The tangible cost implications of a hospital outbreak of multiply-resistant Salmonella

The Economic Burden of Non-Typhoidal Salmonella and Invasive Non-Typhoidal Salmonella Infection: A Systematic Literature Review

Non-typhoidal Salmonella (NTS) infection and invasive non-typhoidal Salmonella (iNTS) infection cause a significant global health and economic burden. This systematic review aims to investigate the reported economic burden of NTS and iNTS infection, identify research gaps, and suggest future research directions. Data from PubMed and Embase databases up to April 2022 were reviewed, and articles were screened based on predefined criteria. Cost data were extracted, categorized into direct medical costs (DMCs), direct non-medical costs (DNMCs), and indirect costs (ICs), and converted into US dollars (year 2022). Data primarily originated from high-income countries (37 out of 38), with limited representation from Africa and resource-limited settings. For inpatients, DMCs were the primary cost driver for both NTS and iNTS illnesses, with estimates ranging from USD 545.9 (Taiwan, a region of China) to USD 21,179.8 (Türkiye) for NTS and from USD 1973.1 (Taiwan, a region of China) to USD 32,507.5 (United States of America) for iNTS per case. DNMCs and ICs varied widely across studies. Although study quality improved over time, methodological differences persisted. This review underscores the lack of economic data on NTS and iNTS in resource-limited settings. It also highlights the need for economic burden data in resource-limited settings and a standardized approach to generate global datasets, which is critical for informing policy decisions, especially regarding future vaccines.

Ceftiofur-resistant Salmonella enterica serovar Heidelberg of poultry origin - a risk profile using the Codex framework

Codex published the 'Guidelines for Risk Analysis of Foodborne Antimicrobial Resistance' to standardise the approach for evaluating risk posed by foodborne antimicrobial-resistant bacteria. One of the first steps in the guidelines is to compile a risk profile, which provides the current state of knowledge regarding a food safety issue, describes risk management options and recommends next steps. In Canada, ceftiofur/ceftriaxone-resistant Salmonella enterica subsp. enterica serovar Heidelberg from poultry was identified as an antimicrobial resistance (AMR) food safety issue. The first objective of this article was to contextualise this food safety issue, using the risk profile format of the Codex Guidelines. A second objective was to evaluate the applicability of the Codex Guidelines. This risk profile indicated that ceftiofur/ceftriaxone-resistant S. Heidelberg (CSH) was commonly isolated from poultry and was associated with severe disease in humans. Ceftiofur use in poultry hatcheries temporally mirrored the prevalence of CSH from poultry meat at retail and from people with salmonellosis. The evidence was sufficient to indicate the need for risk management options, such as restricting the use of ceftiofur in poultry. The Codex Guidelines provided a useful approach to summarise data for decision-makers to evaluate an AMR food safety issue.

Antimicrobial resistance in Salmonella enterica serovar Heidelberg isolates from retail meats, including poultry, from 2002 to 2006

Salmonella enterica serovar Heidelberg frequently causes food-borne illness in humans. There are few data on the prevalence, antimicrobial susceptibility, and genetic diversity of Salmonella serovar Heidelberg isolates in retail meats. We compared the prevalences of Salmonella serovar Heidelberg in a sampling of 20,295 meats, including chicken breast (n = 5,075), ground turkey (n = 5,044), ground beef (n = 5,100), and pork chops (n = 5,076), collected during 2002 to 2006. Isolates were analyzed for antimicrobial susceptibility and compared genetically using pulsed-field gel electrophoresis (PFGE) and PCR for the bla(CMY) gene. A total of 298 Salmonella serovar Heidelberg isolates were recovered, representing 21.6% of all Salmonella serovars from retail meats. One hundred seventy-eight (59.7%) were from ground turkey, 110 (36.9%) were from chicken breast, and 10 (3.4%) were from pork chops; none was found in ground beef. One hundred ninety-eight isolates (66.4%) were resistant to at least one compound, and 49 (16.4%) were resistant to at least five compounds. Six isolates (2.0%), all from ground turkey, were resistant to at least nine antimicrobials. The highest resistance in poultry isolates was to tetracycline (39.9%), followed by streptomycin (37.8%), sulfamethoxazole (27.7%), gentamicin (25.7%), kanamycin (21.5%), ampicillin (19.8%), amoxicillin-clavulanic acid (10.4%), and ceftiofur (9.0%). All isolates were susceptible to ceftriaxone and ciprofloxacin. All ceftiofur-resistant strains carried bla(CMY). PFGE using XbaI and BlnI showed that certain clones were widely dispersed in different types of meats and meat brands from different store chains in all five sampling years. These data indicate that Salmonella serovar Heidelberg is a common serovar in retail poultry meats and includes widespread clones of multidrug-resistant strains.

