Carbenicillin therapy of Pseudomonas and other gram-negative bacillary infections

Identification of host genetic factors modulating β-lactam resistance in Escherichia coli harbouring plasmid-borne β-lactamase through transposon-sequencing

Since β-lactam antibiotics are widely used, emergence of bacteria with resistance to them poses a significant threat to society. In particular, acquisition of genes encoding β-lactamase, an enzyme that degrades β-lactam antibiotics, has been a major contributing factor in the emergence of bacteria that are resistant to β-lactam antibiotics. However, relatively few genetic targets for killing these resistant bacteria have been identified to date. Here, we used a systematic approach called transposon-sequencing (Tn-Seq), to screen the Escherichia coli genome for host genetic factors that, when mutated, affect resistance to ampicillin, one of the β-lactam antibiotics, in a strain carrying a plasmid that encodes β-lactamase. This approach enabled not just the isolation of genes previously known to affect β-lactam resistance, but the additional loci skp, gshA, phoPQ and ypfN. Individual mutations in these genes modestly but consistently affected antibiotic resistance. We have identified that these genes are not only implicated in β-lactam resistance by itself but also play a crucial role in conditions associated with the expression of β-lactamase. GshA and phoPQ appear to contribute to β-lactam resistance by regulating membrane integrity. Notably, the overexpression of the uncharacterized membrane-associated protein, ypfN, has been shown to significantly enhance β-lactam resistance. We applied the genes identified from the screening into Salmonella Typhimurium and Pseudomonas aeruginosa strains, both critical human pathogens with antibiotic resistance, and observed their significant impact on β-lactam resistance. Therefore, these genes can potentially be utilized as therapeutic targets to control the survival of β-lactamase-producing bacteria.

Neurological Adverse Effects Attributable to β-Lactam Antibiotics: A Literature Review

β-lactam antibiotics are commonly prescribed antibiotic drugs. To describe the clinical characteristics, risk markers and outcomes of β-lactam antibiotic-induced neurological adverse effects, we performed a general literature review to provide updated clinical data about the most used β-lactam antibiotics. For selected drugs in each class available in France (ticarcillin, piperacillin, temocillin, ceftazidime, cefepime, cefpirome, ceftaroline, ceftobiprole, ceftolozane, ertapenem and aztreonam), a systematic literature review was performed up to April 2016 via an electronic search on PubMed. Articles that reported original data, written in French, Spanish, Portuguese or English, with available individual data for patients with neurological symptoms (such as seizure, disturbed vigilance, confusional state, myoclonia, localising signs, and/or hallucinations) after the introduction of a β-lactam antibiotic were included. The neurological adverse effects of piperacillin and ertapenem are often described as seizures and hallucinations (>50 and 25% of cases, respectively). Antibiotic treatment is often adapted to renal function (>70%), and underlying brain abnormalities are seen in one in four to one in three cases. By contrast, the neurological adverse drug reactions of ceftazidime and cefepime often include abnormal movements but few hallucinations and seizures. These reactions are associated with renal insufficiency (>80%) and doses are rarely adapted to renal function. Otherwise, it appears that monobactams do not have serious neurological adverse drug reactions and that valproic acid and carbapenem combinations should be avoided. The onset of disturbed vigilance, myoclonus, and/or seizure in a patient taking β-lactam antibiotics, especially if associated with renal insufficiency or underlying brain abnormalities, should lead physicians to suspect adverse drug reactions and to consider changes in antibacterial therapy.

