Secular trends in incidence and antimicrobial resistance among clinical isolates of Salmonella at a university hospital in Taiwan, 1983-1999

Changes in epidemiology and antimicrobial susceptibility of nontyphoid Salmonella in children in southern Taiwan, 1997-2016

BACKGROUND

This study aimed to investigate the changing trends in serogroup distribution and antimicrobial susceptibility of nontyphoid Salmonella (NTS) isolated from children in the past two decades in Taiwan.

METHODS

This retrospective study enrolled patients aged younger than 18 years with culture-proven NTS infection in a tertiary medical center from 1997 to 2016. Data on age, Salmonella serogroup, culture sample, and antimicrobial susceptibility were obtained from medical records. The rates of Salmonella serogroups and antimicrobial resistance were compared between period 1 (1997-2006) and period 2 (2007-2016).

RESULTS

A total of 2075 NTS isolates were identified from 1997 to 2016 (1036 in period 1, 1039 in period 2). The major isolates were from feces (89.1%) and blood (10.4%). The most common serogroup was serogroup B (54.8%), followed by serogroup D (18.8%). There was a significant decline in the proportion of serogroup B with a concomitant rise in serogroup D in the past two decades. In period 2, resistance to cefotaxime and cefixime increased remarkably among serogroup B, whereas resistance to ampicillin increased notably among serogroup D. Furthermore, the incidence of multidrug-resistant (≥3 antibiotics) NTS significantly decreased in both serogroup B and serogroup D in period 2.

CONCLUSION

This study revealed a significant rise in serogroup D with a concomitant decline in serogroup B NTS infection in Taiwanese children. Moreover, antimicrobial resistance to third-generation cephalosporins increased in serogroup B. Continuous surveillance of NTS serogroup distribution and antimicrobial susceptibility is mandatory to formulate therapeutic strategies for NTS infections.

The clinical outcomes of antimicrobial therapy in pediatric patients with nontyphoid salmonellosis with different levels of severity

BACKGROUND

To evaluate if a severity score could differentiate the severity of children with nontyphoid salmonellosis; clinical outcomes of antimicrobial therapy in nontyphoid salmonellosis children with different severities.

METHODS

Admitted children with nontyphoid salmonellosis from 1996 to 2009 were monitored. Enrolled patients were divided into no antibiotics, concordant, and discordant therapies. Besides, the patients were classified into mild, moderate, and severe group according to the severity score. Clinical outcomes were compared among them.

RESULTS

A total of 558 patients were enrolled. In no therapy subset, compared with mild group, patients had worse clinical outcomes and more complications in severe group. Patients receiving no therapy had better clinical outcomes in mild group. However, patients receiving concordant therapy (ceftriaxone) had better clinical outcomes in severe group.

CONCLUSIONS

The severity score and local antibiotic susceptibility could serve as guides for antibiotic prescription for severe nontyphoid salmonellosis in children. Inappropriate antibiotic use would worsen clinical outcomes in children with mild nontyphoid salmonellosis.

Coptidis rhizome and Si Jun Zi Tang can prevent Salmonella enterica serovar Typhimurium infection in mice

Salmonella, a common zoonotic pathogen, causes gastroenteritis in both humans and animals. Traditional Chinese Medicine (TCM) has been used to improve gastrointestinal dysfunction and to modify the immune response to inflammation for centuries. This study used six herbal plants and four TCM formulae to rate their efficacy in preventing S. Typhimurium infection via mouse model. Minimum bactericidal concentration (MBC) of Coptidis rhizome (CR) against the reference strain tallied 12.5 mg/ml and against clinical isolate ST21 was 25 mg/ml. MBCs of other herbal extracts and formulae on Salmonella Typhimurium strains were above 50 mg/ml. In the mice model, CR and Si Jun Zi Tang (SJZT) could significantly decrease the bacterial load in organs and blood after being challenged, along with body weight loss due to the infection. CR and SJZT alleviated infection-induced interferon-gamma levels in the serum and tissues, and tumor necrosis factor-alpha (TNF-α) levels in intestinal tissues. CR and SJZT serum metabolites could suppress S. Typhimurium invasion and TNF-α expression in RAW264.7 cells. The therapeutic activity of CR and SJZT may involve berberine, ginsenoside Rb1, and glycyrrhizin, interfering with Salmonella when invading macrophages. CR and SJZT has shown potential in preventing S. Typhimurium infection through the regulation of the immune response.

