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Much has been learned about organism in the Cronobacter/Enterobacter sakazakii complex since I first named and described Enterobacter sakazakii in 1980. However, there are still wide knowledge gaps. One of the most serious is that are still many uncertainties associated with assessing the public health risk posed by these bacteria, particularly in neonatal meningitis. Over the last few decades, Cronobacter contamination of commercial powdered infant formula products has apparently been reduced, but it is still an ongoing problem. The powdered infant formula industry still cannot produce powdered formula that is free of bacterial contamination with Cronobacter, other Enterobacteriaceae, other pathogenic bacteria, and other microorganisms. Until this happens, infants and other will be at risk of becoming infected when they ingest contaminated formula.

Background: Enterobacter sakazakii is an emergent pathogen that has been associated with neonatal infections through contaminated powdered infant milk formula. The species was defined by Farmer et al. (1980) who described 15 biogroups according to the biochemical characterization of 57 strains. This present study compares genotypes (DNA cluster groups based on partial 16S rDNA sequence analysis) with the biochemical traits for 189 E. sakazakii strains., Results: Analysis of partial 16S rDNA sequences gave 4 well defined phylogenetic groups. Cluster group 1 was composed of the majority of strains (170/189) and included Biogroups 1-5, 7-9, 11, 13 and 14. Cluster 3 corresponded with Biogroup 15 and cluster 4 with Biogroups 6, 10 and 12. Cluster group 2 comprised a new Biogroup 16. For the isolates in this study, the four DNA cluster groups can be distinguished using the inositol, dulcitol and indole tests., Conclusion: This study demonstrates an agreement between genotyping (partial 16S rDNA) and biotyping and describes a new biogroup of E. sakazakii.

When enteric group 58 was first described as a distinct new group of Enterobacteriaceae in 1985, there were only five known human isolates: four from wounds and one from feces. In 1996, we investigated the first blood isolate of enteric group 58, a case of sepsis in a 33-year-old woman receiving total parenteral nutrition. Fifteen additional clinical isolates have since been identified at CDC, including several recognized from a collection of "unidentified" strains dating back to 1973. All strains were characterized with a standard set of 49 biochemical tests used for Enterobacteriaceae, and the results were analyzed to determine phenotypic relatedness and best taxonomic fit. Antibiograms were determined as a taxonomic tool. Original identifications provided by submitting laboratories encompassed a wide variety of Enterobacteriaceae, including 14 species in eight genera, the most common being Enterobacter spp., Salmonella spp., Serratia spp., Kluyvera spp., or Escherichia spp. Enteric group 58 strains have been most frequently isolated from traumatic injuries, fractures, and wounds and rarely from feces. Defining its clinical significance and distinguishing infection from colonization requires further study, but our case report indicates that serious systemic infection can occur. The vernacular name enteric group 58 was used from 1985 to 2004. In this paper, we formally name it Averyella dalhousiensis gen. nov., sp. nov., on the basis of its unique phenotype and its unique 16S rRNA gene sequence. These data indicate that enteric group 58 is not closely related to any of the existing genera or species of Enterobacteriaceae. The type strain is designated CDC 9501--97, and a phenotypic definition is given based on all 21 strains.

A member of the Enterobacteriaceae initially identified as Kluyvera cryocrescens by the MicroScan Gram-Negative Combo 13 panel caused an outbreak of nosocomial infections in four patients (pneumonia, n = 2; urinary tract infection, n = 1; wound infection, n = 1) and urinary tract colonization in one patient. When the strains were tested by the Enteric Reference Laboratory of the Centers for Disease Control and Prevention, biochemical results were most compatible with Yersinia intermedia, Kluyvera cryocrescens, and Citrobacter farmeri but identification scores were low and test results were discrepant. However, when the biochemical test profile was placed in the computer database as a new organism, all strains were identified as the organism with high identification scores (0. 999968 to 0.999997) and no discrepant test results. By 16S rRNA sequence analysis the organism clustered most closely with, but was distinct from, Citrobacter farmeri and Citrobacter amalonaticus. Based on its unique biochemical profile and rRNA sequence, this organism is designated Enteric Group 137. Restriction endonuclease analysis and taxonomic antibiograms of strains causing the outbreak demonstrated a single clone of Enteric Group 137, and antibiotic susceptibility testing revealed the presence of extended-spectrum beta-lactamase (ESBL) resistance. Enteric Group 137 appears to be a new opportunistic pathogen that can serve as a source of ESBL resistance in the hospital.

Background: Vibrio vulnificus is a gram-negative bacterium that causes septicaemia and wound infection. Cases occur sporadically, and no previous outbreaks due to a common source or a clonal strain have been reported. In the summer and autumn of 1996 and 1997, an outbreak of invasive V. vulnificus infection occurred in Israel in people who had recently handled fresh, whole fish purchased from artificial fish-ponds., Methods: We reviewed clinical and epidemiological information, and undertook an environmental investigation to assess disease characteristics, modes of transmission, phenotypic characteristics of the bacterium, and fish-marketing policy. The clonal nature of 19 isolates was studied by biotyping, pulsed-field gel electrophoresis, and restriction-fragment length polymorphism (RFLP) analysis of a PCR fragment., Findings: During 1996-97, 62 cases of wound infection and bacteraemia occurred. 57 patients developed cellulitis, four had necrotising fasciitis, and one developed osteomyelitis. In all cases, the fish were cultivated in inland fish-ponds. In the summer of 1996, fish-pond managers initiated a new marketing policy, in which fish were sold alive instead of being packed in ice. Phenotypically, the isolates had five atypical biochemical test results. The isolates were non-typeable by pulsed-field gel electrophoresis, and all had the same PCR-RFLP pattern which had not been seen previously., Interpretation: The cause of the outbreak was a new strain of V. vulnificus, classified as biogroup 3. A new fish-marketing policy that began in 1996 may have exposed susceptible people to the organism.

Since October 1992, > 150,000 cases of cholera have been reported from India and Bangladesh; the great majority of Vibrio cholerae isolates belong to the newly established serogroup O139. To better understand the interaction of genetic and epidemiologic factors responsible for their sudden appearance and rapid spread, representative toxigenic V. cholerae O139 isolates were molecularly characterized and compared with a set of toxigenic V. cholerae O1 and non-O1/non-O139 strains. DNA sequences of the cholera toxin B subunit gene and multilocus enzyme electrophoresis markers of V. cholerae O139 strains were identical to those of V. cholerae O1 isolates of the seventh pandemic. Two distinct ribotypes and four pulsed-field gel electrophoretic patterns were observed for O139 strains. V. cholerae O139 strains were very similar to V. cholerae O1 strains of the seventh pandemic but clearly different from the toxigenic V. cholerae strains of serogroups other than O1 and O139.

