Overview of Proteus mirabilis pathogenicity and virulence. Insights into the role of metals

Proteus mirabilis is a Gram-negative bacterium with exclusive molecular and biological features. It is a versatile pathogen acclaimed for its distinct urease production, swarming behavior, and rapid multicellular activity. Clinically, P. mirabilis is a frequent pathogen of the human urinary system where it causes urinary tract infections (UTIs) and catheter-associated urinary tract infections (CAUTIs). This review explores the epidemiology, risk factors, clinical manifestations, and treatment of P. mirabilis infections, emphasizing its association with UTIs. The bacterium's genome analysis revealed the presence of resistance genes against commonly used antibiotics, an antibiotic-resistant phenotype that poses a serious clinical challenge. Particularly, the emergence of extended-spectrum β-lactamases (ESBLs) and carbapenemases resistant P. mirabilis strains. On a molecular level, P. mirabilis possesses a wide array of virulence factors including the production of fimbriae, urease, hemolysins, metallophores, and biofilm formation. This review thoroughly tackles a substantial gap in understanding the role of metallophores in shaping the virulence factors of P. mirabilis virulence. Siderophores, iron metal chelating and transporting metallophores, particularly contribute to the complex pathogenic strategies, displaying a potential target for therapeutic intervention.

General Overview of Klebsiella pneumonia: Epidemiology and the Role of Siderophores in Its Pathogenicity

The opportunistic pathogen Klebsiella pneumoniae (K. pneumoniae) can colonize mucosal surfaces and spread from mucosae to other tissues, causing fatal infections. Medical equipment and the healthcare setting can become colonized by Klebsiella species, which are widely distributed in nature and can be found in water, soil, and animals. Moreover, a substantial number of community-acquired illnesses are also caused by this organism worldwide. These infections are characterized by a high rate of morbidity and mortality as well as the capacity to spread metastatically. Hypervirulent Klebsiella strains are thought to be connected to these infections. Four components are critical to this bacterium's pathogenicity-the capsule, lipopolysaccharide, fimbriae, and siderophores. Siderophores are secondary metabolites that allow iron to sequester from the surrounding medium and transport it to the intracellular compartment of the bacteria. A number of variables may lead to K. pneumoniae colonization in a specific area. Risk factors for infection include local healthcare practices, antibiotic use and misuse, infection control procedures, nutrition, gender, and age.

Fecal prevalence of Campylobacter spp. in house dogs in Lebanon: A pilot study

Background and Aim

Campylobacter spp. are Gram-negative bacilli that are widely recognized as a primary cause of bacterial gastroenteritis worldwide. Campylobacteriosis is the disease caused by this pathogen. Recently, greater attention has been given to the prevalence of campylobacteriosis in different animals, including pets. These animals are considered to be significant reservoirs for this zoonosis. In Lebanon, the occurrence of Campylobacter infection is high. Our first-of-its-kind pilot study in Lebanon aimed to estimate the fecal prevalence of Campylobacter species in house dogs.

Materials and Methods

Thirty-five rectal swabs were collected from male and female house dogs of different ages, both with or without diarrhea. Samples obtained from the dogs were subjected to qualitative microbiological culture testing and molecular diagnosis by polymerase chain reaction assays after bacterial DNA extraction.

Results

Fecal prevalence of Campylobacter spp. in house dogs in this study was 17%. There was a relatively higher prevalence among young females and a significant difference between healthy dogs and those suffering from diarrhea.

Conclusion

Campylobacteriosis was found to be prevalent among house dogs in Lebanon, making them potential carriers of Campylobacter species.

Towards new antibiotics classes targeting bacterial metallophores

The increasing bacterial resistance caused by antibiotic overuse has promoted the search for new antimicrobial strategies. Metals uptake via bacterial metallophores are studied to develop new therapeutics against infectious diseases, because metal ions are essential for bacterial growth and virulence. Metal ions assimilation is mainly dependent on metallophores production which are metal chelators synthetized and produced by bacteria to facilitate metals uptake and are vital for bacterial pathogenicity. Here we highlight the perspective for antimicrobial and therapeutic potential of metallophores through several approaches for metallophores application in antimicrobial therapy.

