Rettgeri Strains Research Articles

Epidemiological and molecular study of Providencia rettgeri outbreak at a university hospital during the COVID-19 reference center.

In 2014, Brazil detected New Delhi metallo-β-lactamase (NDM)-producing Enterobacterales from a Providencia rettgeri isolate obtained through surveillance swabs in the Southern region. Subsequently, various species have reported several NDM enzymes. However, comprehensive data on the current epidemiology of NDM-producing P. rettgeri in Brazil remains limited. This study, aimed to provide a detailed characterization of the phenotypic, genotypic, and epidemiological profile of clinical isolates of P. rettgeri NDM. From April 2020 to December 2022, 18 carbapenem-resistant P. rettgeri strains, previously identified using Vitek2®, were isolated at the University Hospital of Londrina. Resistance and virulence genes were assessed through genetic analysis using ERIC PCR and NextSeq (Illumina) sequencing. Statistical analysis was conducted using SPSS version 2.0. Genomic analysis confirmed the presence of β-lactamase blaNDM-1 and blaOXA-1. All isolates showed the presence of the NDM encoding gene and genetic similarity above 90% between isolates. Clinical parameters of patients infected with P. rettgeri exhibited significant association with mechanical ventilation, prior use of carbapenems, and polymyxins. We also report a significant association between P. rettgeri infection and death outcome. This study characterizes NDM-1 metallo-β-lactmases isolates, among P. rettgeri isolates from patients at the University Hospital (HU), during the COVID-19 pandemic. The emergence of this novel resistance mechanism among P. rettgeri poses a significant challenge, limiting the therapeutic options for infections in our hospital.

Analysis of resistance genes of carbapenem-resistant Providencia rettgeri using whole genome sequencing

ObjectiveThis study aimed to investigate the clinical infection characteristics and analyze the resistance gene carrying status of carbapenem-resistant Providencia rettgeri via whole genome sequencing (WGS).MethodsCarbapenem-resistant P. rettgeri were collected from clinical patients between January 2020 and December 2021, and their susceptibility to 19 antimicrobial drugs was determined using the VITEK 2 Compact system and Kirby–Bauer (KB) disk diffusion method. The Illumina platform was used to perform WGS of the P. rettgeri isolates, and the resistance genes carried by the Carbapenem-resistant P. rettgeri strains were detected via ABRicate software. The phylogenetic tree was constructed by thirty-four strains including twenty-eight strains downloaded from NCBI database and the carbapenem-resistant six P. rettgeri strains in this study. Which based on genomic single nucleotide polymorphism (SNP) to understand the affinities of the carbapenem-resistant P. rettgeri strains.ResultsSix carbapenem-resistant P. rettgeri strains were isolated from five different clinical departments using the blood, urine, sputum, and secretion specimens. These infected patients are middle-aged and elderly people with a history of severe trauma, tumors, hypertension, and various other underlying diseases, and invasive procedures. Antimicrobial sensitivity testing showed that all strains presented resistance to ampicillin-sulbactam, ceftazidime, ciprofloxacin, levofloxacin, and ertapenem, whereas they exhibited full susceptibility to cefepime and amikacin. Most strains demonstrated high resistance to β-lactams, aminoglycosides, and sulfonamides. Thirty-five resistance genes were identified by ABRicate. All carbapenem-resistant P. rettgeri strains carried aminoglycoside, fluoroquinolone, chloramphenicol, rifampicin, sulfonamide, and β-lactam resistance genes, and most importantly, all strains possessed the carbapenem resistance gene blaNDM−1. The six P. rettgeri strains in this study and the 28 carbapenem-resistant P. rettgeri strains from the NCBI database were divided into four evolutionary groups. The WF3643, WF3849, WF3822, and WF3821 strains in this study were in the same evolutionary group (clade A), while the closely related WF3099 and WF3279 strains were in different evolutionary groups (clade B and clade D), respectively. The WF3099 strain was distantly related to the other five strains.ConclusionCarbapenem-resistant P. rettgeri strains were mostly isolated from middle-aged and older patients with a history of surgery or serious underlying diseases, and they were found to cause multisystem infections. All Carbapenem-resistant P. rettgeri strains in this study carried blaNDM−1 and multiple antimicrobial drug resistance genes. Furthermore, the P. rettgeri strains in this study were closely related, suggesting the possibility of nosocomial infections. Therefore, our study highlights the need for research on P. rettgeri to control the spread of these nosocomial infections.