Three additional phage typing systems for Salmonella enteritidis, plasmid analysis, biochemical tests, and antimicrobial susceptibility tests, were used in an attempt to subdivide 30 phage type 8 (phage typing system used by the WHO International Center for Enteric Phage Typing, London, England) isolates. These isolates represented 18 different egg-related outbreaks (21 strains) and 9 reference strains or strains that were not egg-associated. Only 7 of the 30 strains (28%) were subdivided by one or more of the methods used; this included 3 of the 21 strains from egg-related outbreaks. Twenty-seven strains contained a 55-kb plasmid that is associated with S. enteritidis. Of 65 additional phages tested, 2 from the phage typing system obtained from the Pasteur Institute, Paris, France, were useful in differentiating the three strains that lacked the 55-kb plasmid. Although the results obtained for the 21 strains from egg-related outbreaks showed that the strains had minor phenotypic differences, the overall results suggested that the strains may represent a single clone. Studies are planned to test additional phages and other typing methods to see whether strains of phage type 8 can be further differentiated.

We evaluated several simple laboratory tests that have been used to identify pathogenic serotypes of Yersinia enterocolitica or to indicate the pathogenic potential of individual strains. A total of 100 strains of Y. enterocolitica were studied, including 25 isolated during five outbreak investigations, 63 from sporadic cases, and 12 from stock cultures. The pyrazinamidase test, which does not depend on the Yersinia virulence plasmid, correctly identified 60 of 63 (95% sensitivity) strains of pathogenic serotypes and 34 of 37 (92% specificity) strains of nonpathogenic serotypes. Salicin fermentation-esculin hydrolysis (25 degrees C, 48 h) correctly identified all 63 (100% sensitivity) strains of the pathogenic serotypes and 34 of 37 (92% specificity) strains of the nonpathogenic serotypes. The results of the pyrazinamidase and salicin-esculin tests disagreed for only 7 of the 100 strains of Y. enterocolitica, and these would require additional testing. Congo red-magnesium oxalate (CR-MOX) agar determines Congo red dye uptake and calcium-dependent growth at 36 degrees C, and small red colonies are present only if the strain contains the Yersinia virulence plasmid. This test has proven to be extremely useful for freshly isolated cultures, but only 15 of 62 strains of pathogenic serotypes that had been stored for 1 to 10 years were CR-MOX positive. None of the 16 strains of Y. enterocolitica serotype O3 fermented D-xylose, so this test easily differentiated strains of this serotype, which now appears to be the most common in the United States. Although antisera that can actually be used to serotype strains of Y. enterocolitica are not readily available, the four simple tests described above can be used to screen for pathogenic serotypes.

The number of reported isolates of Salmonella enteritidis has increased dramatically in the last 10 years. For many years phage typing has been a useful epidemiologic tool for studying outbreaks of S. typhi and S. typhimurium. In 1987, Ward et al. (L. R. Ward, J. De Sa, and B. Rowe, Epidemiol. Infect. 99:291-294, 1987) described a phage typing scheme for S. enteritidis. This system differentiated 27 phage types by use of 10 typing phages. With these phages, we typed 573 strains of S. enteritidis from humans (42 outbreaks), animals, food, and the environment. Ninety-six percent of the strains were typeable. The most common phage types were 8 (48.2%), 13a (20.1%), 13 (7.8%), and 14b (7.8%). Most of the strains were specifically collected from egg-related outbreaks in the northeastern United States in 1988 and 1989, probably accounting for the distribution of the four most common types in this sample. This system was particularly useful for differentiating a group of animal strains that had a number of diverse phage types. For 49 animal strains typed, 16 different patterns were obtained. Phage type 8 represented 32% of these strains, but no other phage type represented more than 8% of these strains. One-half of the 16 animal strains that were phage type 8 were from poultry. This phage typing system will be useful for comparing phage types found in the United States with those types encountered worldwide and for determining whether virulent strains of phage type 4 are entering the United States. Additional phage typing systems as well as molecular techniques are being studied to determine whether they can differentiate strains of phage types 8 and 13a.

In 1985 the vernacular name Enteric Group 90 was coined for a small group of strains that had been referred to our laboratory as probable strains of Salmonella but did not agglutinate in Salmonella typing antisera. By DNA-DNA hybridization (hydroxyapatite method, 32P), seven strains of Enteric Group 90 were found to be closely related (98 to 100% at 60 degrees C and 94 to 100% at 75 degrees C) to the first strain received (0370-85). The relatedness of Enteric Group 90 to 62 strains of other species of the family Enterobacteriaceae was only 6 to 41%, with the highest values obtained with strains of Salmonella, Kluyvera, Shigella, Klebsiella, Enterobacter, and Citrobacter. We propose a new genus, Trabulsiella, with a single new species, Trabulsiella guamensis, for the highly related group of eight strains formerly known as Enteric Group 90. The type strain is designated ATCC 49490 (CDC 0370-85). T. guamensis strains grew well at 36 degrees C and had positive reactions in the following tests: methyl red, citrate utilization (Simmons) (38% positive at day 1, 88% positive at 2 days), H2S production, lysine decarboxylase, arginine dihydrolase (50% positive at 2 days, 100% positive at 7 days), ornithine decarboxylase, motility, growth in KCN medium, mucate fermentation, acetate utilization, nitrate reduction to nitrite, weak tyrosine hydrolysis (88% positive at 2 days, 100% positive at 7 days), and ONPG (o-nitrophenyl-beta-D-galactopyranoside) test. The strains fermented D-glucose with gas production and fermented L-arabinose, cellobiose, D-galactose, D-galacturonate, maltose, D-mannitol, D-mannose, L-rhamnose, D-sorbitol, trehalose, and D-xylose. T. guamensis strains had negative reactions in the following tests: indole production (13% positive), Voges-Proskauer, urea hydrolysis, phenylalanine deaminase, malonate utilization, lipase (corn oil), DNase, oxidase, pigment production, and acid production from adonitol, D-arabitol, dulcitol, erythritol, myo-inositol, melibiose, alpha-methyl-D-glucoside, raffinose, and sucrose. There were delayed positive reactions for gelatin liquefaction (22 degrees C), which was positive at 12 to 23 days, esculin hydrolysis (13% positive at day 1, 50% positive at 7 days), lactose fermentation (13% positive at 3 to 7 days, 100% positive at 8 to 10 days), glycerol fermentation (88% positive at 7 days), and salicin fermentation (13% positive at day 1, 88% positive at 7 days). All strains were susceptible by the disk diffusion method to colistin, nalidixic acid, gentamicin, streptomycin, kanamycin, chloramphenicol, and trimethoprim-sulfamethoxazole, and most strains were susceptible to sulfadiazine (75% susceptible), tetracycline (88%), and carbenicillin (75%). The strains were resistant to penicillin, cephalothin, and ampicillin. The strains were isolated from vacuum cleaner dust (five strains), soil (one strain), and human feces (two strains). Although T. guamensis can occur in human diarrheal stools, there is no evidence that it actually causes diarrhea. Its main interest to clinical microbiologists may be its possible misidentification as a strain Salmonella.