Prevalence and Clinical Significance of Urinary Tract Infection among Neonates Presenting with Unexplained Hyperbilirubinemia in Lebanon: A Retrospective Study

BACKGROUND

Neonatal jaundice is commonly seen in term and preterm newly born babies. It could be either physiologic or secondary to multiple underlying pathologies like urinary tract infection (UTI). Our main objective was to confirm the relationship between neonatal jaundice without apparent cause like hemolysis and the presence of UTI.

MATERIALS AND METHODS

We, retrospectively over a period extended from 2017 to 2020, included 496 babies admitted for elevated indirect hyperbilirubinemia for whom demographic, clinical, laboratory, and therapeutic data were collected through a detailed questionnaire.

RESULTS

Our study included 496 neonates and showed a prevalence of UTI in 8.9% of neonates. The two most common microorganisms in urine culture were Escherichia coli (65.9%) and Klebsiella pneumoniae (25.0%). A multivariate logistic analysis showed that UTI was associated with male neonates (odds ratio [OR] = 2.366, 95% confidence interval [CI]: 1.173 - 4.774; P = 0.016), history of prenatal UTI (OR = 5.378, 95% CI: 2.369 - 12.209; P <0.001), poor feeding (OR = 3.687, 95% CI: 1.570 - 8.661; P = 0.003), and positive urine culture in catheter (OR = 2.704, 95% CI: 1.255 - 5.826; P = 0.011). The mean length of stay was higher in patients with positive UTI (Median = 216 hours) compared to patients with negative UTI (Median = 48 hours) (P <0.001).

CONCLUSION

Neonatal sreening for UTI should be recommended whenever there is unexplaind early or prolonged hyperbilirubinemia with no evidence of alloimmune hemolysis or blood group incompatibility and to prevent the morbidity of urosepsis and congenital kidneys malformations.

Overview of Yersinia pestis Metallophores: Yersiniabactin and Yersinopine

The pathogenic anaerobic bacteria Yersinia pestis (Y. pestis), which is well known as the plague causative agent, has the ability to escape or inhibit innate immune system responses, which can result in host death even before the activation of adaptive responses. Bites from infected fleas in nature transmit Y. pestis between mammalian hosts causing bubonic plague. It was recognized that a host's ability to retain iron is essential in fighting invading pathogens. To proliferate during infection, Y. pestis, like most bacteria, has various iron transporters that enable it to acquire iron from its hosts. The siderophore-dependent iron transport system was found to be crucial for the pathogenesis of this bacterium. Siderophores are low-molecular-weight metabolites with a high affinity for Fe³⁺. These compounds are produced in the surrounding environment to chelate iron. The siderophore secreted by Y. pestis is yersiniabactin (Ybt). Another metallophore produced by this bacterium, yersinopine, is of the opine type and shows similarities with both staphylopine and pseudopaline produced by Staphylococcus aureus and Pseudomonas aeruginosa, respectively. This paper sheds light on the most important aspects of the two Y. pestis metallophores as well as aerobactin a siderophore no longer secreted by this bacterium due to frameshift mutation in its genome.