Penicillins. A current review of their clinical pharmacology and therapeutic use

The penicillins are a large group of bicyclic ring compounds which contain a 4-membered beta-lactam ring (penams) fused to a 5-membered thiazolidine ring. Benzylpenicillin (penicillin G) was the first natural penicillin with potent activity against all Gram-positive pathogens, Gram-negative cocci and some spirochaetes and actinomycetes. For the last 50 years benzylpenicillin has been the mainstay of therapy for serious pneumococcal, streptococcal, meningococcal and gonococcal infections. However, the past decade has seen the emergence of resistance in certain parts of the world, initially among the gonococci, and more recently among the pneumococci and meningococci. Discovery of the 6-aminopenicillinamic acid nucleus has led to considerable manipulation of the basic ring structure, resulting initially in the synthesis of ampicillin, and subsequently the other aminopenicillins, analogues, esters and prodrugs. These drugs have the advantages of improved oral bioavailability and superior activity against Haemophilus influenzae, certain Gram-negative bacilli, salmonellae, enterococci and Listeria monocytogenes, making these agents popular in the treatment of upper and lower respiratory tract infections and urinary tract infections. The increasing spread of bacterial resistance, particularly among Enterobacteriaceae and H. influenzae, has curtailed the usefulness of these drugs in these clinical settings. To counteract this problem, a number of agents combining a penicillin and a beta-lactamase inhibitor (e.g. clavulanic acid, tazobactam and sulbactam) have been developed. These inhibitors have no intrinsic antibacterial activity, but combining them with a penicillin (e.g. amoxicillin/clavulanic acid) confers greater stability to beta-lactamases and hence a broader spectrum of activity. The emergence of penicillinase-producing staphylococci that rendered benzylpenicillin ineffective also stimulated the search for penicillinase-resistant penicillins--methicillin and nafcillin, followed by the acid-stable isoxazolyl penicillins. These agents are now the principle antistaphylococcal treatment. Methicillin-resistant coagulase-negative staphylococci are currently a major cause of hospital sepsis, and are resistant to these latter agents. Enteric Gram-negative bacilli have been the predominant cause of serious hospital infections during the last 30 years. Further manipulation of the penicillin structure has resulted in compounds with broader activity against Gram-negative bacilli, particularly Pseudomonas aeruginosa, while retaining activity against Gram-positive pathogens. The carboxypenicillins were the first step in this direction, but have been largely superseded by the ureidopenicillins. These agents have better activity against P. aeruginosa, and are still effective against Gram-negative and Gram-positive bacteria, including enterococci and anaerobic organisms.(ABSTRACT TRUNCATED AT 400 WORDS)

The penicillins

The penicillin family of antibiotics is ever expanding and remains an important part of our antimicrobial armamentarium. These medications generally have bactericidal activity, excellent distribution throughout the body, low toxicity, and efficacy against infections due to susceptible organisms. The clinical introduction of aqueous penicillin G for treatment of streptococcal and staphylococcal infections was an important pharmacologic landmark. The emergence of penicillinase-producing staphylococci prompted the development of the penicillinase-resistant penicillins (methicillin, oxacillin, nafcillin, and others), in which the acyl side chain prevented disruption of the beta-lactamase ring. The aminopenicillins (ampicillin, amoxicillin, and others) were later developed because of the need for gram-negative antimicrobial activity. Their spectrum included Escherichia coli, Proteus mirabilis, Shigella, Salmonella, Listeria, and Haemophilus. The search for a penicillin with even further antimicrobial activity against the Enterobacteriaceae and Pseudomonas aeruginosa led to the development of the carboxypenicillins, ureidopenicillins, and piperazine penicillins. Recently, the combination of a beta-lactamase inhibitor (clavulanic acid or sulbactam) and an amino-penicillin or ticarcillin has resulted in further extension of their antibacterial spectra. The development of an ideal penicillin that is nonsensitizing, bioavailable, beta-lactamase-resistant, rapidly bactericidal, nontoxic, and inexpensive and that has high affinity to penicillin-binding proteins and no inoculum effect remains the goal.

A preliminary study on the use of carbenicillin in snakes

The results of a 10 year survey on the in vitro antibiotic resistance patterns of Pseudomonas spp. isolated from clinically ill reptiles, showed a high degree of sensitivity to carbenicillin. On the basis of sensitivity testing, carbenicillin was used to treat nine snakes of four different species, with confirmed Pseudomonas infections. Plasma carbenicillin levels were assayed, by a microbiological agar diffusion technique, at intervals of time after a single intramuscular injection at a dose rate of 400 mg/kg. Peak plasma levels of 177 and 270 micrograms/ml were reached 1 h after the initial injection and therapeutic levels persisted for at least 12 h. This initial study indicated that a suggested dose regime in snakes, derived by extrapolation from mammalian dosages, of 100-125 mg/kg daily was insufficient to produce plasma levels of sufficient magnitude and duration to effectively treat Pseudomonas infections in snakes.