After an outbreak of Yersinia enterocolitica infections among black children in Atlanta, a seven-hospital study was conducted to determine the importance of this pathogen in other communities with large black populations. Of 4841 stool specimens from patients with gastroenteritis examined between November 1989 and January 1990, Y. enterocolitica, Shigella, Campylobacter, and Salmonella were identified in 38, 49, 60, and 98 specimens, respectively; 34 (92%) of 37 Y. enterocolitica isolates were serotype O:3. Of the 38 patients with yersiniosis, 37 (97%) were children. Illnesses were clustered around the holidays, and 20 (62%) of 32 patients had been exposed to raw pork intestines in the 2 weeks before onset. Exposure was significantly associated with illness in a case-control study of eight patients identified at one hospital (P = .004). Infants less than or equal to 6 months old with yersiniosis were more likely to have immature-to-total neutrophil ratios greater than 0.50 than were infants of comparable age with salmonellosis (P = .02). Infrequently isolated in the past, Y. enterocolitica O:3 is emerging as an important enteric pathogen in this country, particularly among black children.

Between April 1987 and May 1989, the Centers for Disease Control investigated seven cases of transfusion-associated Yersinia enterocolitica sepsis; four were caused by organisms of serotype O:3, and one each was caused by organisms of serotype O:1,2,3; O:5,27; and O:20. All seven recipients developed septic shock after receiving units of red cells (RBCs) contaminated with Y. enterocolitica; five recipients died. The cases occurred in seven states and were unrelated. There was no evidence for contamination of the RBC units during processing. Six of the seven donors had serologic evidence of recent Y. enterocolitica infection, and it is hypothesized that these donors had asymptomatic bacteremia when they donated the implicated blood. Four of the seven donors reported gastrointestinal illness in the 4 weeks before blood donation, and one donor became ill on the day he donated blood. Y. enterocolitica grows well at 4 degrees C and in the presence of dextrose and iron. If blood is contaminated at the time of collection, storage of the RBCs at 4 degrees C provides an ideal environment for bacterial growth and endotoxin production. These cases demonstrate the need for careful evaluation of patients with transfusion reactions for possible sepsis and suggest a need to screen prospective blood donors for mild gastrointestinal illness, including those illnesses not requiring physician evaluation or medication.

To determine the pandemic potential of Vibrio cholerae, one must demonstrate both the presence of O1 antigen and the production of enterotoxin (CT). Tissue culture or enzyme-linked immunosorbent assays (ELISAs) for CT have been limited to research and reference laboratories. A kit for detecting CT by reversed passive latex agglutination is now commercially available and was used to test 168 strains of V. cholerae O1 and non-O1. When compared with the routine ELISA, the latex test was 98% accurate (86 of 88) for serogroup O1 strains and 100% accurate (80 of 80) for non-O1 strains. For both O1 and non-O1 study strains, the sensitivity of the latex agglutination test was 0.97 and the specificity was 1.00 when results were compared with ELISA results. The latex test is commercially available and has the advantages of being less complicated and less time-consuming than the ELISA.

The name Enterobacter hormaechei is proposed for a new species of the family Enterobacteriaceae, formerly called Enteric Group 75, which consists of 23 strains, 22 of which were isolated from humans. DNAs from 12 E. hormaechei strains tested were highly related to the type strain (ATCC 49162) by DNA hybridization, using the hydroxyapatite method (80 to 97% in 60 degrees C reactions; 80 to 90% in 75 degrees C reactions). The strains were most closely related (50 to 63%) to Enterobacter cloacae, Enterobacter dissolvens, Enterobacter taylorae, and Enterobacter nimipressuralis. E. hormaechei strains were positive within 48 h for the following: Voges-Proskauer test; citrate utilization (Simmons and Christensen); urea hydrolysis (87%); ornithine decarboxylase; growth in potassium cyanide (KCN); malonate utilization; production of acid from D-glucose, L-arabinose, cellobiose, dulcitol (87%), D-galactose, maltose, D-mannitol, D-mannose, L-rhamnose, sucrose, trehalose, and D-xylose; acid production from mucate; nitrate reduction; and o-nitrophenyl-beta-D-galactopyranoside. Delayed positive reactions were seen in tests for arginine dihydrolase, gas from D-glucose, acid from alpha-methyl-D-glucoside, and acetate utilization. E. hormaechei was negative in tests for indole production; H2S production; phenylalanine deaminase; lysine decarboxylase; gelatin hydrolysis; acid production from D-adonitol, D-arabitol, erythritol, glycerol, i(myo)-inositol, melibiose, raffinose, and D-sorbitol; esculin hydrolysis; DNase; lipase; and tyrosine clearing. Variable reactions occurred in tests for methyl red, motility, and tartrate. All strains tested were susceptible or moderately susceptible to amikacin, azlocillin, cefotaxime, ceftazidime, ceftriaxone, chloramphenicol, gentamicin, mezlocillin, moxalactam, piperacillin, trimethoprim-sulfamethoxazole, sulfisoxazole, thienamycin, tobramycin, and trimethoprim. All strains tested were resistant to nitrofurantoin; the majority were resistant to ampicillin, cefoxitin, and cephalothin. Four isolates were from blood; most other isolates were from wounds or sputum.