Conjugation of plasmid harboring bla NDM-1 in a clinical Providencia rettgeri strain through the formation of a fusion plasmid.

Providencia rettgeri has recently gained increased importance owing to the New Delhi metallo-β-lactamase (NDM) and other β-lactamases produced by its clinical isolates. These enzymes reduce the efficiency of antimicrobial therapy. Herein, we reported the findings of whole-genome sequence analysis and a comprehensive pan-genome analysis performed on a multidrug-resistant P. rettgeri 18004577 clinical strain recovered from the urine of a hospitalized patient in Shandong, China, in 2018. Providencia rettgeri 18004577 was found to have a genome assembly size of 4.6 Mb with a G + C content of 41%; a circular plasmid p18004577_NDM of 273.3 Kb, harboring an accessory multidrug-resistant region; and a circular, stable IncT plasmid p18004577_Rts of 146.2 Kb. Additionally, various resistance genes were identified in its genome, including bla NDM-1, bla OXA-10, bla PER-4, aph(3')-VI, ant(2'')-Ia, ant(3')-Ia, sul1, catB8, catA1, mph(E), and tet. Conjugation experiments and whole-genome sequencing revealed that the bla NDM-1 gene could be transferred to the transconjugant via the formation of pJ18004577_NDM, a novel hybrid plasmid. Based on the genetic comparison, the main possible formation process for pJ18004577_NDM was the insertion of the [ΔISKox2-IS26-ΔISKox2]-aph(3')-VI-bla NDM-1 translocatable unit module from p18004577_NDM into plasmid p18004577_Rts in the Russian doll insertion structure (ΔISKox2-IS26-ΔISKox2), which played a role similar to that of IS26 using the "copy-in" route in the mobilization of [aph(3')-VI]-bla NDM-1. The array, multiplicity, and diversity of the resistance and virulence genes in this strain necessitate stringent infection control, antibiotic stewardship, and periodic resistance surveillance/monitoring policies to preempt further horizontal and vertical spread of the resistance genes. Roary analysis based on 30 P. rettgeri strains pan genome identified 415 core, 756 soft core, 5,744 shell, and 12,967 cloud genes, highlighting the "close" nature of P. rettgeri pan-genome. After a comprehensive pan-genome analysis, representative biological information was revealed that included phylogenetic distances, presence or absence of genes across the P. rettgeri bacteria clade, and functional distribution of proteins. Moreover, pan-genome analysis has been shown to be an effective approach to better understand P. rettgeri bacteria because it helps develop various tailored therapeutic strategies based on their biological similarities and differences.

CASE SERIES OF EMERGING NOSOCOMIAL MULTIPLE DRUG RESISTANT PATHOGEN PROVIDENCIA RETTGERI CAUSING URINARY TRACT INFECTION

We report Case Series of Emerging Nosocomial Multiple Drug Resistant Pathogen Providencia rettgeri causing Urinary Tract Infections. The most common cause of catheter-associated urinary tract infections (CAUTI), especially with long-term indwelling urinary catheters in elders, are P. rettgeri and P. stuartii. We are reporting 4 cases of UTI, which are hospital-acquired and CAUTI. These cases are admitted to MICU for treatment purposes and later develop fever spikes after a few days and are evaluated and urine culture showed multi-drug-resistant Providencia rettgeri by VITEK. The empirical therapy was discontinued, managed with fosfomycin, and discharged later with follow-up. The various reports showed P. rettgeriis susceptible for amikacin, gentamicin, tobramycin and ciprofloxacin. In our case series, we isolated multi-drug-resistant strains of P. rettgeri that showed resistance to piperacillin-tazobactam, cefuroxime, ceftriaxone, cefepime, ertapenem, imipenem, meropenem, gentamicin, tobramycin, ciprofloxacin, tigecycline, amikacin, colistin and sensitive only to fosfomycin. The significance of P. rettgeri in association with catheter-related bloodstream infections (CRBSI) and catheter-associated urinary tract infections (CAUTI) was unclear. Hence isolation of Providencia species twice from the clinical samples was considered for association with catheter infections. The proper selection of empirical antimicrobials, antibiotic sensitivity testing, avoiding misuse of antibiotics and implementing proper drug holiday and local antibiotic policy are considered appropriate combination protocol for managing emerging multi-drug-resistant nosocomial Providencia rettgeri strains.

