ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Dec. 2002, p. 3926–3932 Vol. 46, No. 12
0066-4804/02/$04.00⫹0 DOI: 10.1128/AAC.46.12.3926–3932.2002
Copy igh © 2002, Ame ican Socie y o Mic obiology. All Righ s Rese ed.
Ene gy-Dependen Accumula ion o No loxacin and Po in Exp ession
in Clinical Isola es o Klebsiella pneumoniae and Rela ionship
o Ex ended-Spec um ␤-Lac amase P oduc ion
Luis Ma ínez-Ma ínez,
1,2
* Al a o Pascual,
1,2
Ma ía del Ca men Conejo,
1
Isabel Ga cía,
1
P o idencia Joyanes,
1
An onio Dome´nech-Sa´nchez,
3
and Vicen e Ja ie Benedí
3
Depa men o Mic obiology, School o Medicine, Uni e si y o Se ille,
1
and Uni e si y Hospi al V. Maca ena,
2
Se ille, and
Labo a o y o Mic obiology, IMEDEA (CSIC-UIB), Uni e si a de les Illes Balea s, Palma de Mallo ca,
3
Spain
Recei ed 28 Janua y 2002/Re u ned o modi ica ion 18 May 2002/Accep ed 8 Sep embe 2002
The ela ionships be ween po in de iciency, ac i e e lux o luo oquinolones, and ex ended-spec um ␤-lac-
amase (ESBL) p oduc ion we e de e mined o 53 clinical isola es o Klebsiella pneumoniae. Thi y- wo
ESBL-posi i e s ains (including 22 s ains exp essing po ins and 10 s ains lacking po ins) and 21 ESBL-
nega i e s ains we e e alua ed. Ac i e e lux o no loxacin was de ined as a >50% inc ease in he accumu-
la ion o no loxacin in he p esence o ca bonyl cyanide m-chlo ophenylhyd azone (CCCP) in compa ison wi h
he co esponding basal alue in he absence o CCCP. The quinolone esis ance-de e mining egions o bo h
gy A and pa C om 13 s ains, ep esen ing all isola es wi h di e en po in p o iles and wi h o wi hou ac i e
e lux, we e de e mined. Po in loss was signi ican ly mo e common among ESBL-posi i e s ains (10 o 32
[31.2%]) han among ESBL-nega i e s ains (0 o 2 [0%]) (P< 0.01). Ac i e e lux was obse ed in 7 o 10
(70%) s ains lacking po ins and in 4 o 43 (9.3%) s ains p oducing po ins (P< 0.001). The 11 s ains showing
ac i e e lux co esponded o 3 o 21 (14.3%) ESBL-nega i e s ains and 8 o 32 (25.5%) ESBL-posi i e s ains
(P> 0.05). Basal alues o no loxacin accumula ion we e highe in s ains lacking ac i e e lux han in hose
ha had his mechanism (P< 0.05). In he absence o opoisome ase changes, he con ibu ion o ei he po in
loss o ac i e e lux o luo oquinolone esis ance in K. pneumoniae was negligible. I is concluded ha among
K. pneumoniae s ains o clinical o igin, po in loss was obse ed only in hose p oducing ESBL, and ha a
signi ican numbe o po in-de icien s ains also exp essed ac i e e lux o no loxacin. In e ms o luo o-
quinolone esis ance, bo h mechanisms a e signi ican only in he p esence o opoisome ase modi ica ions.
Klebsiella pneumoniae s ains p oducing ex ended-spec um
␤-lac amases (ESBL) a e mo e equen ly esis an o luo o-
quinolones han K. pneumoniae s ains lacking hese enzymes
(22). ESBL-p oducing K. pneumoniae s ains in e media e o
esis an o cip o loxacin con ain gy A mu a ions, alone o
combined wi h pa C mu a ions (4, 5, 6, 12, 25). I is also
possible ha he plasmid coding o he ESBL, o an addi ional
plasmid wi hin he same s ain, may con ain a qn -like de e -
minan as desc ibed o o ganisms exp essing plasmid-medi-
a ed AmpC ype enzymes (14). Qn is esponsible o low-le el
esis ance o quinolones and a o s inc eased esis ance o
hese d ugs (14).
An al e na i e explana ion o ␤-lac am– luo oquinolone
co esis ance in ESBL-p oducing K. pneumoniae is a dec ease
in he pe meabili y o he ou e memb ane o bo h classes o
agen s because o po in al e a ions. Non-ESBL-p oducing
s ains usually exp ess he wo majo po ins (OmpK35 and
OmpK36) o he species, while ESBL-p oducing s ains com-
monly exp ess ei he only one o hese (no mally OmpK36) o
no po in (9). Po in loss in ESBL-p oducing K. pneumoniae
causes esis ance o ce oxi in and inc eased esis ance o de-
c eased suscep ibili y o all oxyimino cephalospo ins, zwi e i-
onic cephalospo ins, and ␤-lac am–␤-lac amase combina ions
(1, 11, 13). Loss o hese channels causes a mode a e ( wo- o
ou old) inc ease in he le el o esis ance o luo oquinolones
when modi ica ions o opoisome ase II (alone o combined
wi h changes in opoisome ase IV) a e p esen (5, 12). The
di ec ole o ei he OmpK35 o OmpK36 in he esis ance o
K. pneumoniae s ains o luo oquinolones and o ␤-lac ams
has been demons a ed. Exp ession o ei he po in om a
ec o con aining wild- ype ompK35 o ompK36 in s ains lack-
ing bo h OmpK35 and OmpK36 dec eases he le el o esis-
ance (1, 13; A. Dome´nech-Sa´nchez, S. He na´ndez-Alle´s, L.
