Gas-producing Bacteria Research Articles

US/PA/MR multimodal imaging-guided multifunctional genetically engineered bio-targeted synergistic agent for tumor therapy

Focused ultrasound ablation surgery (FUAS) is a minimally invasive treatment option that has been utilized in various tumors. However, its clinical advancement has been hindered by issues such as low safety and efficiency, single image guidance mode, and postoperative tumor residue. To address these limitations, this study aimed to develop a novel multi-functional gas-producing engineering bacteria biological targeting cooperative system. Pulse-focused ultrasound (PFUS) could adjust the ratio of thermal effect to non-thermal effect by adjusting the duty cycle, and improve the safety and effectiveness of treatment.The genetic modification of Escherichia coli (E.coli) involved the insertion of an acoustic reporter gene to encode gas vesicles (GVs), resulting in gas-producing E.coli (GVs-E.coli) capable of targeting tumor anoxia. GVs-E.coli colonized and proliferated within the tumor while the GVs facilitated ultrasound imaging and cooperative PFUS. Additionally, multifunctional cationic polyethyleneimine (PEI)-poly (lactic-co-glycolic acid) (PLGA) nanoparticles (PEI-PLGA/EPI/PFH@Fe3O4) containing superparamagnetic iron oxide (SPIO, Fe3O4), perfluorohexane (PFH), and epirubicin (EPI) were developed. These nanoparticles offered synergistic PFUS, supplementary chemotherapy, and multimodal imaging capabilities.GVs-E.coli effectively directed the PEI-PLGA/EPI/PFH@Fe3O4 to accumulate within the tumor target area by means of electrostatic adsorption, resulting in a synergistic therapeutic impact on tumor eradication.In conclusion, GVs-E.coli-mediated multi-functional nanoparticles can synergize with PFUS and chemotherapy to effectively treat tumors, overcoming the limitations of current FUAS therapy and improving safety and efficacy. This approach presents a promising new strategy for tumor therapy.Graphical

Raman Spectroscopy Applied to Early Detection of Clostridium Infection in Milk.

Detecting Clostridium in milk presents a significant challenge for the dairy industry given that traditional methods are time-consuming and not specific for these bacteria. Microbiological techniques are expensive and require qualified personnel. Clostridium, in the form of spores, can withstand pasteurization and revert to its vegetative form during cheese aging. These gas-producing bacteria are known for their production of carbon dioxide and hydrogen, causing the formation of slits, cracks, and irregular eyes in hard and semi-hard cheeses. However, gas analysis in the vial headspace of appropriate culture can be exploited to specifically detect Clostridium presence, since the closest competing bacterial Bacilli produces only carbon dioxide. The aim of this paper is to present a Raman-spectroscopy-based instrument for a rapid, inexpensive identification of Clostridium in milk with a limit of detection of 29 spores/L. The proposed measurement procedure is analog to that routinely used, based on the most probable number method. The Raman-based instrument speeds up the detection of a vial's positivity. A test conducted with Clostridium spores demonstrated its effectiveness in almost halving the time needed for the measurement campaign compared to the traditional method.

Klebsiella aerogenes is indeed a gas producing bacteria

Pancreas cancer with peritoneal involvement was found in a 64-year-old man for which he received 5-fluorouracile, folinic acid and oxaliplatin.

Identification and control of gas-producing bacteria isolated from the swollen bagged soy sauce

The swelling of soy sauce bags seriously affects product quality and causes food safety problems, which has become an urgent problem to solve in the condiment industry. Here, gas-producing bacteria in the swollen bagged soy sauce were isolated and identified to provide an effective control method for inhibiting their growth and solving the swelling of soy sauce bags. It was found that three gas-producing bacteria isolated from the swollen bagged soy sauce were confirmed as Bacillus amyloliquefaciens (G1), Bacillus sp. (G2) and Bacillus subtilis (P3) using 16S rDNA analysis. The strains' morphologies, growth rates, and physiological and biochemical characteristics were also compared. Further studies yielded the optimal growth time, temperature and pH for the three gas-producing bacteria (B. amyloliquefacien: 24 h, 37 °C, and pH 7; Bacillus sp.: 18 h, 30 °C, and pH 6.5–7.5; B. subtilis: 36 h, 30 °C, and pH 8). Bacillus sp. was more salt tolerant than the other two. Then the antibacterial effect of the combination was tested by the physicochemical index. The results showed that filtering through a 0.22 μm inorganic micro-filtration membrane, sterilizing at 121 °C for 2 min, and adding 1 g/kg potassium sorbate was effective methods to inhibit three gas-producing bacteria and control the swelling of soy sauce.

