetal serum beta 2-microglobulin, an index of glomerular filtration rate, and to compare the values obtained in fetuses with urinary tract anomalies with this range.

STUDY DESIGN

Serum beta 2-microglobulin was measured in 53 control fetuses at 18 to 39 weeks' gestation and in 14 fetuses with urinary tract anomalies, 9 of which had simultaneous urine sampling.

RESULTS

In controls fetal serum beta 2-microglobulin had a mean value of 3.4 mg/L (95% data intervals 2.0 to 4.9) and did not correlate with gestational age. In the 14 fetuses with urinary tract anomalies beta 2-microglobulin levels were increased overall compared with controls (median Z score 1.7, range -0.1 to 9.2), and this was also the case in the five fetuses with unilateral renal disorders (median Z score 1.7, range -0.1 to 3.8) and in a fetus who underwent vesicoamniotic shunting and had normal renal function at birth. Serum beta 2-microglobulin was normal in 4 fetuses with bilateral urinary tract obstruction and normal function at postnatal follow-up and also in 1 of 5 fetuses with renal failure. In fetuses with bilateral uropathy urinary sodium correlated with serum beta 2-microglobulin levels.

CONCLUSIONS

Increased values of serum beta 2-microglobulin in fetuses with urinary tract anomalies indicate an impaired glomerular filtration rate. The finding of raised concentrations in fetuses with unilateral damage suggests that the compensatory role of the normal kidney is not complete during intrauterine life. Larger series are required to ascertain whether fetal blood sampling is warranted in the antenatal investigation of renal function, especially in view of the close correlation between urinary sodium and serum beta 2-microglobulin levels in fetuses with bilateral obstruction.

In fetuses with isolated hydronephrosis, urinary beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase (NAG) have a limited role in the prediction of postnatal renal function

Seventy-one fetal urine samples were taken from the bladder or renal pelvis of 33 fetuses at 13-36 weeks' gestation with a diagnosis of urinary tract anomaly. Severe isolated hydronephrosis in the absence of an enlarged bladder was the indication for sampling in 12/33 fetuses (26 samples), who were retrospectively classified into three groups: normal, intermediate, and dysplastic, based on the evaluation of postnatal renal function or histology. For all samples, urinary sodium (Na+), calcium (Ca2+), creatinine, beta 2-microglobulin, and N-acetyl-beta-D-glucosaminidase (NAG) were measured. Among the 71 fetal urine samples, both beta 2-microglobulin and NAG correlated inversely with gestational age, Na+, and Ca2+, but not with creatinine concentrations. However, the correlation of urinary beta 2-microglobulin with gestational age was dependent on the Na+ and Ca2+ concentrations, whereas urinary NAG correlated significantly with urinary Na+ and Ca2+, and also with gestational age. In fetuses with isolated hydronephrosis, only Na+, and not Ca2+, was significantly related to both beta 2-microglobulin and NAG. Only Na+ and beta 2-microglobulin were significantly, and similarly, higher in both dysplastic and intermediate kidneys when compared with fetuses with normal postnatal function. If only the last urine sampled was considered, there was overlapping of all parameters in the three groups. In isolated hydronephrosis, only the most extreme forms of renal failure might be suggested by elevated levels of Na+, Ca2+, beta 2-microglobulin, and NAG, without an obvious superiority of any of these parameters.

Shortcomings in predicting postnatal renal function using prenatal urine biochemistry in fetuses with congenital hydronephrosis

Ten fetuses with hydronephrosis underwent one to seven urine sampling procedures at 23 to 36 weeks' gestation to evaluate renal function. Postnatally, the infants' renal function was assessed by a combination of serum creatinine measurement, ultrasonography and renal scintigraphy. Six infants had pyelo-ureteric junction obstruction, two had megabladder with megaureter, and two had vesico-ureteric reflux. All infants had normal serum creatinine levels at the time of postnatal follow-up, but five of the seven with unilateral involvement had moderate or severe renal damage. Abnormal urinary electrolyte concentrations were found antenatally in only two of them. For the three infants with bilateral hydronephrosis, postnatal evaluation showed moderately or severely damaged kidneys despite prenatal evidence of normal biochemical indexes. Fetal urine electrolyte measurement may be accurate in the diagnosis of renal dysplasia, but its sensitivity is poor in predicting moderate renal dysfunction.

