Cefazolin susceptibility of coagulase-negative staphylococci (CoNS) causing late-onset neonatal bacteraemia.

BACKGROUND: CoNS bacteraemia causes significant neonatal morbidity. Previous work has suggested that ß-lactam antibiotics vary in their binding affinity to PBP2a (produced by the mecA gene) present in most CoNS. OBJECTIVES: We evaluated cefazolin MICs for CoNS isolated in an Australian neonatal ICU (NICU) and correlated them with isolate genotype and phenotype. METHODS: Significant blood isolates from 2009 to 2017 were speciated and underwent broth microdilution testing for cefazolin, cefoxitin, oxacillin and flucloxacillin. Correlation with mecA presence and PBP2a expression was evaluated. A selection of Staphylococcus capitis isolates underwent WGS. RESULTS: The CoNS (n = 99) isolates were confirmed as S. capitis (n = 57), Staphylococcus epidermidis (n = 32), Staphylococcus haemolyticus (n = 2) and Staphylococcus warneri (n = 8). The MIC of cefazolin was ≤2 mg/L for 30% of isolates and 75% had an MIC of ≤8 mg/L (MIC90 = 16 mg/L). This contrasted with MIC90s of cefoxitin, oxacillin and flucloxacillin, which were all ≥32 mg/L. WGS found a number of S. capitis isolates closely related to the globally established NRCS-A clone. CONCLUSIONS: CoNS displayed distinctly lower MIC values of cefazolin than of other agents tested. MIC variation may be related to binding affinity of PBP2a or regulation of expression of mecA by mecR1-mecI functional genes. Further, NRCS-A S. capitis strains were present in this Australian NICU before and after the unit underwent physical relocation, which raised questions about a common environmental source. It is considered justified to conduct a randomized clinical trial that assesses cefazolin versus vancomycin for management of late-onset neonatal sepsis.

Mobile phones and computer keyboards: unlikely reservoirs of multidrug-resistant organisms in the tertiary intensive care unit.

Few studies have used molecular epidemiological methods to study transmission links to clinical isolates in intensive care units. Ninety-four multidrug-resistant organisms (MDROs) cultured from routine specimens from intensive care unit (ICU) patients over 13 weeks were stored (11 meticillin-resistant Staphylococcus aureus (MRSA), two vancomycin-resistant enterococci and 81 Gram-negative bacteria). Medical staff personal mobile phones, departmental phones, and ICU keyboards were swabbed and cultured for MDROs; MRSA was isolated from two phones. Environmental and patient isolates of the same genus were selected for whole genome sequencing. On whole genome sequencing, the mobile phone isolates had a pairwise single nucleotide polymorphism (SNP) distance of 183. However, >15,000 core genome SNPs separated the mobile phone and clinical isolates. In a low-endemic setting, mobile phones and keyboards appear unlikely to contribute to hospital-acquired MDROs.

Identification of the bacterium associated with haemorrhagic septicaemia in rainbow trout as Hafnia alvei.

An unidentified bacterium responsible for epizootic haemorrhagic septicaemic disease in rainbow trout was recently described. This organism exhibited some antigenic similarity to Brucella abortus and to Yersinia ruckeri and was presumed to belong to the family Enterobacteriaceae. Further biochemical characterization and DNA relatedness studies showed that pathogenic fish strains are Hafnia alvei.

Pyrazinamidase, CR-MOX agar, salicin fermentation-esculin hydrolysis, and D-xylose fermentation for identifying pathogenic serotypes of Yersinia enterocolitica.

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.

Yersinia enterocolitica: a frequent seasonal stool isolate from children at an urban hospital in the southeast United States.

From 1 December 1988 through 28 February 1991, 7,290 rectal swab specimens received in our laboratory were screened for Yersinia enterocolitica. A total of 76 patients had Y. enterocolitica isolated from their stool samples. Of these patients, 59 (77.6%) were 12 months old or younger. Y. enterocolitica was second only to Salmonella spp. in this age group. Routine screening for Y. enterocolitica may be warranted in hospitals serving large pediatric populations.

