Pasteurella Multocida Infection Medication

Antimicrobial resistance among Pasteurella isolates is rarely reported in humans. Tetracyclines, erythromycin, and penicillin are most commonly associated with resistance. Penicillin-resistant strains have been isolated only from respiratory tract infections. Most animal-bite injuries can be treated with oral antimicrobials on an outpatient basis. Severe or partially responding infections may necessitate hospitalization and parenteral antimicrobial administration, along with surgical intervention.

Most Pasteurella isolates are susceptible to oral antimicrobials such as amoxicillin, amoxicillin/clavulanic acid, minocycline, fluoroquinolones (ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin), and trimethoprim-sulfamethoxazole. Based on in vitro susceptibility data, several antimicrobials should not be used empirically for P multocida infections, including dicloxacillin, vancomycin, cephalexin, cefaclor, cefadroxil, erythromycin, and clindamycin. Macrolide resistance is usually encountered with erythromycin. Other macrolides, including azithromycin, clarithromycin, and telithromycin (in order of decreasing susceptibility), retain in vitro activity against most Pasteurella strains. Aminoglycosides have poor activity against P multocida.

More-severe infections may require parenteral antibiotics. Intravenous ampicillin-sulbactam, ticarcillin-clavulanate, piperacillin-tazobactam, cefoxitin, and carbapenems (imipenem-cilastatin, meropenem, ertapenem) are excellent empiric options for animal-bite injuries, providing gram-positive, gram-negative, and anaerobic coverage. The new tetracycline-derivative tigecycline also has excellent in vitro activity against P multocida and other pathogens encountered in animal and bite injuries. If P multocida is the only isolated organism, therapy may be changed to intravenous penicillin G. Once clinical improvement is noted, oral penicillin VK is an option. Patients with penicillin allergies can receive minocycline, doxycycline, fluoroquinolones, trimethoprim-sulfamethoxazole, or azithromycin.

The duration of therapy for P multocida infections has not been well established and can be tailored to clinical response. Milder soft-tissue infections usually require 7-10 days of oral therapy. More-severe cases can be treated for 10-14 days. Deep-tissue infections often require 4-6 weeks of therapy, usually intravenously at first.

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Amoxicillin and clavulanate (Augmentin)

Drug combination treats bacteria resistant to beta-lactam antibiotics. For children >3 mo, base dosing protocol on amoxicillin content. Because of different ratios of amoxicillin to clavulanic acid in 250-mg tab (250:125) vs 250-mg chewable tab (250:62.5), do not use 250-mg tab until child weighs >40 kg.

Cefuroxime (Ceftin, Zinacef)

Second-generation cephalosporin that maintains gram-positive activity of first-generation cephalosporins; adds activity against Proteus mirabilis, H influenzae, Escherichia coli, Klebsiella pneumoniae, and Moraxella catarrhalis. Condition of patient, severity of infection, and susceptibility of microorganism determine proper dose and route of administration.

Doxycycline (Vibra-Tabs, Bio-Tab, Doryx, Vibramycin)

Inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria.

Penicillin G (Pfizerpen)

Inhibits biosynthesis of cell wall mucopeptide. Bactericidal against sensitive organisms when adequate concentrations are reached. Most effective during the stage of active multiplication. Inadequate concentrations may produce only bacteriostatic effects. Use penicillin VK for PO or penicillin G for IV.

Ampicillin and sulbactam (Unasyn)

Drug combination of beta-lactamase inhibitor with ampicillin. Covers skin, enteric flora, and anaerobes. Not ideal for nosocomial pathogens.

Ticarcillin and clavulanate (Timentin)

Inhibits biosynthesis of cell wall mucopeptide and is effective during stage of active growth. Antipseudomonal penicillin plus beta-lactamase inhibitor that provides coverage against most gram-positive organisms, most gram-negative organisms, and most anaerobes.

Ciprofloxacin (Cipro)

Mode of action of all quinolones involves inhibition of bacterial DNA synthesis by blocking the enzyme DNA gyrase

Amoxicillin (Trimox, Amoxil)

Interferes with synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria.

Levofloxacin (Levaquin)

For pseudomonal infections and infections due to multidrug-resistant gram-negative organisms.

Ampicillin (Principen, Omnipen)

Bactericidal activity against susceptible organisms. Alternative to amoxicillin when unable to take medication PO.

Piperacillin and tazobactam sodium (Zosyn)

Inhibits biosynthesis of cell wall mucopeptide and is effective during stage of active multiplication.

Ertapenem (Invanz)

Bactericidal activity results from inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin-binding proteins. Stable against hydrolysis by various beta-lactamases including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases. Hydrolyzed by metallo-beta-lactamases.

Imipenem and cilastatin (Primaxin)

For treatment of multi-organism infections in which other agents do not have wide-spectrum coverage or are contraindicated because of potential for toxicity.

Minocycline (Dynacin, Minocin)

Treats infections caused by susceptible gram-negative and gram-positive organisms, in addition to infections caused by susceptible Chlamydia, Rickettsia, and Mycoplasma species.

Cefoxitin (Mefoxin)

Second-generation cephalosporin with activity against some gram-positive cocci, gram-negative rod infections, and anaerobic bacteria. Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins; inhibits final transpeptidation step of peptidoglycan synthesis, resulting in cell wall death.

Infections caused by cephalosporin- or penicillin-resistant gram-negative bacteria may respond to cefoxitin.

Sulfamethoxazole and trimethoprim (Bactrim, Bactrim DS, Septra, Septra DS)

Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid.

Antibacterial activity of TMP-SMZ includes common urinary tract pathogens, except Pseudomonas aeruginosa.

Azithromycin (Zithromax)

Acts by binding to 50S ribosomal subunit of susceptible microorganisms and blocks dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Nucleic acid synthesis is not affected.

Concentrates in phagocytes and fibroblasts as demonstrated by in vitro incubation techniques. In vivo studies suggest that concentration in phagocytes may contribute to drug distribution to inflamed tissues.

Treats mild-to-moderate microbial infections.

Tigecycline (Tygacil)

A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics. Inhibits bacterial protein translation by binding to 30S ribosomal subunit and blocks entry of amino-acyl tRNA molecules in ribosome A site. Complicated intra-abdominal infections caused by C freundii, E cloacae, E coli, K oxytoca, K pneumoniae, E faecalis (vancomycin-susceptible isolates only), S aureus (methicillin-susceptible isolates only), S anginosus group (includes S anginosus, S intermedius, and S constellatus), B fragilis, B thetaiotaomicron, B uniformis, B vulgatus, C perfringens, and P micros.