The occurrence of the first two CTX-M-3 and TEM-1 producing isolates of Salmonella enterica serovar Oranienburg in Poland

Characterization of the Shiga toxin-producing Escherichia coli O26 isolated from human in Poland between 1996 and 2014

Shiga toxin-producing Escherichia coli (STEC) O26 infections can be comparable with STEC O157 infections in severity of the acute haemolytic-uremic syndrome HUS and long-term sequelae. Among O26 STEC isolates, highly virulent clone O26:H11/H- Sequence Type 29 (ST 29) emerged in Germany in mid-1990s and spread to European countries. However, up to date, no STEC O26:H11/H- belonging to ST29 has been documented in Poland. In this study, we determined the relationship and clonal structure, stx genotypes, plasmid gene profiles and antimicrobial resistance of nine human STEC O26:H11/H- strains from human patients in Poland between 1996 and 2014. Of the 9 human STEC O26:H11/H- strains, two belonged to ST29 and were isolated from two children with HUS and renal failure with sepsis respectively. These strains showed the molecular characteristics of the emerging human-pathogenic ST29 clone (stx1-, stx2a+, eae+, ehxA+, etpD+, katP-, espP-). The remaining STEC O26:H11/H- strains examined in this study, belonged to ST21, with plasmid genes profiles frequently reported in ST21 strains in Europe. STEC O26 infections with serious human health consequences highlight the need of continuous surveillance of non-O157 STEC and implementation of the diagnostic approaches focused on their detection. Significance and impact of the study: These study provides the first data on the occurrence of emerging Shiga toxin-producing Escherichia coli O26:H11 ST 29 clone in human patients in Poland. Those strains show the molecular characteristics of highly virulent new ST29 pathotype (stx1-, stx2a+, eae+ ehxA+, etpD+, katP-, espP-). These results demonstrated prompt efforts to implement diagnostic approaches detection of those pathogen in the European countries.

DIVERSITY OF ANTIMICROBIAL RESISTANCE MECHANISMS IN SALMONELLA

Abstract. Current review presents information on the antimicrobial resistance of Salmonella of various serotypes. The phenotypes of resistance and the main resistance mechanisms to the antimicrobials of various groups are described. Comparison data on the resistance to antimicrobials of Salmonella serological variants, which circulate worldwide including the Russian Federation (S. Typhimurium DT104, S. Newport, S. Virchow, S. Enteritidis) are shown. Moreover, epidemiological characteristics of transmission factors related to these pathogens are discussed. Special attention is given to genetic determinants, which encode the resistance of Enterobacteriaceae, as well as mobile genetic elements (integrons, plasmids, pathogenicity islands), which are involved in the spread of resistance.

Development of ceftriaxone resistance in Salmonella enterica serotype Oranienburg during therapy for bacteremia

BACKGROUND

The majority of nontyphoid Salmonella infection is identified in children. When an invasive or severe Salmonella infection is encountered, ceftriaxone is recommended for such patients. A 2-year-old girl was hospitalized for the treatment of Salmonella bacteremia and discharged with standard ceftriaxone treatment. She was readmitted to the hospital after 2 days due to the recurrence of the Salmonella bacteremia. The study aimed to unveil the mechanism for the relapse.

METHODS

Six isolates (4 blood and 2 stool) were recovered from the patient, with the last two blood isolates being ceftriaxone-resistant. Pulsed-field gel electrophoresis was used for genotyping. Ceftriaxone resistance genes and transferability of the resistance plasmid were examined by molecular methods.

RESULTS

All isolates were identified as Salmonella enterica serotype Oranienburg. Five isolates demonstrated almost identical electrophoresis patterns, except that in the two ceftriaxone-resistant isolates an extra band (>100 kb) was noted. A blaCMY-2 gene, carried by a 120-kb conjugative IncI1 plasmid of the sequence type 53, was identified in the two ceftriaxone-resistant isolates. Transfer of the resistance plasmid from one blood isolate to Escherichia coli J53 resulted in the increase of ceftriaxone minimum inhibitory concentration from 0.125 μg/mL to 32 μg/mL in the recipient.