Ma ínez-Ma ínez, and V. J. Benedí, Abs . 38 h In e sci.
Con . An imic ob. Agen s Chemo he ., abs . C186, 1998).
In addi ion o dec eased pe meabili y, i is possible ha
ac i e e lux also con ibu es o luo oquinolone esis ance in
K. pneumoniae. A ew clinical isola es o ESBL-p oducing K.
pneumoniae ha ha e po in de iciencies and exp ess ene gy-
dependen e lux o luo oquinolones ha e been desc ibed (5,
12). In Esche ichia coli and Salmonella en e ica se o a Typhi-
mu ium, pumps o e lux o quinolones may also expo ␤-lac-
ams om he cells (19–21). Exp ession o he amA locus om
K. pneumoniae in E. coli causes esis ance o no loxacin and is
ela ed o bo h inc eased e lux o an imic obial agen s and loss
o he OmpF po in (8). These ac i i ies a e simila o hose
caused by he ansc ip ional ac i a o ma A o E. coli, which
con ibu es o mul iple an imic obial esis ance by inc easing
he ac i i y o he Ac AB-TolC e lux sys em and by dec easing
he pe meabili y o he ou e memb ane due o inc eased an-
* Co esponding au ho . Mailing add ess: Depa men o Mic obi-
ology, School o Medicine, Uni e si y o Se ille, Apdo. 914, 41080
Se ille, Spain. Phone: 34 95 500 8287. Fax: 34 95 437 7413. E-mail:
[email p o ec ed].
3926
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sc ip ion o micF, a ansc ip ional ep esso o he po in gene
ompF (3, 21).
The objec i es o his s udy we e (i) o de e mine he ac i -
i ies o se e al quinolones agains clinical isola es o K. pneu-
moniae wi h cha ac e ized mechanisms o esis ance, (ii) o
es ablish whe he po in loss and ac i e e lux o luo oquino-
lones a e mo e equen ly obse ed in clinical isola es o
K. pneumoniae p oducing ESBL han in hose no p oducing
ESBL, (iii) o e alua e he po en ial ela ionship be ween
po in exp ession and ac i e e lux, and (i ) o analyze he oles
o po in loss and ac i e e lux in he quinolone esis ance le els
o clinical s ains o K. pneumoniae wi h o wi hou mu a ions
in opoisome ase-encoding genes.
MATERIALS AND METHODS
Bac e ial s ains. Fi y- h ee K. pneumoniae s ains o clinical o igin we e
s udied. Th ee g oups o s ains we e selec ed o e alua ion in he p esen s udy:
(i) 10 clonally un ela ed s ains o ESBL-p oducing K. pneumoniae de icien in
bo h OmpK35 and OmpK36 exp ession (see below) isola ed ei he in ou labo-
a o y o in ano he geog aphical zone (po in-de icien s ains), (ii) 22 clonally
un ela ed ESBL-p oducing s ains exp essing po ins in hei ou e memb anes
( hese include 3 s ains clonally ela ed o hose o he p e ious g oup), and (iii)
21 clonally un ela ed non-ESBL-p oducing K. pneumoniae s ains. We lack, and
a e no awa e o , ESBL-nega i e clinical s ains o K. pneumoniae de icien in he
wo majo po ins o he species.
The 32 ESBL-p oducing K. pneumoniae s ains included s ains C1 and C2
(14), s ain CSUB10R (1), and s ains MCQ-102, MCQ-121, and MCQ-122,
kindly p o ided by P. B ad o d (2); s ains GAJ-3, GAJ-18, and GAJ-20, kindly
p o ided by G. A. Jacoby (G. A. Jacoby, P. Han, M. Al a ez, and F. Teno e ,
Abs . 35 h In e sci. Con . An imic ob. Agen s Chemo he ., abs . C40, 1995); six
s ains (LTZ205, LTZ-3273, RL-1, RL-2, RL-5, and RL-5X) om G eece, kindly
p o ided by L. Tzou elekis (24); and 17 s ains om he Uni e si y Hospi al
Vi gen Maca ena, Se ille, Spain, isola ed be ween 1996 and 1998. ESBL-de i-
cien o ganisms we e isola ed be ween 1996 and 1998 a he Uni e si y Hospi al
Vi gen Maca ena, Se ille, Spain (HUS s ains; n⫽19) o he Ciudad Sani a ia
Uni e si a ia de Bell i ge, Ba celona, Spain (CSUB s ains; 2 s ains om he
same pa ien ).
O ganisms we e iden i ied wi h he API 20E sys em (bioMe´ ieux, La Balme
Les G o es, F ance) and main ained in yp ic soy b o h (Di co, De oi , Mich.)
wi h 20% glyce ol (Di co) a ⫺80°C un il use.
