Septicemia caused by vancomycin-resistant Pediococcus acidilactici

Pediococcus pentosaceus Endocarditis in a Patient With Recent Transcatheter Aortic Valve Implantation and Liver Cirrhosis: A Case Report and Review of the Literature

Transcatheter aortic valve implantation (TAVI) is increasingly being used in the management of severe aortic stenosis, mainly in older and/or medically compromised patients, due to its minimally invasive nature. As in any valve replacement procedure, endocarditis is a recognized complication, more so in TAVI patients, in whom comorbidities are highly prevalent. We report the case of a 70-year-old male with a history of liver cirrhosis and a recent TAVI, who presented with recurrent fever and sustainedPediococcus pentosaceus bacteremia. The diagnosis of endocarditis was delayed, as the microorganism was initially discarded as a contaminant, given that Pediococci are rarely described as human pathogens. However, in cirrhotic patients, microbiota may cause intermittent bacteremia and thereby affect prosthetic valves. Transthoracic echocardiography was not helpful in validating the diagnosis, as is often the case in TAVI patients. Transesophageal echocardiography was deemed perilous, due to esophageal varices complicating the underlying cirrhosis. Therefore, endocarditis diagnosis was based on sustained bacteremia and Duke's criteria, including the presence of high fever, a predisposing cardiac lesion, splenic infarction, and the exclusion of an alternative diagnosis. Moreover, cirrhosis enhanced the side effects of treatment and led to the need for regimen changes and prolonged hospitalization. Given the precariousness of the situation, confirmation of treatment success by 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron emission tomography-computed tomography (18F-FDG PET-CT) scan was sought. This is the first reported case of Pediococcus TAVI endocarditis in a cirrhotic patient, highlighting the unique challenges in the diagnosis and management of TAVI endocarditis in patients with co-existing conditions.

Resolution of Pediococcus acidilactici bacteremia without antibiotic therapy in a 16-year-old adolescent with leukemia receiving maintenance chemotherapy

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P. acidilactici infection can be self-limiting, even in immunocompromised hosts.

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P. acidilactici infection can occur in dasatinib-induced hemorrhagic colitis.

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Dairy products consumers can cause P. acidilactici bacteremia.

Pediococcus spp. have been reported to cause infections in patients with underlying conditions. However, the pathogenicity of this bacteria is unclear. Herein, we describe the first case of Pediococcus acidilactici bacteremia, which occurred in a 16-year-old male with dasatinib-induced hemorrhagic colitis during maintenance therapy for leukemia and resolved without antibiotic treatment. P. acidilactici bacteremia might be self-limiting, even in immunocompromised patients receiving chemotherapy.

Update on Tetracycline Susceptibility of Pediococcus acidilactici Based on Strains Isolated from Swiss Cheese and Whey

Bacterial strains used as starter cultures in the production of fermented foods may act as reservoirs for antibiotic resistance (AbR) genes. To avoid the introduction of such genes into the food chain, the presence of acquired AbR in bacterial strains added to food must be tested. Standard protocols and microbiological cut-off values have been defined to provide practitioners with a basis for evaluating whether their bacterial isolates harbor an acquired resistance to a given antibiotic. Here, we tested the AbR of 24 strains of Pediococcus acidilactici by using the standard protocol and microbiological cut-off values recommended by the European Food Safety Authority. Phenotypic data were complemented by searching for known AbR genes using an in silico analysis of whole genomes. The majority (54.2%) of the strains were able to grow at a tetracycline concentration above the defined cut-off, even though only one strain carried a known tetracycline resistance gene, tetM. The same strain also carried the AbR gene of an erythromycin resistance methylase, ermA, and displayed resistance toward clindamycin and erythromycin. Our results bolster the scarce data on the sensitivity of P. acidilactici to tetracycline and suggest that the microbiological cut-off recommended by the European Food Safety Authority for this antibiotic should be amended.

