Citrobacter Infections Research Articles

P-872. Clinical and Microbiological Trends in Citrobacter Bacteremia: A Study from South India

Abstract Background Citrobacter spp are anaerobic Gram-negative bacilli, accounting for approximately 0.8% of all Gram-negative infections. This study aims to elucidate the clinical manifestations and drug susceptibility in Citrobacter infections. Clinical features of patients with Citrobacter bacteremia and comparison between Citrobacter koseri and other Citrobacter spp Methods We conducted a retrospective analysis of Citrobacter spp. bacteremia cases from 2016 to 2022. We assessed clinical profile, species, antimicrobial susceptibility and 28-day outcome. Blood cultures were processed using the BacT/ALERT, Vitek 2 system was employed for bacterial identification and antimicrobial susceptibility testing and reported as per CLSI criteria. Isolates with intermediate susceptibility were classified as non-susceptible. Comparison of antibiotic susceptibility between C Koseri and other Citrobacter spp Results Over the 7 year study period, 25 cases of Citrobacter bacteremia were identified, 60% were males. The median age was 52.5 years (IQR: 46 – 75), with 2 pediatric cases. The annual incidence of Citrobacter bacteremia displayed an upward trend, from 12% in 2016 to 24% in 2022. C. koseri emerged as the predominant species (72%), followed by C. freundii (24%) and C. farmeri (4%). The majority of patients (72%) had diabetes, 16% had chronic liver disease, 12% had malignancy. Risk factors for Citrobacter bacteremia included the presence of an indwelling bladder catheter (76%) and a central venous catheter (44%). Urinary tract was the most frequent source (56%), followed by abdominal (20%) and soft tissue (8%); a newborn had meningitis with brain abscess. The mean for Pitt’s bacteremia score was 1.52±2.6. The mean Charlson’s co-morbidity index was 2.76±2.3. Clinical features for the entire cohort and comparative results between C Koseri and other Citrobacter spp (grouped as non-koseri) is depicted in figure 1. Ciprofloxacin susceptibility was higher among C koseri (94%) as compared to other spp (71%). Antibiotic susceptibility for ceftriaxone was almost similar between the 2 groups. Susceptibility rates for other antibiotics and comparison between C Koseri and other spp are shown in figure 2. All isolates were susceptible to ertapenem, imipenem and amikacin. The overall 28-day mortality rate was 12%. Conclusion We found C. koseri more commonly, urinary source as the most common source and device presence as a significant risk factor. Antibiotic susceptibility was better for C. koseri compared to others. Disclosures All Authors: No reported disclosures

Citrobacter Causing Septic Arthritis: A Case Report

Abstract The genus Citrobacter commonly found in water and soil as well as the intestinal and urinary tracts of animals and humans. Although Citrobacter infections are infrequently diagnosed in environmental contexts, the rising incidence of nosocomial manifestations underscores the importance of considering this organism in the differential diagnosis of hospital-acquired infections. We present a case of patient with septic arthritis of the shoulder who had been originally admitted for the management of acute-on-chronic congestive heart failure exacerbation and severe sepsis. On hospital day 1, joint aspiration cultures and Gram stain confirmed the presence of Citrobacter koseri, a pathogen not commonly associated with septic arthritis, and ceftriaxone was administered to target it. On hospital day 7, antibiotic was transitioned to levofloxacin, every other day for 4 weeks. The patient was discharged to an acute rehabilitation facility after a 14-day hospital stay. This case stresses the importance of maintaining a broad differential diagnosis for any patients who present with fever and joint inflammation or swelling, especially in a postoperative setting.

Pediatric Citrobacter Urinary Tract Infections: A Case Report Highlighting Emerging Trends

Urinary tract infections (UTIs) caused by Citrobacter species in pediatric patients present a unique and infrequently reported scenario in clinical practice. This case report delves into the clinical presentation, diagnostic challenges, treatment modalities, and overall management of a pediatric UTI caused by Citrobacter. Through a literature review, it becomes evident that while Citrobacter infections are more commonly observed in adults, especially the elderly population, recent studies signal a rising trend in pediatric cases globally. Noteworthy findings from published cases underscore the diverse clinical manifestations and associated challenges. We present the case of a 1-month-old male who presented with feeding difficulties and irritability, subsequently diagnosed with a UTI caused by Citrobacter koseri. Despite lacking typical risk factors or symptoms associated with Citrobacter UTIs, the patient demonstrated a favorable response to antibiotic therapy. This case stresses the evolving nature of Citrobacter infections in the pediatric population and emphasizes the importance of vigilance in recognition and management. Further research is warranted to better understand this emerging trend and its implications for pediatric care.