Isolation and characterization of a gas-producing and acid-resistant bacterium from spoiled vinegar

To understand the deterioration of vinegar that has frequently occurred in China recently and to address such a concern, the physicochemical indicators and bacterial structure of the spoiled vinegar collected from Sichuan were preliminarily investigated. Results showed that Lactobacillaceae was most likely responsible for the decrease of vinegar total sugar and furfural, through which total acid and furfuryl alcohol were generated. Then, an unreported difficult-to-cultivate gas-producing bacterium named Z-1 was isolated using a modified MRS medium. Strain Z-1 was identified as Acetilactobacillus jinshanensis subsp. aerogenes on the basis of physiological, biochemical, molecular biological and whole genome analyses. According to the investigation, such species was present throughout the fermentation process and not limited in Sichuan. The analysis of genetic diversity indicated that all the obtained A. jinshanensis isolates displayed high sequence similarity and an absence of recombination. Although it demonstrated acid resistance, Z-1 could be completely deactivated through heating (60 °C). Based on the above results, suggestions for safe production are made for vinegar enterprises.

Isolation of toxic gas-producing bacteria (Desulfovibrio spp.) from shrimp ponds and potential of bacteriophages as biocontrol

Isolation of toxic gas-producing bacteria (Desulfovibrio spp.) from shrimp ponds and potential of bacteriophages as biocontrol

OA20 Pneumatosis intestinalis with spontaneous pneumoperitoneum in a patient with systemic sclerosis-myositis overlap syndrome: a case report and review of the literature

OA20 Pneumatosis intestinalis with spontaneous pneumoperitoneum in a patient with systemic sclerosis-myositis overlap syndrome: a case report and review of the literature

The Gastrointestinal Microbiome in Infant Colic: A Scoping Review.

The significant crying of infantile colic adds stress to the infant and their family, yet it has no recognized etiology. Gastrointestinal health problems and dysfunction have been suspected in the etiology of colic. Disruptions to the microbiome colonization of the gastrointestinal system may lead to excess gas and inflammation that are associated with the crying of colic. Infants with colic have increased colonization with gas-producing bacteria, like Escherichia coli and Klebsiella , and they have lower colonization of anti-inflammatory bacteria, like Bifidobacterium and Lactobacillus . Colic is known to self-resolve around 3 months of age. However, few researchers have investigated how the microbiome may be changing at colic's natural resolution without the intervention of a probiotic. With a better understanding of what leads to colic's self-resolution, future researchers may be able to identify more effective therapies for colic prevention or treatment. This scoping review presents the collective evidence from 21 original, primary research articles on what is known about the gastrointestinal microbiome at colic onset and resolution.

Occlusive Syndrome Revealing Emphysematous Gastritis: A Case Report

Emphysematous gastritis is a rare form of infection affecting the gastric wall, characterised by the presence of gas in the wall caused by gas-producing bacteria. This entity was first described by Fraenkel in 1889. Its prognosis is poor with a very high mortality, requiring early diagnosis and treatment. The clinical picture is not specific. Imaging plays an essential role in the diagnosis and the therapeutic management is essentially based on antibiotics in the absence of complications. We report the case of a 29 years old female patient with no specific pathological history who was admitted with a febrile obstruction syndrome. The diagnostic approach confirmed emphysematous gastritis.

Effects of Different Feeding Methods on the Structure, Metabolism, and Gas Production of Infant and Toddler Intestinal Flora and Their Mechanisms.

In this study, we evaluated the effects of different feeding methods on the characteristics of intestinal flora and gas production in infants and toddlers by using an in vitro simulated intestinal microecology fermentation and organoid model. We found that the feeding method influences intestinal gas and fecal ammonia production in infants and toddlers. Supplementation with milk powder for infants in the late lactation period could promote the proliferation of beneficial bacteria, including Bifidobacteria. Intestinal flora gas production in a culture medium supplemented with fucosyllactose (2′-FL) was significantly lower than that in media containing other carbon sources. In conclusion, 2′-FL may reduce gas production in infant and toddler guts through two mechanisms: first, it cannot be used by harmful intestinal bacteria to produce gas; second, it can inhibit intestinal mucosa colonization by harmful bacteria by regulating the expression of intestinal epithelial pathogenic genes/signaling pathways, thus reducing the proliferation of gas-producing harmful bacteria in the gut.