CONCLUSION

Ceftriaxone is the standard therapeutic choice for invasive or serious Salmonella infections in children. Pediatricians should be aware of the possibility of resistance development during therapy, especially in areas with a widespread of ceftriaxone resistance genes that are carried by a self-transferrable plasmid, such as the blaCMY-2-carrying IncI1 plasmid identified herein.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Emergence of Klebsiella pneumoniae coproducing KPC-2 and 16S rRNA methylase ArmA in Poland

A Klebsiella pneumoniae epidemic strain that coproduced carbapenemase KPC-2 (K. pneumoniae carbapenemase 2) and 16S rRNA methylase ArmA has emerged in Poland. Four nonduplicate isolates from patients in a hospital in Warsaw, Poland, were found to carry the bla(KPC-2) and armA genes on ca. 50-kb and 90-kb plasmids, respectively. Tn4401 with a 100-bp deletion in the variable region was detected in all the isolates. XbaI pulsed-field gel electrophoresis (PFGE) revealed 93.2% similarity of the isolates. All the isolates were resistant to carbapenems and 4,6-disubstituted 2-deoxystreptamines.

Extended-spectrum β-lactamase-producing Salmonella enterica serovar Oranienburg (CTX-M-2 group) in a pediatric hospital in Tucumán, Argentina

INTRODUCTION: Salmonella sp infections have been reported over recent years in hospitals in Argentina and other countries due to multiresistant strains. The aim of this study was to characterize the extended-spectrum β-lactamases in third-generation cephalosporin-resistant strains of Salmonella enterica serovar Oranienburg. METHODS: We studied 60 strains isolated from children with gastroenteritis and/or extraintestinal complications. The antibiotic susceptibility patterns of the isolates were analyzed and the β-lactamases were characterized using phenotyping and genotyping methods. RESULTS: All the strains were resistant to ampicillin, cefotaxime, cefepime and aztreonam and partially susceptible to ceftazidime, thus corresponding well with the resistance phenotype conferred by CTX-M-type β-lactamases. An isoelectric point enzyme (pI = 7.9) was detected in all of the strains, and this was confirmed by PCR as a member of the CTX-M-2 group. CONCLUSIONS: This is the first report of Salmonella enterica serovar Oranienburg producing β-lactamases of the CTX-M-2 group in a pediatric hospital in Tucumán, Argentina.

Prevalence and characterization of extended-spectrum cephalosporin-resistant nontyphoidal Salmonella isolates in adults in Saint Petersburg, Russia (2002-2005)

We studied the prevalence of resistance to extended-spectrum cephalosporins (ESC) among 1,078 Salmonella enterica isolates collected from adults admitted to Botkin Hospital, St. Petersburg, Russia, for gastroenteritis between 2002 and 2005. Only two ESC-resistant isolates were detected, giving a low percentage of strains resistant to ESC (0.2%). One multidrug-resistant (MDR) isolate of the Virchow serotype produced a CTXM-3 extended-spectrum beta-lactamase (ESBL). The bla(CTX-M-3) gene was located downstream from an ISEcp1 element, on an 80-kb conjugative plasmid. The Virchow isolate possessed a class 1 integron with a 2.2-kb gene cassette (dhfrXII-orfF-aadA2). The second ESC-resistant isolate belonged to serotype Newport, was also MDR and produced a CMY-2 cephamycinase. This CMY-2-producing isolate (also called Newport MDR-AmpC) possessed a class 1 integron with a 1-kb gene cassette including a new variant of the aadA gene, aadA24. A large plasmid (>125 kb) was involved in transfer of the bla(CMY-2) gene. The ESC-resistant S. enterica isolates detected in this study were different from those (S. enterica serotype Typhimurium DT193 producing CTXM-4 or CTX-M-5 ESBLs) involved in several nosocomial outbreaks between 1994 and 2003 in Russia. This is the first description of both CTX-M-3 ESBL-producing S. enterica and Newport MDR-AmpC in Russia.