A brief insight into Citrobacter species -a growing threat to public health.

Citrobacter spp. are Gram-negative, non-spore forming, rod-shaped, facultative anaerobic bacteria from the Enterobacteriaceae family often found in soil, sewage, sludge, water, food, and the intestinal tracts of animals and humans. Several members of Citrobacter spp. especially C. freundii, C. koseri, C. braakii are frequently detected in newborn illnesses, urinary tract infections, and patients with severe underlying conditions, including hypertension, diabetes, cancer, and respiratory infections, or those who are immunocompromised. Strains of Citrobacter spp. can spread vertically or horizontally from carriers or other hospital sources and thus cause nosocomial infections in hospital settings. A total of 19 Citrobacter genomospecies have been recognized based on genomics. It has been noted that the Citrobacter genus acquired antimicrobial resistance and virulence, including invasion, colonization, biofilm formation, and toxin production. The recent emergence and spread of antimicrobial resistance to β-lactams, carbapenems, fluoroquinolones, aminoglycosides, and colistin in Citrobacter spp. through chromosomal and plasmid-mediated resistance limits the empiric treatment options. Therefore, combination therapy involving costly and potentially hazardous antibiotics poses significant challenges in treating Citrobacter infections. Here we summarized the nomenclature of Citrobacter spp., clinical manifestations, epidemiology, pathogenesis, antibiotic resistance mechanisms, and treatments from various clinical samples. This review will expand our knowledge of the genomics and epidemiology of Citrobacter spp., enabling improved control of infections and the spread of these organisms.

Citrobacter freundii-associated osteomyelitis and thromboembolic events following Moderna COVID-19 vaccination: a rare case report from Nepal.

Vaccination against coronavirus disease 2019 (COVID-19) is essential for controlling the ongoing cases of this disease. Citrobacter infections of the bones and joints are extremely uncommon. Thromboembolism and deep vein thrombosis (DVT) are very rare complications. The authors present a rare case of osteomyelitis, septic arthritis, deep venous thrombosis, and pulmonary embolism in a 15-year-old previously healthy boy occurring shortly after receiving the second dose of the Moderna COVID-19 vaccine. He experienced pain, swelling in the right leg, shortness of breath, and fever, followed by chest pain and leg edema. Treatment included anticoagulation, ketorolac for pain management, antipyretics, and intravenous antibiotics (Tazobactam/Piperacillin, Linezolid, Clindamycin) for osteomyelitis. The risk of COVID-19 vaccine-related thrombotic events is minimal. Thrombotic events reported among mRNA is very rare. Citrobacter freundii bone and joint infections are very rare, accounting for a small percentage of cases. Some documented cases include cefotaxime-resistant strains causing necrotizing fascitis and osteomyelitis, including postarthroplasty infections. Due to the diverse range of susceptibility patterns and the widespread occurrence of drug resistance, personalized treatment based on culture and sensitivity testing is recommended. However, in rare cases, severe complications like DVT and joint infections associated with Citrobacter infection may occur and should be reported to the vaccine adverse events reporting system. Administering the COVID-19 vaccine to enhance natural antibodies is crucial, despite the low risk of infection, thromboembolism, and DVT. Healthcare providers should stay vigilant about adverse effects postvaccination and promptly report those cases.