Clonal ela ionship o s ains was de e mined by pulsed- ield gel elec opho e-
sis (PFGE) o genomic DNA diges ed wi h SmaI as p e iously desc ibed (1). All
ESBL-de icien s ains om Se ille ep esen ed di e en clones, while he wo
CSUB s ains showed he same PFGE pa e n (da a no shown).
E. coli ATCC 25922 and Pseudomonas ae uginosa ATCC 27853 we e used as
con ol s ains in suscep ibili y es ing assays.
Suscep ibili y es ing. MICs o an imic obial agen s we e de e mined by mi-
c odilu ion acco ding o NCCLS guidelines (17). The ollowing agen s we e
es ed: cip o loxacin (Baye , Le e kusen, Ge many), clina loxacin (Pa ke-Da is,
Ann A bo , Mich.), moxi loxacin (Baye ), nalidixic acid (Sigma, Mad id, Spain),
no loxacin (Sigma), pe loxacin (Rhoˆne-Poulenc, S . An oine, F ance), pipe-
midic acid (Sigma), and o a loxacin (P ize , G o on, Conn.). When a ailable,
clinical ca ego ies we e de e mined acco ding o NCCLS guidelines (18).
ESBL p oduc ion was de ec ed by mic odilu ion, and s ains we e conside ed
ESBL posi i e when cla ulanic acid ( ixed concen a ion, 2 ␮g/ml) caused a
ⱖ8- old educ ion o he MICs o ce azidime, ce o axime, and/o az eonam.
Analysis o OMPs. Bac e ial cells g own o loga i hmic phase we e lysed by
sonica ion. Ou e memb ane p o eins (OMPs) we e ob ained a e ea men o
cell memb anes eco e ed by ul acen i uga ion wi h sodium lau yl-sa cosyna e
(2%; Sigma) and subsequen ul acen i uga ion. OMP p o iles we e de e mined
by sodium dodecyl sul a e-polyac ylamide gel elec opho esis using 11% ac yl-
amide, 0.345% bisac ylamide, and 0.1% sodium dodecyl sul a e in he unning
gel. A e elec opho esis, p o eins we e s ained wi h Coomassie b illian blue
(Sigma) (11).
Accumula ion o no loxacin. Bac e ia g own in nu ien b o h we e suspended
in phospha e-bu e ed saline (PBS) (ca. 0.650 mg o bac e ia [d y weigh ]/ml),
incuba ed wi h 10 ␮go no loxacin/ml a 37°C o 30 min, and cen i uged
h ough a silicone oil ba ie (␳, 1.029 g/cm
3
) o elimina e ex acellula quino-
lone. Fo he 11 s ains o 53 e alua ed ha did no a e se he silicon oil laye ,
ex acellula no loxacin was elimina ed by a wash wi h 1 ml o PBS (a 12,800 ⫻
gand 4°C o 1 min) (16). The cell pelle ob ained by ei he me hod was placed
in 2 ml o 0.1 M glycine-HCl bu e (pH 3.0), o exed, and cen i uged o 5 min
a 12,800 ⫻g. The amoun o no loxacin in he supe na an (basal accumula-
ion) was measu ed spec opho ome ically (12). The e ec o he ene gy inhib-
i o ca bonyl cyanide m-chlo ophenylhyd azone (CCCP) (0.1 mM) was e alu-
a ed in pa allel by addi ion o CCCP o bac e ial suspensions 10 min a e he
addi ion o no loxacin and eincuba ion o he cells o 20 min. Expe imen s
we e done in duplica e on h ee di e en days. An o ganism was conside ed o
exp ess ene gy-dependen accumula ion o no loxacin when CCCP enhanced
basal accumula ion by a leas 50%, a h eshold which co esponds o wice he
s anda d de ia ion o he mean basal accumula ion o he s ains es ed.
Analysis o mu a ions in opoisome ase-encoding genes. Thi een s ains, ep-
esen a i e o all possible combina ions among le el o suscep ibili y, po in
p o ile, and exp ession o ac i e e lux, we e es ed. Al e a ions in he Gy A
subuni o DNA gy ase and he Pa C subuni o opoisome ase IV we e de e -
mined by sequencing he quinolone esis ance-de e mining egions (QRDRs) o
he g yA and pa C genes by use o p ime s p e iously desc ibed by Deguchi e al.
(4).
S a is ical analyses. Rela ionships be ween ESBL p oduc ion, loss o po ins,
and exp ession o ac i e e lux we e de e mined by he chi-squa e es and we e
conside ed s a is ically signi ican a a Po ⬍0.05. No loxacin accumula ion
alues we e exp essed as means ⫾s anda d de ia ions, and di e ences among
g oups we e compa ed by analysis o a iance, which was used o assess s a is ical
signi icance a a Po ⬍0.05.