Prevalence of Campylobacter spp. in broilers in North Lebanon

Background and Aim: Great attention has been given recently to the prevalence of different Campylobacter spp. in poultry since the latter are considered the major contributing reservoir of human campylobacteriosis. In Lebanon, the occurrence of campylobacteriosis in humans is high. The aim of our first-of-its-kind study in the country was to estimate the prevalence of Campylobacter spp. in broilers from a convenient sample of farms in North Lebanon. Materials and Methods: One hundred twenty-five fecal samples were collected from 25 broiler farms, which were selected, examined, and classified according to their biosecurity level and rearing system. All samples were subjected to qualitative microbiological culture testing and polymerase chain reaction (PCR) assays to detect Campylobacter spp. Results: Despite the reported use of antibiotics, cell culture and PCR were positive for 44% and 88%, respectively. This implies that this bacterium is resistant to antibiotics used on the farms. Furthermore, Campylobacter infection rate was higher in open (92%) than in closed (85%) system farms. All farms with poor biosecurity measures, and 82% of farms with good biosecurity measures had Campylobacter infections, and the difference was significant (p < 0.05). Conclusion: Our results show that campylobacteriosis was found prevalent among broilers in North Lebanon, making them potential carriers of Campylobacter spp. Future studies should include antibiotic susceptibility testing to check the susceptibility pattern of isolates.

Prevalence, Laboratory Findings and Clinical Characteristics of Campylobacteriosis Agents among Hospitalized Children with Acute Gastroenteritis in Lebanon

PURPOSE

Campylobacter species are currently the most common cause of bacterial gastroenteritis. In Lebanon, Campylobacter infection occurrence is underdiagnosed owing to the lack of specific culture and rapid test kits, particularly among children. This study aimed to evaluate the prevalence, laboratory findings, and clinical characteristics of Campylobacter infection in hospitalized children with acute gastroenteritis in South Lebanon.

METHODS

We conducted a 6-month retrospective cohort study between January and June 2018, including 291 children aged between 1 month and 12 years, who were admitted to a tertiary healthcare center in South Lebanon. The medical files of the patients were reviewed to retrieve the required clinical information, including clinical and laboratory data.

RESULTS

The prevalence of campylobacteriosis agents in pediatric patients with acute gastroenteritis is 12.02%. Patients infected with Campylobacter had more severe acute gastroenteritis than Campylobacter-negative patients and often presented with high-grade fever, diarrhea episodes more than six times per day, diarrhea lasting for more than five days, and dehydration. Indeed, children with high-grade fever (≥38.5°C) were five times more likely to test positive for Campylobacter than those with low-grade fever. In addition, the results showed a higher Vesikari score for the majority of Campylobacter-positive patients with severe acute gastroenteritis compared to a moderate profile for Campylobacter-negative patients.

CONCLUSION

The present study findings highlight that Campylobacter infection is frequent among children with acute gastroenteritis. Therefore, the detection of Campylobacter should be carried out for the diagnosis of human gastroenteritis in Lebanon, along with the detection of routine enteropathogens.

The Emergence of SARS-CoV-2 Variant(s) and Its Impact on the Prevalence of COVID-19 Cases in the Nabatieh Region, Lebanon

Background: An outbreak of an unknown respiratory illness caused by a novel coronavirus, SARS-CoV-2, emerged in the city of Wuhan in Hubei Province, China, in December 2019 and was referred to as coronavirus disease-2019 (COVID-19). Soon after, it was declared as a global pandemic by the World Health Organization (WHO) in March 2020. SARS-CoV-2 mainly infects the respiratory tract with different outcomes ranging from asymptomatic infection to severe critical illness leading to death. Different SARS-CoV-2 variants are emerging of which three have raised concerns worldwide due to their high transmissibility among populations. Objective: To study the prevalence of COVID-19 in the region of Nabatieh-South Lebanon during the past year and assess the presence of SARS-CoV-2 variants and their effect on the spread of infection during times of lockdown. Methods: In our study, 37,474 nasopharyngeal swab samples were collected and analyzed for the detection of SARS-CoV-2 virus in suspected patients attending a tertiary health care center in South Lebanon during the period between 16 March 2020 and 21 February 2021. Results: The results demonstrated a variation in the prevalence rates ranging from less than 1% during full lockdown of the country to 8.4% upon easing lockdown restrictions and reaching 27.5% after the holidays and 2021 New Year celebrations. Interestingly, a new variant(s) appeared starting January 2021 with a significant positive association between the prevalence of positive tests and the percentage of the variant(s). Conclusions: Our results indicate that the lockdown implemented by the Lebanese officials was an effective intervention to contain COVID-19 spread. Our study also showed that lifting lockdown measures during the holidays, which allowed indoor crowded gatherings to occur, caused a surge in COVID-19 cases and rise in the mortality rates nationwide. More importantly, we confirmed the presence of a highly transmissible SARS-CoV-2 variant(s) circulating in the Lebanese community from at least January 2021 onwards.