In vitro resistance pattern of Citrobacter infections: A retrospective study

Background: Citrobacter infections are associated with a high mortality rate of about 33-48% if infected patients develop bacteremia. This is partly due to high prevalence of intrinsic resistance, extended spectrum beta lactamases and inducible chromosomal Amp C beta lactamases in Citrobacter spp. thus limiting the therapeutic options. We undertook this study to throw light on the current scenario of infection with this organism. Materials and methods: This retrospective study was conducted over a period of 1 year in Microbiology laboratory of a tertiary care teaching hospital in Eastern part of India. From various samples, 146 clinically significant Citrobacter spp. identified by standard biochemical tests and susceptibility testing performed by Kirby Bauer’s disc diffusion method were included in this study. Results: Majority of patients age ranged of 41-50 year. The highest number (70/146, 47.9%) of Citrobacter spp. was isolated from pus and wound swabs followed by urine (46/146, 31.5%) and out of these, 51.4% strains were of Citrobacter koseri whereas 48.6% were of Citrobacter fruendii. Of Citrobacter isolates 36.6% were ESBL producers. They showed 54.1%, 37.9%, 47.1%, 39.8% and 58.5% resistance to imipenem, netilmycin, piperacillin tazobactam, minocycline and levofloxacin respectively. We also found 9.6% and 28.4% strains of Citrobacter spp. being resistant to colistin and tigecycline respectively. Conclusion: Citrobacter spp. showed high degree of resistance to carbapenem and there were colistin resistance strains as well. This study reiterates the emerging resistance in these supposedly low virulence microbes which may pose future challenge in infection control activities.

A Rare Case of Pneumonia and Haemoptysis Caused by Citrobactor Freundii in a Young Immunocompetent Male

Citrobacter infections are often nosocomially acquired, seen in patients with significant underlying diseasesand isolates are commonly drug-resistant.A rare clinical syndrome of haemoptysis with underlyingpneumonia caused by Citrobactor freundii in a immunocompetent young male is presented.

Curbing gastrointestinal infections by defensin fragment modifications without harming commensal microbiota

The occurrence and spread of multidrug-resistant pathogens, especially bacteria from the ESKAPE panel, increases the risk to succumb to untreatable infections. We developed a novel antimicrobial peptide, Pam-3, with antibacterial and antibiofilm properties to counter this threat. The peptide is based on an eight-amino acid carboxyl-terminal fragment of human β-defensin 1. Pam-3 exhibited prominent antimicrobial activity against multidrug-resistant ESKAPE pathogens and additionally eradicated already established biofilms in vitro, primarily by disrupting membrane integrity of its target cell. Importantly, prolonged exposure did not result in drug-resistance to Pam-3. In mouse models, Pam-3 selectively reduced acute intestinal Salmonella and established Citrobacter infections, without compromising the core microbiota, hence displaying an added benefit to traditional broad-spectrum antibiotics. In conclusion, our data support the development of defensin-derived antimicrobial agents as a novel approach to fight multidrug-resistant bacteria, where Pam-3 appears as a particularly promising microbiota-preserving candidate.

Isolation, characterization, and efficacy of bacteriophages isolated against Citrobacter spp. an in vivo approach in a zebrafish model (Danio rerio)

Citrobacter infections are becoming an increasingly significant health problem in aquaculture in South-Eastern countries. The objective of this study was to isolate and evaluate the potential of lytic bacteriophages against Citrobacter infections. TEM analysis revealed that the isolated phages Citrophage MRM19 and Citrophage MRM57 were identified to be Siphovirus and Podovirus family of the order Caudovirales. The phage life-cycle studies showed that Citrophage MRM19 had an adsorption time of 18 ± 1 min and a latency period of 25 ± 3 min with burst size of 110 ± 20 phages/infected cell and Citrophage MRM57 had an adsorption time of 15 ± 1 min and a latency period of 25 ± 2 min with burst size of 50 ± 5 phages/infected cell. In vitro studies indicated that the bacterial load was reduced by 5 and 7 log units within 12 h by Citrophage MRM19 and Citrophage MRM57. The in vivo efficacy of the phages was studied using zebrafish (Danio rerio) as a model organism in low-scale tanks. The study unveiled that the use of phages increased the survival up to 17%, 23%, and 26% in the case of Citrophage MRM19, Citrophage MRM57, and phage cocktail treatment, respectively. Our study indicated that bacteriophages are suitable biocontrol agents against Citrobacter spp. especially in aquaculture industry.

