Emergence of resistance to multiple beta-lactams in Enterobacter cloacae during treatment for neonatal meningitis with cefotaxime

Enterobacter meningitis: organism susceptibilities, antimicrobial therapy and related outcomes

BACKGROUND

Meningitis due to Enterobacter species is an uncommon infection in adults; however, when present, treatment is frequently complicated by resistance of many Enterobacter isolates to third-generation cephalosporins and poor central nervous system penetration of other antibiotics. The aim of this study was to retrospectively review cases of meningitis caused by Enterobacter species at our institution, to better characterize patient factors, pathogen characteristics, and treatment options for this infection.

METHODS

We reviewed all cases of Enterobacter meningitis in a 12-year period at a tertiary care center. Data collected included patient demographics, antibiotic sensitivities of Enterobacter isolates, antimicrobial therapy, and patient outcomes.

RESULTS

Nineteen cases were identified, primarily in patients with neurotrauma and in neurosurgical patients. Enterobacter cloacae was the most frequent Enterobacter species isolated followed by Enterobacter aerogenes and Enterobacter agglomerans (50%, 34%, and 16% of cultures, respectively). Overall, clinical cure/improvement was achieved in 47% of patients, and the mortality rate was 21%. Antibiotic treatment varied substantially and included third-generation cephalosporins, intravenous and intrathecal aminoglycosides, trimethoprim-sulfamethoxazole (TMP-SMX), piperacillin, ciprofloxacin, and other miscellaneous antibiotics. Treatment with TMP-SMX was associated with a high rate of clinical cure/improvement, whereas third-generation cephalosporins were less efficacious.

CONCLUSIONS

Enterobacter meningitis is an infrequent complication of neurological insult. Treatment is often complicated by resistance of Enterobacter species to third-generation cephalosporins. Our results indicate that while third-generation cephalosporins are not the most appropriate choice of agents to treat Enterobacter meningitis, TMP-SMX may yield satisfactory results.

Antimicrobial resistance among gram-negative organisms in the intensive care unit

PURPOSE OF REVIEW

We review the hospital-acquired gram-negative organisms commonly encountered among patients in the intensive care unit and discuss pertinent surveillance data, resistance mechanisms and patterns, and optimal treatment regimens for these pathogens.

RECENT FINDINGS

There has been a notable increase in antibiotic resistance among gram-negative intensive care unit pathogens. Data from surveillance programs such as National Nosocomial Infections Surveillance System, Intensive Care Antimicrobial Resistance Epidemiology, and others have documented undesirable trends in antibiotic resistance, indicating decreasing efficacy of antibiotic classes such as third-generation cephalosporins, carbapenems, and fluoroquinolones, The increased prevalence of extended-spectrum beta-lactamases has contributed to the finding of multidrug resistance among bacteria such as Klebsiella and Escherichia coli. Furthermore, organisms such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia display intrinsic resistance to many antibiotics, making selection of optimal therapy difficult. Studies have correlated infection by these organisms with prior antibiotic exposure, and containment of the spread of infection can be achieved by careful antibiotic use and infection control practices.

SUMMARY

Antibiotic resistance continues to rise among hospital-acquired gram-negative pathogens. Optimal management of these infections requires knowledge of local epidemiology and practices to control their spread.

Clinical implications of inducible beta-lactamase activity in Gram-negative bacteremia in children

BACKGROUND

Organisms of the spp., indole-positive spp., spp. and (ESCaPPM) group are a common cause of hospital-acquired bacteremia and share the potential to develop beta-lactam resistance during therapy. The emergence of such resistance may have adverse consequences, but the frequency with which this occurs has not been studied in children. It has been suggested that such organisms should be treated with combination antimicrobials or carbapenems, but the optimal regimen is uncertain. AIM To determine the frequency with which beta-lactam resistance develops during ESCaPPM sepsis in children and the optimal treatment of such sepsis.

METHODS

A review of the case notes and microbiologic records of all cases of ESCaPPM bacteremia and meningitis managed at a tertiary children's hospital during a 6-year period.

RESULTS

Fifty-eight cases were identified, and in three (5%) cases beta-lactam resistance emerged during treatment, with adverse clinical consequences in two cases. Clinical and microbiologic outcome was similar in those treated with carbapenems and in those treated with a beta-lactam and aminoglycoside combination. Cefotaxime resistance was found in 57, 30, 24 and 7% of children who had received carbapenems, cephalosporins, penicillins or no/other antimicrobials in the month before ESCaPPM sepsis, respectively.