The name Tatumella ptyseos gen. nov., sp. nov., is proposed for a group of organisms (previously called group EF-9) isolated from clinical sources in the United States, Canada, and Puerto Rico. A total of 68% of these isolates were from sputum specimens. T. ptyseos strains are gram-negative, oxidase-negative, fermentative rods that grow on MacConkey agar. The distinctive biochemical characteristics of 44 T. ptyseos isolates were as follows: acid but no gas from D-glucose, sucrose, and, usually (71%), D-xylose (62% delayed); no acid from lactose, maltose, or D-mannitol; negative tests for indole, urea, methyl red, gelatin, L-lysine decarboxylase, and L-ornithine decarboxylase; L-arginine dihydrolase variable; phenylalanine deaminase positive; Voges-Proskauer positive by the Coblentz method but negative by the O'Meara method; nonmotile at 36 degrees C but 66% weakly motile (30% delayed) at 25 degrees C; Simmons citrate positive at 25 degrees C (89%) but Simmons citrate negative at 36 degrees C. Deoxyribonucleic acid-deoxyribonucleic acid relatedness studies on 26 T. ptyseos strains showed that they were 80 to 100% related at 60 degrees C, which indicated that they comprise a single species. The deoxyribonucleic acid relatedness to other species within the Enterobacteriaceae was 7 to 38%. This is evidence that this species belongs in this family, is distinct from all described species and is best placed in a new genus. The T. ptyseos isolates studied were susceptible to all of the antimicrobial agents tested by broth dilution; these antimicrobial agents were amikacin, ampicillin, cephalothin, chloramphenicol, gentamicin, kanamycin, tetracycline, and tobramycin. Three striking differences between T. ptyseos and other members of the Enterobacteriaceae were its large zone of inhibition around penicillin (mean diameter 24 mm), its tendency to die on some laboratory media (such as blood agar) within 7 days, and its small number (usually one) of flagella. Strain H36 (=ATCC 33301, =CDC D6168, =CDC 9591-78) is the type strain of this new species. T. ptyseos is the type species for the genus Tatumella.

In 1983 the vernacular name Enteric Group 501 was coined for a group of strains that had been referred to our laboratory as "possible Vibrio damsela that does not require NaCl for growth." By DNA-DNA hybridization (hydroxyapatite method, 32P, 60 and 75 degrees C), six strains of Enteric Group 501 were closely related to the labeled strain 2446-81 (70 to 95% at 60 degrees C and 71 to 93% at 75 degrees C; 0 to 1% divergence). Type strains of all Aeromonas species and reference strains of six other Aeromonas DNA hybridization groups were 26 to 42% related (60 degrees C) to strain 2446-81, but type strains of 27 Vibrio and Photobacterium species, including V. damsela, were 0 to 1% (75 degrees C) related. We propose the name Aeromonas schubertii for the highly related group of seven strains formerly known as Enteric Group 501. The type strain is designated as ATCC 43700 (CDC 2446-81). Strains of A. schubertii grew well at 36 degrees C and had positive reactions at this temperature for methyl red, Voges-Proskauer (1% NaCl, Coblentz method), lysine decarboxylase, arginine dihydrolase, motility, lipase, DNase, nitrate reduction to nitrite, oxidase, and growth in nutrient broth with 0 and 1% NaCl. There was no growth in 6% NaCl or on thiosulfate-citrate-bile salts-sucrose agar. The following sugars were fermented: D-glucose, D-galactose, maltose, D-mannose, and trehalose. The following sugars were not fermented: adonitol, L-arabinose, D-arabitol, cellobiose, dulcitol, erythritol, myo-inositol, lactose, D-mannitol, melibiose, alpha-CH3-D-glucoside, raffinose, L-rhamnose, salicin, D-sorbitol, sucrose, and D-xylose. Esculin was not hydrolyzed, and the string test was negative. The mannitol-negative reaction differtiates A. schubertii from other Aeromonas species. The antibiogram of this organism is typical of other Aeromonas strains (resistance to ampicillin and carbenicillin and susceptibility to most other agents). A. schubertii strains have been isolated from abscesses (two strains), wound (one), skin (one), pleural fluid (one), and blood (two). The two blood isolates suggest clinical significance typical of other Aeromonas species , but further information is needed on this group.

Escherichia coli serotype O157:H7 has been isolated from outbreaks and sporadic cases of hemorrhagic colitis. There is convincing evidence that it can cause this diarrheal disease. Because of the interest in hemorrhagic colitis, it has become desirable to detect this particular strain in human feces, which usually contains many other strains of E. coli. Two characteristics of the incriminated E. coli O157:H7 strain have made its isolation and identification easier. It does not ferment D-sorbitol rapidly, in contrast to about 95% of other E. coli strains. In addition, the strain has H antigen 7, but only about 10% of other E. coli strains have this particular antigen. To screen for E. coli O157:H7 we devised H7 antiserum-sorbitol fermentation medium (18 g of enteric fermentation base, 10 g of D-sorbitol, 4 g of agar, 10 ml of Andrade indicator, 989 ml of water; all ingredients were mixed, autoclaved, and cooled; 1 ml of E. coli H7 antiserum was then added). Colonies to be screened were inoculated into this medium. Strains of E. coli O157:H7 gave a characteristic pattern; they did not ferment sorbitol and were immobilized in the semisolid medium because of the reaction of their flagella with the flagella antiserum. Almost all other strains of E. coli gave a different pattern; they fermented sorbitol or were not immobilized by the H7 serum or both. Strains which were presumptive positives (sorbitol negative, H7 positive) were then tested in E. coli O157 serum by slide or tube agglutination. The number of strains which were presumptive positive by H7-sorbitol medium but then were not found to be O157 was less than 1%. A second approach has been helpful in deciding which colonies to screen in H7-sorbitol medium. MacConkey-sorbitol agar (22.2 g MacConkey agar base [which contains no sugar], 10 g of D-sorbitol, 1,000 ml of water) was designed as a plating medium. Stools were plated on MacConkey agar to estimate the number of E. coli colonies and also plated on MacConkey-sorbitol agar to estimate the number of sorbitol-negative colonies of E. coli. These two approaches have proved useful for isolating and identifying E. coli O157:H7 form human feces and from feces of animals infected in the laboratory with this strain. The results suggest that media may be formulated in a similar fashion for detecting other specific strains of E. coli.

Eight cases of neonatal meningitis due to Enterobacter sakazakii (formerly known as yellow-pigmented Enterobacter cloacae) which occurred in The Netherlands during the last 6 years were investigated retrospectively. Two patients had necrotizing enterocolitis and meningitis simultaneously. Despite treatment (in most cases with ampicillin and gentamicin), the fatality rate was 75%. Strains were much more susceptible to some of the new beta-lactam antibiotics than to ampicillin. A mode of transmission other than passage through the birth canal was likely, at least for some patients. A cluster of four patient strains in one hospital had almost identical plasmid DNA profiles. However, two strains isolated from formula at the same hospital 2 days after the onset of one case had different profiles, as did the strains from patients in other hospitals.

A mixture of Shigella sonnei and Eubacterium lentum produced H2S in triple sugar iron agar; however, neither produced any in pure culture. A second culture of S. sonnei, isolated in Japan, is thought to be the first documented H2S+ Shigella.