Cystic echinococcosis: An attraction for fungal and bacterial pulmonary infections

Abstract Lung hydatidosis can remain latent for a long time, and symptoms may occur when the cysts grow to a certain size or when symptoms arise secondary to complications such as rupture or superinfection with bacterial organisms or fungi. A variety of signs denoting different appearances of complicated and/or uncomplicated pulmonary hydatid cysts have been described on chest radiographs and computed tomography scans. Aspergillosis is one of the most common fungal infections associated with pre-existing pulmonary cavities. The coexistence of aspergillosis and hydatid cyst is rare. Citrobacter infections usually occur in patients with underlying co-morbidities or immunosuppression. We presented a case of pulmonary echinococcosis with multiple bilateral cysts in which several consecutive episodes of cysts rupture and concomitant Aspergillus and Citrobacter pulmonary infections have been documented.

Clinical Pharmacology of Ciprofloxacin in Neonates: Effects and Pharmacokinetics

Ciprofloxacin is the most commonly used fluoroquinolone. Ciprofloxacin is prescribed for 1 in 44 Americans. Ciprofloxacin is a broad-spectrum bactericidal antibiotic, effective against both gram-positive and gram-negative bacteria, being especially active against the Enterobacteriacae, including many microorganisms resistant to penicillins, cephalosporins and aminoglycosides, and also is effective against Haemophilus influenzae, penicillinase-producing Neisseria gonorrhea, Campylobacter and Pseudomonas aeruginosa. Streptococci and pneumococci are weakly inhibited and there is a high incidence of staphylococcal resistance to ciprofloxacin. In neonates, the dose of ciprofloxacin is 10 mg/kg intravenously over 30-60 min infusion, and 20 mg/kg is used to treat Pseudomonas aeruginosa infection. Ciprofloxacin treatment is effective in life-threatening multi-drug resistant Pseudomonas aeruginosa. Ciprofloxacin may be administered by mouth and has a bioavailability of 70% and is mainly recovered unchanged in the urine. Ciprofloxacin is safe and well tolerated in infants. In neonates, the half-life of ciprofloxacin is 3-4 hours. For meningococcal prophylaxis, give a single dose of 30 mg/kg (up to a maximum of 125 mg) orally. Ciprofloxacin is active against Citrobacter kosery that produces brain abscesses. The mortality rate for meningitis due to Citrobacter kosery is approximately 30%. Third-generation cephalosporins and aminoglycosides failed to prevent the high rates of morbidity and mortality caused by Citrobacter infections. Ciprofloxacin is the antibiotic treatment option for systemic infection or meningitis caused by Citrobacter kosery. Ciprofloxacin has been used to treat neonatal pneumonia, meningitis, and septicemia and was effective in all cases. The aim of this study is to review the clinical pharmacology of ciprofloxacin in neonates.

Etiologies of Urinary Tract Infections in Children Considering Differences in Gender and Type of Infection

Introduction: Urinary tract infection is a common health problem in children. Gram negative entericbacteria, mainly E –coli, are responsible uropathogens. We aimed to define the main etiologies of urinary tract infection in children considering gender and type of infection (febrile versus afebrile).Materials and Methods: We assessed the infections etiology of 648 episodes. Type of infection and etiology were compared between genders. Also, for every uropathogen, a comparison was done between febrile and afebrile infections. Chi square was used for data analysis and P values ≤0.05 were considered as a significant difference.Results: The majority of the infections by Proteus and Enterococcus species were febrile, in contrast to Citrobacter infections which were mostly afebrile. E-coli infections were significantly more prevalent in girls (P=0.0001). Proteus and Kelebsiella infections were more common in boys (P=0.115 and 0.154 respectively), whereas all Enterobacter infections were seen in girls (P=0.129). A comparison was done between females and males based on the type of infection. Although febrile infections were more frequent in boys, the difference was not statistically significant (P=0.059).Conclusions: E-coli, Kelebsiella, Enterobacter and Citrobacter species (90.5%) were the main uropathogens. Infections caused by E-coli were significantly more prevalent in girls. Proteus and Kelebsiella infections were more common in boys, whereas Enterobacter species were more prevalent in girls. The majority of Proteus and Enterococcus infections (>2/3) presented as pyelonephritis, while the frequency of febrile and afebrile infections was similar for E-coli, Kelebsiella, Enterobacter and Staphylococcus species.Keywords: UTIs; Etiology; Gender; Pyelonephritis; Cystitis.

Characterization and genome sequencing of a Citrobacter freundii phage CfP1 harboring a lysin active against multidrug-resistant isolates.

