Elevated arterial base deficit in trauma patients: a marker of impaired oxygen utilization

BACKGROUND

In trauma patients, the admission value of arterial base deficit stratifies injury severity, predicts complications, and is correlated with arterial lactate concentration. In theory, elevated base deficit and lactate concentrations after shock are related to oxygen transport imbalance at the cellular level. The purpose of this study was to test the hypothesis that an elevated base deficit in trauma patients is indicative of impaired systemic oxygen utilization and portends poor outcomes.

METHODS

This study was a retrospective analysis of a prospectively collected database. The study population included all patients admitted to the trauma intensive care unit at a Level 1 trauma center during a 12-month period who were monitored with a pulmonary artery catheter and serial measurements of lactate and base deficit, and who achieved a normal arterial lactate concentration (< 2.2 mmol/L) with resuscitation. The patients were divided into those who maintained a persistently high base deficit (> or = 4 mmol/L) and those who achieved a low base deficit (< 4 mmol/L) during resuscitation.

RESULTS

One-hundred patients (mortality 20%) were monitored with a pulmonary artery catheter and achieved a normal arterial lactate concentration. The mean age+/-SD (SEM) of the group was 37+/-17 years and the Injury Severity Score was 25+/-11. Subgroup analysis revealed that patients with a persistently high base deficit (n=26) had higher rates of multiple organ failure (35% versus 5%, p < 0.001) and death (50% versus 9%, p < 0.00001) compared with patients who achieved a low base deficit. Patients with a persistently high base deficit also had lower oxygen consumption (126+/-40 mL/m2 versus 156+/-30 mL/m2, p=0.01 at 48 hours) and a lower oxygen utilization coefficient (0.20+/-0.05 versus 0.24+/-0.03, p=0.01 at 48 hours) compared with patients with a low base deficit. At 48 hours, both oxygen consumption (r=-0.44, [r, correlation coefficient] p=0.002) and oxygen utilization (r=-0.46, p=0.001) had a significant negative correlation with base deficit.

CONCLUSIONS

In trauma patients, a persistently high arterial base deficit is associated with altered oxygen utilization and an increased risk of multiple organ failure and mortality. Serial monitoring of base deficit may be useful in assessing the adequacy of oxygen transport and resuscitation.

A C-terminal motif found in the beta2-adrenergic receptor, P2Y1 receptor and cystic fibrosis transmembrane conductance regulator determines binding to the Na+/H+ exchanger regulatory factor family of PDZ proteins

The Na+/H+ exchanger regulatory factor (NHERF) binds to the tail of the beta2-adrenergic receptor and plays a role in adrenergic regulation of Na+/H+ exchange. NHERF contains two PDZ domains, the first of which is required for its interaction with the beta2 receptor. Mutagenesis studies of the beta2 receptor tail revealed that the optimal C-terminal motif for binding to the first PDZ domain of NHERF is D-S/T-x-L, a motif distinct from those recognized by other PDZ domains. The first PDZ domain of NHERF-2, a protein that is 52% identical to NHERF and also known as E3KARP, SIP-1, and TKA-1, exhibits binding preferences very similar to those of the first PDZ domain of NHERF. The delineation of the preferred binding motif for the first PDZ domain of the NHERF family of proteins allows for predictions for other proteins that may interact with NHERF or NHERF-2. For example, as would be predicted from the beta2 receptor tail mutagenesis studies, NHERF binds to the tail of the purinergic P2Y1 receptor, a seven-transmembrane receptor with an intracellular C-terminal tail ending in D-T-S-L. NHERF also binds to the tail of the cystic fibrosis transmembrane conductance regulator, which ends in D-T-R-L. Because the preferred binding motif of the first PDZ domain of the NHERF family of proteins is found at the C termini of a variety of intracellular proteins, NHERF and NHERF-2 may be multifunctional adaptor proteins involved in many previously unsuspected aspects of intracellular signaling.