RESULTS
Suscep ibili y es ing. Twen y- wo ou o he 53 s ains s ud-
ied we e suscep ible o nalidixic acid (NAL-S), and 31 we e
esis an o nalidixic acid (NAL-R; MICs, in all cases, we e
ⱖ64 ␮g/ml). NAL-S s ains included 13 s ains p oducing
ESBL and 9 s ains no p oducing ESBL. NAL-R s ains in-
cluded 19 and 12 o ganisms p oducing and no p oducing
ESBL, espec i ely (Fig. 1).
All NAL-S s ains we e inhibi ed by pipemidic acid a 8 ␮g/
ml, and all NAL-R s ains we e inhibi ed by ⱖ16 ␮g o pipe-
midic acid/ml, excep in one case (MIC o pipemidic acid,
4␮g/ml). All NAL-S s ains we e inhibi ed by ⱕ0.06 ␮go
cip o loxacin o clina loxacin/ml. MICs o bo h no loxacin and
pe loxacin o NAL-S s ains we e ⱕ0.06 ␮g/ml (16 s ains)
and 0.125 ␮g/ml (6 s ains), while MICs o o a loxacin and
moxi loxacin o NAL-S s ains we e ⱕ0.06 ␮g/ml (20 s ains),
0.125 ␮g/ml (1 s ain), and 0.25 ␮g/ml (1 s ain). The MIC
90
s
(MICs a which 90% o isola es we e inhibi ed) o no loxacin
and pe loxacin o NAL-S s ains we e 0.125 ␮g/ml, and
MIC
90
s o he emaining ou luo oquinolones o his g oup
o s ains we e ⱕ0.06 ␮g/ml.
Dis ibu ions o MICs o luo oquinolones agains NAL-R
s ains a e shown in Table 1. I can be obse ed ha MICs o
no loxacin and pe loxacin o NAL-R s ains we e always
ⱖ0.5 ␮g/ml, and hose o cip o loxacin we e always ⱖ0.125 ␮g/
ml. On he o he hand, MICs o clina loxacin we e ⱕ2␮g/ml
o all 32 NAL-R s ains. As shown in Table 1, MIC
90
so all
luo oquinolones o which he NCCLS es ablishes b eak-
poin s all wi hin he esis an ca ego y.
Analysis o OMPs. All 53 s ains es ed p oduced an OmpA-
like p o ein o abou 32 kDa. All 21 ESBL-nega i e s ains
(ei he NAL-S o NAL-R) p oduced OMPs in he ange o 35
o 37 kDa, compa ible wi h he hypo hesis ha hey a e po ins.
Among ESBL-p oducing s ains, po in exp ession was ob-
se ed in 22 s ains (68.8%), and no in he emaining 10
s ains (31.2%) (Fig. 1). These da a indica e ha po in loss is
signi ican ly (P⬍0.01) mo e equen among ESBL-p oducing
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s ains. Rep esen a i e esul s o OMP analysis a e p esen ed
in Fig. 2.
Accumula ion o no loxacin. In a se o independen expe -
imen s in which he absolu e alue o no loxacin accumula ion
was de e mined o 10 s ains ( ep esen a i e o he di e en
accumula ion models obse ed) by bo h he silicon oil me hod
and he PBS washing me hod, lowe absolu e alues we e ob-
ained wi h he la e me hod, bu he pe cen ages o inc ease
in no loxacin accumula ion caused by CCCP de e mined by
he wo me hods we e no signi ican ly di e en (da a no
shown). Fo his eason we ha e conside ed he pe cen age o
inc ease in no loxacin accumula ion caused by CCCP o be an
indica o o e lux, ega dless o whe he his was de e mined
by he silicon oil me hod (42 s ains) o he PBS washing
me hod (11 s ains).
Only o 11 o 53 s ains did CCCP enhance he concen a-
ion o accumula ed no loxacin mo e han 50% o e he co -
esponding basal accumula ion alue. Ac i e e lux was sig-
ni ican ly mo e equen (P⬍0.001) among po in-de icien
s ains (7 o 10 [70.0%]) han among po in-p oducing s ains
(4 o 43 [9.3%]). A highe pe cen age o s ains showing ac i e
e lux o no loxacin was no ed among ESBL-posi i e s ains
(8 o 32 [25.0%]) han among ESBL-nega i e s ains (3 o 21
[14.3%]), bu his di e ence was no s a is ically signi ican
(P⬎0.05). Fo se en s ains he inc ease in no loxacin accu-
mula ion due o CCCP was 210 o 275%, and o ou s ains
he inc ease was 56 o 75%. Addi ion o CCCP caused a ⬍50%
inc ease in he accumula ion o no loxacin in 19 s ains: 1 o
20% in 6 s ains, 11 o 20% in 8 s ains, and 31 o 49% in 5
s ains. In e es ingly, CCCP caused dec eased no loxacin ac-
cumula ion in he emaining 23 s ains: he pe cen ages o
dec ease we e 62% (n⫽1), 36% (n⫽1), 20 o 26% (n⫽3),
10 o 19% (n⫽10), and 1 o 9% (n⫽8).
Among he 42 s ains o which accumula ion o no loxacin
was assayed by he silicon oil me hod, basal accumula ion al-
FIG. 1. Rela ionship be ween suscep ibili y o nalidixic acid, ESBL-p oduc ion, po in exp ession, and ac i e e lux o no loxacin (AEN) in 53
clinical isola es o K. pneumoniae.