Citrobacter spp., although frequently ignored, is emerging as an important nosocomial bacterium able to cause various superficial and systemic life-threatening infections. Considered to be hard-to-treat bacterium due to its pattern of high antibiotic resistance, it is important to develop effective measures for early and efficient therapy. In this study, the first myovirus (vB_CfrM_CfP1) lytic for Citrobacter freundii was microbiologically and genomically characterized. Its morphology, activity spectrum, burst size, and biophysical stability spectrum were determined. CfP1 specifically infects C. freundii, has broad host range (>85%; 21 strains tested), a burst size of 45PFU/cell, and is very stable under different temperatures (-20 to 50°C) and pH (3 to 11) values. CfP1 demonstrated to be highly virulent against multidrug-resistant clinical isolates up to 12 antibiotics, including penicillins, cephalosporins, carbapenems, and fluroquinoles. Genomically, CfP1 has a dsDNA molecule with 180,219bp with average GC content of 43.1% and codes for 273 CDSs. The genome architecture is organized into function-specific gene clusters typical for tailed phages, sharing 46 to 94% nucleotide identity to other Citrobacter phages. The lysin gene encoding a predicted D-Ala-D-Ala carboxypeptidase was also cloned and expressed in Escherichia coli and its activity evaluated in terms of pH, ionic strength, and temperature. The lysine optimum activity was reached at 20mM HEPES, pH 7 at 37°C, and was able to significantly reduce all C. freundii (>2 logs) as well as Citrobacter koseri (>4 logs) strains tested. Interestingly, the antimicrobial activity of this enzyme was performed without the need of pretreatment with outer membrane-destabilizing agents. These results indicate that CfP1 lysin is a good candidate to control problematic Citrobacter infections, for which current antibiotics are no longer effective.

Periungual Abscess Caused by Citrobacter braakii in a Patient with Chronic Paronychia.

Dear Editor: Citrobacter species, aerobic, gram-negative bacilli in the Enterobacteriaceae family, are normally present in the environment and do not usually cause disease in immunocompetent hosts1. Chronic paronychia is an inflammatory reaction of the nail fold caused by exposure irritants or allergens that can lead to structural changes and increased susceptibility to infection. A 68-year-old woman presented with a 5-day-old, painful grayish abscess (2.0×1.5 cm) on the dorsum of the right thumb (Fig. 1A). Medical history indicated that the patient had contact with a desiccator containing calcium chloride two days before skin eruption. The patient had no current medical issues or surgical history regarding the abscess, and was employed as a housemaid with frequent exposure to water and detergents. She had a 20-year history of chronic paronychia characterized by erythema and mild swelling aggravated by repeated detergent exposure. Topical antibiotics and detergent avoidance temporarily resolved symptoms. A local clinic prescribed 300 mg of roxithromycin daily, which had not resolved the lesion. The patient's lesion was incised and drained, and oral amoxicillin and pivoxyl sulbactam (250 mg each, 3 times daily for 7 days) were prescribed. Culture of lesion identified Citrobacter braakii. By day 7, the abscess had cleared, leaving mild skin excoriation, trachyonychia and Beau's line, which ultimately resolved (Fig. 1B). Fig. 1 (A) A painful grayish 0.8×0.6 inch sized (2.0×1.5 cm) abscess on her right thumb in a 68-year-old women. (B) One week after incision and drainage with antibiotics treatment, the abscess cleared only leaving mild skin excoriation, trachionychia ... Chronic paronychia is an inflammation of the nail fold caused by factors including repetitive trauma and chemical exposure. As a result, the cuticle separates from the nail plate, forming a cleft between the nail fold and plate that predisposes the area to infection2. Upon presentation at our clinic, the patient had a history of chronic paronychia aggravated by detergent exposure. A noticeable cleft was observed in the area of the lesion (Fig. 1B), and we believe that exposure of this cleft to bacteria in a desiccator may have resulted in infection. Citrobacter species are uncommon cutaneous pathogens. Samonis et al.3 reported 5 cases of skin/soft tissue infection among 78 inpatients with confirmed Citrobacter isolates in a study at a Greek hospital. Single cases of folliculitis and skin ulcers caused by Citrobacter species in immunocompetent hosts4 have been reported, but there were no reports of Citrobacter infections manifesting as periungual abscesses. Antibiotic susceptibility differs among Citrobacter subtypes3 and treatment has been based on individual antimicrobial profiles. One study of 22 cases of C. freundii showed 100% resistance to erythromycin, ampicillin, and methicillin5. As was demonstrated in our case study, macrolides including erythromycin and roxithyromycin (often indicated for gram positive/negative cocci infections) were ineffective treatments for C. braakii, a gram-negative bacillus. While oral amoxicillin and pivoxyl sulbactam were prescribed after incision and drainage (I&D) in our study, the Citrobacter isolate was resistant to amoxicillin. Therefore, the I&D procedure was primarily responsible for patient improvement. To our knowledge, this is the first reported case of C. braakii-induced periungual abscess in a patient with chronic paronychia. Additional data on Citrobacter infections are needed to improve comprehension of risk factors, etiology, clinical features, and management of these infections.