Clinical manifestations of nontyphoid salmonellosis in children younger than 2 years old--experiences of a tertiary hospital in southern Taiwan

BACKGROUND

Few published studies have explored the clinical manifestations of nontyphoid salmonellosis in children <2 years of age. The aim of this study was to investigate the clinical manifestations, microbiological features, complications, fecal excretion time, and responses to treatment in children <2 years of age with nontyphoid salmonellosis.

METHODS

Between January 2005 and December 2009, pediatric patients who were admitted to Kaohsiung Veterans General Hospital with positive cultures for nontyphoid Salmonella were enrolled. The following data were recorded: demographic, clinical, and microbiological features, underlying diseases, treatment regimen, complications, responses to treatment, and fecal excretion time. The clinical manifestations were compared between patients <2 years of age and patients >2 years of age.

RESULTS

Of a total 279 enrolled patients, 179 were >2 years of age. Compared with the patients who were ≥2 years of age, patients <2 years of age demonstrated a significantly higher incidence of bloody stool, mixed infection, extraintestinal infection, longer course of antibiotics, longer course of diarrhea after admission, and more days spent in the hospital. The rates of insusceptibility of nontyphoid Salmonella to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole, ceftriaxone, and ciprofloxacin in patients <2 years of age were 37.87%, 29.09%, 23.73%, 3.26%, and 2.25%, respectively. Younger patients were generally more susceptible to antibiotics than patients ≥2 years of age, although this result was not statistically significant.

CONCLUSION

The clinical manifestations of nontyphoid salmonellosis are more severe in younger children <2 years of age than older children. Local susceptibility patterns could serve as a guide for the prescription of antibiotics by clinicians.

Reappraisal of parenteral antimicrobial therapy for nontyphoidal Salmonella enteric infection in children

Increasing antimicrobial resistance in nontyphoidal Salmonella (NTS) species complicates the use of antibiotics if indicated. We investigated the impact of antimicrobial resistance on clinical outcomes and discussed how to use antibiotics rationally. Hospitalized children in 2005-2006 with stool cultures positive for NTS were identified. The clinical and microbiological features were retrospectively reviewed. A total of 683 children were included [371 (54.3%) male; 89.5% <5 years of age]. Antibiotics were given to 56.5% of the patients; third-generation cephalosporin was the most commonly used drug class. Cases receiving antibiotics that were inactive in vitro did not have more complications than those receiving antibiotics active in vitro. Complications occurred in 7.9% of the patients, with bacteraemia being the most common (57.4%). Compared to the others, patients with longer febrile duration and higher C-reactive protein (CRP) levels (CRP ≥100 mg/L) were more frequently put on empirical antimicrobial therapy and had more complications. These patients usually had shorter hospitalization and duration of fever if antimicrobial agents that can reach high tissue concentrations in the intestinal mucosa were administered, such as fluoroquinolone or ceftriaxone. It is concluded that adequate antibiotics may be clinically beneficial to a subset of patients with high CRP and longer duration of fever among children with NTS enteritis. To prevent the induction of antibiotic resistance from this therapy, we suggested a short course (3-5 days) of intravenous ceftriaxone for such patients, which would lead to a faster clinical recovery.

In vitro and in vivo intracellular killing effects of tigecycline against clinical nontyphoid Salmonella isolates using ceftriaxone as a comparator

Salmonella is an important, worldwide food-borne pathogen. Resistance to fluoroquinolones and cephalosporins has been increasingly reported, and new therapeutic agents are desperately needed. In this study, we evaluated the in vitro antimicrobial susceptibility of clinical nontyphoidal Salmonella isolates to tigecycline. Antibacterial activity of tigecycline, ceftriaxone, and ciprofloxacin were investigated by time-kill studies and the murine peritonitis model. The MIC₅₀/MIC₉₀ values of tigecycline, ceftriaxone, and ciprofloxacin against 76 Salmonella isolates were 0.25/0.5, 1/8, and 0.125/0.5 μg/ml, respectively. The intracellular inhibitory activity of tigecycline at 0.5 μg/ml (1 × MIC) against Salmonella isolates in human peripheral blood mononuclear cells was sustained for 24 h. In a mouse peritonitis model, tigecycline reduced the extracellular and intracellular bacterial counts from 10⁷ CFU/ml and 10⁵ CFU/ml, respectively, to an undetectable level within 96 h. The results were similar to those obtained with ceftriaxone. The survival rate of mice exposed to tigecycline after being infected by an inoculum of 1 × 10⁵ CFU was 80%, and that of mice exposed to ceftriaxone was 100%. When the inoculum was increased to 1.3 × 10⁶ CFU, the survival rate of mice treated by tigecycline was 20%, and that of mice exposed to ceftriaxone was 0% (P = 0.2). When a ceftriaxone- and ciprofloxacin-resistant but tigecycline-susceptible isolate was tested, mice treated by tigecycline had a higher survival rate than those treated by ceftriaxone (15/20 [75%] versus 6/20 [30%]; P = 0.011). Our results suggest that tigecycline is at least as effective as ceftriaxone for murine Salmonella infections and warrants further clinical investigations to delineate its potential against human Salmonella infections.