TABLE 1. Dis ibu ion o MICs, MIC
50
s, and MIC
90
so six
luo oquinolones agains 31 NAL-R s ains o K. pneumoniae
D ug
No. o s ains inhibi ed a he
ollowing MIC (␮g/ml): MIC
50
(␮g/ml)
MIC
90
(␮g/ml)
⬍0.06 0.125 0.25 0.5 12481632ⱖ64
Cip o loxacin 1 1 5 1564 4 2 2 4 32
Clina loxacin 10 2 4 9 4 2 0.25 1
Moxi loxacin 4 3 6682 1 1 2 8
No loxacin 4 4225 8 2 4 8 64
Pe loxacin 4 2336 8 2 3 8 32
T o a loxacin 2 3 7484 2 1 2 8
3928 MARTI
´NEZ-MARTI
´NEZ ET AL. ANTIMICROB.AGENTS CHEMOTHER.
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ues we e highe in s ains lacking ac i e e lux o no loxacin
han in s ains showing ac i e e lux o no loxacin (P⬍0.05).
No such compa ison was a emp ed o s ains assayed by he
cen i uga ion me hod because none o hem exp essed ac i e
e lux as p e iously de ined.
Accumula ion o no loxacin in s ains lacking ac i e e lux
a e cells we e ea ed wi h CCCP anged om 219 o 589
ng/mg o bac e ia (d y weigh ), while he co esponding ange
in ac i e-e lux-posi i e s ains was 273 o 505 ng/mg o bac e ia
(d y weigh ) (P⬎0.05).
No loxacin accumula ion in 11 s ains wi h ac i e e lux o
no loxacin is p esen ed acco ding o po in exp ession pa e n
in Table 2. No loxacin accumula ion in h ee s ains de icien
in po in exp ession and lacking ac i e e lux o no loxacin
(Table 3) was no signi ican ly di e en (P⬎0.05) om ha
obse ed o s ains ha do no exp ess ac i e e lux bu ex-
p ess po ins.
Ta ge modi ica ions. As shown in Table 4, he QRDRs o
bo h Gy A and Pa C o he ou NAL-S s ains e alua ed we e
iden ical o he sequences epo ed o K. pneumoniae s ain
ATCC 13833: codons 83 and 87 o gy A coded o Se and Asp,
espec i ely, while codons 78, 80, and 84 o pa C coded o Gly,
Se , and Glu, espec i ely. The same esul s we e ob ained o
wo s ains wi h low-le el esis ance o nalidixic acid: MICs o
nalidixic acid we e 64 and 256 ␮g/ml o s ains HUS 33-99 and
HUS 298-98, espec i ely. All s ains wi h high-le el esis ance
o nalidixic acid (MIC ⱖ1,024 ␮g/ml) had mu a ions a gy A,
ei he alone o combined wi h mu a ions in pa C. No cases o
mu a ion in pa C we e obse ed in he absence o mu a ions in
gy A. Mu a ions in codon 83 o gy A caused a change om Se
o ei he Phe o Ty , while mu a ions in codon 87 caused a
change om Asp o ei he Ty o Asn. Mu a ions in pa C
caused changes a posi ion 78 (Gly o Cys), 80 (Se o A g), o
84 (Glu o Gly). The e we e no ob ious ela ionships be ween
he ypes o mu a ions in opoisome ase genes and he le el o
esis ance o luo oquinolones.
No loxacin accumula ion and po in exp ession in pai s o
clonally ela ed s ains (p esen ing he same PFGE pa e n)
a e p esen ed in Table 5.
DISCUSSION
Resis ance o luo oquinolones in K. pneumoniae is mo e
commonly ound among ESBL-p oducing s ains han among
non-ESBL p oduce s (22). In his s udy he possible associa-
ions be ween al e ed pe meabili y, ac i e e lux o no loxacin,
and ESBL p oduc ion in clinical isola es o K. pneumoniae
we e e alua ed. Addi ionally, opoisome ase changes we e also
de e mined o some s ains in o de o e alua e in mo e de ail
he ele ance o he abo e-men ioned mechanisms. The pos-
FIG. 2. OMP p o iles o ESBL-p oducing (A) and non-ESBL-p oducing (B) K. pneumoniae s ains. (A) Lane 2, s ain HUS 76-96; lane 3, s ain
HUS 56-96; lane 4, s ain HUS 33-96; lane 5, s ain HUS 71-96; lane 6, s ain HUS 20-97; lane 7, s ain HUS 91-96. (B) Lane 9, s ain RL-1; lane
10, s ain RL-2; lane 11, s ain RL-5X; lane 12, s ain RL-5b; lane 13, s ain GAJ-3; lane 14, s ain HUS 8-98. Lanes 1 and 8, molecula size ma ke s
(in kilodal ons). Symbols: open ci cle, LamB-like p o ein; a owhead, po in; solid ci cle, OmpA-like p o ein.