Fetal urinary insulin-like growth factor I and binding protein 3 in bilateral obstructive uropathies

Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 mumol/l at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat < or = mumol/l. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18,159 +/- 9083 pg/ml; 2657 +/- 669 ng/ml) and 2 (1574 +/- 847 pg/ml; 176 +/- 50 ng/ml) in comparison with group 3 (35 +/- 6 pg/ml; 21 +/- 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (> 50 mumol/l). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment.

Sequential urinalysis improves evaluation of fetal renal function in obstructive uropathy

OBJECTIVES

The purpose of our study was to determine whether sequential vesicocenteses improve the evaluation of renal damage, compared with single urine sampling in obstructive uropathy.

STUDY DESIGN

A total of 29 fetuses with complete obstructive uropathy underwent a minimum of three sequential complete vesicocenteses at 48- to 72-hour intervals. First and last urine values were analyzed for multiple parameters. The ability of first versus last urine values to detect the presence of renal damage was compared according to postnatal or fetal autopsy information.

RESULTS

Fetuses with minimal renal damage had patterns of decreasing hypertonicity and last urine values below cutoff thresholds indicative of favorable prognosis. Fetuses with significant renal damage had higher initial values and patterns of increasing hypertonicity. For five of six parameters, last urine samples were more predictive of renal damage than first urine samples.

CONCLUSION

Last urine values together with pattern-of-change trend analysis after serial vesicocenteses improve diagnostic precision in fetuses with complete obstructive uropathy.

Contamination of hands and work surfaces with Salmonella enteritidis PT4 during the preparation of egg dishes

Salmonella enteritidis PT4 was recovered from fingers following the breaking of intact shell eggs artificially contaminated in the contents with the bacterium. Kitchen utensils used to mix egg dishes were salmonella-positive, sometimes after washing. Following the preparation of batter or the mixing of eggs, S. enteritidis was recovered from work surfaces over 40 cm from the mixing bowl. The bacterium survived well in thin, dry films of either batter or egg and, from an initial level of one cell per cm2, could be recovered from formica work surfaces 24 h after contamination.

The role of home-made ice cream as a vehicle of Salmonella enteritidis phage type 4 infection from fresh shell eggs

A family outbreak of Salmonella enteritidis PT4 infection is described in which home-made ice cream was identified as the vehicle of infection. The ice cream contained approximately 10(5) S. enteritidis PT4 organisms per gm and was probably contaminated by an infected shell egg containing between 10(5)-10(8) organisms. The continued relevance of the Chief Medical Officer's warning on the use of raw shell eggs is highlighted. Home-made ice cream using the same recipe as ice cream that had been incriminated as the cause of the family outbreak of S. enteritidis PT4 infection was used to study the growth of the organism that might have occurred in the 3-4 h it took to prepare the product. When the inoculum was in the stationary phase, as it would be from shell or other cross contamination, there was a lag phase of 3 h before growth occurred at room temperature. Even when actively multiplying organisms were introduced, as may be found in an infected egg, there was less than 3 log(10) increase in the salmonella count in 4 h at room temperature. It was, therefore, given the high S. enteritidis count, unlikely that the ice cream was cross-contaminated. By contrast, raspberry sorbet at pH 3.73 proved to be lethal to a large inoculum of S. enteritidis and may be a relatively safe raw egg containing product.

In utero surgical treatment of fetal obstructive uropathy: a new comprehensive approach to identify appropriate candidates for vesicoamniotic shunt therapy

OBJECTIVES

We present a new approach to prenatal evaluation and prediction of renal function and long-term outcomes for fetuses considered candidates for in utero surgery.

STUDY DESIGN

A review of 34 cases of obstructive uropathies was made, with analysis of our approach to prenatal evaluation, the predictive value of urinary electrolytes and protein analysis in identifying renal dysplasia, and the outcomes of cases with and without in utero surgical intervention.

RESULTS

Ten of 11 pregnancies that were terminated had dysplasia; one female had cloacal dysgenesis. In three of eight unshunted cases megacystis resolved after vesicocentesis. Eight of 15 shunted fetuses survived. Of those predicted to have good postnatal outcome, six of six demonstrated good postnatal renal function. Of those predicted to have poor outcomes, two of two had poor postnatal renal function and dysplasia. Seven of 15 shunted fetuses died, four of four predicted to have dysplasia were confirmed, and three died of nonrenal causes.