Pneumocephalus and Suppurative Meningoencephalitis in a Dog after Craniofacial Trauma

Background: Pneumocephalus is characterized by the presence of gas in the intracranial compartment, and it can develop because of trauma or craniofacial surgery or spontaneously. Clinical signs start within days or months after the injury and vary according to the site of involvement. Computed tomography is the ideal diagnostic tool, however skull radiography can also be used. Treatment varies according to the severity of the case, and it can be conservative or associated with surgical intervention in the most severe cases. The purpose of this report is to describe the case of a dog that developed pneumocephalus and suppurative meningoencephalitis after head trauma caused by a bite from another dog. Case: A 2-month-old bitch, mixed breed, with 3.2 kg, was referred to the veterinary hospital because it had been bitten on the head by another dog. Shortly after the incident, the animal showed no clinical signs. However, 2 days later, the bitch became depressed and in persistent lateral decubitus. A lesion with a crust of approximately 0.5 cm was found close to the occipital region, with bone irregularity on palpation. The animal was in lateral decubitus with muscular hypotonia, bilateral mydriasis unresponsive to light and stupor. Radiographic images showed parietal fracture and pneumocephalus. Based on the findings of physical and laboratorial exams, diagnosis of suppurative meningoencephalitis and pneumocephalus secondary to craniofacial trauma was established. Empirical broad-spectrum antimicrobial therapy was started in addition to mannitol, corticoids, and analgesics. The animal was referred for surgical debridement by trepanation, when samples were collected to bacterial culture, which was negative. Despites the care, the animal died 14 h after the surgical procedure. Histopathological examination of the frontal cortex was performed, being the histological changes compatible with suppurative meningoencephalitis. Discussion: Dog bites on the head and neck are particularly severe, and can create intracranial bleeding, disfigurement of the face, damage to peripheral structures or cranial fractures. In this report, through radiographic images, it was found that the patient had an intracerebral aerocele, since there was presence of gas in the intracranial compartment. This alteration should always be considered in animals with neurological alterations and a history of craniofacial trauma. The main neurological changes observed in the reported case were unresponsive to mydriasis and altered mental status 2 days after the trauma, and this delay in the onset of clinical signs is frequently reported in cases of pneumocephalus. Neutrophilia and leukocytosis observed can be justified by the suppurative meningoencephalitis, confirmed by the histopathological exam. Antimicrobial therapy should be started as soon as possible, and the choice must be based on their capacity to cross the blood-brain barrier and the broad spectrum. The administration of antibiotics before collecting the material for bacterial culture may explain the negative result of this test, so that it is not possible to determine whether the intracranial gas observed on the radiograph may have developed from the trauma or because of gas-producing bacteria. Head trauma can induce suppurative meningoencephalitis and pneumocephalus even in the absence of perforating wounds at the time of the consultation. The neurological signs can start days after the trauma. Besides the clinical and surgical treatments, the prognosis of any bacterial infection of the central nervous system is poor. Keywords: aerocele, brain syndrome, Glasgow scale, radiography, trepanation.

Human gut metatranscriptome changes induced by a fermented milk product are associated with improved tolerance to a flatulogenic diet

Healthy plant-based diets rich in fermentable residues may induce gas-related symptoms, possibly mediated by the gut microbiota. We previously showed that consumption of a fermented milk product (FMP) containing Bifidobacterium animalis subsp. lactis CNCM I-2494 and lactic acid bacteria improved gastrointestinal (GI) comfort in response to a flatulogenic dietary challenge in healthy individuals. To study the effects of the FMP on gut microbiota activity from those participants, we conducted a metatranscriptomic analysis of fecal samples (n = 262), which were collected during the ingestion of a habitual diet and two series of a 3-day high-residue challenge diet, before and following 28-days of FMP consumption.Most of the FMP species were detected or found enriched upon consumption of the product. FMP mitigated the effect of a flatulogenic diet on gas-related symptoms in several ways. First, FMP consumption was associated with the depletion of gas-producing bacteria and increased hydrogen to methane conversion. It also led to the upregulation of activities such as replication and downregulation of functions related to motility and chemotaxis. Furthermore, upon FMP intake, metabolic activities such as carbohydrate metabolism, attributed to B.animalis and S.thermophilus, were enriched; these activities were coincidentally found to be negatively associated with several GI symptoms. Finally, a more connected microbial ecosystem or mutualistic relationship among microbes was found in responders to the FMP intervention.Taken together, these findings suggest that consumption of the FMP improved the tolerance of a flatulogenic diet through active interactions with the resident gut microbiota.