Salmonella resistant to extended-spectrum cephalosporins: prevalence and epidemiology

Salmonella resistant to extended-spectrum cephalosporins (ESCs) have emerged worldwide since 1988. By 2004, 43 countries had reported this public health problem. Resistance was mediated by classical extended-spectrum beta-lactamases, plasmid-mediated cephalosporinases, and recently a class A carbapenemase. Of these, CMY-2 is the most widely disseminated enzyme. Salmonella enterica serotype Typhimurium and S. enterica serotype Enteritidis are the most common serovars associated with ESC resistance in human infections. Many outbreaks in humans have been reported, most often among children and neonates. ESC-resistant Salmonella is frequently recovered from animals and food, with poultry as primary food source, suggesting that humans are often infected by these routes.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Nosocomial outbreak of pediatric gastroenteritis caused by CTX-M-14-type extended-spectrum beta-lactamase-producing strains of Salmonella enterica serovar London

CTX-M-14-type extended-spectrum beta-lactamase was first detected in Salmonella enterica serovar London strains which were isolated from three hospitalized pediatric patients with gastroenteritis. The isolates had pulsed-field gel electrophoresis patterns identical to those of the previously isolated antimicrobial-susceptible strains from community-acquired gastroenteritis, suggesting the susceptible clone acquired the resistance.

beta-Lactamases among extended-spectrum beta-lactamase (ESBL)-resistant Salmonella from poultry, poultry products and human patients in The Netherlands

OBJECTIVES

The purpose of this work was to study the genetic determinants responsible for extended-spectrum beta-lactamase (ESBL) resistance of Salmonella isolated from Dutch poultry, poultry meat and hospitalized humans.

METHODS

Thirty-four ESBL-resistant Salmonella isolates from The Netherlands were tested towards 21 antimicrobial agents. PCR and sequencing were used to determine the underlying genetic determinants responsible for the ESBL phenotypes. The transferability of the ESBL phenotypes was tested by conjugation to a susceptible Salmonella enterica serovar Dublin and plasmid purification, restriction fragment length polymorphism (RFLP) and pulsed-field gel electrophoresis (PFGE) were employed to further characterize a subset of the isolates.

RESULTS

A great genetic diversity was seen among the isolates. The bla(TEM-52) gene was most predominant and was found among Salmonella enterica serovars Blockley, Thomson, London, Enteritidis phage type 14b, Paratyphi B, Virchow and Typhimurium phage types 11 and 507. We also found the bla(TEM-20) gene in S. Paratyphi B var. Java and the bla(TEM-63) gene in S. Isangi. Furthermore, we detected the bla(CTX-M-28) gene in S. Isangi and the bla(CTX-M-3) gene in S. Typhimurium phage type 507. The bla(CTX-M-2) gene was identified in S. Virchow, which also contained a copy of the bla(SHV-2) gene and a copy of the bla(TEM-1) gene. The bla(SHV-12) gene was found alone in S. Concord and together with the bla(TEM-52) gene in S. Typhimurium. Finally, the bla(ACC-1) gene was cloned from a S. Bareilly isolate and was found to be present on indistinguishable plasmids in all S. Bareilly isolates examined as well as in a S. Braenderup isolate and a S. Infantis isolate.

CONCLUSIONS

Our data underscore the diversity of ESBL genes in Salmonella enterica isolated from animals, food products and human patients.