Yersinia enterocolitica pharyngitis.

During the investigation of a large multistate outbreak of milk-borne yersiniosis, 14 patients who presented with pharyngitis had Yersinia enterocolitica isolated from the throat. Their illness was characterized by sore throat and fever without enteritis; 3 needed hospitalization. All patients tested had leukocytosis and an elevated convalescent-phase serum titer against the outbreak strain. In contrast to patients with enteritis, who were children, all patients with pharyngitis were adults. Thus, Y. enterocolitica may be responsible for some sporadic cases of pharyngitis in which the throat culture is negative for other pathogens.

Yersinia enterocolitica O:3: an emerging cause of pediatric gastroenteritis in the United States. The Yersinia enterocolitica Collaborative Study Group.

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.

Increase in antibiotic resistance among isolates of Salmonella in the United States, 1967-1975.

To study temporal changes in the antibiotic resistance of Salmonella in the United States, a study design similar to that of a 1967 study was used to determine the antibiotic sensitivity of 754 human nontyphoid Salmonella isolates sent to the Center for Disease Control, Atlanta, Georgia, in 1975. The frequency of resistance to one or more of the same nine antibiotics used in both studies increased significantly during the eight years in Salmonella typhimurium (40%-59%; P = 0.004), other serotypes (14%-23%; P = 0.001), and all serotypes combined (21%-31%; P < 0.001). The increase in frequency of resistance was significant for streptomycin (P = 0.022), sulfonamides (P < 0.001), ampicillin (P < 0.001), and kanamycin (P < 0.001). No chloramphenicol-resistant isolates were found in the 1967 study, whereas six isolates (0.8%) were resistant in 1975. The frequency of strains resistant to six or more antibiotics increased greatly (0.8%-5.0%; P < 0.001). These data document a continuing increase in antimicrobial resistance among Salmonella isolates.

Xenorhabdus luminescens (DNA hybridization group 5) from human clinical specimens.

An unusual isolate from a human leg wound was identified as Xenorhabdus luminescens. This finding led to the discovery or isolation of four additional strains, two from blood and two from wounds. Three of the five strains were from patients in San Antonio, Tex. Three strains were studied by DNA-DNA hybridization (S1 nuclease-trichloroacetic acid method) and were 77 to 100% related to each other, 34% related to the type strain of X. luminescens, 35 to 40% related to three of Grimont's other DNA hybridization groups of X. luminescens, and 9% related to the type strain of Xenorhabdus nematophilus. The new group of five strains was designated X. luminescens DNA hybridization group 5. All five strains were very inactive biochemically and fermented only D-glucose and D-mannose. The key reactions for recognizing this new organism are yellow pigment production, negative test for nitrate reduction to nitrite, weak bioluminescence (10 to 15 min of dark adaptation is required to see the weak light produced), and a unique hemolytic reaction on sheep blood agar plates incubated at 25 degrees C. Two case histories of strains from wounds are given; these suggest that X. luminescens DNA hybridization group 5 may be a new bacterial agent that causes wound infections. The two cases of wound infection, along with the two blood isolates, suggest that the new organism is clinically significant.

Occurrence and distribution of serotypes of the Arizona subgroup of Salmonella strains in the United States from 1967 to 1976.

The Salmonella Arizona subgroup contains gram-negative enteric bacteria that are closely related to other salmonellae biochemically, serologically, and genetically. Although the Arizona subgroup may be isolated from a wide variety of nonhuman and human sources, the arizonae are uncommonly recognized as human pathogens, and surprisingly little is known about their epidemiology. From 1967 through 1976, the Centers for Disease Control received 858 Arizona subgroup cultures from human and nonhuman sources representing 143 different serotypes in 33 somatic groups; several serotypes had not been previously reported. The 374 cultures from humans represent 71 different serotypes; extraintestinal isolates were present in 31 (44%) serotypes. Compared with data from a previous 20 years of surveillance, the proportion of Arizona subgroup strains isolated from stools, blood, and other sites was remarkably stable, but several serotypes showed marked changes in their frequency of isolation. In total, the ratio of extraintestinal to intestinal isolates was 0.37, but marked serotype-specific variation was noted, suggesting differences in virulence associated with serotype.