Osteomyelitis Due to Citrobacter koseri Infection in a Diabetic Patient

Citrobacter infections are reported in neonates and immunocompromised patients most commonly. Citrobacter koseri (diversus) is an important cause of neonatal meningitis and brain abscess formation. But osteomyelitis is a rare condition and very few cases were reported. We described a 68-years-old man with diabetes mellitus who had 1st metatarsal osteomyelitis due to Citrobacter koseri . Intravenous treatment with piperacillin-tazobactame was administered for 3 weeks and the wound was recovered completely. Citrobacter koseri can be a cause of osteomyelitis in patients with underlying predisposing factors and bone cultures should be evaluated to detect probable pathogens and determine proper antimicrobial therapy. doi:10.4021/jem36e

Citrobacter infections in a general hospital: characteristics and outcomes

In this investigation, we sought to investigate the characteristics of Citrobacter spp. infections. A retrospective cohort study in a 700-bed, tertiary care, university hospital was carried out during the period from June 1994 to January 2006. Seventy-eight patients (70 adults) with Citrobacter spp. isolates were identified. C. freundii was more common (71.8%), followed by C. koseri (23.1%) and C. braakii (3.8%). The most common associated clinical syndromes were urinary tract infections (52.6% of cases, including eight cases of asymptomatic bacteriuria), as well as intra-abdominal (14.1%), surgical site (7.7%), skin and soft tissue (6.4%), and respiratory tract infections (6.4%). In 29.5% of patients, Citrobacter spp. isolates were associated to polymicrobial infections, principally at sites other than the urinary tract. Antibiograms of 38 consecutive Citrobacter spp. isolates (29 C. freundii) were available. Most active agents were colistin (100%), fosfomycin (100%), imipenem (97.4%), gentamicin (89.5%), nitrofurantoin (89.5%), ciprofloxacin (80.6%), and cefepime (73.7%). Most patients (82.1%) had at least one underlying illness. Combination antimicrobial therapy was administered in 28.2% of cases. One patient died during hospitalization. The length of hospital stay was longer in patients with polymicrobial compared to monomicrobial infections (23 versus 13 days, respectively, p = 0.02). The isolation of Citrobacter species, although rather infrequent, was clinically relevant in the great majority of cases. Further attention should be paid to these pathogens.

Treatment of Citrobacter kosen Infection with Ciprofloxacin and Cefotaxime in a Preterm Infant

To report a case of successful treatment of Citrobacter koseri infection in a preterm infant as a means of challenging the current treatment recommendations on the basis of pharmacodynamic and pharmacokinetic considerations. A premature infant was diagnosed with C. koseri sepsis after 3 weeks in intensive care. Concern for meningitis was based on the propensity for central nervous system (CNS) involvement with Citrobacter infection along with new findings of ventriculomegaly and hydrocephalus shown on cranial ultrasound (CUS). The infant was treated with ciprofloxacin 10-20 mg/day and cefotaxime 100 mg/day for 21 days. After treatment, lumbar puncture was normal, follow-up CUS returned to baseline, and the infant passed a hearing screen after discharge. A favorable outcome was achieved in this case. Approximately 76% of neonatal patients infected with C. koseri develop brain abscesses. The mortality rate for meningitis due to Citrobacter spp. is approximately 30%, and of the infants who survive, more than 80% have some degree of mental retardation. Third-generation cephalosporins and aminoglycosides are traditional therapies against this infection. The current antibiotic strategies have failed to prevent the high rates of morbidity and mortality associated with Citrobacter infections. A possible basis for these poor outcomes is failure to apply appropriate pharmacokinetic and pharmacodynamic principles in selecting antibiotics that will achieve adequate concentrations to kill the bacteria in granulocytes within the CNS. Based on favorable sensitivity data, penetration into neutrophils and the CNS, and favorable toxicity profiles, ciprofloxacin and meropenem would appear to be the most appropriate antibiotic treatment options for systemic infection or meningitis caused by C. koseri. Ciprofloxacin and meropenem should be considered antibiotic treatment options for systemic infection or meningitis caused by C. koseri.