Antibacterial activity of Thonningia sanguinea against some multi-drug resistant strains of Salmonella enterica

BACKGROUND

The emergence of strains of S.enterica with multiple drug resistance (MDR) is of great concern worldwide.The extracts of flowers of Thonningia sanguinea are used in traditional medicine in Ivory Coast to treat diarrhoeal diseases including salmonellosis. Previous studies had shown inhibition of the MDR strain Salmonella Enteritidis lysotype 6.

OBJECTIVES

The present study focused to investigate the effect of the extract of the flowers of Thonningia sanguinea on some clinical MDR strains of Salmonella namely S. Tyhpi, S. Typhimurium, S. Hadar and a sensitive strain (S. Enteritidis).

METHODS

The antimicrobial parameters were determined by double dilution with agar slant method. This method led us to determine MIC, IC50 and MBC.

RESULTS

The MDR strain of S.Typhimurium presented the highest MIC (2.5 mg/ml) whereas the other two MDR strains (S. Hadar, S. Typhi) and the sensitive one (S. Enteritidis) had the same MIC (1.25 mg/ml). The four strains presented the same MBC (2.5 mg/ml). The MDR strain of S. Typhi is the most susceptible strain to the aqueous extract of the flowers of Thonningia sanguinea according to The IC50 values.

CONCLUSIONS

The aqueous extract of Thonningia sanguinea can provide an alternative therapy for the treatment of salmonellosis, mainly for typhoid fever caused by MDR strains of S Typhi. The extract also inhibits S.Hadar a MDR emerging strain in Ivory Coast.

Factors influencing the prevalence of Salmonella spp. in swine farms: a meta-analysis approach

A systematic review and meta-analysis was conducted to identify study-level variables that could explain the variation in apparent Salmonella spp. prevalence estimates. Electronic and non-electronic literature searches from 1990 until 2005 were carried out to identify all studies related to the prevalence of subclinical Salmonella infection in swine. The searches were restricted to studies published in English, Spanish, and French. Clinical trials or any other study where an intervention was evaluated were excluded from this analysis. A template was designed to retrieve the most relevant variables and data abstraction was performed in duplicate. A total of 98 papers containing 82 animal-level and 156 farm-level studies were used in the analyses. The median farm-level and animal-level prevalences were 59% and 17%, respectively. Meta-regression analyses were carried out on both farm and animal-level data. Diagnostic procedure, sample size, and country where study was conducted were the three most important predictors in explaining the differences in Salmonella prevalences between studies. When compared to a farm with a apparent prevalence of 50% determined by the blood ELISA, prevalences based on culture of fecal samples were 39% lower and prevalences based on cecum and tissue cultures were 16% and 19% lower, respectively. Similar to farm-level models, animal-level models did not show any difference among serological tests and prevalence values based culture procedures were, on average, 9% lower than those from serological tests. Sample size was negatively associated with prevalence estimates. In conclusion, the methodology was useful for identifying and quantifying sources of variation in Salmonella apparent prevalence among studies and for establishing prevalence distributions that could be used as input parameters in risk assessment and decision models. The analysis provides some guidelines when interpreting and comparing apparent Salmonella prevalence results from studies using different study designs.