To evaluate the clinical and epidemiologic aspects of aeromonas enteritis, we studied the cases of 34 persons nationwide from whom Aeromonas hydrophila had been isolated in large numbers from stool in 1984. Compared with 68 control subjects, these patients were more likely to have drunk untreated water, usually from private wells (odds ratio = 20.9; p less than 0.01). Eighteen of the isolates belonged to a single DNA-relatedness group of the eight described for Aeromonas species, but no clear correlation between illnesses in patients and any tested genotypic or phenotypic characteristic of recovered organisms was found. Gastrointestinal complaints tended to be chronic in infected adults and acute and severe in children. Nine patients had become ill after taking antimicrobial agents to which recovered Aeromonas species were resistant; 5 persons took antimicrobials to which their Aeromonas strains were susceptible and had alleviation or resolution of their gastrointestinal symptoms. These findings indicate that at least some Aeromonas strains are enteropathogenic for the normal host and that these organisms are acquired by drinking untreated water.

In 1972 there were only 11 genera and 26 species in the family Enterobacteriaceae. Today there are 22 genera, 69 species, and 29 biogroups or Enteric Groups. This paper is a review of all of the new organisms. It has a series of differential charts to assist in identification and a large chart with the reactions of 98 different organisms for 47 tests often used in identification. A simplified version of this chart gives the most common species and tests most often used for identification. The sources of the new organisms are listed, and their role in human disease is discussed. Fourteen new groups of Enterobacteriaceae are described for the first time. These new groups are biochemically distinct from previously described species, biogroups, and Enteric Groups of Enterobacteriaceae. The new groups are Citrobacter amalonaticus biogroup 1, Klebsiella group 47 (indole positive, ornithine positive), Serratia marcescens biogroup 1, and unclassified Enteric Groups 17, 45, 57, 58, 59, 60, 63, 64, 68, and 69.

Serratia ficaria was isolated from culture of a leg ulcer of a 44-year-old woman who had venous insufficiency and alcoholic cirrhosis. Although Pseudomonas maltophilia, P acidovorans, and Enterobacter cloacae were also present, S ficaria was isolated in large numbers and was considered to contribute significantly to this infection. This represents the third known clinical isolation of this bacterium.

Serratia marcescens rarely causes infections in newborn infants. We recently studied an epidemic caused by a multiply-resistant, serotype 014:H12 Serratia marcescens that involved 42 infants. Cutaneous abscesses at previous intravenous infusion sites occurred nine times, usually required surgical drainage, and were the most striking infections during the outbreak. Six infants developed Serratia bacteremia and two died with Serratia meningitis; 34 patients were colonized with Serratia but remained uninfected. An epidemiologic investigation of the 83 infants at risk in the nursery assessed factors predisposing them to colonization or infection with the epidemic organism. Colonization of the throat, umbilicus, gastrointestinal tract, or skin was frequent among infants as was carriage of Serratia on nursey employees' hands. Infected and colonized infants were the most important reservoir for Serratia in the nursery and cross-infection between infants readily occurred. Scalp-vein needles appeared to provide a portal of entry of Serratia in colonized infants, predisposing them to abscess formation and bacteremia.

The name Providencia rustigianii sp. nov. is proposed for a group of organisms previously known as Providencia alcalifaciens biogroup 3. By DNA hybridization, strains of P. rustigianii were 81 to 99% related to each other at 60 degrees C, but only 44 to 49% related to P. alcalifaciens biogroups 1 and 2 and 26 to 33% related to Providencia stuartii. P. rustigianii could be differentiated from P. alcalifaciens and P. stuartii by simple biochemical tests. P. rustigianii produced acid from D-galactose but not from trehalose; P. stuartii produced acid from both; and P. alcalifaciens produced acid from neither. P. rustigianii could be distinguished from Providencia rettgeri (formerly Proteus rettgeri) by urea hydrolysis and acid production from D-arabitol; P. rustigianii was negative for these two tests, but P. rettgeri was positive. Strains of P. rustiganii were 32 to 34% related to strains of P. rettgeri. Three of the 11 strains of P. rustigianii were isolated from stools, but the sources of the other isolates are unknown. Three strains (27%) were sensitive to colistin, and 82 to 100% were sensitive to ampicillin, carbenicillin, cephalothin, gentamicin, kanamycin, nalidixic acid, streptomycin, and tetracycline. Strain ATCC 33673 (CDC no. 0132-68) is the type strain for this species.

The name Koserella trabulsii is proposed for a group of Enterobacteriaceae formerly called Enteric Group 45. This group consists of 12 strains that were originally identified as atypical Hafnia alvei. K. trabulsii strains were negative for indole production, Voges-Proskauer, H2S production, urea hydrolysis, phenylalanine deaminase, and acid production from glycerol, lactose, sucrose, and D-sorbitol; they were positive for methyl red, citrate (Simmons), lysine and ornithine decarboxylases, arginine dihydrolase (negative in 1 to 2 days and positive in 3 to 7 days), and acid production from cellobiose and melibiose; and they were resistant to the Hafnia-specific bacteriophage of Guinée and Valkenburg. They were tested for DNA relatedness by the hydroxyapatite method with 32PO4-labeled DNA from the designated type strain (CDC 3349-72, ATCC 35313). The 12 strains were 87 to 99% related in 60 degrees C reactions. Relatedness of K. trabulsii to 71 DNA hybridization reference strains of representative species of Enterobacteriaceae was 4 to 37%. It was 15 to 16% related to H. alvei. All strains were susceptible to nalidixic acid, sulfadiazine, gentamicin, kanamycin, and chloramphenicol, and 83% were susceptible to nalidixic acid, sulfadiazine, gentamicin, kanamycin, and chloramphenicol, and 83% were susceptible to tetracycline. Most of the strains were resistant or intermediate to penicillin, ampicillin, carbenicillin, colistin, and cephalothin. Five of the strains were isolated from wounds, three were from the respiratory tract, and one each was from a stool, knee fluid, water, and an unknown source. The clinical significance of this organism is not known; therefore, future studies should focus on its isolation and its relationship to human disease.