Investigation of gas-producing bacteria in sufu and its effective method to control their growth

The presence of gas-producing bacteria in sufu will cause the package swelling, thus significantly affecting the storage period and sensory quality of sufu. This study aimed to isolate and identify the gas-producing bacteria in sufu and provide an effective method to control their growth. The gas-producing bacteria were isolated in sufu and identified as Weissella confusa and Weissella koreensis based on 16S rDNA. W. confusa and W. koreensis still grow and produce gas in MRS broth with a salinity of 10% oralcohol of 11% content. Nisin and Lactococcus lactis were able to inhibit the growth of W. confusa and W. koreensis, while no inhibition was observed when sodium propionate, sodium dehydroacetate, and ε-polylysine hydrochloride were used. When the salinity and alcohol content was 6%, the growth of W. confusa was inhibited at MICs of nisin of 0.250 mg mL−1 and 0.125 mg mL−1, while the growth of W. koreensis was inhibited to 0.125 mg mL−1 and 0.063 mg mL−1. Nisin and L. lactis induced changes in cell morphology by disrupting membrane integrity of gas-producing bacteria. This study guides the sufu enterprises to adopt effective measures controlling the package swelling of sufu production and extending the products' storage period.

EMPHYSEMATOUS PYELONEPHRITIS IN RENAL TRANSPLANT RECIPIENT

Introduction: Emphysematous pyelonephritis (EPN) is a necrotizing infection caharacterized by the presence of gas in the renal parenchyma, collecting system and peri- renal tissues. It´s a life threatening disease, nonspecific presentation, extremely rare in transplant recipients. Associated factors are: Diabetes mellitus, female sex, inmunosuppresion, urinary tract obstruction, and impaired vascular supply. It´s typically caused by gas producing bacteria such as Escherichia coli and Klebsiella pneumonia. We report a case of EPN in a transplant recipients. Case Description: 63-year-old male patient with end-stage renal failure due to polycystic disease. Kidney transplant with deceased donor in December 2017. There is no history of urinary stent, diabetes, rejection or obstruction of the urinary tract. Urinary tract colonization with Klebsiella pneumoniae producing extended spectrum Betalactamases (BLEE). In January 2020 consulted for deterioration of the general state, vomiting, diarrhea, anuria. TA: 100/60 FC: 120 FR: 22 SAT 89% FIO2 21%. He had no fever, urinary symptoms, graft site pain or signs of peritoneal irritation. Immunosuppression with meprednisone and mycophenolate. Leukocytes 9100 103 / mm3, neutrophils 82%, Platelets 192000 103 / mm3, hb 7.3 g / dl. Creatinine 2.70 mg%. Urinary sediment: semi-covered leukocyte field. Start empirical treatment with Meropenen. Graft echodoppler without collections or urostasis, with normal arterial resistance indices. For the first 24 hours, afebrile continues, with pain in the right hypochondrium. Ultrasound with presence of air bubbles in upper and lower calyces. Tomography with densification of the perirenal fat and presence of bubbles at the level of the renal sinus. Nephrostomy is performed. Uroculture: Klebsiella pneumoniae BLEE, negative blood cultures, negative coproculture, negative Clostridium difficile toxin, CMV viral load <100 copies. Patient completed 3 weeks of intravenous treatment. Continue with ertapenem.He with clinical, laboratory parameters and imaging improvement. Discussion: Emphysematous pyelonephritis has a high mortality. Of 29 cases reviewed 93% were diabetic, the rest were observed obstructive uropathy and a case of rejection. The 58.6% required transplantectomy, 27.5% antibiotic treatment with percutaneous drainage, 13.7% antibiotic management. The 13.7% died, 44.8% entered hemodialysis and 41% recovered renal function. The predominant germ was Escherichia coli (41.3%) and Klebsiella pneumoniae (34.4%). In our case as a only risk factor was chronic colonization by Klebsiella pneumoniae. According to the staging of Geizawi corresponded to a stage 2, so it was managed with antibiotic therapy and percutaneous drainage with favorable evolution. For this reason we highlight the importance of knowledge of the microbiological colonization of the urinary tract for early diagnosis and targeted therapy.