Seroprevalence of Brucella abortus in cattle in Southern Lebanon using different diagnostic tests

Background and Aim

Brucellosis is endemic zoonotic and highly contagious bacterial disease. Recently, several brucellosis cases were reported in Lebanon, causing significant economic losses; however, no study was done so far on farms located in the southern part of the country. Thus, the aim of our study was to estimate the prevalence of Brucella abortus in South Lebanon using three different serological tests in the diagnosis of brucellosis in cattle.

Materials and Methods

Seventeen farms from 14 locations in Southern Lebanon were selected. Two hundred and three bovine blood samples of different ages, and 121 milk samples collected from older than 2 years cattle were tested using different serological tests: Rose Bengal test (RBT), milk ring test (MRT), indirect enzyme-linked immunosorbent assay (I-ELISA), and confirmed with competitive ELISA (C-ELISA).

Results

Results revealed that approximately 15.3% (confidence interval [CI] 95 10.3-20.2%) and 15.7% (CI 95 9.2-22.2%) of samples were positive using RBT and MRT, respectively. This percentage was significantly higher when using I-ELISA (18.3%) (CI 95 12.9-23.5%) and C-ELISA (18.7%) (CI 95 9.8-27.5%). Among used diagnostic tests, our results showed that ELISA was more accurate for the detection of brucellosis, especially since it detects the late stages of the infection, which is characterized by the presence of immunoglobulin G. The seroprevalence of brucellosis was higher among females. All positive tests were of cattle Holstein breed older than 2 years. Tyre and Jezzine cities had a higher significance in bovine brucellosis than Saida. A positive correlation between human and cattle brucellosis was found.

Conclusion

Our results showed that bovine brucellosis is prevalent in southern Lebanon. Lack of research, in addition to little feedback of occurring illness or symptoms, creates a gap in helping to control the spread of the disease.

Spectrum of MEFV Variants and Genotypes among Clinically Diagnosed FMF Patients from Southern Lebanon

Background: Familial Mediterranean Fever (FMF) is an autosomal recessive auto-inflammatory disease characterized by pathogenic variants in the MEFV gene, with allele frequencies greatly varying between countries, populations and ethnic groups. Materials and methods: In order to analyze the spectrum of MEFV variants and genotypes among clinically diagnosed FMF patients from South Lebanon, data were collected from 332 participants and 23 MEFV variants were screened using a Real-Time PCR Kit. Results: The mean age at symptom onset was 17.31 ± 13.82 years. The most prevalent symptoms were abdominal pain, fever and myalgia. MEFV molecular analysis showed that 111 patients (63.79%) were heterozygous, 16 (9.20%) were homozygous, and 47 (27.01%) carried two variants or more. E148Q was the most encountered variant among heterozygous subjects. E148Q/M694V was the most frequent in the compound heterozygous/complex genotype group, while M694I was the most common among homozygous patients. Regarding allele frequencies, M694V was the most common variant (20.7%), followed by E148Q (17.1%), V726A (15.7%) and M694I (13.2%). Conclusion: The high percentage of heterozygous patients clinically diagnosed as FMF highlights the pseudo-dominant transmission of the disease in Lebanon and emphasizes the importance of molecular testing for a more accurate diagnosis and better management and treatment of FMF.