Extraintestinal focal infections in adults with nontyphoid Salmonella bacteraemia: predisposing factors and clinical outcome

BACKGROUND

Nontyphoid Salmonella (NTS) isolates lead to not only self-limited, acute gastrointestinal infections, but also bacteraemia with or without extraintestinal focal infections (EFIs). The risk factors associated with EFIs in adults with NTS bacteraemia were not clearly elucidated.

METHODS

In a medical center in southern Taiwan, patients aged > or = 18 years with NTS bacteraemia between January 1999 and June 2005 were included for analysis.

RESULTS

Of 129 patients, 51 (39.5%) were complicated with EFIs. The most common EFI was mycotic aneurysm, followed by pleuropulmonary infections and spinal osteomyelitis. Compared to patients with primary bacteraemia, those with EFIs had higher leucocyte counts (P = 0.004) and higher serum levels of C-reactive protein (P < 0.0001). The development of EFIs was associated with a higher mortality, more severe septic manifestations, longer hospital stays and duration of antimicrobial therapy. Univariate analysis revealed that diabetes mellitus (P = 0.02), hypertension (P = 0.02) and chronic lung disease (P = 0.006) were significantly associated with EFIs. However, patients with malignancy (P = 0.01) and immunosuppressive therapy (P = 0.03) were less likely to develop EFIs. On the basis of multivariate analysis, an independent factor for the occurrence of EFIs was age [adjusted odds ratio (aOR) 1.05; 95% confidence interval (CI) 1.02-1.07; P < 0.0001], whilst malignancy was negatively associated with EFIs (aOR 0.16; 95% CI 0.14-0.78; P = 0.01).

CONCLUSION

Amongst patients with NTS bacteraemia, EFIs often occurred in the aged, and were associated with a higher mortality and morbidity. Recognition of specific host factors is essential for identification of EFIs which often demand early surgical interventions and prolonged antimicrobial therapy.

Cefotaxime-ciprofloxacin combination therapy for nontyphoid Salmonella bacteremia and paravertebral abscess after failure of monotherapy

Therapeutic failure of monotherapy with either a third-generation cephalosporin or a fluoroquinolone against nontyphoid salmonellae has been observed in clinical practice. Combination therapy with both agents is recommended in the literature for treating life-threatening infections. However, we know of no published case reports that indicate a therapeutic advantage of this combination therapy for nontyphoid salmonellae infections. We describe a 60-year-old man who had breakthrough bacteremia with vertebral osteomyelitis and paravertebral abscess caused by Salmonella enterica serotype Choleraesuis. This was not controlled with sequential monotherapy but was eventually cured with cefotaxime-ciprofloxacin combination therapy. The Etest showed that the strain was susceptible to cefotaxime and ciprofloxacin, but resistant to nalidixic acid. Cefotaxime and ciprofloxacin in combination may be considered as an option for difficult-to-treat salmonellosis.

Pulsed-field gel electrophoresis, plasmid profiles and phage types for the human isolates of Salmonella enterica serovar Enteritidis obtained over 13 years in Taiwan

AIMS

Plasmid profile, phage typing, and pulsed-field gel electrophoresis (PFGE) patterns of 124 Salmonella Enteritidis strains isolated in 1998-2002 in Taiwan were analysed and the results were compared with those of the 63 strains obtained in 1991-1997, so that molecular subtypes and epidemic strains for Salmonella Enteritidis over a 13-year period (1991-2002) could be elucidated.