Analysis and control of microbial gas production in fermented chili paste

In this work, the fermented chili pastes of normal samples (NS) and abnormal samples (ANS, aerogenic samples) were analyzed. The gas produced in the ANS was carbon dioxide. The kinds of bacteria genus were the same in both samples. However, concentrations of Bacillus and Clostridium in ANS were higher than those in NS. This finding indicated that they might be the potential bacteria for gas production. Gas-producing bacteria Bacillus amyloliquefaciens and Clostridium perfringens were isolated from the ANS. Antagonistic strain of Lactobacillus plantarum LM1-3 was isolated from the NS. Orthogonal experiment was performed to inhibit gas production using L. plantarum LM1-3 combined with NaCl and acetic acid. As a result, gas production could be inhibited under 30 °C for more than 30 days under the optimal composition of 12.00% NaCl, 2.7% acetic acid, and 105 CFU/g L. plantarum LM1-3. Otherwise, aerogenesis defect was observed at the 5th day in the control. Practical applications Many fermented chili paste products do not undergo sterilization with high temperature to ensure the natural flavor. Aerogenesis of fermented chili paste after packaging might happen. High salt and acid pressures are used to prevent aerogenesis, however, they will have a negative impact on taste under high concentration. Lactobacillus plantarum, which are generally recognized as safe, can not only inhibit aerogenesis, but also is recognized as a probiotic strain. Therefore, the composition of fermented chili paste was optimized by using acetic acid, salt, and L. plantarum that was isolated from fermented chili paste to inhibit the aerogenesis.

MON-688 Emphysematous Gastritis and Diabetes

Background: Emphysematous gastritis (EG) is a rare and severe form of gastritis of infectious origin. Diabetes is an important underlying risk factor as it leads to a systemic predisposition to infections. Other risk factors include long term steroid use, nonsteroidal anti-inflammatory (NSAID) use, alcohol use, corrosive ingestion, and pancreatitis, all of which disrupt gastric mucosa. First described in the 1800s, it is characterized by the presence of air in the stomach wall and differentials for these cases include gastric emphysema and cystic pneumatosis both of which are non-infectious in origin. Clinical Case: A 57-year-old male with type 2 diabetes presented with a one-day history of abdominal pain, non-bloody diarrhea, and vomiting. One day prior to presentation, he developed diarrhea which was followed by episodes of projectile vomiting reported as orange-tinged with mucus. On the day of admission, he was afebrile, tachycardic in 120s with stable blood pressure. Laboratory evaluation was significant for leukocytosis at 18.8 k/uL (4.3–11.3 k/uL) and lactic acidosis 2.37 mmol/L (0.7–2.1 mmol/L). Abdominal examination was notable for soft abdomen with diffuse tenderness to deep palpation without rebound or guarding. Further workup with Computed Tomography (CT) was concerning for emphysematous gastritis with air in the gastric vein, splenic vein, and portal vein. Given hemodynamic stability and benign abdominal examination, medical management was initiated. He was started on ceftriaxone and metronidazole which were continued for a total of 10 days with clinical improvement. Discussion: EG results from disruption in gastric mucosa which facilitates translocation of gas-producing bacteria commonly Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa, and Enterobacter subspecies. Immunosuppression with diabetes is an important underlying factor and patients are at risk even with controlled diabetes. Additionally, patients with diabetic complications like gastroparesis with frequent retching are at increased risk. Considering variable and non-specific symptoms of presentation, a high index of clinical suspicion is required for recognition as it may have a fulminant course with high mortality risk. CT scan is the imaging of choice for diagnosis. Management primarily consists of bowel rest, antibiotics and monitoring for signs of peritonitis. In the absence of complications including rupture or stricture formation, surgery is not recommended. In our case, possible gastroenteritis with subsequent vomiting and retching in the setting of underlying diabetes predisposed to the development of emphysematous gastritis. Although air in the portal venous system is associated with higher mortality, our patient was successfully managed conservatively. As the diagnosis carries a high mortality risk, early recognition is imperative for a successful outcome.