Identification and Characterization of vB_PreP_EPr2, a Lytic Bacteriophage of Pan-Drug Resistant Providencia rettgeri

Providencia rettgeri is an emerging opportunistic Gram-negative pathogen with reports of increasing antibiotic resistance. Pan-drug resistant (PDR) P. rettgeri infections are a growing concern, demonstrating a need for the development of alternative treatment options which is fueling a renewed interest in bacteriophage (phage) therapy. Here, we identify and characterize phage vB_PreP_EPr2 (EPr2) with lytic activity against PDR P. rettgeri MRSN 845308, a clinical isolate that carries multiple antibiotic resistance genes. EPr2 was isolated from an environmental water sample and belongs to the family Autographiviridae, subfamily Studiervirinae and genus Kayfunavirus, with a genome size of 41,261 base pairs. Additional phenotypic characterization showed an optimal MOI of 1 and a burst size of 12.3 ± 3.4 PFU per bacterium. EPr2 was determined to have a narrow host range against a panel of clinical P. rettgeri strains. Despite this fact, EPr2 is a promising lytic phage with potential for use as an alternative therapeutic for treatment of PDR P. rettgeri infections.

Genomic analysis of a multidrug-resistant clinical Providencia rettgeri (PR002) strain with the novel integron ln1483 and an A/C plasmid replicon.

Whole-genome sequence analysis was performed on a multidrug-resistant Providencia rettgeri PR002 clinical strain isolated from the urine of a hospitalized patient in Pretoria, South Africa, in 2013. The resistome, mobilome, pathogenicity island(s), as well as virulence and heavy-metal resistance genes of the isolate, were characterized using whole-genome sequencing and bioinformatic analysis. PR002 had a genome assembly size of 4,832,624bp with a GC content of 40.7%, an A/C2 plasmid replicase gene, four integrons/gene cassettes, 17 resistance genes, and several virulence and heavy metal resistance genes, confirming PR002 as a human pathogen. A novel integron, In1483, harboring the gene blaOXA-2 , was identified, with other uncharacterized class 1 integrons harboring aacA4cr and dfrA1. Aac(3')-IIa and blaSCO-1 , as well as blaPER-7 , sul2, and tet(B), were found bracketed by composite Tn3 transposons, and IS91, IS91, and IS4 family insertion sequences, respectively. PR002 was resistant to all antibiotics tested except amikacin, carbapenems, cefotaxime-clavulanate, ceftazidime-clavulanate, cefoxitin, and fosfomycin. PR002 was closely related to PR1 (USA), PRET_2032 (SPAIN), DSM_1131, and NCTC7477 clinical P. rettgeri strains, but not close enough to suggest it was imported into South Africa from other countries. Multidrug resistance in P. rettgeri is rare, particularly in clinical settings, making this case an important incident requiring urgent attention. This is also the first report of an A/C plasmid in P. rettgeri. The array, multiplicity, and diversity of resistance and virulence genes in this strain are concerning, necessitating stringent infection control, antibiotic stewardship, and periodic resistance surveillance/monitoring policies to preempt further horizontal and vertical spread of these resistance genes.

Genome-based insights into the resistomes and mobilomes of two Providencia rettgeri strains isolated from wound infections in Madagascar