Antimicrobial Susceptibilities and Laboratory Profiles of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis Isolates as Agents of Urinary Tract Infection in Lebanon: Paving the Way for Better Diagnostics

Background: Urinary tract infections (UTIs) are major healthcare problems that are usually treated empirically. However, antimicrobial resistance has been increasing across many settings. This study aims to elucidate the antibiotic resistance profiles of three common uropathogens, Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), and Proteus mirabilis (P. mirabilis) and compare between extended spectrum beta-lactamase (ESBL) and non-ESBL strains among Lebanese patients. Methods: This retrospective study was conducted at multiple tertiary healthcare centers in South Lebanon, between January and September 2017, including 551 patients of all age groups. Demographic, clinical, and laboratory data of patients were collected and analyzed statistically. Results: The prevalence of UTI in Lebanon was highest in adults between 19 and 64 years (44%). E. coli was the predominant uropathogenic organism (67.1%) followed by K. pneumoniae (10%) and P. mirabilis (3.7%). ESBL represented 32.9% of the UTI agents. The three common uropathogens studied were found to be most susceptible to imipenem (100%) and meropenem (100%). Interestingly, 115 (25.1%) out of the 458 E. coli isolates were resistant to more than eight antibiotics while 107 (23.4%) were susceptible to all antibiotics studied. Conclusions: Our study underlined the importance of adequate antimicrobial prescription for UTIs in Lebanon to avoid multidrug resistance.

Prevalence, risk factors, and clinical characteristics of rotavirus and adenovirus among Lebanese hospitalized children with acute gastroenteritis

BACKGROUND

Acute gastroenteritis is a very common infectious disease facing all age groups worldwide, especially the pediatric population. Viruses, bacteria, and parasites are all possible causes of infectious gastroenteritis; however, viruses have become more frequently identified with the advances in the ability to diagnose viral infections, particularly rotavirus and adenovirus. We aimed in our study to compare between the prevalence, risk factors, and clinical characteristics of rotavirus and adenovirus among children with viral gastroenteritis in Lebanon.

MATERIALS AND METHODS

A 12-months retrospective study was performed between January 1st and December 31st, 2018 including 308 children aged 1 month to 12 years, who were admitted to three tertiary healthcare centers in South Lebanon. Medical data were retrieved from patients' files, including clinical and laboratory information.

RESULTS

Rotavirus was found in stool of 204 patients (66.23 %), followed by adenovirus in 78 cases (25.32 %), and mixed group (rotavirus and adenovirus) in 26 cases (8.44%). The highest prevalence of rotavirus in our present study was seen among children between 12 and 23 months old, whereas patients infected with adenovirus were mainly aged between 24-35 months or 4-11 months. Majority of patients in the adenovirus and mixed groups had high-grade fever compared to the rotavirus group. Laboratory findings presented significantly higher average of white blood cells (WBCs), absolute neutrophil count (ANC), and C-reactive protein (CRP) in the mixed group compared to the two other groups. Monthly distribution of rotavirus and adenovirus infection revealed a biennial pattern of rotavirus incidence during January and July-August while frequency of adenovirus infection was highest during July-August.

CONCLUSION

Due to the high prevalence of viral diarrhea among the pediatric age group in our region, particularly rotavirus and adenovirus, along with the associated non-specific signs and symptoms, we highly recommend that medical laboratories be equipped for virus detection. Also, vaccination against rotavirus should be considered as a prevention strategy.

Prevalence, risk factors and seasonal variations of different Enteropathogens in Lebanese hospitalized children with acute gastroenteritis

BACKGROUND

Acute gastroenteritis (AGE) is a major cause of pediatric morbidity and mortality around the world. It remains a frequent reason for infection-related admissions to emergency units among all age groups. Following the Syrian refugee crisis and insufficient clean water in our region, we sought to assess the etiological and epidemiological factors pertaining to AGE in South Lebanon.