Antigen-specific lymphocyte proliferation and interleukin production in chickens immunized with killed Salmonella enteritidis vaccine or experimental subunit vaccines

Lymphocyte proliferation and interleukin (IL)-2 and IL-6 levels in serum were measured as indicators of cell-mediated immunity after immunization of chickens with a commercial killed Salmonella enteritidis (SE) vaccine or experimental subunit vaccines of crude protein (CP) extract or the outer membrane protein (OMP). Significantly increased proliferative responses to SE flagella, but not lipopolysaccharide, porin, CP, or OMP, were observed at 1 wk postimmunizarion in the three vaccination groups. The responses to flagella were specific because flagella-induced proliferation was not seen in chickens immunized with adjuvant alone. Of the three immunization protocols, use of the killed SE vaccine appeared most effective because it induced higher flagella-stimulated lymphocyte proliferation at 1 and 2 wk postvaccination compared with the CP- and OMP-vaccinated groups. Significantly increased IL-2 and IL-6 levels in serum were seen at 1 wk postimmunization in the three vaccination groups compared with adjuvant alone, but there were no differences between the killed vaccine and the subunit vaccines at this time, and the levels of both lymphokines returned to baseline at 2 wk postimmunization. We conclude that cell-mediated immunity to SE after vaccination with the killed bacterial vaccine or subunit vaccines is transient and mainly limited to flagella.

Evaluation of a 24-hour bioluminescent enzyme immunoassay for the rapid detection of Salmonella in chicken carcass rinses

A bioluminescent enzyme immunoassay (BEIA), using Salmonella-specific monoclonal antibody M183 for capture and biotinylated monoclonal antibody M183 for detection, was developed with InteLite AB streptavidin-biotinylated firefly luciferase complex as a reporter. Salmonella cultures were preenriched in buffered peptone water with shaking for 6 h at 37 degrees C and then selectively enriched in Muller-Kauffmann tetrathionate (MKTT) broth and modified semisolid Rappaport-Vassiliadis (MSRV) medium for 16 h at 42 degrees C. After enrichment, the total test time for the BEIA was 1.5 h. The analytical sensitivity of the BEIA ranged from 6.0 x 10(2) CFU/ml to 1.2 x 10(5) CFU/ml in MKTT and from 1.4 x 10(5) to 2.3 x 10(6) CFU/ml in MSRV using six Salmonella serovars prevalent in Canada. With enrichment cultures, the BEIA detected 1 CFU of Salmonella Typhimurium and Salmonella Enteritidis in 25 ml of chicken rinses. Representative strains of 10 Salmonella serovars were detected, and cross-reactivity was not observed with 25 non-Salmonella foodborne bacteria. The BEIA performance was assessed by testing 420 poultry samples, which were analyzed in parallel with the standard MSRV culture method. The BEIA detected 117 (27.88%) Salmonella-positive samples, whereas the standard MSRV culture method detected 124 (29.5%). The BEIA had a sensitivity of 64.5% and a specificity of 87.5% compared to the standard MSRV culture method. However, similar specificities and sensitivities were obtained when the standard MSRV culture method was compared to the BEIA (sensitivity = 68.4% and specificity = 85.5%). Neither method detected 100% of the Salmonella found in the samples tested, and statistical analyses indicated no significant difference between the two methods. In summary, the BEIA offers another alternative for the detection of Salmonella, with the additional advantage of providing a 24-h test for detecting Salmonella in chicken carcass rinses. The results obtained in this research indicate that tests are still needed for the isolation and detection of Salmonella that will establish the true prevalence of Salmonella in chicken samples.

Phage-based typing scheme for Salmonella enterica serovar Heidelberg, a causative agent of food poisonings in Canada

Salmonella enterica serovar Heidelberg is perhaps the second most frequent Salmonella serovar isolated from humans and the most common isolated from animals in Canada. This pathogen has shown increasing resistance to antimicrobial agents and mimics the multidrug resistance observed in S. enterica serovar Typhimurium strain DT 104. However, unlike for serovar Typhimurium, a rapid and inexpensive subtyping method has not been available for large-scale surveillance efforts. We developed a phage typing scheme and subtyped 2,523 strains of serovar Heidelberg from outbreaks, sporadic infections, and environmental sources in Canada between January 1991 and December 2000. All strains were sensitive to one or more phages and could be subdivided into 49 phage types. A total of 196 isolates from 13 major outbreaks could be subtyped into six phage types, while 86 strains from family outbreaks were assigned to seven phage types. All strains were typeable, and epidemiologically related strains isolated from patients and implicated foods had identical phage types, antibiograms, and pulsed-field gel electrophoresis (PFGE) patterns. Combining PFGE with phage typing increased the discriminatory power of the analysis beyond that of either method alone. We concluded that this phage typing scheme, in conjunction with PFGE, enhances subtyping of serovar Heidelberg strains. Furthermore, this phage typing scheme is a rapid, economical, stable, and reliable epidemiologic tool for tracing the origin of food-borne disease and for the surveillance of sporadic infections.