Detection of CTX-M-type beta-lactamase genes in fecal Escherichia coli isolates from healthy children in Bolivia and Peru

A survey was carried out from August to November 2002 to evaluate the antimicrobial susceptibilities of fecal Escherichia coli isolates from 3,208 healthy children from four different urban areas of Latin America, two in Bolivia (Camiri and Villa Montes) and two in Peru (Yurimaguas and Moyobamba). Ceftriaxone-resistant E. coli isolates were detected in four children, one from each of the areas sampled. The isolates exhibited a multidrug-resistant phenotype, including resistance to oxyimino-cephalosporins and aztreonam, and the MICs of ceftazidime for the isolates were lower than those of cefotaxime. By PCR and sequencing, the bla(CTX-M-2) determinant was detected in three isolates and the bla(CTX-M-15) determinant was detected in one isolate (from Peru). The CTX-M-2-producing isolates belonged to three different phylogenetic groups (groups A, B2, and D), while the CTX-M-15-producing isolate belonged to phylogenetic group D. The bla(CTX-M-2) determinants were transferable to E. coli by conjugation, while conjugative transfer of the bla(CTX-M-15) determinant was not detectable. Plasmids harboring the bla(CTX-M-2) determinant exhibited similar restriction profiles, and in all of them the gene was located on a 2.2-kb PstI fragment, suggesting a genetic environment similar to that present in In35 and InS21. The findings of the present study confirm the widespread distribution of CTX-M-type beta-lactamases and underscore the role that commensal E. coli isolates could play as a potential reservoir of these clinically relevant resistance determinants. This is the first report of CTX-M-type enzymes in Bolivia and Peru and also the first report of the detection of CTX-M-15 in Latin America.

Detection of cefotaxime-resistant CTX-M-3 in clinical isolates of Serratia marcescens

Strains of Serratia marcescens (isolated in a hospital during April and August 2000) resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, streptomycin, tetracycline, and gentamicin were characterized. Out of a total of 34 clinical isolates 6 (17.6 %) exhibited the extended spectrum beta-lactamases (ESBL) resistance; they were also resistant to cefotaxime (minimum inhibitory concentration, MIC > or = 128 microg/mL) but susceptible to imipenem (MIC < or = 0.5 microg/mL). This multidrug resistance was shown to be transferred by a conjugative plasmid. Transconjugants revealed similar MIC profiles when compared to the parental strains. Isoelectric focusing revealed one major transferable beta-lactamase (pI 8.4) which was further identified as CTX-M-3 by PCR and gene sequencing. The presence of strains with this type of ESBL showed the evolution of bla genes and their dissemination among at least three species of the family Enterobacteriaceae isolated within a single hospital. The predominance of CTX-M type enzymes found in this area of Taiwan appeared to be similar to that described in Poland.

Multiple outbreaks of nosocomial salmonellosis in Russia and Belarus caused by a single clone of Salmonella enterica serovar Typhimurium producing an extended-spectrum beta-lactamase

Thirty-four cefotaxime-resistant Salmonella enterica serovar Typhimurium isolates representative of the isolates that caused outbreaks of gastroenteritis in 10 hospitals in seven regions of Russia and Belarus from 1994 to 2003 were analyzed. All isolates produced the CTX-M-5-like extended-spectrum beta-lactamase, which confers high-level resistance to cefotaxime and ceftriaxone and decreased susceptibility to ceftazidime. The bla(CTX-M) genes were located on small (7.4- to 12-kb) non-self-transferable plasmids approximately 20 bp downstream of the ISEcp1 insertion sequences. Some isolates carried additional conjugative plasmids mediating resistance to penicillin-inhibitor combinations and various non-beta-lactam agents, including tetracycline, chloramphenicol, gentamicin, tobramycin, and co-trimoxazole. Despite the minor differences in susceptibility patterns, all isolates were considered clonally related on the basis of arbitrarily primed PCR and pulsed-field gel electrophoresis analysis. The similarities of the restriction profiles of the CTX-M-coding plasmids further supported the clonal origin of these isolates.