A molecular analysis was performed of two Providencia rettgeri (P. rettgeri) strains (Pr 297 and Pr 269) collected in 2007 and 2009 from wound swabs of patients admitted to the intensive care units at Joseph Ravoangy Andrianavalona hospital and the Military Hospital in Antananarivo, Madagascar. The two P. rettgeri isolates were subjected to susceptibility testing. Whole genome sequencing was performed to characterise the antibiotic resistance genes, genomic islands and mobilomes (integrons, plasmids and insertion sequences). All isolates were found to be multidrug-resistant. Antibiotic-resistant genes described were amongst eight different classes of antimicrobial agents. Thirty insertion sequences and twelve genomic islands were predicted in each genome. Class 1 and class 2 integrons were found in both genomes, with gene cassette regions encompassing arr-2 - cmlA5 - blaOXA-10 - ant (3")-Ia and dfrA1 - sat2 - ant (3")-Ia - orfX, respectively. IncA/C2, ColM and ColE1-like plasmids were described harbouring blaCMY-30, qnrD and aac(6')-Ib-cr4 genes, respectively. Phylogenetic analysis showed that Pr 297 and Pr 269 isolates were genetically identical and clustered with P. rettgeri strains described in the USA and Spain. It is believed that this is the first molecular characterisation of wound infection pathogens from Madagascan patients and the first description of P. rettgeri co-producing CMY-30, OXA-10 and AAC(6')-Ib-cr4 enzymes. The diversity of the resistance determinants and mobile genetic elements was probably due to extensive horizontal gene transfer events, highlighting the need to conduct further molecular monitoring studies to understand the genomic plasticity of resistant bacteria in Madagascan hospitals.

Epidemiological characteristics of blaNDM-1 gene in Enterobacteriaceae strains circulating in China during 2013 to 2014

Objective To investigate the epidemiological characteristics of blaNDM-1 gene (encoding New Delhi metallo-β-lactamase 1) in Enterobacteriaceae strains circulating in China during July 2013 to June 2014. Methods A total of 2 577 Enterobacteriaceae strains were collected from 19 Class A tertiary hospitals nationwide by China Antimicrobial Resistance Surveillance Trial (CARST). PCR was used to detect the presence of blaNDM-1 gene in those Enterobacteriaceae strains. For blaNDM-1-positive strains, Analytical Profile Index (API) strips and 16S rRNA analysis were used to identify bacterial genus and species. Antibiotic susceptibilities were assessed by detecting minimum inhibitory concentrations (MIC) against them with two-fold agar dilution test. Multilocus-sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) were performed for homology analysis. Results Among the 2 577 strains, 24 from 8 different provinces and cities carried the blaNDM-1 gene, including 11 Klebsiella pneumoniae strains, 4 Enterobacter cloacae strains, 3 Providencia rettgeri strains, 2 Escherichia coli strains, 2 Citrobacter freundii strains, 1 Klebsielia Oxytoca and 1 Serratia marcescens, and all of them were multidrug-resistant (MDR). ST17 (5, 45.45%) and ST20 (3, 27.27%) were the predominant sequence types of Klebsiella pneumoniae strains. Strains of the same STs were clonally related. PFGE analysis showed that 3 Providencia rettgeri strains isolated in Nanjing belonged to the same clone. Conclusion The positive rate of blaNDM-1 gene in Enterobacteriaceae strains isolated during 2013 to 2014 is 0.93%, indicating a significant increase as compared with that during 2009 to 2010 (0%) and 2011 to 2012 (0.32%). The present study first reports the strain of Serratia marcescens harboring NDM-1 gene in China. NDM-1-producing strains are highly resistant to multiple drugs. Most of the NDM-1-producing Enterobacteriaceae strains were Klebsiella pneumoniae strains (45.83%) warranting special attention as there is a risk of endemic outbreak. Key words: Beta-lactamase NDM-1; Enterobacteriaceae; Epidemiology

Nosocomial dissemination of plasmids carrying blaTEM-24, blaDHA-1, aac(6′)-Ib-cr, and qnrA6 in Providencia spp. strains isolated from a Tunisian hospital

The aim of this study is to report the emergence of IncA/C conjugative plasmids harboring blaTEM-24, blaDHA-1, qnrA6, and aac(6′)-Ib-cr genes among Providencia spp. isolates recovered in 2008 in Tunisia. The double-disk synergy test confirmed the phenotype extended-spectrum β-lactamase (ESBL) in 2 Providencia stuartii and 5 Providencia rettgeri. These ESBLs were coresistant to cefoxitin, chloramphenicol, ofloxacin, and sulfonamides but remained susceptible to imipenem. Three β-lactamases TEM-2, TEM-24, and DHA-1 were detected. blaTEM-24, blaDHA-1, aac(6′)-Ib-cr, and qnrA6 genes were successfully transferred to Escherichia coli strain HB101, and they were found located on the conjugatifs IncA/C plasmids. Genetic relatedness showed similar and different patterns among P. stuartii and P. rettgeri strains, respectively.