Emphysematous gastritis due to Sarcina ventriculi infection in a diabetic liver-kidney transplant recipient

ABSTRACTEmphysematous gastritis (EG) is a rare and potentially lethal process caused by invasive, gas-producing bacteria leading to inflammation and gas dissection of the stomach. The most common etiologic agents are Clostridium infections, but other organisms, including enterobacteria, staphylococcus, and fungi have also been identified. We report the first case of EG due to Sarcina ventriculi in a solid organ transplant recipient, who presented with epigastric pain and vomiting. The patient had a history of type 1 diabetes mellitus (DM) with recurrent episodes of ketoacidosis and systemic diabetic complications, including severe gastroparesis. CT scan studies demonstrated EG with venous air, and endoscopy showed severe gastritis and ulcerations. In the gastric biopsies, abundant Sarcina ventriculi were noted in areas of mucosal/submucosal necrosis. Antibiotic treatment was instituted at admission, and subsequent endoscopy demonstrated the disappearance of Sarcina, with some improvement of the gastric inflammation; however, the patient developed septic shock with multiorgan failure and expired. This case highlights the need to consider other infectious etiologies in transplant patients, in addition to the well-known opportunistic infections.

A case of alcohol-related emphysematous cystitis

Emphysematous cystitis (EC) is a very rare urinary tract infectious disease that can be fatal if not treated. In general, it frequently occurs in diabetic women and is thought to be associated with gas-producing bacteria. Type 2 diabetes mellitus, immunosuppression, drugs (mostly steroids), neurogenic bladder and instrumentation are the major risk factors of this type of infection.&#x0D; We present a case of emphysematous cystitis in a 53-year-old male, in which the patient does not have any classical risk factors associated with EC other than alcohol consumption. To the best of our knowledge, the only case in the literature where this type of infection develops without a classical risk factor and negative urine culture. It is also one of the rare EC cases that may be associated with alcohol use.

Emphysematous Pyelitis With Query Intraparenchymal Involvement

We report the ccase of a 65-year-old woman presenting with urosepsis in the context of a one-week history of progressive right flank pain and a past medical history of type 2 diabetes mellitus. Computed Tomography (CT) demonstrated evidence of emphysematous pyelitis, a rare infection caused by gas-producing bacteria associated with elevated blood glucose. The patient responded well to fluid resuscitation and was discharged home with follow-up arranged for blood sugar management and outpatient lithotripsy addressing obstructive renal calculus.

Air entrapment resembling necrotising fasciitis as a frequent incident following total hip arthroplasty

In combination with pain and elevated inflammatory parameters that are frequently observed following elective total hip arthroplasty (THA), air entrapment on radiographic images could be indicative of necrotising fasciitis. The aim of the present study was to analyse presence/extent of air entrapment following THA, and to correlate radiological with clinical findings. One-hundred patients undergoing short-stem elective THA (ANA NOVA Alpha Proxy-system) were prospectively included. Patients received pre- and postoperative x-rays (day 1 + discharge) of the affected hip, together with a CT-scan of the lower extremity (discharge). C-reactive-protein-(CRP), leukocyte, haemoglobin-, creatinine-, glucose-, sodium-levels – and based on these the LRINEC score– as well as pain-scores (numeral-rating-scale, NRS) at postoperative days 1, 3 and 5 were documented. Air entrapment was visible in 98% of x-rays taken postoperatively and in 93% of CT-scans at discharge. Leukocyte-levels significantly decreased from postoperative day 1 to 5. CRP-levels had a peak at the 3rd postoperative day (p < 0.001). On discharge-x-rays of patients with low body-mass-indexes, air entrapment was significantly more often visible (p = 0.040). Neither implant-related nor laboratory parameters, LRINEC- or NRS-scores significantly correlated with presence/extent of air entrapment (p > 0.05). Considering the high rate of air entrapment following elective THA postoperatively and at discharge, suspicion of an infection with gas-producing bacteria may only be raised in case of persistent inflammatory parameters, deteriorating general condition and signs of local infection.