Treatment of respiratory infections in the patient at risk

Therapeutic intervention of varying potency and toxicity is now available for bacterial, fungal, parasitic, and viral pneumonia, but the problem of establishing the precise origin to evaluate treatment protocols remains. Antibacterial agents reduce postinfluenzal morbidity and mortality. Earlier appropriate treatment of gram-positive coccal infections has reduced mortality to less than 10 percent unless bacteremia is present. Gram-negative bacillary pneumonia remains a major problem and response rates do not exceed 65 percent except in selected series in which two effective antimicrobial agents have been used. Nevertheless, the superiority of two agents has not convincingly been demonstrated in any retrospective series or prospective randomized trial; more efficacy data in patients with gram-negative pneumonia treated with the newer beta-lactam agents would be useful. Little information is available on the laboratory correlates of successful treatment of gram-negative pneumonia, such as sputum antibiotic levels. Moreover, aerosolization of antimicrobial agents has been used with reported success by some investigators, but this therapeutic approach remains controversial. Pneumonia or lung abscess due to anaerobes may require increasingly larger doses of penicillin or alternative antianaerobe agents. Parasitic pneumonias such as those due to Pneumocystis carinii have responded well to trimethoprim-sulfamethoxazole. Acyclovir appears effective against some herpes viruses (simplex and varicella zoster), but it has failed to affect cytomegalovirus pneumonia even when combined with interferon. Opportunistic fungal pneumonias are poorly treated with all available agents and usually do not respond unless there is amelioration of predisposing factors or improvement in underlying disease. The latter statement appears relevant in most patients with severely compromised host defenses and pulmonary infection.

Use of ureidopenicillins for selection of plasmid vector transformants in Pseudomonas aeruginosa and Pseudomonas putida

Broad-host-range plasmids coding for beta-lactamase were successfully selected after transformation of Pseudomonas strains. Transformants of both Pseudomonas aeruginosa and Pseudomonas putida containing plasmid pRO1614 were isolated in media containing low concentrations of piperacillin. These strains were also susceptible to other ureidopenicillins. Similar selections of transformants with carbenicillin, ampicillin, or ticarcillin required high concentrations of antibiotics and yielded backgrounds of spontaneous resistant mutants.

Hospital outbreaks caused by Pseudomonas aeruginosa: importance of serogroup O11

Suspected outbreaks caused by pseudomonas aeruginosa in 19 hospitals and two motels were studied. On the basis of epidemiological analysis, serological typing, and antibiotic resistance patterns, 17 were classified as single-strain outbreaks. Six were classified as common-source outbreaks: of these, three were caused by contaminated urological instruments or solutions, two involved bathing in contaminated whirlpools, and one was caused by contaminated lens prostheses implanted during eye surgery. The ability of P. aeruginosa to survive or grow in wet environments was important in each of these six outbreaks. Eight outbreaks were classified as cross-infection. Two involved the urinary tract and were caused by antibiotic-resistant strains. Six involved the respiratory tract, but only one was caused by an antibiotic-resistant strain. In 2 of the 17 single-strain outbreaks, the exact mode of transmission could not be determined. One was an outbreak of pseudobacteremia in which patient blood cultures were contaminated with a single strain, presumably during collection of specimens or culture processing, P. aeruginosa serogroup O11 caused 9 of 17 (53%) single-strain outbreaks, a surprising finding since this serogroup represents only about 8% of endemic hospital isolates of this species. Serotyping was very useful in epidemiological analysis, but antibiotic susceptibility patterns were less useful.

Carbenicillin and ticarcillin

Carbenicillin and ticarcillin are penicillins which were initially developed as agents to treat serious Pseudomonas infections in the seriously ill hospitalized patient. These drugs have made a major contribution to improved survival in the neutropenic patients with Pseudomonas infection, the burn patient and to the care of the patient with cystic fibrosis. Areas of use for the compounds have enlarged to include aspiration pneumonitis in hospitalized patients, intra-abdominal and pelvic sepsis, and infections due to Proteus and Enterobacter species. Careful attention to the pharmacology of the agents is necessary to achieve clinical and bacteriologic success and to avoid the toxic side-effects such as bleeding and hypokalemia associated with the use of these agents. A decade of use has shown that the agents have remained effective agents in institutions in which their use has not been abused. It is too early to clearly position azlocillin, mezlocillin, and piperacillin. In the next few years the role of these potent compounds will be established. As noted in this review, these three agents have been used with success to treat all of the aforementioned infections. With these drugs it is also essential that the physician closely correlate in vitro data and the human pharmacology of the drugs if he or she wishes to achieve the most effective response from the agents.