CONCLUSIONS

The emergence of beta-lactam resistance during treatment of ESCaPPM sepsis is uncommon in our hospital but can have adverse consequences. Where isolates are reported as susceptible to both classes of drugs, an extended spectrum penicillin in combination with an aminoglycoside may be preferable first line treatment of ESCaPPM sepsis to a carbapenem or quinolone.

Meropenem compared with ceftazidime in the empiric treatment of acute severe infections in hospitalized children. Italian Pediatric Meropenem Study Group

In a multicenter, randomized, open comparison of meropenem to ceftazidime as empiric treatment of severe acute infections, 185 children (1 mo-15 years old, mean 65.4 mo) were enrolled. Meropenem (20 mg/kg t.i.d. i.v.) was given to 98 and ceftazidime (10-30 mg/kg t.i.d. i.v.) to 87 children, generally for 5 to 10 days (mean: 6.9 for meropenem and 7.5 for ceftazidime). Clinical response was evaluated at the beginning and at the end of therapy and 4 weeks later (follow-up). Clinical response was deemed satisfactory at the end of therapy in 96.7% of the patients treated with meropenem and in 95.3% of those who received ceftazidime without any statistically significant difference. One relapse occurred in a meropenem-treated patient at the follow-up clinical assessment. The baseline infecting organism was eradicated or presumed eradicated at the end of therapy in 14/16 patients treated with meropenem and in 14/15 treated with ceftazidime. The incidence of drug-related adverse events (mostly a slight increase in liver enzymes) was 9.2% in the meropenem group and 4.6% in the ceftazidime group. Our data show that meropenem is as effective as ceftazidime in the empiric treatment of severe infections in infants and children.

Specificity of the high-mannose recognition site between Enterobacter cloacae pili adhesin and HT-29 cell membranes

Enterobacter cloacae has been implicated as one of the causative agents in neonatal infection and causes a septicemia thought to be initiated via the gastrointestinal tract. The adhesion of radiolabeled E. cloacae to HT-29 cells was concentration and temperature dependent and was effectively blocked by unlabeled bacteria or by millimolar concentrations of alpha-mannosides and micromolar concentrations of high-mannose oligosaccharides. A variety of well-characterized mannose oligosaccharides were tested as inhibitors of adhesion. The best inhibitor was the Man9(GlcNAc)2-tyrosinamide, which was considerably better than other tyrosinamide-linked oligosaccharides such as Man7(GlcNAc)2, Man6(GlcNAc)2 or Man5(GlcNAc)2. Further evidence that the bacteria preferred Man9(GlcNAc)2 structures was obtained by growing HT-29 cells in the presence of glycoprotein processing inhibitors that block mannosidase I and increase the amount of protein-bound Man9(GlcNAc)2 at the cell surface. Such cells bound 1.5- to 2-fold more bacteria than did control cells. The adhesin involved in binding to high-mannose structures was purified from isolated pili. On sodium dodecyl sulfate-gels, a 35-kDa protein was identified by its specific binding to a mannose-containing biotinylated albumin. The amino acid sequences of several peptides from the 35-kDa subunit showed over 85% identity to FimH, the mannose-specific adhesin of Salmonella typhimurium. Pili were labeled with 125I and examined for the ability to bind to HT-29 cells. Binding showed saturation kinetics and was inhibited by the addition of Man9(GlcNAc)2-tyrosinamide but not by oligosaccharides with fewer mannose residues. Polyclonal antibody against this 35-kDa protein also effectively blocked adhesion of pili or E. cloacae, but no effect was observed with nonspecific antibody. These studies demonstrate that the 35-kDa pilus subunit is a lectin whose specificity is directed toward Man, (GlcNAc)2 oligosaccharides.

Bacterial urinary tract infections in diabetes

Diabetes mellitus has a number of long-term effects on the genitourinary system. These effects predispose to bacterial urinary tract infections in the patient with diabetes mellitus. Bacteriuria is more common in diabetic women than in nondiabetic women because of a combination of host and local risk factors. Upper tract infection complications are also more common in this group. Diabetic patients are at higher risk for intrarenal abscess, with a spectrum of disease ranging from acute focal bacterial pyelonephritis to renal corticomedullary abscess, to the renal carbuncle. A number of uncommon complicated urinary tract infection complications occur more frequently in diabetics, such as emphysematous pyelonephritis and emphysematous pyelitis. Because of the frequency and severity of urinary tract infection in diabetic patients, prompt diagnosis and early therapy is warranted. A plain abdominal radiograph is recommended as a minimum radiographic screening tool in the patient with diabetes presenting with systemic signs of urinary tract infection. Ultrasonography or further radiographic studies such as CT scanning may also be warranted, depending on the clinical picture, to identify upper urinary tract complications early for appropriate intervention.