Direct luteinizing hormone action triggers adrenocortical tumorigenesis in castrated mice transgenic for the murine inhibin alpha-subunit promoter/simian virus 40 T-antigen fusion gene

Transgenic (TG) mice, expressing the Simian Virus 40 T-antigen (Tag) under a 6-kb fragment of the murine inhibin alpha-subunit promoter (inh alpha p), develop gonadal tumors of granulosa/theca or Leydig cell origin. We showed previously that adrenocortical tumors develop if the TG mice are gonadectomized but never develop in intact animals. However, if functional gonadectomy was induced by GnRH antagonist treatment or by cross-breeding the TG mice into the hypogonadotropic hpg genetic background, neither gonadal nor adrenal tumors appeared. Since the most obvious difference between the gonadectomized and GnRH-antagonist-treated or Tag/hpg double mutant mice is the elevated gonadotropin secretion in the first group, we examined whether the adrenal tumorigenesis would be gonadotropin-dependent. Surprisingly, both the adrenal tumors and a cell line (C alpha 1) derived from one of them expressed highly functional LH receptors (LHR), as assessed by Northern hybridization, immunocytochemistry, ligand binding, and human CG (hCG)-stimulated cAMP and steroid production. No FSH receptor expression was found in the adrenal tumors by RT-PCR. hCG treatment of the C alpha 1 cells stimulated their proliferation, as measured by [3H]thymidine incorporation. This effect was related to hCG-stimulated steroidogenesis since progesterone, testosterone, and estradiol, at physiological concentrations, also stimulated the C alpha 1 cell proliferation. Different adrenocortical cells expressed initially LHR and Tag, whereas both were highly expressed in the tumor cells. In conclusion, the high level of functional LHR in the adrenal tumors indicates that this receptor can function as tumor promoter when ectopically expressed and stimulated by the ligand hormone.

A missense mutation in the BRCA2 gene in three siblings with ovarian cancer

Inherited susceptibility to ovarian cancer has been associated with germline defects at several loci. The major known ovarian cancer susceptibility gene is BRCA1 on chromosome 17q, which confers a risk of approximately 60% by the age of 70 years. Truncating mutations in BRCA2 on chromosome 13q also predispose to ovarian cancer, although they confer a lower risk than mutations in BRCA1. We have studied the molecular basis of ovarian cancer predisposition in a Finnish family with three affected sisters. Analysis of polymorphic markers provided evidence against linkage to BRCA1, but the sibship was consistent with linkage to BRCA2. Conformation-sensitive gel electrophoresis was used to screen the entire coding sequence of BRCA2. A G to A transition at nucleotide 8702 was observed, which is predicted to convert glycine 2901 to aspartate in the encoded protein. This sequence variant was not detected in 220 cancer-free Finnish control individuals, or in several hundred cancer families of many nationalities previously screened for BRCA2 mutations. Taken together with the fact that this amino acid residue and the surrounding region of BRCA2 is identical in mouse and chicken, the data suggest that this alteration is a disease-causing BRCA2 missense mutation. Previously published data indicate that the risks of breast and ovarian cancer conferred by BRCA2-truncating mutations varies with the position of the mutation in the gene. The missense mutation reported here suggests that the BRCA2 domain including and surrounding glycine 2901 may be more important in preventing neoplastic transformation in ovarian epithelium than in breast epithelium.

The health of Australian children and young adults: recent statistics

The lack of reliable national statistics to monitor the health of Australian children and youths is well recognised (Commonwealth Department of Human Services and Health 1995). There is a clear need to develop this information through a nationally integrated and coordinated approach. The best way to achieve this would be to scope the fields of child and youth health information, identify data gaps and deficiencies, and catalogue the data requirements and needs. The framework within which this should occur, accompanied by a national child and youth health information development plan, also needs to be clearly defined. The Australian Institute of Health and Welfare is undertaking an analysis of the health of Australian children and youths and a review of available information in this area. Here we present early work on this project, providing a general picture of the health of Australian children and youths based on mortality, morbidity, reported health status and disability statistics. Some information on the health of indigenous children and young people is also included.

Use of integral and differential methods for the determination of L-dopa in pure form and pharmaceutical preparations

A new simple and selective kinetic method for the determination of L-dopa, using differential and integral methods, is described. The spectrophotometric measurements were recorded by measuring the increase in absorbance at 300 nm. The concentration range was valid from 5-35 ppm. The complex ratio showed a (1:2) of L-dopa with respect to sodium hydroxide, with formation constant 5.06 x 10(6) and molar absorptivity of 3.85 x 10(3) l mol-1 cm-1.