NDM-1 Metallo-β-Lactamase and ArmA 16S rRNA methylase producing Providencia rettgeri clinical isolates in Nepal

BackgroundDrug-resistant Providencia rettgeri producing metallo-β-lactamase and 16S rRNA methylase has been reported in several countries. We analyzed P. rettgeri clinical isolates with resistance to carbapenems and aminoglycosides in a hospital in Nepal.MethodsFive clinical isolates of multidrug-resistant P. rettgeri were obtained in a hospital in Nepal. Antimicrobial susceptibilities were determined using the microdilution method and entire genomes were sequenced to determine drug-resistant genes. Epidemiological analysis was performed by pulsed-field gel electrophoresis.ResultsFour of the 5 isolates were resistant to carbapenems (imipenem and meropenem), with MICs ≥16 mg/L, with the remaining isolate showing intermediate resistance to imipenem, with an MIC of 2 mg/L and susceptibility to meropenem with an MIC ≤1 mg/L. All 5 isolates had blaVEB-1. Of the 4 carbapenem-resistant strains, 3 had blaNDM-1 and 1 had blaOXA-72. All isolates were highly resistant to aminoglycosides (MICs ≥1,024 mg/L) and harbored armA. As the result of pulsed-field gel electrophoresis pattern analysis in the 5 P. rettgeri isolates, 4 had identical PFGE patterns and the fifth showed 95.7% similarity.ConclusionsThis is the first report describing multidrug-resistant P. rettgeri strains harboring blaNDM-1 or blaOXA-72 and armA isolated from patients in Nepal.

Importance of Providencia species as a major cause of travellers’ diarrhoea

In this study the importance of Providencia species as a cause of travellers' diarrhoea was examined using a selective medium developed by the authors. Providencia species could easily be distinguished from other enteric pathogens by the colour of the colonies obtained. Nine strains of Providencia alcalifaciens, nine of Providencia rettgeri and five of Providencia stuartii were isolated from 130 specimens, representing a surprisingly high incidence of infection compared with other pathogens isolated on SS agar and TCBS agar. Patients infected with P. rettgeri complained of abdominal pain, as for other Providencia species, but also of vomiting, which is rather characteristic of P. rettgeri infection. To analyse the pathogenicity of these isolates, their invasiveness was examined using Caco-2 cells. Most of the P. rettgeri strains invaded Caco-2 cells. Random amplified polymorphic DNA (RAPD) fingerprinting showed the same profile for two P. rettgeri isolates from individuals travelling in the same tour group. The results show that Providencia species, especially P. rettgeri, might cause diarrhoea, and that these species are important pathogens.

Natural antibiotic susceptibility of Providencia stuartii, P. rettgeri, P. alcalifaciens and P. rustigianii strains.

The natural antibiotic susceptibility of 38 Providencia rettgeri, 35 P. stuartii, 23 P. alcalifaciens and 20 P. rustigianii strains was examined. MIC values were determined by a microdilution procedure and evaluated by a table calculation programme. P. stuartii was the least susceptible Providencia sp. and was naturally resistant to tetracyclines, some penicillins, older cephalosporins, sulphamethoxazole and fosfomycin and to antibiotics to which other species of Enterobacteriaceae are also resistant. It was naturally sensitive to modern penicillins and cephalosporins, carbapenems and aztreonam, but its susceptibility to aminoglycosides and quinolones was difficult to assess. P. alcalifaciens and P. rustigianii strains were the most susceptible Providencia spp. They were naturally sensitive or intermediate to tetracyclines and sensitive to aminoglycosides and quinolones. Susceptibility to sparfloxacin, biapenem and sulphamethoxazole permitted the discrimination of P. alcalifaciens and P. rustigianii strains. The natural antibiotic susceptibility of P. rettgeri strains was between that of P. stuartii and that of the other providenciae. P. rettgeri was resistant to tetracyclines and fosfomycin, but more susceptible to aminoglycosides, quinolones, fosfomycin and numerous beta-lactam antibiotics than P. stuartii. A database is described of the natural antibiotic susceptibilities of Providencia spp. It can be used for the validation of antibiotic susceptibility test results of these micro-organisms.