METHODS AND RESULTS

A total of 124 strains of Salmonella Enteritidis isolated from human in Taiwan between 1998 and 2002 were analysed by PFGE, plasmid analysis and phage typing. The results obtained were compared with those of the 63 strains obtained in 1991-1997, so that the clonal relationships for a total of 187 strains obtained over 13 years could be elucidated. For PFGE, restriction enzymes XbaI, SpeI and NotI were used for chromosomal DNA digestion. Results showed 28 PFGE pattern combinations for the 187 Salmonella strains. Of them, pattern X3S3N3 was the major subtype as 130 strains isolated from different locations during 1991-2002 showed this PFGE pattern. For all these 187 strains, the genetic similarity was higher than 80%. Plasmid analysis showed 17 distinct types, which consist of one to four plasmids and the predominant phage type of those strains was PT4 (71.6%) and PT6a (13.4%). The three methods identified different degrees of polymorphism in the following order: plasmid profile (18 types, D = 0.659) > PFGE (28 types, D = 0.512) > phage typing (13 types, D = 0.438). As PFGE patterns, phage type and plasmid profile were combined for subtyping, the 187 strains could be grouped into 46 subtypes and the discriminatory index was raised to 0.795. For these 46 subtypes, the predominant one was X3S3N3/P1/PT4, which contained 77 (41%) isolates.

CONCLUSIONS

Most of the Salmonella Enteritidis strains from sporadic cases were with pattern X3S3N3. They were the prevalent and may be the epidemic strains found in Taiwan during 1991-2002. The present study suggested that the several variants were derived from a single clonal line and the genome for strains of Salmonella Enteritidis are highly conserved over a 13-year period (1991-2002).

SIGNIFICANCE AND IMPACT OF THE STUDY

The results obtained here are useful for epidemiolgical study of salmonellosis caused by Salmonella Enteritidis in Taiwan. Comparing the data of the present study with those obtained for strains from other countries, the major subtypes for Salmonella Enteritidis infection in the world can be elucidated.

Ceftriaxone resistance of nontyphoidal Salmonella enterica isolates in Northern Taiwan attributable to production of CTX-M-14 and CMY-2 beta-lactamases

Among 3,027 nontyphoidal Salmonella enterica isolates identified between January 1999 and December 2002 in a medical center in northern Taiwan, 31 were resistant to the extended-spectrum cephalosporin ceftriaxone (1.02% [31/3,027]), including 2 in 1999 (0.36% [2/549]), 13 in 2000 (1.49% [13/870]), 7 in 2001 (0.78% [7/893]), and 9 in 2002 (1.26% [9/715]). Sixteen of these isolates belonged to Salmonella serogroup B, nine belonged to serogroup C, four belonged to serogroup D, and two belonged to serogroup E. The majority were from stool cultures. The mechanism of resistance was investigated for eight isolates, including three S. enterica serovar Typhimurium, one S. enterica serovar Wagenia, one S. enterica serovar Senftenberg, one S. enterica serovar Derby, one S. enterica serovar Panama, and one S. enterica serovar Duesseldorf isolate. All eight patients from whom these isolates were recovered had community-acquired infections. All eight isolates were resistant to ampicillin, ceftriaxone, and cefotaxime but susceptible to imipenem and ciprofloxacin. Ceftriaxone resistance was due to the production of the CMY-2 AmpC beta-lactamase by seven isolates and the CTX-M-14 beta-lactamase by the remaining isolate. Both beta-lactamase genes were carried on conjugative plasmids. In a 2.5-kb region encompassing the bla(CMY-2) gene, at nucleotide 49 upstream of the start codon of bla(CMY-2), three of the seven bla(CMY-2)-positive isolates had an A nucleotide and four had a G nucleotide. In conclusion, the ceftriaxone resistance of nontyphoidal Salmonella isolates in our hospital was attributed to the CTX-M-14 and CMY-2 beta-lactamases.

Increasing ceftriaxone resistance in Salmonella isolates from a university hospital in Taiwan

OBJECTIVES

Salmonella infection is a distressing health problem worldwide. This study reports the changing epidemiology of Salmonella infections in Taiwan during 1999-2003, with emphasis on increasing ceftriaxone resistance.

METHODS

Records of Salmonella clinical isolates in Chang Gung Memorial Hospital during 1999-2003 were reviewed. All isolates were identified and antimicrobial susceptibility determined by standard methods. A total of 22 ceftriaxone-resistant isolates were investigated by PCR sequencing of the bla(TEM), bla(SHV), bla(CTX-M) and ampC genes. Southern-blot hybridization was used to localize the ampC gene. Infrequent-restriction-site PCR was used to genotype these isolates.