TABLE 2. Accumula ion o no loxacin wi hou and wi h 100 ␮M
CCCP in 11 s ains o K. pneumoniae showing ene gy-dependen
accumula ion o no loxacin and exp essing po ins o no
S ain
Accumula ion o no loxacin
a
(ng/mg o bac e ia [d y w ])
Basal
b
Wi h CCCP
c
Po in de icien
RL-1 103 ⫾25 273 ⫾53
RL-5b 128 ⫾25 352 ⫾34
LTZ-3273 253 ⫾41 437 ⫾59
C1 247 ⫾61 505 ⫾55
C2 220 ⫾35 410 ⫾81
CSUB10R 188 ⫾19 429 ⫾50
MCQ-122 269 ⫾39 430 ⫾32
Po in exp essing
CSUB-61A 298 ⫾22 445 ⫾13
HUS 71-96 245 ⫾59 436 ⫾73
HUS 298-98 182 ⫾80 417 ⫾56
GAJ-18 161 ⫾63 331 ⫾32
a
Da a a e means ⫾s anda d de ia ions om h ee independen duplica e
expe imen s.
b
Tes ed in he absence o CCCP.
c
Tes ed in he p esence o 100 ␮M CCCP.
TABLE 3. Accumula ion o no loxacin wi hou and wi h CCCP in
h ee s ains o K. pneumoniae de icien in po ins and lacking
ene gy-dependen accumula ion o no loxacin
S ain
Accumula ion o no loxacin
a
(ng/mg o bac e ia [d y w ])
Basal Wi h 100 mM CCCP
RL-2 441 ⫾80 387 ⫾90
GAJ-3 386 ⫾33 386 ⫾33
MCQ-102 454 ⫾119 372 ⫾88
a
Da a a e exp essed as means ⫾s anda d de ia ions om h ee independen
duplica e expe imen s.
VOL. 46, 2002 EFFLUX, PORINS, AND ESBL IN K. PNEUMONIAE 3929
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sible p o ec ion o DNA gy ase by a Qn -like p o ein (14, 23)
has been uled ou in a pa allel s udy (da a no shown). Figu e
1 shows he dis ibu ion o he 53 s ains es ed in his s udy
acco ding o quinolone suscep ibili y, ESBL p oduc ion, po in
exp ession, and ac i e e lux exp ession.
Ou esul s indica e ha in clinical isola es o K. pneumo-
niae, po in loss is mo e equen among ESBL-posi i e han
among ESBL-nega i e s ains and ha in his o ganism ac i e
e lux o no loxacin occu s mo e commonly among po in-de-
icien s ains. Al hough he pe cen age o s ains showing ac-
i e e lux was highe among ESBL-posi i e han among
ESBL-nega i e isola es, his end was no s a is ically signi i-
can . I is possible ha he me hod we used o de ec ing ac i e
e lux is no sensi i e enough and/o ha he b eakpoin o
de ining i (a 50% inc ease in accumula ion in he p esence o
CCCP) is oo s ic (no e ha o i e s ains, CCCP enhanced
accumula ion by 31 o 49%). I would be in e es ing o e alua e
a la ge numbe o s ains, o measu e accumula ion o o he
subs a es, o o use o he me hodological app oaches (an as-
say wi h adiolabeled luo oquinolone, o immunological de-
TABLE 4. Mu a ions a he QRDRs o gy A and pa C in 13 clinical s ains o K. pneumoniae
S ain
P esence o absence
a
o : MIC Mu a ion
d
ESBL Po in E lux NAL
b
CIP
c
Gy A Pa C
Se 83 Asp87 Gly78 Se 80 Glu84
CSUB-61A ⫺⫹⫺ 0.5 0.004 —————
CSUB-61B ⫺⫹⫹ 0.5 0.008 —————
HUS 76-96 ⫺⫹⫺ 2ⱕ0.06 —————
LTZ-3273 ⫹⫺⫹ 16 ⱕ0.06 —————
HUS 33-96 ⫺⫹⫺ 64 0.125 —————
HUS 298-98 ⫺⫹⫹ 256 0.5 —————
C2 ⫹⫺⫹⬎1,024 0.5 Phe ————
MCQ-102 ⫹
e
⫺⫺⬎1,024 0.5 Ty ————
C1 ⫹⫺⫹⬎1,024 4 Ty ———
HUS 22-97 ⫹⫹⫺⬎1,024 4 Phe Ty ——Gly
HUS 20-97 ⫺⫹⫺⬎1,024 8 Phe Ty ——Gly
MCQ-121 ⫹
e
⫹⫺⬎1,024 64 Phe Asn Cys A g —
MCQ-122 ⫹
e
⫺⫹⬎1,024 128 Phe Asn Cys A g —
a
⫹, p esence; ⫺, absence.
b
NAL, nalidixic acid.
c
CIP, cip o loxacin.
d
—, no change wi h espec o wild- ype sequence.
e
AmpC ype ␤-lac amase p oduce .