Isolation and characterisation of dog uropathogenic Proteus mirabilis strains

Proteus mirabilis strains isolated from the urine of dogs with urinary tract infections, were characterised with respect to the production of haemolysin and fimbriae. In contrast to healthy dogs, P. mirabilis was also isolated in high numbers from the faeces of dogs suffering from recurrent urinary tract infections. Production of fimbriae was demonstrated by electron microscopy and the presence of genes for two different types of major fimbrial subunits (MR/P-like or UCA-like) was demonstrated by Southern hybridisation. These genes were absent in the Proteus vulgaris, Providentia rettgeri and Morganella morganii strains tested. All but one P. mirabilis strains were haemolytic and most strains produced fimbriae albeit in different amounts. The UCA fimbrial subunits from dog and human isolates have identical molecular weights and N-terminal sequences and are immunologically cross reactive. It was concluded that dog uropathogenic P. mirabilis strains are very similar to human uropathogenic P. mirabilis strains.

Numerical analysis of electrophoretic protein patterns of Providencia rettgeri strains from human faeces, urine and other specimens.

Thirty-one strains of Providencia rettgeri (mainly from humans) were characterized by one-dimensional SDS-PAGE of cellular proteins. The strains came from various countries and comprised 14 from urine, eight from faeces, two from bile (plus one from the liver of a sheep), two from sputum, one from an insect pupa and three the sources of which were unknown. Also included, for reference purposes, were the type strains of the four other Providencia species. The protein patterns, which contained 45-50 discrete bands, were highly reproducible and were used as the basis for two numerical analyses. In the first, which included all the protein bands, the 31 Prov. rettgeri strains formed 13 clusters at the 84% S level. In the second analysis, in which the principal protein bands (in the 33.3-41.3 kD range) were excluded, 29 of the 31 Prov. rettgeri strains formed a single cluster at the 81% S level, whilst the four Providencia reference strains remained unclustered. We conclude that high resolution PAGE combined with computerized analysis of protein patterns provides the basis for typing clinical strains of Prov. rettgeri. Reference strains of each of the 13 PAGE types identified are available from NCTC for inclusion in future studies.

Commercial identification systems often fail to identify Providencia stuartii.

We tested 145 clinical isolates in an attempt to evaluate some of the most widely used commercial identification systems in Europe in terms of their ability to identify Providencia strains. Two manual miniaturized systems (API 20E and Enterotube II) and three mechanized-automated systems (Cobas-Bact, Sceptor System, and Titertek-Enterobac-Rapid Automated System) were evaluated. Providencia alcalifaciens and Providencia rettgeri strains were correctly identified by all systems in all cases, and in most cases identification was achieved without the aid of supplementary tube tests. By contrast, Providencia stuartii was identified without the aid of supplementary tube tests for only 42.5% (API 20E), 37.5% (Enterotube), 68.7% (Sceptor), and 71.2% (Cobas-Bact) of the isolates. The overall misidentification rates were 16.3, 11.3, 11.3, and 10%, respectively. The Titertek-Enterobac-Rapid Automated System failed to identify only 1 of 80 strains (1.3%) and required supplementary tests in 2 other cases (2.5%). Since four of the multitest systems examined often failed to correctly identify P. stuartii, we conclude that supplementary conventional tube tests should always be used to distinguish this species from the other taxa of the Proteeae tribe.

Investigation of a Providencia rettgeri strain that has enterobacterial common antigen in the immunogenic state

Antigenic material obtained by phenol-water extraction from Providencia rettgeri strains, Escherichia coli O:14 strains, and mutants of the E. coli O:14 strain were examined by the passive (indirect) hemagglutination technique, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and by immune blotting (lipopolysaccharide (LPS) blotting). Providencia rettgeri 965, like E. coli O:14, was demonstrated to have an enterobacterial common antigen (ECA) in the immunogenic form but, unlike E. coli O:14, it possessed characteristics of a smooth strain. Two populations of molecules were observed to occur in P. rettgeri 965 phenol-water extracts: one consisting of LPS identifiable with specific O antisera and the other of ECA molecules identifiable with E. coli O:14 antiserum or with a monoclonal antibody against ECA.