The familial Wilms' tumour susceptibility gene, FWT1, may not be a tumour suppressor gene

A familial Wilms' tumour susceptibility gene, known as FWT1, has recently been localised to chromosome 17q12-q21 by genetic linkage analysis. Four Wilms' tumours from a family showing strong evidence of linkage to FWT1 were examined for allele loss using polymorphic microsatellite markers on chromosome 17q. In three tumours no loss of heterozygosity was observed. In the remaining case, loss of heterozygosity was detected at all markers analysed. However, the alleles lost in this Wilms' tumour were those segregating with the disease in the family. This is in contrast to the usual pattern observed in familial cancer syndromes, where the allele lost in tumours arising in gene carriers is the wild type inherited from the non mutation carrying parent. Taken together with previous data indicating that LOH on chromosome 17q is rare in sporadic Wilms' tumour, the results suggest that FWT1 is not a tumour suppressor gene. Moreover, loss of alleles linked to the disease and the implied absence of the mutated susceptibility gene in one tumour, suggests that a mutation in FWT1 may be necessary for the initiation of some familial Wilms' tumours but subsequently the maintenance of the neoplastic phenotype becomes independent of the FWT1 mutation.

Evidence for a familial Wilms' tumour gene (FWT1) on chromosome 17q12-q21

Wilms' tumour (WT) is one of the most common solid tumours of childhood, occurring in 1 in 10,000 children and accounting for 8% of childhood cancers. It is believed to result from malignant transformation of abnormally persistent renal stem cells (nephrogenic rests) which retain embryonic differentiation potential. Although WT is usually sporadic, approximately one percent occur in families in which susceptibility appears to be inherited as an autosomal dominant trait with incomplete penetrance. Predisposition to other cancers or to the developmental abnormalities associated with sporadic WT is not usually apparent in WT families. The WT1 gene at 11p13 (ref.2), and additional genes on chromosomes 11p15 (ref. 3) and 16q (ref. 4) have been implicated in the development of WT but are not responsible for familial WT. We have carried out a genome linkage search in a large Canadian family with seven confirmed cases of WT. Our results provide strong evidence for the localisation of a familial WT predisposition gene, FWT1, to an 18-centimorgan (cM) interval on chromosome 17q12-q21.

Multiloculated hydrocephalus related to cerebrospinal fluid shunt infection

This study is an attempt to establish that CSF shunt infection has a role in the aetiology of multiloculated hydrocephalus. The authors carried out a review of 12 cases of multiloculated hydrocephalus who were treated at King Khalid University Hospital between 1988-1994. The multiloculation appears to have developed following the shunt infection in all cases. The hydrocephalus was related to an intraventricular haemorrhage (IVH) in 9 patients and was congenital in 2 patients and post-meningitic in 1 patient. The shunt infection was caused by a gram-negative organism in 8 patients and duration of external ventricular drainage ranged from 9-24 (median 13) days. The diagnosis of multiloculated hydrocephalus was made on average 2 months after the shunt infection. In three patients endoscopic fenestration of intraventricular septations was attempted but was effective in only one case. The other patients were managed by two shunts (9 patients) and three shunts (2 patients). At a mean follow-up of 15 months, the shunt revision rate of the patients was 0.4/year. One patient died of multiple brain abscesses and 6 patients remain severely disabled. The poor outcome may also be related to the original IVH as well as the multiloculated hydrocephalus. The study also shows that patients with post-haemorrhagic hydrocephalus, who develop a shunt infection due to gram-negative organisms and in whom the CSF fails to be cleared of the infection following 12 days of external drainage appear to be at risk of developing multiloculated hydrocephalus.

Hand washing with soap reduces diarrhoea and spread of bacterial pathogens in a Bangladesh village

Hand washing with soap and water can prevent the spread of diarrhoeal diseases in areas where comparatively costly interventions, such as supply of safe water and improved sanitation, are not possible. In this study, the practice of hand washing with soap and water was instituted in a periurban slum of Dhaka city, and the surveillance for diarrhoea sustained for a one-year period. Rates of primary and secondary attacks were compared to those of a non-intervention area similar in age structure, economic status, education, and other relevant variables. Rectal swabs of cases and contacts established aetiologies. There was a large (2.6 fold) reduction in diarrhoeal episodes in the intervention area during the observation period. Rates of bacterial pathogens were also lower in the intervention area. Significant reduction in diarrhoeal incidences was observed in all age groups for all pathogens except for rotavirus. These observations if implemented as health policy could reduce the spread of diarrhoeal diseases at low cost in high risk areas.