CONCLUSIONS

Our prenatal approach successfully differentiated fetuses with underlying renal dysplasia from those without irreversible damage who subsequently benefited from in utero vesicoamniotic shunt placement.

Egg age and the growth of Salmonella enteritidis PT4 in egg contents

The growth of Salmonella enteritidis PT4 in albumen around an intact yolk was governed by the age of the egg on inoculation. In the majority of eggs, held at 20 degrees C, the bacterium was unable to grow rapidly until eggs had been stored for approximately 3 weeks. The multiplication of S. enteritidis in stored eggs appeared to be associated with alterations to the yolk membrane which allowed the bacterium to either invade the yolk or obtain nutrients from it. The rate at which egg contents change to permit the growth of S. enteritidis would appear to be temperature related and took place more rapidly when eggs were stored under conditions where temperatures fluctuated and, on occasions, reached 30 degrees C.

Fetal urine analysis for the assessment of renal function in obstructive uropathy

OBJECTIVES

The assessment of fetal renal function plays a key role in the evaluation of posterior urethral valve obstruction cases. The aim of our study was to determine the value of several urinary compounds, including beta 2-microglobulin, N-acetyl-beta-D-glucosaminidase, and microalbumin in the assessment of prenatal renal function in cases of posterior urethral valve and their potential role in the selection of such cases for in utero shunting.

STUDY DESIGN

A range of urinary compounds was measured, including beta 2-microglobulin, N-acetyl-beta-D-glucosaminidase, and microalbumin in 25 cases of posterior urethral valve obstruction. These cases were divided into four groups based on outcome. The Mann-Whitney test and analysis of covariance were used.

RESULTS

Sodium, calcium, and beta 2-microglobulin were the best predictors for fetal survival. beta 2-Microglobulin values > 13 mg/L were almost invariably associated with fatal outcome.

CONCLUSION

The estimation of beta 2-microglobulin may help in counseling parents and in selecting cases for in utero shunting.

An investigation into an outbreak of Salmonella enteritidis phage-type 4 infection and the consumption of custard slices and trifles

Epidemiological investigation into an outbreak of food poisoning in 17 patients caused by Salmonella enteritidis phage-type 4 demonstrated a highly significant association with consumption of custard, retailed in custard slices and trifles from a bakery on one day. The bakery had changed their recipe for custard 2 weeks earlier to include fresh shell eggs and had not followed earlier national advice on cooking eggs for human consumption. The case-control study supports earlier work associating Salmonella enteritidis phage-type 4 infection with consumption of uncooked or lightly cooked shell eggs.

The identification of Salmonella enteritidis-infected poultry flocks associated with an outbreak of human salmonellosis

In the summer of 1991 a human outbreak of Salmonella enteritidis infection occurred following a barbecue in which about 100 persons were involved. Eggs, supplied by one or more of 10 different layer farms, were the most probable source of the infection. To identify the S. enteritidis-positive flocks, an immunoassay was used to detect salmonella serogroup D-specific antibodies in the yolk of hens eggs. Antibody titres in the eggs from two layer farms, farm A and B, clearly exceeded the titres found in randomly collected eggs. Further investigation on farm A and B yielded high antibody titres in the eggs from flocks A1, A2 and B2, and low titres in the eggs from flock B1. S. enteritidis was isolated from the faecal samples of flocks A1, A2 and B2, whereas no salmonella was detected in the faecal samples of flock B1. The flocks present on both farms originated from the same breeder flock.

Cystic lesions of the fetal kidney: diagnosis and prediction of postnatal function by fetal urine biochemistry

Fetal urine was aspirated under ultrasound control from 21 large cystic renal masses in 18 pregnancies of 20 to 35 weeks gestation. None were associated with bladder or ureteric dilatation. At postnatal investigation, 12 kidneys were demonstrated to be hydronephrotic (5 with no or poor function) and 9 multicystic. Urinary concentrations of sodium (Na+), calcium (Ca++), and phosphate (PO4--) were significantly higher in the multicystic group than in the hydronephrotic, whereas urea and creatinine levels were lower. Determination of urinary PO4-- enabled differential diagnosis with no false-positive or false-negative cases. Among hydronephrotic kidneys, no biochemical parameter accurately predicted postnatal function, although creatinine was increased in all three nonfunctioning kidneys. In hydronephrotic kidneys, urinary Na+ concentration increased with advancing gestational age (r = .66; P < .02), suggesting that the duration of hydronephrosis has a negative effect on renal function.