A blood culture bottle from a patient with bacteremia contained both Proteus rettgeri biogroup 5 and Providencia stuartii (described in Bergey's Manual of Determinative Bactiology [8th ed., 1974] as Proteus inconstans), which had the same unusual antibiotic resistance pattern. Single colonies of this P. rettgeri biogroup 5 isolate were shown to produce urea- clones. If current taxonomy is used, the strain changed from P. rettgeri to P. stuartii in the laboratory and probably also in the patient. Urea- clones were also found in three of six other strains of P. rettgeri biogroup 5. No urea-negative clones were found in two isolates each of P. rettgeri biogroups 1 and 3. Previous data from deoxyribonucleic acid-deoxyribonucleic acid hybridization, biochemical reactions, and serological cross-reactions all have indicated that the taxon now called P. rettgeri biogroup 5 should be classified as P. stuartii urea+. We propose that this taxonomic change be made. Urease production is probably plasmid mediated in P. stuartii urea+ and can easily be lost, as shown in our case report and in three stock cultures. Urea hydrolysis will no longer be the key test for differentiating P. rettgeri from P. stuartii. Rather, acid production from trehalose, D-arabitol, adonitol, and D-mannitol will be the key tests. Whereas P. rettgeri is usually trehalose-, D-arabitol+, adonitol+, and D-mannitol+, P. stuartii has the opposite reactions.

The name Vibrio hollisae (synonym = Special Bacteriology group EF-13) is proposed for a new group of 16 strains that occurred in stool cultures of patients with diarrhea. V. hollisae is a small gram-negative rod, which is motile with a single polar flagellum. No lateral or peritrichous flagella were observed, even when it was grown on a solid medium. Sodium chloride is required for growth, so V. hollisae is a halophilic vibrio. Strains were positive (36 degrees C, 24 or 48 h) for oxidase (Kovacs), indole production, nitrate reduction to nitrite, and fermentation of D-glucose (acid, no gas), L-arabinose, D-galactose, and D-mannose. Strains were negative for the following tests often used in enteric bacteriology: lipase (corn oil); deoxyribonuclease; gelatinase; methyl red; Voges-Proskauer; utilization of citrate, acetate, and malonate; L-lysine decarboxylase (Møllers); L-ornithine decarboxylase (Møllers); L-arginine dihydrolase (Møllers); growth in KCN medium; and acid production from D-adonitol, D-arabitol, cellobiose, dulcitol, erythritol, glycerol (25% delayed positive at 7 days), i-(myo)-inositol, lactose, maltose, D-mannitol, melibiose, alpha-methyl-D-glucoside, mucate, raffinose, L-rhamnose, salicin, D-sorbitol, sucrose, trehalose, and D-xylose. None of the strains was motile (semisolid medium) at 36 degrees C at 48 h, but by 7 days 88% were motile. The strains did not grow within 2 days when plated on thiosulfate-citrate-bile salts-sucrose (TCBS) agar or MacConkey agar, but they grew on sheep blood agar and marine agar. By DNA-DNA hybridization (75 degrees C, hydroxyapatite with (32)P), V. hollisae was only 0 to 4% related to 21 named species in Vibrio and Photobacterium. The type strain is designated ATCC 33564, which has a mean guanineplus-cytosine content in DNA of 50 mol%. With the disk diffusion method V. hollisae had relatively large zones of inhibition around penicillin, ampicillin, carbenicillin, cephalothin, colistin, polymyxin B, streptomycin, kanamycin, gentamicin, tetracycline, chloramphenicol, and sulfadiazine. Future studies should focus on the isolation of this new vibrio and its ecology and relationship to human diseases.

A bacteriophage-typing schema was developed for differentiating strains of Shigella sonnei. Sixty-seven bacteriophages were obtained from other collections, and 36 bacteriophages were isolated from sewage. From these 103 bacteriophages, a provisional set of 12 was chosen by computer analysis as being the most sensitive in differentiating strains of S. sonnei isolated in the United States. The provisional schema was used to type 265 strains from different geographical areas. It divided them into 87 different lysis patterns, and all 265 strains were typable. Smooth and rough colonial variants of the same strain had different lysis patterns, so the technique was standardized to type rough colonies only. Reproducibility was difficult to obtain until all conditions were carefully standardized. Changes in results were noted even on different lot numbers of Trypticase soy agar, which was defined as the standard medium. So that the medium would not be a variable, 100 pounds (ca 453.5 kg) of the same lot number was purchased. Bacteriophage typing was very useful in differentiating strains, and work should continue on establishing a standarized schema.

In 1983, the vernacular name Enteric Group 77 was coined for a group of strains that had been referred to our laboratory as "possible Vibrio cholerae except for gas production." By DNA-DNA hybridization (hydroxyapatite, 32P), 8 of 10 strains of Enteric Group 77 were very highly related to the labeled strain 1169-83 (74 to 100% at 60 degrees C and 75 to 100% at 75 degrees C; percent divergence, 0.0 to 2.5). Type strains of six other Aeromonas species were 45 to 66% related (60 degrees C) to strain 1169-83, but type strains of 27 Vibrio species were only 2 to 6% related. The name Aeromonas veronii is proposed for the highly related group of nine strains formerly known as Enteric Group 77. The type strain is designated as ATCC 35604 (CDC 1169-83). Strains of A. veronii grew well at 36 degrees C and had positive reactions at this temperature for indole, methyl red, Voges-Proskauer, citrate, lysine and ornithine decarboxylases, DNase, lipase, and motility; the strains had negative reactions for arginine decarboxylase, H2S, urea, and malonate. The following sugars were fermented: D-glucose (acid and gas), cellobiose (seven of nine strains), D-galactose, maltose, D-mannitol, D-mannose, alpha-methyl-D-glucoside (eight of nine strains), salicin, sucrose, and trehalose. The following sugars were not fermented: adonitol, L-arabinose, D-arabitol, dulcitol, erythritol, myo-inositol, lactose, raffinose, L-rhamnose, D-sorbitol, and D-xylose. The positive ornithine decarboxylase reaction differentiates A. veronii from other Aeromonas species. The antibiogram of A. veronii is typical of other Aeromonas strains (resistance to ampicillin and carbenicillin and susceptibility to most other agents). A. veronii strains were isolated from three clinical sources: respiratory secretions of four victims of drowning or near drowning in fresh water (probably not clinically significant); infected wounds of two patients previously exposed to fresh water (unknown clinical significance); and stools from three patients with diarrhea (probably clinically significant).

Thirty-one persons nationwide from whom Plesiomonas shigelloides was isolated in large numbers from stool in 1984 were compared with 62 matched control subjects. Infection with P. shigelloides was strongly associated with eating uncooked shellfish, usually raw oysters, in the 48 hours before the onset of illness (p less than 0.00001) and with foreign travel (p less than 0.00006), usually to Mexico. Most ill persons had self-limited diarrhea with blood and mucus in stool and other clinical findings that suggested enteroinvasiveness of infecting organisms. Two patients developed their illnesses after taking ampicillin for reasons unrelated to diarrhea; plesiomonads recovered from their stools were resistant to ampicillin. Seven persons with gastrointestinal complaints had alleviation or resolution of their symptoms after taking antimicrobial agents to which recovered plesiomonads were susceptible. These findings suggest that P. shigelloides may cause enteric disease in the normal host, that it may be acquired from eating uncooked shellfish, and that it may be a cause of travelers' diarrhea.