Correlation of β-lactamase production and resistance to β-lactam antibiotics in enterobacteriaceae

Incidence of β-lactamase production (using the Nitrocefin test and isoelectric focusing) was evaluated on 284 strains of ampicillin-resistant Enterobacteriaceae. Production of the various β-lactamases was correlated with the resistance to different β-lactam antibiotics. No obvious correlation between the β-lactamase production and the resistance pattern was found. The most striking result was the lack of β-lactamase production in 42.6% of the strains. About 50% or more of the Proteus morganii, Proteus vulgaris, Serratia and Enterobacter strains produced no β-lactamases, in contrast to E. coli, Klebsiella, and Proteus rettgeri strains which produced β-lactamases extensively. The predominant enzyme was TEM 1, while TEM 2 enzyme was extremely common in Proteus mirabilis and Proteus rettgeri. Finally, it can be concluded from our results that the production of β-lactamases can be regarded as an important but not the sole determinant of resistance of β-lactam antibiotics.

HISTAMINE PRODUCTION BY FOOD‐BORNE BACTERIAL SPECIES12

A total of 112 bacterial strains representing 38 species were tested for their potential to elicit food poisoning outbreaks via histamine formation in foods. Proteus morganii and Enterobacter aerogenes displayed a quantitative superiority in terms of histamine production on a trypticase‐soy broth‐histidine (TSBH) medium and a tuna fish infusion broth (TFIB). When bacteria were incubated under standardized conditions in TSBH medium, histamine accumulated to levels exceeding 50 nmoles/ml of media with a total of 23 strains, including 13 of 15 P. morganii strains, 3 of 3 E. aerogenes strains, 3 of 12 Hafnia alvei strains, 1 of 4 Providencia alcalifaciens strains, 1 of 5 Enterobacter cloacae strains, 1 of 1 Proteus rettgeri strains, and 1 of 1 Citrobacter diversus strains. However, only 8 of the 15 P. morganii strains and the 3 E. aerogenes strains were capable of generating histamine in excess of 200 nmoles/ml in the TSBH medium. Of the 23 strains capable of appreciable histamine production in TSBH medium, P. morganii and E. aerogenes were, by far, the most prolific histamine producers in TFIB. Of the organisms tested, only P. morganii and E. aerogenes would appear to have the capability of forming sufficient histamine in scombroid fish products to elicit food poisoning outbreaks.

Benzyl penicillin and ampicillin in the cerebrospinal fluid during experimental Haemophilus influenzae meningitis.

The new aminoglycoside antibiotic, amikacin (formerly called BB-K8), was used to treat 12 episodes of urinary tract infection caused by hospital-acquired Proteus rettgeri strains. These bacteria were resistant in vitro to kanamycin and gentamicin, and infection persisted in most of the patients in spite of therapy with one of these agents. In all cases, the urinary tract infection was controlled or eradicated by therapy, although relapse or reinfection was frequently encountered in these patients with complicated urological problems. No toxicities attributable to the drug were encountered in the small group of patients.

HOST-RANGE OF PROTEUS MORGANII BACTERIOPHAGES.

COLICINE H, which kills many Escherichia, Shigella, Salmonella and a few Proteus hauseri1 also attacks many strains of P. morganii2. The relationship between P. morganii and the other genera mentioned has recently been strengthened by the finding3 that the guanidine + cytosine content of their deoxyribonucleic acids are very similar and differ from P. hauseri, P. rettgeri and Providence strains. On the other hand, it has been shown4,5 that although P. morganii strains are not susceptible to P. rettgeri phages, many P. morganii organisms are attacked by P. hauseri and Providence phages. There is also a well-known antigenic relationship between Proteus morganii and P. hauseri. Work on P. morganii phages has been confined to temperate varieties, and host-range determinations were limited to the Proteus group of organisms2,6. The phages were found to be species specific. In view of the uncertainty7 about the taxonomic position of Proteus morganii, it was decided to investigate the action of P. morganii phages derived from both lysogenic strains and sewage on members of the family Enterobacteriaceae.