TABLE 5. Accumula ion o no loxacin wi hou and wi h CCCP in i e pai s o clonally ela ed K. pneumoniae s ains
wi h di e en mechanisms o esis ance o luo oquinolones
S ain PFGE
pa e n
P esence o
absence
a
o :
No loxacin accumu-
la ions
b
(ng/mg o
bac e ia [d y w ])
Mu a ion(s)
c
MIC (␮g/ml)
ESBL Po in Basal Wi h CCCP Gy A Pa C NAL
d
CIP
e
NOR
CLIN
g
CUSB-61A 1 ⫺⫹570 ⫾27 219 ⫾78 w w 0.5 0.004 0.03 ⱕ0.06
CUSB-61B 1 ⫺⫹298 ⫾22 445 ⫾13 w w 0.5 0.008 0.06 ⱕ0.06
RL-5X 2 ⫹⫹470 ⫾25 409 ⫾79 w w 8 ⱕ0.06 0.25 ⱕ0.06
RL-2 2 ⫹⫺441 ⫾80 387 ⫾90 w w 4 ⱕ0.06 0.5 ⱕ0.06
LB2
h
3⫹⫹286 ⫾24 385 ⫾65 Se 83Ty w ⬎1,024 0.5 2 ⱕ0.06
LB4
h
3⫹⫺116 ⫾21 263 ⫾38 Se 83Ty w ⬎1,024 1 4 ⱕ0.06
CSUB10S 4 ⫹⫹313 ⫾6 ND Se 83Phe w ⬎1,024 0.5 1 ⱕ0.06
CSUB10R 4 ⫹⫺188 ⫾19 429 ⫾50 Se 83Phe w ⬎1,024 4 8 ⱕ0.06
MCQ-121 5 ⫹
i
⫹434 ⫾53 405 ⫾79 Se 83Phe, Asp87Asn Gly78Cys, Se 80A g ⬎1,024 64 256 1
MCQ-122 5 ⫹
i
⫺298 ⫾22 445 ⫾13 Se 83Phe, Asp87Asn Gly78Cys, Se 80A g ⬎1,024 128 ⬎256 2
a
⫹, p esence; ⫺, absence.
b
Basal, wi hou CCCP; wi h CCCP, in he p esence o 100 ␮M CCCP. Da a a e means ⫾s anda d de ia ions om h ee independen duplica e expe imen s. ND,
no de e mined.
c
w , wild ype.
d
NAL, nalidixic acid.
e
CIP, cip o loxacin.
NOR, no loxacin.
g
CLIN, clina loxacin.
h
Da a o LB2 and LB4 ha e been epo ed p e iously (11) and a e included o compa ison.
i
Also p oducing he AmpC ype ACT-1 ␤-lac amase.
3930 MARTI
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ec ion o he e lux sys em p o eins) o con i m ha ac i e
e lux is no ela ed o ESBL p oduc ion.
The da a in Table 1 indica e he exis ence o c oss- esis ance
o nalidixic acid and luo oquinolones in K. pneumoniae, al-
hough he e ec s o he mechanisms o esis ance a e di e en
o di e en compounds. Clina loxacin was, in e ms o
MIC
90
s, he mos ac i e luo oquinolone o hose es ed he e,
ollowed by moxi loxacin, o a loxacin, cip o loxacin, pe loxa-
cin, and no loxacin.
K. pneumoniae ATCC 13833 and many o he quinolone-
suscep ible clinical isola es con ain se ine ins ead o h eonine
a posi ion 83, as p e iously epo ed o K. pneumonaie M5a1
(7). A ecen epo has shown ha Klebsiella oxy oca 13182
con ains h eonine (25). Ou da a wi h ou NAL-S s ains also
indica e ha se ine is no mally ound a posi ion 83 o Gy A in
K. pneumoniae, while Phe o Ty is p esen in K. pneumoniae
s ains wi h high-le el esis ance o NAL. Changes in Gy A
Asp87 o Ty o o Asp ha e been obse ed in ou NAL-R
s ains. These ha e also been he mos equen subs i u ions
ound in o he s udies (4, 5, 6, 25). Mu a ions in pa C (coding
o Se 80A g and Glu84Gly) we e obse ed in ou ou o i e
NAL-R and cip o loxacin- esis an s ains. In he wo clonally
ela ed s ains MCQ-121 and MCQ-122, a mu a ion in pa C
ha is esponsible o a Gly78Cys change and ha has no been
pe iously epo ed o K. pneumoniae was no ed. The ele-
ance o his change awai s u he s udy.
This s udy and p e ious s udies (4, 5, 6, 12) indica e ha he
le els o esis ance o nalidixic acid and luo oquinolones in
clinical isola es o K. pneumoniae a e no comple ely explained
by changes in he QRDRs o gy A and pa C (Table 4; compa e
s ain HUS76-96 wi h s ain LTZ-3273 and s ain MCQ-102
wi h s ain C1).
S ains CSUB10R and LB4 a e de icien in po ins, con ain a
Gy A change, and in addi ion exhibi ene gy-dependen accu-
mula ion o luo oquinolones (11, 12). On he o he hand, he
clonally ela ed s ains CSUB10S and LB2 exp ess OmpK36
and do no show ene gy-dependen accumula ion o luo o-
quinolones. This sugges s a link be ween he loss o he wo
po ins and exp ession o ene gy-dependen accumula ion o
luo oquinolones in clinical isola es o K. pneumoniae. To e al-
ua e his hypo hesis, no loxacin accumula ion was de e mined
in a collec ion o un ela ed po in-de icien s ains and, o
compa ison, in a ep esen a i e numbe o po in-exp essing
s ains (ei he p oducing o no p oducing ESBL).