Genetic relationships among strains of Salmonella enteritidis in a national epidemic in Switzerland

A collection of Salmonella enteritidis strains isolated in Switzerland (1965-90) was characterized. The phage type and plasmid profile of isolates were compared with the copy number and insertion loci of the DNA insertion element IS200. Three clonal lines of S. enteritidis were identified by IS200 profile; the various phage types were subtypes reproducibly associated with one of these lines. All human and poultry isolates contained a 38 Mda plasmid which hybridized with a mouse virulence-associated gene probe. In S. enteritidis, the IS200 profile is a race-specific molecular marker of the chromosome, and may be particularly applicable for studying the epidemiology of less common serovars.

Fetal urine biochemistry in the assessment of obstructive uropathy

In 60 fetuses with obstructive uropathy, sodium, total calcium, urea, and creatinine were measured in samples obtained by "urodochocentesis" or pyelocentesis at 16 to 36 weeks' gestation. The patients were retrospectively assigned into two groups on the basis of outcome. Group 1 (n = 20) included infants who either had normal postnatal renal function or absence of prenatal renal dysplasia. Group 2 included infants who either had histologic evidence of renal dysplasia or subsequently developed renal failure. In group 1 the urinary sodium decreased and creatinine increased with gestation, demonstrating maturation in fetal renal function. In group 2 the urinary sodium and calcium were higher and the urinary urea and creatinine were lower than in group 1. The best predictor of outcome was the combination of either high calcium or high sodium with a positive predictive value of 91.3% and negative predictive value of 77.7%. In the antenatal evaluation of obstructive uropathy, fetal urinary biochemistry provides useful information for more accurate counseling of the parents and a rational basis for selecting patients who may benefit from intrauterine therapeutic interventions.

Fetal urine biochemistry: an index of renal maturation and dysfunction

OBJECTIVE

To construct a reference range for fetal urinary sodium, potassium, urea, creatinine, calcium and phosphate with gestation and to assess to what extent these biochemical indices are modified in fetuses with lower urinary tract obstruction.

DESIGN

Prospective descriptive study.

SETTING

Royal Postgraduate Medical School London.

SUBJECTS

24 women between 17 and 35 weeks gestation with an ultrasound diagnosis of fetal lower urinary tract obstruction, with or without renal dysplasia and a control group of 26 women between 16 and 33 weeks gestation with normal amniotic fluid volume and fetal anatomy.

INTERVENTIONS

Fetal urine samples (1-100 ml) were aspirated from the control fetuses either before termination of pregnancy (n = 9) or at the time of intrauterine transfusion for Rh alloimmunization (n = 17). The fetuses with obstructive uropathy had urine samples aspirated on one occasion (n = 14) or serially (n = 10).

MAIN OUTCOME MEASURES

Relation between urine biochemistry and renal damage ascertained clinically or at postmortem.

RESULTS

In the control group, urinary sodium and phosphate decreased and creatinine increased significantly with gestational age, consistent with increasing fetal glomerular filtration rate and progressive maturation of tubular function. Urinary sodium and calcium were significantly higher in fetuses with renal dysplasia compared with those with lower urinary tract obstruction but normal renal histology or normal clinical outcome. Serial urinary samples from fetuses with obstructive uropathy showed more pronounced deviation from the normal with increasing gestation in all fetuses with renal dysplasia. The highest sensitivity in the detection of renal dysplasia was shown by urinary calcium (100%) whereas urinary sodium showed the best specificity (80%).

CONCLUSION

Renal damage is the direct effect of urinary obstruction, rather than an association so that treatment should start as soon as possible. Urinary biochemistry may be helpful in the management of these patients.

Numbers of Salmonella enteritidis in the contents of naturally contaminated hens' eggs

Over 5700 hens eggs from 15 flocks naturally infected with Salmonella enteritidis were examined individually for the presence of the organism in either egg contents or on shells. Thirty-two eggs (0.6%) were positive in the contents. In the majority, levels of contamination were low. Three eggs, however, were found to contain many thousands of cells. In eggs where it was possible to identify the site of contamination, the albumen was more frequently positive than the yolk. Storage at room temperature had no significant effect on the prevalence of salmonella-positive eggs but those held for more than 21 days were more likely (P less than 0.01) to be heavily contaminated. In batches of eggs where both shells and contents were examined, 1.1% were positive on the former site and 0.9% in the latter.