Intracranial mycotic infections in neurosurgical practice

Intracranial mycotic infections requiring neurosurgical intervention are being diagnosed more frequently. This study is a review of 17 cases of intracranial mycotic infections that were treated in a neurosurgical unit in Saudi Arabia over an 8-year period. A primary focus of infection was identified in 41% of patients while 18% of patients had a predisposing factor. Forty-seven percent of patients presented with a brain abscess (solitary 29%, multiple 18%) while 35% had a granuloma. 18% meningitis and ventriculitis and 12% hydrocephalus. The Aspergillus species and Ramichloridium machenziei were the commonest pathogens. Following the appropriate surgical and antimicrobial treatment, the mortality rate was 41% and there was evidence of residual disease at follow-up in 18%. The reason for a fatal outcome was failure to consider a fungal aetiology and to obtain a tissue diagnosis early-because of late referral (2 cases), as well as failure to respond to antimycotic therapy (4 cases) and rupture of the internal carotid artery due to Aspergillus arteritis (one case). It is concluded that an early tissue diagnosis is crucial in the management of intracranial mycotic infection so that the appropriate surgical and antimycotic treatment can be started early.

Neurosurgical management of intraventricular haemorrhage in preterm infants

A review of intraventricular haemorrhage (IVH) diagnosed in 103 preterm infants from 1983 to 1993 describes the presenting features and management of this condition. In this 10-year period, 37 infants with IVH developed post-haemorrhagic hydrocephalus (PHH), defined as ventriculomegaly, raised intracranial pressure and increasing head circumference. PHH was treated by external ventricular drainage and/or ventriculo-peritoneal shunting; but other drainage procedures like lumbar punctures and subcutaneous ventricular reservoir were used occasionally. Relative indications, merits and demerits of these various surgical options is discussed and results summarized. High incidence of neuro-developmental handicap and its correlation with the grade of haemorrhage and PHH is emphasized. External ventricular drainage (EVD) was found to be an effective and safe therapy for rapidly progressive PHH and increased intracranial pressure. Ultimate outcome depended mainly on the grade of haemorrhage, severity of PHH and promptness of its neurosurgical management.

Choroidal detachment associated with retinal detachment as a presenting finding

Choroidal detachment along with retinal detachment as a presenting finding is rare. We identified five such cases presenting to our ophthalmology practice between 1964 and 1991. The patient is usually myopic and presents with marked visual loss, profound hypotony and a marked anterior chamber reaction. The pathogenesis seems to revolve around the hypotony and myopia and an unstable choroidal vascular system. Management usually involves a scleral buckling procedure with cryotherapy under direct visualization to release choroidal and subretinal fluid, possibly preceded by a few days of anti-inflammatory therapy. The overall prognosis is poor owing to delays in diagnosis and the postoperative development of proliferative vitreoretinopathy.

Prognostic indicators and risk factors for increased duration of acute diarrhoea and for persistent diarrhoea in children

To identify the prognostic indicators and risk factors for increased duration of acute diarrhoea and for occurrence of persistent diarrhoea (i.e. acute episodes lasting longer than 14 days) in children under three years, a systematic sample (3690) of patients attending a large treatment centre in Bangladesh was analysed using multiple regression, logistic regression and stratified (Mantel-Haenszel) analysis. Significant prognostic indicators or risk factors for increase in duration of acute diarrhoea, after adjusting for confounders, include bloody or mucoid diarrhoea, concomitant signs of chest infection, presence of vitamin A deficiency signs, decreased weight for age, routine use of contaminated surface water, lack of breastfeeding and increasing age; presence of rotavirus or enterotoxigenic Escherichia coli or Vibrio cholerae 01 in stool had negative association. In logistic regression and stratified analysis these factors, except for lack of breastfeeding and age, were also found to be risk factors or prognostic indicators of persistent diarrhoea. Policy implications of these findings for programmes to reduce morbidity and mortality from persistent diarrhoea include development of effective vaccines against dysentery-causing Shigella, programmes to prevent vitamin A deficiency, protein energy malnutrition and acute respiratory infections in children, and long-term programmes to provide clean water for all day-to-day needs.