Enterobacter spp.: pathogens poised to flourish at the turn of the century

Knowledge of the genus Enterobacter and its role in human disease has expanded exponentially in recent years. The incidence of infection in the hospital and the community has increased. New clinical syndromes have been recognized. Enterobacter spp. have also been implicated as causes of other syndromes that traditionally have been associated almost exclusively with more easily treatable pathogens, such as group A streptococci and staphylococci. Rapid emergence of multiple-drug resistance has been documented in individual patients during therapy and in populations and environments with strong selective pressure from antimicrobial agents, especially the cephalosporins. Therapeutic options for patients infected with multiply resistant strains have become severely limited. Carbapenems or, alternatively, fluoroquinolones are the most predictively active options, although resistance to both classes has been observed on rare occasions. Enterobacter spp. appear well adapted for survival and even proliferation as the turn of the century approaches.

Transient in vivo selection of a constitutively cephalosporin resistant Enterobacter cloacae causing ventriculitis

A case of neonatal ventriculitis complicating a ventriculoperitoneal shunt and caused by one strain of Enterobacter cloacae (as shown on pulsed field gel electrophoresis) is presented. Daily ventricular fluid cultures from day 1 to 9 revealed inducible cephalosporin resistance in all isolates except on days 3, 4 and 5 of therapy when isolates were constitutively resistant. This emergence of resistance due to constitutive Bush class 1 beta-lactamase production is an excellent example of the rapid emergence of a predominant strain of bacteria depending on antibiotic selection pressures in vivo. The transient nature of the predominant resistant phenotype may have been due to missing a dose of cefotaxime on day 5 or in vivo factors allowing persistence of sensitive organisms in antibiotic protected sites. Caution is advised in the use of cephalosporins alone for serious Enterobacter species infections. Repeat culture and sensitivity should be done in severe infections that are slow to respond to cephalosporin therapy.

Enterobacter cloacae in a neonatal intensive care unit: account of an outbreak and its relationship to use of third generation cephalosporins

After uneventful use of cefotaxime and ceftazidime as first line therapy for three years in our neonatal intensive care unit we isolated cephalosporin-resistant Enterobacter cloacae (CREC) strains which caused clusters of cases or colonization and/or serious neonatal infection. By using two or more typing methods, at least five different strains with similar patterns of antimicrobial sensitivities were identified. The results of a case-control study did not support the notion that the use of third generation cephalosporins was associated with colonization and infection by CREC. The outbreak was brought under control by interrupting the transmission of the epidemic strain D, by measures such as cohort nursing, diligent handwashing before and after procedures, and thorough environmental cleaning as well as by decontamination with glutaraldehyde after dismantling of the blood gas analyser believed to have acted as a persistent reservoir. Our experience highlights the danger of inadequate supervision and maintenance of equipment used for near-patient testing and the need to monitor such equipment not only in terms of its calibration and analytical performance but also microbiologically.

A comparison of ceftazidime and aminoglycoside based regimens as empirical treatment in 1316 cases of suspected sepsis in the newborn. European Society for Paediatric Infectious Diseases--Neonatal Sepsis Study Group

We report a prospective, non-blind, randomised, multicentre, parallel group, multinational investigation to compare ceftazidime to aminoglycoside based regimens as empirical treatment in 1316 cases of suspected sepsis in the newborn. In each of the 15 study centres either ceftazidime alone (CAZ) or ceftazidime + ampicillin (CAZ + AMP) was compared to an amino-glycoside/ampicillin combination (AG + AMP). In all cases treatment was based on "an intention to treat". Bacteria considered to be pathogenic were isolated from 176/1316 (13.4%) patients. The incidence of proven infection varied from 39% in a Yugoslav centre to 6% in a British centre; a further 489/1316 (37.1%) patients fulfilled the criteria for clinically suspected sepsis. A total of 210 bacterial isolates from 197 infection sites in 176 patients were considered to be clinically significant. The cure rate for evaluable patients with proven infection who were treated with CAZ + AMP (97%, 30/31) was significantly higher than that for the corresponding patients treated with AG + AMP (66%, 26/39), (P < 0.002). The difference in cure rate between CAZ monotherapy (79%, 34/43) and AG + AMP (86%, 32/37) was not significant. Treatment failed in 28/150 (18.7%) evaluable patients. There were significantly fewer failures (P < 0.001) with CAZ + AMP than with AG + AMP therapy. There were 55 staphylococcal infections. Treatment was successful in 16/19 evaluable patients treated with CAZ or CAZ + AMP and in 16/29 evaluable patients treated with AG + AMP. None of the study centres encountered problems with ceftazidime resistant bacteria. The cure rate for patients with only clinical and radiological evidence of sepsis was greater than 94% in all treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)