Further predictors of renal dysplasia in fetal obstructive uropathy: bladder pressure and biochemistry of 'fresh' urine

Urine was aspirated on two consecutive days from the dilated bladder of nine fetuses with lower urinary tract obstruction. Gestational age ranged from 17 to 35 weeks. Renal dysplasia was diagnosed histologically in four fetuses, whereas the other five had normal renal histology or only partial dysplasia. Urinary sodium (Na+) and osmolality (Osm) decreased significantly in the second urine sample 1 day after bladder emptying (median decrease: Na+ = -11.3 per cent; Osm = -13.3 per cent). Although there were no significant differences between fetuses with or without renal dysplasia, normalization of an initially raised urine Na+ concentration occurred at the second sample in a fetus with partially normal renal histology, thus correcting a false-positive diagnosis of dysplasia. Bladder pressure was measured at the time of the first urine sampling in seven fetuses and in a further eight with bladder outlet obstruction undergoing a single urine aspiration at 18-28 weeks. Bladder pressure was increased above the reference range in 8 of 15 fetuses with urinary obstruction, but there was no correlation between pressure and the degree of impairment of renal function. Although no conclusive clinical guidelines can be drawn from this study for the evaluation of fetal renal function, these findings suggest that, in lower urinary tract obstruction, tubular reabsorption is impeded by the standing pressure in the urinary tract and that improvement of renal function may occur following relief of obstruction.

International increase in Salmonella enteritidis: a new pandemic?

Over the past 5 years Salmonella enteritidis infections in humans have increased on both sides of the Atlantic ocean. The WHO salmonella surveillance data for 1979-87 were reviewed and show that S. enteritidis appears to be increasing on at least the continents of North America, South America, and Europe, and may include Africa. S. enteritidis isolates increased in 24 (69%) of 35 countries between 1979 and 1987. In 1979, only 2 (10%) of 21 countries with reported data reported S. enteritidis as their most common salmonella serotype; in 1987, 9 (43%) of 21 countries reported S. enteritidis as their most common serotype; 8 (89%) of 9 were European countries. Although the reason for the global increase is not yet clear, investigations in individual countries suggest it is related to consumption of eggs and poultry which harbour the organism.

Serological response of chickens to Salmonella enteritidis infection

Fifty-eight sera, from 29 chickens originating from two layer flocks known to be naturally infected with Salmonella enteritidis phage type (PT) 4, were examined for antibodies to S. enteritidis. Using the techniques of immunoblotting and ELISA, antibodies to the lipopolysaccharide (LPS) of S. enteritidis were detected in 43 of 58 sera. Antibodies were of the IgG class and bound to the S. enteritidis LPS antigen O = 12. Bacterial agglutination reactions using whole-cell preparations of S. enteritidis and S. pullorum, correlated with anti-LPS antibody reactions as detected by immunoblotting and ELISA. A rapid means of screening chicken sera for antibodies to the LPS of S. enteritidis as an indicator of infection is discussed.

A large outbreak of Salmonella enteritidis phage type 4 associated with eggs from overseas

In February 1989 the largest reported outbreak to date in the United Kingdom of Salmonella enteritidis phage type 4 (PT4) infection occurred following a wedding reception at a hotel. One hundred and seventy-three people met the case definition of illness of whom 118 had the organism isolated from their stools. A further 17 were found to be S. enteritidis PT4 positive, but were asymptomatic. Lightly-cooked, egg-based sauces were the epidemiologically proven vehicles of infection. Investigations showed this outbreak to be the first to implicate imported European eggs as the source of infection. An unusual feature of this outbreak was a reported incubation period of less than 3 h for some of the confirmed cases of salmonellosis.

Salmonella enteritidis phage type 4 from the contents of intact eggs: a study involving naturally infected hens

Two small flocks of egg-laying hens, naturally infected with Salmonella enteritidis, were housed in individual cages so that their eggs could be identified. During a longitudinal study where the contents of 1,119 eggs were examined, 11 were positive for S. enteritidis. One isolate was phage type (PT) 33 the others were PT4. The production of infected eggs was clustered though intermittent. The positive eggs, which were produced by 10 of the 35 hens, were all found to contain fewer than 10 salmonellas. Some birds were also apparently carrying S. hadar PT14 as this organism was isolated from the contents of six cracked eggs.