Infections due to Serratia marcescens were studied in 23 different hospitals. A retrospective study was done in 4 hospitals; all isolates were compared by serological typing, antibiograms, bacteriocin production, and bacteriocin sensitivity. 2 of the hospitals were having cross-infection problems due to antibiotic-resistant strains, but the other 2 had little or no cross-infection. Outbreaks were studied in 19 other hospitals. 9 of these outbreaks were classified as "common source" since contaminated "sterile solutions" were incriminated as the cause in each. One hospital had a "pseudo-outbreak," in which Serratia from E.D.T.A. blood-collecting tubes contaminated blood-cultures as they were collected. All 10 of these strains from common-source outbreaks were generally sensitive to antibiotics. Outbreaks in 9 other hospitals resulted from cross-infection and were caused by strains which were very resistant to antibiotics. Guidelines for detecting outbreaks are given and control measures are suggested.

Since 1971 a lactose-positive (lac+) Salmonella typhimurium variety Copenhagen has been endemic in the city of Sao Paulo. The strain is a strong lactose fermenter and resembles Escherichia coli on primary plating media and in triple sugar iron agar. Although most isolates of the strain have uniform properties, some have slightly different antigens, antibiograms, phage types, or fermentation patterns. Most isolates have come from stools of infants under 1 year of age and are probably hospital acquired; however, other isolates are probably community acquired. Eighteen other lac+ Salmonella isolated in the United States were also studied. Most of these strains resembled E. coli on primary plates and triple sugar iron agar; thus their identification would pose a problem for most clinical laboratories. A simple procedure for detecting lac+ Salmonella mixed with lac+ E. coli consists of touching 12 colonies in succession with a straight wire and then inoculating a peptone iron agar tube. H2S production is apparent from lac+ Salmonella even if 11 E. coli and one Salmonella colony are picked. If a positive peptone iron agar tube is observed, then individual colonies are tested to rule out other strong H2S producers. The true incidence of lac+ Salmonella is unknown because they are not isolated and identified in most laboratories.

This is the first report of a naturally occurring Salmonella that is urea positive. The strain was identified as Salmonella cubana and it was typical in all biochemical, serological, and bacteriophage reactions, except that is produced urease strongly.

In this report we present clinical descriptions of 12 Hawaiian patients from whom Escherichia vulneris or E. hermannii strains were isolated. All but two patients had soft-tissue infections with multiple bacteria, particularly Staphylococcus aureus. The other two had purulent conjunctivitis associated with S. aureus and infected malignant peritonitis with multiple organisms, respectively. In none of the cases were the Escherichia spp. found in abundant quantities or considered pathogenic. In preliminary animal pathogenicity studies, 12 strains each of E. vulneris and E. hermannii failed to cause serious symptoms in 4-week-old mice when 10(7) cells were injected intraperitoneally. When 10(6) cells were used, none of these bacterial strains injected into mouse soft tissue was capable of producing persistent wound infections. Susceptibility studies of 40 strains of these bacteria to 20 different antimicrobial agents showed that they were susceptible to third-generation cephalosporins as well as to most other cephalosporins, aminoglycosides, trimethoprim, and sulfamethoxazole-trimethoprim; these strains were only marginally susceptible or resistant to penicillin, tetracycline, chloramphenicol, and nitrofurantoin.

It is widely thought that after enteric bacteric have been "formalinized" (treated with an equal volume of 0.6% formalin) for 1 h, the bacteria become "antigens" and are no longer viable. None of the 27 cultures of Salmonella and other Enterobacteriaceae were entirely killed within 1 h after formalin was added, but all 27 were reduced from 10(9) viable cells per ml to less than 10(2) per ml within 7 h. Thus, mouth pipetting of cultures formalinized for only 1 h is a possible infection hazard.

Clinical microbiologists normally identify important isolates to the level of species and determine their susceptibility to antibiotics. These activities generate a species identification and provide some differentiation below the level of species in the form of a biotype and an antibiogram. Most other typing methods should be reserved for special studies or to investigate possible infection problems or outbreaks. Specialized techniques should usually be done in reference laboratories. These include serotyping, (complete antigenic analysis), bacteriophage susceptibility, and bacteriocin production or susceptibility.

Kluyvera is proposed as a new genus for the group of organisms formerly known as Enteric Group 8 (synonym = API group 1). Strains of Kluyvera share the properties of most members of the family Enterobacteriaceae: they are gram-negative rods, motile with peritrichous flagella, catalase positive, and oxidase negative; they grow on MacConkey agar, ferment D-glucose with the production of acid and gas, and are susceptible to many antibiotics. Strains are usually indole positive, methyl red positive, Voges-Proskauer negative, citrate positive, H2S (triple sugar iron) negative, urea negative, phenylalanine deaminase negative, lysine decarboxylase positive, arginine dihydrolase negative, and ornithine decarboxylase positive. Kluyvera strains ferment many of the sugars and polyhydroxyl alcohols used in identification. By deoxyribonucleic acid-deoxyribonucleic acid hybridization, strains of Kluyvera were divided into three groups. Kluyvera ascorbata is proposed as the type species for the genus. Most strains of K. ascorbata have been isolated from clinical specimens. K. cryocrescens is proposed as the second species. It was occasionally isolated from clinical specimens, but it was isolated more commonly from the environment. Kluyvera species group 3 was heterogeneous, but was distinct from the two named species by deoxyribonucleic acid hybridization. This group was rare, so no species name will be proposed at this time. K. ascorbata can be differentiated from K. cryocrescens by its positive ascorbate test, inability to grow at 5 degrees C in a refrigerator, and smaller zones of inhibition around carbenicillin and cephalothin disks. The test normally used for identification does not clearly differentiate these two species. Kluyvera species are probably infrequent opportunistic pathogens. The most common source is sputum, where they are probably not clinically significant. Five strains have been from blood cultures. More information is needed about the incidence and clinical significance of the genus Kluyvera.