Economic impact of an Escherichia coli O157:H7 outbreak in Japan

We estimated the economic impact of an outbreak of foodborne diseases occurring from elementary school lunches in 1996 in which 268 persons in Iwate prefecture, Japan were infected with Escherichia coli O157:H7. This study assessed the impact of direct economic losses and indirect economic consequences due to this outbreak. The economic impact of the outbreak was estimated to be about 82,686,000 yen. The laboratory costs, about 21,204,000 yen, showed the highest ratio of the total cost of this outbreak (about 26%). Also, the cost of foodstuffs that were not purchased during the suspension of the lunch service (about 19%), personnel expenses paid to lunch service employees (about 17%), human illness costs (about 15%), and the repair costs of facilities (about 15%) showed up as a high ratio in the total cost, respectively. Because all patients were children, the productivity losses estimated were low as children were considered as dependants with no income. Instead, we estimated the lost income of the mothers of the children. The source of the contamination could not be identified. Therefore, no food industries suffered any setbacks where certain food items could not be used for daily consumption due to the outbreak.

An outbreak of multiply-resistant Klebsiella pneumoniae in the Grampian region of Scotland

A predominantly hospital-based outbreak of multiply-resistant Klebsiella pneumoniae capsular type K2 (MRK) expressing expanded spectrum betalactamase (ESBL) activity and fully sensitive only to the carbapenems and amikacin is described. The organism was isolated from 283 patients between March 1992 and September 1995. The outbreak started in the intensive care unit (ICU) of a major acute hospital and spread through surgical wards, a medical ward, a geriatric unit in a separate hospital and various other local hospitals. Environmental screening revealed extensive ward contamination. The decline of the outbreak after the spring of 1995 coincided with the re-emphasis of standard infection control procedures and the launch of a works programme aimed at addressing underlying sites of environmental contamination. Of the 283 cases, 166 (59.0%) were detected through a specially instigated case finding programme. The MRK caused 11 cases of septicaemia, two postoperative intra-abdominal abscesses, one case of postoperative meningitis, 102 cases of urinary tract infection and 28 wound infections and was isolated from the respiratory tracts of five patients with ventilator associated pneumonia. The difficulty in controlling the outbreak is ascribed to heavy environmental contamination, frequent inter- and intra-hospital patient transfers and prolonged carriage of the outbreak strain.

Large scale use of ciprofloxacin in the control of a Salmonella outbreak in a hospital for the mentally handicapped

An outbreak of salmonella food poisoning occurred in a hospital for the mentally handicapped in July 1990. Salmonella enteritidis phage type 4 was identified in 101 patients and eight staff. Standard infection control measures were instituted. Ciprofloxacin was given to all resident patients and to all affected staff. The outbreak was rapidly controlled. There were no new cases after ciprofloxacin was started and there were no clinical relapses. Microbiological relapsers were retreated with ciprofloxacin. A gradual return to normal activity was possible and within two months the hospital was functioning normally. No salmonellae have been identified in the hospital since that time, confirming that the organism was eradicated, rather than just temporarily suppressed.

Costs of an outbreak of wound infections in an orthopaedic ward

An outbreak of serious wound infections occurring in an orthopaedic ward is reported. The outbreak involved 10 patients, all of whom had undergone clean, orthopaedic operative procedures. The outbreak was eventually terminated by discarding five damaged and contaminated mattresses. The costs incurred during this outbreak were calculated using a retrospective comparative study. The infected patients had an average increased hospital stay of 17 days and average increased costs of 2220 pounds. The outbreak demonstrated the high costs of hospital-acquired infection and the need for further investment in infection control programmes.