RESULTS

A total of 3635 Salmonella isolates, including 3592 (98.8%) non-typhoid Salmonella, were identified. Serogroup B (55.6%) remained the most predominant, but the prevalence has been decreasing. In contrast, serogroup D infections have increased significantly from 13.6 to 22.8%. Overall resistance to ampicillin and chloramphenicol remained high, with the highest rate (91% to both drugs) observed in Salmonella enterica serotype Choleraesuis in 2003. A sudden upsurge of ciprofloxacin resistance from zero to 69% was found in S. Choleraesuis. Ceftriaxone resistance increased in several serogroups (0.8-2.1%; average, 1.5%). The resistance was associated with plasmid-mediated bla(CMY-2) in 14 cases and extended-spectrum beta-lactamases (ESBLs), including CTX-M-3 (n=6), SHV-2a (n=1) and SHV-12 (n=1), in others. Diverse serotypes and genotypes were found among the ceftriaxone-resistant isolates.

CONCLUSIONS

Increasing ceftriaxone resistance in non-typhoid Salmonella appears to link to the spread of plasmid-mediated ampC or ESBL genes. Effective measures should be taken to prevent the problem worsening.

Veterinary Drug Usage and Antimicrobial Resistance in Bacteria of Animal Origin

In the production of food animals, large amounts of antimicrobial agents are used for therapy and prophylaxis of bacterial infections and in feed to promote growth. There are large variations in the amounts of antimicrobial agents used to produce the same amount of meat among the different European countries, which leaves room for considerable reductions in some countries. The emergence of resistant bacteria and resistance genes due to the use of antimicrobial agents are well documented. In Denmark it has been possible to reduce the usage of antimicrobial agents for food animals significantly and in general decreases in resistance have followed. Guidelines for prudent use of antimicrobial agents may help to slow down the selection for resistance and should be based on knowledge regarding the normal susceptibility patterns of the causative agents and take into account the potential problems for human health. Current knowledge regarding the occurrence of antimicrobial resistance in food animals, the quantitative impact of the use of different antimicrobial agents on selection of resistance and the most appropriate treatment regimes to limit the development of resistance is incomplete. Programmes monitoring the occurrence and development of resistance and consumption of antimicrobial agents are strongly desirable, as is research into the most appropriate ways to use antimicrobial agents in veterinary medicine.

Fluoroquinolone resistance in Salmonella enterica serotype Choleraesuis, Taiwan, 2000-2003

Salmonella enterica serotype Choleraesuis is a highly invasive pathogen that infects humans and causes systemic infections that require antimicrobial therapy. Surveillance in Taiwan showed that fluoroquinolone resistance in S. Choleraesuis markedly increased from 2000 to 2003, reaching approximately 70% in 2003.

Antimicrobial resistance in nontyphoid Salmonella serotypes: a global challenge

Increasing antimicrobial resistance in nontyphoid Salmonella species has been a serious problem for public health worldwide. The high rate of resistance is hampering the use of conventional antibiotics, and growing resistance to newer antimicrobial agents is aggravating the situation. The circumstances of occurrence and spread of antimicrobial resistance are complex; however, a major cause is the widespread use of antimicrobial agents in food animals, particularly in animal feed. Genetic analysis has indicated that the source of resistance is frequently a transferable plasmid. Recent studies have revealed that some serotype-specific virulence plasmids form hybrid plasmids through recombination with resistance plasmids or acquire gene cassettes consisting of multiple resistance genes. Such evolutionary events provide a virulent strain the advantage of survival in an unfavorable drug environment. In view of the serious implications associated with drug-resistant Salmonella species, a more deliberate use of antibiotics in both human medicine and animal industry is warranted. Continued surveillance of antimicrobial resistance and use of antimicrobial agents in food animals is also indispensable.