Resolution of persistent Pediococcus bacteremia with daptomycin treatment: case report and review of the literature

A case of bacteremia caused by Pediococcus acidilactici occurring in a patient with metastatic adenocarcinoma of the gallbladder is described. The bacteremia persisted despite an antimicrobial regimen of vancomycin, ciprofloxacin, metronidazole, and caspofungin. Within 36 h of switching the vancomycin to daptomycin (6 mg/kg per day), the bacteremia resolved and the patient improved clinically. Previous reports of human pediococcal infection are also reviewed.

Bacteremic infection with Pediococcus: vancomycin-resistant opportunist

Pediococci are recently recognized Gram-positive human pathogens, resistant to vancomycin and generally susceptible to penicillin. Infection in adults has been seen in patients with chronic underlying conditions as well as those with previous abdominal surgery. Two previous infants with congenital gastrointestinal malformations requiring surgical correction have been reported with sepsis attributable to Pediococcus sp. We report a third infant born with gastroschisis who developed Pediococcus bacteremia and meningitis 3 months after surgery, and speculate regarding the role of probiotics in the pathogenesis of this infection.

Quinupristin-dalfopristin resistance among gram-positive bacteria in Taiwan

To understand quinupristin-dalfopristin resistance among clinical isolates of gram-positive bacteria in Taiwan, where this agent is not yet available for clinical use, we evaluated 1,287 nonduplicate isolates recovered from January 1996 to December 1999 for in vitro susceptibility to quinupristin-dalfopristin and other newer antimicrobial agents. All methicillin-susceptible Staphylococcus aureus (MSSA) isolates were susceptible to quinupristin-dalfopristin. High rates of nonsusceptibility to quinupristin-dalfopristin (MICs, >/=2 microg/ml) were demonstrated for the following organisms: methicillin-resistant S. aureus (MRSA) (31%), coagulase-negative staphylococci (CoNS) (16%), Streptococcus pneumoniae (8%), viridans group streptococci (51%), vancomycin-susceptible enterococci (85%), vancomycin-resistant Enterococcus faecalis (100%), vancomycin-resistant Enterococcus faecium (66%), Leuconostoc spp. (100%), Lactobacillus spp. (50%), and Pediococcus spp. (87%). All isolates of MSSA, MRSA, S. pneumoniae, and viridans group streptococci were susceptible to vancomycin and teicoplanin. The rates of nonsusceptibility to vancomycin and teicoplanin were 5 and 7%, respectively, for CoNS, ranging from 12 and 18% for S. simulans to 0 and 0% for S. cohnii and S. auricularis. Moxifloxacin and trovafloxacin had good activities against these isolates except for ciprofloxacin-resistant vancomycin-resistant enterococci and methicillin-resistant staphylococci. In Taiwan, virginiamycin has been used in animal husbandry for more than 20 years, which may contribute to the high rates of quinupristin-dalfopristin resistance.

In vitro activities of ketolide HMR3647, macrolides, and other antibiotics against Lactobacillus, Leuconostoc, and Pediococcus isolates

Testing of susceptibility to 13 antibiotics was performed with 90 isolates of Lactobacillus, Leuconostoc, and Pediococcus. MICs at which 90% of the isolates tested were inhibited by HMR3647, erythromycin, and ciprofloxacin were 0.015, 0.125 and 32 microg/ml, respectively. The penicillin MIC was > or = 16 microg/ml against 26.2% of the studied Lactobacillus sp. isolates and 50% of Lactobacillus plantarum. HMR3647 showed excellent activity against these genera.

Intrinsically vancomycin-resistant gram-positive organisms: clinical relevance and implications for infection control

Intrinsic resistance to vancomycin in gram-positive bacteria presumably predates acquired vancomycin resistance in enterococci but it has only recently generated interest. Intrinsically resistant enterococci possessing the vanC gene and the non-enterococcal genera Leuconostoc, Lactobacillus, Pediococcus and Erysipelothrix are known to cause human infection. This review examines the available data on their identification, resistance mechanisms, epidemiology, clinical infections and antimicrobial susceptibility. Intrinsically vancomycin-resistant gram-positives are usually opportunistic pathogens. Although serious infections may occur, treatment options remain available. No additional infection control measures for the intrinsically resistant genera appear justified with currently available evidence, although vigilance should be maintained to detect future changes in susceptibility patterns.