From 1974 through 1981, 4,089 isolates of Salmonella typhi were phage typed at the Centers for Disease Control and nine regional laboratories in the United States. The most prevalent types were degraded Vi (27%), E1 (20.6%), A (9.8%), C1 (5.7%), untypable Vi (3.5%), W form (3.5%), D1 (3.4%), B3 (3.4%), and F1 (2.4%). There were less than 2% of each of the remaining types. The distribution of phage types for this time period was similar to that seen in the periods 1966-1969 and 1970-1973, except that phage type B3 was one of the 10 most prevalent types in 1974-1981 but was not seen in 1966-1973. Phage typing is presently the most valuable laboratory tool for differentiation of strains of S. typhi in epidemiological studies.

Strains formerly classified as the aerogenic (gas-producing) biogroup of Vibrio fluvialis were shown by DNA relatedness to be a separate species. The species was named Vibrio furnissii sp. nov. (type strain ATCC 35016 = CDC B3215). Three strains of V. furnissii were 79% or more related to the type strain of V. furnissii and about 50% related to the type strain of V. fluvialis. V. fluvialis strains were 40 to 64% related to the type strain of V. furnissii. Divergence in related sequences was only 0.0 to 1.5% among strains of V. furnissii and among strains of V. fluvialis but was 5.0 to 8.0% in interspecific reactions between V. fluvialis and V. furnissii. V. furnissii was aerogenic (produced gas from the fermentation of carbohydrates), whereas V. fluvialis was anaerogenic (did not produce gas from the fermentation of carbohydrates). Another test of some help in differentiating the two species was fermentation of L-rhamnose (57% positive for V. furnissii and negative for V. fluvialis). In addition to the reactions above, V. furnissii is distinguished from other salt-requiring vibrios on the basis of its positive reactions in tests for Møller L-arginine, L-arabinose, maltose, and D-mannitol and its negative reactions for Møller L-lysine and L-ornithine, lactose, and Voges-Proskauer. V. furnissii has been isolated from patients with acute gastroenteritis in at least two outbreaks of food poisoning; its role as a cause of diarrhea needs further study.

Interhospital spread appeared to be responsible for a large epidemic of infections due to a strain of Serratia marcescens that was resistant to all currently available parenteral antibiotics. Between April 1, 1973 and January 1, 1975, 210 patients in four geographically separate hospitals in Nashville, Tennessee, were infected with the epidemic strain; 21 patients were bacteremic and eight died. Catheter-associated urinary tract infection accounted for the majority of isolates, and broad-spectrum antibiotic exposure appeared to promote the acquisition of the epidemic strain. The serotype (O1:H7) and phage type (186) of the organism were identical in all four hospitals, but background, sensitive strains of S. marcesens yielded a variety of other serotypes. Carriage on the hands of hospital personnel was implicated as the mode of spread within the hospital and apparently was the mode of transmission between the hospitals. Antibiotic resistance was largely episomally mediated, but resistance to gentamicin, cephalothin, and colistin was not transferable.

In 1972 and 1973 a nationwide outbreak of typhoid fever occurred in Mexico. The responsible strain of Salmonella typhi had a characteristic pattern of phage lysis, resembling the type A pattern, referred to as degraded Vi(A), and was resistant to chloramphenicol and other antimicrobial agents in vitro and in vivo. Eighty cases of infection with strains of S. typhi that were related to the Mexican epidemic strain were reported in the United States. The epidemic in Mexico subsided in mid-1973, and no further cases of typhoid fever due to chloramphenicol-resistant organisms were reported in the United States. Infections with chloramphenicol-sensitive strains of S. typhi with the phage lysis pattern of degraded (Vi(A) occurred in association with travel in Mexico before and after the height of the epidemic in Mexico. Although typhoid fever due to chloramphenicol-resistant organisms has not been reported in the United States since the subsidence of the Mexican epidemic, testing of isolates of S. typhi for antibiotic sensitivity is recommended because of the continued existence of resistant strains elsewhere.

An outbreak caused by a highly resistant strain of Salmonella typhimurium occurred in a nursery at a university medical center. The outbreak strain, which was resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole, was apparently imported from the Far East by a Cambodian refugee. The five patients involved had severe underlying diseases, and bacteremia and meningitis developed in one of these patients. The only reservoir identified was the gastrointestinal tracts of the infected patients, and infection was probably transmitted by the contaminated hands of hospital personnel. The outbreak was rapidly brought under control by isolating cases outside of the nursery and by instituting enteric precautions for infants who remained in the nursery. When compared by disk diffusion susceptibility tests with 353 strains of S. typhimurium tested at the Centers for Disease Control, the imported strain had a unique antibiogram. Bacteriophage typing of the strains revealed that all were untypable; this, in itself, was a good marker, because only 5 to 10% of S. typhimurium isolates in this country have this property. Agarose gel electrophoresis of isolates from the five patients revealed an identical plasmid banding pattern consisting of three large and three small plasmids. Highly resistant strains of S. typhimurium imported from the Far East may spread rapidly when introduced into a hospital nursery. Prompt institution of control measures may limit the outbreak and prevent systemic infections for which there are few effective therapeutic agents.

Yersinia enterocolitica is listed as a single species in Bergey's Manual of Determinative Bacteriology, but has recently been split into "true" Y. enterocolitica, Y. kristensenii, Y. intermedia, and Y. frederiksenii. From 48 bacteriophages isolated from raw sewage, 24 were chosen as being the most useful for differentiating strains within the four Yersinia species. The composite set of 24 phages typed 92% of 236 Y. enterocolitica strains, 100% of 16 Y. kristensenii strains, 97% of 29 Y. frederiksenii strains, and 90% of 20 Y. intermedia strains. The most common phage type in any of the groups contained 22% of the strains tested, but most of the phage types contained greater than 5% of the strains. The new typing schema was tested in three outbreaks of Y. enterocolitica, and the results agreed well with serotyping and epidemiological findings. In the same outbreaks, biotyping (API 20E profiles; Analytab Products, Plainview, N.Y.) and antibiograms were less reliable markers and probably should be used only in conjunction with serotyping or phage typing or both. Caution should be used in identifying cultures of Y. frederiksenii and Y. intermedia with the API 20E system, since the tests at 37 degrees C for L-rhamnose and melibiose fermentation are often delayed past 24 h, which is the cut-off point for the final reading in the API system. There were distinct differences in the susceptibilities of Y. enterocolitica and Y. kristensenii to ampicillin, carbenicillin, and cephalothin, which adds further support for classifying the latter as a separate species.

The isolation of Pseudomonas aeruginosa, serogroup 11, from the skin lesions of bathers and from public whirlpools during outbreaks of pool-associated rash illness raises the question of whether the association is an etiologic one and if so what accounts for it. We suggest that a particular environmental adaptation of some strains of Pseudomonas and certain virulence factors they possess may enhance their pathogenic potential.