Impact of acute diarrhoea on parasite loads

Parasites and diarrhoea are more frequent in poor populations. Parasite prevalence rates in post-diarrhoeal patients of the International Centre for Diarrhoeal Disease Research (ICDDRB) and in non-diarrhoeal populations of two Dhaka poor socioeconomic communities have been compared to explore if there is any effect of acute diarrhoea on parasite prevalence rates. Stool of a 4% systemic randomly selected sample of diarrhoeal patients and the whole population of two local poor communities have been examined. The results showed that the prevalence of parasites in a post-diarrhoeal population is significantly lower than in a non-diarrhoeal population. These reductions (E. hist. 10.2% vs. 2.03%, G. lamb. 9.7% vs. 3.5%, hookworm 37.4% vs. 4.7% and Ascaris lumbricoides 81% vs. 20.6%) may be attributed mainly to the flushing effect of diarrhoea.

Cryptosporidiosis: a cause of diarrhea in Bangladesh

Fecal samples from diarrheal patients and non-diarrheal controls were examined for Cryptosporidium oocysts in a year-long prospective study at a diarrhea treatment center in Dhaka, Bangladesh. Cryptosporidium oocysts were detected in 42 (3%) of 1,382 diarrheal patients but in none of 235 non-diarrheal controls. In 32 (76%) of 42 patients, no other enteropathogens were detected. Children less than 5 years of age were more commonly infected than older children (4.8% vs. 1.6%, P greater than 0.05) and adults (4.8% vs. 0.2%, P less than 0.01). A higher number of cases were detected during hot and humid months (April--July). Nineteen children less than 5 years of age (index cases) and their 71 family members were followed for 3 weeks after the release of the index cases from the hospital. Diarrhea continued for greater than 14 days (persistent diarrhea) in 8 (32%) index children. Cryptosporidium oocysts were detected in 1 (12.5%) of 8 family members who developed diarrhea during the follow-up period. Index cases excreted oocysts for 3-28 days (12.37 +/- 8.35 days). Almost all the patients recovered with oral rehydration. Cryptosporidium ssp. cause self-limited diarrhea episodes in children less than 5 years of age in Bangladesh, with a low frequency of intrafamilial transmission.

Risk factors for persistent diarrhoea

With a systematically sampled population of children aged under 5 attending this centre for diarrhoeal disease research during 1983-5 a retrospective analysis of persistent diarrhoea (defined as greater than 14 days' duration) was performed to identify the possible risk factors for this syndrome. Of the 4155 children included in the analysis, 410 (10%) gave a history of persistent diarrhoea. A comparison with children with acute diarrhoea matched for age showed that 11 factors were correlated with persistent diarrhoea, and strongly associated factors were stools with blood or mucus, or both, lower respiratory tract infection, malnutrition, vitamin A deficiency, and antibiotic use before presentation. The peak age was 2 years, and there was no sex difference. Deaths occurred more often in the group with persistent diarrhoea. Although Shigella spp, Campylobacter jejuni, and Giardia lamblia were frequently identified, their rates of isolation were not significantly higher among patients with persistent diarrhoea. No seasonal variation was observed in the rates of persistent diarrhoea. Although the introduction of family food to the diet was associated with higher rates, this factor was difficult to separate from the age dependent risks.

Cholera, rotavirus and ETEC diarrhoea: some clinico-epidemiological features

This paper analyses a few selected features from the history and clinical examination of 1258 patients with acute diarrhoea and a single laboratory diagnosis of either cholera, rotavirus, or enterotoxigenic (ETEC) Escherichia coli infection. Age distribution and seasonality in Bangladesh were also studied. The duration of illness before admission was not significantly different in the 3 groups. Cholera occurred especially in the spring and early winter. Most cholera patients were between 3 and 10 years of age. Over 37% of the patients developed severe dehydration. In about 90% of cholera cases, the stools were alkaline (pH greater than 7). ETEC infections were seen mostly in April-May and September-October. Infants were frequently affected but from age 25 onwards the age distribution closely followed that of cholera. Severe dehydration occurred in 8.3% of patients and was more frequent than in rotavirus cases. Stool pH was as frequently acidic as basic. Rotavirus cases were concentrated during the winter in patients under 2 years of age. They had marked vomiting, yet severe dehydration was almost absent. Cough was present in half of them. The stools were usually acidic. In spite of considerable overlap of signs and symptoms between the 3 aetiological groups, a presumptive diagnosis of cholera could be made in patients past infancy and early childhood who showed very severe dehydration. However, age-specific prevalence was strikingly different and seasonal variations considerable.