Salmonella enterica serotype Choleraesuis: epidemiology, pathogenesis, clinical disease, and treatment

Nontyphoid Salmonella strains are important causes of reportable food-borne infection. Among more than 2,000 serotypes, Salmonella enterica serotype Choleraesuis shows the highest predilection to cause systemic infections in humans. The most feared complication of serotype Cholearesuis bacteremia in adults is the development of mycotic aneurysm, which previously was almost uniformally fatal. The advances in diagnostic techniques, surgical care, and antimicrobial therapy have greatly improved the survival of these patients. However, the recent emergence of serotype Choleraesuis that is resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and, notably, fluoroquinolone antibiotics has aroused concern about the use of these agents for the empirical treatment of systemic infection caused by this organism. In view of the serious implications of the situation, the chain of transmission and mechanism of resistance should be carefully studied to reduce the spread of infection and threat to human health. To date, there are no vaccines available to prevent serotype Choleraesuis infections in humans. The availability, in the near future, of the genome sequence of serotype Cholearesuis will facilitate the development of effective vaccines as well as the discovery of new targets for novel antimicrobial agents.

Ciprofloxacin-resistant Salmonella enterica Typhimurium and Choleraesuis from pigs to humans, Taiwan

We evaluated the disk susceptibility data of 671 nontyphoid Salmonella isolates collected from different parts of Taiwan from March 2001 to August 2001 and 1,261 nontyphoid Salmonella isolates from the National Taiwan University Hospital from 1996 to 2001. Overall, ciprofloxacn resistance was found in 2.7% (18/671) of all nontyphoid Salmonella isolates, in 1.4% (5/347) of Salmonella enterica serotype Typhimurium and in 7.5% (8/107) in S. enterica serotype Choleraesuis nationwide. MICs of six newer fluoroquinolones were determined for the following isolates: 37 isolates of ciprofloxacin-resistant (human) S. enterica Typhimurium (N = 26) and Choleraesuis (N = 11), 10 isolates of ciprofloxacin-susceptible (MIC <1 μg/mL) (human) isolates of these two serotypes, and 15 swine isolates from S. enterica Choleraesuis (N = 13) and Typhmurium (N = 2) with reduced susceptibility to ciprofloxacin (MIC >0.12 μg/mL). Sequence analysis of the gryA, gyrB, parC, parE, and acrR genes, ciprofloxacin accumulation; and genotypes generated by pulsed-field gel electrophoresis with three restriction enzymes (SpeI, XbaI, and BlnI) were performed. All 26 S. enterica Typhimurium isolates from humans and pigs belonged to genotype I. For S. enterica Choleraesuis isolates, 91% (10/11) of human isolates and 54% (7/13) of swine isolates belonged to genotype B. These two genotypes isolates from humans all exhibited a high-level of resistance to ciprofloxacin (MIC 16–64 μg/mL). They had two-base substitutions in the gyrA gene at codons 83 (Ser83Phe) and 87 (Asp87Gly or Asp87Asn) and in the parC gene at codon 80 (Ser80Arg, Ser80Ile, or Ser84Lys). Our investigation documented that not only did these two S. enterica isolates have a high prevalence of ciprofloxacin resistance nationwide but also that some closely related ciprofloxacin-resistant strains are disseminated from pigs to humans.

Nontyphoid salmonellosis in taiwan children: clinical manifestations, outcome and antibiotic resistance

OBJECTIVES

The purposes of this study were to investigate the epidemiologic, clinical, and microbiologic features of patients with nontyphoid salmonellosis and to elucidate the impact of resistance on the outcome of nontyphoid salmonellosis in Taiwan. The authors also sought to develop a severity score to derive an objective guideline for antibiotic use in nontyphoid salmonellosis in the era of increasing antibiotic resistance.

METHODS

The authors prospectively monitored 311 children with nontyphoid salmonellosis in Kaohsiung, Taiwan. The demographic, clinical, and microbiologic features, underlying diseases, treatment regimen, complications, and outcome were analyzed. In vitro susceptibility testing of the isolates was performed.

RESULTS

The median age of affected patients was 15 months. Salmonella enteritidis B caused 68.5% of episodes, followed by S. enteritidis C1 (11.9%), D (7.7%), C2 (7.1%), E (2.6%), S. choleraesuis (1.6%), and S. paratyphi (0.6%). Sixty percent of isolates were resistant to ampicillin. Patients with bacteremia could not be differentiated from patients without bacteremia on clinical grounds. Patients receiving antibiotics that were inactive in vitro (discordant therapy) had more days of fever and longer hospital stay compared with patients receiving antibiotics that were active in vitro (concordant therapy). Patients receiving no antibiotic treatment had the fewest days of fever and shortest hospital stays, especially among patients with mild illness (severity score, 0-1).