Pharmacoeconomics of antibacterial treatment

Antibacterial drugs account for between 3 and 25% of all prescriptions, between 6 and 21% of the total market value of drugs in a single country, and up to 50% of the drug budget in hospitals. Bacterial infection is widely perceived as disease caused by harmful outside agents which can be isolated and tested to select the best drug for treatment. In fact, the need for any treatment and the pros and cons of different drugs are just as debatable as in any other therapeutic area. Moreover, the bacteria which make up the normal flora of the body fulfil important roles, so that the ecological implications of treatment for the individual and for society should be considered in assessing the costs and consequences of antibacterial treatment. In this review we outline the most important issues relating to the treatment of bacterial infection in the community and in the hospital, contrasting information from developed and developing countries where appropriate. We review the existing literature on economic evaluation, but in general most of the literature deals with containing the costs of antibacterial drugs in hospitals, and there are many gaps in the literature on cost-effectiveness of treatment. Consequently there are still extreme variations in medical practice which present a challenge for future evaluation. As the outcomes of antibacterial treatment are apparent in a few weeks or months, this is an ideal field for testing pharmacoeconomic methodology. The desire to overcome medical practice variation through consensus statements should be avoided. Instead we recommend wider application of decision analysis to acknowledge that choices exist for the diagnosis and treatment of bacterial infection and to gather information about the implications of these choices. Much of the existing literature would be improved by a more explicit definition of costs. Direct costs to the health services should be distinguished from non medical costs. Moreover, the analysis should consider whether savings from one budget result in costs to another health service budget, or to the patient (transfer costs). These deficiencies in cost analysis will be relatively easy to correct. Of more concern is the fact that the efficacy of much antibacterial treatment is either totally debatable, or variable, depending on factors such as the type of patient treated or the quality of delivery of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Microprocessors for auditing the surveillance activity of the Infection Control Nurse

An important part of the Infection Control Nurse's activity in the UK is the laboratory-based surveillance of patients with infections that are known to be transmissible, i.e. of 'alert' organisms. We have replaced a manual 'T-card' system in which relevant patient information, microbiology and nursing notes are held on all patients yielding 'alert' organisms. The programme is menu driven, requires minimal coding and runs on a microprocessor with a hard disc. The programme enables surveillance patient information to be entered, edited, archived and recorded. Instant retrieval on screen or hard copy includes summarized or full displays of all patients on all wards, sorted by wards, organism, date or risk category. Archived data may be retrieved within minutes and this avoids having to interrogate the whole laboratory database overnight. To illustrate an additional use of the data stored, we analysed the surveillance activities of the Control of Infection Nurse for one year. Of 203 laboratory diagnoses requiring patient surveillance, 30% were viral infections, of which more than two-thirds were caused by hepatitis B virus; of the 142 bacterial isolates, 27% were multiply antibiotic-resistant Enterobacteriaceae, 25% Pseudomonas spp, 12% Salmonella spp., 9% methicillin-resistant Staphylococcus aureus (MRSA), 7% Group A streptococci and 8% meningococci. These isolates resulted in only four outbreaks involving nine patients or staff. This information has proved useful for auditing the nurse's activity and provides evidence for the cost-effectiveness of infection control.

A pseudo-outbreak of Pseudomonas on a special care baby unit

Following isolation of a multi-antibiotic-resistant pseudomonad from a newborn infant on admission to the Special Care Baby Unit and further isolation of apparently the same organism from two additional infants, a full investigation was instigated in an attempt to discover the source of the organism. This revealed a further 13 infants apparently colonized with the same organism. Repeated screening of the infants with a commercial sterile swab/transport medium failed to isolate the organism. Examination of bottles of the in-house transport medium, which had been stored under a sink, produced further isolates of the same organism. Water splashed from the sink was suspected as the ultimate source of contamination. Biochemical characterization showed that P. pickettii and at least one other Pseudomonas species were involved. The epidemiological, clinical and economic implications of the 'outbreak' are discussed together with the ultimate financial implications for investigation of such incidents.