METHODS

In this multi-center cross sectional clinical study, we analyzed the demographic, clinical and laboratory data of 619 Lebanese children from the age of 1 month to 5 years old who were admitted with AGE to pediatrics departments of three tertiary care centers in South Lebanon.

RESULTS

Our results revealed that males had a higher incidence of AGE (57.3%) than females. Enteropathogens were identified in 332/619 (53.6%) patients. Single pathogens were found in 294/619 (47.5%) patients, distributed as follows: Entamoeba histolytica in 172/619 (27.8%) patients, rotavirus in 84/619 (13.6%), and adenovirus in 38/619 (6.1%). Mixed co-pathogens were identified in 38/619 (6.1%) patients. Analyzing the clinical manifestations indicated that E. histolytica caused the most severe AGE. In addition, children who received rotavirus vaccine were significantly less prone to rotavirus infection.

CONCLUSIONS

Our findings alluded to the high prevalence of E. histolytica and other unidentified enteropathogens as major potential causes of pediatric AGE in hospitalized Lebanese children. This should drive us to widen our diagnostic panel by adopting new diagnostic techniques other than the routinely used ones (particularly specific for the pathogenic amoeba E. histolytica and for the unidentified enteropathogens), and to improve health services in this unfortunate area of the world where insanitary water supplies and lack of personal hygiene represent a major problem.

Prevalence, antimicrobial resistance and risk factors for campylobacteriosis in Lebanon

INTRODUCTION

The rapid increase in Campylobacter strains resistant to antibiotics represents a major problem for public health. In Lebanon, campylobacteriosis is underdiagnosed since bacteria detection in stool samples is not performed routinely. This study aims to evaluate the prevalence, sources and routes of transmission, risk factors and antimicrobial susceptibility patterns of Campylobacter spp. in Lebanon.

METHODOLOGY

Stool samples collected from 1000 Lebanese patients with diarrhea, and 150 meat samples taken from supermarkets and slaughterhouses were subjected to Campylobacter detection. Colonies were identified by Gram staining, oxidase and catalase activities. They were then differentiated at the species level by hippurate test and PCR. Susceptibility of Campylobacter spp. to antibiotics was studied by the disc diffusion standard method.

RESULTS

Campylobacter spp. were detected in 21.5% of stool samples; the main isolated species being C. jejuni (83.2%) and C. coli (13.9%). The highest Campylobacter infection rates were detected among children (41.8%) and during summer (31.6%). Consumption of contaminated meat and salads, and contact with animals represented the major risk factors for campylobacteriosis, with poultry carcasses and bovine cuts identified as the main bacteria reservoirs. Neither demographic determinants nor season had a major effect on the prevalence of campylobacteriosis. Erythromycin was the most active agent against Campylobacter spp. A multi-resistance rate was observed in 35.9% of isolates.

CONCLUSIONS

Campylobacteriosis is a major public health concern in Lebanon. Bacteria detection in stool culture should be performed routinely to allow an early diagnosis and a better monitoring of the disease and its burden.

Prevalence of anemia among Lebanese hospitalized children: Risk and protective factors

BACKGROUND

Anemia is a global health problem associated with short- and long-term consequences especially in children. The incidence of anemia along with the factors associated with its increased or decreased risk is not yet well studied in Lebanon. Our study aims at determining the demographics of this health burden and identifying some of the important factors linked to it among the pediatric population.

METHODS

A 4-months cross-sectional study was performed between August and November 2017 including 295 children aged 1 month to 12 years, who were hospitalized in a tertiary care hospital located in South Lebanon. We analyzed the different demographic data, age, gender, breast feeding duration, solid food introduction, iron supplementation and disease of diagnosis in association with multiple hematological parameters.

RESULTS

The prevalence of both mild and moderate anemia was 71.8 and 25.4%, with only 2 cases of severe anemia encountered among children aged 6 months or above. Results showed that the risk of anemia increases by around 3.4 folds among malnourished children than in well-nourished children. This risk also decreased by almost 42% in children receiving iron supplement.