CONCLUSION

Blood culture should be obtained in patients with nontyphoid salmonellosis to detect bacteremia. In treating antibiotic-resistant nontyphoid salmonellosis, antibiotics are still not mandatory for patients who present with primarily gastrointestinal symptoms and limited signs of systemic inflammation reflected by a low severity score (low C-reactive protein, fewer band cells in peripheral blood, and fewer days of fever before admission). Susceptibility data should be promptly obtained because use of discordant antibiotics appears to prolong illness.

Salmonella bacteraemia in Turkish children: 37 cases seen in a university hospital between 1993 and 2002

The aim of the study was to evaluate the clinical pattern of Salmonella bacteraemia in Turkish children. From 1993 to 2002, all children with a blood culture positive for Salmonella were retrospectively evaluated in the Division of Paediatric Infectious Diseases in Ankara University School of Medicine. All Salmonella isolates were serotyped and investigated for antimicrobial susceptibility. During the 10-year study period, 40 patients with Salmonella bacteraemia were identified. Of 37 eligible children, eight had enteric fever and 29 had non-typhoidal salmonellosis. Salmonella typhimurium was the most common serotype in the group with non-typhoidal salmonellosis. No significant differences were found between the enteric fever and non-typhoidal salmonellosis groups with regard to clinical features, laboratory findings and outcome, except in mean platelet counts and mean serum alanine aminotransferase (ALT) levels. In vitro resistance rates of Salmonella strains were low. Outcome was excellent in all but one child with hydrocephalus and gross neurological sequelae owing to meningitis. Salmonella bacteraemia is relatively uncommon in Turkish children. Differentiating between enteric fever and non-typhoidal Salmonella bacteraemia on clinical grounds is difficult.

Prevalence and antimicrobial susceptibility of serogroup D nontyphoidal Salmonella in a university hospital in Taiwan

The incidence of serogroup D Salmonella has been increasing in Taiwan. Most of these isolates belonged to Salmonella enterica serovar Enteritidis and showed a relatively higher rate of resistance to sulfamethoxazole-trimethoprim than to other antimicrobial agents. The results of molecular experiments indicated that genes responsible for the resistance were located on plasmids. The resistance may occur via horizontal gene transfer. Furthermore, the first identification of ciprofloxacin and ceftriaxone resistance in serogroup D Salmonella in our hospital is also than they did to other antimicrobial agents cause for concern.

Molecular epidemiology of Salmonella enterica serovar Enteritidis isolated in Taiwan

Incidence of Salmonella enterica serovar Enteritidis infection seems to be on the rise in Taiwan, and therefore, the characteristics of the isolate, including genotypes, were epidemiologically investigated. Of the 71 clinical strains isolated in 1997-1999, 61 (86%) remained susceptible to the eight antibiotics tested, while the remaining ten, eight of which were isolated in 1999, were resistant to one to three of the agents including three multiply resistant strains. The majority, 69 or 97% of the isolates, harbored a 60-kb spvC gene-carrying virulence plasmid and 12 of them harbored one or two additional various-sized plasmids. Strains with more than one plasmid were isolated mostly in 1999. Pulse-field gel electrophoresis (PFGE) revealed three major genotypes (Types A, B and C), in which type A was the predominant type. Of the 68 Type A, which contained 8 subtypes, 59 (83%) belonged to only two subtypes. Similar results were obtained with a PCR-based typing method, the infrequent-restriction-site (IRS) PCR. All four methods detected types that were rarely seen before and most of these were of recent isolates, indicating that these unusual types were new or strains of foreign origin. Though all four methods discriminated types well, PFGE and IRS-PCR showed higher sensitivity for classification. Between the two, the latter, though less discriminatory than PFGE, seems the method of choice, since it is simpler, less time-consuming and above all easy to perform.

Current status of antimicrobial resistance in Taiwan

While some trends in antimicrobial resistance rates are universal, others appear to be unique for specific regions. In Taiwan, the strikingly high prevalence of resistance to macrolides and streptogramin in clinical isolates of gram-positive bacteria correlates with the widespread use of these agents in the medical and farming communities, respectively. The relatively low rate of enterococci that are resistant to glycopeptide does not parallel the high use of glycopeptides and extended-spectrum beta-lactams in hospitals. The evolving problem of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates is substantial, and some unique enzymes have been found. Recently, some gram-negative bacteria (e.g., Pseudomonas aeruginosa and Acinetobacter baumannii) that are resistant to all available antimicrobial agents including carbapenems have emerged.