Estrogen screening in evaluation of fetal outcome and infant's development

In an unselected obstetric population of 869 women serial determinations of estriol in serum and urine were performed from the 28th week of pregnancy until delivery. Clinical management was based on ultrasound and nonstress/contraction stress tests only. Data on the development of the infants were available after 1 year in 759 cases (89%) and after 2 years in 661 cases (78%). Serum free estriol (E3) screening during weeks 28-34 of pregnancy revealed a significantly increased risk for reduced Apgar scores, growth retardation and postnatal complications in pregnancies with decreased levels (p less than 0.001). The development of the children was disturbed by a higher incidence of childhood diseases, retardation in speech and bowel and bladder control. The urinary estrogen determinations (UE) during this period of pregnancy showed only a vague connection with birth weight and Apgar scores (p less than 0.05) and no connection to the infant's development. Serial determinations of E3 after the 35th week of pregnancy increased the significance for all parameters tested. If the estrogen concentration was determined in the last 2 weeks before delivery, 50% of the SGA and 60% of the endangered cases could be diagnosed. After reduced E3 serial levels neurological sequelae, reduced body weight, retarded speech and late development of bowel and bladder control were significantly more frequent at age two than after normal E3 levels. The differences obtained by serial UE determinations were less evident. Considering cost-benefit-calculations, an E3 screening of every pregnant woman cannot recommended. In pregnancies at risk serial E3 determinations allow better prognostication of fetal well-being. In the case of reduced E3 values maximum post partum care should be made available for all newborns. Special support should be given to the early infant's development after reduced E3 values have been observed.

Changing pattern of resistant Shiga bacillus (Shigella dysenteriae type 1) and Shigella flexneri in Bangladesh

Shigella dysenteriae type 1 (Shiga bacillus) has made a dramatic comeback in Bangladesh after 10 years when Shigella flexneri was the dominant serogroup. Whereas S. flexneri showed little increase in resistance to the commonly used antimicrobial agents--namely, trimethoprim-sulfamethoxazole (TMP-SMX) and ampicillin-over the years, S. dysenteriae type 1 underwent rapid changes with regard to sensitivity pattern during the last two years. The first TMP-SMX-resistant strain of S. dysenteriae type 1 was detected in September 1982; however, by mid-1984 most strains were resistant while retaining sensitivity to ampicillin. During this period, the ratio of S. flexneri to S. dysenteriae type 1 narrowed from 0.15 to 1. Such propagation of high resistance to TMP-SMX might have been due to widespread use of the drug imported into the country in large quantities. Resistance to ampicillin is increasing rapidly, particularly in S. dysenteriae type 1.

Changes in the trend of shigellosis in Dhaka: family study on secondary infection, clinical manifestation and sensitivity pattern: 1980

The incidence of shigellosis and the death rate have increased and the resistance of shigellae to antibiotics has changed in Dhaka during our experiences. In 1980, we investigated the secondary infection and case rates, infection to case ratio, duration of illness, excretion of shigellae and antibiotic sensitivity pattern in 100 families with cases of shigellosis, culturing rectal swabs obtained by home visits for a 10-day period. Standard methods were used for culture and sensitivity tests. The over-all secondary infection rate in contacts was 27.3% and the case rate 10.7%. The rates were higher for Shigella flexneri than for Sh. dysenteriae. When the index cases were nought to four years old the secondary infection and case rates were higher than when index cases were older. Contacts aged nought to four years had highest attack rates. The average duration of excretion of Sh. flexneri was 4.5 and Sh. dysenteriae 2.6 days. Illness was one day longer for Sh. dysenteriae than for Sh. flexneri. Cases of shigellosis in hospital had higher rates of fever and blood in stool than those who were not in-patients. 40% of Sh. dysenteriae and 14% of Sh. flexneri were sensitive to tetracycline, 0 to 5% to streptomycin and 100% to sulphamethoxazole, trimethoprim and gentamicin. Incidence of Sh. flexneri had increased in 1980 but that of Sh. dysenteriae remained the same as in 1973 although Sh. dysenteriae type 1 appeared to be less infective in 1980 than in 1973.