CONCLUSION

In consideration to the fact that anemia is a prevalent disease in the Lebanese childhood population, especially in infancy, simple preventive measures such as proper nutritional habits and supplementation of iron rich food to children are highly recommended and should be respected by public health providers.

Surveillance Study of Acute Gastroenteritis Etiologies in Hospitalized Children in South Lebanon (SAGE study)

PURPOSE

Acute gastroenteritis (AGE) is a major cause of morbidity and remains a major cause of hospitalization. Following the Syrian refugee crisis and insufficient clean water in the region, this study reviews the etiological and epidemiological data in Lebanon.

METHODS

We prospectively analyzed demographic, clinical and routine laboratory data of 198 children from the age of 1 month to 10 years old who were admitted with the diagnosis of AGE to a private tertiary care hospital located in the district of Nabatieh in south Lebanon.

RESULTS

Males had a higher incidence of AGE (57.1%). Pathogens were detected in 57.6% (n=114) of admitted patients, among them single pathogens were found in 51.0% (n=101) of cases that consisted of: Entamoeba histolytica 26.3% (n=52), rotavirus 18.7% (n=37), adenovirus 6.1% (n=12) and mixed co-pathogens found in 6.6% (n=13). Breast-fed children were significantly less prone to rotavirus (p=0.041). Moreover, children who had received the rotavirus vaccine were significantly less prone to rotavirus (p=0.032).

CONCLUSION

Our findings highlight the high prevalence of E. histolytica infection as the major cause of pediatric gastroenteritis in hospitalized children, during the summer period likely reflecting the insanitary water supplies and lack of hygiene. Moreover the 42.4% of unidentified causative pathogens should prompt us to widen our diagnostic laboratory arsenal by adopting new diagnostic technologies.

Pseudomonas aeruginosa zinc uptake in chelating environment is primarily mediated by the metallophore pseudopaline

Metal uptake is vital for all living organisms. In metal scarce conditions a common bacterial strategy consists in the biosynthesis of metallophores, their export in the extracellular medium and the recovery of a metal-metallophore complex through dedicated membrane transporters. Staphylopine is a recently described metallophore distantly related to plant nicotianamine that contributes to the broad-spectrum metal uptake capabilities of Staphylococcus aureus. Here we characterize a four-gene operon (PA4837-PA4834) in Pseudomonas aeruginosa involved in the biosynthesis and trafficking of a staphylopine-like metallophore named pseudopaline. Pseudopaline differs from staphylopine with regard to the stereochemistry of its histidine moiety associated with an alpha ketoglutarate moiety instead of pyruvate. In vivo, the pseudopaline operon is regulated by zinc through the Zur repressor. The pseudopaline system is involved in nickel uptake in poor media, and, most importantly, in zinc uptake in metal scarce conditions mimicking a chelating environment, thus reconciling the regulation of the cnt operon by zinc with its function as the main zinc importer under these metal scarce conditions.

Biosynthesis of a broad-spectrum nicotianamine-like metallophore in Staphylococcus aureus

Metal acquisition is a vital microbial process in metal-scarce environments, such as inside a host. Using metabolomic exploration, targeted mutagenesis, and biochemical analysis, we discovered an operon in Staphylococcus aureus that encodes the different functions required for the biosynthesis and trafficking of a broad-spectrum metallophore related to plant nicotianamine (here called staphylopine). The biosynthesis of staphylopine reveals the association of three enzyme activities: a histidine racemase, an enzyme distantly related to nicotianamine synthase, and a staphylopine dehydrogenase belonging to the DUF2338 family. Staphylopine is involved in nickel, cobalt, zinc, copper, and iron acquisition, depending on the growth conditions. This biosynthetic pathway is conserved across other pathogens, thus underscoring the importance of this metal acquisition strategy in infection.