Expanded-spectrum cephalosporin resistance in non-typhoid Salmonella

Expanded-spectrum cephalosporins (ESCs) such as ceftriaxone, together with fluorinated quinolones, are the choice antibiotics in the treatment of invasive salmonella infections. Resistance to ESCs among non-typhoid salmonella has been recognised since the late 1980s. Currently, ESC-resistant salmonella strains are reported world-wide and in some areas their incidence is significant. Resistance is mainly due to acquisition of multi-resistant plasmids encoding a variety of extended-spectrum and AmpC-type beta-lactamases. The origins of ESC-resistant salmonellae are diverse. Exchange of resistance determinants between salmonellae and nosocomial enterobacteria seems to be frequent, at least in developing countries. Also, the use of newer beta-lactams in animal husbandry and veterinary medicine may have facilitated the spread of ESC-resistant salmonella strains in livestock.

Cefotaximases (CTX-M-ases), an expanding family of extended-spectrum β-lactamases

Among the extended-spectrum β-lactamases, the cefotaximases (CTX-M-ases) constitute a rapidly growing cluster of enzymes that have disseminated geographically. The CTX-M-ases, which hydrolyze cefotaxime efficiently, are mostly encoded by transferable plasmids, and the enzymes have been found predominantly in Enterobacteriaceae, most prevalently in Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, and Proteus mirabilis. Isolates of Vibrio cholerae, Acinetobacter baumannii, and Aeromonas hydrophila encoding CTX-M-ases have also been reported. The CTX-M-ases belong to the molecular class A β-lactamases, and the enzymes are functionally characterized as extended-spectrum β-lactamases. This group of β-lactamases confers resistance to penicillins, extended-spectrum cephalosporins, and monobactams, and the enzymes are inhibited by clavulanate, sulbactam, and tazobactam. Typically, the CTX-M-ases hydrolyze cefotaxime more efficiently than ceftazidime, which is reflected in substantially higher MICs to cefotaxime than to ceftazidime. Phylogenetically, the CTX-M-ases are divided into four subfamilies that seem to have descended from chromosomal β-lactamases of Kluyvera spp. Insertion sequences, especially ISEcp1, have been found adjacent to genes encoding enzymes of all four subfamilies. The class I integron-associated orf513 also seems to be involved in the mobilization of blaCTX-M genes. This review discusses the phylogeny and the hydrolytic properties of the CTX-M-ases, as well as their geographic occurrence and mode of spread.Key words: extended-spectrum β-lactamases, cefotaximases, phylogeny, dissemination, hydrolytic properties.

Antimicrobial drug resistance in Salmonella enterica

PURPOSE OF REVIEW

This review addresses the changing patterns of antimicrobial resistance in Salmonella.

RECENT FINDINGS

Resistance to chloramphenicol, amicillin and cotrimoxazole is common in Salmonella Typhi and Paratyphi A in Asia and a few countries of Africa. In some countries, the isolation of multidrug resistant strains appears to be declining. R-type ACSSuT Salmonella Typhimurium DT104 is common in animal and human infections in many industrialized countries. Strains with additional trimethoprim and low-level ciprofloxacin resistance are increasingly seen. Resistance is appearing in new Typhimurium phage types, such as DT204b, and is common in serotypes Hadar and Virchow but not Enteritidis. A variety of Ambler class A and class C beta-lactamase enzymes have now been described causing extended spectrum cephalosporin resistance in different Salmonella serotypes. The overall level of extended spectrum cephalosporin resistance currently appears low. Low-level ciprofloxacin resistance, associated with point mutations in the gyrA gene, is inceasingly common in typhoidal and non-typhoidal serotypes isolated from humans and animals and has been associated with treatment failures. Sporadic reports describe human infections with non-Typhi Salmonella that are fully fluoroquinolone resistant. There is increasing support for the call to revise the fluoroquinolone breakpoints for Salmonella. A study from Denmark suggested that infections with drug resistant Salmonellae are associated with a poorer outcome than drug susceptible infections.

SUMMARY

Resistance is increasing to several critical antimicrobials used to treat invasive salmonellosis including extended spectrum cephalosporins and quinolones. In resource poor countries, such drug resistant Salmonella infections may become effectively untreatable.