Koserella trabulsii, a new genus and species of Enterobacteriaceae formerly known as Enteric Group 45.

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.

Moellerella wisconsensis, a new genus and species of Enterobacteriaceae found in human stool specimens.

The name Moellerella wisconsensis is proposed for a group of the family Enterobacteriaceae previously called enteric group 46. The species name, wisconsensis, was coined because six of the nine strains were isolated in Wisconsin. M. wisconsensis strains were negative for indole production, Voges-Proskauer, H2S production, urea, phenylalanine deaminase, lysine and ornithine decarboxylases, arginine dihydrolase, gas production from D-glucose, acid production from trehalose, and motility; the strains were positive for methyl red, citrate (Simmons), and acid production from lactose and raffinose and resistant to colistin. DNAs from five strains of M. wisconsensis were highly related (80 to 93% in reactions assayed on hydroxyapatite at 60 degrees C and 78 to 97% at 75 degrees C) to 32P-labeled DNA of the proposed type strain (CDC 2896-78, ATCC 35017). Labeled DNA from this type strain was only 2 to 32% related (at 60 degrees C) to DNA from 49 strains of named and unnamed species of Enterobacteriaceae. Eight of nine M. wisconsensis strains were isolated from human stool samples. Clinical information on one strain was available, and it was found to be associated with a case of diarrhea. On MacConkey agar, colonies of M. wisconsensis were bright red with precipitated bile around them and thus were indistinguishable from Escherichia coli colonies. Future studies should focus on the isolation of this new organism and its relationship to human disease.

Leminorella, a new genus of Enterobacteriaceae: identification of Leminorella grimontii sp. nov. and Leminorella richardii sp. nov. found in clinical specimens.

Leminorella is proposed as a new genus for the group of Enterobacteriaceae formerly known as Enteric Group 57. Strains of Leminorella gave positive tests for H2S production, acid production from L-arabinose and D-xylose, and tyrosine clearing; they were negative for indole production, Voges-Proskauer, urea hydrolysis, phenylalanine deaminase, motility, gelatin liquefaction, lysine and ornithine decarboxylases, arginine dihydrolase, growth in KCN, and acid production from adonitol, D-arabitol, cellobiose, erythritol, D-galactose, myo-inositol, lactose, maltose, D-mannitol, D-mannose, melibiose, alpha-CH3-glucoside, raffinose, L-rhamnose, salicin, D-sorbitol, sucrose, and trehalose. By DNA hybridization, strains of Leminorella were only 3 to 16% related to other Enterobacteriaceae and were divided into three groups. Leminorella grimontii is proposed as the type species for the genus and strain CDC 1944-81, ATCC 33999, is designated as the type strain. There were four strains of L. grimontii from stool specimens and two from urine specimens. L. richardii is proposed as the name for the second species (type strain, CDC 0978-82, ATCC 33998). All four L. richardii strains were from stool specimens. L. grimontii can be distinguished from L. richardii because it produces gas from glucose (100%) and acid from dulcitol (83%) and is methyl red positive (100%). One strain, CDC 3346-72, was more related to L. grimontii by DNA hybridization than to L. richardii, but the lower relatedness to both of these species indicated that it may be a third species. Biochemically it could not be distinguished from L. grimontii. All Leminorella strains were resistant (no zone of inhibition) to ampicillin, carbenicillin, and cephalothin. Some of the Leminorella strains were sent to us for Salmonella serotyping, and two reacted weakly in Salmonella antisera. The clinical significance of Leminorella is unknown.

Kluyvera, a new (redefined) genus in the family Enterobacteriaceae: identification of Kluyvera ascorbata sp. nov. and Kluyvera cryocrescens sp. nov. in clinical specimens.

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.

Biochemical identification of new species and biogroups of Enterobacteriaceae isolated from clinical specimens.

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.