Citrobacter infections in a tertiary care hospital in Northern India

This prospective study was carried out to look for the frequency of isolation of Citrobacter species from clinical specimens and study their antimicrobial susceptibility pattern. Patients from whom Citrobacter species were isolated during routine diagnostic testing from January to December 2004 were included in the study. Isolates were identified by standard biochemical tests. Antimicrobial susceptibility testing was performed by disk diffusion method as per National Committee of Clinical Laboratory Standards (NCCLS) guidelines. Citrobacter species were isolated from a total of 205 patients. Infection was nosocomially acquired in 94.6% patients. One hundred eighty one (88.3%) patients had significant underlying illnesses. Culture yielded Citrobacter koseri in 185 (90.2%) and Citrobacter freundii in 20 (9.8%) patients. The distribution of isolates was as follows: urine (46.2%), respiratory tract (16.3%), blood (15.8%), pus (12.1%) and sterile body fluids (9.3%). Drug resistance was observed to be more in C. koseri as compared to C. freundii. Citrobacter infections are often nosocomially acquired, seen in patients with significant underlying diseases and isolates are commonly drug-resistant. Adoption of hospital infection control practices and a good antibiotic policy may prevent their spread.

Differentiation and susceptibility of Citrobacter isolates from patients in a university hospital.

OBJECTIVE: Recently a publication of Brenner et al. introduced 11 genetically distinct species within the genus Citrobacter. These newly recognized Citrobacter species can be classified by means of their biochemical characteristics. The aim of this study was to examine the distribution and susceptibility of Citrobacter isolates in our patient population. METHODS: A total of 126 samples---containing a Citrobacter species---was collected from 116 hospitalized patients during a 6-month period. Organisms were identified according to standard procedures. Antimicrobial susceptibility testing was performed by agar dilution on Mueller-Hinton agar, and interpretation was based on NCCLS criteria. RESULTS: C. freundii was the most common organism isolated (n=59), followed by C. braakii (n=25) and C. koseri (n=23). The urinary tract and the respiratory tract were found to be the predominant sites of colonization or infection, accounting for 45% and 32% of all isolates respectively. It appeared that young children (<12 months old) and the elderly were most at risk of acquiring Citrobacter. Two-thirds of all specimens contained other organisms in addition to Citrobacter. Most Citrobacter isolates were related with a predisposing factor. Species-related differences were found in the susceptibility pattern. CONCLUSIONS: These findings suggest that citrobacteria are important opportunistic pathogens contributing to colonization or infection in our hospital population.

Antibiotic Susceptibility of 629 Bacterial Blood and CSF Isolates from Swedish Infants and the Therapeutic Implications

Blood and CSF isolates (n = 629) from Swedish infants up to one year of age were tested in vitro against 13 antimicrobial agents in order to update the guidelines for empiric therapy of septicaemia and meningitis. Ampicillin plus gentamicin provided inadequate empiric therapy for meningitis, due to the poor CSF penetration of the aminoglycoside and the frequent occurrence of bacterial resistance to ampicillin. Ceftazidime and cefuroxime were moderately active, particularly against isolates from small infants. Cefotaxime today seemed to provide the best empiric therapy of septicaemia and meningitis in infants. Because of the occurrence of Listeria and enterococcal infections, ampicillin should initially be added and other combinations are also advisable for the occasional cases of Enterobacter, Citrobacter, Serratia, and Pseudomonas infections. For coagulase-negative staphylococci only vancomycin offered a broad activity (100% at achievable serum levels).