We measu ed no loxacin accumula ion by using a luo o-
me ic assay, elimina ing ex acellula luo oquinolone by cen-
i uga ion h ough a silicon oil ba ie o by washing cells wi h
PBS. In his s udy, lowe no loxacin accumula ion was ob-
ained when he PBS washing me hod ins ead o he silicon oil
me hod was used, in ag eemen wi h p e ious epo s (16;
unpublished da a). Al hough he ac ual easons o hese di -
e ences ha e no ye been sa is ac o ily explained, he ap-
p oach we used o de ining ac i e e lux as a a io o accumu-
la ion in he p esence o CCCP o accumula ion in he absence
o CCCP allows compa ison o he esul s ob ained by hese
wo me hods.
In some o he s ains we s udied, CCCP caused dec eased
( a he han inc eased) accumula ion o no loxacin. I can be
hypo hesized ha , in hese s ains, CCCP induces he exp es-
sion o one o mo e e lux pumps also in ol ed in luo oquin-
olone elimina ion, bu u he wo k is needed o cla i y hese
esul s.
Se en o he 11 s ains exp essing ac i e e lux o no loxacin
we e po in de icien , while among he 10 po in-de icien s ains
e alua ed, 7 exp essed ene gy-dependen accumula ion o luo-
oquinolones (Fig. 1).
Accumula ions (ei he in he absence o in he p esence o
CCCP) in he se en s ains exp essing e lux o luo oquino-
lones and lacking po ins we e no s a is ically di e en (P⬍
0.05) om hose in ou s ains exp essing ene gy-dependen
accumula ion o luo oquinolones and p oducing po ins (Table
2), while accumula ions in s ains lacking ac i e e lux we e no
di e en (P⬎0.05) o s ains exp essing o lacking po ins
(Table 3). This sugges s ha when he majo po ins o K.
pneumoniae a e los , no loxacin (and pe haps o he luo o-
quinolones) may s ill accumula e in he cell by o he means
and ha dec eased accumula ion depends mo e on elimina ion
by ac i e e lux han on dec eased pe meabili y by po in loss.
Fu he s udies a e equi ed o deduce he independen oles
o ac i e e lux and o loss o po ins in he inal amoun o
no loxacin accumula ed in s ains exp essing bo h mecha-
nisms.
In a p e ious s udy i was shown ha when o he mecha-
nisms o esis ance a e absen , loss o po ins in K. pneumoniae
C3 does no con ibu e signi ican ly o quinolone esis ance
(10). In his s udy we ha e obse ed, o s ains CSUB-61A and
CSUB-61B, ha exp ession o ene gy-dependen accumula ion
o luo oquinolones alone does no signi ican ly inc ease he
le el o esis ance (Table 5). When bo h po in loss and ac i e
e lux a e p esen in he same o ganism ha has a opoisom-
e ase change(s), a mode a e inc ease in he le el o luo o-
quinolone esis ance is obse ed. This has been desc ibed p e-
iously o s ains LB2 and LB4 (11) and o s ains CSUB10S
and CSUB10R (1) and has been obse ed he e o s ains
MCQ-121 and MCQ-122 (wi h double mu a ions in bo h gy A
and pa C). This indica es ha mul iple a ge mu a ions a e
much mo e impo an han nonspeci ic mechanisms o quin-
olone esis ance, bu he la e may be a c i ical s ep a o ing
he eme gence o mu an s wi h al e ed a ge s.
K. pneumoniae may exp ess a basal e lux o luo oquinolo-
nes, as al eady obse ed o E. coli and o he en e obac e ia.
The wide ange o no loxacin accumula ion in he s ains we
s udied may e lec a ia ion in unde ined ac o s ha de e -
mine binding o he d ug o he cell bu may also ep esen
a iable exp ession o ac i e e lux in di e en o ganisms. In E.
coli, Ac AB-TolC is he mo e clinically ele an e lux sys em,
since i is in ol ed in he elimina ion o luo oquinolones,
␤-lac ams, and o he an imic obial agen s (15, 20). P elimina y
esul s (da a no shown) indica e ha K. pneumoniae con ains
an Ac AB homologue. New s udies a e in p og ess o e alua e
he impo ance o Ac AB-TolC and o he e lux sys ems in he
s ains included in his epo .
ACKNOWLEDGMENTS
We hank C. A danuy, P. B ad o d, G. A. Jacoby, and L. Tzou ele-
kis o supplying bac e ial s ains.
This wo k was suppo ed by he Fondo de In es igacio´n Sani a ia,
Minis e io de Sanidad y Consumo o Spain, g an s 00/0242 ( o
L.M.-M.) and 01/0034 ( o V.J.B.). A.D.-S. was suppo ed by a p edoc-
o al ellowship om he Minis e io de Educacio´n y Cul u a o he
Spanish go e nmen .
VOL. 46, 2002 EFFLUX, PORINS, AND ESBL IN K. PNEUMONIAE 3931
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3932 MARTI
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