Current perspectives on glycopeptide resistance

In the last 5 years, clinical isolates of gram-positive bacteria with intrinsic or acquired resistance to glycopeptide antibiotics have been encountered increasingly. In many of these isolates, resistance arises from an alteration of the antibiotic target site, with the terminal D-alanyl-D-alanine moiety of peptidoglycan precursors being replaced by groups that do not bind glycopeptides. Although the criteria for defining resistance have been revised frequently, the reliable detection of low-level glycopeptide resistance remains problematic and is influenced by the method chosen. Glycopeptide-resistant enterococci have emerged as a particular problem in hospitals, where in addition to sporadic cases, clusters of infections with evidence of interpatient spread have occurred. Studies using molecular typing methods have implicated colonization of patients, staff carriage, and environmental contamination in the dissemination of these bacteria. Choice of antimicrobial therapy for infections caused by glycopeptide-resistant bacteria may be complicated by resistance to other antibiotics. Severe therapeutic difficulties are being encountered among patients infected with enterococci, with some infections being untreatable with currently available antibiotics.

Identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci

Several new genera and species of gram-positive, catalase-negative cocci that can cause infections in humans have been described. Although these bacteria were isolated in the clinical laboratory, they were considered nonpathogenic culture contaminants and were not thought to be the cause of any diseases. Isolation of pure cultures of these bacteria from normally sterile sites has led to the conclusion that these bacteria can be an infrequent cause of infection. This review describes the new bacteria and the procedures useful for clinical laboratories to aid in their identification. The clinical relevance and our experience with the various genera and species are reviewed and discussed.

Catheter-related septicemia caused by a vancomycin-resistant Coryneform CDC group A-5

A case of catheter-related septicemia, due to Coryneform CDC group A-5, in an 11 yr old boy with acute myelomonocytic leukemia is discussed. The child failed to respond to initial antibiotic therapy, even following the addition of vancomycin. Laboratory studies later showed the organism to be vancomycin resistant but cefotaxime susceptible.

Antimicrobial susceptibility of Pediococcus spp. and genetic basis of macrolide resistance in Pediococcus acidilactici HM3020

We determined the MICs of 28 antimicrobial agents against 36 clinical strains of Pediococcus spp. (25 P. acidilactici, 9 P. pentosaceus, and 2 P. urinaeequi strains). Penicillin G, imipenem, gentamicin, netilmicin, erythromycin, clindamycin, rifampin, chloramphenicol, daptomycin, and ramoplanin were the most active. All strains of P. acidilactici were susceptible to novobiocin, whereas all isolates of P. pentosaceus were resistant. Novobiocin could therefore be helpful for differentiation of these two closely related species. P. acidilactici HM3020 was inducibly resistant to macrolide, lincosamide, and streptogramin B-type (MLS) antibiotics. Resistance was due to a determinant homologous to ermAM and carried by a nontransferable 46-kb plasmid, pVM20. This plasmid was structurally distinct from two enterococcal MLS resistance plasmids, pIP819 and pAM beta 1. The 34 strains of P. acidilactici and P. pentosaceus were resistant to tetracycline, and total DNA of these strains did not hybridize to probes specific for tetK, tetL, tetM, and tetO.

Septicemia and hepatic abscess caused by Pediococcus acidilactici

A case of postoperative Pediococcus acidilactici septicemia with parallel isolation of the organism from hepatic specimens is presented. Laboratory methods to identify this vancomycin-resistant gram-positive cocci are described. Very few cases of documented infections due to this bacterium have been reported in the literature.

Septicaemia caused by Pediococcus pentosaceus: a new opportunistic pathogen

A case of septicaemia caused by Pediococcus pentosaceus is described. The role played by pediococci, and other vancomycin-resistant Gram-positive cocci, in disease states is examined. We suggest that in immunocompromised patients these organisms act as opportunist pathogens. This would appear to be the first reported case of P. pentosaceus septicaemia.