Clinical trial of piperacillin with acquisition of resistance by Pseudomonas and clinical relapse

A total of 20 serious infections were treated with piperacillin. These infections included bacteremias (5), pneumonias (5), urinary tract infections (5), soft tissue infections (3), septic arthritis (1), and osteomyelitis (1). The most common bacterial pathogen was Pseudomonas aeruginosa, accounting for eight infections. The clinical and bacteriological response rates were 75 and 70%, respectively. Four of the five patients who failed to respond to piperacillin therapy were infected with Pseudomonas. In two patients with Pseudomonas infections clinical relapse was accompanied by the development of piperacillin-resistant P. aeruginosa. The findings suggest that the use of piperacillin as a single agent for the treatment of serious gram-negative infections may be ill-advised, especially if P. aeruginosa is the offending pathogen.

Infectious complications of burns casualties during the Yom-Kippur War

During the October 1973 military conflict, 41 burned patients hospitalized at the Sheba Medical Center were closely followed up. All the patients who had burns occupying 20% or more of the body surface developed wound infections. Pseudomonas aeruginosa was the major pathogen isolated. Most infections occurred during the second week following the injury. Serial cultures revealed that only the isolation of Proteus species and P. aeruginosa from wounds could predict an infection caused by those microorganisms. During treatment with gentamicin and carbenicillin a marked increase in carbenicillin-resistant P. aeruginosa and gentamicin-resistant Klebsiella strains was noted. Cross-infections with carbenicillin-resistant P. aeruginosa was not a major cause in the development of resistant strains.

Drug administration in renal failure

Renal failure impairs urinary excretion of drugs and may also modify drug action by alternations in protein binding, distribution, biotransformation and, possibly, by retention of active metabolites. Dialysis adds another variable by altering the blood levels of those drugs soluble in plasma water and therefore available for diffusion or ultrafiltration. Renal insufficiency clearly modifies decisions about the choice and dose of a wide variety of drugs. Although data are accumulating at a rapid rate, available information about the use of drugs in patients with kidney disease is rather limited. The following is a summary of recent information on the use of a variety of drugs frequently utilized in patients with impaired renal function. The guidelines presented here are not absolute, but they are intended to be practical and reasonable, based on current information for adult patients of average size with kidney disease.

Pseudomonas bacteremia. Review of 108 cases

The current circumstances associated with Pseudomonas aeruginosa bacteremia are reviewed in 108 episodes to assess the impact of new antimicrobial drugs on this infection. Since 1961, Pseudomonas bacteremia has apparently become more frequent with proportional increases in middle-aged patients. The respiratory tract has become the major source of infection. Clinical features are not characteristic, but infected patients are almost uniformly severely ill before blood stream invasion occurs. The use of gentamicin, carbenicillin and colistin has not changed the outcome of Pseudomonas bacteremia. Although better than no antimicrobial treatment, these drugs cannot be shown to be superior to any other available antibiotics. A reassessment is needed to evaluate the relationship between the in vitro action and the effectiveness of antibiotics in the treatment of Pseudomonas infection and the use of gentamicin, carbenicillin and colistin in these bacteremias. In view of the poor results with antibiotics, investigation into immunologic prophylaxis and therapy is needed. At the present time, control of the patients' underlying disease contributes most towards assuring survival with Pseudomonas bacteremia.

Frequency of transferable drug resistance in clinical isolates of Klebsiella, Aerobacter, and Escherichia

Twenty-seven patients with serious gram-negative infections were treated with ticarcillin in an average daily dosage of 237 mg/kg (range, 174 to 307 mg/kg). Ticarcillin was bactericidal for all infecting organisms in concentrations ranging from 31.2 to 125 μg/ml. Five of 8 patients (62%) with overwhelming Pseudomonas pneumonia were cured or improved, and 9 of 12 (75%) were cured of pneumonia caused by other gram-negative organisms. Of six extrapulmonary infections caused by Pseudomonas, five (83%) were cured or improved. In seven cases, the infecting organism reisolated during therapy was more resistant to ticarcillin than the primary isolate. The serum half-life of ticarcillin in three patients with renal failure was 11.2 ± 1.0 h, and during hemodialysis it decreased to 6.3 ± 1.8 h. There were two episodes of superinfection with resistant organisms. Thirteen patients (48%) manifested eosinophilia, one of whom had severe urticaria. Prolongation of bleeding time was attributable to ticarcillin in two patients. Ticarcillin appears to be effective for therapy of serious gram-negative infections in dosages 30 to 50% less than those recommended for carbenicillin.

Cerebral toxicity of penicillins in relation to their hydrophobic character

The neurotoxic effects of ticarcillin, methicillin, phenthicillin, oxacillin, cloxacillin and dicloxacillin were studied in the conscious rabbit. During and after intravenous administration of 1.2 and 2.4 g/kg, resp., over 50 min the blood concentrations of the drugs were determined and the neurotoxicity assessed by continuous recording of the electroencephalogram. The hydrophobia of the penicillins was characterized by determination of their partition coefficients between isobutanol and buffer solution pH 7.4. The penicillins showed quite different neurotoxic properties. A close correlation (r = 0.928) was found between the neurotoxic potency of the penicillins and their partition coefficients. With increasing hydrophobia the neurotoxic potency increased in the following sequence: Ticarcillin, methicillin, oxacillin, phenethicillin, cloxacillin, dicloxacillin. It can be concluded, therefore, that determination of the partition coefficient of a penicillin gives valuable information on the neurotoxicity to be expected. The introduction of a neurotoxicity quotient revealed that penicillins may be divided into two groups: less neurotoxic penicillins with a partition coefficient below 1.0 and highly neurotoxic penicillins with a partition coefficient above 1.0.

Survival of candida septicaemia treated with amphotericin B

Candida albicans septicaemia occurred in an alcoholic woman who had severe hepatic dysfunction, and was further debilitated by multiple cardiac arrests, prolonged artificial ventilation, bronchopneumonia and Ps. aeruginosa septicaemia. She received broad spectrum antibiotics and corticosteroids, and needed prolonged intravenous cannulation. In vitro, a specific defect was demonstrated in her cell-mediated immune response to candida antigens. Examination of her serum showed normal immunoglobulins, and an adequate agglutination titre to these antigens.

Amphotericin B (800 mg intravenously over 19 days) was administered, and she survived. Hypokalaemia, anaemia, and peripheral neuropathy complicated therapy, and thrombophlebitis of a cannulated peripheral vein necessitated a vena caval catheter. There was no significant deterioration of renal function.

Toxic effects of other drugs were encountered—deafness following kanamycin, an encephalopathy when blood levels of carbenicillin were boosted by probenecid, and cardiac arrest when diazepam and phenobarbitone were administered to control an epileptic fit and delirium tremens. Prolonged intravenous cannulation was complicated by staphylococcal septicaemia.

A year later she died of peritonitis. Chronic pancreatitis was complicated by ascites, which became infected by E. coli. No residual C. albicans infection was found at necropsy.

In vitro studies of alpha-carboxyl-3-thienylmethyl penicillin, a new semisynthetic penicillin

The activity of a new semisynthetic penicillin, alpha-carboxyl-3-thienylmethyl penicillin (BRL-2288) was determined against 535 clinical isolates of gram-negative bacilli, by using the tube dilution technique. Nearly 80% of isolates of Proteus spp. were inhibited by 3.12 mug or less of this antibiotic per ml. BRL-2288 was as active as ampicillin against Escherichia coli. It was slightly more active than carbenicillin or 6-(d-alpha-sulfoaminophenylacetamido)-penicillanic acid against Pseudomonas sp., with over half of the isolates being inhibited by 50 mug or less of BRL-2288 per ml. Isolates of Klebsiella sp. were routinely resistant to this antibiotic. The drug was bactericidal against most sensitive organisms. BRL-2288 was less active against large inocula. A strain of Pseudomonas sp. which developed resistance to carbenicillin also developed resistance to BRL-2288 simultaneously.